CN109818569B - Parallel type turn-off system for photovoltaic module and method for restarting after turn-off - Google Patents

Abstract

The invention mainly relates to a parallel connection type turn-off system for a photovoltaic assembly and a method for restarting after turn-off. The photovoltaic modules are provided with a turn-off device, a plurality of photovoltaic modules are connected in series to form a battery string, and the turn-off device is used for turning off the corresponding photovoltaic module to remove the photovoltaic module from the battery string or restoring the corresponding photovoltaic module from a turn-off state to a series connection state of connecting the photovoltaic module into the battery string. And when the shutdown control module receives the shutdown command, the shutdown control module stops transmitting the periodic excitation pulse source to each shutdown device so as to inform the shutdown devices to execute shutdown operation. And the turn-off control module transmits periodic excitation pulse sources to the turn-off devices again when receiving the starting command so as to inform the turn-off devices to execute turn-on operation, so that the photovoltaic assemblies corresponding to the turn-off devices are recovered to a serial connection state from a turn-off state.

Description

Parallel type turn-off system for photovoltaic module and method for restarting after turn-off

Technical Field

The invention mainly relates to the technical field of solar power generation, in particular to a system capable of quickly switching off a series-connected multi-stage photovoltaic module.

Background

The photovoltaic power generation system needs to meet the safety standard in a power electronic system, and corresponding laws and regulations are provided for governments or related institutions of various countries. Based on safety code considerations, the american fire protection association modifies national electrical codes, requiring that in residential photovoltaic power generation systems: when an emergency occurs, the voltage of the direct current end is limited not to exceed eighty volts to the maximum extent after the alternating current grid-connected port of the photovoltaic power generation system is disconnected. Italian safety regulations caution: firefighters are absolutely not allowed to perform a fire extinguishing operation with a building charged with voltage. Germany also has first implemented fire safety standards and also stipulates in plain text: an additional direct current cut-off device needs to be added between an inverter and a component in the photovoltaic power generation system. From these laws and regulations, the first remarks to safety factors can be concluded: even if the photovoltaic modules have unexpected fire, the rescue is allowed to carry out fire-fighting rescue only after all the photovoltaic modules are burnt out and the personal safety is no longer endangered.

The popularity of the photovoltaic power generation system is higher in Europe and America, so that the matched rule and rule of safe power utilization also extend to the field of photovoltaic power generation in time. Taking the safety code NEC2017 in the united states as an example, the photovoltaic power generation system is required to have a rapid turn-off function, and the voltage between the conductors inside the photovoltaic array and between the conductors and the ground must not exceed about eighty volts at most after turn-off. The positive measures of the photovoltaic power station in dealing with the safety regulations are as follows: in order to realize quick switching-off, a switching-off device which plays a role in switching-off is specially installed at the output end of a photovoltaic module, a command transmitting device is installed on a battery pack string which provides direct current or a direct current bus, and the command transmitting device is mainly powered by an alternating current power grid. For example, in case of fire, it is necessary to turn off the photovoltaic module quickly, and the command transmitting device is used to instruct the turn-off device to turn off. The countermeasure of shutting down the photovoltaic module can prevent further deterioration of negative events such as fire and the like, and improve reliability and safety.

Disclosure of Invention

In one non-limiting alternative embodiment of the present invention, a parallel shutdown system for photovoltaic modules is disclosed and generally comprises:

at least one turn-off control module;

the photovoltaic module comprises a plurality of turn-off devices and a plurality of photovoltaic modules, wherein each photovoltaic module is provided with one turn-off device;

a plurality of photovoltaic modules are connected in series to form a battery pack string;

each turn-off device is used for turning off the photovoltaic component corresponding to the turn-off device to remove the photovoltaic component from the battery string or restoring the photovoltaic component corresponding to the turn-off device from a turn-off state to a series connection state of connecting the photovoltaic components into the battery string;

when the turn-off control module receives a turn-off command, the turn-off control module stops transmitting a periodic excitation pulse source to each turn-off device to inform the plurality of turn-off devices to execute turn-off operation so as to turn off the corresponding photovoltaic assemblies; or

When receiving the starting command, the turn-off control module transmits periodic excitation pulse sources to the turn-off devices again to inform the turn-off devices to execute turn-on operation, so that the photovoltaic assemblies corresponding to the turn-off devices are recovered to a serial connection state from a turn-off state.

The above parallel shutdown system for photovoltaic module, wherein:

each turn-off device comprises a group of input ends respectively connected to the positive electrode and the negative electrode of the photovoltaic assembly and a group of output ends connected with other turn-off devices in series, and a bypass diode is arranged between the group of output ends of each turn-off device;

when the photovoltaic component is turned off, the bypass diode provides a conduction path between a group of output ends of the turn-off device corresponding to the turned-off photovoltaic component.

The above parallel shutdown system for photovoltaic module, wherein:

each turn-off device comprises a main switch for switching off or on between an input and an output thereof, the main switch having a first terminal, a second terminal and a control terminal;

each turn-off device comprises a first coupling transformer coupled to the output end of the turn-off device through a power line, and a primary winding of the first coupling transformer and a first terminal of the main switch are connected to one of a group of output ends;

the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on the power line;

the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode;

when the potential of the energy storage capacitor reaches the conducting threshold voltage of the main switch, the main switch is switched on, otherwise, the main switch is switched off.

The above parallel shutdown system for photovoltaic module, wherein:

the main switch is a power MOSFET and the first, second and control terminals are a source, a drain and a gate, respectively; or

The main switch is an IGBT and the first, second and control terminals are an emitter, a collector and a gate, respectively.

The above parallel shutdown system for photovoltaic module, wherein:

and a parallel resistor connected in parallel with the energy storage capacitor is also arranged between the control terminal and the first terminal of the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are further arranged between the control terminal and the first terminal of the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to the control terminal of the main switch through the steering diode;

the dotted terminal is connected to the anode of the steering diode and the control terminal of the main switch is connected to the cathode of the steering diode.

The above parallel shutdown system for photovoltaic module, wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to a first node through a first capacitor;

a first diode is connected between the synonym end of the secondary winding of the first coupling transformer and the first node;

the anode of the first diode is connected to the synonym terminal of the secondary winding of the first coupling transformer, and the cathode is connected to the first node;

the first node is coupled to the anode of the steering diode and the control terminal of the main switch is coupled to the cathode of the steering diode.

The above parallel shutdown system for photovoltaic module, wherein:

the stage that the shutdown device does not execute shutdown operation and sets the photovoltaic module corresponding to the shutdown device to be connected into the battery string, and an excitation pulse source sent by the shutdown control module has a first logic state;

when receiving a turn-off command, the turn-off control module firstly inverts an excitation pulse source transmitted to the turn-off device from a first logic state to a second logic state with opposite polarity so as to inform the turn-off device to immediately short-circuit the control terminal and the first terminal of the main switch so as to rapidly turn off the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

the winding direction of one auxiliary winding of the first coupling transformer is opposite to that of the secondary winding;

the different name end of the auxiliary winding of the first coupling transformer is connected to the base electrode and the same name end of an NPN bipolar transistor, and the emitter electrode of the NPN bipolar transistor is connected to the first terminal of the main switch;

the collector of the NPN bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the NPN bipolar transistor to be conducted when inducing the excitation pulse source of the second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

the winding direction of one auxiliary winding of the first coupling transformer is the same as that of the secondary winding;

the homonymous terminal of the auxiliary winding of the first coupling transformer is connected to the base electrode and the synonym terminal of a PNP bipolar transistor and the emitter electrode of the PNP bipolar transistor through a reversely connected second diode, and the emitter electrode of the PNP bipolar transistor is connected to the first terminal of the main switch;

the collector of the PNP bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the PNP bipolar transistor to be conducted when inducing an excitation pulse source of a second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch;

the anode of the second diode is connected to the base of the PNP bipolar transistor and the cathode is connected to the dotted terminal of the auxiliary winding.

The above parallel shutdown system for photovoltaic module, wherein:

the turn-off device comprises a parallel capacitance connected between the first and second terminals of the main switch;

after the turn-off device performs the turn-off operation and closes the main switch, a parallel capacitor connected in parallel with the main switch provides a conduction path through which the excitation pulse source propagates bypassing the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

the turn-off device comprises a normally-open parallel switch connected between a first terminal and a second terminal of the main switch, a control terminal of the normally-open parallel switch being connected to a control terminal of the main switch;

after the turn-off device executes turn-off operation and closes the main switch, the normally-open parallel switch entering the conducting state provides a conducting path for the excitation pulse source to propagate by bypassing the main switch; and

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch to switch on the main switch, the potential of the energy storage capacitor also controls the normally-open parallel switch to be switched off.

The above parallel shutdown system for photovoltaic module, wherein:

and replacing the primary winding and the secondary winding of the first coupling transformer by the primary winding and the secondary winding of one transformer.

In a non-limiting alternative embodiment of the invention, a method for restarting a parallel shutdown system for photovoltaic modules based on the foregoing after shutdown is disclosed, wherein:

each turn-off device comprises a main switch for switching off or on between an input and an output thereof, the main switch having a first terminal, a second terminal and a control terminal;

each turn-off device further comprises a first coupling transformer coupled to its output terminal via a power line, the primary winding of the first coupling transformer being connected to the first terminal of the main switch at one of a set of output terminals;

the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on the power line;

the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode;

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch, the main switch is switched on, otherwise, the main switch is switched off;

the method comprises the following steps:

when receiving a starting command, the turn-off control module transmits a periodic excitation pulse source to the turn-off device through the power line again so as to charge the energy storage capacitor until the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch, so as to trigger the turn-off device to execute conduction operation, and thus the corresponding battery assembly is recovered to a series connection state from a turn-off state.

The method described above, wherein:

the turn-off device comprises a parallel capacitance connected between the first and second terminals of the main switch;

after the turn-off device performs turn-off operation and closes the main switch, the excitation pulse source is stopped to cause charge loss of the energy storage capacitor and cannot reach the conduction threshold voltage of the main switch, and at this stage, a parallel capacitor connected in parallel with the main switch provides a conduction path for the excitation pulse source to propagate by bypassing the main switch.

The method described above, wherein:

the turn-off device comprises a normally-open parallel switch connected between a first terminal and a second terminal of the main switch, a control terminal of the normally-open parallel switch being connected to a control terminal of the main switch;

after the turn-off device executes turn-off operation and closes the main switch, the excitation pulse source is stopped to cause the charge loss of the energy storage capacitor and cannot reach the conduction threshold voltage of the main switch, and at this stage, the normally-open parallel switch entering the conduction state provides a conduction path for the excitation pulse source to propagate by bypassing the main switch; and

when the turn-off control module receives the starting command and charges the energy storage capacitor again to enable the potential of the energy storage capacitor to reach the conducting threshold voltage of the main switch to turn on the main switch, the potential of the energy storage capacitor also controls the normally-open parallel switch to be turned off.

The method described above, wherein:

and a parallel resistor connected in parallel with the energy storage capacitor is also arranged between the control terminal and the first terminal of the main switch.

The method described above, wherein:

a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are further arranged between the control terminal and the first terminal of the main switch.

The method described above, wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to the control terminal of the main switch through the steering diode;

the dotted terminal is connected to the anode of the steering diode and the control terminal of the main switch is connected to the cathode of the steering diode.

The method described above, wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to a first node through a first capacitor;

a first diode is connected between the synonym end of the secondary winding of the first coupling transformer and the first node;

the anode of the first diode is connected to the synonym terminal of the secondary winding of the first coupling transformer, and the cathode is connected to the first node;

the first node is coupled to the anode of the steering diode and the control terminal of the main switch is coupled to the cathode of the steering diode.

The method described above, wherein:

the stage that the shutdown device does not execute shutdown operation and sets the photovoltaic module corresponding to the shutdown device to be connected into the battery string, and an excitation pulse source sent by the shutdown control module has a first logic state;

when receiving a turn-off command, the turn-off control module firstly inverts an excitation pulse source transmitted to the turn-off device from a first logic state to a second logic state with opposite polarity so as to inform the turn-off device to immediately short-circuit the control terminal and the first terminal of the main switch so as to rapidly turn off the main switch.

The method described above, wherein:

the winding direction of one auxiliary winding of the first coupling transformer is opposite to that of the secondary winding;

the different name end of the auxiliary winding of the first coupling transformer is connected to the base electrode and the same name end of an NPN bipolar transistor, and the emitter electrode of the NPN bipolar transistor is connected to the first terminal of the main switch;

the collector of the NPN bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the NPN bipolar transistor to be conducted when inducing the excitation pulse source of the second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch.

The method described above, wherein:

the winding direction of one auxiliary winding of the first coupling transformer is the same as that of the secondary winding;

the homonymous terminal of the auxiliary winding of the first coupling transformer is connected to the base electrode and the synonym terminal of a PNP bipolar transistor and the emitter electrode of the PNP bipolar transistor through a reversely connected second diode, and the emitter electrode of the PNP bipolar transistor is connected to the first terminal of the main switch;

the collector of the PNP bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the PNP bipolar transistor to be conducted when inducing an excitation pulse source of a second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch;

the anode of the second diode is connected to the base of the PNP bipolar transistor and the cathode is connected to the dotted terminal of the auxiliary winding.

In another non-limiting alternative embodiment of the present invention, another parallel shutdown system for photovoltaic modules is disclosed, characterized in that it essentially comprises:

at least one turn-off control module;

the photovoltaic module comprises a plurality of turn-off devices and a plurality of photovoltaic modules, wherein each photovoltaic module is provided with one turn-off device;

a plurality of photovoltaic modules are connected in series to form a battery pack string;

each turn-off device is used for turning off the photovoltaic component corresponding to the turn-off device to remove the photovoltaic component from the battery string or restoring the photovoltaic component corresponding to the turn-off device from a turn-off state to a series connection state of connecting the photovoltaic components into the battery string;

when the turn-off control module receives a turn-off command, the turn-off control module stops transmitting a periodic excitation pulse source to each turn-off device to inform the plurality of turn-off devices to execute turn-off operation so as to turn off the corresponding photovoltaic assemblies; or

When the turn-off control module receives a starting command, the turn-off control module transmits periodic excitation pulse sources to the turn-off devices again to inform the turn-off devices to execute turn-on operation so as to restore the corresponding photovoltaic assemblies from the turn-off state to the serial connection state;

each turn-off device comprises a main switch for switching off or on between an input and an output thereof, the main switch having a first terminal, a second terminal and a control terminal;

each turn-off device comprises an inductor coupled to its output terminal by a power line, one end of the inductor being connected to a first terminal of the main switch at one of a set of output terminals, the opposite end of the inductor being connected to the anode of a steering diode and the cathode of the steering diode being coupled to the control terminal of the main switch;

the inductor is used for extracting an excitation pulse source loaded on the power line;

the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through the steering diode;

when the potential of the energy storage capacitor reaches the conducting threshold voltage of the main switch, the main switch is switched on, otherwise, the main switch is switched off.

The above parallel shutdown system for photovoltaic module, wherein:

each turn-off device comprises a group of input ends respectively connected to the positive electrode and the negative electrode of the photovoltaic assembly and a group of output ends connected with other turn-off devices in series, and a bypass diode is arranged between the group of output ends of each turn-off device;

when the photovoltaic component is turned off, the bypass diode provides a conduction path between a group of output ends of the turn-off device corresponding to the turned-off photovoltaic component.

The above parallel shutdown system for photovoltaic module, wherein:

and a parallel resistor connected in parallel with the energy storage capacitor is also arranged between the control terminal and the first terminal of the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are further arranged between the control terminal and the first terminal of the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

the turn-off device comprises a parallel capacitance connected between the first and second terminals of the main switch;

after the turn-off device performs the turn-off operation and closes the main switch, a parallel capacitor connected in parallel with the main switch provides a conduction path through which the excitation pulse source propagates bypassing the main switch.

The above parallel shutdown system for photovoltaic module, wherein:

the turn-off device comprises a normally-open parallel switch connected between a first terminal and a second terminal of the main switch, a control terminal of the normally-open parallel switch being connected to a control terminal of the main switch;

after the turn-off device executes turn-off operation and closes the main switch, the normally-open parallel switch entering the conducting state provides a conducting path for the excitation pulse source to propagate by bypassing the main switch; and

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch to switch on the main switch, the potential of the energy storage capacitor also controls the normally-open parallel switch to be switched off.

By taking the safety level factor of the photovoltaic power generation system into full consideration, taking the sum of the photovoltaic power generation system proposed by the U.S. NEC2017-690.12 standard as an example, the photovoltaic power generation system is required to have the shutdown capability at the component level and provide the best system safety. Through the above explanation of the present application, if the voltage needs to be rapidly reduced to below 30 v, the shutdown control module stops sending the excitation pulse to the shutdown device to notify the shutdown device to shut down the respective corresponding photovoltaic module when receiving an external shutdown command sent by a person, and at this time, the dc bus voltage is approximately equal to zero v, and the system has high safety. Therefore, the component-level turn-off solution has the automatic turn-off capability of the component, and can be used for preventing the irreversible damage of the component and the junction box caused by heat generation caused by fire, hot spots or overlarge wiring resistance of the junction box.

In the present application, the shutdown command may be not only from an external shutdown command issued manually, but also from an internal shutdown command, for example, when the shutdown control module detects a high temperature or an open fire or the like through a sensor, the shutdown command of the shutdown control module may be generated by being triggered by various target faults. In the application, when a starting command is received by the turn-off control module, a stimulation pulse (such as square wave) is transmitted to the turn-off device through the power line, so that the energy storage capacitor is charged until the potential of the energy storage capacitor reaches the conducting threshold voltage of the main switch, the turn-off device is triggered to carry out the operation of recovering from the turn-off state to the re-series connection state on the battery string connected with the turn-off device in series, and the voltage can be restored to be supplied to the bus.

Drawings

To make the above objects, features and advantages more comprehensible, embodiments accompanied with figures are described in detail below, and features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following figures.

Fig. 1 is a schematic diagram of an architecture in which photovoltaic modules are connected in series to form a battery string and a plurality of battery strings are connected in parallel.

Fig. 2 is an architecture for configuring a shutdown device for a photovoltaic module and a shutdown control module for a battery string.

Fig. 3 is a first embodiment of a battery string with a shut down control module instructing a shut down device to remain on.

Fig. 4 is a second embodiment of a battery string with a shut down control module instructing a shut down device to remain on.

Fig. 5 is a diagram of the shutdown control module sending an excitation pulse signal onto the power line that can be received by the shutdown device.

Fig. 6 is a first embodiment where the turn-off control module instructs the turn-off device to rapidly switch from on to off.

Fig. 7 is a second embodiment where the turn-off control module instructs the turn-off device to rapidly switch from on to off.

Fig. 8 is an example of the fluctuation of the voltage on the energy storage capacitor during the switching of the switching-off device from on to off.

Fig. 9 is an embodiment of accelerating the discharge of the storage capacitor during the switching of the turn-off device from on to off.

Fig. 10 is a first embodiment where the turn-off control module instructs the turn-off device to rapidly switch from off to on.

Fig. 11 is a second embodiment where the turn-off control module instructs the turn-off device to rapidly switch from off to on.

Fig. 12 is an example of a turn-off device using a single inductor sense pulse signal to charge a storage capacitor.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to various embodiments, but the described embodiments are only used for describing and illustrating the present invention and not for describing all embodiments, and the solutions obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

In the field of photovoltaic power generation, a photovoltaic module or a photovoltaic cell is a core component of power generation. Solar panels are classified into monocrystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells and the like in the mainstream technology, the required service life of the silicon cells is as long as more than twenty years, and monitoring of the durability of the output characteristics of the cells is essential. Many internal and external factors contribute to inefficient power generation of photovoltaic modules: conversion efficiency is reduced due to manufacturing differences or installation differences between the photovoltaic modules themselves or shading or maximum power tracking adaptation. Taking the shielding as an example, if a part of the photovoltaic modules are shielded by clouds, buildings, tree shadows, dirt and the like, the part of the photovoltaic modules can be changed into a load by a power supply and does not generate electric energy any more, the temperature of the photovoltaic modules at a local position with a serious hot spot effect is higher, and some parts of the photovoltaic modules can exceed several hundred degrees centigrade to cause permanent damage such as burning or dark spots, welding spot melting, packaging material aging, glass explosion, corrosion and the like, so that great potential hazards are caused to the long-term safety and reliability of the photovoltaic modules. The photovoltaic power generation system needs to solve the following problems: the working state of each mounted photovoltaic cell panel can be observed in real time or intermittently, the early warning can be carried out on abnormal conditions of over-temperature, over-voltage, over-current, terminal short circuit, various faults and the like of the battery, and the adoption of active safety shutdown or other emergency measures for the abnormal battery is particularly important. The U.S. national electrical code states that the voltage of all photovoltaic power generation systems needs to drop below 30 volts within 10 seconds, and a shutdown device serving as a shutdown function must be configured for the output of the photovoltaic module based on the function of achieving rapid shutdown.

Referring to fig. 1, a photovoltaic module array is the basis for the conversion of light energy to electrical energy in a photovoltaic power generation system. The battery string installed in the photovoltaic module array is shown, with respect to the battery string: each battery string is formed by connecting a plurality of photovoltaic modules which are mutually connected in series, and the photovoltaic modules can be replaced by direct current power supplies such as fuel cells or chemical batteries. A plurality of different battery strings are connected in parallel: although each battery string is composed of a plurality of photovoltaic modules and the plurality of photovoltaic modules inside are connected in series, a plurality of different battery strings are connected in parallel with each other and collectively supply electric energy to an energy collecting device such as a photovoltaic inverter INVT. In a certain battery string, the application takes the series-type multi-stage photovoltaic modules PV1-PVN as an example, and the output voltages V of the series-type multi-stage photovoltaic modules PV1-PVN are respectively_O1-V_ONAfter being superposed with each other willThe total cascade voltage with the higher potential is supplied to the inverter INVT, i.e. the bus voltage V_BUSThe inverter INVT carries out inversion from direct current to alternating current after converging the output power of each of the multistage photovoltaic modules connected in series, and N is a natural number larger than 1. A large-capacity capacitor C is connected between the DC buses LA-LB for providing DC power supply for the inverter_DCIn photovoltaic systems, the bus capacitor must also provide decoupling between the constant input power and the fluctuating output power of the inverter.

Referring to fig. 2, each photovoltaic cell or photovoltaic module in an embodiment is configured with a device for performing monitoring and shutdown, that is, a shutdown device for short. In a certain battery string: the electric energy generated by the first-stage photovoltaic module PV1 is determined by the first-stage shutdown device SD1 to be superimposed on the whole battery string, the electric energy generated by the second-stage photovoltaic module PV2 is determined by the second-stage shutdown device SD2 to be superimposed on the whole battery string, and the electric energy generated by the nth-stage photovoltaic module PVN is determined by the nth-stage shutdown device SDN to be superimposed on the whole battery string. The main function of the shut-off device is explained below, for example: the first-stage shutdown device SD1 to the nth-stage shutdown device SDN need to establish communication with another shutdown control module RSD (Rapid Shut-Down), the communication mechanism is compatible with various current communication schemes such as power line carrier communication or various wireless communications, and the shutdown control module RSD at least needs to be equipped with a human-computer interaction function, that is, can receive commands from human beings. If a fire occurs in a power station for various reasons, a fire fighter must first shut down the entire power generation system to fight the fire, otherwise high voltages may jeopardize personal safety. Taking the artificial active operation turn-off control module RSD as an example: when the shutdown control module RSD receives a shutdown command, for example, an emergency shutdown switch provided by the shutdown control module RSD is pressed to indicate that a shutdown command is reached, at this time, the shutdown control module RSD immediately sends a first command, that is, a shutdown command, to the multi-stage shutdown device SD1-SDN based on communication, and may be represented by a logic level signal, so as to notify the multi-stage shutdown device SD1-SDN to shut down the corresponding photovoltaic module PV1-PVN, so that the voltage output by the battery string connected between the dc buses LA-LB immediately drops to approximately zero as desired.

Referring to fig. 2, the present application, in an optional but not necessary embodiment, assumes that the interior of the string of cells is connected in series with a first stage photovoltaic module PV1, a second stage photovoltaic module PV2, and so on, to an nth stage photovoltaic module PVN. It can be known that the total string-level voltage that can be provided on an individual certain battery string is approximately equal to: the voltage value V output by the first-stage photovoltaic module PV1_O1Plus the voltage V output by the photovoltaic module PV2 of the second stage_O2Then, the voltage V output by the photovoltaic module PV3 of the third stage needs to be added_O3…, and so on, adding up to the voltage value V output by the photovoltaic module PVN of the Nth stage_ONThe total cascade voltage is calculated to be equal to V_O1+V_O2+…V_ON. The cascade voltage obtained by superposing the voltages output by the multi-stage photovoltaic modules on the bus LA-LB is transmitted to electric equipment such as a combiner box or an inverter for combination and inversion, and then is connected to the grid or used locally. The photovoltaic modules PV1-PVN correspond to the shutdown devices SD1-SDN, and the specific scheme of superposing cascade voltage is that the first-stage shutdown devices SD1, the second-stage shutdown devices SD2, … and the like are connected in series through power lines until the Nth-stage shutdown devices SDN and the like. Basic definition regarding the shut-off device: the shutdown device is used to shut down the corresponding photovoltaic module for removal from the string of battery packs, or in the present application, the shutdown device is used to restore the corresponding photovoltaic module from a shutdown state to a series connection state into the string of battery packs.

Referring to fig. 2, it is mentioned that when the shutdown control module RSD sends a so-called shutdown command to the shutdown devices SD1-SDN, the shutdown devices SD1-SDN are notified to shut down the corresponding photovoltaic modules PV1-PVN to ensure system safety, the voltage between the dc buses LA-LB may be pulled down to be nearly equal to zero as desired to ensure safety, and the shutdown control module RSD is ready to receive a startup command at any time. The start command may be generated at any time, for example, when a fire alarm occurs to cut off the entire battery string, and after the fire alarm is released, the system needs to be restarted to enable the photovoltaic power generation system to enter the working state again to supply voltage to the bus.

Referring to fig. 2, the control mode for restarting the system again after it is turned off is: the shutdown control module RSD, upon receiving a startup command, sends a startup instruction to the plurality of shutdown devices SD1-SDN opposite to the aforementioned shutdown instruction to inform the shutdown devices to restore the respective corresponding photovoltaic modules PV1-PVN from the shutdown state to the series-connected state. As is known, the shutdown control module RSD at least needs to be equipped with a human-computer interaction function, the start command may be a command issued manually, and pressing a start switch equipped in the shutdown control module RSD can represent that a start command is reached, and the shutdown control module needs to immediately issue a second command, i.e., a start command, to the shutdown device SD1-SDN, where the second command may be represented by a logic level signal. The data or instruction communication between the shutdown control module and the shutdown device can be power line carrier or wireless communication, and even the excitation pulse provided by the application is used as a communication means. The shutdown devices SD1-SDN receive a startup command and then restore their respective corresponding photovoltaic modules from a shutdown state to a series-connected state, and the voltage output by the battery string between the dc buses LA-LB immediately restores to provide a cascade voltage to the buses as desired, where the voltage level of the cascade voltage is very high and can be typically as high as several hundred volts or even thousands of volts. Compared with the embodiment of fig. 1 without any shutdown measures, the embodiment of fig. 2 has a fast shutdown function and meets the safety specification, and meets the user requirement of component-level high-reliability shutdown.

With reference to fig. 3, it is observed in the whole link of the multi-stage shutdown device SD1-SDN series connection: the second output of any preceding stage of turn-off device is coupled to the first output of an adjacent succeeding stage of turn-off device, thereby satisfying: the maximum total string-level voltage that can be provided in a battery string is equal to the final sum of the output voltages of the respective multi-level shutdown devices SD 1-SDN. The specific relationship is as follows: the second output O2 of the first stage shutdown device SD1 is coupled to the first output O1 of the adjacent succeeding stage, i.e. the second stage shutdown device SD2, the second output O2 of the second stage shutdown device SD2 is coupled to the first output O1 of the adjacent succeeding stage, i.e. the third stage shutdown device SD3, until the second output NO2 of the N-1 stage shutdown device is coupled to the first output O1 of its succeeding stage shutdown device SDN. The voltage output by each of the multi-stage turn-off devices is equivalent to the cascade voltage obtained by superposing the multi-stage photovoltaic modules and is transmitted to the energy collecting device. We can also observe that the first output O1 of the first stage shutdown device SD1 is coupled to the bus bar LA, and can also observe that the second output O2 of the last nth stage shutdown device SDN is coupled to the bus bar LB.

Referring to fig. 3, the shutdown device is used to shut down the photovoltaic module corresponding thereto for removal from the string of battery packs or to restore the photovoltaic module corresponding thereto from the shutdown state to the series-connected state of the connected string of battery packs. The first input of any one of the turn-off devices is coupled to the positive pole of the corresponding photovoltaic module and the second input of the turn-off device is coupled to the negative pole of the corresponding photovoltaic module. Such as: a first input N1 of the shutdown device SD1 is coupled to the positive pole of the photovoltaic module PV1 and a second input N2 of the shutdown device SD1 is coupled to the negative pole of thephotovoltaic module PV 1. In another more representative example: a first input N1 of the shutdown device SDN is coupled to the positive pole of the respective photovoltaic module PVN and a second input N2 of said shutdown device SDN is coupled to the negative pole of the photovoltaic module PVN. In the field, any one of the turn-off devices includes a switching element disposed between the first input terminal N1 and the first output terminal O1, and may further include a switching element disposed between the second input terminal N2 and the second output terminal O2, so that if the turn-off device needs to turn off the corresponding photovoltaic module and remove the corresponding photovoltaic module from the battery string, the switching element is controlled to be turned off, and conversely, if the turn-off device needs to restore the corresponding photovoltaic module from the off state to the series connection state of the connected battery string, the switching element is controlled to be turned on. Naturally, in the field of photovoltaic power generation, there are several alternative variants of the shut-off device for so-called photovoltaic modules, but the basic functions are: the photovoltaic module is switched off or on. A bypass switch diode provided in the turn-off device is additionally coupled between the first output NO1 and thesecond output NO 2. It is noted that the bypass diode is arranged with its anode connected to the second output NO2 and with its cathode connected to the first output NO1, so that the bypass diode is turned off in the reverse direction when the photovoltaic module is controlled by the corresponding turn-off device to return to the series-connected state, and so that the bypass diode is turned on in the forward direction when the photovoltaic module is switched to the turned-off state by the corresponding turn-off device.

Referring to fig. 3, the operating mechanism of the shut-off device can be generally described as: if the switching element between the input and the output is on, this means that the turn-off device will turn on the corresponding photovoltaic module, which corresponds to the photovoltaic module being connected to the string of batteries and contributing its voltage component to the string voltage, and the bypass diode is then turned off in the opposite direction. Correspondingly, if the switching element between the input terminal and the output terminal is turned off, it means that the turn-off device performs a turn-off operation on the corresponding photovoltaic module, so that the photovoltaic module can no longer contribute its voltage component to the string voltage, that is, the bypass diode is turned on in the forward direction when the photovoltaic module is removed from the battery string, and the practical meaning is that: and a bypass diode provides a conduction path between two output ends of the turn-off device corresponding to the turned-off photovoltaic module.

Referring to fig. 3, a parallel shutdown system implies, as the name implies, that the shutdown device and the corresponding photovoltaic module are connected in parallel. The shutdown devices SD1-SDN and the photovoltaic modules PV1-PVN are connected in parallel in a one-to-one manner, so that one shutdown device is provided for each photovoltaic module. Whether the shutdown device SD1-SDN performs shutdown operation or whether the SDN performs turn-on operation is controlled by the shutdown control module RSD, and the shutdown control module RSD is artificially controlled or controlled by a preset condition, for example, occurrence or release of high temperature, high voltage, overcurrent, open flame or extreme cold weather can trigger the shutdown control module RSD to issue a shutdown or turn-on command, and the multiple photovoltaic modules are connected in series to form a battery string. The shutdown device is used for shutting down the photovoltaic component corresponding to the shutdown device to remove the photovoltaic component from the battery string or restoring the photovoltaic component corresponding to the shutdown device from the shutdown state to the series connection state of the connection battery string. Typical shutdown devices SDN for example are used to shut down the corresponding photovoltaic module PVN from the string or to restore the corresponding photovoltaic module PVN from a shutdown state to a series access state into the string. When the turn-off control module RSD receives the turn-off command, for example, the emergency turn-off switch/voice-operated switch/turn-off button/touch screen turn-off switch provided in the turn-off control module is activated to issue the turn-off command, and the turn-off control module has a man-machine interaction function. The shutdown control module RSD adopts the following scheme for the mode of commanding a so-called shutdown to the exemplary shutdown device SDN: the shutdown control module RSD is configured to send the excitation pulse source PUS to the shutdown device SDN uninterruptedly or at least intermittently or periodically when controlling the shutdown device SDN to be in a normal on state to ensure that the battery assembly PVN is able to contribute its own voltage component to the cascade voltage, and the photovoltaic assembly PVN is now able to contribute its own voltage component to the bus since the shutdown device SDN is turned on and is directly connected in series between the buses LA-LB. In contrast, if the shutdown control module RSD attempts to control the shutdown device SDN to be in the shutdown state such that the battery assembly PVN is removed from between the dc buses LA-LB, it is necessary to stop sending the so-called excitation pulse source PUS to the shutdown device SDN, and it is needless to say that the photovoltaic assembly PVN cannot contribute any more voltage component to the buses because the shutdown device SDN is in the shutdown state and is directly removed from between the dc buses LA-LB. Generally, the mode in which the shutdown control module instructs the shutdown device SDN to shutdown is considered as follows: if the supply of periodic excitation pulse sources PUS to the shutdown device SDN is stopped, this may indicate that the shutdown device SDN needs to perform a shutdown operation on the battery assembly PVN. It is noted that, although the shutdown device SDN is taken as an example, the electrical characteristics of the other shutdown devices SD1-SD (N-1) remaining in the shutdown device SD1-SDN are not substantially different from the shutdown device SDN.

Referring to fig. 3, the turn-off device SDN comprises a main switch M and a first coupling transformer T₁And further comprising two inputs N1-N2 connected to the positive and negative poles of the photovoltaic module PVN, respectively, and the turn-off device SDN further comprises two outputs O1-O2 connected in series with the remaining other turn-off devices, two of the outputs of which can be turned on by the turn-off device SDNTo provide the output power and output voltage of the photovoltaic module PVN. A bypass diode DP is further arranged between the two outputs O1-O2 of the shutdown device SDN, and when the photovoltaic module PVN is shutdown by the shutdown device SDN, the bypass diode DP provides a conduction path between the two outputs O1-O2 of the shutdown device SDN corresponding to the shutdown photovoltaic module PVN. Assuming that the main switch M of the turn-off device SDN has a first terminal and a second terminal and a control terminal, the first terminal being connected to the second output O2 of the turn-off device and the second terminal being connected to the second input N2, the main switch is selectively connected between the second input and the second output is the embodiment adopted in fig. 3. In the alternative, the first terminal of the main switch M may also be connected to the first output O1 of the turn-off device and the second terminal to the first input N1, i.e. in the alternative the main switch is selectively connected between the first input and the first output. The main switch is used for switching between the input terminal and the output terminal, for example, the first input terminal N1 and the first output terminal O1 can be controlled to be switched between the input terminal and the output terminal, and for example, the second input terminal N2 and the second output terminal O2 can be controlled to be switched between the input terminal and the output terminal: when the main switch is switched off, the corresponding photovoltaic module is removed from the battery pack string, and when the main switch is switched on, the corresponding photovoltaic module is restored to be connected into the battery pack string.

Referring to fig. 3, the turn-off device SDN in this embodiment comprises said first coupling transformer T coupled to the second output O2 by a power line₁The specific connection relationship is as follows: first coupling transformer T₁The primary winding L1 and the first terminal of the main switch are connected to one of two output terminals O1-O2, namely to the second output terminal O2. In detail, the primary winding L1 is connected between the second output O2 of the shut-off device SDN and the bus bar LB. In the alternative embodiment of fig. 3, the second terminal of the main switch M is directly connected to the second input N2 and the so-called first input N1 and first output O1 in the topology of the turn-off device SDN are directly coupled together.

Referring to fig. 3, a modification is made based on fig. 3 but in an alternative not shown: the shut-down device SDN comprises a first coupling transformer coupled to, for example, a first output O1 via a power lineT₁In this embodiment, which is not shown, it corresponds to the first coupling transformer T which we will describe₁The primary winding L1 of the primary winding is directly moved between the second output O2 of the adjacent previous-stage shutdown device SD (N-1) and the first output O1 of the next-stage shutdown device SDN. This solution also modifies the position of the main switch M: the main switch is moved from between the second output O2 and the second input N2 previously connected to the turn-off device to between the first output O1 and the first input N1 connected to the turn-off device, setting a first terminal of the main switch to the first output O1 of the turn-off device and a second terminal to the first input N1. In the alternative, the transformer T is connected by the first coupling₁The primary winding moves between the second output O2 of the shutdown device SD (N-1) and the first output O1 of the shutdown device SDN, then in this alternative embodiment: first coupling transformer T₁The primary winding and the first terminal of the main switch are connected to the other of the two output terminals O1-O2, i.e. the first output terminal O1. In contrast to the example of fig. 3, this alternative embodiment assumes that the primary winding L1 is connected between a first output of the shutdown device SDN and a second output of the shutdown device SD (N-1). Thus in an alternative embodiment to fig. 3: we can provide that the second terminal of the main switch is directly connected to the first input N1, and that in the turn-off device SDN so-called second input N2 and second output O2 are directly coupled together. An alternative to making the correction based on fig. 3 is to prove that there are two options: the main switch is selectively connected between the second input end and the second output end, so that the primary winding of the first coupling transformer and the first terminal of the main switch are connected to the second output end of the two output ends, namely, fig. 3; the main switch is selectively connected between the first input terminal and the first output terminal, and the primary winding of the first coupling transformer and the first terminal of the main switch are connected to the first of the two output terminals, the latter being based on the modification of fig. 3.

Referring to fig. 3, in summary, it is the embodiment of fig. 3 explained above that the main switch M is selectively connected between the second input terminal and the second output terminal. In an alternative, the first terminal of the main switch M may also be connected to the first output O1 of the turn-off device and the second terminal to the first input N1, i.e. in the alternative to fig. 3 the main switch is selectively connected between the first input and the first output. In summary: the main switch is used to switch the input terminal and the output terminal, such as to switch the first input terminal N1 and the first output terminal O1, and to switch the second input terminal N2 and the second output terminal O2. When the main switch is switched off, the corresponding photovoltaic module is removed from the battery pack string, and when the main switch is switched on, the corresponding photovoltaic module is restored to be connected into the battery pack string.

Referring to fig. 3, a first coupling transformer T₁The secondary winding L2 is used for sensing or extracting the excitation pulse source PUS loaded on the power line, the sensed excitation pulse source PUS charges the energy storage capacitor C1 connected between the control terminal and the first terminal of the main switch through a steering diode D2, and when the potential of the energy storage capacitor C1 reaches the turn-on threshold voltage of the main switch, the main switch M is turned on, otherwise, the main switch M is turned off. This solution is not only applicable to the embodiment of fig. 3, but also to an alternative embodiment not shown in fig. 3, in which one end of the secondary winding L2 of the first coupling transformer, e.g. the synonym and the first terminal of the main switch, are coupled to the second output O2, in fig. 3, an end of the secondary winding L2 of the first coupling transformer, e.g. the synonym and the first terminal of the main switch, are coupled to the first output O1, which differs from the above-mentioned position of the main switch, in fig. 3, the main switch is arranged between the second input N2 and the second output O2, and in an alternative embodiment, the main switch is shifted to be arranged between the first input N1 and the first output O1, but has the same function. The power line or series line referred to herein may actually be considered as an extension of the bus bar. The main switch M may be a power switch such as a power MOSFET, i.e., a metal oxide semiconductor field effect transistor, or an IGBT, i.e., an insulated gate bipolar transistor. The main switch is a three-port electronic switch, the mosfet includes a gate, a source and a drain, and the igbt includes a gate, a collector and an emitter. Oxidation of metalsAn i-semiconductor field effect transistor has a second terminal, such as a drain D, and has a first terminal, such as a source S, and a control terminal, such as a gate G, while a so-called insulated gate bipolar transistor has a second terminal, such as a collector C, and has a first terminal, such as an emitter E, and a control terminal, such as a gate G. The turn-on characteristic of a general mosfet is turned on when a voltage value up to a turn-on threshold voltage is applied between the gate and the source, and the turn-on characteristic of a general igbt is turned on when a voltage value up to a turn-on threshold voltage is applied between the gate and the emitter. Power semiconductor switching devices are typically: metal oxide semiconductor field effect transistors, bipolar transistors, thyristors, gate turn-off thyristors, integrated gate commutated thyristors, turn-off thyristors and emitter turn-off thyristors, insulated gate bipolar transistors, and the like.

Referring to fig. 3, a first coupling transformer T₁Is connected to a second output O2, and is connected to a primary winding L1 and a main switch M having first and second terminals and a control terminal. The signal at the control terminal of the main switch M determines whether the first and second terminals of the main switch are on or off, and the coupling transformer can be replaced by a transformer. The first coupling transformer, because of its coupling effect, has its secondary winding L2 used to extract or inductively switch off the excitation pulse source PUS that the control module RSD loads onto the power line, which may be pulsed voltage and is most common and most frequently used with square wave pulses. In order to satisfy the requirement that the secondary winding L2 can induce and capture the excitation pulse source PUS, a first coupling transformer T is provided₁The synonym terminal of the secondary winding L2 is coupled to the first terminal of the main switch M, i.e. to the common node NCO and the common node NCO is considered to have the reference ground potential GR. A first coupling transformer T is also provided as in FIG. 3₁The dotted terminal of the secondary winding is coupled to a control terminal of the main switch M, such as gate G, through a steering diode D2. Specifically, the method comprises the following steps: first coupling transformer T₁Is coupled to a first node N1 via a first capacitor CC, the steering diode is connected between the first node N1 and the control terminal of the main switch, and the anode of the steering diode D2The terminal is connected to said first node N1 and the cathode terminal is connected to the control terminal of the main switch.

Referring to fig. 3, in addition to this, we also have a first coupling transformer T₁Between the synonym terminal of the secondary winding L2 and said first node N1 mentioned above is additionally connected a separate first diode D1, note that the anode of the first diode D1, which has the reference ground GR, is connected to the first coupling transformer T₁The synonym terminal of the secondary winding L2, and the cathode of a first diode D1 is provided to be connected to the first node N1. The source of excitation pulses PUS captured or induced by the secondary winding L2 from the mains is charged by the steering diode D2 to the storage capacitor C1 connected between the control terminal and the first terminal of the main switch M, i.e. to said storage capacitor C1 arranged between the gate G and the common node NCO by the excitation signal, which steering diode allows the induced pulses to charge the storage capacitor unidirectionally. In an alternative embodiment a parallel resistor R1 is also provided between the control terminal of the main switch M and the first terminal/common node NCO in parallel with the energy storage capacitor. The induced excitation pulse source PUS charges the energy storage capacitor C1, the main switch M is turned on when the potential of the energy storage capacitor C1 reaches the turn-on threshold voltage of the main switch M, otherwise, the main switch M is turned off when the potential of the energy storage capacitor C1 does not reach the turn-on threshold voltage of the main switch M. According to the semiconductor physics theory, the equivalent physical model of the solar module comprises factors such as diode factors, equivalent series resistance and equivalent parallel resistance, and the output impedance characteristics of the photovoltaic module are greatly different under the influence of different illumination intensities and different temperature environments. The transmission path of the excitation pulse is transmitted through the internal resistance of each photovoltaic module, and the degradation degree of the excitation pulse on the transmission path of the multi-stage photovoltaic module is hardly predictable under the condition that the impedance of the photovoltaic module is greatly deviated along with the external environment. In the fuzzy signal processing, the combination of the first capacitor CC and the first diode D1 is used to raise the potential of the excitation pulse source PUS by a certain amplitude in at least some embodiments to avoid excessive attenuation.

Referring to fig. 4, the master in the SDN shutdown deviceFirst terminal of switch M and first coupling transformer T₁The so-called primary winding L1 is connected to the second output O2, the first capacitor CC and the first diode D1 being omitted with respect to fig. 3. Providing a first coupling transformer T in a so-called shut-down device SDN₁The first terminal of the primary winding L1 and the main switch M are connected to the second output O2 and the second terminal of the main switch M is connected to the second input N2. Wherein it is noted that the first coupling transformer T₁The secondary winding L2 is used to extract the excitation pulse source PUS applied to the power line, and as a coupling function of the signal, the excitation pulse source PUS signal induced or captured by the secondary winding L2 is charged via the aforementioned steering diode D2 to the energy storage capacitor C1 connected between the control terminal, e.g., the gate G, and the first terminal, e.g., the source electrode S, of the main switch M. The common node NCO and the first terminal are coupled together. Optionally, a parallel resistor R1 connected in parallel with the energy storage capacitor C1 is also provided between the control terminal of the main switch and the common node NCO/first terminal. In an alternative embodiment the steering diode D2 has its anode terminal connected directly to the dotted terminal of the secondary winding L2 and its cathode terminal connected to the control terminal of the main switch. In an alternative embodiment a pair of anti-series connected zener diodes Z1-Z2 connected in parallel with the energy storage capacitor C1 are also provided between the control terminal of the main switch M and the first terminal or common node. The reverse series connection of the zener diodes Z1-Z2 refers to: the anodes of zener diodes Z1 and Z2 are interconnected, the cathode of zener diode Z1 is connected to the first terminal or common node NCO, and the cathode of zener diode Z2 is connected to the control terminal of the main switch such that the pair of series connected zener diodes is connected in parallel with the energy storage capacitor C1, note that this embodiment may also be applied to the embodiment of fig. 3 as well. The back-to-back reverse series connected voltage stabilizing diodes are used for clamping the voltage drop between the control terminal and the first terminal of the main switch, and the power switch is prevented from being damaged.

Referring to fig. 5, there are several ways for the shutdown control module RSD to supply periodic excitation pulse sources PUS to the shutdown device SDN or to the power line. In this embodiment: the excitation pulse source PUS is pulsed in the form of high and low logic levels by the turn-off control module RSDThe signal generator generates, and may be an ac signal. Second coupling transformer T in this embodiment₂There is also a primary winding and a secondary winding, and the primary winding is connected in series to the power line, and the primary winding and the series of cut-off devices SN1-SDN are connected in series by the power line. A second coupling transformer T is also provided₂Is connected in series between a further reference ground GG, denoted second reference ground potential, to be distinguished from the above-mentioned reference ground potential GR, denoted first reference ground potential, to avoid confusion, and the potentials of both may be different, and the coupling capacitor OC. The working mechanism of the turn-off control module RSD is as follows: outputting the generated excitation pulse source PUS via a driver DR, and finally passing the excitation pulse source PUS through a second coupling transformer T₂The primary winding and the secondary winding of the transformer are coupled to be propagated or applied to the power line, where the so-called excitation pulse source PUS is a square wave or similar other pulsating signal. Any scheme in the art for loading or propagating a periodic or intermittent pulsed signal onto a power line may be substituted for the embodiment of fig. 5.

Referring to fig. 6, if the shutdown control module RSD tries to control the shutdown device SDN to be in the normal on state, the excitation pulse source PUS must be continuously or intermittently sent, and the shutdown device SDN senses the excitation pulse source PUS and charges its own energy storage capacitor to maintain the shutdown device SD on, that is, the condition that the potential of the energy storage capacitor C1 reaches the on threshold voltage of the main switch is satisfied. If the shutdown control module RSD no longer expects the shutdown device SDN to be in a normal on state but to be turned off, for example, if the shutdown control module RSD receives a shutdown command in an emergency, the excitation pulse source PUS that is originally sent to the shutdown device SDN continuously or intermittently or periodically may be stopped, in which case the energy storage capacitor C1 may be powered down and no longer meet the condition that the potential reaches the on threshold voltage of the main switch. The mode of issuing a shutdown instruction to the shutdown device SDN by the shutdown control module is as follows: and stopping supplying the periodical excitation pulse source to the shutdown device SDN to inform the shutdown device SDN to perform shutdown operation on the photovoltaic module PVN corresponding to the shutdown device SDN. Introduction to the U.S. electrical specifications states that the voltage of a photovoltaic power generation system must drop below 30 volts in 10 seconds, and the embodiment of fig. 3-5, while capable of shutting down the entire battery string in a timely manner, is a more secure and safer way for the shutdown device shown in fig. 6 to shut down the system more quickly when the shutdown control module RSD receives a shutdown command.

Referring to fig. 6, in a phase when the shutdown control module RSD does not receive the shutdown command, the shutdown device SDN does not perform the shutdown operation and maintains the on connection with the photovoltaic device PVN, and the excitation pulse source PUS sent by the shutdown control module RSD has a first logic state, such as a positive potential relative to a zero potential, which can still effectively ensure that the excitation pulse source PUS captured by the first coupling transformer continuously charges the energy storage capacitor C1 connected between the control terminal and the first terminal of the main switch through a steering diode D2, so as to satisfy the condition that the potential of the energy storage capacitor reaches the on threshold voltage of the main switch. As a more rapid turn-off mode when the turn-off control module RSD receives the turn-off command, when receiving the turn-off command, the turn-off control module first inverts the excitation pulse source PUS delivered to the turn-off device SDN from the first logic state to a second logic state with opposite polarity, for example, a negative potential relative to a zero potential, and notifies the turn-off device SDN to immediately short-circuit the control terminal and the first terminal of the main switch so as to rapidly turn off the main switch M. See fig. 6 for a first coupling transformer T₁The auxiliary winding L3 has a winding direction opposite to that of the secondary winding L2, and therefore, the magnetic induction directions of the two windings are different. The purpose of actively employing the additional auxiliary winding L3 in this embodiment is: first coupling transformer T₁The synonym terminal of the auxiliary winding L3 is connected to the base of a NPN bipolar transistor Q of the switching type, the synonym terminal of the auxiliary winding L3 and the emitter of the NPN bipolar transistor, which are connected to the first terminal of the main switch M, i.e. the synonym terminal of the auxiliary winding L3 and the emitter of the NPN bipolar transistor have the reference ground potential GR. Note that the collector of the NPN bipolar transistor Q is also connected to the control terminal of the main switch, e.g., the gate G. If the pump pulse source PUS has the first logic state, the auxiliary winding L3 cannot effectively sense the pump pulse source PUS having the first logic state or activate the NPN bipolar transistor, and vice versa when the control circuit is turned offWhen the module RSD receives the turn-off command, the NPN bipolar transistor Q is activated to conduct due to the excitation pulse source PUS being flipped from the original first logic state to the subsequent second logic state of opposite polarity, so that the excitation pulse source PUS of the second logic state can be smoothly captured or sensed by the auxiliary winding L3, and the control terminal of the main switch M is immediately shorted together with its first terminal to rapidly turn off the main switch M, so that the control terminal of the main switch M is at the same potential as the so-called reference ground GR. The main shutdown control principle is: this embodiment is applicable to the embodiment of fig. 3-5, in which the auxiliary winding L3 senses the excitation pulse source PUS in the second logic state, and rapidly energizes the NPN bipolar transistor Q to turn on, thereby shorting the control terminal and the first terminal of the main switch to close the main switch M.

Referring to fig. 7, during the time period when the shutdown control module RSD does not receive the shutdown command, the shutdown device SDN does not perform the shutdown operation and maintains the on-connection with the photovoltaic module PVN, and the excitation pulse source PUS sent by the shutdown control module RSD has the first logic state, such as a positive level relative to zero potential, which may ensure that the excitation pulse source PUS sensed by the first coupling transformer continuously charges the energy storage capacitor C1 connected between the control terminal and the first terminal of the main switch through the steering diode D2, and meets the condition that the potential of the energy storage capacitor reaches the on-threshold voltage of the main switch. As a faster shutdown mode when the shutdown control module RSD receives the shutdown command, when receiving the shutdown command, the shutdown control module first flips the excitation pulse source PUS delivered to the shutdown device SDN from the first logic state to an opposite second logic state, such as a negative level with a relatively zero potential, to notify the shutdown device SDN to immediately short-circuit the control terminal and the first terminal of the main switch to rapidly turn off the main switch M, and then stops delivering the periodic excitation pulse source PUS to the shutdown device or only sends the excitation pulse source PUS having the second logic state instead of the first logic state to the shutdown device, which is applicable to the embodiment of fig. 6. The stopping of the supply of the so-called excitation pulse source PUS to the shutdown device is intended to stop the charging of the energy storage capacitor, and as an alternative, merely sending the excitation pulse source PUS having the second logic state instead of the first logic state to the shutdown device is to clamp both the control terminal of the main switch and the first terminal of the main switch directly to the same potential, either means operating independently or in cooperation, with the end result that the shutdown device SDN performs the shutdown operation and disconnects from the pv module PVN. The first logic state of the excitation pulse source is, for example, a positive potential relative to a zero potential or a reference potential, and the second logic state of the excitation pulse source is, for example, a negative potential relative to a zero potential or a reference potential, so that the two logic states have opposite polarities.

Referring to fig. 7, as an alternative to the embodiment of fig. 6, it is necessary to provide a first coupling transformer T₁The winding direction of the other auxiliary winding L3 is the same as that of the secondary winding L2, and therefore the magnetic induction directions are the same. The purpose of actively employing the additional auxiliary winding L3 in this embodiment is: first coupling transformer T₁The dotted terminal of the auxiliary winding L3 is connected to the base of a PNP bipolar transistor Q via a second diode D3, the synonym terminal of the auxiliary winding L3 and the emitter of the PNP bipolar transistor Q are connected to the first terminal of the main switch M, that is, the synonym terminal of the auxiliary winding and the emitter of the PNP bipolar transistor Q have the reference ground potential GR. The collector of the PNP bipolar transistor is connected to the control terminal of the main switch M, such as the gate G, and the auxiliary winding L3 excites the PNP bipolar transistor Q to turn on when the excitation pulse source PUS of the second logic state is induced, thereby shorting the control terminal and the first terminal of the main switch and closing the main switch M. Note that the anode of the second diode D3 is connected to the base of the PNP bipolar transistor and its cathode is connected to the dotted terminal of the auxiliary winding L3. When the excitation pulse source PUS has the first logic state, although the auxiliary winding L3 senses the excitation pulse source PUS in the first logic state, the bipolar transistor cannot be turned on, so that the auxiliary winding is considered to be inoperative, otherwise, when the turn-off control module RSD receives the turn-off command, the auxiliary winding L3 senses the excitation pulse source PUS in the second logic state, because the excitation pulse source PUS is turned over from the original first logic state to the second logic state with opposite polarity, so that the PNP bipolar transistor Q is turned on and immediately the PNP bipolar transistor Q is turned onThe control terminal of the main switch M and its first terminal are shorted together to turn off the main switch M rapidly so that the control terminal of the main switch M and the so-called reference ground GR are at the same potential. The main shutdown control principle at this time is: the auxiliary winding L3, when it senses the excitation pulse source PUS in the second logic state, will rapidly turn on the PNP bipolar transistor Q, thereby shorting the control terminal and the first terminal of the main switch to close the main switch M, which can be applied to the embodiments of fig. 3-5.

Referring to fig. 8, the method for the shutdown device SD to maintain the on state of the power generation system and normally generate power before receiving the instruction of the shutdown command includes: before a turn-off control module RSD waiting for a turn-off command receives the turn-off command, namely before a time TS of a time axis, the turn-off control module RSD controls a turn-off device SDN to enter a conducting mode, so that a series of photovoltaic modules PV1-PVN corresponding to the turn-off device entering the conducting mode are connected between DC buses LA-LB to supply power to the DC buses, and the voltage of the DC buses is approximately equal to V_O1+V_O2+…V_ON. The periodic supply of the excitation pulse source PUS to the shutdown device causes acurve 106 of the voltage fluctuation of the energy storage capacitor to resemble a sawtooth wave, and an upward slope in thecurve 106 is charging the energy storage capacitor and a downward slope is discharging or leaking the energy storage capacitor, because the excitation pulse source PUS is a high-low level square wave similar to a level jump and causes the voltage of the energy storage capacitor to exhibit a sawtooth fluctuation. The voltage fluctuation of the energy storage capacitor in the case of a power MOSFET also represents the fluctuation of the gate-source voltage VGS. When receiving a shutdown command, the shutdown control module RSD indicates that the shutdown command is reached by, for example, pressing the emergency shutdown switch, and at this time, the shutdown control module RSD immediately stops sending the excitation pulse source PUS to the shutdown device SD, and the energy storage capacitor starts to rapidly lose power due to the loss of the excitation pulse source PUS at the time TS when the shutdown command is sent, and the charge is lost at thetime TE 1. Of course, the main switch does not wait until the charge of the energy storage capacitor approaches zero, but at a certain time node between the times TS-TE1, the main switch M is turned off because the potential of the energy storage capacitor cannot reach the turn-on threshold voltage of the main switch.

Referring to fig. 9, in conjunction with fig. 8, the shutdown control module stops delivering the excitation pulse source to the shutdown device when receiving the shutdown command to notify the shutdown device to perform the shutdown operation, that is, the embodiments in fig. 3 to 5, which start to power down the energy storage capacitor C1 at the moment of issuing the command to shutdown, that is, at the moment TS, because the excitation pulse source PUS is lost, until the charge on the energy storage capacitor TE1 is lost to be used up at a subsequent moment. The embodiment illustrated with fig. 6-7 is used for comparison, and the shutdown operation is performed modified as follows: turning over the excitation pulse source PUS supplied to the turn-off device SDN from an original first logic state to a second logic state of opposite polarity, informing the turn-off device SDN to immediately short-circuit the control terminal and the first terminal of the main switch, and rapidly turning off the main switch M to perform the turn-off operation, as shown in fig. 9, these embodiments cause the control terminal and the first terminal of the main switch to be transiently short-circuited at a time instant TS at which an instruction of turn-off is issued, so that the control terminal and the first terminal are at the same potential. The same principle that the main switch does not wait until the charge of the energy storage capacitor closes until it is lost faster, almost directly falling to zero at time TE2, starts the signal inversion at time TS, but the main switch M is turned off at some time node between times TS-TE2 and almost around time TS due to the control terminal of the main switch and its first terminal being short-circuited transiently. The time between TS-TE2 in FIG. 9 is much less than the time between TS-TE1 in FIG. 8. Comparing the control schemes of fig. 8-9 we can easily get undoubted results: the solution of fig. 9 using the auxiliary winding greatly shortens the response time of the shutdown control module to execute the shutdown command when it receives the shutdown command. If the bus voltage needs to drop below 30 volts in 10 seconds, it is clear that the solution with the auxiliary winding is more consistent with the expectation of a rapid bus drop.

Referring to fig. 10, a method of restarting the system again if an attempt is made without hindrance after the shutdown device SDN is shut down under the instruction of shutdown needs to be separately designed. Before the turn-off control module RSD waiting for the start command receives the start command, the turn-off control module RSD controls the turn-off device SDN to enter the turn-off mode, and the turn-off device RSD enters the turn-off modeThe corresponding photovoltaic modules cannot be connected between the direct current buses to supply power to the direct current buses. The main switch is opened, so that the bus can be opened to guarantee safety, but at the same time, the negative disadvantage is caused, namely that an excitation pulse source PUS sent by the turn-off control module RSD can not be smoothly propagated in a closed loop, wherein the closed loop refers to a loop formed by the main switch and a series of battery assemblies PV1-PVN connected in series and located between the buses LA-LB. The unique design of the system restart method is as follows: the shutdown device SDN is configured to perform an operation of recovering from the shutdown state to the re-series connection state on the battery string connected in series therewith, that is, when the shutdown control module RSD receives a start command, for example, a physical start switch/touch screen switch/voice-operated switch provided for triggering the shutdown control module is characterized to have reached the start command, the shutdown device SDN is sent a periodic excitation pulse source PUS through the power line again to notify the shutdown device SDN to perform an operation of re-connecting the corresponding photovoltaic module, and at this stage, the shutdown control module RSD immediately sends a start instruction again to the shutdown device. It has been discussed above that the failure of the periodic excitation pulse source PUS, which is delivered again to the shut-down device via the power line due to the opening of the main switch M, to form a closed propagation path via the opened main switch M, in other words, the failure of the secondary winding to sense a pulse, directly causes difficulties in the operation of the shut-down device SDN to perform a re-series connection. The method for solving the problem that the excitation pulse source PUS is transmitted in the closed loop comprises the following steps: the shutdown device SDN is provided with a parallel capacitor CP connected between a first terminal, such as a source, and a second terminal, such as a drain, of the main switch M, and after the shutdown device SDN performs a shutdown operation and closes the main switch M, the parallel capacitor CP connected in parallel with the main switch M provides a conduction path for the excitation pulse source PUS to propagate on the power line. After the shutdown control module RSD receives the starting command, the shutdown control module instructs a shutdown device SDN to recover the corresponding photovoltaic modules PVN from the shutdown state of the system shutdown stage to the series connection state through an excitation pulse source PUS, the power generation system containing the photovoltaic modules PV1-PVN of the battery string is rapidly restarted, and the voltage of the DC bus LA-LB is rapidly increased to be equal to V_O1+V_O2+…V_ON. The overall idea is that the parallel capacitor CP ensures that the excitation pulse source PUS can be transmitted when the main switch M is turned off, the main switch is turned on again by charging the energy storage capacitor with the aid of the excitation pulse source PUS, and the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch, so that the turn-off device can perform the operation of series connection again on the battery string connected in series with the turn-off device.

Referring to fig. 11, the aforementioned confusion of attempting to restart the system after the shutdown device SDN is shutdown under the instruction of shutdown lies in: the excitation pulse source PUS emitted by the turn-off control module RSD can no longer propagate smoothly in the closed loop and is mainly caused by the main switch being opened. As an alternative to the embodiment of fig. 10, an alternative approach to addressing the propagation of the excitation pulse source in the closed loop is: the turn-off device SDN is configured with a normally open parallel switch MP connected between a first terminal and a second terminal of the main switch M. Normally-open (Normally-ON) parallel switch MP defaults to being in an ON state if it is not actively controlling its ON or off state under normal conditions. The types of devices that can be used for the normally-on parallel switch MP are, for example, a junction field effect transistor JFET, the drains and sources of which are respectively considered as first and second terminals and which can be interchanged. The control terminal G of the normally-open parallel switch MP is connected to the control terminal G of the main switch M, and the first terminal and the second terminal of the normally-open parallel switch MP are correspondingly connected to the first terminal and the second terminal of the main switch, respectively. After the turn-off device SDN performs the turn-off operation and turns off the main switch M, the normally-open parallel switch enters a default on state. Conversely, if the energy storage capacitor is charged to cause a potential difference between the first terminal or the second terminal of the normally-open parallel switch and the gate control terminal, the normally-open parallel switch enters a cut-off state. After the turn-off device performs the turn-off operation and closes the main switch M, the normally-open parallel switch MP entering the on-state provides the on-path for the excitation pulse source PUS to propagate on the power line in the present application. When the turn-off control module RSD controls the turn-off device to be in a normal on state, for example, when it is ensured that the turn-off device SDN and the battery string are connected in series, it is necessary to send a driving pulse source PUS to the turn-off device SDN uninterruptedly or at least intermittently or periodically, and at a stage when the main switch M is turned on because the potential of the energy storage capacitor C1 reaches the on threshold voltage of the main switch due to charging of the pulse signal, in order to avoid interference between the main switch and the normally-open parallel switch, the charged potential of the energy storage capacitor C1 is also used as a pinch-off voltage to control the normally-open parallel switch MP in the category of junction field effect transistors to be turned off. The overall idea is that the normally-open parallel switch ensures that the excitation pulse source PUS can be transmitted when the main switch M is turned off, the main switch is enabled to be turned on again by charging the energy storage capacitor through the excitation pulse source PUS, and the condition that the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch is met, so that the turn-off device can execute the operation of series connection again on the battery string connected with the turn-off device in series. It should be noted that in some optional but non-necessary embodiments, the turn-off instruction causes the energy storage capacitor to gradually power down, the main switch M is turned off in advance in the power down process of the energy storage capacitor because the potential cannot reach the turn-on threshold voltage of the main switch, and at this time, the normally-open parallel switch MP is clamped in the turn-off region because the charge of the energy storage capacitor is not yet zero, until the power down of the energy storage capacitor is ended, the gate-source voltage of the normally-open parallel switch MP cannot be affected any more, so that the parallel switch enters the default turn-on state.

With reference to fig. 12, by modifying the parallel shutdown system for photovoltaic modules mentioned above, in particular in the embodiments of fig. 2 to 11, it comprises: the system comprises a shutdown control module RSD, a plurality of shutdown devices SD1-SDN and a plurality of series-connected photovoltaic modules PV1-PVN, wherein each photovoltaic module is provided with one shutdown device, and the photovoltaic modules are connected in series to form a battery string. The shutdown device is used for shutting down the photovoltaic component corresponding to the shutdown device and removing the photovoltaic component from the battery string, or the shutdown device is used for restoring the photovoltaic component corresponding to the shutdown device from a shutdown state to a serial connection state of the connected battery string. In an alternative embodiment, the shutdown control module RSD stops delivering the periodic excitation pulse source PUS to each shutdown device SD1-SDN upon receiving the shutdown command to notify the plurality of shutdown devices SD1-SDN to perform the shutdown operation to shut down the corresponding photovoltaic modules PV 1-PVN. Or when the shutdown control module RSD receives the start-up command, it will continue to deliver again the periodic excitation pulse source PUS to each shutdown device SD1-SDN to inform the plurality of shutdown devices to perform the turn-on operation to restore the respective corresponding photovoltaic module PV1-PVN from the off-state to the series-connected state.

With reference to fig. 12, by modifying the parallel shutdown system for photovoltaic modules mentioned above, in particular in the embodiments of fig. 2-11, each shutdown device, such as an SDN, comprises a main switch M for switching off or on between its input and output, the main switch M having a first terminal, a second terminal and a control terminal. The main switch M is connected between the first input terminal N1 and the first output terminal O1 for switching the first input terminal N1 and the first output terminal O1 off or on, and the main switch M is connected between the second input terminal N2 and the second output terminal O2 for switching the second input terminal N2 and the second output terminal O2 on. The shutdown device SDN comprises an inductor LS coupled to its output, such as the second output O2 or the first output O1, by a power line. Coupling element T₃The above first coupling transformer can be replaced and the coupling element mainly comprises an inductor LS. One end of the inductor LS is connected to the first terminal of the main switch M at the second output terminal O2 of the two output terminals, or one end of the inductor LS is connected to the first terminal of the main switch M at the first output terminal O1 of the two output terminals. The opposite end of inductor LS is connected to the anode of a steering diode D2 and the cathode of steering diode D2 is coupled to the control terminal of main switch M. The inductor LS is used to extract the excitation pulse source PUS loaded on the power line, and the induced excitation pulse source PUS charges the energy storage capacitor C1 connected between the control terminal and the first terminal of the main switch via the steering diode D2. When the potential of the energy storage capacitor C1 reaches the on threshold voltage of the main switch, the main switch M is turned on, otherwise, the main switch M is turned off.

With reference to fig. 12, by modifying the parallel shutdown system for photovoltaic modules mentioned above, in particular in the embodiments of fig. 2 to 11: the turn-off device SDN comprises two inputs N1-N2 connected to the positive and negative poles of the photovoltaic module respectively and two outputs O1-O2 connected in series with other turn-off devicesA bypass diode DP is arranged between the output ends O1-O2, and when the photovoltaic module PVN is turned off, the bypass diode DP provides a conduction path between the two output ends O1-O2 of the turn-off device SDN corresponding to the turned-off photovoltaic module. In an alternative embodiment, a parallel resistor R1 connected in parallel with the energy storage capacitor C is further provided between the control terminal and the first terminal of the main switch. In an alternative embodiment an anti-series connected zener diode Z1-Z2 connected in parallel with the energy storage capacitor C is also provided between the control terminal and the first terminal of the main switch. In an alternative embodiment, the turn-off device SDN comprises a parallel capacitor CP connected between the first terminal and the second terminal of the main switch, as may be seen in fig. 10 and 12, and after the turn-off operation is performed by the turn-off device SDN and the main switch is closed, a conduction path is provided by the parallel capacitor CP connected in parallel with the main switch M for the excitation pulse source to propagate around the main switch. In an alternative embodiment, the turn-off device SDN further includes a normally-open parallel switch MP connected between the first terminal and the second terminal of the main switch, as shown in fig. 11 and 12, wherein a control terminal of the normally-open parallel switch MP is connected to a control terminal of the main switch M, and after the turn-off device M performs the turn-off operation, the normally-open parallel switch MP entering the on state provides a conduction path through which the excitation pulse source PUS propagates by bypassing the main switch; and when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch M to switch on the main switch, the potential of the energy storage capacitor C1 also controls the normally-open parallel switch MP to be switched off. Note that all of the features possessed by and described in relation to the various embodiments of fig. 2-7 and fig. 10-11 may also be applied to the embodiment set forth in fig. 12. Coupling element T₃Instead of the above first coupling transformer, the inductor LS replaces the primary winding of the first coupling transformer. The inductor LS may be arranged between the second output terminal of the previous-stage turn-off device and the first output terminal of the adjacent subsequent-stage turn-off device, or the inductor LS may be arranged between the first output terminal of the first-stage turn-off device and the bus bar LA, or even the inductor LS may be arranged between the second output terminal of the last-stage turn-off device and the bus bar LB.

While the present invention has been described with reference to the preferred embodiments and illustrative embodiments, it is to be understood that the invention as described is not limited to the disclosed embodiments. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims of the present application should be considered to be within the intent and scope of the present invention.

Claims (28)

1. A parallel shutdown system for a photovoltaic module, comprising:

at least one turn-off control module;

the photovoltaic module comprises a plurality of turn-off devices and a plurality of photovoltaic modules, wherein each photovoltaic module is provided with one turn-off device;

a plurality of photovoltaic modules are connected in series to form a battery pack string;

each turn-off device is used for turning off the photovoltaic component corresponding to the turn-off device to remove the photovoltaic component from the battery string or restoring the photovoltaic component corresponding to the turn-off device from a turn-off state to a series connection state of connecting the photovoltaic components into the battery string;

when the turn-off control module receives a turn-off command, the turn-off control module stops transmitting a periodic excitation pulse source to each turn-off device to inform the plurality of turn-off devices to execute turn-off operation so as to turn off the corresponding photovoltaic assemblies; or

When the turn-off control module receives a starting command, the turn-off control module transmits periodic excitation pulse sources to the turn-off devices again to inform the turn-off devices to execute turn-on operation so as to restore the corresponding photovoltaic assemblies from the turn-off state to the serial connection state;

each turn-off device comprises a group of input ends respectively connected to the positive electrode and the negative electrode of the photovoltaic assembly and a group of output ends connected with other turn-off devices in series, and a bypass diode is arranged between the group of output ends of each turn-off device;

when the photovoltaic component is turned off, the bypass diode provides a conduction path between a group of output ends of the turn-off device corresponding to the turned-off photovoltaic component.

2. A parallel shutdown system for photovoltaic modules as claimed in claim 1 wherein:

each turn-off device comprises a main switch for switching off or on between an input and an output thereof, the main switch having a first terminal, a second terminal and a control terminal;

each turn-off device comprises a first coupling transformer coupled to the output end of the turn-off device through a power line, and a primary winding of the first coupling transformer and a first terminal of the main switch are connected to one of a group of output ends;

the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on the power line;

the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode;

when the potential of the energy storage capacitor reaches the conducting threshold voltage of the main switch, the main switch is switched on, otherwise, the main switch is switched off.

3. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

the main switch is a power MOSFET and the first, second and control terminals are a source, a drain and a gate, respectively; or

The main switch is an IGBT and the first, second and control terminals are an emitter, a collector and a gate, respectively.

4. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

and a parallel resistor connected in parallel with the energy storage capacitor is also arranged between the control terminal and the first terminal of the main switch.

5. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are further arranged between the control terminal and the first terminal of the main switch.

6. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to the control terminal of the main switch through the steering diode;

the dotted terminal is connected to the anode of the steering diode and the control terminal of the main switch is connected to the cathode of the steering diode.

7. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to a first node through a first capacitor;

a first diode is connected between the synonym end of the secondary winding of the first coupling transformer and the first node;

the anode of the first diode is connected to the synonym terminal of the secondary winding of the first coupling transformer, and the cathode is connected to the first node;

the first node is coupled to the anode of the steering diode and the control terminal of the main switch is coupled to the cathode of the steering diode.

8. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

the stage that the shutdown device does not execute shutdown operation and sets the photovoltaic module corresponding to the shutdown device to be connected into the battery string, and an excitation pulse source sent by the shutdown control module has a first logic state;

when receiving a turn-off command, the turn-off control module firstly inverts an excitation pulse source transmitted to the turn-off device from a first logic state to a second logic state with opposite polarity so as to inform the turn-off device to immediately short-circuit the control terminal and the first terminal of the main switch so as to rapidly turn off the main switch.

9. A parallel shutdown system for photovoltaic modules as claimed in claim 8 wherein:

the winding direction of one auxiliary winding of the first coupling transformer is opposite to that of the secondary winding;

the different name end of the auxiliary winding of the first coupling transformer is connected to the base electrode and the same name end of an NPN bipolar transistor, and the emitter electrode of the NPN bipolar transistor is connected to the first terminal of the main switch;

the collector of the NPN bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the NPN bipolar transistor to be conducted when inducing the excitation pulse source of the second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch.

10. A parallel shutdown system for photovoltaic modules as claimed in claim 8 wherein:

the winding direction of one auxiliary winding of the first coupling transformer is the same as that of the secondary winding;

the homonymous terminal of the auxiliary winding of the first coupling transformer is connected to the base electrode and the synonym terminal of a PNP bipolar transistor and the emitter electrode of the PNP bipolar transistor through a reversely connected second diode, and the emitter electrode of the PNP bipolar transistor is connected to the first terminal of the main switch;

the collector of the PNP bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the PNP bipolar transistor to be conducted when inducing an excitation pulse source of a second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch;

the anode of the second diode is connected to the base of the PNP bipolar transistor and the cathode is connected to the dotted terminal of the auxiliary winding.

11. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

the turn-off device comprises a parallel capacitance connected between the first and second terminals of the main switch;

after the turn-off device performs the turn-off operation and closes the main switch, a parallel capacitor connected in parallel with the main switch provides a conduction path through which the excitation pulse source propagates bypassing the main switch.

12. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

the turn-off device comprises a normally-open parallel switch connected between a first terminal and a second terminal of the main switch, a control terminal of the normally-open parallel switch being connected to a control terminal of the main switch;

after the turn-off device executes turn-off operation and closes the main switch, the normally-open parallel switch entering the conducting state provides a conducting path for the excitation pulse source to propagate by bypassing the main switch; and

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch to switch on the main switch, the potential of the energy storage capacitor also controls the normally-open parallel switch to be switched off.

13. A parallel shutdown system for photovoltaic modules as claimed in claim 2 wherein:

and replacing the primary winding and the secondary winding of the first coupling transformer by the primary winding and the secondary winding of one transformer.

14. A method for restarting a parallel shutdown system for photovoltaic modules after shutdown, based on claim 1, wherein:

each turn-off device comprises a main switch for switching off or on between an input and an output thereof, the main switch having a first terminal, a second terminal and a control terminal;

each turn-off device further comprises a first coupling transformer coupled to its output terminal via a power line, the primary winding of the first coupling transformer being connected to the first terminal of the main switch at one of a set of output terminals;

the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on the power line;

the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode;

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch, the main switch is switched on, otherwise, the main switch is switched off;

the method comprises the following steps:

when receiving a starting command, the turn-off control module transmits a periodic excitation pulse source to the turn-off device through the power line again so as to charge the energy storage capacitor until the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch, so as to trigger the turn-off device to execute conduction operation, and thus the corresponding battery assembly is recovered to a series connection state from a turn-off state.

15. The method of claim 14, wherein:

the turn-off device comprises a parallel capacitance connected between the first and second terminals of the main switch;

after the turn-off device performs turn-off operation and closes the main switch, the excitation pulse source is stopped to cause charge loss of the energy storage capacitor and cannot reach the conduction threshold voltage of the main switch, and at this stage, a parallel capacitor connected in parallel with the main switch provides a conduction path for the excitation pulse source to propagate by bypassing the main switch.

16. The method of claim 14, wherein:

the turn-off device comprises a normally-open parallel switch connected between a first terminal and a second terminal of the main switch, a control terminal of the normally-open parallel switch being connected to a control terminal of the main switch;

after the turn-off device executes turn-off operation and closes the main switch, the excitation pulse source is stopped to cause the charge loss of the energy storage capacitor and cannot reach the conduction threshold voltage of the main switch, and at this stage, the normally-open parallel switch entering the conduction state provides a conduction path for the excitation pulse source to propagate by bypassing the main switch; and

when the turn-off control module receives the starting command and charges the energy storage capacitor again to enable the potential of the energy storage capacitor to reach the conducting threshold voltage of the main switch to turn on the main switch, the potential of the energy storage capacitor also controls the normally-open parallel switch to be turned off.

17. The method of claim 14, wherein:

and a parallel resistor connected in parallel with the energy storage capacitor is also arranged between the control terminal and the first terminal of the main switch.

18. The method of claim 14, wherein:

a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are further arranged between the control terminal and the first terminal of the main switch.

19. The method of claim 14, wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to the control terminal of the main switch through the steering diode;

the dotted terminal is connected to the anode of the steering diode and the control terminal of the main switch is connected to the cathode of the steering diode.

20. The method of claim 14, wherein:

the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;

the dotted terminal of the secondary winding of the first coupling transformer is coupled to a first node through a first capacitor;

a first diode is connected between the synonym end of the secondary winding of the first coupling transformer and the first node;

the anode of the first diode is connected to the synonym terminal of the secondary winding of the first coupling transformer, and the cathode is connected to the first node;

the first node is coupled to the anode of the steering diode and the control terminal of the main switch is coupled to the cathode of the steering diode.

21. The method of claim 14, wherein:

the stage that the shutdown device does not execute shutdown operation and sets the photovoltaic module corresponding to the shutdown device to be connected into the battery string, and an excitation pulse source sent by the shutdown control module has a first logic state;

when receiving a turn-off command, the turn-off control module firstly inverts an excitation pulse source transmitted to the turn-off device from a first logic state to a second logic state with opposite polarity so as to inform the turn-off device to immediately short-circuit the control terminal and the first terminal of the main switch so as to rapidly turn off the main switch.

22. The method of claim 21, wherein:

the winding direction of one auxiliary winding of the first coupling transformer is opposite to that of the secondary winding;

the different name end of the auxiliary winding of the first coupling transformer is connected to the base electrode and the same name end of an NPN bipolar transistor, and the emitter electrode of the NPN bipolar transistor is connected to the first terminal of the main switch;

the collector of the NPN bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the NPN bipolar transistor to be conducted when inducing the excitation pulse source of the second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch.

23. The method of claim 21, wherein:

the winding direction of one auxiliary winding of the first coupling transformer is the same as that of the secondary winding;

the homonymous terminal of the auxiliary winding of the first coupling transformer is connected to the base electrode and the synonym terminal of a PNP bipolar transistor and the emitter electrode of the PNP bipolar transistor through a reversely connected second diode, and the emitter electrode of the PNP bipolar transistor is connected to the first terminal of the main switch;

the collector of the PNP bipolar transistor is connected to the control terminal of the main switch;

the auxiliary winding excites the PNP bipolar transistor to be conducted when inducing an excitation pulse source of a second logic state, and therefore the control terminal and the first terminal of the main switch are short-circuited to close the main switch;

the anode of the second diode is connected to the base of the PNP bipolar transistor and the cathode is connected to the dotted terminal of the auxiliary winding.

24. A parallel shutdown system for a photovoltaic module, comprising:

at least one turn-off control module;

the photovoltaic module comprises a plurality of turn-off devices and a plurality of photovoltaic modules, wherein each photovoltaic module is provided with one turn-off device;

a plurality of photovoltaic modules are connected in series to form a battery pack string;

each turn-off device is used for turning off the photovoltaic component corresponding to the turn-off device to remove the photovoltaic component from the battery string or restoring the photovoltaic component corresponding to the turn-off device from a turn-off state to a series connection state of connecting the photovoltaic components into the battery string;

when the turn-off control module receives a turn-off command, the turn-off control module stops transmitting a periodic excitation pulse source to each turn-off device to inform the plurality of turn-off devices to execute turn-off operation so as to turn off the corresponding photovoltaic assemblies; or

When the turn-off control module receives a starting command, the turn-off control module transmits periodic excitation pulse sources to the turn-off devices again to inform the turn-off devices to execute turn-on operation so as to restore the corresponding photovoltaic assemblies from the turn-off state to the serial connection state;

wherein:

each turn-off device comprises a main switch for switching off or on between an input and an output thereof, the main switch having a first terminal, a second terminal and a control terminal;

each turn-off device comprises an inductor coupled to its output terminal by a power line, one end of the inductor being connected to a first terminal of the main switch at one of a set of output terminals, the opposite end of the inductor being connected to the anode of a steering diode and the cathode of the steering diode being coupled to the control terminal of the main switch;

the inductor is used for extracting an excitation pulse source loaded on the power line;

the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through the steering diode;

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch, the main switch is switched on, otherwise, the main switch is switched off;

each turn-off device comprises a group of input ends respectively connected to the positive electrode and the negative electrode of the photovoltaic assembly and a group of output ends connected with other turn-off devices in series, and a bypass diode is arranged between the group of output ends of each turn-off device;

when the photovoltaic component is turned off, the bypass diode provides a conduction path between a group of output ends of the turn-off device corresponding to the turned-off photovoltaic component.

25. A parallel shutdown system for a photovoltaic module as set forth in claim 24 wherein:

and a parallel resistor connected in parallel with the energy storage capacitor is also arranged between the control terminal and the first terminal of the main switch.

26. A parallel shutdown system for a photovoltaic module as set forth in claim 24 wherein:

a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are further arranged between the control terminal and the first terminal of the main switch.

27. A parallel shutdown system for a photovoltaic module as set forth in claim 24 wherein:

the turn-off device comprises a parallel capacitance connected between the first and second terminals of the main switch;

after the turn-off device performs the turn-off operation and closes the main switch, a parallel capacitor connected in parallel with the main switch provides a conduction path through which the excitation pulse source propagates bypassing the main switch.

28. A parallel shutdown system for a photovoltaic module as set forth in claim 24 wherein:

the turn-off device comprises a normally-open parallel switch connected between a first terminal and a second terminal of the main switch, a control terminal of the normally-open parallel switch being connected to a control terminal of the main switch;

after the turn-off device executes turn-off operation and closes the main switch, the normally-open parallel switch entering the conducting state provides a conducting path for the excitation pulse source to propagate by bypassing the main switch; and

when the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch to switch on the main switch, the potential of the energy storage capacitor also controls the normally-open parallel switch to be switched off.

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