CN112820565B - Automatic transfer switching device control method and automatic transfer switching device - Google Patents

Abstract

The invention discloses a control method of an automatic transfer switch electric appliance. The automatic transfer switch electric appliance comprises an automatic transfer switch using a mechanical transfer switch and a power electronic device connected with the automatic transfer switch in parallel, wherein the power electronic device comprises a rectifying module and a power module and is used for providing electric energy for a load in a short time in the process of switching a power supply of the automatic transfer switch; in the process of switching the power supply of the automatic transfer switch, the following circulation current suppression control is performed on the power electronic device: and controlling the power electronic device by taking the sum of the currents of the various phases output by the power module of the power electronic device as a control target from the physical opening moment of the mechanical change-over switch until the current output by the mechanical change-over switch is 0. The invention also discloses an automatic change-over switch appliance. The invention can effectively inhibit the circulation current, thereby realizing the design optimization of the power electronic device.

Description

Automatic transfer switching device control method and automatic transfer switching device

Technical Field

The present invention relates to an Automatic Transfer Switching Equipment (ATSE).

Background

Automatic Transfer Switching Equipment (ATSE) is used primarily in emergency power systems to monitor power circuits and to transfer one or more load circuits from one power source to another. During the switching process, arcing occurs when the mechanical contacts separate, and the presence of arcing keeps the electrical circuit in a conductive state even though the mechanical contacts separate. If the arcing is not extinguished in time, a fault of short circuit of the two power supplies may be caused. In order to improve reliability, ATSE needs to design a conventional arc extinguishing chamber, and the switching speed of the control switch cannot be too fast, and the switching time is usually designed to be 30ms or more, which results in a longer power-off time of the load during switching.

For some devices with high requirements for continuous power supply, the conventional mechanical ATSE has difficulty meeting the working requirements. In order to meet the continuous power supply requirement of load equipment, 0-grade ATSE is preferably selected, and an online UPS or STS is generally adopted, but the products are high in price, large in size, high in maintenance cost, relatively large in loss during normal operation and special in regulation requirement on the load equipment.

In order to ensure the continuity of load power supply, quickly extinguish arcing and ensure the reliability of switching of two power supplies, the Chinese invention patent (with the publication number of CN105024450A and the publication number of 2015/11/4) discloses a double-power-supply automatic switching device which can meet the power supply requirement of a high-sensitive load and has high reliability.

In order to reduce the volume and reduce the cost, the automatic transfer switching device provided by the patent adopts a non-isolated circuit topology, a circulating current loop is formed by the rectifier bridge, the power module and the switch, circulating current components are not beneficial to load energy supply, but burden is increased on the power module by space, once circulating current is too large, faults such as overcurrent and overheating of the module are easily caused, potential safety hazards are formed, and the efficiency is reduced.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a control method of an automatic transfer switching device, which can effectively inhibit the circulation current and ensure the reliable work of a power electronic device, thereby realizing the small design capacity, small volume, low loss and high reliability of the power electronic device for supplying energy in a short time.

The invention specifically adopts the following technical scheme to solve the technical problems:

the control method of the automatic transfer switch electric appliance comprises an automatic transfer switch using a mechanical transfer switch and a power electronic device connected with the automatic transfer switch in parallel, wherein the power electronic device comprises a rectification module and a power module and is used for providing electric energy for a load in a short time in the process of switching a power supply of the automatic transfer switch; in the process of switching the power supply of the automatic transfer switch, the following circulation current suppression control is performed on the power electronic device: and controlling the power electronic device by taking the sum of the currents of the various phases output by the power module of the power electronic device as a control target from the physical opening moment of the mechanical change-over switch until the current output by the mechanical change-over switch is 0.

In one preferable embodiment, after the circulation suppression control is completed, the power electronic device is controlled with a goal that the voltage output by the power electronic device meets a load requirement, until the current output by the mechanical transfer switch appears again, or until the physical closing time of the mechanical transfer switch, or until a preset delay time is reached, the power electronic device stops outputting the load.

In a second preferred embodiment, after the circulation suppression control is completed, the power electronic device is controlled with the aim that the voltage output by the power electronic device meets the load requirement; when the current output through the mechanical change-over switch appears again, the power electronic device is controlled by taking the sum of the currents of all phases output by the power module of the power electronic device as a control target again, and the power electronic device stops outputting to the load until the physical closing time of the mechanical change-over switch.

Preferably, the power electronic device further includes a dc filter disposed between the rectifier module and the power module and an ac filter disposed behind the power module.

Further preferably, the power electronic device is PMW controlled by a double closed loop control method of a voltage outer loop and a current inner loop.

Still more preferably, in the process of controlling the power electronic device by taking the sum of the currents of the various phases output by the power module of the power electronic device as a control target, the load voltage is adjusted by taking the voltage output by the power electronic device as a target of meeting the load requirement, and a three-phase voltage command U is obtained_ref(ii) a Meanwhile, the sum of the currents of all phases output by a power module of the power electronic device is taken as 0 as a control target, and a circulating current restraining voltage instruction U is obtained through the regulation and control of a current controller_{h_ref}The power is controlled according to the circulation suppression voltage commandThe N-phase output potential of the electronic device is regulated, and other three-phase output potentials of the power electronic device are regulated along with the N-phase output potential so as to guarantee the interphase voltage difference and the three-phase voltage instruction U_refThe same is true.

According to the same inventive concept, the following technical scheme can be obtained:

an automatic transfer switch electric appliance comprises an automatic transfer switch using a mechanical transfer switch and a power electronic device connected with the automatic transfer switch in parallel, wherein the power electronic device is used for supplying electric energy to a load for a short time in the process of power supply switching of the automatic transfer switch; the automatic transfer switching equipment adopts the control method of any one of the technical schemes.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention can restrain the circulation in the arcing mode, and ensure the safety and reliability of the equipment;

2. the invention can adopt a circuit topology without isolation, and has low hardware cost, small volume and low loss.

Drawings

FIG. 1 is a schematic diagram of the basic principle of the present invention;

FIG. 2 is a schematic circuit diagram of an embodiment of an automatic transfer switching apparatus according to the present invention;

FIG. 3 is a schematic diagram illustrating the control principle of the mechanical transfer switch after physical opening;

FIG. 4 is a schematic flow chart of the algorithm of the circulation suppression algorithm;

FIG. 5 is a schematic diagram illustrating the control principle after the mechanical transfer switch is extinguished;

fig. 6 is a schematic diagram of a control principle of the mechanical transfer switch before physical closing in the specific embodiment.

Detailed Description

Aiming at the circulating current problem of the existing automatic change-over switch electric appliance with the short-time energy supply power electronic device in an arcing mode, the invention solves the idea that the effective inhibition of the circulating current is realized by reasonably controlling the output current of the power electronic device in the arcing mode (namely, the separation and the contact of a moving contact and a static contact of a mechanical change-over switch can realize the disconnection and the connection of a circuit where the moving contact and the static contact are positioned under the condition that the arcing exists between the moving contact and the static contact of the mechanical change-over switch in the process of switching a power supply), so as to ensure the reliable work of the power electronic device, thereby realizing the small design capacity, the small volume, the low loss and the high reliability of the short-time energy supply power electronic device.

Specifically, the automatic transfer switch electric appliance comprises an automatic transfer switch using a mechanical transfer switch and a power electronic device connected with the automatic transfer switch in parallel, wherein the power electronic device comprises a rectification module and a power module and is used for supplying electric energy to a load in a short time in the process of switching a power supply of the automatic transfer switch; in the process of switching the power supply of the automatic transfer switch, the following circulation current suppression control is performed on the power electronic device: and controlling the power electronic device by taking the sum of the currents of the various phases output by the power module of the power electronic device as a control target from the physical opening moment of the mechanical change-over switch until the current output by the mechanical change-over switch is 0.

The circulation current restraining control can effectively restrain the circulation current caused by arcing when the mechanical change-over switch is opened. After the circulation current suppression control is finished, the power electronic device is controlled by taking the voltage output by the power electronic device to meet the load requirement as a target until the current output by the mechanical change-over switch reappears, or until the physical switching-on time of the mechanical change-over switch, or until a preset delay time is reached, the power electronic device stops outputting the load.

In the above situation, the "current output by the mechanical transfer switch appears again" refers to reignition of an arc between a moving contact and a stationary contact, which are arcing at the time of physical opening of the mechanical transfer switch, or arcing due to air breakdown between the moving contact of the mechanical transfer switch and the stationary contact in another power circuit before another power circuit is connected, or current due to contact between the moving contact of the mechanical transfer switch and the stationary contact in another power circuit.

In the above case, "after the preset delay time is reached, the power electronic device stops outputting to the load", which means that, when it is determined that the load has recovered power supply after the power electronic device independently supplies power for the specified time, and the time that the subsequent mechanical transfer switch turns on another power supply is shorter than the maximum allowable power-off time for power supply to the load, the power electronic device can exit in advance and no output is performed.

However, in some special cases, the mechanical transfer switch may also generate a relatively strong arcing phenomenon at the closing moment, and when the moving contact and the stationary contact of the mechanical transfer switch are in contact, the moving contact may generate a bouncing phenomenon, and arcing occurs between the moving contact and the stationary contact, and this situation of the mechanical transfer switch may also cause the occurrence of a circulating current, and in order to solve this problem, the present invention provides the following further improvement schemes:

after the circulation current restraining control is finished, controlling the power electronic device by taking the voltage output by the power electronic device as a target to meet a load requirement; when the current output by the mechanical change-over switch occurs again, the power electronic device is controlled by taking the sum of the currents of all phases output by the power module of the power electronic device as 0 as a control target again until the physical switching-on time of the mechanical change-over switch (the physical switching-on time refers to that the moving contact is stably contacted with the fixed contact and no bounce phenomenon occurs any more), and the power electronic device stops outputting the load.

For the public understanding, the following takes the most common dual power conversion system as an example, and the technical solution of the present invention is described in detail with reference to the accompanying drawings:

fig. 1 shows a basic structure of a hybrid dual power transfer system employing an automatic transfer switching apparatus of the present invention, as shown in fig. 1, wherein the automatic transfer switching apparatus includes a dual power automatic transfer switch using a mechanical transfer switch and a power electronic device connected in parallel with the dual power automatic transfer switch; the output ends of two power sources S1 and S2 are respectively connected with an input branch of the power electronic device, the output end of the power source S1 connected with the input branch L1 is connected with the input end a of a mechanical change-over switch (single-pole double-throw), the output end of the power source S2 connected with the input branch L2 is connected with the input end c of the mechanical change-over switch (single-pole double-throw), the output end b of the mechanical change-over switch is connected with a load through the mechanical change-over switch output branch, the power source S1/S2 is connected with the power electronic device and the power electronic device output branch L3 through the input branch L1/L2, and the power electronic device output branch L3 is connected with the mechanical change-over switch output branch L4 and then is connected with the load; in the power electronic device of the present embodiment, in addition to the necessary input-side rectifier bridge, power module, and controller, a dc filter is connected between the rectifier bridge and the power module, and an ac filter is connected between the power module and the output branch L3.

In the conversion process of the mechanical change-over switch, the controller controls the power electronic device to actively regulate and control the electric arc generated on the mechanical change-over switch, so that the energy of the electric arc is attenuated until the electric arc is extinguished, and a circulating current is generated in the process; the controller regulates and controls the power electronic device to inhibit the circulation current, and the method can be divided into the following three stages:

in stage one, the output terminal b of the mechanical transfer switch is connected to the input terminal a of the mechanical transfer switch, and at this time, the power source S1 supplies power to the load, when the power supply S2 needs to be switched to supply power to the load, the mechanical change-over switch is switched off, and after the moving contact and the static contact are separated (because of the existence of arcing between the moving contact and the static contact, the moving contact and the static contact are still in a connected state electrically, and the invention is called as physical brake-off for distinction), and generating arcing, wherein an output branch L4 of the mechanical change-over switch is connected with a branch (a branch connected with points b and a) where the mechanical change-over switch generating the arcing current is located through an arcing current (which can be detected through a current transformer arranged between the point P and the mechanical change-over switch), then is connected to an input branch of the power electronic device, and forms a circulating loop through a rectifier bridge and a controlled and conducted power module to form a circulating loop I._h(ii) a At this stage, the controller controls the sum of the output currents of the output branch L3 of the power electronic device to be zero, so as to inhibit the circulation current;

in the second stage, in the conversion process of the mechanical change-over switch, after detecting that the first arcing current is zero, indicating that the arcing is extinguished; at this stage, the power electronic device does not control the output current of the output branch L3 any more, and only regulates and controls the output load voltage to supply power to the load;

and in the third stage, when the mechanical change-over switch starts to be switched on to the other power supply S2, arcing is generated between the moving contact and the fixed contact of the mechanical change-over switch, after arcing current is detected, the controller controls the sum of the output currents of the output branch L3 of the power electronic device to be zero until the whole mechanical change-over process is completed (namely the mechanical change-over switch reaches the physical switching-on moment), and the power electronic device stops supplying energy to the load and simultaneously stops controlling the output current of the output branch L3.

The three possible causes of arcing at the stage are two, and before the power supply S2 is switched on, air between the movable contact of the mechanical transfer switch and the fixed contact in the loop where the power supply S2 is located is broken down to cause arcing, or after the movable contact of the mechanical transfer switch is connected with the fixed contact in the loop of the power supply S2, arcing is caused by bouncing of the movable contact.

Fig. 2 shows a specific circuit of the automatic transfer switching apparatus in a three-phase four-wire system, as shown in fig. 2, which mainly includes a power source S1, a power source S2, a mechanical automatic transfer switch ATS, power electronics, and a controller for controlling the power electronics. The power supply S1 and the power supply S2 can be used as a common power supply and a standby power supply, respectively. The output end of the power electronic device is connected with a load, and the load is connected with a power supply through an ATS. The controller is used for processing each information obtained by sampling, performing current and voltage control operation through a set algorithm, and finally generating a PWM signal through four-bridge arm modulation. In the process of switching the power supply of the automatic transfer switch, the power electronic device is specifically controlled according to the following method so as to inhibit the circulation current generated in the process of switching the power supply of the automatic transfer switch:

in the first stage, a power supply S1 supplies power to a load through a mechanical change-over switch, when the power supply S2 needs to be switched to supply power to the load, the ATS is disconnected, and the machinery in a power supply loop of the power supply S1 is disconnectedAfter the moving contact and the static contact of the formula change-over switch are separated, arcing (namely between A and A1) is generated between the moving contact and the static contact, and a loop current loop is formed by the power electronic device and a branch circuit where the mechanical change-over switch generating arcing is located, as shown in fig. 3, if arcing exists between the moving contact and the static contact of the mechanical change-over switch of the A phase after the mechanical change-over switch is disconnected, any phase of the power S1 or S2, if the phase is the A phase of the power S1, passes through the input branch circuit L_1AThe rectifier bridge is connected with a direct current bus, and when the upper bridge arm of the phase A of the power module is controlled to be conducted, current flows into the phase A output branch circuit L_3AThen via the branch L where the mechanical change-over switch is located_4AThe branch where the mechanical change-over switch generating arcing of the phase A is located flows into the branch L_5AForming a circulation flow;

or arcing occurs between the moving contact and the fixed contact of the C-phase mechanical change-over switch (namely, arcing occurs between C and C1), and L_5CAnd L_1CThe branch circuit and the power electronic device form a circulating current branch circuit; namely, a loop current exists between the output of the A/B/C phase power supply and a branch where the A/B/C phase mechanical change-over switch is located;

or a circulating current exists among phases, as shown in fig. 2, when the moving contact and the fixed contact of the C-phase mechanical change-over switch of the power supply S1 are separated, the a-phase power supply output of the power supply S1, the branch where the C-phase mechanical change-over switch generating arcing is located, and the power electronic device form a circulating current loop;

or a circulating current exists between two power supplies, such as an output branch L of the power supply S1_1AL of a mechanical change-over switch for generating arcing_6CThe branch circuit and the power electronic device form a circulation loop;

in short, when it is required that a certain phase bridge arm in A, B, C three phases is controlled to be conducted, arcing exists between a moving contact and a static contact of a mechanical change-over switch corresponding to the phase, and a circulating loop can be formed between the arcing and other phases of the rectified input or another power output branch circuit to form a circulating loop; meanwhile, the direction of the circulating current is related to the controlled-conduction bridge arm of the power module, for example, comparing fig. 2 and fig. 3, the current direction of the circulating current branch when the upper bridge arm of the phase a of the power module is controlled to be conducted and the C-phase mechanical transfer switch is disconnected is opposite to the current direction of the circulating current branch when the lower bridge arm of the phase a of the power module is controlled to be conducted and the C-phase mechanical transfer switch is disconnected.

As shown in fig. 4, the method for controlling the circulating current suppression at this stage is that the power electronic device controls the load voltage U through a voltage outer loop and a current inner loop in a double closed loop manner_cAdjusting to obtain three-phase voltage command U_ref(ii) a Meanwhile, 4 paths of output current I in the output branch L3 are used for restraining the circulation current_LThe sum is controlled to be 0, and a circulating current suppression voltage instruction U is obtained through the regulation and control of a current controller_{h_ref}Outputting a point P to the N-phase bridge arm according to the instruction_NThe potential is regulated and controlled, and the potential of output points of other three-phase bridge arms follows P_NRegulation and control to ensure phase-to-phase pressure difference and instruction U_refAnd the circulating current can be restrained, and meanwhile, the three-phase voltage energy supply control is not influenced.

Wherein the load voltage U_cIncluding P_APoint sum P_NPhase a load voltage U between points_{c_AN}、P_BPoint sum P_NB-phase load voltage U between points_{c_BN}、P_CPoint sum P_NC-phase load voltage U between points_{c_CN}Phase voltage command U of each phase_refIncluding U corresponding to each phase_{ref_AN}、U_{ref_BN}、U_{ref_CN}The output branch L3 comprises output branches L corresponding to the phases_3A、L_3B、L_3C、L_3NOutput current I_LComprises 4 output currents I_LA、I_LB、I_LC、I_LN。

As shown in the figure, the reference points of the output voltages of the bridge arms are all negative bus voltage N_dcPoint potential, so the duty ratio of each phase of bridge arm can be expressed as

Wherein x represents AN, BN, CN. And converting the Clark change into an alpha beta static coordinate system, removing zero vectors, performing Clark inverse transformation to convert standard sinusoidal vectors, and comparing to obtain the maximum duty ratio and the minimum duty ratio.

According to vector derivation:

after the duty ratio of the N bridge arms is obtained, other three-phase bridge arms are according to T_A＝T_N+T_ANAnd in the form of the PWM control signal, summing is carried out to obtain the duty ratio of each phase of bridge arm, and the duty ratio is output to generate the PWM control signal.

And in the second stage, in the conversion process of the mechanical change-over switch, after the arc current is detected to be zero, the arc can be considered to be extinguished, and a circulating loop cannot be formed. In order to avoid that the circulation suppression algorithm gives zero-sequence component bias due to various disturbance factors such as sampling errors and interference and the like to influence normal energy supply output, as shown in fig. 5, the power electronic device does not perform the circulation suppression algorithm any more, and only regulates and controls the P-point load voltage through the output branch line L3 to supply energy to the load.

And step three, when the mechanical change-over switch starts to be powered on S2, current appearing in the mechanical change-over switch is detected, as shown in fig. 6, the circulation current suppression algorithm shown in fig. 4 is continued, circulation current is suppressed by controlling the sum of the currents of all the phases of the output branch L3 to be zero, and the circulation current suppression algorithm is stopped when the power electronic device stops supplying power to the load until the whole mechanical change-over process is completed (namely the mechanical change-over switch reaches the physical closing moment).

The sum of the output currents is the sum of the currents in the capacitors Ca, Cb, Cc of each phase, the sum of the currents of the phases of the load, and the circulating current.

Since the sum of the currents in the capacitors Ca, Cb, Cc of the respective phases and the sum of the currents in the respective phases of the load are 0 in a normal state (a state where no leakage occurs or the like), the circulating current can be set to 0 by simply controlling the sum of the bridge arm output currents to 0.

In conclusion, by adopting the control method of the invention, the circulation current suppression in the whole process of breaking, converting and connecting the mechanical change-over switch is realized, the reliability of the equipment is ensured, the output pressure of the power module is reduced, the efficiency is improved, meanwhile, the electric energy is provided for the load during the switch conversion period, and the power-off time of the load is shortened.

Claims (7)

1. The control method of the automatic transfer switch electric appliance comprises an automatic transfer switch using a mechanical transfer switch and a power electronic device connected with the automatic transfer switch in parallel, wherein the power electronic device comprises a rectification module and a power module and is used for providing electric energy for a load in a short time in the process of switching a power supply of the automatic transfer switch; the power electronic device is characterized in that the following circulation current suppression control is performed on the power electronic device in the process of switching the power supply of the automatic change-over switch: and controlling the power electronic device by taking the sum of the currents of the various phases output by the power module of the power electronic device as a control target from the physical opening moment of the mechanical change-over switch until the current output by the mechanical change-over switch is 0.

2. The method for controlling an automatic transfer switching apparatus according to claim 1, wherein after the control of the circulating current suppression is completed, the power electronic apparatus is controlled with a goal that the voltage output from the power electronic apparatus satisfies a load requirement until the current output from the mechanical transfer switch reappears, or until a physical closing time of the mechanical transfer switch, or until a preset delay time is reached, and the power electronic apparatus stops outputting the load.

3. The method for controlling an automatic transfer switching apparatus according to claim 1, wherein the power electronic device is controlled with a goal that a voltage output from the power electronic device satisfies a load requirement after the control of the circulating current is completed; when the current output through the mechanical change-over switch appears again, the power electronic device is controlled by taking the sum of the currents of all phases output by the power module of the power electronic device as a control target again, and the power electronic device stops outputting to the load until the physical closing time of the mechanical change-over switch.

4. The method as claimed in claim 1, wherein the power electronic device further comprises a dc filter disposed between the rectifier module and the power module and an ac filter disposed behind the power module.

5. The control method of the automatic transfer switching apparatus according to claim 4, wherein the PMW control is performed on the power electronic device by a double closed loop control method of a voltage outer loop and a current inner loop.

6. The method for controlling an automatic transfer switching apparatus according to claim 5, wherein in the process of controlling the power electronic device with the sum of the currents of the respective phases output from the power modules of the power electronic device as 0 as a control target, the load voltage is adjusted with the voltage output from the power electronic device as a target to meet the load requirement, and a three-phase voltage command U is obtained_ref(ii) a Meanwhile, the sum of the currents of all phases output by a power module of the power electronic device is taken as 0 as a control target, and a circulating current restraining voltage instruction U is obtained through the regulation and control of a current controller_{h_ref}And regulating and controlling the N-phase output potential of the power electronic device according to the circulating current suppression voltage instruction, and regulating and controlling other three-phase output potentials of the power electronic device along with the N-phase output potential so as to ensure the interphase voltage difference and the three-phase voltage instruction U_refThe same is true.

7. An automatic transfer switch electric appliance comprises an automatic transfer switch using a mechanical transfer switch and a power electronic device connected with the automatic transfer switch in parallel, wherein the power electronic device comprises a rectifying module and a power module and is used for supplying electric energy to a load for a short time in the process of switching a power supply of the automatic transfer switch; the automatic transfer switching apparatus is characterized in that the control method according to any one of claims 1 to 6 is used.

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