Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a parallel control device of a lithium ion battery pack.
The purpose of the invention is realized by the following technical scheme:
a parallel control device of a lithium ion battery pack comprises a first battery pack monitoring module, a second battery pack monitoring module, a main control module, a closed-loop feedback module and a power switch module;
a first battery pack monitoring module: the system comprises a main control module, a first battery pack, a second battery pack, a first battery pack, a second battery pack, a third battery pack, a fourth battery pack, a fifth battery pack, a sixth battery pack, a fifth battery pack, a sixth battery pack, a fifth battery pack, a sixth battery pack, a fourth battery pack;
a second battery pack monitoring module: the system comprises a main control module, a first battery pack, a second battery pack, a first battery pack and a second battery pack, wherein the main control module is used for sampling the total pressure of the second battery pack, the current between the first battery pack and the second battery pack and the temperature of each monitoring node in the second battery pack and transmitting the total pressure, the current and the temperature to the main control module in a bus communication mode;
a main control module: comparing the total pressure of the first battery pack and the total pressure of the second battery pack, and sending a reference voltage instruction to a closed-loop feedback module;
a closed loop feedback module: regulating the voltage output to the power switch module according to the reference voltage and the feedback voltage by combining a zero pole compensation network;
a power switch module: and adjusting the charging current between the first battery pack and the second battery pack according to the voltage output by the closed-loop feedback module.
The closed-loop feedback module comprises a first operational amplifier unit, a second operational amplifier unit, a feedback resistor R1, a feedback resistor R2, a first pole-zero compensation network and a second pole-zero compensation network;
the main control module is provided with two paths of outputs, the first path of output is connected to the equidirectional input end of the first operational amplifier unit, the second path of output is connected to the equidirectional input end of the second operational amplifier unit, one end of the feedback resistor R1 is connected to the reverse input end of the first operational amplifier unit, and the other end of the feedback resistor R1 is connected with the positive output end of the first battery pack; one end of the feedback resistor R2 is connected to the reverse input end of the second operational amplifier unit, and the other end of the feedback resistor R2 is connected to the positive output end of the second battery pack;
the first pole-zero compensation network is formed by connecting a resistor R3 and a capacitor C1 in parallel, is connected between the reverse input end and the output end of the first operational amplifier unit and provides pole-zero compensation for the closed-loop feedback module;
the second pole-zero compensation network is formed by connecting a resistor R4 and a capacitor C2 in parallel, is connected between the reverse input end and the output end of the second operational amplifier unit and provides pole-zero compensation for the closed-loop feedback module;
the ground of the first operational amplifier unit is connected to the anode of the first battery pack, and the ground of the second operational amplifier unit is connected to the anode of the second battery pack.
When the total pressure of the second battery pack is greater than that of the first battery pack, the first output of the main control module is the maximum charging current R1 which can be accepted by the first battery pack, and the second output is 0;
when the total pressure of the first battery pack is greater than that of the second battery pack, the second output of the main control module is the maximum charging current R2 which can be received by the second battery pack, and the first output is 0.
A first fuse is provided between the positive electrode of the first battery pack and the resistor R1, and a second fuse is provided between the positive electrode of the second battery pack and the resistor R2.
The power switch module comprises a switch tube K1 and a switch tube K2;
the grid of switch tube K1 is connected to the output of first fortune unit of putting, and the grid of switch tube K2 is connected to the output of second fortune unit of putting, and the source electrode of switch tube K1 is connected with the reverse input end of first fortune unit of putting, and the drain electrode of switch tube K1 is connected with the drain electrode of switch tube K2, and the source electrode of switch tube K2 is connected with the reverse input end of second fortune unit of putting.
The first battery pack monitoring module, the second battery pack monitoring module and the main control module are connected to a bus in a hanging mode in a communication mode, and a data transmission function can be achieved.
The positive electrode of the first battery pack is connected with the positive electrode of the second battery pack through a relay K3, and the first battery pack and the second battery pack are connected in parallel and then are connected with a load or a charger through a relay K4;
after charging and discharging between the first battery pack and the second battery pack are completed, the main control module controls the relay K3 to be switched on, the switch tube K1 and the switch tube K2 to be switched off, the relay K4 is switched on, the first battery pack and the second battery pack which are connected in parallel discharge to a load, or the charger charges the first battery pack and the second battery pack which are connected in parallel.
The first battery pack, thesecond battery pack 2 and the load or charger are grounded.
The main control module adopts a step current reduction mechanism, and the realization method is as follows:
the main control module receives the total pressure of the first battery pack and the total pressure of the second battery pack, and when the difference value between the total pressure of the first battery pack and the total pressure of the second battery pack is smaller than a set first differential pressure threshold value, the main control module sends a reference voltage command to reduce the current between the first battery pack and the second battery pack to 80% of an initial value; when the difference value between the total pressure of the first battery pack and the total pressure of the second battery pack is smaller than a set second differential pressure threshold value, reducing the current between the first battery pack and the second battery pack to 60% of the initial value by sending a reference voltage instruction; when the difference value between the total pressure of the first battery pack and the total pressure of the second battery pack is smaller than a set third pressure difference threshold value, the current between the first battery pack and the second battery pack is reduced to 40% of the initial value by sending a reference voltage instruction until the total pressure of the first battery pack is the same as the total pressure of the second battery pack, and charging and discharging between the first battery pack and the second battery pack are completed.
Compared with the prior art, the invention has the following advantages:
(1) the invention sets reference voltage through the main control module, controls the current flowing through the switching tube under the action of the closed-loop feedback module, and is beneficial to flexibly adjusting the maximum charging current acceptable by different lithium ion battery packs and improving the charging and discharging efficiency among the battery packs compared with the method of adopting a series power resistor mode and adopting a method of adjusting the grid source voltage of the switching tube to enable the switching tube to work in a constant current region in the prior art.
(2) The invention realizes the series-parallel connection function of a plurality of power resistors by utilizing the heating loss of the switching tube, can be applied to different battery packs without the differentiated design of current limiting among the battery packs for a plurality of lithium ion battery packs, and improves the universality to a great extent.
(3) According to the invention, the charging control strategy among the lithium ion battery packs is realized by monitoring the charging current in real time, and once the node temperature of the battery pack is monitored to be higher, the charging current is gradually reduced, so that the safety and the reliability can be effectively improved.
(4) The parallel control circuit has the advantages of simple structure, easy layout and wiring, small occupied volume, capability of secondarily improving the existing parallel control circuit, capability of realizing the adjustable current charging function among the lithium ion battery packs, minimum change, easiness in realization and low cost based on secondary improvement of the mature prior art.
(5) According to the invention, the switching tube works in a constant current region for large-current charging and works in a saturation region for constant-voltage charging, so that the voltage difference between the lithium ion battery packs is further reduced.
Detailed Description
As shown in fig. 1, the parallel control device of the lithium ion battery pack includes a first battery pack monitoring module 1, a second batterypack monitoring module 2, a main control module, a closed-loop feedback module, and a power switch module. The first battery pack monitoring module 1 samples the total pressure, the branch current (the current between the first battery pack and the second battery pack) and the node temperature of the first battery pack 1, the second batterypack monitoring module 2 samples the total pressure, the branch current and the node temperature of thesecond battery pack 2, the sampled data are uploaded to the main control module in a bus communication mode, and the main control module compares the total pressures of the two battery packs and sends a reference voltage instruction to the closed-loop feedback module.
The closed-loop feedback module comprises a first operational amplifier unit, a second operational amplifier unit, a feedback resistor R1, a feedback resistor R2, a first pole-zero compensation network and a second pole-zero compensation network; the main control module is provided with two paths of outputs, the first path of output is connected to the equidirectional input end of the first operational amplifier unit, the second path of output is connected to the equidirectional input end of the second operational amplifier unit, one end of the feedback resistor R1 is connected to the reverse input end of the first operational amplifier unit, and the other end of the feedback resistor R1 is connected with the positive output end of the first battery pack; one end of the feedback resistor R2 is connected to the reverse input end of the second operational amplifier unit, and the other end of the feedback resistor R2 is connected to the positive output end of the second battery pack; the first pole-zero compensation network is formed by connecting a resistor R3 and a capacitor C1 in parallel, is connected between the reverse input end and the output end of the first operational amplifier unit and provides pole-zero compensation for the closed-loop feedback module; the second pole-zero compensation network is formed by connecting a resistor R4 and a capacitor C2 in parallel, is connected between the reverse input end and the output end of the second operational amplifier unit and provides pole-zero compensation for the closed-loop feedback module; the ground of the first operational amplifier unit is connected to the anode of the first battery pack, and the ground of the second operational amplifier unit is connected to the anode of the second battery pack.
A first fuse is provided between the positive electrode of the first battery pack and the resistor R1, and a second fuse is provided between the positive electrode of the second battery pack and the resistor R2. The protection circuit is used for protecting the battery pack and avoiding charging and discharging overcurrent.
The power switch module comprises a switch tube K1 and a switch tube K2; the grid of switch tube K1 is connected to the output of first fortune unit of putting, and the grid of switch tube K2 is connected to the output of second fortune unit of putting, and the source electrode of switch tube K1 is connected with the reverse input end of first fortune unit of putting, and the drain electrode of switch tube K1 is connected with the drain electrode of switch tube K2, and the source electrode of switch tube K2 is connected with the reverse input end of second fortune unit of putting.
The specific reference voltage command is as follows: if the total voltage of the first battery pack 1 is greater than the total voltage of thesecond battery pack 2, the main control module outputs a reference voltage Vref1(Vref1 is 0) to the unidirectional input end of the first operational amplifier unit, and simultaneously outputs a reference voltage Vref2(Vref2 is the maximum charging current acceptable for the battery pack 2R 2) to the unidirectional input end of the second operational amplifier unit. The voltage on the inverting input end sampling resistor R1 of the first operational amplifier unit compensates the zero pole through the resistor R3 and the capacitor C1 in the first PI network (first zero pole compensation network), adjusts the output voltage of the first operational amplifier unit, namely the gate-source voltage of the switch tube K1, and controls the switch tube K1 to be switched off. Meanwhile, the voltage on the reverse input end sampling resistor R2 of the second operational amplifier unit compensates a zero pole through a resistor R4 and a capacitor C2 in a second PI network (a second zero pole compensation network), the output voltage of the second operational amplifier unit, namely the gate-source voltage of the switching tube K2, is adjusted, and the current value flowing through the switching tube K2 is controlled; if the total voltage of thesecond battery pack 2 is greater than the total voltage of the first battery pack 1, the main control module outputs a reference voltage Vref2(Vref2 is 0) to the unidirectional input terminal of the second operational amplifier unit, and simultaneously outputs a reference voltage Vref1(Vref1 is the maximum charging current acceptable for the battery pack 1R 1) to the unidirectional input terminal of the first operational amplifier unit. The voltage on the inverting input end sampling resistor R2 of the second operational amplifier unit compensates the zero pole through the resistor R4 and the capacitor C2 in the second PI network, adjusts the output voltage of the second operational amplifier unit, namely the gate-source voltage of the switch tube K2, and controls the switch tube K2 to be switched off. Meanwhile, the voltage on the reverse input end sampling resistor R1 of the first operational amplifier unit compensates a zero pole through the resistor R3 and the capacitor C1 in the first PI network, the output voltage of the first operational amplifier unit, namely the gate-source voltage of the switching tube K1, is adjusted, and the current value flowing through the switching tube K1 is controlled.
The main control module is designed with a three-level temperature alarm mechanism, after the first battery pack monitoring module and the second battery pack monitoring module upload node temperature data to the bus, the main control module receives the node temperature data, compares the received data with a set threshold value 1, and sets the reference of the current between the first battery pack and the second battery pack to 80% of the initial value if the set threshold value 1 is reached; if theset threshold value 2 is reached, setting the reference of the current between the first battery pack and the second battery pack to be 60% of the initial value; if the set threshold value 3 is reached, the charging between the battery packs is stopped.
The main control module adopts a step current reduction mechanism, and the realization method is as follows:
the main control module receives the total pressure of the first battery pack and the total pressure of the second battery pack, and when the difference value between the total pressure of the first battery pack and the total pressure of the second battery pack is smaller than a set first differential pressure threshold value, the main control module sends a reference voltage command to reduce the current between the first battery pack and the second battery pack to 80% of an initial value; when the difference value between the total pressure of the first battery pack and the total pressure of the second battery pack is smaller than a set second differential pressure threshold value, reducing the current between the first battery pack and the second battery pack to 60% of the initial value by sending a reference voltage instruction; when the difference value between the total pressure of the first battery pack and the total pressure of the second battery pack is smaller than a set third pressure difference threshold value, the current between the first battery pack and the second battery pack is reduced to 40% of the initial value by sending a reference voltage instruction until the total pressure of the first battery pack is the same as the total pressure of the second battery pack, and charging and discharging between the first battery pack and the second battery pack are completed.
The positive pole of the first battery pack is connected with the positive pole of the second battery pack through a relay K3, and the first battery pack and the second battery pack are connected in parallel and then are connected with a load or a charger through a relay K4.
The first battery pack and the second battery pack which are connected in parallel with the main control module discharge to the load, or the charger charges the first battery pack and the second battery pack which are connected in parallel with each other.
The first battery pack, thesecond battery pack 2 and the load or charger are grounded.
After the charging and discharging between the first battery pack and the second battery pack are completed, the main control module controls the relay K3 to be switched on, the switch tube K1 and the switch tube K2 to be switched off, and the relay K4 to be switched on after receiving a communication command of a load or a battery charger, so that the discharging to the load is realized, or the battery charger charges the battery pack.
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.