CN116865316A - A modular energy storage bidirectional converter - Google Patents

Abstract

The invention provides a modular energy storage bidirectional converter, which includes a number of battery units arranged on a battery rack in an electrical cabinet. The electrical cabinet is also provided with a discharge load, a detection unit, and a control unit. The discharge load It is used to connect each battery unit in turn for discharge testing. The detection unit and the discharge load are connected to each battery unit synchronously and used to detect the voltage and current of each battery unit during the discharge process. The robot transfer unit is used for Move the battery unit designated as the main battery to one location, and move the battery unit designated as the auxiliary battery to another location. The output terminals of the parallel-connected battery units are connected to the first DC/AC circuit and the boost circuit in sequence, and the output terminals of the series-connected battery units are connected to the second DC/AC circuit. The control unit controls the boost circuit before the switching time. The output circuit of the external load controls the second DC/AC circuit as the output circuit to the external load after the switching time.

Description

A modular energy storage bidirectional converter

Technical field

The invention relates to the technical field of energy storage, and in particular to a modular energy storage bidirectional converter.

Background technique

Bidirectional converter is an energy storage converter, also known as bidirectional energy storage inverter. It is used in AC coupled energy storage systems such as grid-connected energy storage and microgrid energy storage to connect the battery pack and the grid (or load). , is a device that realizes two-way conversion of electrical energy. It can invert the DC power of the battery into AC power and transmit it to the grid or use it for AC loads. It can also rectify the AC power of the grid into DC power to charge the battery. In a microgrid system composed of multiple energy sources, the bidirectional converter is The most core equipment.

Current bidirectional converters all use modular energy storage, that is, most of the energy storage batteries used are retired batteries from electric vehicles, which are connected into energy storage modules. Because the output voltage of a single battery is only 15V DC, in order to convert it to AC 220V mains voltage, each battery needs to be connected in series to increase the output voltage, and then converted to output mains voltage through a DC/AC circuit. However, since each battery is not uniformly shipped from the same manufacturer, there will be imbalance problems in each battery during use. Even if batteries with the same capacity and voltage are screened before assembly, such problems cannot be avoided. The discharge time of each battery discharged in series is limited by the minimum capacity. If things go on like this, the aging of the battery with the smallest capacity will be accelerated. At the same time, there is also the problem of low discharge efficiency during each discharge.

Contents of the invention

The present invention aims to solve the above technical problems and provide a modular energy storage bidirectional converter.

The technical solution of the present invention is a modular energy storage bidirectional converter, which includes a number of battery units arranged on a battery rack in an electrical cabinet. The electrical cabinet is also provided with a discharge load, a detection unit, and a control unit. unit, the discharge load is used to connect to each of the battery units in turn to conduct a discharge test, the detection unit and the discharge load are connected to each of the battery units synchronously and are used to discharge the battery units in each unit. During the process, voltage and current are detected, and the control unit calibrates half of the battery units with close to the measured capacity and the remaining half of the battery units as the main battery and the auxiliary battery respectively, and the manipulator transfer unit It is used to move the battery unit calibrated as the main battery to one place, and the battery unit calibrated as the auxiliary battery to another place; wherein, each of the battery units calibrated as the main battery is relative to each other. are connected in series, and each of the battery units calibrated as an auxiliary battery is connected in parallel with each other. The control unit generates a switching time based on the capacity measurement test data of the battery unit calibrated as an auxiliary battery. The switching time is The conversion time is based on the activation start time of the battery unit calibrated as an auxiliary battery as the time zero point. The output terminals of the parallel-connected battery units are connected to the first DC/AC circuit and the boost circuit in sequence. The series-connected battery units The output end is connected to a second DC/AC circuit, and the control unit controls the boost circuit as an output circuit to the external load before the switching time, and controls the voltage boost circuit after the switching time. The second DC/AC circuit serves as the output circuit to the external load.

As an implementation manner, the switching time is an interval time, and the switching time includes a first time node and a second time node, and the first time node is earlier than the second time node in time sequence. At the first time node, the control unit controls the battery units connected in series to be turned on so that the second DC/AC circuit serves as an output circuit to an external load. At the second time node, The control unit controls the battery cells connected in parallel to be disconnected to stop the boost circuit from serving as an output circuit to an external load.

As an implementation manner, the switching time is configured after an actual loss capacity of the maximum capacity in the parallel-connected battery units exceeds half.

As an implementation manner, when calibrating the main battery and the auxiliary battery, the control unit, after eliminating the battery unit with the largest capacity and the battery unit with the smallest capacity, selects the remaining battery units with a capacity close to The calibration is the main battery.

As an embodiment, a positive electrode wire is connected between the positive electrodes of each battery unit, a negative electrode wire is connected between the negative electrodes of each battery unit, and the positive electrode wires of adjacent battery units are connected to each other. Positive and negative conductors are connected between the negative conductors. The nodes of the positive and negative conductors separate the positive conductor into a first conductor segment and a second conductor segment, and the negative conductor separates into a third conductor segment and a second conductor segment. The fourth conductor segment, the first conductor segment is provided with a positive parallel contactor, the fourth conductor segment is provided with a negative parallel contactor, the positive and negative conductors are provided with a series contactor, the positive conductor , the negative electrode wire, the positive and negative electrode wires, the positive parallel contactor, the negative parallel contactor, and the series contactor are all integrated on a connection cover plate, and the connection cover plate is connected to the phase adjacent to the positive and negative electrodes of the battery unit.

As an implementation manner, the positive parallel contactor, the negative parallel contactor and the series contactor are interlocked.

As an implementation manner, the positive parallel contactor and the negative parallel contactor switch synchronously in response to the control signal of the control unit, and the series contactor switches in response to the control signal of the control unit, so that the calibration Both the battery unit used as the main battery and the battery unit designated as the auxiliary battery can be switched between series connection and parallel connection.

As an implementation manner, before the battery unit calibrated as the auxiliary battery is activated, the control unit controls the discharge load and the detection unit to access the battery unit calibrated as the main battery to monitor all the battery units. The battery units are subjected to the same number of discharge tests as the number of battery units. During each discharge process, the battery unit with insufficient capacity first is calibrated and an auxiliary output voltage is provided to it so that it can continue to participate in the next discharge. test, and at the same time, the control unit generates a time node for providing auxiliary output voltage. At the end of the last discharge test, the control unit generates a time node for providing auxiliary output voltage to the last battery unit with insufficient capacity, and uses the last all The time node is the reference time, and a one-to-one correspondence between the last time node and each other time node is generated corresponding to the discharge time of each battery unit. The control unit determines the discharge time according to each discharge time and the discharge time. The voltage and current data measured in the test are generated one-to-one corresponding to the capacity compensation amount of each battery unit. Compensation capacitors are connected to both ends of each battery unit in series. The actual capacity of each compensation capacitor is based on the The capacity compensation amount is configured. After the switching time, the control unit controls each of the battery units connected in parallel to disconnect each other, and connects each of the battery units to each of the compensation units. capacitance until the actual capacity of each compensation capacitor reaches the configured value.

As an implementation manner, the compensation capacitor is a capacitor whose capacity can be adjusted.

As an implementation manner, the control unit causes the compensation capacitor to connect the battery units connected in series after the actual capacity reaches the configured value.

Compared with the prior art, the beneficial effect of the present invention is that after the battery units are respectively calibrated as the main battery and the auxiliary battery through the capacity measurement test, the battery units calibrated as the main battery are connected in series with each other, and the calibrated The battery cells of the auxiliary battery are connected in parallel with each other, so that they can be used as two outputs. The main battery unit has good consistency due to stricter screening and is no longer easily limited by the capacity of a single battery unit. Secondly, in order to make the remaining half of the battery units available for use after screening, they are connected in parallel for output. Then one group is connected to the first DC/AC circuit and the boost circuit, and the other group is connected to the second DC/AC circuit. The switching conversion time is used as the time node to allow the output of the two to be converted. In this way, the modular energy storage bidirectional converter is no longer limited by the capacity of a single battery unit and can have a stable output for a longer period of time, thus improving the overall energy conversion efficiency.

Description of the drawings

Figure 1 is a functional schematic diagram of a modular energy storage bidirectional converter provided by an embodiment of the present invention;

Figure 2 is a schematic diagram of series-connected battery units provided by an embodiment of the present invention;

Figure 3 is a schematic diagram of parallel battery units provided by an embodiment of the present invention;

Figure 4 is a schematic connection diagram of each battery unit provided by the embodiment of the present invention;

Figure 5 is a schematic diagram of the connection between each battery unit and the compensation capacitor provided by the embodiment of the present invention.

In the picture: 100, electrical cabinet; 200, battery rack compartment; 300, battery unit; 400, discharge load; 500, detection unit; 600, control unit; 700, robot transfer unit; 800, first DC/AC circuit; 900. Boost circuit; 1000. Second DC/AC circuit; 1100. Positive wire; 1200. Negative wire; 1300. Positive and negative wires; 1400. First wire segment; 1500. Second wire segment; 1600. Third Wire segment; 1700, fourth wire segment; 1800, positive parallel contactor; 1900, negative parallel contactor; 2000, series contactor; 2100, connection cover; 2200, compensation capacitor.

Detailed ways

The above-mentioned and additional embodiments and advantages of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, but not all, of the embodiments of the present invention.

In one implementation, as shown in Figures 1-3.

The modular energy storage bidirectional converter provided by this embodiment includes a number of battery units 300 located on the battery rack compartment 200 in the electrical cabinet 100. The electrical cabinet 100 is also provided with a discharge load 400, a detection unit 500, and The control unit 600 and the discharge load 400 are used to access each battery unit 300 in turn to perform a discharge test. The detection unit 500 and the discharge load 400 are connected to each battery unit 300 synchronously and are used to connect each battery unit 300 during the discharge process. The control unit 600 performs voltage and current detection, and the control unit 600 calibrates half of the battery units 300 with similar measured capacities and the remaining half of the battery units 300 as the main batteries and the auxiliary batteries respectively, and the robot transfer unit 700 is used to calibrate the calibrated main batteries. The battery unit 300 is moved to one place, and the battery unit 300 labeled as an auxiliary battery is moved to another place. Among them, each battery unit 300 calibrated as a main battery is connected in series with each other, and each battery unit 300 calibrated as an auxiliary battery is connected in parallel with each other. The control unit 600 is based on the capacity measurement test of the battery unit 300 calibrated as an auxiliary battery. The data generates a switching time. The switching time takes the start time of the battery unit 300 calibrated as an auxiliary battery as the time zero point. The output terminals of the parallel battery units 300 are sequentially connected to the first DC/AC circuit 800 and the booster. In the circuit 900, the output end of the series-connected battery unit 300 is connected to the second DC/AC circuit 1000. The control unit 600 controls the boost circuit 900 as an output circuit to the external load before the switching time, and controls the boost circuit 900 after the switching time. The second DC/AC circuit 1000 is used as an output circuit to an external load.

In this embodiment, in order to improve the overall energy conversion efficiency and reduce energy loss, a modular energy storage bidirectional converter is provided. Different from the traditional working mode of bidirectional converter using series output, as described in the background art, this application proposes an improved working mode that can improve energy conversion efficiency. Before describing the working mode of the modular energy storage bidirectional converter, it is necessary to supplement the description of the existing technology and explain why the parallel output working mode is not used in the existing technology. We know that the output voltage of a single battery unit 300 is only 15V. To convert it to 220V, a boost circuit is required to significantly boost the voltage. The energy consumption of the boost circuit is very large. Secondly, connecting so many battery units 300 in parallel means that Doubling the current output will cause great energy loss and heat generation in the circuit. Although the parallel output is not limited by the 300 capacity of a single battery unit, its considerable energy loss cannot be ignored.

Under the above circumstances, before use of the modular energy storage bidirectional converter provided by this embodiment, a capacitance test is performed on all battery units 300, and the discharge load 400 is connected to each battery unit 300 in sequence to perform a capacity test. In the discharge test, the detection unit 500 and the discharge load 400 are synchronously connected to each battery unit 300 and perform voltage and current detection on each battery unit 300 during the discharge process, thereby determining half of the battery units 300 with closer capacities, and other Half battery cell 300. The reason for this is because, as mentioned in the background art, each battery is not uniformly manufactured by one manufacturer, and the consistency of the battery is difficult to strictly control. After the battery units 300 are respectively calibrated as the main battery and the auxiliary battery through the capacitance test, the battery units 300 calibrated as the main batteries are connected in series with each other, and the battery units 300 calibrated as the auxiliary batteries are connected with each other. In parallel connection, it can be used as two outputs. The main one has been strictly screened and the battery unit 300 has good consistency and is no longer easily limited by the capacity of a single battery unit 300. Secondly, in order to enable half of the remaining battery units 300 to be put into use after screening, they are connected in parallel for output. Then one group is connected to the first DC/AC circuit 800 and the boost circuit 900, and the other group is connected to the second DC/AC circuit 1000. The switching time is used as the time node to allow the outputs of the two to be converted. For example, when starting to use, the parallel-connected battery unit 300 first outputs through the first DC/AC circuit 800 and the boost circuit 900. After a period of use, the series-connected battery unit 300 outputs through the second DC/AC circuit 1000. . In this way, the modular energy storage bidirectional converter is not limited by the capacity of a single battery unit 300 and can have a stable output for a longer period of time, thereby improving the overall energy conversion efficiency.

In one embodiment, the switching time of the modular energy storage bidirectional converter is an interval time, and the switching time includes a first time node and a second time node, and the first time node is earlier in time sequence. At the second time node, at the first time node, the control unit 600 controls the series-connected battery unit 300 to be turned on so that the second DC/AC circuit 1000 serves as an output circuit to the external load. At the second time node, the control unit 600 controls The parallel connected battery cells 300 are disconnected to stop the boost circuit 900 from functioning as an output circuit to an external load.

In this embodiment, the switching time can be set as an interval time. The switching time includes a first time node and a second time node. The first time node is earlier than the second time node in time sequence. At one time node, the control unit 600 controls the series-connected battery units 300 to turn on so that the second DC/AC circuit 1000 serves as an output circuit to the external load. At a second time node, the control unit 600 controls the parallel-connected battery units 300 to turn off so that the second DC/AC circuit 1000 serves as an output circuit to the external load. Stop boost circuit 900 as an output circuit to an external load. In other words, there is no interruption between the two outputs.

In one embodiment, the switching time is configured after an actual loss capacity of the maximum capacity of the parallel-connected battery units 300 exceeds half. In addition, when calibrating the main battery and the auxiliary battery, the control unit 600 removes the battery unit 300 with the largest capacity and the battery unit 300 with the smallest capacity, and then selects the calibrated main battery with a similar capacity from the remaining battery units 300 .

In this embodiment, an implementation of switching time is provided, and an implementation of screening battery units 300 is also provided. After eliminating the maximum capacity and the minimum capacity, battery units 300 with closer capacities can be screened. .

In one embodiment, as shown in Figure 4.

In the modular energy storage bidirectional converter provided by this embodiment, a positive wire 1100 is connected between the positive electrodes of each battery unit 300, and a negative wire 1200 is connected between the negative electrodes of each battery unit 300, connecting adjacent ones. Positive and negative wires 1300 are connected between the positive wire 1100 and the negative wire 1200 of the battery unit 300. The nodes of the positive and negative wires 1300 separate the positive wire 1100 into a first wire segment 1400 and a second wire segment 1500, and the negative wire 1200 The third conductor segment 1600 and the fourth conductor segment 1700 are separated. The first conductor segment 1400 is provided with a positive parallel contactor 1800. The fourth conductor segment 1700 is provided with a negative parallel contactor 1900. The positive and negative conductors 1300 are provided with The series contactor 2000, the positive wire 1100, the negative wire 1200, the positive and negative wires 1300, the positive parallel contactor 1800, the negative parallel contactor 1900, and the series contactor 2000 are all integrated on a connection cover 2100, and the connection cover 2100 The positive and negative electrodes of adjacent battery cells 300 are connected.

In this embodiment, both the parallel-connected battery units 300 and the series-connected battery units 300 use this wiring method. Whether they are connected in series or in parallel, they can be realized through the control of the control unit 600 . For example, if all the positive parallel contactors 1800 and the negative parallel contactors 1900 are controlled to be closed and the series contactors 2000 are opened, then the connection mode of each battery unit 300 is parallel, and all the series contactors 2000 are controlled to be closed and the positive parallel contactors 1800 and the negative parallel contactor are connected in parallel. When the contactor 1900 is disconnected, the connection mode of each battery unit 300 is in series. Therefore, this connection method can realize controlled switching of parallel and series connections. In a specific embodiment, since the robot transfer unit 700 is used to move the battery unit 300 designated as the main battery to one place and the battery unit 300 designated as the auxiliary battery to another place, traditional wiring is used. The approach will change dramatically. In this embodiment, the positive wire 1100, the negative wire 1200, the positive and negative wires 1300, the positive parallel contactor 1800, the negative parallel contactor 1900, and the series contactor 2000 are all integrated on a connection cover 2100, and the connection cover 2100 The positive and negative electrodes of adjacent battery cells 300 are connected. Therefore, no matter how each battery unit 300 moves, no matter whether it is connected in series or in parallel after movement, there is no need to adjust the connection cover 2100, and all controls are centralized controlled by the control unit 600. Easy to operate and highly implementable.

In a preferred embodiment, the positive parallel contactor 1800, the negative parallel contactor 1900 and the series contactor 2000 are interlocked.

In a preferred embodiment, the positive parallel contactor 1800 and the negative parallel contactor 1900 switch synchronously in response to the control signal of the control unit 600, and the series contactor 2000 switches in response to the control signal of the control unit 600, so as to calibrate the main battery. Both the battery unit 300 and the battery unit 300 designated as an auxiliary battery can be switched between series connection and parallel connection.

In one embodiment, as shown in Figure 5.

In the modular energy storage bidirectional converter provided by this embodiment, before the battery unit 300 calibrated as the auxiliary battery is activated, the control unit 600 controls the discharge load 400 and the detection unit 500 to access the battery unit 300 calibrated as the main battery. , to perform the same number of discharge tests on the battery units 300 as the number of battery units 300. During each discharge process, the battery unit 300 with insufficient capacity first is calibrated and an auxiliary output voltage is provided to it so that it can continue to participate in the next During the discharge test, the control unit 600 generates a time node for providing the auxiliary output voltage. At the end of the last discharge test, the control unit 600 generates a time node for providing the auxiliary output voltage to the last battery unit 300 with insufficient capacity, and the last time node is The reference time generates a one-to-one correspondence between the last time node and each other time node corresponding to the discharge time of each battery unit 300. The control unit 600 generates one-to-one correspondence based on each discharge time and the voltage and current data measured in the discharge test. Corresponding to the capacity compensation amount of each battery unit 300, compensation capacitors 2200 are connected to both ends of each battery unit 300 in series. The actual capacity of each compensation capacitor 2200 is configured according to the capacity compensation amount. After the switching conversion time, the control unit 600 controls each battery unit 300 connected in parallel to disconnect each other, and connects each battery unit 300 to each compensation capacitor 2200 until the actual capacity of each compensation capacitor 2200 reaches the configured value.

In this embodiment, in order to improve the output quality, that is, the stability of the output voltage, during the main output process, one-to-one capacity compensation is performed on each battery unit 300 so that the consistency of each battery unit 300 is highly consistent, basically This eliminates the battery consistency issues currently plagued by bidirectional converters. In the working mode mentioned in the first embodiment in which the parallel-connected battery units 300 output before the series-connected battery units 300 , adaptive matching is made for the capacity compensation of each series-connected battery unit 300 in this embodiment. The determination of the switching time is also reflected in this. After leaving enough compensation capacity for the parallel battery units 300, the switching time is set before the time. Specifically, before the battery unit 300 calibrated as the auxiliary battery is activated, the control unit 600 controls the discharge load 400 and the detection unit 500 to access the battery unit 300 calibrated as the main battery, so as to perform the sum of the battery unit 300 and the number of the battery units 300 . During the same number of discharge tests, during each discharge process, the battery unit 300 with insufficient capacity first is calibrated and an auxiliary output voltage is provided to it so that it can continue to participate in the next discharge test. At the same time, the control unit 600 generates and provides an auxiliary output voltage. At the end of the last discharge test, the control unit 600 generates a time node for providing the auxiliary output voltage to the last battery unit 300 with insufficient capacity, and uses the last time node as the reference time to generate the last time node and various other times. The one-to-one correspondence between the nodes corresponds to the discharge time of each battery unit 300. The control unit 600 generates a one-to-one capacity compensation amount corresponding to each battery unit 300 based on each discharge time and the voltage and current data measured in the discharge test. The above-mentioned number of discharge tests equal to the number of battery units 300 can determine the amount of compensation required for each battery unit 300 . In fact, since these battery units 300 have undergone relatively strict screening and are 50% selected from the original battery units 300, the capacity difference between each battery unit 300 is not big, so the capacity that needs to be compensated is also Relatively limited. Therefore, in the working mode of parallel-connected battery units 300 outputting, each battery unit 300 can be basically consumed, leaving only a small part for capacity compensation. Then, in the output working mode of the battery units 300 connected in series, each battery unit 300 can basically consume power simultaneously. Through the above working method, because the switching time can be set as close as possible before the parallel-connected battery units 300 are consumed to only the compensation capacity, the screened parallel-connected battery units 300 are also involved most of the time. Provided for use, it can further improve energy conversion efficiency. In addition, in the working mode of the series-connected battery units 300 outputting, due to one-to-one compensation, the output voltage is stable and the output quality is high. The most important thing is that for the main battery unit 300, each battery unit 300 basically consumes power simultaneously, and there is no over-discharge. Correspondingly, there is no overcharge during the charging process. Therefore, compared with the original battery unit 300 connected in series, the service life is improved.

The above-mentioned specific embodiments further describe in detail the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. It is particularly pointed out that for those skilled in the art, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A modular energy storage bidirectional converter, characterized in that it includes a number of battery units located on a battery rack in an electrical cabinet. The electrical cabinet is also provided with a discharge load, a detection unit, and a control unit. , the discharge load is used to access each of the battery units in turn to perform a discharge test, and the detection unit and the discharge load are synchronously connected to each of the battery units and used to perform the discharge process of each of the battery units. The voltage and current are detected in it, and the control unit calibrates half of the battery units with close to the measured capacity and the remaining half of the battery units as the main battery and the auxiliary battery respectively, and the robot transfer unit uses The battery unit calibrated as the main battery is moved to one place, and the battery unit calibrated as the auxiliary battery is moved to another place; Wherein, the battery units calibrated as main batteries are connected in series with each other, and the battery units calibrated as auxiliary batteries are connected in parallel with each other. The control unit determines the battery units calibrated as auxiliary batteries according to the control unit. The capacity measurement test data generates a switching time. The switching time is based on the activation start time of the battery unit calibrated as an auxiliary battery. The output terminals of the parallel battery units are sequentially connected to the first A DC/AC circuit and a boost circuit, the output end of the battery unit in series is connected to a second DC/AC circuit, and the control unit controls the boost circuit as a power supply to the external load before the switching time. An output circuit controls the second DC/AC circuit as an output circuit to an external load after the switching time. 2. The modular energy storage bidirectional converter according to claim 1, characterized in that the switching time is an interval time, and the switching time includes a first time node and a second time. node, the first time node is earlier than the second time node in time sequence, and at the first time node, the control unit controls the battery units connected in series to turn on so that the second DC/AC The circuit serves as an output circuit to the external load. At the second time node, the control unit controls the parallel-connected battery units to be disconnected to stop the boost circuit from serving as an output circuit to the external load. 3. The modular energy storage bidirectional converter according to claim 2, wherein the switching time is configured after more than half of the actual loss capacity of the maximum capacity of the parallel-connected battery units. 4. The modular energy storage bidirectional converter according to claim 1, characterized in that when the control unit is calibrating the main battery and the auxiliary battery, the battery unit with the largest capacity and the battery unit with the smallest capacity are eliminated. After the battery unit is described, the calibrated main battery with a similar capacity is selected from the remaining battery units. 5. The modular energy storage bidirectional converter according to claim 1, characterized in that, the positive electrodes of each battery unit are connected with positive wires, and the negative electrodes of each battery unit are connected with Negative electrode wires. Positive and negative electrode wires are connected between the positive electrode wires and the negative electrode wires of adjacent battery units. The nodes of the positive and negative electrode wires separate the positive electrode wires into first wire segments and The second conductor segment divides the negative conductor into a third conductor segment and a fourth conductor segment, the first conductor segment is provided with a positive parallel contactor, and the fourth conductor segment is provided with a negative parallel contactor, A series contactor is provided on the positive and negative electrode wires, the positive electrode wire, the negative electrode wire, the positive and negative electrode wires, the positive electrode parallel contactor, the negative electrode parallel contactor, and the series contactor They are all integrated on a connecting cover plate, and the connecting cover plate is connected to the positive and negative electrodes of the adjacent battery units. 6. The modular energy storage bidirectional converter according to claim 5, characterized in that the positive parallel contactor, the negative parallel contactor and the series contactor are interlocked. 7. The modular energy storage bidirectional converter according to claim 5, wherein the positive parallel contactor and the negative parallel contactor switch synchronously in response to the control signal of the control unit, and the The series contactor switches in response to the control signal of the control unit, so that both the battery unit calibrated as the main battery and the battery unit calibrated as the auxiliary battery can be switched between series connection and parallel connection. 8. The modular energy storage bidirectional converter according to claim 1, characterized in that, before the battery unit calibrated as an auxiliary battery is activated, the control unit controls the discharge load and the detection The unit is connected to the battery unit calibrated as the main battery to perform a discharge test on the battery unit for the same number of times as the number of battery units. During each discharge process, the battery with insufficient capacity first is calibrated. unit and provide auxiliary output voltage to it so that it can continue to participate in the next discharge test. At the same time, the control unit generates a time node for providing the auxiliary output voltage. At the end of the last discharge test, the control unit generates a signal to the last insufficient capacity. The battery unit provides a time node of the auxiliary output voltage, and using the last time node as the reference time, a one-to-one correspondence between the last time node and each other time node is generated for each of the battery units. The control unit generates a one-to-one capacity compensation amount corresponding to each of the battery units according to each of the discharge times and the voltage and current data measured in the discharge test. Two of the battery units in series are Compensation capacitors are connected to both terminals, and the actual capacity of each compensation capacitor is configured according to the capacity compensation amount. After the switching time, the control unit controls the balance between each of the parallel battery units. Disconnect, and connect each battery unit to each compensation capacitor until the actual capacity of each compensation capacitor reaches the configured value. 9. The modular energy storage bidirectional converter according to claim 8, wherein the compensation capacitor is a capacitor with an adjustable capacity. 10. The modular energy storage bidirectional converter according to claim 8, wherein the control unit causes the compensation capacitor to connect the series-connected battery units after the actual capacity reaches the configured value.