An all-vanadium redox flow battery acdc type equalization system and an electric energy equalization method thereof

Abstract

The application relates to a full-vanadium liquid flow battery ACDC type equalization system and an electric energy equalization method thereof, and the system comprises an ACDC equalizer, a PDU power distribution unit and a PCS energy storage converter; each battery subsystem of the full-vanadium liquid flow battery is connected with an AC power grid through the PCS energy storage converter to form a general charge-discharge circuit; the AC power grid is connected with the positive and negative electrodes of each battery subsystem in the full-vanadium liquid flow battery through the ACDC equalizer and the PDU power distribution unit in sequence to form an equalization charge-discharge circuit, wherein the PDU power distribution unit comprises two front-stage busbars connected with the positive and negative electrodes of the ACDC equalizer, and a plurality of rear-stage busbars connected with the positive and negative electrodes of each battery subsystem; the front-stage busbars are connected with the rear-stage busbars through switching switches KpN and KnN after being branched. The application forms an efficient charge-discharge circuit for each battery subsystem, cooperates with an intelligent master control system, realizes energy balance among battery units and realizes automatic and efficient electric quantity equalization of the full-vanadium liquid flow battery subsystem.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power storage technology and system equipment, in particular to a vanadium redox flow battery ACDC type equalization system and an electric energy equalization method thereof. BACKGROUND

[0002] At present, in the field of power storage technology, vanadium redox flow batteries are attracting much attention due to their long service life, large energy storage capacity, high energy efficiency and good environmental adaptability. With the increasing scale and complexity of vanadium redox flow battery systems, the imbalance problem between battery subsystems gradually emerges, and this problem directly affects the performance and service life of the overall system. The battery equalization problem of vanadium redox flow batteries mainly reflects in the concentration difference of electrolyte and the voltage difference of battery cells. The charge and discharge states of each battery cell cannot be kept consistent during long-term operation, which leads to uneven distribution of vanadium ion concentration of electrolyte, and further causes the decline of battery performance and the loss of capacity. In addition, the voltage difference between battery cells can cause some battery subsystems to be overcharged or overdischarged, further aggravating the aging and damage risk of the battery. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a vanadium redox flow battery ACDC type equalization system and an electric energy equalization method thereof. The ACDC equalizer and PDU power distribution unit constitute an efficient charge and discharge circuit for each battery subsystem, cooperate with the intelligent master control system, real-time monitor the voltage and power parameters of the battery cells, and feedback control the ACDC equalizer and PDU power distribution unit, to realize the energy balance between the battery cells and the automatic and efficient power balance of the vanadium redox flow battery subsystem, and further improve the overall performance and service life of the vanadium redox flow battery system.

[0004] The ACDC type balancing system of the all-vanadium redox flow battery comprises an ACDC balancer, a PDU power distribution unit and a PCS energy storage converter; each battery subsystem of the all-vanadium redox flow battery is connected to an AC power grid through the PCS energy storage converter to form a general charge-discharge circuit; the AC power grid is connected to the positive and negative electrodes of each battery subsystem in the all-vanadium redox flow battery through the ACDC balancer and the PDU power distribution unit in sequence to form a balancing charge-discharge circuit, wherein the PDU power distribution unit comprises two front-stage busbars connected to the positive and negative electrodes of the ACDC balancer and a plurality of rear-stage busbars connected to the positive and negative electrodes of each battery subsystem; in the balancing charge-discharge circuit comprising N battery subsystems, the positive electrode end of the ACDC balancer is divided into N branches, and a switching switch KpN is arranged on the corresponding branch; the negative electrode of the ACDC balancer is divided into N branches, and a switching switch KnN is arranged on the corresponding branch; the branch where the switching switch Kp1 is located is connected to the rear-stage busbar on the positive electrode side of the first battery subsystem, the branch where the switching switch KnN is located is connected to the rear-stage busbar on the negative electrode side of the Nth battery subsystem, and the branch where the switching switch KpN is located is connected to the rear-stage busbar on the positive electrode side of the Nth battery subsystem after being merged with the branch where the switching switch Kn-1N is located.

[0005] Optimally, the front-stage busbar is provided with balancer main switches Q1 and Q2 for disconnecting the PDU power distribution unit from the ACDC balancer, and the front-stage busbar is provided with a battery cluster switch Qn+2 for switching the battery subsystem connected in the balancing circuit.

[0006] Further, in the balancing charge-discharge circuit comprising N battery subsystems, the positive busbar at the output end of the ACDC balancer is divided into N branches after passing through the balancer main switch Q1, and the switching switch KpN is arranged on the corresponding branch; the negative electrode at the output end of the ACDC balancer is divided into N branches after passing through the balancer main switch Q2, and the switching switch KnN is arranged on the corresponding branch; the branch where the switching switch Kp1 is located is connected to the positive electrode side of the first battery subsystem after passing through the battery cluster switch Q3, the branch where the switching switch KnN is located is connected to the negative electrode side of the Nth battery subsystem after passing through the battery cluster switch Qn+3, and the branch where the switching switch KpN is located is connected to the positive electrode side of the Nth battery subsystem after passing through the battery cluster switch Qn+2 after being merged with the branch where the switching switch Kn-1N is located.

[0007] Optimally, the ACDC balancer is provided with a power transmission circuit for forming a power mode charge-discharge channel, the power transmission circuit comprises a main power circuit, a rectifier bridge circuit and an inverter circuit, the rectifier bridge circuit and the inverter circuit are connected in series after being connected in parallel with the charge-discharge switch, and are connected in series at the rear-stage and front-stage of the main power circuit.

[0008] Optimally, an isolation transformer is arranged between the AC power grid and the ACDC balancer and the PCS energy storage converter.

[0009] The ACDC type equalization system of the all-vanadium redox flow battery further comprises a master control device, an input end of the master control device being connected with the PCS energy storage converter and each battery subsystem, and an output end of the master control device being connected with the ACDC equalizer and the PDU power distribution unit; the master control device comprises a microprocessor, a multi-channel signal channel module, a relay module, a 485 interface module, a DO / AO interface module, a display module and a wireless data transmission module.

[0010] Further, the voltage transformer and the SOC sensor integrated on the PCS energy storage converter and each battery subsystem are connected with the input end of the microprocessor through the multi-channel signal channel module, the output end of the microprocessor is connected with the DO / AO interface module through the relay module, and the 485 interface module, the wireless data transmission module and the display module are connected with the microprocessor in series. The microprocessor is communicatively connected with the PCS energy storage converter and the ACDC equalizer through the 485 interface module, the former being used for receiving signals and judging the charging and discharging working condition signals, and the latter being used for controlling the ACDC equalizer to switch the voltage control mode / power mode; after the microprocessor determines the battery subsystems that need to be charged and discharged, the output signals are converted into switch signals or analog signals by the relay module, and then the signals are transmitted to the main switch of the equalizer, the battery cluster switch and the switching switch through the DO / AO interface module, so as to realize automatic control; the display module is integrated with a liquid crystal display screen, which is used for displaying the PCS charging and discharging working condition judged by the microprocessor, the charging and discharging voltage and the SOC value of each battery subsystem, the number of the battery subsystems that need to be charged and discharged, the charging and discharging time and the progress and other parameters; the wireless data transmission module is used for synchronously uploading the above-mentioned parameter data to a remote host computer, and downloading and executing the instructions or programs sent by the remote host computer for parameter adjustment or system upgrade.

[0011] The electric energy equalization method of the ACDC type equalization system of the all-vanadium redox flow battery, which realizes the electric energy equalization of each battery subsystem in the charging and discharging process through the above-mentioned ACDC type equalization system of the all-vanadium redox flow battery, comprises the following steps,

[0012] S1: the system closes the equalizer main switch Q1 and Q2 and all battery cluster switches Qn+2 of the PDU power distribution unit;

[0013] S2: the system starts the ACDC equalizer to run and establish voltage;

[0014] S3: the system judges the charging and discharging direction of the battery subsystem;

[0015] S4: the system determines the battery subsystems that need to be charged and discharged;

[0016] S5: The system controls the ACDC equalizer to change the mode, controls the switching switch of the PDU power distribution unit, and charges or discharges the battery subsystem that needs to be charged or discharged.

[0017] Further, the method for determining the battery subsystem that needs to be charged or discharged in step S4 is:

[0018] S41: When the system in step S3 determines that the PCS energy storage converter is in a forward charging working condition, the SOC values of each battery subsystem are collected and sorted, wherein the highest battery subsystem SOC value is recorded as SOC_max, the lowest battery subsystem SOC value is recorded as SOC_min, and the serial number is recorded as A; when SOC_max-SOC_min>X%, it is determined that the battery subsystem A needs to be charged.

[0019] S42: When the system in step S3 determines that the PCS energy storage converter is in a reverse discharging working condition, the SOC values of each battery subsystem are collected and sorted, wherein the lowest battery subsystem SOC value is recorded as SOC_min, the highest battery subsystem SOC value is recorded as SOC_max, and the serial number is recorded as B; when SOC_max-SOC_min>X%, it is determined that the battery subsystem B needs to be discharged.

[0020] Further, the method for charging the battery subsystem that needs to be charged in step S5 is:

[0021] S4151: The system controls the ACDC equalizer to output a voltage that is the current voltage value of the battery subsystem A, and then controls the PDU power distribution unit to close its corresponding switching switch KpA and KnA.

[0022] S4152: The ACDC equalizer is switched to a power mode to charge the battery subsystem A; when the battery subsystem SOC_max-SOC_min<Y%, the charging is completed, the positive and negative switching switches KpA and KnA are disconnected, and then the ACDC equalizer is switched to a control voltage mode and returns to step S4.

[0023] Further, the method for discharging the battery subsystem that needs to be discharged in step S5 is:

[0024] S4251: The system controls the PDU power distribution unit to close its corresponding switching switch KpB and KnB.

[0025] S4252: The ACDC equalizer is switched to a power mode to discharge the battery subsystem B to the AC power grid; when the battery subsystem SOC_max-SOC_min<Y%, the discharging is completed, the positive and negative switching switches KpB and KnB are disconnected, and then the ACDC equalizer is switched to a control voltage mode and returns to step S4.

[0026] The full vanadium redox flow battery ACDC type equalization system and the electric energy equalization method have the following beneficial effects:

[0027] (1) The ACDC equalizer and the PDU power distribution unit form an efficient charging and discharging circuit for each battery subsystem;

[0028] (2) The intelligent master control system monitors the voltage and power parameters of the battery unit in real time, displays and transmits data on site, and ensures that the operation state and power balance process of the battery subsystem are clear and known;

[0029] (3) The intelligent master control system controls the ACDC equalizer and the PDU power distribution unit, realizes the energy balance between the battery units, and realizes the automatic and efficient power balance of the full vanadium redox flow battery subsystem. BRIEF DESCRIPTION OF DRAWINGS

[0030] The full vanadium redox flow battery ACDC type equalization system and the electric energy equalization method will be further described below in conjunction with the drawings:

[0031] Figure 1 is the logic structure and connection principle line frame diagram of the full vanadium redox flow battery ACDC type equalization system embodiment 1;

[0032] Figure 2 is the circuit diagram of the PDU power distribution unit in the full vanadium redox flow battery ACDC type equalization system embodiment 2;

[0033] Figure 3 is the logic structure connection line frame diagram of the power transmission circuit in the full vanadium redox flow battery ACDC type equalization system embodiment 3;

[0034] Figure 4 is the logic structure and connection principle line frame diagram of the full vanadium redox flow battery ACDC type equalization system embodiment 5;

[0035] Figure 5 is the logic structure connection line frame diagram of the master control device in the full vanadium redox flow battery ACDC type equalization system embodiment 5;

[0036] Figure 6 is the implementation step diagram of the full vanadium redox flow battery ACDC type equalization system electric energy equalization method;

[0037] Figure 7 is the operation flow chart of the full vanadium redox flow battery ACDC type equalization system electric energy equalization method;

[0038] Figure 8 is the switch action timing chart of the full vanadium redox flow battery ACDC type equalization system electric energy equalization method.

[0039] In the drawings:

[0040] 1-ACDC equalizer, 2-PDU power distribution unit, 3-PCS energy storage converter, 4-battery subsystem, 5-AC grid, 6-isolation transformer

[0041] 11-power transmission circuit; 111-main power circuit, 112-rectifier bridge circuit, 113-inverter circuit

[0042] 10-master control device; 101-microprocessor, 102-multi-channel signal channel module, 103-relay module, 104-485 interface module, 105-DO / AO interface module, 106-display module, 107-wireless data transmission module DETAILED DESCRIPTION

[0043] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0044] In the description of the present application, it should be understood that the terms "left", "right", "front", "back", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation of the present application.

[0045] The technical solutions of the present application are further described below with specific examples, but the protection scope of the present application is not limited to the following examples.

[0046] Example 1: as Figure 1As shown, the ACDC type equalization system of the all-vanadium redox flow battery includes an ACDC equalizer 1, a PDU power distribution unit 2, and a PCS energy storage converter 3. Each battery subsystem 4 of the all-vanadium redox flow battery is connected to an AC power grid 5 through the PCS energy storage converter 3, forming a general charge-discharge circuit. The AC power grid 5 is connected to the positive and negative electrodes of each battery subsystem 4 of the all-vanadium redox flow battery through the ACDC equalizer 1 and the PDU power distribution unit 2, respectively, forming an equalization charge-discharge circuit. The PDU power distribution unit 2 includes two front bus bars connected to the positive and negative electrodes of the ACDC equalizer 1 and a plurality of rear bus bars connected to the positive and negative electrodes of each battery subsystem 4. In the equalization charge-discharge circuit containing N battery subsystems 4, the positive electrode end of the ACDC equalizer 1 is divided into N branches, and a switching switch KpN is provided on the corresponding branch. The negative electrode end of the ACDC equalizer 1 is divided into N branches, and a switching switch KnN is provided on the corresponding branch. The branch with the switching switch Kp1 is connected to the rear bus bar on the positive electrode side of the first battery subsystem, the branch with the switching switch KnN is connected to the rear bus bar on the negative electrode side of the Nth battery subsystem, and the branch with the switching switch KpN is connected to the rear bus bar on the positive electrode side of the Nth battery subsystem after merging with the branch with the switching switch Kn-1N.

[0047] Embodiment 2: As shown in Figure 2 In this embodiment, the equalizer main switches Q1 and Q2 are provided on the front bus bar of the ACDC type equalization system of the all-vanadium redox flow battery for disconnecting the PDU power distribution unit 2 from the ACDC equalizer 1, and the battery cluster switches Qn+2 are provided on the front bus bar for switching the connected battery subsystems in the equalization circuit. In the equalization charge-discharge circuit containing N battery subsystems, the positive electrode bus bar at the output end of the ACDC equalizer 1 is divided into N branches after passing through the equalizer main switch Q1, and the switching switches KpN are respectively provided on the corresponding branches. The negative electrode at the output end of the ACDC equalizer 1 is divided into N branches after passing through the equalizer main switch Q2, and the switching switches KnN are respectively provided on the corresponding branches. The branch with the switching switch Kp1 is connected to the positive electrode side of the first battery subsystem after passing through the battery cluster switch Q3, the branch with the switching switch KnN is connected to the negative electrode side of the Nth battery subsystem after passing through the battery cluster switch Qn+3, and the branch with the switching switch KpN is connected to the positive electrode side of the Nth battery subsystem after passing through the battery cluster switch Qn+2 after merging with the branch with the switching switch Kn-1N. In this embodiment, N is taken as 3 (i.e., the equalization charge-discharge circuit containing three battery subsystems). The remaining structures and components are as described in Embodiment 1 and will not be repeated here.

[0048] Embodiment 3: As shown in Figure 3As shown, the ACDC equalizer 1 of the full vanadium flow battery ACDC equalization system is provided with a power transmission circuit 11 for forming a power mode charging and discharging channel, the power transmission circuit 11 includes a main power circuit 111, a rectifier bridge circuit 112 and an inverter circuit 113, the rectifier bridge circuit 112 and the inverter circuit 113 are connected in parallel after the charging and discharging switch, and are connected in series at the rear stage and the front stage of the main power circuit 11.

[0049] Embodiment 4: The full vanadium flow battery ACDC equalization system is provided with an isolation transformer 6 between the AC power grid 5 and the ACDC equalizer 1 and the PCS energy storage converter 3. The remaining structures and components are as described in Embodiment 1 and will not be repeated.

[0050] Embodiment 5: As shown, Figure 4 , 5 As shown, the full vanadium flow battery ACDC equalization system further includes a master control device 10, the input end of the master control device 10 is connected with the PCS energy storage converter 3 and each battery subsystem 4, and the output end of the master control device 10 is connected with the ACDC equalizer 1 and the PDU power distribution unit 2; the master control device includes a microprocessor 101, a multi-channel signal channel module 102, a relay module 103, a 485 interface module 104, a DO / AO interface module 105, a display module 106 and a wireless data transmission module 107. The voltage transformer and the SOC sensor integrated on the PCS energy storage converter 3 and each battery subsystem 4 are connected with the input end of the microprocessor 101 through the multi-channel signal channel module 102, the output end of the microprocessor 101 is connected with the DO / AO interface module 105 through the relay module 103, and the 485 interface module 104, the wireless data transmission module 106 and the display module 107 are connected with the microprocessor in series. The microprocessor is connected with the PCS energy storage converter and the ACDC equalizer through the 485 interface module, the former is used for receiving signals and judging the charging and discharging working condition signals, and the latter is used for controlling the ACDC equalizer to switch the voltage control mode / power mode; after the microprocessor determines the battery subsystem which needs to be charged and discharged and the charging and discharging are completed, the output signal is converted into a switching signal or an analog signal by the relay module, and then the signal is connected with the equalizer main switch, the battery cluster switch and the switching switch through the DO / AO interface module and is transmitted to execute the signal, so as to realize automatic control; the display module is integrated with a liquid crystal display screen, which is used for displaying the PCS charging and discharging working condition judged by the microprocessor, the charging and discharging voltage and the SOC value of each battery subsystem received, the number of the battery subsystem determined to be charged and discharged, the charging and discharging time and the progress calculated and other parameters; the wireless data transmission module is used for synchronously uploading the above-mentioned parameter data to a remote host computer, and downloading and executing the instructions or programs sent by the remote host computer for parameter adjustment or system upgrading. The remaining structures and components are as described in Embodiment 1 and will not be repeated.

[0051] Embodiment 1. An ACDC-type equalization system for a full vanadium redox flow battery, as shown in Figure 6 , 7 FIG. 1, the method for equalizing electrical energy of the ACDC-type equalization system for a full vanadium redox flow battery comprises the following steps:

[0052] S1: The system closes the equalizer main switches Q1 and Q2 of the PDU power distribution unit 2 and all battery cluster switches Qn+2.

[0053] S2: The system starts the ACDC equalizer 1 to run and establish voltage.

[0054] S3: The system determines the charge and discharge direction of the battery subsystem 4.

[0055] S4: The system determines the battery subsystem 4 that needs to be charged or discharged.

[0056] S5: The system controls the ACDC equalizer 1 to change mode and controls the switching switch of the PDU power distribution unit 2 to charge or discharge the battery subsystem that needs to be charged or discharged.

[0057] The method for determining the battery subsystem that needs to be charged or discharged in step S4 is as follows:

[0058] When the system determines in step S3 that the PCS energy storage converter 3 is in a forward charging working condition, the SOC values of the battery subsystems 4 are collected and sorted, where the highest battery subsystem SOC value is recorded as SOC_max, the lowest battery subsystem SOC value is recorded as SOC_min, and the serial number is recorded as A; when SOC_max-SOC_min>X%, it is determined that the battery subsystem A needs to be charged.

[0059] When the system determines in step S3 that the PCS energy storage converter 3 is in a reverse discharging working condition, the SOC values of the battery subsystems 4 are collected and sorted, where the lowest battery subsystem SOC value is recorded as SOC_min, the highest battery subsystem SOC value is recorded as SOC_max, and the serial number is recorded as B; when SOC_max-SOC_min>X%, it is determined that the battery subsystem B needs to be discharged.

[0060] The method for charging the battery subsystem that needs to be charged in step S5 is as follows:

[0061] The system controls the ACDC equalizer 1 to output a voltage as the current voltage value of the battery subsystem A, and then controls the PDU power distribution unit 2 to close the corresponding switching switches KpA and KnA; the ACDC equalizer 1 is switched to a power mode to charge the battery subsystem A, and when the battery subsystem SOC_max-SOC_min < Y%, i.e., the charging is completed, the positive and negative switching switches KpA and KnA are disconnected, and then the ACDC equalizer 1 is switched to a control voltage mode, and returns to step S4.

[0062] The method for discharging the battery subsystem to be discharged is as follows: the system controls the PDU power distribution unit 2 to close the corresponding switching switches KpB and KnB; the ACDC equalizer 1 is switched to a power mode to discharge the battery subsystem B to the AC power grid, and when the battery subsystem SOC_max-SOC_min < Y%, i.e., the discharging is completed, the positive and negative switching switches KpB and KnB are disconnected, and then the ACDC equalizer 1 is switched to a control voltage mode, and returns to step S4.

[0063] In the above charging and discharging process, the system (the main control device) controls the action time sequence of each switch as shown in Figure 8 .

[0064] The above-described ACDC type equalization system for a full vanadium redox flow battery and the electric energy equalization method thereof form an efficient charging and discharging loop for each battery subsystem through the ACDC equalizer and the PDU power distribution unit, cooperate with an intelligent main control system, monitor the voltage and electric quantity parameters of the battery cells in real time, and perform feedback control on the ACDC equalizer and the PDU power distribution unit, so as to realize energy balance between the battery cells and automatic and efficient electric quantity equalization of the full vanadium redox flow battery subsystem, and further improve the overall performance and service life of the full vanadium redox flow battery system.

[0065] The above description shows the main features, basic principles, and advantages of the present application. It is obvious for those skilled in the art that the present application is not limited to the details of the above-described exemplary embodiments or examples, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the above-described embodiments or examples should be regarded as exemplary and non-limiting. The scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0066] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made specifically within that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.

Claims

1. An ACDC-type balancing system for a vanadium redox flow battery, characterized in that: The ACDC equalizer (1), the PDU power distribution unit (2), the PCS energy storage converter (3); each battery subsystem (4) of the all-vanadium redox flow battery is connected to the AC power grid (5) through the PCS energy storage converter (3), and a general charge-discharge circuit is formed; the AC power grid (5) is connected to the positive and negative electrodes of each battery subsystem (4) in the all-vanadium redox flow battery through the ACDC equalizer (1) and the PDU power distribution unit (2) in turn, and an equalization charge-discharge circuit is formed, wherein The PDU power distribution unit (2) comprises two front busbars connected to the positive and negative electrodes of the ACDC equalizer (1) and a plurality of rear busbars connected to the positive and negative electrodes of each battery subsystem (4) in turn; in the equalization charge-discharge circuit comprising N battery subsystems (4), the front busbar of the positive electrode of the ACDC equalizer (1) is divided into N branches after the equalizer main switch Q1, and switching switches Kp1…KpN and battery cluster switches Q3…QN+2 are arranged on the corresponding branches; the front busbar of the negative electrode of the ACDC equalizer (1) is divided into N branches after the equalizer main switch Q2, and switching switches Kn1…KnN are arranged on the corresponding branches; the branch with the switching switch Kp1 is connected to the rear busbar on the positive electrode side of the first battery subsystem through the battery cluster switch Q3…the branch with the switching switch KpN is connected to the rear busbar on the positive electrode side of the Nth battery subsystem through the battery cluster switch QN+2; the branch with the switching switch Kn1 is connected to the rear busbar on the negative electrode side of the first battery subsystem through the battery cluster switch Q4…the branch with the switching switch KnN is connected to the rear busbar on the negative electrode side of the Nth battery subsystem through the battery cluster switch QN+3; The system further comprises a master control device (10), the input end of the master control device (10) is connected to the PCS energy storage converter (3) and each battery subsystem (4), and the output end of the master control device (10) is connected to the ACDC equalizer (1) and the PDU power distribution unit (2); during equalization docking, voltage matching is first performed in voltage control mode, and then power control mode is switched.

2. A method for balancing electrical energy of an ACDC type balancing system of a vanadium redox flow battery, characterized in that: The all-vanadium redox flow battery ACDC equalization system of claim 1, the method for realizing energy equalization of the system comprises the following steps, S1: the system closes the equalizer main switches Q1 and Q2 of the PDU power distribution unit (2) and all battery cluster switches; S2: the system starts the ACDC equalizer (1) to establish voltage; S3: the system determines the charge-discharge direction of the battery subsystem (4); S4: the system determines the battery subsystem (4) that needs to be charged or discharged; S5: the system controls the ACDC equalizer (1) to change mode, controls the switching switches of the PDU power distribution unit (2), and charges or discharges the battery subsystem that needs to be charged or discharged.

3. The energy equalization method of the all-vanadium redox flow battery ACDC equalization system according to claim 2, characterized in that: In step S4, the method for determining the battery subsystem that needs to be charged or discharged is: S41: When the system judges that the PCS energy storage converter (3) is in the forward charging condition in step S3, the SOC values of each battery subsystem (4) are collected and sorted, wherein the highest battery subsystem SOC value is recorded as SOC_max, the lowest battery subsystem SOC value is recorded as SOC_min, and the serial number is recorded as A; SOC_max-SOC_min>X% is determined that the battery subsystem A needs to be charged; S42: When the system judges that the PCS energy storage converter (3) is in the reverse discharge condition in step S3, the SOC values of each battery subsystem (4) are collected and sorted, wherein the lowest battery subsystem SOC value is recorded as SOC_min, the highest battery subsystem SOC value is recorded as SOC_max, and the serial number is recorded as B; SOC_max-SOC_min>X% is determined that the battery subsystem B needs to be discharged.

4. The energy balancing method of the ACDC type balancing system of the all-vanadium redox flow battery according to claim 3, characterized in that: The charging method of the battery subsystem in need of charging in step S5 is, S4151: The system controls the ACDC balancer (1) to output a voltage equal to the current voltage value of the battery subsystem A, and then controls the PDU power distribution unit (2) to close the corresponding switching switches KpA and KnA; S4152: The ACDC balancer (1) is switched to the power mode to charge the battery subsystem A, and when the battery subsystem SOC_max-SOC_min<Y%, the charging is completed, the positive and negative switching switches KpA and KnA are disconnected, and then the ACDC balancer (1) is switched to the control voltage mode, and returns to step S4.

5. The energy balancing method of the ACDC type balancing system of the all-vanadium redox flow battery according to claim 3, characterized in that: The discharging method of the battery subsystem in need of discharging in step S5 is, S4251: The system controls the PDU power distribution unit (2) to close the corresponding switching switches KpB and KnB; S4252: The ACDC balancer (1) is switched to the power mode to discharge the battery subsystem B to the AC grid, and when the battery subsystem SOC_max-SOC_min<Y%, the discharging is completed, the positive and negative switching switches KpB and KnB are disconnected, and then the ACDC balancer (1) is switched to the control voltage mode, and returns to step S4.

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