Patent Publication Number: US-2023134800-A1

Title: Vanadium cell soc balanced system

Description:
RELATED APPLICATIONS 
     This application claims priority to and the benefit of Chinese Patent Application No. 202111287458.6 filed on Nov. 2, 2021, the disclosure of which is expressly incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The application relates to the field of vanadium batteries, in particular to a vanadium battery SOC balance system. 
     BACKGROUND 
     The vanadium battery is a storage battery and can store energy by utilizing different chemical potential energies of vanadium ions in different oxidation states. The vanadium battery has the advantages of high charging and discharging efficiency, recyclable electrolyte and the like. 
     It can be appreciated that a plurality of galvanic piles can be connected between a positive electrode electrolyte tank and a negative electrode electrolyte tank, and all galvanic piles are established ties and are together can improve battery capacity, and all galvanic piles are parallelly connected and are together can raise power, consequently adopt earlier the mode of establishing ties again parallelly connected to form the better battery of performance, nevertheless can make the pipeline loss great, and pipeline current increases simultaneously causes the galvanic pile to destroy easily. However, when the liquid path is disconnected, the cell is divided into several groups of parallel-connected cell stacks, and one positive electrolyte tank and one negative electrolyte tank are provided for each group of cell stacks, and after a long-time operation, the SOC may be unbalanced, thereby affecting the battery capacity. 
     SUMMARY 
     In order to improve the problem of SOC unbalance, the application provides a vanadium battery SOC balance system. 
     The SOC balance system of the vanadium redox battery adopts the following technical scheme: 
     a vanadium battery SOC balance system comprises a detection module, a control module, a load module and a plurality of vanadium battery modules; 
     the vanadium battery modules are sequentially connected in series; 
     the detection module is used for detecting and outputting SOC values of the vanadium battery modules; 
     the control module is connected with the detection module and used for receiving the SOC values and connecting the load module into one of the vanadium battery modules according to the SOC values. 
     By adopting the technical scheme, the detection module can detect the SOC values of the vanadium battery modules, the control module can insert the load into one of the vanadium battery modules according to the SOC values, so that the vanadium battery module inserted into the load module can discharge through the load module, the SOC value of the vanadium battery module is further reduced, and the SOC values of the vanadium battery modules are balanced. 
     Optionally, the number of the vanadium redox battery modules is two, and the two vanadium redox battery modules are respectively a first vanadium redox battery module and a second vanadium redox battery module; 
     the first vanadium battery module is connected with the second vanadium battery module in series; 
     the detection module is used for detecting the SOC value of the first vanadium battery module and outputting an SOC1 value, and is used for detecting the SOC value of the second vanadium battery module and outputting an SOC2 value; 
     the control module is connected with the detection module and used for receiving the SOC1 value and the SOC2 value and connecting the load module into the first vanadium battery module or the second vanadium battery module according to the difference value of the SOC1 value and the SOC2 value. 
     Through adopting above-mentioned technical scheme, the detection module can detect the SOC value of first vanadium battery module and second vanadium battery module, and control module can insert the load into first vanadium battery module or second vanadium battery module according to the difference of SOC1 value and SOC2 value for first vanadium battery module and second vanadium battery module can discharge through the load module, and then reach that SOC1 value is close with SOC2 value, so that the SOC value of first vanadium battery module and second vanadium battery module is balanced. 
     Optionally, the load module is respectively connected in parallel to the first vanadium battery module and the second vanadium battery module, and loops of the load module connected with the first vanadium battery module and the second vanadium battery module are respectively provided with at least one controllable switch; 
     the control module is used for outputting a first closing signal when the difference value between the SOC1 value and the SOC2 value is larger than a first preset value, and outputting a second closing signal when the difference value between the SOC1 value and the SOC2 value is smaller than a second preset value; 
     the at least one controllable switch is positioned on a loop of the load module connected with the first vanadium battery module and is used for being closed when receiving a first closing signal; 
     and the at least one controllable switch positioned on the loop of the load module connected with the second vanadium battery module is used for closing when receiving a second closing signal. 
     By adopting the technical scheme, when the difference value between the SOC1 value and the SOC2 value is larger than a first preset value, the first vanadium battery module is connected to the load module to discharge. When the difference value between the SOC1 value and the SOC2 value is smaller than a second preset value, the second vanadium battery module is connected to the load module to discharge, so that the difference value between the SOC1 value and the SOC2 value is controlled within an allowable range, and the SOC is balanced. 
     Optionally, the first vanadium redox battery module and the second vanadium redox battery module both include a positive electrolyte tank, a negative electrolyte tank and a plurality of parallel electric stacks; 
     the anode electrolyte tank is respectively communicated with the anode and the cathode of each electric pile through pipelines, and the cathode electrolyte tank is respectively communicated with the anode and the cathode of each electric pile through pipelines; 
     the load module is connected in parallel with the electric pile of the first vanadium battery module and the electric pile of the second vanadium battery module. 
     Optionally, a loop of the load module connected to the first vanadium redox battery module and a loop of the load module connected to the second vanadium redox battery module have a common branch, and the at least one controllable switch located on the loop of the load module connected to the first vanadium redox battery module and the at least one controllable switch located on the loop of the load module connected to the second vanadium redox battery module form a double-pole double-throw controllable switch. 
     Optionally, the pipeline connected with the anode electrolyte tank and the pipeline connected with the cathode electrolyte tank are both provided with a circulating pump. 
     Through adopting above-mentioned technical scheme, the circulating pump can be with anodal electrolyte and negative pole electrolyte pump sending to each pile. 
     Optionally, the control module includes a processing unit and a control unit; 
     the processing unit is connected with the detection module and is used for receiving the SOC1 value and the SOC2 value, calculating the difference value of the SOC1 value and the SOC2 value and outputting the difference value of the SOC1 value and the SOC2 value; 
     the control unit is connected with the processing unit and used for receiving the difference value between the SOC1 value and the SOC2 value, outputting the first closing signal when the difference value between the SOC1 value and the SOC2 value is larger than the first preset value, and outputting the second closing signal when the difference value between the SOC1 value and the SOC2 value is smaller than the second preset value. 
     Optionally, a balance pipe is further connected between the positive electrode electrolyte tank and the negative electrode electrolyte tank in the first vanadium battery module and between the positive electrode electrolyte tank and the negative electrode electrolyte tank in the second vanadium battery module, and controllable balance valves are respectively arranged on the balance pipes; 
     the liquid level detection device is used for detecting the liquid level in each positive electrolyte tank and each negative electrolyte tank and outputting liquid level detection signals; 
     the control unit is also connected with a liquid level detection device, is used for receiving a liquid level detection signal and outputting a starting signal when the difference value of the liquid level values reflected by the liquid level detection signal is smaller than a difference preset value; the liquid level detection device is also used for outputting an adjusting signal when the difference value of the liquid level values reflected by the liquid level detection signal is greater than a difference preset value; 
     the controllable balance valve is connected with the control unit and is used for being opened when the adjusting signal is received; 
     the detection module is further used for detecting the first vanadium battery module and the second vanadium battery module when receiving a starting signal. 
     By adopting the technical scheme, when the liquid level difference between the positive electrolyte and the negative electrolyte is too large, the balance valve needs to be opened to balance the liquid levels of the positive electrolyte and the negative electrolyte, and then the SOC value of the first vanadium battery module and the SOC value of the second vanadium battery module are detected. 
     In summary, the present application includes at least one of the following beneficial technical effects: 
     1. the detection module can detect the SOC values of the first vanadium battery module and the second vanadium battery module, the control module can insert loads into the first vanadium battery module or the second vanadium battery module according to the difference value of the SOC1 value and the SOC2 value, the first vanadium battery module and the second vanadium battery module can discharge through the load module, the SOC1 value is close to the SOC2 value, and the SOC values of the first vanadium battery module and the second vanadium battery module are balanced. 
     Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a system schematic diagram of a vanadium redox battery SOC balancing system according to an embodiment of the present application. 
         FIG.  2    is a schematic circuit diagram of a vanadium redox battery SOC balancing system according to an embodiment of the present application. 
         FIG.  3    is another circuit schematic diagram of the vanadium redox battery SOC balancing system according to the embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to  FIG.  1 - 3    and the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. 
     The embodiment of the application discloses a vanadium redox battery SOC balance system. Referring to  FIGS.  1  and  2   , the vanadium battery SOC balancing system includes a detection module  1 , a control module  2 , a load module  5 , and a plurality of vanadium battery modules. The SOC values of the vanadium battery modules are detected through the detection module  1 , so that the control module  2  can control the load module  5  to be connected into one of the vanadium battery modules according to the SOC values to consume the electric energy of the vanadium battery modules, and further the SOC values of the vanadium battery modules are balanced. 
     Specifically, two vanadium battery modules may be provided. When there are two vanadium battery modules in the vanadium redox battery SOC balance system of the present application, the two vanadium battery modules are a first vanadium battery module  3  and a second vanadium battery module  4 , respectively, for the purpose of differentiation. Further, the detection module  1  detects the SOC values of the first vanadium battery module  3  and the second vanadium battery module, so that the control module  2  can control the first vanadium battery module  3  or the second vanadium battery module  4  to be connected to the load module  5  to consume electric energy according to the difference between the SOC values of the first vanadium battery module  3  and the second vanadium battery module  4 , and further the SOC values of the first vanadium battery module  3  and the second vanadium battery module  4  are balanced. 
     The first vanadium battery module  3  is connected in series with the second vanadium battery module  4 . The first vanadium redox battery module  3  and the second vanadium redox battery module  4  both comprise a positive electrolyte tank  31  and a negative electrolyte tank  32  and a plurality of parallel electric piles  33 , and the two groups of parallel electric piles  33  are connected in series. Since the first vanadium battery module  3  and the second vanadium battery module  4  are connected in the same manner, the first vanadium battery module  3  is taken as an example in the embodiment of the present application. 
     The positive electrolyte tank  31  and the negative electrolyte tank  32  in the first vanadium redox battery module  3  are respectively communicated with the positive electrode and the negative electrode of each electric pile  33  through pipelines  6 , and circulating pumps  7  are further arranged on the pipelines  6  communicated with the positive electrolyte tank  31  and the pipelines  6  communicated with the negative electrolyte tank  32 , so that positive electrolyte can circulate between the positive electrolyte tank  31  and each electric pile  33 , and similarly, negative electrolyte can circulate between the negative electrolyte tank  32  and each electric pile  33 . 
     Moreover, a balance pipe is provided between the positive electrode electrolyte tank  31  and the negative electrode electrolyte tank  32 , and the balance pipe enables the positive electrode electrolyte tank  31  and the negative electrode electrolyte tank  32  to be communicated. Of course, the balance pipe is further provided with a controllable balance valve  8 , so that when the liquid level difference between the positive electrolyte tank  31  and the negative electrolyte tank  32  is large, the controllable balance valve  8  is controlled to open, so that the liquid levels in the positive electrolyte pipe and the negative electrolyte tank  32  are consistent. 
     The load modules  5  are respectively connected in parallel to the first vanadium battery module  3  and the second vanadium battery module  4 . Specifically, the load module  5  includes load resistors R connected in parallel to the cell stacks  33  of the first vanadium battery module  3  and the cell stacks  33  of the second vanadium battery module  4 , respectively. At least one controllable switch is respectively arranged on a loop of the load resistor R connected with the first vanadium battery module  3  and the second vanadium battery module  4 . The load resistor R can be switched into the first vanadium battery module  3  or the second vanadium battery module  4  by controlling the closed state of these controllable switches. 
     It is worth noting that the number of controllable switches provided on the circuit where the load resistor R is connected to the first vanadium battery module  3  and the second vanadium battery module  4  depends on the connection manner of the load resistor R to the first vanadium battery module  3  and the second vanadium battery module  4 . Wherein, a controllable switch or two controllable switches can be respectively arranged on the loop of the load resistor R connected with the first vanadium battery module  3  and the second vanadium battery module  4 . 
     Referring to  FIG.  3   , in particular, a load resistor R is connected in series with a controllable switch K 1 , and the load resistor R and the controllable switch K 1  are connected in parallel with the cell stack  33  in the first vanadium battery module  3  and the cell stack  33  in the second vanadium battery module  4 , respectively. Meanwhile, a controllable switch K 2  is further arranged on a branch of the first vanadium battery module  3  where the stack  33  is connected with the controllable switch K 1  or a branch of the first vanadium battery module connected with the load resistor R. Similarly, a controllable switch K 3  is further provided on the branch of the second vanadium battery module  4  where the stack  33  is connected to the controllable switch K 1  or the branch connected to the load resistor R. Obviously, the controllable switch K 1  and the controllable switch K 2  are closed at the same time, and the controllable switch K 3  is opened, so that the load resistor R is connected to the first vanadium battery module  3 ; accordingly, the controllable switch K 1  and the controllable switch K 3  are closed at the same time, and the controllable switch K 2  is opened, so that the load resistor R is connected to the second vanadium battery module  4 . Of course, the controllable switch K 1 , the controllable switch K 2  and the controllable switch K 3  are all turned off at the same time, i.e. the load resistor R is not switched in. 
     Referring to  FIG.  2   , further, in the present application, in addition to the branch where the load resistor R is located, the loops where the load resistor R is connected to the first vanadium battery module  3  and the second vanadium battery module  4  also have a common branch. Meanwhile, a controllable switch is respectively arranged on the loops of the load resistor R connected with the first vanadium battery module  3  and the second vanadium battery module  4 . Preferably, the controllable switches respectively disposed on the loops connecting the load resistor R with the first vanadium battery module  3  and the second vanadium battery module  4  may be regarded as the same controllable switch K 4 , and the controllable switch K 4  may be a double-pole double-throw switch. Specifically, two fixed ends of the controllable switch K 4  are connected to both ends of the load resistor R, respectively. And a common branch and a loop of the load resistor R connected with the first vanadium battery module  3  and the second vanadium battery module  4  are provided with a connecting end except the common branch. Two movable ends of the controllable switch  4  can be connected with the connection ends on the common branch, and are connected with any connection end except the common branch on a loop where the load resistor R is connected with the first vanadium battery module  3  and the second vanadium battery module  4  to form a loop, so that the load resistor R is connected into the first vanadium battery module  3  or the second vanadium battery module  4 . Of course, the two active ends of the controllable switch  4  are not connected to the three terminals, and then the load resistor R is not connected to the first vanadium battery module  3  and the second vanadium battery module  4 . 
     Referring to  FIGS.  1  and  2   , generally, before SOC detection is performed on two sets of the positive electrolyte tank  31  and the negative electrolyte tank  32 , it is first necessary to make the liquid levels in the two sets of the positive electrolyte tank  31  and the negative electrolyte tank  32  uniform. Therefore, the vanadium redox battery SOC balance system of the application also comprises a liquid level detection device  9 . 
     The liquid level detection device  9  is used for detecting the liquid level in each positive electrolyte tank  31  and each negative electrolyte tank  32  and outputting a liquid level detection signal. Preferably, the liquid level detection device  9  is a liquid level sensor. Of course, a measuring instrument having a function of measuring a liquid level, such as a liquid level meter, may also be employed. 
     The control module  2  is connected with the liquid level detection device  9 , is used for receiving the liquid level detection signal and outputting a starting signal when the difference value of the liquid level values reflected by the liquid level detection signal is smaller than the preset difference value; and the liquid level detection circuit is also used for outputting an adjusting signal when the difference value of the liquid level values reflected by the liquid level detection signal is greater than the preset difference value. Wherein the control module  2  comprises a processing unit  21  and a control unit  22 . 
     The control unit  22  is connected with the liquid level detection device  9 , and is used for receiving the liquid level detection signal and outputting a starting signal when the difference value of the liquid level values reflected by the liquid level detection signal is smaller than the preset difference value; and the liquid level detection circuit is also used for outputting an adjusting signal when the difference value of the liquid level values reflected by the liquid level detection signal is greater than the preset difference value. 
     It should be noted that before SOC detection is performed on the two sets of the positive electrolyte tank  31  and the negative electrolyte tank  32 , the liquid level difference between the two sets of the positive electrolyte tank  31  and the negative electrolyte tank  32  may be zero, may be smaller, and may be larger. In general, it is allowable that the initial difference between the liquid level values of the two sets of the positive electrolyte tank  31  and the negative electrolyte tank  32  is small, i.e. the later operation such as SOC balancing is not greatly affected. Therefore, when the difference value of the liquid level values reflected by the liquid level detection signals is smaller than the preset difference value, the control unit  22  can output a start signal. Specifically, the liquid level difference is a difference between the liquid levels of the positive electrode electrolyte tank  31  and the negative electrode electrolyte tank  32  of the same group. In the present application, the difference preset value is 20 cm. Of course, the preset value of the difference value can be adaptively adjusted according to actual conditions. 
     The controllable balancing valve  8  is connected to the control unit  22  for receiving the adjustment signal and is opened upon receipt of the adjustment signal. At this time, the positive electrode electrolyte tank  31  and the negative electrode electrolyte tank  32  of the same group are communicated, and the liquid in one electrolyte tank with a higher liquid level flows to the other electrolyte tank, so that the liquid levels of the two electrolyte tanks are the same. When the adjustment of the liquid in the two electrolyte tanks is completed, the controllable balance valve  8  is closed. Specifically, the liquid levels of the positive electrolyte tank  31  and the negative electrolyte tank  32  may be detected by the liquid level detection device  9 , and when the liquid phases of the positive electrolyte tank  31  and the negative electrolyte tank  32  are the same, the control unit  22  controls the controllable balance valve  8  to close. Of course, it is also possible to set the opening time for the controllable balance valve  8 , and after the control unit  22  controls the controllable balance valve  8  to open, and after the controllable balance valve  8  is opened for a preset time period, the controllable balance valve  8  is automatically closed. The above description provides only two control methods as references, and does not limit other control methods. Accordingly, the control unit  22  outputs an activation signal after the controllable balancing valve  8  has closed. 
     The detection module  1  is connected to the control unit  22 , and is configured to receive a start signal, and detect the first vanadium battery module  3  and the second vanadium battery module  4  when receiving the start signal. Specifically, the detection module  1  is used for detecting the SOC value of the first vanadium battery module  3  and outputting an SOC1 value; and is used for detecting the SOC value of the second vanadium battery module  4  and outputting the SOC2 value. It should be noted that the detection module  1  cannot directly detect the SOC1 value of the first vanadium battery module  3  and the SOC2 value of the second vanadium battery module  4 , so that the detection module  1  actually detects the open-circuit voltage, i.e., OCV, between the two poles of the first vanadium battery module  3  or the second vanadium battery module  4 , and further converts the open-circuit voltage into a corresponding SOC value. 
     Further, the processing unit  21  is connected to the detection module  1 , and is configured to receive the SOC1 value and the SOC2 value, calculate a difference between the SOC1 value and the SOC2 value, and output a difference between the SOC1 value and the SOC2 value. 
     The control unit  22  is connected to the processing unit  21 , and is configured to receive a difference between the SOC1 value and the SOC2 value, and to output a first closing signal when the difference between the SOC1 value and the SOC2 value is greater than a first preset value, and to output a second closing signal when the difference between the SOC1 value and the SOC2 value is less than a second preset value. The first closing signal is used for controlling at least one controllable switch on a loop connecting the load resistor R and the first vanadium battery module  3  to be closed and other controllable switches to be opened, and the second closing signal is used for controlling at least one controllable switch on a loop connecting the load resistor R and the second vanadium battery module  4  to be closed and other switches to be opened. 
     It can be understood that the difference between the SOC1 value and the SOC2 value is greater than the first preset value, which indicates that the SOC1 value of the first vanadium battery module  3  is greater than the SOC2 value of the second vanadium battery module  4 , and the difference between the SOC1 value and the SOC2 value is greater than the first preset value. At this time, the control unit  22  needs to control at least one controllable switch on the loop where the load resistor R is connected with the first vanadium battery module  3  to be closed, and simultaneously control other controllable switches to be opened, so that the load resistor R is connected to the first vanadium battery module  3  to consume the energy of the first vanadium battery module  3  through the load resistor R, thereby reducing the SOC1 value. 
     Similarly, the difference between the SOC1 value and the SOC2 value is smaller than the second preset value, which can indicate that the SOC1 value of the first vanadium battery module  3  is smaller than the SOC2 value of the second vanadium battery module  4 , and the difference between the SOC1 value and the SOC2 value is smaller than the second preset value, where it should be noted that the second preset value is a negative number. At this time, the control unit  22  needs to control at least one controllable switch on the loop connecting the load resistor R and the second vanadium battery module  4  to be closed, and simultaneously control other controllable switches to be opened, so that the load module  5  is connected to the second vanadium battery module  4  to consume the energy of the second vanadium battery module  4  through the load resistor R, thereby reducing the SOC2 value, and achieving the effect of balancing the SOC values of the first vanadium battery module  3  and the second vanadium battery module  4 . 
     Besides, when the difference between the SOC1 value and the SOC2 value is greater than the second preset value and less than the first preset value, it indicates that the difference between the SOC1 value of the first vanadium battery module  3  and the SOC2 value of the second vanadium battery module  4  is within the allowable range. At this time, the control unit  22  controls all the controllable switches to be turned off so that the load resistor R is not connected into the first vanadium battery module  3  and the second vanadium battery module  4 . 
     In the present application, the first preset value is 2%, and the second preset value is −2%, and of course, the first preset value and the second preset value can be adaptively designed according to actual situations. The liquid level detection process, the SOC detection process and the SOC balance process are processes of starting and preprocessing stages of the vanadium battery SOC balance system. 
     Further, after the SOC balancing system enters a normal operating state, the first preset value is changed to 5%, and the second preset value is changed to −5%, that is, when the difference between the SOC1 value and the SOC2 value is greater than 5%, the load resistor R is connected to the first vanadium battery module  3 , when the difference between the SOC1 value and the SOC2 value is less than −5%, the load resistor R is connected to the second vanadium battery module 4, and when the difference between the SOC1 value and the SOC2 value is greater than −5% and less than 5%, the connection state of the load resistor R with the first vanadium battery module  3  and the second vanadium battery module  4  is maintained. 
     In addition, in the art, the detection module  1  and the control module  2  generally employ an EMS controller. 
     When there are three or more vanadium battery modules in the vanadium battery SOC balance system of the present application, the difference from the vanadium battery SOC balance system having two vanadium battery modules is only that: and the vanadium battery modules are sequentially connected in series. Similarly, the parallel electric stacks in each vanadium battery module are connected together in series in sequence. 
     At this time, load resistors R are respectively connected in parallel to the cell stacks of each vanadium battery module. And at least two controllable switches are respectively arranged on a loop of the load resistor R connected with each vanadium battery module. The load resistor R can be connected to one of the vanadium battery modules by controlling the closed state of the controllable switches. The connection mode of the load resistor R and the plurality of vanadium battery modules can refer to the connection mode of the load resistor R and the first vanadium battery module  3  and the second vanadium battery module  4 . It is worth mentioning that the controllable switch in series with the load resistor R is a common controllable switch in the loop where the load resistor R is connected to each vanadium battery module. 
     The processing unit  21  is configured to receive all the SOC values, compare all the SOC values to determine a maximum SOC value and a minimum SOC value, and then calculate and output a difference between the maximum SOC value and the minimum SOC value. 
     The control unit  22  is configured to receive a difference between the maximum SOC value and the minimum SOC value, and output a third close signal when the difference is greater than a first preset value. The third closing signal is used for controlling the two controllable switches on a loop, connected with the load resistor R, of the vanadium battery module corresponding to the maximum SOC value to be closed, and simultaneously controlling the other controllable switches to be opened, so that the load resistor R is connected to the vanadium battery module corresponding to the maximum SOC value, the energy of the vanadium battery module is consumed through the load resistor R, and the SOC value of the vanadium battery module is reduced. 
     And when the difference value between the maximum SOC value and the minimum SOC value is smaller than the first preset value, the difference value of the SOC values of any two vanadium battery modules is in an allowed range. At this time, the control unit  22  controls all the controllable switches to be turned off, so that the load resistor R is not connected into any vanadium battery module. 
     Similarly, when the SOC balancing system enters a normal operating state, the first preset value is changed to 5%, that is, the difference between the maximum SOC value and the minimum SOC value is greater than 5%, the load resistor R is connected to the vanadium battery module corresponding to the maximum SOC value, and when the difference between the maximum SOC value and the minimum SOC value is less than 5%, the connection state between the load resistor R and the vanadium battery modules is maintained. 
     The implementation principle of the SOC balance system of the vanadium redox battery in the embodiment of the application is as follows: and simultaneously connecting the load module  5  with a plurality of vanadium battery modules, and arranging a controllable switch on a loop of the load module  5  connected with each vanadium battery module. The SOC values of the vanadium battery modules are detected through the detection module  1 , and the control module  2  accesses the load module  5  into one of the vanadium battery modules according to the SOC values, so that the vanadium battery modules can consume energy through the load module  5 , and further SOC value balance is achieved. 
     The foregoing is a preferred embodiment of the present application and is not intended to limit the scope of the application in any way, and any features disclosed in this specification (including the abstract and drawings) may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features. 
     It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.