Second-life battery energy storage system and SOC balancing control method and related device

Abstract

The present application relates to a SOC balancing control method. In view of the technical problem that the SOC balancing control method of the current energy storage system has a large control deviation due to the different attenuation degrees of the new and old batteries, a second-life battery energy storage system and its SOC balancing control method and related devices are provided, and a healthy state of charge is proposed. The specific control logic is determined according to the absolute value of the deviation between the healthy state of charge of each battery module and . In order to improve the SOC balancing speed, the present application determines the specific operation mode of the second-life battery energy storage system according to the differences in the healthy state of charge of each battery module during the operation of the second-life battery energy storage system. Therefore, the present application performs SOC balancing according to the battery attenuation degree, and truly realizes SOC balancing for second-life batteries.

Description

Technical Field

[0001] The present application relates to a SOC balancing control method, and specifically to a second-life battery energy storage system and its SOC balancing control method and related devices. Background Art

[0002] Realizing the reuse of second-life batteries has become a concern for the industry and academia. If retired batteries can be kept consistent, it will promote industrial development and technological progress. At the same time, energy storage systems can effectively solve the spatiotemporal distribution of energy, and therefore have been widely used in the industry, especially electrochemical energy storage technology has been rapidly developed. During the operation of the energy storage system, batteries may have abnormal failures. In the current mainstream energy storage system, the degree of battery attenuation in each battery cluster remains relatively consistent. If any battery in the cluster is abnormal, all battery PACKs need to be replaced, which will cause great economic losses.

[0003] In summary, it is of great economic and technical necessity to solve the engineering and technical problems in the application of new energy second-life batteries in energy storage systems, as well as the engineering and technical problems in the mixed use of new and old battery modules in the operation and maintenance of energy storage systems.

[0004] The Chinese invention patent with publication number CN111725876A discloses a SOC balancing control method based on droop control, which balances the SOC (State of Charge) for two working conditions: 1. Different battery capacities and consistent initial SOC: each converter configures the charge and discharge power according to the capacity ratio to achieve SOC balance; 2. The battery capacities are the same and the initial SOCs are inconsistent: the charge and discharge power is allocated according to the size of the SOC to achieve SOC balance. However, the corresponding balancing strategy method for different attenuation degrees and inconsistent SOCs is not analyzed.

[0005] The Chinese invention patent with publication number CN110525269A discloses a battery pack balancing control method of SOC, which realizes battery pack balancing based on SOC estimation results and adopts model predictive control algorithm, improves the inconsistency between cells in the battery pack, and effectively reduces battery balancing time and energy consumption. By identifying the parameters of the battery equivalent circuit model, a battery mathematical model is constructed, and the balancing control of the control target SOC is achieved through the model prediction algorithm. However, it is believed that whether it is a new battery or a battery that has been attenuated for a certain period of time, the SOC is always 0-1. For batteries with different attenuation degrees, the SOC balancing proposed in the application cannot achieve the actual balancing effect.

[0006] The Chinese invention patent with the publication number CN114844162A discloses a method for balancing the SOC of multiple cluster batteries in an energy storage system. For multiple clusters of energy storage units, PCS (Power Conversion System) is used to connect them in parallel on the AC side. Each cluster of battery units is connected to the PCS. In this energy storage system structure, the charge and discharge power of each cluster is distributed through EMS (Energy Management System). For battery clusters with large SOC differences, some battery clusters will be in a discharging state, while other battery clusters will be in a charging state. The premise of this method is that the batteries in the cluster have a high consistency, and the SOC of each battery in the cluster is almost the same. However, with the application of battery charging and discharging, the batteries in the cluster will undergo differential changes, which will increase the SOC deviation. This method cannot be balanced for such situations. Summary of the invention

[0007] The present application aims to provide a second-life battery energy storage system and its SOC balancing control method and related devices, in view of the technical problem that the SOC balancing control method of the current energy storage system has a large control deviation due to the different attenuation degrees of the new and old batteries.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions:

[0009] In a first aspect, the present application proposes a SOC balancing control method for a cascade battery energy storage system, comprising:

[0010] According to the battery module and , calculate the healthy state of charge of each battery module ;

[0011] Calculate the battery module average value ;

[0012] Determine each battery module in turn and The absolute value of the deviation Is it less than or equal to A? If so, the cascade battery energy storage system operates in PWM mode according to the healthy state of charge balancing algorithm. Otherwise:

[0013] (1) If the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are placed in PWM charging mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0014] (2) If the battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converter is in PWM discharge mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0015] Among them, A is the first balance target time control parameter, B is the second balance target time control parameter, A and B are both determined according to the balance target time requirements of the cascade battery energy storage system, and A>B.

[0016] Furthermore, the healthy state of charge balancing algorithm includes:

[0017] If the cascade battery energy storage system is in charging mode, then:

[0018] Get the maximum The bus voltage of the DC / DC converter corresponding to the battery module , and maximize The DC / DC converter corresponding to the battery module operates according to the minimum duty cycle D of the cascade battery energy storage system;

[0019] According to the total bus-side voltage and bus-side voltage of the cascade battery energy storage system , determine the bus-side voltage of the remaining DC / DC converters ;

[0020] According to the bus voltage The remaining DC / DC converters correspond to the battery modules , obtain the bus-side voltage control target of each remaining DC / DC converter;

[0021] The bus-side voltage of each remaining DC / DC converter is operated according to the corresponding bus-side voltage control target of the remaining DC / DC converter;

[0022] If the cascade battery energy storage system is in discharge mode, then:

[0023] Get the minimum The bus voltage of the DC / DC converter corresponding to the battery module , and minimize The DC / DC converter corresponding to the battery module operates according to the minimum duty cycle D of the cascade battery energy storage system;

[0024] According to the total bus-side voltage and bus-side voltage of the cascade battery energy storage system , determine the bus-side voltage of the remaining DC / DC converters ;

[0025] According to the bus voltage The remaining DC / DC converters correspond to the battery modules , obtain the bus-side voltage control target of each remaining DC / DC converter;

[0026] The bus-side voltage of each remaining DC / DC converter is operated according to the corresponding bus-side voltage control target of the remaining DC / DC converter.

[0027] Furthermore, the calculation obtains the healthy state of charge of each battery module ,include:

[0028]

[0029] in, For the The healthy state of charge of each battery module, For the Battery modules , For the Battery modules , For each battery module Maximum value;

[0030] The calculation obtains the average value ,include:

[0031]

[0032] in, is the total number of battery modules.

[0033] Furthermore, the total bus side voltage and bus side voltage of the cascade battery energy storage system , determine the bus-side voltage of the remaining DC / DC converters ,include:

[0034]

[0035] in, is the total voltage on the bus side of the cascade battery energy storage system;

[0036] According to the bus side voltage The remaining DC / DC converters correspond to the battery modules , the bus-side voltage control targets of the remaining DC / DC converters are obtained, including:

[0037]

[0038] in, The remaining DC / DC converters The DC / DC converter bus side voltage control target, The remaining DC / DC converters DC / DC converters correspond to battery modules .

[0039] Furthermore, the first equalization target time control parameter A is 5%, and the second equalization target time control parameter B is 2%.

[0040] In the second aspect, the present application proposes a SOC balancing control system for a cascade battery energy storage system, comprising:

[0041] Healthy charge module, used to and , calculate the healthy state of charge of each battery module ;

[0042] The average value module is used to calculate the average value of each battery module. average value ;

[0043] The judgment module is used to judge each battery module in turn. and The absolute value of the deviation Is it less than or equal to A? If so, the cascade battery energy storage system operates in PWM mode according to the healthy state of charge balancing algorithm. Otherwise:

[0044] (1) If the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are placed in PWM charging mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0045] (2) If the battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converter is in PWM discharge mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0046] Among them, A is the first balance target time control parameter, B is the second balance target time control parameter, A and B are both determined according to the balance target time requirements of the cascade battery energy storage system, and A>B.

[0047] In a third aspect, the present application provides an electronic device, comprising:

[0048] Memory for storing computer programs;

[0049] A processor is used to implement the steps of the above-mentioned SOC balancing control method for the cascade battery energy storage system when executing the computer program.

[0050] In a fourth aspect, the present application proposes a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned SOC balancing control method of the cascade battery energy storage system are implemented.

[0051] In a fifth aspect, the present application proposes a second-life battery energy storage system, comprising a PCS, multiple DC / DC converters and multiple battery modules; the second-life battery energy storage system adopts the above-mentioned second-life battery energy storage system SOC balancing control method.

[0052] Compared with the prior art, this application has the following beneficial effects:

[0053] This application proposes a SOC balancing control method for a battery energy storage system, and proposes a healthy state of charge , according to the healthy state of charge of each battery module and The absolute value of the deviation Determine the specific control logic. In order to improve the SOC balancing speed, this application is based on the healthy charge state of each battery module in the operation of the cascade battery energy storage system. The difference determines the specific operation mode of the echelon battery energy storage system. Therefore, this application performs SOC balancing according to the degree of battery attenuation, and truly realizes SOC balancing for echelon batteries.

[0054] The present application also proposes a SOC balancing control system for a second-life battery energy storage system, an electronic device, a computer-readable storage medium and a second-life battery energy storage system, which have all the advantages of the above-mentioned SOC balancing control method for a second-life battery energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0056] Figure 1 This is a first flow chart of a SOC balancing control method for a second-life battery energy storage system according to the present application;

[0057] Figure 2 A schematic diagram of a main circuit structure of a second-life battery energy storage system;

[0058] Figure 3 It is a signal flow diagram of a cascade battery energy storage system;

[0059] Figure 4 This is a second flow chart of a SOC balancing control method for a second-life battery energy storage system of the present application;

[0060] Figure 5 A flow chart of a healthy state of charge balancing algorithm for this application;

[0061] Figure 6 A schematic diagram of the SOC balancing control system of the cascade battery energy storage system of the present application. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0063] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0064] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0065] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invented product is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0066] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0067] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0068] Second-life batteries are batteries that have been retired from their original application scenarios but still have residual capacity and use value. Although these batteries are usually no longer suitable for use in high-demand environments, they can still be used again in lower-demand application scenarios after proper evaluation, testing, reorganization and reuse, thereby achieving efficient use of resources and sustainable development of the environment.

[0069] For example, with the rapid development of the new energy vehicle industry, a large number of automotive lithium battery packs are facing retirement and scrapping. Among these retired battery packs, not all batteries are in a scrapped state. Due to the consistency problem of the battery pack, usually only individual units of the battery are scrapped, while many batteries in the pack are still in a good life cycle and have a high utilization value. Through a reasonable cascade utilization plan, these batteries can continue to play a role in waste heat, reduce resource waste, and reduce environmental pollution.

[0070] At the same time, with the development of new energy power generation technology, the most effective technical solution to the problems of "abandoning wind" and "abandoning light" is the application of energy storage technology. The energy storage system can effectively solve the temporal and spatial distribution of energy, especially the electrochemical energy storage technology has been rapidly developed. During the operation of the energy storage system, the battery may have abnormal failures. In the current mainstream energy storage system, the degree of battery attenuation in each battery cluster remains relatively consistent. If any battery in the cluster is abnormal, all battery PACKs (battery packs) need to be replaced, which will cause great economic losses. If only the battery module or battery PACK corresponding to the abnormal battery can be replaced, without replacing the entire cluster with a new battery PACK, it can not only reduce the workload of on-site maintenance, but also reduce the investment cost of the energy storage system. Therefore, the mixed use of new and old battery modules will be an engineering and technical issue that needs to be considered in future energy storage systems.

[0071] Based on the above situation, the present application proposes a cascade battery energy storage system and its SOC balancing control method and related devices. The present application is described in detail below in conjunction with embodiments and drawings.

[0072] like Figure 1 As shown, it is a first flow chart of a SOC balancing control method of a cascade battery energy storage system of the present application, which may include:

[0073] S101, according to each battery module and , calculate the healthy state of charge of each battery module .

[0074] It should be noted that SOC (State Of Charge) refers to the ratio of the amount of charge that can be extracted from the battery cell at a specific time point to the total capacity of the battery, reflecting the remaining power state of the battery. SOH (State Of Health) refers to the health state, which is used to describe the health state of the battery and reflects the current rated capacity of the battery, that is, the ratio of the current rated capacity to the initial rated capacity. New batteries are A fully dead battery would have a charge level of 0%. , full spelling Healthy State of charge, means the charge state taking the health status into consideration.

[0075] S102, calculate and obtain the average value .

[0076] S103, determine the battery modules in turn. and The absolute value of the deviation Is it less than or equal to A? If so, the cascade battery energy storage system operates in PWM mode according to the healthy state of charge balancing algorithm. Otherwise:

[0077] (1) If the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are placed in PWM charging mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0078] (2) If the battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converter is in PWM discharge mode until the absolute value of the deviation of the corresponding battery module is When the voltage is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode.

[0079] Among them, A is the first balance target time control parameter, B is the second balance target time control parameter, A and B are both determined according to the balance target time requirements of the cascade battery energy storage system, and A>B.

[0080] The settings of A and B actually determine when the cascade battery energy storage system can reach the balance threshold. In practical applications, the values ​​of A and B can be set according to the specific requirements of SOC balance control. In order to improve the utilization rate of electric energy in the cascade battery energy storage system and the consistency control of battery modules, the values ​​of A and B can be set smaller, otherwise they can be appropriately larger.

[0081] During the charge and discharge process, very complex electrochemical reactions usually take place inside the electrochemical energy storage battery, which is affected by differences in external ambient temperature, heat dissipation conditions, and other electromagnetic conditions during operation. Even after consistency screening, the battery module will decay in an anisotropic manner as the number of charge and discharge times increases.

[0082] like Figure 2As shown, it is a schematic diagram of the main circuit structure of a second-life battery energy storage system, including a battery module composed of N second-life batteries, and each battery module is connected to a corresponding DC / DC converter. In practical applications, the DC / DC converter can be an isolated converter or a non-isolated converter. In addition, whether it is a boost converter or a buck converter, it can also be applied to the second-life battery energy storage system of the present application. The DC / DC converter bus side has a controllable switch K2. On the one hand, when the DC / DC converter fails, the controllable switch K2 can be used to exit, so that the second-life battery energy storage system can still operate normally. On the other hand, the controllable switch K2 can also participate in the system balancing control in the second-life battery energy storage system, so that the corresponding DC / DC converter can be bypassed. Figure 1 In the main circuit structure shown in the figure, the DC / DC converters are cascaded to form DC+ (positive DC power supply) and DC- (negative DC power supply) with higher DC voltage specifications, and the corresponding DC side voltage The DC side of the PCS (Power Conversion System) is connected, and the AC side of the PCS is connected to the power grid.

[0083] like Figure 3 The figure shows a signal flow diagram of a cascade battery energy storage system. The BMU (Battery Management Unit) is used to sample the voltage and temperature of each cell in the battery module and upload it to the main control unit (RCU, Room Control Unit) of the BMS (Battery Management System) by communication. The RCU sends the relevant data of the cells in the cascade battery energy storage system to the system controller by communication. The DC / DC converter communicates with the system controller in real time, and sends information such as the working mode and bus side voltage control target of the cascade battery energy storage system. At the same time, the DC / DC converter reports the operating status and operating parameter data of each DC / DC converter to the system controller. The PCS communicates and interacts with the system controller, sends the PCS operating mode, start and stop instructions, and operating power, and the PCS reports the operating status and fault information. The system controller exchanges data with the operating information of each functional unit in the system and the instructions issued by the upper EMS (Energy Management System) and controls the generation and conversion of operating instructions.

[0084] For the SOC balancing control method of the cascade battery energy storage system of the present application, the battery modules are connected to the DC / DC converters accordingly, and the bus-side cascade of each DC / DC converter constitutes an energy storage system. The SOC balancing control at the module level is achieved through power regulation and distribution of the DC / DC converter.

[0085] The common feature of mixed use of second-hand batteries and new and old batteries is that the battery attenuation degree is different. , the general SOC balancing algorithm generally only considers One factor, not considered Factors that influence The prerequisite for achieving balance is that all batteries have the same degree of attenuation. However, in the energy storage system, the attenuation of batteries is unavoidable, especially the simple engineering application problem of cascade batteries and the replacement of old and new batteries in subsequent operation and maintenance. The SOC balancing control method for the cascade battery energy storage system of this application is adopted to achieve true SOC balancing, and the SOC balancing effect can be achieved under any working conditions.

[0086] In order to improve the SOC balancing speed, according to the healthy charge state of each battery module in operation Differences determine the operation mode of the cascade battery energy storage system, and the If the deviation exceeds the threshold value A (in practical applications, A can be set to 5%), the battery module in the charging mode will be The largest battery module is bypassed, and the other battery modules are charged. In the discharge mode, the battery modules are The smallest battery module is bypassed, and the other battery modules are discharged; when each battery module (including the bypass exit battery module) The deviation is within the threshold value B (in actual application, B can be set to 2%), and the battery module that was previously bypassed is put into operation; the DC / DC converters corresponding to all battery modules operate in PWM mode and can operate according to the healthy charge state balancing algorithm.

[0087] like Figure 4 As shown, it is a second flow chart of a SOC balancing control method of a cascade battery energy storage system of the present application, which may include:

[0088] S201, each battery module and As input information, the healthy state of charge of each battery module is obtained through HSOC calculation .

[0089] The specific calculation can be done using the following formula:

[0090]

[0091] in, For the The healthy state of charge of each battery module, For the Battery modules , For the Battery modules , For each battery module Maximum value.

[0092] S202, calculate and obtain the average value

[0093]

[0094] in, is the total number of battery modules.

[0095] S203, calculating the and average value The absolute value of the deviation.

[0096]

[0097] in, For the Battery modules and average value The absolute value of the deviation.

[0098] S204, traverse all , judge in turn Is it satisfied? If satisfied, execute step S205, otherwise, execute step S207.

[0099] S205, when the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are placed in PWM charging mode until the absolute value of the deviation of the corresponding battery module is If it is less than B, then go to step S206.

[0100] When the battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converter is in PWM discharge mode until the absolute value of the deviation of the corresponding battery module is If it is less than B, then go to step S206.

[0101] S206, causing the DC / DC converter in bypass operation to exit the bypass mode and operate in a PWM charging or discharging mode.

[0102] S207, all DC / DC converters are charged or discharged in PWM operation mode, and the cascade battery energy storage system operates in PWM (Pulse Width Modulation) mode according to a healthy state of charge balancing algorithm.

[0103] like Figure 5 As shown, a flow chart of a healthy state of charge balancing algorithm is shown, which can be executed in the following way:

[0104] (1) Determine the operating mode of the battery energy storage system. If it is a charging mode, execute step (2); if it is a discharging mode, execute step (3);

[0105] (2) Traversing the healthy charge state of the battery modules in the cascade battery energy storage system , get the maximum , and the maximum The corresponding DC / DC converter operates according to the minimum duty cycle D of the cascade battery energy storage system. At the same time, the bus side voltage of the DC / DC converter is marked as ;

[0106] Make the total voltage on the bus side of the cascade battery energy storage system minus , get the total voltage on the bus side of other DC / DC converters :

[0107]

[0108] Calculate and obtain the bus side voltage control target of other DC / DC converters :

[0109]

[0110] (3) Traversing the healthy charge state of the battery modules in the cascade battery energy storage system , get the minimum , and the minimum The corresponding DC / DC converter operates according to the minimum duty cycle D of the cascade battery energy storage system. At the same time, the bus side voltage of the DC / DC converter is marked as ;

[0111] Make the total voltage on the bus side of the cascade battery energy storage system minus , get the total voltage on the bus side of other DC / DC converters :

[0112]

[0113] Calculate and obtain the bus side voltage control target of other DC / DC converters :

[0114]

[0115] The SOC balancing control method of the cascade battery energy storage system of the present application can be based on In the charging mode, the bus voltage control target of the DC / DC converter is determined. The DC / DC converter bus voltage corresponding to the smallest battery module operates at the upper voltage limit of the DC / DC converter operation. The DC / DC converter bus voltage corresponding to the largest battery module operates in the minimum duty cycle mode; in the discharge mode, The bus-side voltage of the DC / DC converter corresponding to the largest battery module operates at the upper voltage limit of the DC / DC converter operation; The smallest battery module corresponds to the DC / DC converter bus side voltage operating in the minimum duty cycle mode.

[0116] The SOC balancing control method of the second-life battery energy storage system of the present application is widely used and solves many problems of the energy storage system: (1) It solves the engineering and technical problems of second-life batteries in energy storage applications, eliminates the SOC balancing problem of different SOH of second-life batteries in energy storage system applications, enables battery modules with different attenuation levels to achieve SOC balancing, improves the charge and discharge capacity of the energy storage system, and makes the second-life batteries more friendly to charge and discharge; (2) It solves the problem of mixed use of new and old batteries and different battery attenuation levels after the energy storage system is replaced during operation and maintenance, and suppresses the barrel effect, and realizes the balanced control of SOC between battery modules in the cluster; (3) It solves the differential anisotropic attenuation during battery charging and discharging. Even for uniform energy storage batteries, anisotropic attenuation will still occur during use due to the influence of operating conditions.

[0117] like Figure 6 As shown, it is a schematic diagram of a SOC balancing control system of the cascade battery energy storage system of the present application, which may include:

[0118] Healthy charge module, used to and , calculate the healthy state of charge of each battery module ;

[0119] The average value module is used to calculate the average value of each battery module. average value ;

[0120] The judgment module is used to judge each battery module in turn. and The absolute value of the deviation Is it less than or equal to A? If so, the cascade battery energy storage system operates in PWM mode according to the healthy state of charge balancing algorithm. Otherwise:

[0121] (1) If the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are placed in PWM charging mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0122] (2) If the battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converter is in PWM discharge mode until the absolute value of the deviation of the corresponding battery module is When the value is less than B, the battery module and DC / DC converter in bypass operation will exit the bypass mode and operate in PWM charge / discharge mode;

[0123] Among them, A is the first balance target time control parameter, B is the second balance target time control parameter, A and B are both determined according to the balance target time requirements of the cascade battery energy storage system, and A>B.

[0124] Taking the application scenario of new energy vehicles as an example, the application of retired batteries of new energy vehicles in energy storage will extend the life of the second-life batteries. The reuse of second-life batteries has good economic benefits and makes outstanding contributions to environmental protection. It is crucial to solve the many technical problems faced by second-life batteries in energy storage applications. The attenuation degree of retired batteries is different. It is crucial to solve the problem of SOC balance of batteries with different attenuation degrees in energy storage applications. Otherwise, the barrel effect of second-life batteries will restrict their commercial application.

[0125] Correspondingly, the present application also proposes a second-life battery energy storage system, including a PCS, multiple DC / DC converters and multiple battery modules. The second-life battery energy storage system adopts the above-mentioned second-life battery energy storage system SOC balancing control method.

[0126] It should be noted that in the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the system embodiments described above are merely schematic. For example, the division of each module is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules can be combined or integrated into another device, or some features can be ignored or not executed. The module described as a separate component may or may not be physically separated. The component displayed as a module may be a physical unit or multiple physical units, that is, it may be located in one place, or it may be distributed in multiple different places. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment.

[0127] In addition, each module in each embodiment of the present invention may be integrated into a processing unit, each module may exist physically separately, or two or more modules may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0128] An electronic device provided in an embodiment of the present application includes a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps of the SOC balancing control method of the cascade battery energy storage system described in any of the above embodiments are implemented.

[0129] Another electronic device provided in the embodiment of the present application may also include: an input port connected to the processor, used to transmit multimodal data collected by an external acquisition device to the processor; and a display unit connected to the processor, used to display the processing results of the processor to the outside world; a communication module connected to the processor, used to realize the communication between the electronic device and the outside world. The display unit can be a display panel, a laser scanning display, etc.; the communication mode adopted by the communication module includes but is not limited to mobile high-definition link technology (HML), universal serial bus (USB), high-definition multimedia interface (HDMI), wireless connection (including wireless fidelity technology (WiFi), Bluetooth communication technology, low-power Bluetooth communication technology, and communication technology based on IEEE802.11s).

[0130] An embodiment of the present application provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of the SOC balancing control method of the cascade battery energy storage system described in any of the above embodiments are implemented.

[0131] The computer-readable storage medium involved in the present application includes random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the technical field.

[0132] For the description of the relevant parts of the SOC balancing control system, electronic device and computer-readable storage medium of the cascade battery energy storage system provided in the embodiment of the present application, please refer to the detailed description of the corresponding parts in the SOC balancing control method of the cascade battery energy storage system provided in the embodiment of the present application, which will not be repeated here. In addition, the parts of the above technical solutions provided in the embodiment of the present application that are consistent with the implementation principles of the corresponding technical solutions in the prior art are not described in detail to avoid excessive elaboration.

[0133] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A SOC balancing control method for a second-life battery energy storage system, characterized in that: include: According to the battery module and , calculate the healthy state of charge of each battery module ; Wherein, the calculation obtains the healthy state of charge of each battery module ,include: in, For the The healthy state of charge of each battery module, For the Battery modules , For the Battery modules , For each battery module Maximum value; Calculate the battery modules average value : in, is the total number of battery modules; Determine each battery module in turn and The absolute value of the deviation Is it less than or equal to A? If so, the cascade battery energy storage system operates in PWM mode according to the healthy state of charge balancing algorithm. Otherwise: (1) If the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are put into PWM charging mode until the absolute value of the deviation of the corresponding battery module is If the value is less than B, the battery module and DC / DC converter in bypass mode will exit the bypass mode and operate in PWM charge / discharge mode. (2) If the cascade battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are put into PWM discharge mode until the absolute value of the deviation of the corresponding battery module is If the value is less than B, the battery module and DC / DC converter in bypass mode will exit the bypass mode and operate in PWM charge / discharge mode. Wherein, A is the first balancing standard time control parameter, and B is the second balancing standard time control parameter. Both A and B are determined according to the balancing standard time requirements of the cascade battery energy storage system, and A>B; The healthy state of charge balancing algorithm includes: If the battery energy storage system is in charging mode: Get the maximum The bus side voltage of the DC / DC converter corresponding to the battery module and maximize The DC / DC converter corresponding to the battery module operates according to the minimum duty cycle D of the cascade battery energy storage system; According to the total bus side voltage and bus side voltage of the cascade battery energy storage system , determine the bus side voltage of the remaining DC / DC converters ; According to the bus side voltage and the remaining DC / DC converters corresponding to the battery modules , obtain the bus side voltage control target of each remaining DC / DC converter; The bus-side voltage of each remaining DC / DC converter is operated according to the corresponding bus-side voltage control target of the remaining DC / DC converter; If the cascade battery energy storage system is in discharge mode, then: Get the minimum The bus side voltage of the DC / DC converter corresponding to the battery module and minimize The DC / DC converter corresponding to the battery module operates according to the minimum duty cycle D of the cascade battery energy storage system; According to the total bus side voltage and bus side voltage of the cascade battery energy storage system , determine the bus side voltage of the remaining DC / DC converters ; According to the bus side voltage and the remaining DC / DC converters corresponding to the battery modules , obtain the bus side voltage control target of each remaining DC / DC converter; The bus-side voltage of each remaining DC / DC converter is operated according to the corresponding bus-side voltage control target of the remaining DC / DC converter.

2. The SOC balancing control method for a secondary battery energy storage system according to claim 1, characterized in that: According to the total bus side voltage and bus side voltage of the cascade battery energy storage system , determine the bus side voltage of the remaining DC / DC converters ,include: in, is the total bus-side voltage of the cascade battery energy storage system; According to the bus side voltage and the remaining DC / DC converters corresponding to the battery modules , the bus-side voltage control targets of the remaining DC / DC converters are obtained, including: in, The remaining DC / DC converters The DC / DC converter bus side voltage control target, The remaining DC / DC converters DC / DC converters corresponding to battery modules .

3. The SOC balancing control method for a secondary battery energy storage system according to claim 2, characterized in that: The first equalization target time control parameter A is 5%, and the second equalization target time control parameter B is 2%.

4. A SOC balancing control system for a second-life battery energy storage system, characterized in that: include: Healthy charge module, used to and , calculate the healthy state of charge of each battery module ; Wherein, the calculation obtains the healthy state of charge of each battery module ,include: in, For the The healthy state of charge of each battery module, For the Battery modules , For the Battery modules , For each battery module Maximum value; The average value module is used to calculate the average value of each battery module. average value : in, is the total number of battery modules; The judgment module is used to judge the battery modules in turn. and The absolute value of the deviation Is it less than or equal to A? If so, the cascade battery energy storage system operates in PWM mode according to the healthy state of charge balancing algorithm. Otherwise: (1) If the battery energy storage system is in charging mode, the maximum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are put into PWM charging mode until the absolute value of the deviation of the corresponding battery module is If the value is less than B, the battery module and DC / DC converter in bypass mode will exit the bypass mode and operate in PWM charge / discharge mode. (2) If the cascade battery energy storage system is in discharge mode, the minimum The battery module and the corresponding DC / DC converter are bypassed, and the remaining DC / DC converters are put into PWM discharge mode until the absolute value of the deviation of the corresponding battery module is If the value is less than B, the battery module and DC / DC converter in bypass mode will exit the bypass mode and operate in PWM charge / discharge mode. Wherein, A is the first balancing standard time control parameter, and B is the second balancing standard time control parameter. Both A and B are determined according to the balancing standard time requirements of the cascade battery energy storage system, and A>B; The healthy state of charge balancing algorithm includes: If the battery energy storage system is in charging mode: Get the maximum The bus side voltage of the DC / DC converter corresponding to the battery module and maximize The DC / DC converter corresponding to the battery module operates according to the minimum duty cycle D of the cascade battery energy storage system; According to the total bus side voltage and bus side voltage of the cascade battery energy storage system , determine the bus side voltage of the remaining DC / DC converters ; According to the bus side voltage and the remaining DC / DC converters corresponding to the battery modules , obtain the bus side voltage control target of each remaining DC / DC converter; The bus-side voltage of each remaining DC / DC converter is operated according to the corresponding bus-side voltage control target of the remaining DC / DC converter; If the cascade battery energy storage system is in discharge mode, then: Get the minimum The bus side voltage of the DC / DC converter corresponding to the battery module and minimize The DC / DC converter corresponding to the battery module operates according to the minimum duty cycle D of the cascade battery energy storage system; According to the total bus side voltage and bus side voltage of the cascade battery energy storage system , determine the bus side voltage of the remaining DC / DC converters ; According to the bus side voltage and the remaining DC / DC converters corresponding to the battery modules , obtain the bus side voltage control target of each remaining DC / DC converter; The bus-side voltage of each remaining DC / DC converter is operated according to the corresponding bus-side voltage control target of the remaining DC / DC converter.

5. An electronic device, characterized in that: include: memory for storing computer programs; A processor, configured to implement the steps of the SOC balancing control method for a second-life battery energy storage system as claimed in any one of claims 1 to 3 when executing the computer program.

6. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the SOC balancing control method for a cascade battery energy storage system according to any one of claims 1 to 3 are implemented.

7. A second-life battery energy storage system, comprising a PCS, multiple DC / DC converters, and multiple battery modules; characterized in that: The second-life battery energy storage system adopts the second-life battery energy storage system SOC balancing control method described in any one of claims 1 to 3.

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