Energy storage system and battery management method

Abstract

The application provides a kind of energy storage system and battery management method, energy storage system includes battery cluster, battery control system, at least two first power conversion modules, bus and second power conversion module, the multiple battery packs in battery cluster are connected in parallel to bus by at least two first power conversion modules, one end of second power conversion module is connected in parallel with battery cluster, the other end of second power conversion module is connected load or power grid.Battery control system obtains target current value that second power conversion module needs to provide to load or power grid.Based on target current value and the battery parameters of each battery pack, battery control system controls battery pack to discharge to bus through the first power conversion module connected in parallel with battery pack, or controls the first power conversion module connected in parallel with battery pack to charge battery pack, to balance the battery parameters of each battery pack or make battery cluster output target power.In the application, the battery parameters of each battery pack can be balanced or the battery cluster can output target power, which improves system stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery energy storage, and in particular to an energy storage system and a battery management method. BACKGROUND

[0002] An energy storage system usually has multiple battery clusters, and a battery cluster can be obtained by connecting multiple battery packs in series. The energy storage system can supply power to a load by connecting multiple battery clusters in parallel. Different device attenuation rates in the energy storage system or the use of new and old batteries together can cause a large difference in the state of charge (SOC) (also referred to as the remaining power) between the battery packs in the energy storage system, which in turn affects the performance of the energy storage system. Therefore, when new and old batteries are used together, after the charging / discharging of some battery packs is completed, the battery packs that have not completed charging / discharging can continue to charge / discharge. At this time, a current balancing circuit (a DC / DC converter is usually used in the current balancing circuit) needs to be added to make the energy storage system work in a balancing current mode with the goal of balancing the state of charge of the battery packs. Generally, the battery management system in the energy storage system can use the SOC change rate of each battery cluster as a basis to determine whether the energy storage system needs to be adjusted for current balancing. When the energy storage system needs to be adjusted for current balancing (i.e., the SOC of each battery pack is significantly different), the DC / DC converters connected in parallel to each battery pack work in a balancing current mode to balance the SOC of each battery pack. However, when the specifications of the battery packs are different, the SOC change rate cannot accurately switch the working mode of the DC / DC converter, which results in the inability to balance the SOC of each battery pack and weak applicability. SUMMARY

[0003] The present application provides an energy storage system and a battery management method, which can balance the battery parameters of each battery pack or make the battery cluster output a target power, thereby improving the stability of the system and having strong applicability.

[0004] In a first aspect, the present application provides an energy storage system, which can include a battery cluster, a battery control system, at least two first power conversion modules, a bus and a second power conversion module. The battery cluster can include a plurality of battery packs connected in series, the plurality of battery packs can be connected in parallel to the bus through the at least two first power conversion modules, and one end of the second power conversion module is connected in parallel to the battery cluster, and the other end of the second power conversion module can be connected to a load or a power grid. The first power conversion module can be a DC / DC conversion module, and the bus can be a DC bus. Alternatively, the first power conversion module can be a DC / AC conversion module, and the bus can be an AC bus. The battery control system can be configured to obtain a target current value required by the second power conversion module to provide to the load or the power grid. The battery control system can also be configured to control the battery packs to discharge to the bus through the first power conversion modules connected in parallel to the battery packs, or control the first power conversion modules connected in parallel to the battery packs to charge the battery packs, based on the target current value and battery parameters of the battery packs, so as to balance the battery parameters of the battery packs or make the battery cluster output a target power. In the present application, when the specifications of the battery packs in the battery cluster are different, the battery parameters of the battery packs can be balanced or the battery cluster can output the target power, thereby improving the stability of the system and the applicability.

[0005] In combination with the first aspect, in a first possible implementation, the battery control system can be configured to receive a current instruction value of the second power conversion module issued by a system controller, detect battery parameters of the battery packs, and determine a system control parameter according to the battery parameters of the battery packs and / or the current instruction value of the second power conversion module. The battery control system can also be configured to control the first power conversion modules to switch their working modes to a target mode when the system control parameter reaches a parameter threshold, and obtain a target current value required by the second power conversion module to provide to the load or the power grid in the target mode. The target mode can include a target power balancing mode or an equalization balancing mode. In the energy storage system provided by the present application, the working modes of the first power conversion modules can be diversified, and the accuracy of the working mode switching can be improved, thereby improving the applicability.

[0006] With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner, when the battery parameter comprises the state of charge value, the battery control system can be configured to determine the state of charge deviation value according to the maximum state of charge value and the minimum state of charge value in the state of charge values of the battery packs, and determine the state of charge deviation value and / or the current instruction value of the second power conversion module as the system control parameter. In other words, the system control parameter can be the state of charge deviation value, the current instruction value of the second power conversion module, the state of charge deviation value and the current instruction value of the second power conversion module, or other parameters, which can be determined according to actual application scenarios and is not limited herein. In the energy storage system provided in the present application, the state of charge deviation value and / or the current instruction value of the second power conversion module can be determined as the system control parameter, so that whether the working mode of each first power conversion module is switched to the target mode can be accurately determined through the system control parameter, and the applicability is stronger.

[0007] With reference to the second possible implementation manner of the first aspect, in a third possible implementation manner, when the system control parameter is the state of charge deviation value, the battery control system can be configured to determine that the system control parameter reaches the parameter threshold value when the state of charge deviation value is greater than a preset state of charge threshold value, and control each first power conversion module to switch the working mode thereof to the equalization current sharing mode. In the energy storage system provided in the present application, each first power conversion module can be controlled to switch the working mode thereof to the equalization current sharing mode when the state of charge deviation value is greater than the preset state of charge threshold value, so that the accuracy of mode switching is improved, and the applicability is stronger.

[0008] With reference to the second possible implementation manner of the first aspect, in a fourth possible implementation manner, when the system control parameter comprises the state of charge deviation value and the current instruction value of the second power conversion module, the battery control system can be configured to determine that the system control parameter reaches the parameter threshold value when the state of charge deviation value is less than or equal to the preset state of charge threshold value and the current instruction value of the second power conversion module is greater than the current limit value of the second power conversion module, and control each first power conversion module to switch the working mode thereof to the target power current sharing mode. In the energy storage system provided in the present application, each first power conversion module can be controlled to switch the working mode thereof to the target power current sharing mode when the state of charge deviation value is less than or equal to the preset state of charge threshold value and the current instruction value is greater than the current limit value, so that the accuracy of mode switching is improved, and the applicability is stronger.

[0009] With reference to the second possible implementation manner of the first aspect, in a fifth possible implementation manner, when the system control parameter is the current command value of the second power conversion module, the battery control system is configured to determine that the system control parameter reaches the parameter threshold when the current command value of the second power conversion module is greater than the current limit value of the second power conversion module, and control each first power conversion module to switch the working mode to the target power current sharing mode. In the energy storage system provided in the present application, each first power conversion module can be controlled to switch the working mode to the target power current sharing mode when the current command value is greater than the current limit value, thereby improving the accuracy of mode switching and having stronger applicability.

[0010] With reference to the second possible implementation manner of the first aspect, in a sixth possible implementation manner, when the system control parameter includes the state of charge deviation value and the current command value of the second power conversion module, the battery control system is configured to determine that the system control parameter reaches the parameter threshold when the current command value of the second power conversion module is less than or equal to the current limit value of the second power conversion module and the state of charge deviation value is greater than the preset state of charge threshold, and control each first power conversion module to switch the working mode to the equalization current sharing mode. In the energy storage system provided in the present application, each first power conversion module can be controlled to switch the working mode to the equalization current sharing mode when the current command value is less than or equal to the current limit value and the state of charge deviation value is greater than the preset state of charge threshold, thereby improving the accuracy of mode switching and having stronger applicability.

[0011] With reference to any one of the fourth possible implementation manner of the first aspect to the sixth possible implementation manner of the first aspect, in a seventh possible implementation manner, the battery control system is further configured to determine the current limit value of the second power conversion module based on the battery parameters of each battery pack. The battery parameters can include temperature, maximum working current, state of charge value, state of health (SOH) and other parameters. In other words, the battery control system is further configured to determine the current limit value of the second power conversion module based on the temperature, maximum working current, state of charge value, state of health and other parameters of each battery pack. In the energy storage system provided in the present application, the current limit value of the second power conversion module can be determined based on the battery parameters of each battery pack, and it is further possible to determine whether to switch each first power conversion module to the target mode, thereby having stronger applicability.

[0012] In an eighth possible implementation of any one of the first through seventh possible implementations of the first aspect, one battery pack can be connected in parallel to the bus through one first power conversion module, in other words, one battery pack is connected in parallel to one end of the first power conversion module, and the other end of the first power conversion module is connected in parallel to the bus. When the target mode is the target power current sharing mode, the battery parameters can include a maximum operating current, and the battery control system can be configured to receive a power current value issued by the system controller based on the expected power, and issue the power current value to the first power conversion module connected in parallel to each battery pack, the power current value being a current value required by the second power conversion module to provide power to the load or the power grid in the target power current sharing mode. The size of the expected power can be determined by the demand of the load. Any first power conversion module connected in parallel to any battery pack can be configured to absorb a portion of the current other than the power current in the maximum operating current of any battery pack and output to the bus, or to absorb current from the bus based on the power current value and output in parallel to the second power conversion module with any battery pack, so that the battery cluster outputs the target power to the second power conversion module. The current value of the power current is equal to the power current value. The current output in parallel by any battery pack and any first power conversion module connected in parallel thereto is less than or equal to the power current. When the current output in parallel is less than the power current, the target power is less than the expected power. When the current output in parallel is equal to the power current, the target power is equal to the expected power. In the energy storage system provided in the present application, the power demand of the load can be taken as the primary target, and all battery packs can be controlled to exchange power with the maximum capacity, so as to maximize the actual output power of the battery cluster, thereby improving the stability of the system and the applicability.

[0013] In a ninth possible implementation of any one of the first through seventh possible implementations of the first aspect, one battery pack is connected in parallel to the bus through one first power conversion module, the target mode is the balancing current sharing mode, and the battery parameters include a state of charge value. The battery control system can be configured to control the battery pack to discharge to the bus through the first power conversion module connected in parallel to the battery pack when the state of charge value of the battery pack is greater than an average state of charge value, or to control the first power conversion module connected in parallel to the battery pack to charge the battery pack when the state of charge value of the battery pack is less than the average state of charge value. The average state of charge value is an average value of the state of charge values of the battery packs. In the energy storage system provided in the present application, the state of charge value and the average state of charge value of the battery pack can be used to accurately determine the charging or discharging of the battery pack, thereby improving the applicability.

[0014] In combination with the ninth possible implementation manner of the first aspect, in a tenth possible implementation manner, the battery parameters further include a maximum operating current, and the battery control system is configured to receive the equalization current value from the system controller and send the equalization current value to the first power conversion module connected in parallel to each battery pack, the equalization current value being a current value required by the second power conversion module in the equalization current sharing mode to provide to the load or the power grid. Any first power conversion module connected in parallel to any battery pack in each battery pack is configured to absorb a portion of the current of the maximum operating current of the any battery pack other than the equalization current and output to the bus, or to absorb the current from the bus to output the equalization current to the second power conversion module and charge the any battery pack to equalize the battery parameters of each battery pack. The equalization current has a current value equal to the equalization current value, and the battery parameters of each battery pack can include a state of charge value, a state of health value, or other parameters. In the energy storage system provided in the present application, any battery pack can be charged or discharged to equalize the battery parameters of each battery pack, which has higher applicability.

[0015] In combination with any one of the first aspect to the tenth possible implementation manner of the first aspect, in an eleventh possible implementation manner, the plurality of battery packs are connected to the same first power conversion module through a selection switch, and the selection switch is configured to select a target battery pack from the plurality of battery packs to connect the target battery pack to the bus through the same first power conversion module in parallel. The target battery pack is the battery pack with the maximum battery parameter or the battery pack with the minimum battery parameter in the plurality of battery packs, and the battery parameter includes a state of charge value or a maximum operating current. In the energy storage system provided in the present application, a small number of first power conversion modules can be used to equalize the battery parameters of the battery packs or to make the battery cluster output the target power, thereby saving costs.

[0016] In the second aspect, the present application provides a battery management method, which is applicable to an energy storage system. The energy storage system includes a battery cluster, a battery control system, at least two first power conversion modules, a bus, and a second power conversion module. The battery cluster includes a plurality of battery packs connected in series. The plurality of battery packs are connected to the bus in parallel through the at least two first power conversion modules. One end of the second power conversion module is connected to the battery cluster in parallel, and the other end of the second power conversion module is connected to a load or a power grid. In the method, the battery control system can obtain a target current value required by the second power conversion module to provide to the load or the power grid. The battery control system can control the battery packs to discharge to the bus through the first power conversion module connected in parallel to the battery packs or control the first power conversion module connected in parallel to the battery packs to charge the battery packs based on the target current value and the battery parameters of the battery packs to equalize the battery parameters of the battery packs or make the battery cluster output the target power. In the present application, when the specifications of the battery packs in the battery cluster are different, the battery parameters of the battery packs can be equalized or the battery cluster can output the target power, which has higher applicability.

[0017] In combination with the second aspect, in a first possible implementation, the battery control system can receive the current instruction value of the second power conversion module issued by the system controller, detect the battery parameters of each battery pack, and determine the system control parameter according to the battery parameters of each battery pack and / or the current instruction value of the second power conversion module. When the system control parameter reaches the parameter threshold value, the battery control system can control each first power conversion module to switch its working mode to the target mode, and obtain the target current value required by the second power conversion module to provide to the load or the power grid in the target mode. In the method provided in the present application, the diversity of the working mode of the first power conversion module can be realized, and the accuracy of the working mode switching is improved, and the applicability is stronger.

[0018] In combination with the first possible implementation of the second aspect, in a second possible implementation, the battery parameter includes a state of charge value. The battery control system determines a state of charge deviation value according to the maximum state of charge value and the minimum state of charge value in the state of charge values of each battery pack, and determines the state of charge deviation value and / or the current instruction value of the second power conversion module as the system control parameter. In the method provided in the present application, the state of charge deviation value and / or the current instruction value of the second power conversion module can be determined as the system control parameter, and then whether the working mode of each first power conversion module is switched to the target mode can be accurately judged through the system control parameter, and the applicability is stronger.

[0019] In combination with the second possible implementation of the second aspect, in a third possible implementation, the system control parameter is the state of charge deviation value. When the state of charge deviation value is greater than a preset state of charge threshold value, the battery control system determines that the system control parameter reaches the parameter threshold value, and controls each first power conversion module to switch its working mode to the equalization current sharing mode. In the method provided in the present application, each first power conversion module can be controlled to switch its working mode to the equalization current sharing mode when the state of charge deviation value is greater than the preset state of charge threshold value, so that the accuracy of the mode switching is improved, and the applicability is stronger.

[0020] In combination with the second possible implementation of the second aspect, in a fourth possible implementation, the system control parameter is the current instruction value of the second power conversion module. When the current instruction value of the second power conversion module is greater than the current limiting value of the second power conversion module, the battery control system determines that the system control parameter reaches the parameter threshold value, and controls each first power conversion module to switch its working mode to the target power current sharing mode. In the method provided in the present application, each first power conversion module can be controlled to switch its working mode to the target power current sharing mode when the state of charge deviation value is less than or equal to the preset state of charge threshold value and the current instruction value is greater than the current limiting value, so that the accuracy of the mode switching is improved, and the applicability is stronger.

[0021] In combination with the second possible implementation manner of the second aspect, in a fifth possible implementation manner, the system control parameter includes a state of charge deviation value and a current instruction value of the second power conversion module. When the state of charge deviation value is less than or equal to a preset state of charge threshold value and the current instruction value of the second power conversion module is greater than a current limiting value of the second power conversion module, the battery control system determines that the system control parameter reaches the parameter threshold value, and controls each first power conversion module to switch the working mode to the target power current sharing mode. Conversely, when the current instruction value of the second power conversion module is less than or equal to the current limiting value of the second power conversion module and the state of charge deviation value is greater than the preset state of charge threshold value, the battery control system determines that the system control parameter reaches the parameter threshold value, and controls each first power conversion module to switch the working mode to the balancing current sharing mode. In the method provided in the application, the state of charge deviation value and the current instruction value can be used to determine whether to switch the working mode of each first power conversion module to the balancing current sharing mode or the target power current sharing mode, thereby improving the accuracy of mode switching and having stronger applicability.

[0022] In combination with any one of the first possible implementation manner to the fifth possible implementation manner of the second aspect, in a sixth possible implementation manner, one battery pack is connected in parallel to the bus through one first power conversion module, the target mode is the target power current sharing mode, the target current value is a power current value required by the second power conversion module to provide to the load or the power grid in the target power current sharing mode, the power current value is determined by the expected power, and the battery parameter includes a maximum working current. The battery control system can control any first power conversion module connected in parallel to any battery pack to absorb a part of the current of the maximum working current of any battery pack except the power current and output to the bus, or control any first power conversion module to absorb current from the bus based on the power current value and output in parallel to the second power conversion module with any battery pack, so that the battery cluster outputs the target power to the second power conversion module. Wherein, the current value of the power current is equal to the power current value, and the target power is less than or equal to the expected power. In the method provided in the application, the power demand of the load can be taken as the primary target, and all battery packs are controlled to exchange power with the maximum capacity, so that the actual output power of the battery cluster is maximized, thereby improving the system stability and having stronger applicability.

[0023] In any one of the first possible implementation to the fifth possible implementation of the second aspect, in a seventh possible implementation, one battery pack is connected in parallel to the bus through one first power conversion module, the target mode is a balanced current sharing mode, the target current value is a balanced current value required by the second power conversion module to provide to the load or the grid in the balanced current sharing mode, and the battery parameter includes a maximum working current. The battery control system can control any first power conversion module connected in parallel to any battery pack to absorb a part of the current of the any battery pack except the balanced current and output to the bus, or control any first power conversion module to absorb current from the bus to output the balanced current to the second power conversion module and charge any battery pack to balance the battery parameters of the battery packs. The current value of the balanced current is equal to the balanced current value. In the method provided in the present application, the battery parameters of the battery packs can be balanced by charging or discharging any battery pack, and the applicability is stronger.

[0024] Optionally, when the target mode is the balanced current sharing mode, the battery parameter further includes a state of charge value, which can be used to determine to charge the battery pack or control the battery pack to discharge. When the state of charge value of the battery pack is greater than the average state of charge value, the battery control system can control the battery pack to discharge to the bus through the first power conversion module connected in parallel to the battery pack, or control the first power conversion module connected in parallel to the battery pack to charge the battery pack when the state of charge value of the battery pack is less than the average state of charge value.

[0025] In the present application, the working mode of the first power conversion module can be switched to the target mode by the system control parameter to balance the battery parameters of the battery packs or make the battery cluster output the target power, the diversity of the working mode of the first power conversion module can be realized, the accuracy of the working mode switching and the system stability are improved, and the applicability is stronger. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is an application scenario diagram of the energy storage system provided in the present application;

[0027] Figure 2 is a structural diagram of the energy storage system provided in the present application;

[0028] Figure 3 is another structural diagram of the energy storage system provided in the present application;

[0029] Figure 4 is still another structural diagram of the energy storage system provided in the present application;

[0030] Figure 5 is a flowchart of the battery management method provided in the present application. DETAILED DESCRIPTION

[0031] The energy storage system provided in the present application is applicable to various types of power generation equipment such as photovoltaic power generation equipment or wind power generation equipment, and various types of power consumption equipment (such as power grid, household equipment or industrial and commercial power consumption equipment), and can be applied to the field of automobile, micro-grid or other fields. The energy storage system provided in the present application is applicable to energy storage of different types of batteries, which can include lithium ion battery, lead-acid battery (or lead-acid storage battery), or other batteries, and the specific type of battery is not limited in the present application.

[0032] The energy storage system provided in the present application can be adapted to different application scenarios, such as photovoltaic power generation scenario, wind power generation scenario, or power consumption equipment power supply scenario. The following will take the power consumption equipment power supply scenario as an example for description, and the following will not be repeated. Please see Figure 1 , Figure 1 is a schematic diagram of the application scenario of the energy storage system provided in the present application. The energy storage system provided in the present application can include a battery cluster, a battery control system, at least two first power conversion modules, a bus and a second power conversion module (such as a DC / DC converter). The battery cluster can include a plurality of battery packs connected in series, and the plurality of battery packs can be connected in parallel to the bus through the at least two first power conversion modules. One end of the second power conversion module is connected in parallel to the battery cluster, and the other end of the second power conversion module can be connected to the load or the power grid through an energy storage converter (such as a DC / AC converter). One battery pack can be composed of one or more battery cells (the voltage of the battery cell is usually between 2.5V and 4.2V) connected in series and parallel, forming the smallest energy storage and management unit. As shown in Figure 1 , the energy storage system (such as energy storage system 1) can include an energy storage container and a DC / AC converter. The energy storage container can include at least one battery cluster (i.e. one or more battery clusters) and a DC / DC converter. In the case that the energy storage container includes a plurality of battery clusters, the battery clusters are connected in parallel and connected in parallel to the DC / DC converter. In the case that the energy storage container includes one battery cluster, the battery cluster is connected in parallel to the DC / DC converter. The battery cluster in the energy storage container can provide a direct current input voltage to the DC / DC converter. The DC / DC converter performs power conversion on the direct current input voltage and outputs direct current power to the DC / AC converter. At this time, the DC / AC converter can perform power conversion on the direct current power input by the DC / DC converter, and output alternating current power to the alternating current power grid (such as power grid 2) or the alternating current load (such as household equipment 3), so as to supply power to the power grid 2 and the household equipment 3.

[0033] In some possible embodiments, the battery control system of the energy storage system can obtain a target current value required by the second power conversion module to provide to the load or the power grid. The battery control system can control the battery packs to discharge to the bus through the first power conversion module in parallel with the battery pack or control the first power conversion module in parallel with the battery pack to charge the battery pack based on the target current value and the battery parameters of the battery packs, so as to balance the battery parameters of the battery packs or make the battery cluster output a target power. The energy storage system provided in the present application can balance the battery parameters of the battery packs or make the battery cluster output a target power, thereby improving the stability of the system and being more applicable. The energy storage system provided in the present application and the working principle thereof will be described below in conjunction with Figures 2 to 4 The energy storage system provided in the present application and the working principle thereof will be described below in conjunction with

[0034] Referring to Figure 2 , Figure 2 is a structural schematic diagram of the energy storage system provided in the present application. As shown in Figure 2 , the energy storage system 1 can include a battery cluster 10, at least two first power conversion modules (for example, a first power conversion module 20a to a first power conversion module 20n), a bus 30, a second power conversion module 40, and a battery control system 50. The plurality of battery packs in the battery cluster 10 can be connected in parallel to the bus 30 through the at least two first power conversion modules, for example, one battery pack in the battery cluster 10 is connected in parallel to the bus 30 through one first power conversion module, or a plurality of battery packs in the battery cluster 10 are connected in parallel to the bus 30 through one first power conversion module. For the convenience of description, the first power conversion module 20a to the first power conversion module 20n will be taken as an example for description below, and the following will not be described in detail. The battery cluster 10 can include a plurality of battery packs (for example, a battery pack 10a to a battery pack 10n), the battery pack 10a is connected in parallel to the bus 30 through the first power conversion module 20a, the battery pack 10b is connected in parallel to the bus 30 through the first power conversion module 20b, …, and the battery pack 10n is connected in parallel to the bus 30 through the first power conversion module 20n. In other words, one end of each battery pack is connected in parallel to one first power conversion module, and the other end of each first power conversion module is connected in parallel to the bus 30. For example, the battery pack 10a is connected in parallel to one end of the first power conversion module 20a, the battery pack 10b is connected in parallel to one end of the first power conversion module 20b, …, and the battery pack 10n is connected in parallel to one end of the first power conversion module 20n, and the other end of the first power conversion module 20a to the first power conversion module 20n is connected in parallel to the bus 30. The one or more power conversion modules connected in parallel with the battery pack can be collectively referred to as the first power conversion module in the present application. The above-mentioned battery control system 50 can communicate with the battery cluster 10, the first power conversion module 20a to the first power conversion module 20n, and the second power conversion module 40 through power line carrier (PLC) communication.

[0035] In some possible embodiments, when the energy storage system includes a plurality of battery clusters, one battery cluster can be connected in parallel with one second power conversion module, or a plurality of battery clusters can be connected in parallel with the same second power conversion module, and thus the second power conversion module can also be referred to as a cluster-level power conversion module or a cluster-level power converter, which can be determined according to the actual application scenario and is not limited herein. The power conversion module connected in parallel with the entire battery cluster can be referred to as a second power conversion module in the present application, and the second power conversion module can be a cluster-level DC / DC conversion module (also referred to as a cluster-level DC / DC converter). For convenience of description, the energy storage system including one battery cluster will be described below, as shown in FIG. 1, the energy storage system 1 includes one battery cluster (i.e., the battery cluster 10) and one second power conversion module (i.e., the second power conversion module 40), one end of the second power conversion module 40 is connected in parallel with the battery cluster 10, and the other end of the second power conversion module 40 can be connected with a load or a power grid. Figure 2

[0036] In some possible embodiments, the battery control system 50 can obtain a target current value required by the second power conversion module 40 to provide to the load or the power grid. Further, the battery control system 50 can control the battery packs 10a to 10n to discharge or charge through the first power conversion modules connected in parallel with the battery packs to the bus 30 based on the target current value and the maximum operating current of each battery pack, so as to balance the battery parameters of the battery packs 10a to 10n or make the battery cluster 10 output a target power. The current value required by the second power conversion module 40 to provide to the load or the power grid in the target mode (such as a target power balancing current mode or an equalization current mode) can be collectively referred to as a target current value (such as a power current value or an equalization current value) in the present application.

[0037] ​In some possible embodiments, the system controller can issue an instruction carrying the current instruction value of the second power conversion module 40 to the battery control system 50. At this time, the battery control system 50 can receive the current instruction value of the second power conversion module 40 issued by the system controller, detect the battery parameters of each battery pack in the battery packs 10a to 10n, and determine the system control parameter according to the battery parameters of each battery pack in the battery packs 10a to 10n and / or the current instruction value of the second power conversion module 40. The parameters used to determine whether to switch the working mode of each first power conversion module can be collectively referred to as the system control parameter in this application. When the system control parameter reaches a parameter threshold value, the battery control system 50 can control each first power conversion module in the first power conversion modules 20a to 20n to switch its working mode to a target mode, and obtain a target current value required by the second power conversion module 40 to provide to the load or the power grid in the target mode. The parameter threshold value can be a preset threshold value configured for the energy storage system, and / or a threshold value calculated by the battery parameters of each battery pack, which can be determined according to the actual application scenario and is not limited herein.

[0038] In some possible embodiments, when the battery parameters include the state of charge value, the battery control system 50 can determine the state of charge value of each battery pack in the battery packs 10a to 10n according to the current integral of each battery pack or the volt-ampere characteristic curve (i.e., the UI characteristic curve) of each battery pack. The battery control system 50 can determine a state of charge deviation value according to the maximum state of charge value and the minimum state of charge value in the state of charge values of each battery pack in the battery packs 10a to 10n, and determine the state of charge deviation value and / or the current instruction value of the second power conversion module 40 as the system control parameter. The state of charge deviation value herein can be the difference between the maximum state of charge value and the minimum state of charge value. It can be understood that the system control parameter can be the state of charge deviation value; or the system control parameter can be the current instruction value of the second power conversion module 40; or the system control parameter can be the state of charge deviation value and the current instruction value of the second power conversion module 40, which can be determined according to the actual application scenario and is not limited herein.

[0039] In some possible embodiments, the system control parameter can be the state of charge deviation value when the energy storage system 1 is primarily aimed at protecting the battery packs in the battery cluster 10. When the state of charge deviation value is greater than a preset state of charge threshold, the battery control system 50 can determine that the system control parameter reaches a parameter threshold, and control each of the first power conversion modules 20a to 20n to switch its operation mode to the equalization current sharing mode. Alternatively, when the state of charge deviation value is less than or equal to the preset state of charge threshold, the system control parameter can include the state of charge deviation value and a current command value of the second power conversion module 40. The battery control system 50 can determine a current limit value of the second power conversion module 40 based on battery parameters of each of the battery packs 10a to 10n, which can include temperature, maximum operating current, state of charge value, state of health value, and other parameters. In other words, the battery control system 50 can determine the current limit value of the second power conversion module 40 based on the temperature, maximum operating current, state of charge value, and state of health value of each of the battery packs 10a to 10n. The maximum operating current of the battery pack can be determined by the maximum charge / discharge operating current configured by the battery pack factory and the temperature of the battery pack, e.g., the maximum operating current of the battery pack decreases as the temperature increases. In other words, when the factory configuration of the battery pack is determined, and the temperature of the battery pack is determined, the maximum operating current of the battery pack (including the maximum charge operating current and / or the maximum discharge operating current) is determined. When the state of charge deviation value is less than or equal to the preset state of charge threshold, and the current command value of the second power conversion module 40 is greater than the current limit value of the second power conversion module 40, the battery control system 50 can determine that the system control parameter reaches the parameter threshold, and control each of the first power conversion modules 20a to 20n to switch its operation mode to the target power current sharing mode.

[0040] In some possible embodiments, the system control parameter can be the current command value of the second power conversion module 40 in the case that the energy storage system 1 is primarily aimed at meeting the power demand of the load or the grid. When the current command value of the second power conversion module 40 is greater than the current limit value of the second power conversion module 40, the battery control system 50 can determine that the system control parameter reaches the parameter threshold value, and control each of the first power conversion modules 20a to 20n to switch its operation mode to the target power equalization mode. Since the battery cluster 10 will exchange power with the maximum capacity in the target power equalization mode, i.e. the battery cluster 10 will output the maximum power that it can provide to the load or the grid, and the target power output by the battery cluster 10 will be less than or equal to the maximum power demanded by the load or the grid, the target power equalization mode can also be referred to as the maximum power equalization mode. Alternatively, the system control parameter can include the state of charge deviation value and the current command value of the second power conversion module 40 in the case that the current command value of the second power conversion module 40 is less than or equal to the current limit value of the second power conversion module 40. When the current command value of the second power conversion module 40 is less than or equal to the current limit value of the second power conversion module 40, and the state of charge deviation value is greater than the preset state of charge threshold value, the battery control system 50 can determine that the system control parameter reaches the parameter threshold value, and control each of the first power conversion modules 20a to 20n to switch its operation mode to the equalization equalization mode.

[0041] In some possible embodiments, when the target mode is the target power current sharing mode, the system controller can determine an expected power of the load or the power grid, and issue a power current value to the battery control system 50 based on the expected power. The expected power can be determined by the power requirement of the load, and the expected power can also be understood as the maximum power required by the load or the power grid. The power current value is the current value required by the second power conversion module 40 to provide to the load or the power grid in the target power current sharing mode. At this time, the battery control system 50 can receive the power current value from the system controller, and issue the power current value to the first power conversion module connected in parallel to each battery pack in the battery cluster 10. For convenience of description, the following will be described by taking the battery cluster 10 including the battery pack 10a and the battery pack 10b as an example, and the battery parameters can include the maximum working current. When the maximum working current of the battery pack 10a is greater than the maximum working current of the battery pack 10b, the battery pack 10a can output a power current to the second power conversion module 40, and output a part of the current in the maximum working current of the battery pack 10a other than the power current to the first power conversion module 20a. The first power conversion module 20a can absorb the part of the current in the maximum working current of the battery pack 10a other than the power current and output to the bus 30. At this time, the first power conversion module 20b can absorb current from the bus 30 based on the power current value and output in parallel to the second power conversion module 40 with the battery pack 10b, so that the battery cluster 10 outputs the target power to the second power conversion module 40. The current value of the power current is equal to the power current value. The current output in parallel by the battery pack 10b and the first power conversion module 20b can be less than or equal to the power current, and when the current output in parallel by the battery pack 10b and the first power conversion module 20b is less than the power current, the target power is less than the expected power; when the current output in parallel by the battery pack 10b and the first power conversion module 20b is equal to the power current, the target power is equal to the expected power, which can be determined according to the actual application scenario, and is not limited herein. When the target power is equal to the expected power, it can be indicated that the battery cluster 10 outputs the maximum power to the second power conversion module 40.

[0042] In some possible embodiments, when the target mode is the equalization current mode, the battery parameters can include the state of charge values, and the battery control system 50 can control the battery packs to discharge through the first power conversion modules in parallel connection to the bus 30 when the state of charge values of the battery packs are greater than the average state of charge value, or control the battery packs to charge through the first power conversion modules in parallel connection when the state of charge values of the battery packs are less than the average state of charge value. The average state of charge value can be the average of the state of charge values of the battery packs in the battery cluster 10. The system controller can issue an equalization current value to the battery control system 50, and the equalization current value is the current value required by the second power conversion module 40 to provide power to the load or the grid in the equalization current mode. At this time, the battery control system 50 can receive the equalization current value from the system controller and issue the equalization current value to the first power conversion modules in parallel connection of the battery packs in the battery cluster 10. For the convenience of description, the following will take the battery cluster 10 including the battery pack 10a and the battery pack 10b as an example for description, and the battery parameters also include the maximum working current (i.e., the battery parameters include the state of charge values and the maximum working current). When the maximum working current of the battery pack 10a is greater than the maximum working current of the battery pack 10b, the battery pack 10a can output the equalization current to the second power conversion module 40 and output the part of the maximum working current of the battery pack 10a other than the equalization current to the first power conversion module 20a. The first power conversion module 20a can absorb the part of the maximum working current of the battery pack 10a other than the equalization current and output to the bus 30. At this time, the first power conversion module 20b can absorb current from the bus 30 to output the equalization current to the second power conversion module 40 and charge the battery pack 10b to equalize the battery parameters of the battery pack 10a and the battery pack 10b in the battery cluster 10. The equalization current value is equal to the equalization current value, and the battery parameters of each battery pack can include the state of charge value, the state of health value or other parameters.

[0043] Optionally, in some possible embodiments, the plurality of battery packs can also be connected to the same first power conversion module through the selection switch, and the selection switch can select a target battery pack from the plurality of battery packs to connect the target battery pack to the bus through the same first power conversion module in parallel connection. The target battery pack can be the battery pack with the maximum battery parameter or the battery pack with the minimum battery parameter from the plurality of battery packs, and the battery parameter can include the state of charge value or the maximum working current. Since the selection switch can cut off the battery packs other than the target battery pack from the plurality of battery packs when selecting the target battery pack, the battery control system can partially equalize the battery parameters of the battery packs in the battery cluster or make the battery cluster output the target power to the second power conversion module, so that the purpose of partially equalizing the battery parameters of the battery packs or making the battery cluster output the target power can be achieved through a small number of first power conversion modules, thereby saving costs.

[0044] For convenience of description, the following will be described by taking the battery cluster 10 including the battery pack 10a, the battery pack 10b and the battery pack 10n as an example, the battery pack 10a and the battery pack 10b are connected to the first power conversion module 20a through the selection switch, and the battery pack 10n is directly connected to the first power conversion module 20n. In the case where the target mode is the equalization current-sharing mode, the battery parameters include the state-of-charge values, it is assumed that the state-of-charge value of the battery pack 10n is greater than the state-of-charge value of the battery pack 10a and greater than the state-of-charge value of the battery pack 10b, when the state-of-charge value of the battery pack 10a is greater than the state-of-charge value of the battery pack 10b, the selection switch can be selected to connect the battery pack 10b and cut off the battery pack 10a, at this time, the battery control system 50 can equalize the battery parameters of the battery pack 10b and the battery pack 10n in the battery cluster 10. It is assumed that the state-of-charge value of the battery pack 10n is less than the state-of-charge value of the battery pack 10a and less than the state-of-charge value of the battery pack 10b, when the state-of-charge value of the battery pack 10a is greater than the state-of-charge value of the battery pack 10b, the selection switch can be selected to connect the battery pack 10a and cut off the battery pack 10b, at this time, the battery control system 50 can equalize the battery parameters of the battery pack 10a and the battery pack 10n in the battery cluster 10. In the case where the target mode is the target power current-sharing mode, the battery parameters include the maximum working currents, it is assumed that the maximum working current of the battery pack 10n is greater than the maximum working current of the battery pack 10a and greater than the maximum working current of the battery pack 10b, when the maximum working current of the battery pack 10a is greater than the maximum working current of the battery pack 10b, the selection switch can be selected to connect the battery pack 10b and cut off the battery pack 10a, at this time, the battery control system 50 can make the battery pack 10b and the battery pack 10n in the battery cluster 10 output the target power to the second power conversion module 40. It is assumed that the maximum working current of the battery pack 10n is less than the maximum working current of the battery pack 10a and less than the maximum working current of the battery pack 10b, when the maximum working current of the battery pack 10a is greater than the maximum working current of the battery pack 10b, the selection switch can be selected to connect the battery pack 10a and cut off the battery pack 10b, at this time, the battery control system 50 can make the battery pack 10a and the battery pack 10n in the battery cluster 10 output the target power to the second power conversion module 40.

[0045] Please see Figure 3 , Figure 3 is another structural schematic diagram of the energy storage system provided by the present application. As Figure 3As shown in 3a, the energy storage system 1 also includes an energy storage converter 60. One end of the energy storage converter 60 can be connected in parallel with the second power conversion module 40, and the other end of the energy storage converter 60 can be directly connected to a load or the power grid. The first power conversion modules 20a to 20n are all DC / DC conversion modules, the second power conversion module 40 can be a DC / DC conversion module, and the bus 30 is a DC bus 30. The energy storage converter 60 can be a DC / AC conversion module; therefore, the load connected to the energy storage converter 60 is an AC load, and the power grid connected to the energy storage converter 60 is an AC power grid. The second power conversion module 40 can convert the DC power provided by the battery cluster 10 to obtain the target DC power and output the target DC power to the energy storage converter 60. Here, the DC power provided by the battery cluster 10 can be determined by the power current value corresponding to the target power sharing mode or the equalization current value corresponding to the equalization sharing mode, indicating that the DC power provided by the battery cluster 10 can be determined by the final output power of the entire battery cluster 10. The final output power of the entire battery cluster 10 can be either the target power output of the battery cluster 10 under the target power sharing mode or the balanced power output of the battery cluster 10 under the balanced current sharing mode. The energy storage converter 60 can convert the target DC power into AC power and output AC power to AC loads or AC grids to realize the power supply of the battery cluster 10 to AC loads or AC grids.

[0046] like Figure 3 As shown in 3b, when the energy storage system 1 does not include the second power conversion module 40, it also includes an energy storage converter 60. One end of the energy storage converter 60 can be directly connected in parallel with the battery cluster 10, and the other end can be directly connected to a load or the power grid. Here, the energy storage converter 60 can be a DC / AC conversion module; therefore, the load connected to the energy storage converter 60 is an AC load, and the power grid connected to the energy storage converter 60 is an AC power grid. It can be understood that when the energy storage system 1 does not include the second power conversion module 40, the current limiting value of the second power conversion module 40 in the above system control parameters can be the current limiting value of the energy storage converter 60. The energy storage converter 60 can convert the DC power provided by the battery cluster 10 into AC power and output AC power to the AC load or AC power grid, thereby enabling the battery cluster 10 to supply power to the AC load or AC power grid.

[0047] Optionally, in some feasible implementations, when at least two first power conversion modules in the energy storage system are both DC / AC conversion modules, multiple battery packs in the battery cluster can be connected in parallel to the AC bus through at least two first power conversion modules. Please also refer to... Figure 4 , Figure 4 This is yet another structural schematic diagram of the energy storage system provided in this application. For example...Figure 4 As shown, the energy storage system 2 may include a battery cluster 11, at least two first power conversion modules (such as first power conversion modules 21a to 21n), an AC bus 31, a second power conversion module 41, and a battery control system 51. The first power conversion modules 21a to 21n are all DC / AC conversion modules, and the second power conversion module 41 is a DC / DC conversion module. The battery cluster 11 can be connected in parallel to one end of the second power conversion module 41, and the other end of the second power conversion module 41 can be connected to a DC load or a DC power grid. The battery control system 51 can communicate with the battery cluster 11, the first power conversion modules 21a to 21n, and the second power conversion module 41 via powerline carrier (PLC) communication. The battery cluster 11 includes multiple battery packs (battery packs 11a to 11n). Battery pack 11a is connected in parallel to AC bus 31 via a first power conversion module 21a, battery pack 11b is connected in parallel to AC bus 31 via a first power conversion module 21b, and so on, with battery pack 11n connected in parallel to AC bus 31 via a first power conversion module 21n. In other words, each battery pack is connected in parallel to one end of a first power conversion module, and the other end of each first power conversion module is connected in parallel to AC bus 31. The aforementioned second power conversion module 41 can convert the DC power provided by the battery cluster 11 into target DC power and output the target DC power to a DC load or DC grid, thereby enabling the battery cluster 11 to supply power to a DC load or DC grid.

[0048] See Figure 5 , Figure 5 This is a flowchart illustrating the battery management method provided in this application. This method is applicable to energy storage systems (such as those described above). Figures 2 to 4 The provided energy storage system includes a battery cluster, a battery control system, at least two first power conversion modules, a bus, and a second power conversion module. The battery cluster comprises multiple battery packs connected in series. These battery packs are connected in parallel to the bus via at least two first power conversion modules. One end of the second power conversion module is connected in parallel with the battery cluster, and the other end of the second power conversion module is connected to a load or the power grid. Figure 5 As shown, the method includes the following steps S101 to S102:

[0049] Step S101: The battery control system obtains the target current value that the second power conversion module needs to provide to the load or the power grid.

[0050] In some possible embodiments, the battery control system can receive the current instruction value of the second power conversion module issued by the system controller, detect the battery parameters of each battery pack, and determine the system control parameter according to the battery parameters of each battery pack and / or the current instruction value of the second power conversion module. When the system control parameter reaches the parameter threshold, the battery control system can control each first power conversion module to switch its working mode to the target mode, and obtain the target current value required by the second power conversion module to provide to the load or the power grid in the target mode. The parameter threshold can be a preset threshold configured for the energy storage system, and / or a threshold calculated by the battery parameters of each battery pack, which can be determined according to the actual application scenario and is not limited herein.

[0051] In some possible embodiments, when the battery parameters include the state of charge values, the battery control system can determine a state of charge deviation value according to the maximum state of charge value and the minimum state of charge value in the state of charge values of each battery pack, and determine the state of charge deviation value and / or the current instruction value of the second power conversion module as the system control parameter. The state of charge deviation value herein can be the difference between the maximum state of charge value and the minimum state of charge value. It can be understood that the system control parameter can be the state of charge deviation value; or the system control parameter can be the current instruction value of the second power conversion module; or the system control parameter can include the state of charge deviation value and the current instruction value of the second power conversion module, which can be determined according to the actual application scenario and is not limited herein.

[0052] In some possible embodiments, when the energy storage system takes protecting the battery packs in the battery cluster as the primary target, the system control parameter can be the state of charge deviation value. When the state of charge deviation value is greater than a preset state of charge threshold, the battery control system can determine that the system control parameter reaches the parameter threshold, and control each first power conversion module to switch its working mode to the equalization current sharing mode. Further, the battery control system can receive the equalization current value from the system controller, which is the current value required by the second power conversion module to provide to the load or the power grid in the equalization current sharing mode. Alternatively, when the state of charge deviation value is less than or equal to the preset state of charge threshold, the system control parameter can include the state of charge deviation value and the current instruction value of the second power conversion module. When the state of charge deviation value is less than or equal to the preset state of charge threshold, and the current instruction value of the second power conversion module is greater than the current limit value of the second power conversion module, the battery control system can determine that the system control parameter reaches the parameter threshold, and control each first power conversion module to switch its working mode to the target power current sharing mode. Further, the battery control system can receive the power current value issued by the system controller based on the expected power, which is the current value required by the second power conversion module to provide to the load or the power grid in the target power current sharing mode.

[0053] In some possible embodiments, the system control parameter can be a current command value of the second power conversion module when the energy storage system is primarily aimed at meeting the power demand of the load or the grid. The battery control system can determine a current limit value of the second power conversion module based on the battery parameters of the battery packs, which can include temperature, maximum operating current, state of charge value, and state of health value. Further, when the current command value of the second power conversion module is greater than the current limit value of the second power conversion module, the battery control system can determine that the system control parameter reaches the parameter threshold, control the first power conversion modules to switch their operating modes to the target power current sharing mode, and receive the power current value issued by the system controller based on the expected power. Alternatively, when the current command value of the second power conversion module is less than or equal to the current limit value of the second power conversion module, the system control parameter can include a state of charge deviation value and the current command value of the second power conversion module. When the current command value of the second power conversion module is less than or equal to the current limit value of the second power conversion module, and the state of charge deviation value is greater than a preset state of charge threshold, the battery control system can determine that the system control parameter reaches the parameter threshold, control the first power conversion modules to switch their operating modes to the balancing current sharing mode, and receive the balancing current value from the system controller.

[0054] In step S102, the battery control system controls the battery packs to discharge to the bus through the first power conversion modules in parallel with the battery packs, or controls the first power conversion modules in parallel with the battery packs to charge the battery packs, to balance the battery parameters of the battery packs or to make the battery cluster output the target power, based on the target current value and the battery parameters of the battery packs.

[0055] In some possible embodiments, when the target mode is the target power current sharing mode, the battery parameters include maximum operating currents, and the battery control system can control any first power conversion module of any battery pack in parallel to absorb a portion of the maximum operating current of any battery pack other than the power current and output to the bus, or control any first power conversion module described above to absorb current from the bus based on the power current value and output in parallel to the second power conversion module with any battery pack, so that the battery cluster outputs the target power to the second power conversion module. Wherein the current value of the power current is equal to the power current value, and the target power is less than or equal to the expected power. For the convenience of description, the following will be described by taking the battery cluster (such as the battery cluster 10) including the battery pack 10a and the battery pack 10b as an example. In the case that the maximum operating current of the battery pack 10a is greater than the maximum operating current of the battery pack 10b, the battery control system 50 can control the battery pack 10a to output the power current to the second power conversion module 40, and control the battery pack 10a to output a portion of the maximum operating current other than the power current to the first power conversion module 20a. At this time, the battery control system 50 can control the first power conversion module 20a to absorb a portion of the maximum operating current of the battery pack 10a other than the power current and output to the bus 30. Further, the battery control system 50 can control the first power conversion module 20b to absorb current from the bus 30 based on the power current value and output in parallel to the second power conversion module 40 with the battery pack 10b, so that the battery cluster 10 outputs the target power to the second power conversion module 40. Here, the current output in parallel by the battery pack 10b and the first power conversion module 20b can be less than or equal to the power current, and when the current output in parallel by the battery pack 10b and the first power conversion module 20b is less than the power current, the target power is less than the expected power; when the current output in parallel by the battery pack 10b and the first power conversion module 20b is equal to the power current, the target power is equal to the expected power, which can be determined according to actual application scenarios, and is not limited herein. In the case that the target power is equal to the expected power, it can be indicated that the battery cluster 10 outputs the maximum power to the second power conversion module 40.

[0056] In some possible implementation manners, when the target mode is the balanced current sharing mode, the battery parameters include the state of charge value and the maximum operating current. When the state of charge value of the battery pack is greater than the average state of charge value, the battery control system can control the battery pack to discharge through the first power conversion module in parallel connection with the battery pack to the bus, or control the first power conversion module in parallel connection with the battery pack to charge the battery pack when the state of charge value of the battery pack is less than the average state of charge value. Further, the battery control system can control any first power conversion module in parallel connection with any battery pack to absorb a part of the current other than the balancing current in the maximum operating current of any battery pack and output to the bus, or control any first power conversion module to absorb current from the bus to output the balancing current to the second power conversion module and charge any battery pack to balance the battery parameters of the battery packs. The battery parameters of the battery packs can include the state of charge value, the state of health value or other parameters. For convenience of description, the following will be described by taking the battery cluster (for example, the battery cluster 10) including the battery pack 10a and the battery pack 10b as an example. In the case where the maximum operating current of the battery pack 10a is greater than the maximum operating current of the battery pack 10b, the battery control system 50 can control the battery pack 10a to output the balancing current to the second power conversion module 40, and control the battery pack 10a to output a part of the current other than the balancing current in the maximum operating current to the first power conversion module 20a. At this time, the battery control system 50 can control the first power conversion module 20a to absorb a part of the current other than the balancing current in the maximum operating current of the battery pack 10a and output to the bus 30. Further, the battery control system 50 can control the first power conversion module 20b to absorb current from the bus 30 to output the balancing current to the second power conversion module 40 and charge the battery pack 10b to balance the battery parameters of the battery pack 10a and the battery pack 10b in the battery cluster 10.

[0057] In specific implementations, more operations performed by the battery control system in the battery management method provided in the present application can be referred to the implementation manners of the battery control system in the energy storage system and the working principle thereof shown in Figures 2 to 4 The specific implementations of the battery control system in the energy storage system and the working principle thereof shown in

[0058] In the present application, the working mode of the first power conversion module can be switched to the target mode by the system control parameters to balance the battery parameters of the battery packs or make the battery cluster output the target power, the working mode of the first power conversion module can be diversified, the accuracy of the working mode switching and the system stability are improved, and the applicability is stronger.

[0059] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An energy storage system, characterized in that, The energy storage system includes a battery cluster, a battery control system, at least two first power conversion modules, a bus, and a second power conversion module. The battery cluster includes multiple battery packs connected in series. The multiple battery packs are connected in parallel to the bus through the at least two first power conversion modules. One end of the second power conversion module is connected in parallel with the battery cluster, and the other end of the second power conversion module is connected to a load or the power grid. The battery control system is used to obtain the target current value that the second power conversion module needs to provide to the load or the power grid; the battery control system is also used to control the battery pack to discharge to the bus through the first power conversion module connected in parallel with the battery pack based on the target current value and the battery parameters of each battery pack, or to control the first power conversion module connected in parallel with the battery pack to charge the battery pack, so as to balance the battery parameters of each battery pack or make the battery cluster output the target power. The battery control system is used to receive the current command value of the second power conversion module issued by the system controller, and to detect the battery parameters of each battery pack, wherein the battery parameters include the state of charge value. The battery control system is used to determine the state of charge deviation value based on the maximum and minimum state of charge values ​​of each battery pack, and to determine the state of charge deviation value and / or the current command value of the second power conversion module as system control parameters. The battery control system is also used to control each first power conversion module to switch its working mode to the target mode when the system control parameters reach the parameter threshold, and to obtain the target current value that the second power conversion module needs to provide to the load or the power grid in the target mode; The system control parameters include the state-of-charge deviation value and the current command value of the second power conversion module. The battery control system is used to determine that the system control parameters have reached the parameter threshold when the state-of-charge deviation value is less than or equal to a preset state-of-charge threshold and the current command value of the second power conversion module is greater than the current limit value of the second power conversion module, and to control each first power conversion module to switch its operating mode to the target power sharing mode; or The system control parameter is the current command value of the second power conversion module. The battery control system is used to determine that the system control parameter has reached the parameter threshold when the current command value of the second power conversion module is greater than the current limit value of the second power conversion module, and to control each first power conversion module to switch its operating mode to the target power sharing mode; or The system control parameters include the state of charge deviation value and the current command value of the second power conversion module. The battery control system is used to determine that the system control parameters have reached the parameter threshold when the current command value of the second power conversion module is less than or equal to the current limit value of the second power conversion module and the state of charge deviation value is greater than the preset state of charge threshold, and to control each first power conversion module to switch its working mode to the equalization current sharing mode.

2. The energy storage system according to claim 1, characterized in that, The battery control system is also used to determine the current limit value of the second power conversion module based on the battery parameters of each battery pack, including temperature, maximum operating current, state of charge value, and state of health value.

3. The energy storage system according to claim 1 or 2, characterized in that, A battery pack is connected in parallel to the bus via a first power conversion module. The target mode is a target power sharing mode. The battery parameters include the maximum operating current. The battery control system is used to receive the power current value issued by the system controller based on the expected power, and issue the power current value to the first power conversion module connected in parallel with each battery pack. The power current value is the current value that the second power conversion module needs to provide to the load or the power grid under the target power current sharing mode. The first power conversion module connected in parallel with any battery pack in each battery pack is used to absorb a portion of the maximum operating current of any battery pack other than the power current and output it to the bus, or to absorb current from the bus based on the power current value and output it in parallel with any battery pack to the second power conversion module, so that the battery cluster outputs the target power to the second power conversion module. Wherein, the current value of the power current is equal to the power current value, and the target power is less than or equal to the expected power.

4. The energy storage system according to claim 1 or 2, characterized in that, A battery pack is connected in parallel to the bus via a first power conversion module. The target mode is a balanced current sharing mode. The battery parameters include the state of charge value. The battery control system is used to control the battery pack to discharge to the bus through the first power conversion module connected in parallel with the battery pack when the state of charge value of the battery pack is greater than the average state of charge value, or to control the first power conversion module connected in parallel with the battery pack to charge the battery pack when the state of charge value of the battery pack is less than the average state of charge value. The average state of charge (SOC) value is the average of the SOC values ​​of each battery pack.

5. The energy storage system according to claim 4, characterized in that, The battery parameters also include the maximum operating current; The battery control system is used to receive the equalization current value from the system controller and send the equalization current value to the first power conversion module connected in parallel with each battery pack. The equalization current value is the current value that the second power conversion module needs to provide to the load or the power grid in the equalization current sharing mode. The first power conversion module connected in parallel with any battery pack in each battery pack is used to absorb part of the maximum operating current of any battery pack except for the equalization current and output it to the bus, or to absorb current from the bus to output equalization current to the second power conversion module and charge any battery pack, so as to equalize the battery parameters of each battery pack. Wherein, the current value of the balancing current is equal to the value of the balancing current.

6. The energy storage system according to claim 1, characterized in that, Multiple battery packs are connected to the same first power conversion module via a selection switch; The selection switch is used to select a target battery pack from the plurality of battery packs, so that the target battery pack is connected in parallel to the bus through the same first power conversion module. The target battery pack is either the battery pack with the largest battery parameters or the battery pack with the smallest battery parameters among the plurality of battery packs. The battery parameters include the state of charge value or the maximum operating current.

7. A battery management method, characterized in that, The method is applicable to energy storage systems, which include battery clusters, battery control systems, at least two first power conversion modules, a bus, and second power conversion modules. The battery clusters include multiple battery packs connected in series, and the multiple battery packs are connected in parallel to the bus through the at least two first power conversion modules. One end of the second power conversion module is connected in parallel with the battery cluster, and the other end of the second power conversion module is connected to a load or the power grid. The method includes: The battery control system obtains the target current value that the second power conversion module needs to provide to the load or the power grid; based on the target current value and the battery parameters of each battery pack, the battery control system controls the battery pack to discharge to the bus through the first power conversion module connected in parallel with the battery pack, or controls the first power conversion module connected in parallel with the battery pack to charge the battery pack, so as to balance the battery parameters of each battery pack or make the battery cluster output the target power. The battery control system acquires the target current value that the second power conversion module needs to provide to the load or the power grid, including: The battery control system receives the current command value of the second power conversion module issued by the system controller, and detects the battery parameters of each battery pack. The battery parameters include the state of charge (SOC) value. The SOC deviation value is determined based on the maximum and minimum SOC values ​​of each battery pack, and the SOC deviation value and / or the current command value of the second power conversion module are determined as system control parameters. When the system control parameters reach the parameter threshold, the battery control system controls each first power conversion module to switch its operating mode to the target mode, and obtains the target current value that the second power conversion module needs to provide to the load or grid in the target mode; Wherein, the system control parameter is the current command value of the second power conversion module; and when the system control parameter reaches the parameter threshold, the battery control system controls each of the first power conversion modules to switch its operating mode to the target mode, including: When the current command value of the second power conversion module is greater than the current limit value of the second power conversion module, the battery control system determines that the system control parameter has reached the parameter threshold and controls each first power conversion module to switch its operating mode to the target power sharing mode. Alternatively, the system control parameters include the state-of-charge deviation value and the current command value of the second power conversion module; when the system control parameters reach the parameter threshold, the battery control system controls each first power conversion module to switch its operating mode to the target mode, including: When the state of charge deviation value is less than or equal to the preset state of charge threshold and the current command value of the second power conversion module is greater than the current limit value of the second power conversion module, the battery control system determines that the system control parameter has reached the parameter threshold and controls each first power conversion module to switch its operating mode to the target power sharing mode. When the current command value of the second power conversion module is less than or equal to the current limit value of the second power conversion module, and the state of charge deviation value is greater than the preset state of charge threshold, the battery control system determines that the system control parameters have reached the parameter threshold, and controls each first power conversion module to switch its operating mode to the equalization current sharing mode.

8. The method according to claim 7, characterized in that, A battery pack is connected in parallel to the bus via a first power conversion module. The target mode is a target power sharing mode. The target current value is the power current value that the second power conversion module needs to provide to the load or the power grid in the target power sharing mode. The power current value is determined by the expected power. The battery parameters include the maximum operating current. The battery control system, based on the target current value and the battery parameters of each battery pack, controls the battery packs to discharge to the bus through a first power conversion module connected in parallel with the battery packs, or controls the first power conversion module connected in parallel with the battery packs to charge the battery packs, so as to balance the battery parameters of each battery pack or enable the battery cluster to output the target power, including: The battery control system controls any first power conversion module connected in parallel with any battery pack in each battery pack to absorb a portion of the maximum operating current of any battery pack other than the power current and output it to the bus, or controls any first power conversion module to absorb current from the bus based on the power current value and output it in parallel with any battery pack to the second power conversion module, so that the battery cluster outputs the target power to the second power conversion module. Wherein, the current value of the power current is equal to the power current value, and the target power is less than or equal to the expected power.

9. The method according to claim 7, characterized in that, A battery pack is connected in parallel to the bus via a first power conversion module. The target mode is a current sharing mode. The target current value is the equalization current value that the second power conversion module needs to provide to the load or the power grid in the current sharing mode. The battery parameters include the maximum operating current. The battery control system, based on the target current value and the battery parameters of each battery pack, controls the battery packs to discharge to the bus through a first power conversion module connected in parallel with the battery packs, or controls the first power conversion module connected in parallel with the battery packs to charge the battery packs, so as to balance the battery parameters of each battery pack or enable the battery cluster to output the target power, including: The battery control system controls any first power conversion module connected in parallel with any battery pack in each battery pack to absorb a portion of the maximum operating current of any battery pack, excluding the equalization current, and output it to the bus. Alternatively, it controls any first power conversion module to absorb current from the bus to output equalization current to the second power conversion module and charge any battery pack, so as to equalize the battery parameters of each battery pack. Wherein, the current value of the balancing current is equal to the value of the balancing current.

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