Energy storage system and active equalization method

Abstract

The invention provides an energy storage system and an active equalization method, the energy storage system comprises a plurality of battery modules, a DC bus and a battery management system, and each battery module is connected to the DC bus. Under the condition that the multiple battery modules are actively balanced, the battery management system is used for pairing n pairs of battery modules from the multiple battery modules. Wherein the first battery parameters of the n pairs of battery modules are greater than or equal to a first preset parameter value. Each pair of battery modules comprises a first battery module and a second battery module, and the voltage of the first battery module is larger than that of the second battery module. The first battery parameter is an absolute value of a difference value between a maximum voltage value and a minimum voltage value of the battery module. Furthermore, the battery management system is also used for controlling the first battery module in each pair of battery modules to charge the second battery module through the direct current bus. Based on the invention, the active equalization efficiency of the plurality of battery modules can be improved, and the battery capacity difference among the plurality of battery modules can be reduced more quickly.

Description

Technical Field

[0001] The present application relates to the field of battery energy storage technology, and in particular to an energy storage system and an active balancing method. Background Art

[0002] In energy storage systems, power converters are used to convert the DC power output by battery clusters to supply power to loads. Battery clusters are usually composed of multiple battery modules connected in series. However, as the energy storage system runs longer, the battery capacity differences between multiple battery modules in the battery cluster will increase, resulting in capacity mismatch problems in the battery cluster during the charging and discharging process, and thus unable to meet the power requirements of the energy storage system to supply power to the load. Therefore, how to reduce the battery capacity differences between multiple battery modules is one of the technical problems that need to be solved urgently. Summary of the invention

[0003] The present application provides an energy storage system and an active balancing method, which can improve the active balancing efficiency of multiple battery modules and more quickly reduce the battery capacity differences between the multiple battery modules.

[0004] In a first aspect, an embodiment of the present application provides an energy storage system, which includes a plurality of battery modules, a DC bus, and a battery management system, wherein each of the plurality of battery modules is connected to the DC bus. In the case of active balancing of the plurality of battery modules, the battery management system is used to pair n pairs of battery modules from the plurality of battery modules. Among them, the first battery parameters of the n pairs of battery modules are greater than or equal to the first preset parameter value. Each pair of battery modules in the above n pairs of battery modules includes a first battery module and a second battery module, and the voltage of the first battery module is greater than the voltage of the second battery module. The above first battery parameter may be the absolute value of the difference between the maximum voltage value and the minimum voltage value of the battery module. Furthermore, the battery management system is also used to control the first battery module in each pair of battery modules to charge the second battery module through the DC bus to reduce the battery capacity difference between the first battery module and the second battery module in each pair of battery modules. In this active balancing process, the first battery module is in a discharging state and the second battery module is in a charging state. In implementing the embodiments of the present application, since the rated charge and discharge power of the battery module is constant, each pair of battery modules is controlled to be charged and discharged in pairs, which can ensure that the number of battery modules in a charging state is the same as the number of battery modules in a discharging state (that is, both are n), so that each pair of battery modules always operates at full power during the charging and discharging process, thereby improving the active balancing efficiency of multiple battery modules and more quickly reducing the battery capacity differences between multiple battery modules.

[0005] In a possible implementation manner, when actively balancing multiple battery modules, the battery management system is used to select m battery modules from the multiple battery modules. Among them, the first battery parameters of the m battery modules are all greater than or equal to the first preset parameter value. The above-mentioned m battery modules can be sorted from large to small or from small to large according to the voltage of the battery modules. It should be understood that when the first battery parameter of the battery module is greater than or equal to the first preset parameter value, the battery module is a battery module to be balanced. Therefore, all m battery modules are battery modules to be balanced. Further, the battery management system is also used to pair the i-th battery module among the m battery modules with the (m + 1 - i)-th battery module to obtain n pairs of battery modules. Implementing the embodiments of the present application can pair the m battery modules to be balanced in pairs according to the voltage magnitude of the battery modules, so as to ensure that the n pairs of battery modules after pairing always operate at full power during the charge and discharge process, thereby improving the active balancing efficiency of the multiple battery modules.

[0006] In a possible implementation manner, the above energy storage system further includes a plurality of DC converters, and the plurality of DC converters correspond to the plurality of battery modules one by one. Among them, each battery module is connected to the DC bus through the corresponding DC converter. For each pair of battery modules, the DC converter corresponding to the first battery module is used to convert the voltage output by the first battery module and supply power to the DC bus. The DC converter corresponding to the second battery module is used to convert the voltage output by the DC bus and charge the second battery module. Implementing the embodiments of the present application, since the charge and discharge rated power of the DC converter is constant, therefore, by controlling the DC converters corresponding to each pair of battery modules for charge and discharge in pairs, it can be ensured that the number of DC converters in the charging state is the same as the number of DC converters in the discharging state (both are n), so that the DC converters corresponding to each pair of battery modules always operate at full power during the charge and discharge process, thereby improving the active balancing efficiency of the multiple battery modules and reducing the battery capacity difference between the multiple battery modules more quickly. In addition, in this active balancing process, there is no need to adopt a control logic based on an equalization algorithm model, which reduces the control complexity of the DC converter, thereby reducing the maintenance cost of the energy storage system.

[0007] In a possible implementation manner, during the charging and discharging process of the DC converter corresponding to each pair of battery modules, when the output parameter of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, the battery management system is used to control the DC converter corresponding to any pair of battery modules to stop charging and discharging. Among them, the output parameter includes the output voltage or output current of the DC converter. It should be understood that when the output voltage of the DC converter corresponding to any battery module is greater than or equal to the second preset parameter value, an overvoltage fault occurs in the DC converter corresponding to any battery module. And when the output current of the DC converter corresponding to any battery module is greater than or equal to the second preset parameter value, an overcurrent fault occurs in the DC converter corresponding to any pair of battery modules. Implementing the embodiments of the present application, when a recoverable fault (such as an overvoltage fault or an overcurrent fault) occurs in the DC converter corresponding to any battery module, the DC converters corresponding to any pair of battery modules can be controlled in pairs to stop charging and discharging, so as to isolate the faulty DC converter to avoid the spread of the fault to other normally operating DC converters, thereby reducing the potential risk and scheduling strategy complexity brought by the fault. In addition, when the DC converters corresponding to any pair of battery modules stop charging and discharging and no longer perform active balancing, other normally operating DC converters will continue to perform active balancing, which can avoid all the DC converters corresponding to n pairs of battery modules from stopping charging and discharging, thereby reducing the impact on the active balancing efficiency of multiple battery modules.

[0008] In a possible implementation manner, during the fault recovery process of the DC converter corresponding to any pair of battery modules, the output parameter of the DC converter corresponding to any pair of battery modules will gradually decrease to be less than the second preset parameter value, that is, the fault recovery of the DC converter corresponding to any pair of battery modules. At this time, the battery management system is also used to control the DC converter corresponding to any pair of battery modules to resume charging and discharging. Implementing the embodiments of the present application, when the fault of the DC converter corresponding to any pair of battery modules is recovered, the DC converter corresponding to any pair of battery modules can be re-controlled to resume charging and discharging, so as to avoid affecting the active balancing efficiency of multiple battery modules.

[0009] In a possible implementation manner, during the charging and discharging process of the DC converter corresponding to each pair of battery modules, within the first time period, when the number of times the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to the third preset parameter value, that is, when an irrecoverable fault occurs in the DC converter corresponding to any pair of battery modules, the battery management system is used to control the DC converters corresponding to n pairs of battery modules to stop charging and discharging. Implementing the embodiments of the present application can avoid the spread of the irrecoverable fault that occurs in the DC converter to other normally operating DC converters, thereby improving the use safety and service life of the DC converters corresponding to n pairs of battery modules.

[0010] In a possible implementation, after the first battery module in each pair of battery modules charges the second battery module through the DC bus for a second duration, the battery management system is configured to control the DC converters corresponding to n pairs of battery modules to stop charging and discharging. Herein, the second duration is the active balancing duration of the DC converter. Implementing the embodiments of the present application can avoid an excessive increase in the capacity difference between battery modules due to the overlong charging and discharging time of the DC converters corresponding to each pair of battery modules by limiting the active balancing duration of the DC converters, thereby improving the active balancing efficiency of multiple battery modules.

[0011] In a second aspect, an energy storage system provided by an embodiment of the present application includes multiple battery modules, a DC bus, and a battery management system. Each battery module among the multiple battery modules is connected to the DC bus. When performing active balancing on the multiple battery modules, the battery management system is configured to pair s pairs of battery modules from the multiple battery modules. Herein, the second battery parameters of the s pairs of battery modules are all greater than or equal to a fourth preset parameter value. Each pair of battery modules among the above s pairs of battery modules includes a third battery module and a fourth battery module, and the third battery parameter of the third battery module is greater than that of the fourth battery module. The above second battery parameter is the absolute value of the difference between the state of charge of the battery module and the average state of charge of the multiple battery modules, and the third battery parameter is the difference between the state of charge of the battery module and the average state of charge. Further, the battery management system is also configured to control the third battery module in each pair of battery modules to charge the fourth battery module through the DC bus to reduce the battery capacity difference between the third battery module and the fourth battery module in each pair of battery modules. Implementing the embodiments of the present application can enable each pair of battery modules to always operate at full power during the charging and discharging process, thereby improving the active balancing efficiency of multiple battery modules and more quickly reducing the battery capacity difference between multiple battery modules.

[0012] In a possible implementation, when performing active balancing on the multiple battery modules, the battery management system is configured to select j battery modules from the multiple battery modules. Herein, the second battery parameters of the j battery modules are all greater than or equal to a fourth preset parameter value. The above j battery modules can be sorted from large to small or from small to large according to the third battery parameter. Further, the battery management system is also configured to pair the kth battery module among the j battery modules with the (j + 1 - k)th battery module to obtain s pairs of battery modules. Implementing the embodiments of the present application can pair the j battery modules to be balanced in pairs according to the magnitude of the third battery parameter, thereby ensuring that the s pairs of battery modules after pairing always operate at full power during the charging and discharging process, and further improving the active balancing efficiency of multiple battery modules.

[0013] In a possible implementation manner, the above energy storage system further includes a plurality of DC converters, and the plurality of DC converters correspond to the plurality of battery modules one by one. Among them, each battery module is connected to the DC bus through the corresponding DC converter. For each pair of battery modules, the DC converter corresponding to the third battery module is used to perform voltage conversion on the voltage output by the third battery module and supply power to the DC bus. The DC converter corresponding to the above fourth battery module is used to perform voltage conversion on the voltage output by the DC bus and charge the fourth battery module. Implementing the embodiments of the present application, in this active balancing process, there is no need to adopt a control logic based on an equalization algorithm model, which reduces the control complexity of the DC converter, thereby reducing the maintenance cost of the energy storage system.

[0014] In a possible implementation manner, during the charging and discharging process of the DC converter corresponding to each pair of battery modules, when the output parameter of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, the battery management system is used to control the DC converter corresponding to any pair of battery modules to stop charging and discharging. Among them, the output parameter includes the output voltage or output current of the DC converter. Implementing the embodiments of the present application can isolate the faulty DC converter to prevent the fault from spreading to other normally operating DC converters, thereby reducing the potential risk and scheduling strategy complexity brought by the fault. In addition, it can also prevent all the DC converters corresponding to the s pairs of battery modules from stopping charging and discharging, thereby reducing the impact on the active balancing efficiency of the plurality of battery modules.

[0015] In a possible implementation manner, during the process of fault recovery of the DC converter corresponding to any pair of battery modules, the output parameter of the DC converter corresponding to any pair of battery modules will gradually decrease to be less than the second preset parameter value, that is, the fault recovery of the DC converter corresponding to any pair of battery modules. At this time, the battery management system is also used to control the DC converter corresponding to any pair of battery modules to resume charging and discharging, thereby avoiding affecting the active balancing efficiency of the plurality of battery modules.

[0016] In a possible implementation manner, during the charging and discharging process of the DC converter corresponding to each pair of battery modules, within the first time period, when the number of times the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to the third preset parameter value, the battery management system is used to control the DC converters corresponding to the s pairs of battery modules to stop charging and discharging. Implementing the embodiments of the present application can prevent the irrecoverable faults occurring in the DC converter from spreading to other normally operating DC converters, thereby improving the use safety and service life of the DC converters corresponding to the s pairs of battery modules.

[0017] In a possible implementation, after the third battery module in each pair of battery modules charges the fourth battery module through the DC bus for a second duration, the battery management system is used to control the DC converters corresponding to s pairs of battery modules to stop charging and discharging. Implementing the embodiments of the present application can avoid an excessive increase in the capacity difference between battery modules due to the overlong charging and discharging time of the DC converters corresponding to each pair of battery modules by restricting the active equalization duration of the DC converters, thereby improving the active equalization efficiency of multiple battery modules.

[0018] In a third aspect, an embodiment of the present application provides an active equalization method for an energy storage system, which is generally executed by a battery management system in the energy storage system. When actively equalizing multiple battery modules, the battery management system pairs n pairs of battery modules from the multiple battery modules. The energy storage system includes multiple battery modules, a DC bus, and a battery management system, and each battery module in the multiple battery modules is connected to the DC bus. The first battery parameter of each of the above n pairs of battery modules is greater than or equal to a first preset parameter value. Each pair of the above n pairs of battery modules includes a first battery module and a second battery module, and the voltage of the first battery module is greater than that of the second battery module. The above first battery parameter may be the absolute value of the difference between the maximum voltage value and the minimum voltage value of the battery module. Further, the battery management system controls the first battery module in each pair of battery modules to charge the second battery module through the DC bus. Implementing the embodiments of the present application can enable each pair of battery modules to always operate at full power during the charging and discharging process, thereby improving the active equalization efficiency of multiple battery modules and reducing the battery capacity difference between multiple battery modules more quickly.

[0019] In a possible implementation, when actively equalizing multiple battery modules, the battery management system selects m battery modules from the multiple battery modules. The first battery parameter of each of the m battery modules is greater than or equal to a first preset parameter value. The above m battery modules can be sorted in descending order or ascending order according to the voltage of the battery modules. Further, the battery management system pairs the i-th battery module among the m battery modules with the (m + 1 - i)-th battery module to obtain n pairs of battery modules.

[0020] In a possible implementation, for each pair of battery modules, the battery management system controls the DC converter corresponding to the first battery module to perform voltage conversion on the voltage output by the first battery module and supply power to the DC bus, and controls the DC converter corresponding to the second battery module to perform voltage conversion on the voltage output by the DC bus and charge the second battery module. The energy storage system further includes multiple DC converters, which are in one-to-one correspondence with the multiple battery modules, and each battery module is connected to the DC bus through the corresponding DC converter.

[0021] In a possible implementation manner, when the output parameters of the DC converter corresponding to any pair of battery modules are greater than or equal to the second preset parameter value, the battery management system controls the DC converter corresponding to any pair of battery modules to stop charging and discharging. Wherein, the output parameters include the output voltage or output current of the DC converter.

[0022] In a possible implementation manner, during the process of fault recovery of the DC converter corresponding to any pair of battery modules, the output parameters of the DC converter corresponding to any pair of battery modules will gradually decrease to be less than the second preset parameter value, that is, the fault recovery of the DC converter corresponding to any pair of battery modules. At this time, the battery management system controls the DC converter corresponding to any pair of battery modules to resume charging and discharging.

[0023] In a possible implementation manner, within the first time period, when the number of times that the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to the third preset parameter value, that is, when the DC converter corresponding to any pair of battery modules has an irrecoverable fault, the battery management system controls the DC converters corresponding to n pairs of battery modules to stop charging and discharging.

[0024] In a possible implementation manner, after the first battery module in each pair of battery modules charges the second battery module through the DC bus for the second time period, the battery management system controls the DC converters corresponding to n pairs of battery modules to stop charging and discharging.

[0025] In a fourth aspect, an active equalization method for an energy storage system provided by an embodiment of the present application, when actively equalizing multiple battery modules, the battery management system pairs s pairs of battery modules from the multiple battery modules. Wherein, the energy storage system includes multiple battery modules, a DC bus, and a battery management system, and each battery module in the multiple battery modules is connected to the DC bus. The second battery parameters of the above s pairs of battery modules are all greater than or equal to the fourth preset parameter value. Each pair of battery modules in the above s pairs of battery modules includes a third battery module and a fourth battery module, and the third battery parameter of the third battery module is greater than the third battery parameter of the third battery module. The above second battery parameter is the absolute value of the difference between the state of charge of the battery module and the average value of the states of charge of the multiple battery modules, and the third battery parameter is the difference between the state of charge of the battery module and the average value of the states of charge. Further, the battery management system controls the third battery module in each pair of battery modules to charge the fourth battery module through the DC bus. Implementing the embodiment of the present application can enable each pair of battery modules to always operate at full power during the charging and discharging process, thereby improving the active equalization efficiency of the multiple battery modules and more quickly reducing the battery capacity difference between the multiple battery modules.

[0026] In a possible implementation, when actively balancing multiple battery modules, the battery management system selects j battery modules from the multiple battery modules. Among them, the second battery parameters of the j battery modules are all greater than or equal to the fourth preset parameter value. The above j battery modules can be sorted from largest to smallest or from smallest to largest according to the third battery parameter. Further, the battery management system also pairs the k-th battery module among the j battery modules with the (j + 1 - k)-th battery module to obtain s pairs of battery modules.

[0027] In a possible implementation, for each pair of battery modules, the battery management system controls the DC converter corresponding to the third battery module to convert the voltage output by the third battery module and supply power to the DC bus, and controls the DC converter corresponding to the fourth battery module to convert the voltage output by the DC bus and charge the fourth battery module. The energy storage system further includes a plurality of DC converters, the plurality of DC converters correspond to the plurality of battery modules one by one, and each battery module is connected to the DC bus through the corresponding DC converter.

[0028] In a possible implementation, during the process of actively balancing multiple battery modules, when the output parameter of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, the battery management system controls the DC converter corresponding to any pair of battery modules to stop charging and discharging. The output parameter includes the output voltage or output current of the DC converter.

[0029] In a possible implementation, during the process of fault recovery of the DC converter corresponding to any pair of battery modules, the output parameter of the DC converter corresponding to any pair of battery modules will gradually decrease to be less than the second preset parameter value, that is, the fault recovery of the DC converter corresponding to any pair of battery modules. At this time, the battery management system also controls the DC converter corresponding to any pair of battery modules to resume charging and discharging.

[0030] In a possible implementation, within the first time period, when the number of times the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to the third preset parameter value, the battery management system controls the DC converters corresponding to the s pairs of battery modules to stop charging and discharging.

[0031] In a possible implementation, after the third battery module in each pair of battery modules charges the fourth battery module through the DC bus for the second time period, the battery management system controls the DC converters corresponding to the s pairs of battery modules to stop charging and discharging.

[0032] It should be understood that the implementations and beneficial effects of the above-mentioned multiple aspects of the present application can be mutually referred to. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of an energy storage system provided by an embodiment of the present application;

[0034] Figure 2 It is a schematic circuit diagram of an energy storage system provided by an embodiment of the present application;

[0035] Figure 3 It is another schematic circuit diagram of an energy storage system provided by an embodiment of the present application;

[0036] Figure 4 It is a pairing schematic diagram of multiple battery modules provided by an embodiment of the present application;

[0037] Figure 5 It is an interaction schematic diagram between a battery control unit and a battery management unit when a recoverable fault occurs in a DC converter provided by an embodiment of the present application;

[0038] Figure 6 It is an interaction schematic diagram between a battery control unit and a battery management unit when an irrecoverable fault occurs in a DC converter provided by an embodiment of the present application;

[0039] Figure 7 It is a schematic flowchart of an active equalization method for an energy storage system provided by an embodiment of the present application;

[0040] Figure 8 It is another schematic flowchart of an active equalization method for an energy storage system provided by an embodiment of the present application. Detailed implementation manners

[0041] The energy storage system provided by the present application is applicable to commercial energy storage systems, household energy storage systems, photovoltaic energy storage power generation systems, power battery systems, and other fields that require energy storage systems for energy storage and power backup, and is used to achieve energy balance between battery modules.

[0042] Refer to Figure 1 , Figure 1 It is a schematic structural diagram of an energy storage system provided by an embodiment of the present application. As Figure 1As shown in the figure, the energy storage system includes battery modules 11a, 11b, …, 11z, a DC bus 12, a battery management system 13, and an energy storage inverter 14. Each of the battery modules 11a to 11z is connected to the DC bus 12. The battery modules 11a to 11z are connected in series and then connected to the input end of the energy storage inverter 14, and the output end of the energy storage inverter 14 is used to connect to the power grid 15. When the energy storage system supplies power to the power grid 15, the energy storage inverter 14 is used to invert the DC voltage after the battery modules 11a to 11z are connected in series into an AC voltage and supply power to the power grid 15. During the process of supplying power to the power grid 15, the battery management system 13 is used to achieve energy balance between the battery modules 11a to 11z through the DC bus 12, which can reduce the battery capacity difference between the battery modules 11a to 11z, thereby avoiding the problem of capacity mismatch during the charge and discharge process of the battery modules, and further improving the power supply reliability of the energy storage system.

[0043] It can be understood that the above energy storage system may further include other devices. Exemplarily, the other devices include a battery sampling module and a safety system. The battery sampling module is used to collect battery parameters of the battery module, such as the first battery parameter, the second battery parameter, or the third battery parameter in the following embodiments. The safety system is used to perform overcharge protection, over-discharge protection, and short-circuit protection on the battery module, thereby avoiding damage to the battery module and improving the safety of the energy storage system. The above is only an example, and the embodiments of the present application do not limit the specific structure of the energy storage system.

[0044] The following will combine Figures 2 to 6 to give an example and explanation of the structure of the energy storage system provided by the present application and two active balancing methods.

[0045] Refer to Figure 2 , Figure 2 which is a circuit schematic diagram of the energy storage system provided by the embodiments of the present application. As Figure 2 shown, the energy storage system 2 includes battery modules 21a to 21u, a DC bus 22, and a battery management system 23. Each of the battery modules 21a to 21u is connected to the DC bus 22. The battery modules 21a to 21u can be connected in series. Optionally, the battery modules 21a to 21u can also be connected in parallel. Exemplarily, each battery module can be a battery pack or a battery cell, where the battery pack can be composed of multiple battery cells connected in series and parallel.

[0046] The following will explain one of the active balancing methods for the battery modules 21a to 21u.

[0047] In the case of active equalization of battery modules 21a to 21u, the battery management system 23 is used to pair n pairs of battery modules from battery modules 21a to 21u. Here, the active equalization is a process of transferring the energy of the high-energy battery modules among battery modules 21a to 21u to the low-energy battery modules to achieve energy transfer equalization, so as to reduce the battery capacity difference among battery modules 21a to 21u and finally reach the balanced state. Among them, the first battery parameter of the n pairs of battery modules is greater than or equal to the first preset parameter value. The above-mentioned first battery parameter is the absolute value of the difference between the maximum voltage value and the minimum voltage value of the battery module. Exemplarily, the first preset parameter value can be 10 mV or 30 mV. Each pair of battery modules in the above-mentioned n pairs of battery modules includes a first battery module and a second battery module, and the voltage of the first battery module is greater than that of the second battery module.

[0048] Further, the battery management system 23 is also used to control the first battery module in each pair of battery modules to charge the second battery module through the DC bus 22, so as to reduce the battery capacity difference between the first battery module and the second battery module in each pair of battery modules. During this active equalization process, the first battery module is in the discharge state, and the second battery module is in the charging state.

[0049] Implementing the embodiments of the present application, since the charge and discharge rated power of the battery module is constant, therefore, by controlling each pair of battery modules to charge and discharge in pairs, it can be ensured that the number of battery modules in the charging state is the same as the number of battery modules in the discharge state (i.e., both are n), so that each pair of battery modules always operates at full power during the charge and discharge process, thereby improving the active equalization efficiency of battery modules 21a to 21u and more quickly reducing the battery capacity difference among battery modules 21a to 21u.

[0050] In some feasible implementation manners, in the case of active equalization of battery modules 21a to 21u, the above-mentioned battery management system 23 is used to select m battery modules from battery modules 21a to 21u. Among them, the first battery parameter of the m battery modules is greater than or equal to the first preset parameter value. The above-mentioned m battery modules are sorted from large to small or from small to large according to the voltage of the battery module. It should be understood that when the first battery parameter of the battery module is greater than or equal to the first preset parameter value, the battery module is a battery module to be equalized. Therefore, all m battery modules are battery modules to be equalized. Further, the battery management system 23 is also used to pair the i-th battery module and the (m + 1 - i)-th battery module among the m battery modules to obtain n pairs of battery modules. It should be understood that when m is an even number, n is 0.5m. When m is an odd number, n is the value obtained by rounding down 0.5m (i.e., ), and the One battery module is the remaining battery module paired during the active equalization process and is not equalized during this active equalization process. Implementing the embodiments of the present application can pair the m battery modules to be equalized in pairs according to the voltage magnitudes of the battery modules, so as to ensure that the n pairs of battery modules after pairing always operate at full power during charge and discharge, thereby improving the active equalization efficiency of battery modules 21a to 21u.

[0051] It can be understood that when the m battery modules are sorted from largest to smallest according to the voltage of the battery modules, the first battery module in each pair of battery modules is the i-th battery module, and the second battery module is the (m + 1 - i)-th battery module. When the m battery modules are sorted from smallest to largest according to the voltage of the battery modules, the first battery module in each pair of battery modules is the (m + 1 - i)-th battery module, and the second battery module is the i-th battery module.

[0052] In some feasible implementation manners, as Figure 2 shown, the above energy storage system 2 further includes DC converters 24a to 24u, and the battery modules 21a to 21u correspond to the DC converters 24a to 24u one by one. Among them, each battery module is connected to the DC bus 22 through the corresponding DC converter. Specifically, the battery module 21a is connected to the DC bus 22 through the corresponding DC converter 24a,..., and the battery module 21u is connected to the DC bus 22 through the corresponding DC converter 24u. Exemplarily, each DC converter is a DC converter with bidirectional buck-boost function. Among them, the DC converter can also be called an active equalization module (AEM), which is used to achieve the power distribution of the battery modules by actively scheduling the charge and discharge of the battery modules.

[0053] For each pair of battery modules among the above-mentioned n pairs of battery modules, the DC converter corresponding to the first battery module is used to convert the voltage output by the first battery module and supply power to the DC bus 22. The DC converter corresponding to the second battery module is used to convert the voltage output by the DC bus 22 and charge the second battery module. By implementing the embodiments of the present application, since the charge-discharge rated power of the DC converter is constant, controlling the DC converters corresponding to each pair of battery modules for charge and discharge in pairs can ensure that the number of DC converters in the charging state is the same as the number of DC converters in the discharging state (i.e., both are n), so that the DC converters corresponding to each pair of battery modules always operate at full power during the charge and discharge process, thereby improving the active balancing efficiency of the battery modules 21a to 21u and reducing the battery capacity difference between the battery modules 21a to 21u more quickly. In addition, during this active balancing process, there is no need to adopt a control logic based on an equalization algorithm model, which reduces the control complexity of the DC converter, thereby reducing the maintenance cost of the energy storage system 2. Herein, the full power of the DC converter refers to the maximum power that the DC converter can stably output for a long time under normal working conditions.

[0054] In some feasible embodiments, during the charging and discharging process of the DC converters corresponding to each pair of battery modules, when the output parameters of the DC converter corresponding to any pair of battery modules are greater than or equal to the second preset parameter value, the battery management system 23 is configured to control the DC converter corresponding to any pair of battery modules to stop charging and discharging. Among them, the output parameters include the output voltage or output current of the DC converter. It should be understood that when the output voltage of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, an overvoltage fault occurs in the DC converter corresponding to any pair of battery modules. Exemplarily, when the DC converter charges the corresponding battery module, the second preset parameter value can be 220V or 222V. When the DC converter supplies power to the DC bus 22, the second preset parameter value can be 451V, 465V or 475V. When the output current of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, an overcurrent fault occurs in the DC converter corresponding to any pair of battery modules. Exemplarily, when the DC converter charges the corresponding battery module, the second preset parameter value can be 7A, 8A or 16A. When the DC converter supplies power to the DC bus 22, the second preset parameter value can be 20A. Implementing the embodiments of the present application, when a recoverable fault (such as an overvoltage fault or an overcurrent fault) occurs in the DC converter corresponding to any pair of battery modules, the DC converters corresponding to any pair of battery modules can be controlled in pairs to stop charging and discharging, so as to isolate the faulty DC converter to prevent the fault from spreading to other normally operating DC converters, thereby reducing the potential risks and scheduling strategy complexity brought by the fault. In addition, when the DC converters corresponding to any pair of battery modules stop charging and discharging and no longer perform active balancing, other normally operating DC converters will continue to perform active balancing, which can prevent all the DC converters corresponding to n pairs of battery modules from stopping charging and discharging, thereby reducing the impact on the active balancing efficiency of the battery modules 21a to 21u.

[0055] In some feasible embodiments, during the process of fault recovery of the DC converter corresponding to any pair of battery modules, the output parameters of the DC converter corresponding to any pair of battery modules will gradually decrease to be less than the second preset parameter value. At this time, the battery management system 23 is further configured to control the DC converter corresponding to any pair of battery modules to resume charging and discharging. Implementing the embodiments of the present application, when the fault of the DC converter corresponding to any pair of battery modules is recovered, the DC converter corresponding to any pair of battery modules can be re-controlled to resume charging and discharging, so as to avoid affecting the active balancing efficiency of the battery modules 21a to 21u.

[0056] In some feasible embodiments, during the charging and discharging process of the DC converters corresponding to each pair of battery modules, when the output voltage of the DC converter corresponding to any pair of battery modules is less than or equal to a preset voltage value, that is, when the DC converter corresponding to any pair of battery modules has an undervoltage fault, the battery management system 23 is used to control the DC converter corresponding to any pair of battery modules to stop charging and discharging. Exemplarily, when the DC converter charges the corresponding battery module, the preset voltage value can be 154V. When the DC converter supplies power to the DC bus 22, the preset voltage value can be 315V. During the process of fault recovery of the DC converter corresponding to any pair of battery modules, the output voltage of the DC converter corresponding to any pair of battery modules will gradually increase to be greater than the preset voltage value. At this time, the battery management system 23 is also used to control the DC converter corresponding to any pair of battery modules to resume charging and discharging. Implementing the embodiments of the present application, when the DC converter corresponding to any pair of battery modules has a recoverable fault (such as an undervoltage fault), it is possible to control the DC converters corresponding to any pair of battery modules to stop charging and discharging and no longer perform active balancing, while the other normally operating DC converters will continue to perform active balancing, which can avoid all the DC converters corresponding to n pairs of battery modules from stopping charging and discharging, thereby reducing the impact on the active balancing efficiency of the battery modules 21a to 21u. In addition, when the undervoltage fault of the DC converter corresponding to any pair of battery modules is recovered, it is possible to re-control the DC converter corresponding to any pair of battery modules to resume charging and discharging, thereby avoiding affecting the active balancing efficiency of the battery modules 21a to 21u.

[0057] It can be understood that during the charging and discharging process of the DC converters corresponding to each pair of battery modules, within a first time period, when the number of times the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to a third preset parameter value, that is, when the DC converter corresponding to any pair of battery modules has an irrecoverable fault, the battery management system 23 is used to control the DC converters corresponding to n pairs of battery modules to stop charging and discharging. Exemplarily, the first time period can be 5s, and the third preset parameter value can be 10 times. It can be understood that the reason for the DC converter corresponding to any pair of battery modules to stop charging and discharging can be an overvoltage fault, an overcurrent fault or an undervoltage fault, which is not limited herein. Implementing the embodiments of the present application can avoid the spread of the irrecoverable fault of the DC converter to other normally operating DC converters, thereby improving the use safety and service life of the DC converters corresponding to n pairs of battery modules.

[0058] It can be understood that when the DC converter corresponding to the battery module has different faults (such as recoverable faults or irrecoverable faults), the battery management system 23 will adopt different scheduling strategies to control the DC converters corresponding to n pairs of battery modules, and the scheduling method is more flexible.

[0059] In some feasible embodiments, when the DC converters corresponding to each pair of battery modules do not fail, or the faults that occur in the DC converters corresponding to any pair of battery modules have been recovered, after the first battery module in each pair of battery modules charges the second battery module through the DC bus 22 for a second duration, the battery management system 23 is configured to control the DC converters corresponding to n pairs of battery modules to stop charging and discharging. Wherein, the second duration is the active equalization duration of the DC converter. Exemplarily, the second duration can be 5 minutes or 10 minutes. Implementing the embodiments of the present application can avoid an excessive increase in the capacity difference between battery modules due to the too long charging and discharging time of the DC converters corresponding to each pair of battery modules by restricting the active equalization duration of the DC converters, thereby improving the active equalization efficiency of the battery modules 21a to 21u.

[0060] The following will combine Figures 3 to 6 to specifically describe one of the active equalization methods for the battery modules 21a to 21u.

[0061] When the battery modules 21a to 21u include eight battery modules, specifically as Figure 3 shown, the above Figure 2 shown battery modules 21a to 21u include battery module 21a, battery module 21b, battery module 21c, battery module 21d, battery module 21e, battery module 21f, battery module 21g, and battery module 21u. Correspondingly, the DC converters 24a to 24u include DC converter 24a, DC converter 24b, DC converter 24c, DC converter 24d, DC converter 24e, DC converter 24f, DC converter 24g, and DC converter 24u. Correspondingly, the above Figure 2 shown battery management system 23 includes a battery control unit (BCU) 231, battery management units (BMUs) 232a, 232b, 232c, 232d, 232e, 232f, 232g, and 232u. Wherein, the battery management units 232a to 232u correspond to the battery modules 21a to 21u one by one. The above battery control unit 231 can transmit data to the battery management units 232a to 232u through the CAN bus, such as issuing a power-on instruction or a power-off instruction.

[0062] In the case of active equalization of battery modules 21a to 21u, the battery control unit 231 is configured to select m (e.g., 5) battery modules from the battery modules 21a to 21u. Exemplarily, as Figure 4 shown, after the 5 battery modules are sorted in ascending order of the voltage of the battery modules, they sequentially include battery module 21a, battery module 21b, battery module 21c, battery module 21g, and battery module 21u. In Figure 4 , the gray part in the battery module is used to indicate the voltage magnitude of the battery module. Further, the battery control unit 231 is configured to pair the battery module 21a with the smallest voltage among the battery modules and the battery module 21u with the largest voltage, and pair the battery module 21b with the second smallest voltage and the battery module 21g with the second largest voltage to obtain n (e.g., 2) pairs of battery modules. Among them, the battery module 21a and the battery module 21b are the second battery modules in the 2 pairs of battery modules, and the battery module 21g and the battery module 21u are the first battery modules in the 2 pairs of battery modules. The above-mentioned battery module 21a and battery module 21u are the first pair of battery modules in the 2 pairs of battery modules, and the battery module 21b and battery module 21g are the second pair of battery modules in the 2 pairs of battery modules. At this time, the battery module 21c is not paired and is the remaining battery module in the pairing process of this active equalization.

[0063] After obtaining two pairs of battery modules through pairing, the battery control unit 231 is configured to send a startup command to the battery management unit corresponding to each pair of battery modules in the two pairs of battery modules. Further, the battery management unit corresponding to the first battery module in each pair of battery modules is configured to, in response to the startup command, control the DC converter corresponding to the first battery module to perform voltage conversion on the voltage output by the first battery module and supply power to the DC bus 22. At this time, the battery management unit corresponding to the second battery module in each pair of battery modules is configured to, in response to the startup command, control the voltage output to the DC bus 22 to perform voltage conversion and charge the second battery module. In a specific implementation, when the DC converter includes a control chip, an auxiliary power supply, a relay, and a DC conversion circuit, the relay is connected between the control chip and the auxiliary power supply. Herein, the auxiliary power supply may also be arranged outside the DC converter, and this is not limited herein. Taking the startup operation of the DC converter 24u corresponding to the battery module 21u as an example for illustration, the above-mentioned battery management unit 232u is configured to, in response to the startup command, draw power from the battery module 21u, perform conversion, and supply power to the control chip in the DC converter 24u. Further, the control chip in the DC converter 24u is configured to receive the power supply, control the relay to conduct to enable the auxiliary power supply to supply power to the control chip, and control the DC converter 24u to supply power to the DC bus 22. It should be noted that after the DC converter 24u starts up and runs, the battery management unit 232u does not need to continue to supply power to the control chip in the DC converter 24u, but the auxiliary power supply in the DC converter 24u supplies power to the control chip, thereby avoiding consuming the power of the battery module 21u. It can be understood that for the specific operations of the startup and operation of the DC converters corresponding to the other battery modules in the two pairs of battery modules, reference may be made to the specific operations of the startup and operation of the above-mentioned DC converter 24u, and details are not described herein again. Implementing the embodiments of the present application, by adopting the structure combining the battery control unit 231 and the battery management units 232a to 232u, to control the charging and discharging of the DC converters corresponding to each pair of battery modules in pairs, not only can the complexity and cost of the energy storage system 2 be reduced, but also the overall performance and stability of the energy storage system 2 can be improved.

[0064] During the charging and discharging process of the DC converters corresponding to two pairs of battery modules, such as Figure 5As shown, when a recoverable fault occurs in one of the DC converters corresponding to the second pair of battery modules, for example, when a recoverable fault occurs in the DC converter 24b corresponding to the battery module 21b, the battery management unit 232b corresponding to the battery module 21b is configured to output a first warning message to the battery control unit 231 when the output parameter of the DC converter 24b is greater than or equal to the second preset parameter value, or the output voltage of the DC converter 24b is less than or equal to the preset voltage value. Further, the battery control unit 231 is configured to parse the first warning message to obtain the message corresponding to the first warning message, and when the message corresponding to the first warning message is the same as the message corresponding to the occurrence of a recoverable fault in the DC converter, send a shutdown command to the battery management unit 232b and the battery management unit 232g. Further still, the battery management unit 232g is configured to control the DC converter 24g to stop discharging in response to the shutdown command. The above battery management unit 232b is configured to control the DC converter 24b to stop charging in response to the shutdown command. Optionally, the battery management unit 232b is configured to control the DC converter 24b to stop charging and output a first warning message to the battery control unit 231 when the output parameter of the DC converter 24b is greater than or equal to the second preset parameter value, or the output voltage of the DC converter 24b is less than or equal to the preset voltage value. Further, the battery control unit 231 is configured to send a shutdown command to the battery management unit 232g corresponding to the battery module 21g in response to the first warning message. Further still, the battery management unit 232g is configured to control the DC converter 24g to stop discharging in response to the shutdown command. Implementing the embodiments of the present application can isolate the faulty DC converter (such as the DC converter 24b) faster, thereby improving the safety and service life of the DC converter.

[0065] During the process of fault recovery of the DC converter 24b, the above battery management unit 232b is further configured to output a startup request command to the battery control unit 231 when the output parameter of the DC converter 24b is less than the second preset parameter value, or the output voltage of the DC converter 24b is greater than the preset voltage value. Further, the battery control unit 231 is further configured to send a startup command to the battery management unit 232b and the battery management unit 232g in response to the startup request command. Further still, the battery management unit 232g is configured to control the DC converter 24g to resume discharging in response to the startup command. The above battery management unit 232b is configured to control the DC converter 24b to resume charging in response to the startup command.

[0066] When an irrecoverable fault occurs in the DC converter 24b, such as Figure 6As shown, when the number of times the DC converters 24b and 24g stop charging and discharging within the first time period is greater than or equal to the third preset parameter value, the battery management unit 232b is further configured to control the DC converter 24b to stop charging and output a second warning message to the battery control unit 231. Further, the battery control unit 231 is further configured to parse the second warning message to obtain the message corresponding to the second warning message. When the message corresponding to the second warning message is the same as the message corresponding to an irrecoverable fault occurring in the DC converter, a shutdown instruction is sent to the battery management unit 232a, the battery management unit 232g, and the battery management unit 232u. Even further, the battery management unit 232a is configured to control the DC converter 24a to stop charging in response to the shutdown instruction. The battery management unit 232g is configured to control the DC converter 24g to stop discharging in response to the shutdown instruction. The battery management unit 232u is configured to control the DC converter 24u to stop discharging in response to the shutdown instruction.

[0067] In the case where the DC converters corresponding to the two pairs of battery modules do not fail or the faults of the DC converters have been recovered, after the first battery module in each pair of battery modules charges the second battery module through the DC bus 22 for the second time period, the battery control unit 231 is further configured to send a shutdown instruction to the battery management unit corresponding to each pair of battery modules. Further, the battery management unit corresponding to each pair of battery modules is configured to control the DC converters corresponding to each pair of battery modules to stop charging and discharging in response to the shutdown instruction. At this time, the DC converters corresponding to the two pairs of battery modules are all shut down and no longer perform active balancing, that is, the active balancing of the battery modules ends this time. In a specific implementation, taking the shutdown of the DC converter 24u corresponding to the battery module 21u as an example, the battery management unit 232u is configured to output a shutdown instruction to the control chip in the DC converter 24u in response to the shutdown instruction. Further, the control chip in the DC converter 24u is configured to control the DC conversion circuit in the DC converter 24u to stop outputting in response to the shutdown instruction. At this time, the relay still remains in the conducting state. It can be understood that for the specific operations of shutting down the DC converters corresponding to the other battery modules in the two pairs of battery modules, reference can be made to the specific operations of shutting down the DC converter 24u above, which will not be elaborated here. Implementing the embodiments of the present application to control the DC converters corresponding to each pair of battery modules to shut down when the active balancing time period reaches the second time period can reduce the number of times of frequently turning off the relays in the DC converters, thereby extending the service life of the relays in the DC converters.

[0068] In some feasible embodiments, the battery control unit 231 is further configured to, when the duration for which both DC converters corresponding to the two pairs of battery modules stop charging and discharging is greater than or equal to the first shutdown duration, re-pair x pairs of battery modules from the five battery modules and perform active balancing on the x pairs of battery modules. Specifically, reference may be made to the description of performing active balancing on two pairs of battery modules in the foregoing embodiments, which will not be elaborated herein. Among them, the first shutdown duration may be specifically determined by the working state of the battery modules. It should be understood that when the first battery module that needs to discharge and the second battery module that needs to be charged in each pair of the x pairs of battery modules are the same as those in each pair of the two pairs of battery modules, the first shutdown duration is negatively correlated with the voltage difference or state of charge difference between the two pairs of battery modules after the completion of this active balancing. Exemplarily, the first shutdown duration may be 0 minutes, 5 minutes, 10 minutes, or 15 minutes. Optionally, when the first battery module that needs to discharge and the second battery module that needs to be charged in each pair of the x pairs of battery modules are different from those in each pair of the two pairs of battery modules, such as when the first battery module that needs to discharge and the second battery module that needs to be charged are interchanged or the battery modules remaining after pairing in this active balancing (such as battery module 21c) are added, the first shutdown duration is greater than the first shutdown duration when the first battery module that needs to discharge and the second battery module that needs to be charged in each pair of the x pairs of battery packs are the same as those in each pair of the two pairs of battery packs.

[0069] It can be understood that when the first battery module that needs to discharge and the second battery module that needs to be charged in each pair of the x pairs of battery modules are the same as those in each pair of the two pairs of battery modules, it can indicate that the voltage fluctuations of the two pairs of battery modules are small, while when the first battery module that needs to discharge and the second battery module that needs to be charged in each pair of the x pairs of battery modules are different from those in each pair of the two pairs of battery modules, it can indicate that the voltage fluctuations of the two pairs of battery modules are large. Therefore, it is necessary to extend the first shutdown duration (such as 20 minutes) to stabilize the voltage of the two pairs of battery modules.

[0070] By implementing the embodiments of the present application, the voltage of the battery modules fluctuates after the active balancing is completed. Therefore, it is necessary to let it stand for a period of time (such as greater than or equal to the first shutdown duration) to stabilize the voltage of the battery modules, and then perform active balancing again after the voltage of the battery modules is stabilized, thereby improving the active balancing efficiency of the battery modules 21a to 21u.

[0071] In some feasible embodiments, when the duration that the DC converters corresponding to 2 pairs of battery modules both stop charging and discharging is greater than or equal to the first shutdown duration, and some of the battery modules in the 2 pairs of battery modules are not among the x pairs of battery modules, the battery control unit 231 is used to control the DC converters corresponding to some of the battery modules in the 2 pairs of battery modules to enter the sleep state. In a specific implementation, the battery control unit 231 is used to send a sleep command to the battery management units corresponding to some of the battery modules in the 2 pairs of battery modules. Further, the battery management units corresponding to some of the battery modules are used to, in response to the sleep command, output a sleep command to the control chips in the DC converters corresponding to some of the battery modules. Even further, the control chips in the DC converters corresponding to some of the battery modules are used to, in response to the sleep command, control the relays in the DC converters corresponding to some of the battery modules to disconnect. At this time, the auxiliary power supply in the DC converters corresponding to some of the battery modules stops drawing power from the battery modules to supply power to the control chips, which can avoid excessive consumption of the power of some of the battery modules, thereby improving the active balancing efficiency of the battery modules 21a to 21u.

[0072] In some feasible embodiments, when the duration that the DC converters corresponding to 2 pairs of battery modules are both shut down is greater than or equal to the first shutdown duration, and the x pairs of battery modules are the same as the 2 pairs of battery modules, the battery control unit 231 does not need to control the DC converters corresponding to the x pairs of battery modules to enter the sleep state, but directly controls the DC converters corresponding to the x pairs of battery modules to perform active balancing. Implementing the embodiments of the present application can reduce the number of times of frequently turning off the relays in the DC converters, thereby extending the service life of the relays in the DC converters.

[0073] It can be understood that the above battery management system 23 (i.e., the battery control unit 231 and the battery management units 232a to 232u) can repeatedly execute the above operations of performing active balancing on the paired battery modules, continuously reducing the battery capacity difference between the battery modules 21a to 21u until the energy balance between the battery modules 21a to 21u is achieved, thereby avoiding the problem of capacity mismatch of the battery modules during the charging and discharging process.

[0074] Another active balancing method for the battery modules 21a to 21u will be described below.

[0075] In some feasible embodiments, when active balancing is performed on battery modules 21a to 21u, the battery management system 23 is configured to pair s pairs of battery modules from battery modules 21a to 21u. Among them, the second battery parameters of the s pairs of battery modules are all greater than or equal to a fourth preset parameter value. Exemplarily, the fourth preset parameter value can be 95%. Each pair of battery modules in the above s pairs of battery modules includes a third battery module and a fourth battery module, and the third battery parameter of the third battery module is greater than the third battery parameter of the fourth battery module. The above second battery parameter is the absolute value of the difference between the state of charge (SOC) of the battery module and the average value of the state of charge of battery modules 21a to 21u, and the third battery parameter is the difference between the state of charge of the battery module and the average value of the state of charge. Further, the battery management system 23 is further configured to control the third battery module in each pair of battery modules to charge the fourth battery module through the DC bus 22, so as to reduce the battery capacity difference between the third battery module and the fourth battery module in each pair of battery modules. Implementing the embodiments of the present application can enable each pair of battery modules to always operate at full power during the charge and discharge process, thereby improving the active balancing efficiency of battery modules 21a to 21u and more quickly reducing the battery capacity difference between battery modules 21a to 21u.

[0076] In some feasible embodiments, the state of charge SOC1 of the above battery module can be determined by the following formula (1).

[0077] SOC1 = (100% - SOC2) * SOC3 * SOH, Formula (1)

[0078] In Formula (1), SOC2 is used to represent the current state of charge of the battery module, SOC3 is used to represent the rated capacity of the battery module, and SOH is used to represent the effective value of the health state of the battery module. The battery management system 23 is configured to determine the state of charge SOC1 of each battery module in battery modules 21a to 21u according to the above formula (1), and further obtain the average value of the state of charge of battery modules 21a to 21u

[0079] In some feasible embodiments, the above second battery parameter can also be replaced by the absolute value of the balancing time of the battery module. At this time, the fourth preset parameter value is a preset balancing time value. The above third battery parameter can also be replaced by the balancing time of the battery module. Among them, the balancing time t of the battery module can be determined by the following formula (2) and formula (3).

[0080] t = SOC4 / I, Formula (2)

[0081]

[0082] In formula (2), SOC4 is used to represent the equalization capacity of the battery module, and I is used to represent the rated current of the DC converter corresponding to the battery module. Exemplarily, the rated current can be 5.7A or 6.6A. In formula (3), 0.9 can also be replaced with other values, which can be specifically determined by the actual application scenario of the energy storage system 2 and are not limited herein.

[0083] In some feasible embodiments, when actively equalizing the battery modules 21a to 21u, the battery management system 23 is configured to select j battery modules from the battery modules 21a to 21u. Among them, the second battery parameters of the j battery modules are all greater than or equal to the fourth preset parameter value. The above j battery modules can be sorted from large to small or from small to large according to the third battery parameter. Further, the battery management system 23 is further configured to pair the kth battery module among the j battery modules with the (j + 1 - k)th battery module to obtain s pairs of battery modules. Implementing the embodiments of the present application can pair the j battery modules to be equalized in pairs according to the magnitude of the third battery parameter, so as to ensure that the s pairs of battery modules after pairing always operate at full power during the charge and discharge process, thereby improving the active equalization efficiency of the battery modules 21a to 21u.

[0084] In some feasible embodiments, for each pair of battery modules, the DC converter corresponding to the third battery module is configured to perform voltage conversion on the voltage output by the third battery module and supply power to the DC bus 22. The DC converter corresponding to the fourth battery module is configured to perform voltage conversion on the voltage output by the DC bus 22 and charge the fourth battery module. Implementing the embodiments of the present application does not require a control logic based on an equalization algorithm model during this active equalization process, reducing the control complexity of the DC converter, thereby reducing the maintenance cost of the energy storage system 2.

[0085] In some feasible embodiments, during the process of actively equalizing the battery modules 21a to 21u, when the output parameter of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, the battery management system 23 is configured to control the DC converter corresponding to any pair of battery modules to stop charging and discharging. The output parameter includes the output voltage or output current of the DC converter. Implementing the embodiments of the present application can isolate the faulty DC converter to prevent the fault from spreading to other normally operating DC converters, thereby reducing the potential risk and scheduling strategy complexity brought by the fault. In addition, it can also prevent all the DC converters corresponding to the s pairs of battery modules from stopping charging and discharging, thereby reducing the impact on the active equalization efficiency of the battery modules 21a to 21u.

[0086] In some feasible embodiments, during the fault recovery of the DC converters corresponding to any pair of battery modules, the output parameters of the DC converters corresponding to any pair of battery modules will gradually decrease to be less than the second preset parameter value, that is, the fault recovery of the DC converters corresponding to any pair of battery modules. At this time, the battery management system 23 is further configured to control the DC converters corresponding to any pair of battery modules to resume charging and discharging, so as to avoid affecting the active balancing efficiency of the battery modules 21a to 21u.

[0087] In some feasible embodiments, during the charging and discharging process of the DC converters corresponding to each pair of battery modules, when the output voltage of the DC converter corresponding to any pair of battery modules is less than or equal to the preset voltage value, that is, when the DC converter corresponding to any pair of battery modules has an undervoltage fault, the battery management system 23 is configured to control the DC converter corresponding to any pair of battery modules to stop charging and discharging. During the fault recovery process of the DC converters corresponding to any pair of battery modules, the output voltage of the DC converters corresponding to any pair of battery modules will gradually increase to be greater than the preset voltage value. At this time, the battery management system 23 is further configured to control the DC converters corresponding to any pair of battery modules to resume charging and discharging. Implementing the embodiments of the present application can avoid all the DC converters corresponding to s pairs of battery modules from stopping charging and discharging, thereby reducing the impact on the active balancing efficiency of the battery modules 21a to 21u. In addition, when the undervoltage fault of the DC converter corresponding to any pair of battery modules is recovered, the DC converter corresponding to any pair of battery modules can be re-controlled to resume charging and discharging, so as to avoid affecting the active balancing efficiency of the battery modules 21a to 21u.

[0088] In some feasible embodiments, during the active balancing process of the battery modules 21a to 21u, when the number of times that the DC converters corresponding to any pair of battery modules stop charging and discharging is greater than or equal to the third preset parameter value within the first time period, the battery management system 23 is configured to control the DC converters corresponding to s pairs of battery modules to stop charging and discharging. Implementing the embodiments of the present application can avoid the non-recoverable faults occurring in the DC converters from spreading to other normally operating DC converters, thereby improving the use safety and service life of the DC converters corresponding to s pairs of battery modules.

[0089] In some feasible embodiments, after the third battery module in each pair of battery modules charges the fourth battery module through the DC bus for the second time period, the battery management system 23 is configured to control the DC converters corresponding to s pairs of battery modules to stop charging and discharging. Implementing the embodiments of the present application can avoid the charging and discharging time of the DC converters corresponding to each pair of battery modules from being too long, resulting in an increase in the capacity difference between the battery modules, thereby improving the active balancing efficiency of the battery modules 21a to 21u by restricting the active balancing time period of the DC converters.

[0090] It can be understood that for the specific operations and beneficial effects of the battery management system 23 to perform active balancing on s pairs of battery modules, reference can be made to the above Figures 2 to 6 description in the corresponding embodiment regarding the battery management system 23 performing active balancing on n pairs of battery modules, which will not be elaborated here.

[0091] In some feasible embodiments, the above battery modules 21a to 21u, the DC bus 22, and the battery management system 23 can form a battery cluster in the energy storage system 2, and the energy storage system 2 can also include multiple battery clusters. Among them, the battery management system 23 is also used to perform active balancing on multiple battery modules in each battery cluster. For the specific process, reference can be made to the above Figures 2 to 6 description in the corresponding embodiment regarding performing active balancing on the battery modules 21a to 21u, which will not be elaborated here. It can be understood that each battery cluster can independently use a DC bus, or multiple battery clusters share the same DC bus. And each battery cluster can independently use a battery management system, or multiple battery clusters share the same battery management system.

[0092] See Figure 7 , Figure 7 is a schematic flowchart of an active balancing method for an energy storage system provided by an embodiment of the present application. This active balancing method is usually executed by the battery management system in the energy storage system, and specifically can be as Figure 7 shown, and this active balancing method includes the following steps S101 to S106.

[0093] Step S101, the battery management system pairs n pairs of battery modules from multiple battery modules.

[0094] In step S101, the energy storage system includes multiple battery modules, a DC bus, and a battery management system, and each battery module among the multiple battery modules is connected to the DC bus. The first battery parameters of the above n pairs of battery modules are all greater than or equal to the first preset parameter value. Each pair of battery modules among the above n pairs of battery modules includes a first battery module and a second battery module, and the voltage of the first battery module is greater than that of the second battery module. The above first battery parameter can be the absolute value of the difference between the maximum voltage value and the minimum voltage value of the battery module.

[0095] In specific implementation, the battery management system selects m battery modules from multiple battery modules. Among them, the first battery parameters of the m battery modules are all greater than or equal to the first preset parameter value. The above m battery modules can be sorted in descending order or ascending order according to the voltage of the battery modules. Further, the battery management system pairs the i-th battery module among the m battery modules with the (m + 1 - i)-th battery module to obtain n pairs of battery modules.

[0096] In step S102, the battery management system controls the first battery module in each pair of battery modules to charge the second battery module through the DC bus.

[0097] In specific implementation, for each pair of battery modules, the battery management system controls the DC converter corresponding to the first battery module to convert the voltage output by the first battery module and supply power to the DC bus, and controls the DC converter corresponding to the second battery module to convert the voltage output by the DC bus and charge the second battery module. Among them, the energy storage system further includes a plurality of DC converters, and the plurality of DC converters correspond to the plurality of battery modules one by one, and each battery module is connected to the DC bus through the corresponding DC converter.

[0098] In step S103, when the output parameter of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, the battery management system controls the DC converter corresponding to any pair of battery modules to stop charging and discharging.

[0099] In step S103, the output parameter includes the output voltage or output current of the DC converter.

[0100] In step S104, when the output parameter of the DC converter corresponding to any pair of battery modules is less than the second preset parameter value, the battery management system controls the DC converter corresponding to any pair of battery modules to resume charging and discharging.

[0101] In step S105, within the first time period, when the number of times that the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to the third preset parameter value, the battery management system controls the DC converters corresponding to n pairs of battery modules to stop charging and discharging.

[0102] In step S106, after the first battery module in each pair of battery modules charges the second battery module through the DC bus for the second time period, the battery management system controls the DC converters corresponding to n pairs of battery modules to stop charging and discharging.

[0103] In specific implementation, for the active balancing method of the energy storage system provided in this application, more operations performed by the battery management system and their corresponding beneficial effects can be seen in the above Figures 2 to 6 shown implementation manner of the battery management system 23 and its corresponding beneficial effects in the energy storage system 2 and its working principle, which will not be elaborated here.

[0104] See Figure 8 , Figure 8 is another flow schematic diagram of the active balancing method of the energy storage system provided by the embodiment of the present application. This active balancing method is usually executed by the battery management system in the energy storage system, and specifically can be as Figure 8As shown, the active balancing method includes the following steps S201 to S206.

[0105] Step S201: The battery management system pairs s pairs of battery modules from multiple battery modules.

[0106] In step S201, the energy storage system includes multiple battery modules, a DC bus, and a battery management system. Each battery module in the multiple battery modules is connected to the DC bus. The second battery parameter of the above s pairs of battery modules is greater than or equal to the fourth preset parameter value. Each pair of battery modules in the above s pairs of battery modules includes a third battery module and a fourth battery module, and the third battery parameter of the third battery module is greater than the third battery parameter of the third battery module. The second battery parameter is the absolute value of the difference between the state of charge of the battery module and the average state of charge of the multiple battery modules, and the third battery parameter is the difference between the state of charge of the battery module and the average state of charge.

[0107] In specific implementation, when actively balancing multiple battery modules, the battery management system selects j battery modules from the multiple battery modules. Among them, the second battery parameter of the j battery modules is greater than or equal to the fourth preset parameter value. The above j battery modules can be sorted from large to small or from small to large according to the third battery parameter. Further, the battery management system is also used to pair the kth battery module and the (j + 1 - k)th battery module among the j battery modules to obtain s pairs of battery modules.

[0108] Step S202: The battery management system controls the third battery module in each pair of battery modules to charge the fourth battery module through the DC bus.

[0109] In specific implementation, for each pair of battery modules, the battery management system controls the DC converter corresponding to the third battery module to convert the voltage output by the third battery module and supply power to the DC bus, and controls the DC converter corresponding to the fourth battery module to convert the voltage output by the DC bus and charge the fourth battery module. Among them, the energy storage system also includes multiple DC converters, and the multiple DC converters correspond to the multiple battery modules one by one. Each battery module is connected to the DC bus through the corresponding DC converter.

[0110] Step S203: When the output parameter of the DC converter corresponding to any pair of battery modules is greater than or equal to the second preset parameter value, the battery management system controls the DC converter corresponding to any pair of battery modules to stop charging and discharging.

[0111] In step S203, the output parameter includes the output voltage or output current of the DC converter.

[0112] Step S204: When the output parameters of the DC converter corresponding to any pair of battery modules are less than the second preset parameter value, the battery management system controls the DC converter corresponding to any pair of battery modules to resume charging and discharging.

[0113] Step S205: When the number of times that the DC converter corresponding to any pair of battery modules stops charging and discharging is greater than or equal to the third preset parameter value within the first time period, the battery management system controls the DC converters corresponding to s pairs of battery modules to stop charging and discharging.

[0114] Step S206: After the third battery module in each pair of battery modules charges the fourth battery module through the DC bus for the second time period, the battery management system controls the DC converters corresponding to s pairs of battery modules to stop charging and discharging.

[0115] In specific implementation, for more operations performed by the battery management system and their corresponding beneficial effects in the active balancing method of the energy storage system provided in this application, reference can be made to the implementation manners and their corresponding beneficial effects performed by the battery management system 23 in the energy storage system 2 and its working principle shown above. Details are not described herein again. Figures 2 to 6 Shown in the energy storage system 2 and its working principle, the implementation manners and their corresponding beneficial effects performed by the battery management system 23 are not elaborated herein.

[0116] In the active balancing method of the energy storage system provided in this application, the active balancing efficiency of multiple battery modules can be improved, and the battery capacity difference between multiple battery modules can be reduced more quickly. In addition, during this active balancing process, there is no need to adopt a control logic based on an equalization algorithm model, which reduces the control complexity of multiple DC converters, thereby reducing the maintenance cost of the energy storage system.

[0117] The above are only specific implementation manners of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and all should be covered by the protection scope of this application. Therefore, the protection scope of this 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 plurality of battery modules, a DC bus, and a battery management system, and each of the battery modules is connected to the DC bus; The battery management system is configured to: Pair n pairs of battery modules from the plurality of battery modules; wherein, the first battery parameter of the n pairs of battery modules is greater than or equal to a first preset parameter value, each pair of the battery modules includes a first battery module and a second battery module, and the voltage of the first battery module is greater than the voltage of the second battery module; the first battery parameter is the absolute value of the difference between the maximum voltage value and the minimum voltage value of the battery module; Control the first battery module in each pair of the battery modules to charge the second battery module through the DC bus.

2. The energy storage system according to claim 1, characterized in that, The battery management system is configured to: Select m battery modules from the plurality of battery modules; wherein, the first battery parameter of the m battery modules is greater than or equal to the first preset parameter value, and the m battery modules are sorted from largest to smallest or from smallest to largest according to the voltage of the battery modules; Pair the i-th battery module and the (m + 1 - i)-th battery module among the m battery modules to obtain the n pairs of battery modules.

3. The energy storage system according to claim 1 or 2, characterized in that, The energy storage system further includes a plurality of DC converters, and the plurality of DC converters correspond to the plurality of battery modules one by one; wherein, each of the battery modules is connected to the DC bus through the corresponding DC converter; The DC converter corresponding to the first battery module is configured to convert the voltage output by the first battery module and supply power to the DC bus; The DC converter corresponding to the second battery module is configured to convert the voltage output by the DC bus and charge the second battery module.

4. The energy storage system according to claim 3, wherein When the output parameter of the DC converter corresponding to any pair of the battery modules is greater than or equal to a second preset parameter value, the battery management system is configured to control the DC converter corresponding to any pair of the battery modules to stop charging and discharging; wherein, the output parameter includes the output voltage or output current of the DC converter.

5. The energy storage system according to claim 4, wherein, When the output parameter of the DC converter corresponding to any pair of the battery modules is less than the second preset parameter value, the battery management system is configured to control the DC converter corresponding to any pair of the battery modules to resume charging and discharging.

6. The energy storage system according to claim 5, wherein When the number of times that the DC converter corresponding to any pair of the battery modules stops charging and discharging is greater than or equal to a third preset parameter value within a first time period, the battery management system is configured to control the DC converters corresponding to the n pairs of battery modules to stop charging and discharging.

7. The energy storage system according to any one of claims 3-5, characterized in that, After a second time period when the first battery module in each pair of the battery modules charges the second battery module through the DC bus, the battery management system is configured to control the DC converters corresponding to the n pairs of battery modules to stop charging and discharging.

8. An energy storage system, characterized in that, The energy storage system includes a plurality of battery modules, a DC bus, and a battery management system, and each of the battery modules is connected to the DC bus; The battery management system is configured to: Pair s pairs of battery modules from the multiple battery modules; wherein, the second battery parameters of the s pairs of battery modules are all greater than or equal to a fourth preset parameter value, each pair of the battery modules includes a third battery module and a fourth battery module, and the third battery parameter of the third battery module is greater than that of the fourth battery module; the second battery parameter is the absolute value of the difference between the state of charge of the battery module and the average value of the states of charge of the multiple battery modules, and the third battery parameter is the difference between the state of charge of the battery module and the average value of the states of charge. Control the third battery module in each pair of the battery modules to charge the fourth battery module through the DC bus.

9. The energy storage system according to claim 8, characterized in that, The battery management system is used for: Select j battery modules from the multiple battery modules; wherein, the second battery parameters of the j battery modules are all greater than or equal to the fourth preset parameter value, and the j battery modules are sorted from largest to smallest or from smallest to largest according to the third battery parameter. Pair the k-th battery module and the (j + 1 - k)-th battery module among the j battery modules to obtain the s pairs of battery modules.

10. The energy storage system according to claim 8 or 9, characterized in that, The energy storage system further includes a plurality of DC converters, and the plurality of DC converters correspond to the plurality of battery modules one by one; wherein, each battery module is connected to the DC bus through the corresponding DC converter. The DC converter corresponding to the third battery module is used for voltage conversion of the voltage output by the third battery module and supplying power to the DC bus. The DC converter corresponding to the fourth battery module is used for voltage conversion of the voltage output by the DC bus and charging the fourth battery module.

11. The energy storage system according to claim 10, wherein When the output parameter of the DC converter corresponding to any pair of the battery modules is greater than or equal to a second preset parameter value, the battery management system is used to control the DC converter corresponding to any pair of the battery modules to stop charging and discharging; wherein, the output parameter includes the output voltage or output current of the DC converter.

12. The energy storage system according to claim 11, wherein, When the output parameter of the DC converter corresponding to any pair of the battery modules is less than the second preset parameter value, the battery management system is used to control the DC converter corresponding to any pair of the battery modules to resume charging and discharging.

13. The energy storage system according to claim 11, wherein, When the number of times that the DC converter corresponding to any pair of the battery modules stops charging and discharging is greater than or equal to a third preset parameter value within a first time period, the battery management system is used to control the DC converters corresponding to the s pairs of battery modules to stop charging and discharging.

14. The energy storage system according to any one of claims 10-12, characterized in that, After a second time period when the third battery module in each pair of the battery modules charges the fourth battery module through the DC bus, the battery management system is used to control the DC converters corresponding to the s pairs of battery modules to stop charging and discharging.

15. An active balancing method for an energy storage system, characterized in that, The method includes: Pair n pairs of battery modules from multiple battery modules; wherein, the energy storage system includes multiple battery modules and a DC bus, and each of the battery modules is connected to the DC bus; the first battery parameters of the n pairs of battery modules are all greater than or equal to a first preset parameter value, each pair of the battery modules includes a first battery module and a second battery module, and the voltage of the first battery module is greater than the voltage of the second battery module; the first battery parameter is the absolute value of the difference between the maximum voltage value and the minimum voltage value of the battery module. Control the first battery module in each pair of the battery modules to charge the second battery module through the DC bus.

16. An active equalization method for an energy storage system, characterized in that, The method includes: Pair s pairs of battery modules from multiple battery modules; wherein, the second battery parameters of the s pairs of battery modules are all greater than or equal to a fourth preset parameter value, each pair of the battery modules includes a third battery module and a fourth battery module, and the third battery parameter of the third battery module is greater than the third battery parameter of the fourth battery module; the second battery parameter is the absolute value of the difference between the state of charge of the battery module and the average value of the states of charge of the multiple battery modules, and the third battery parameter is the difference between the state of charge of the battery module and the average value of the states of charge. Control the third battery module in each pair of the battery modules to charge the fourth battery module through the DC bus.

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