Energy balancing method, determination method of balancing coefficient, system and storage medium

Abstract

The application discloses an energy balancing method, a balancing coefficient determination method, a system and a storage medium, and is applied to the technical field of energy storage, and the method comprises the following steps: determining the current charging / discharging power of an energy storage subsystem according to the target power and the balancing coefficient of an energy storage system, and the battery capacity and the state of charge of the energy storage subsystem; determining the current total charging / discharging power of the energy storage system according to the current charging / discharging power of each energy storage subsystem; when the current total charging / discharging power is less than the lower limit value of the target power, determining the difference total charging / discharging power according to the total charging / discharging power of the charging / discharging limiting energy storage subsystem and the target power; and determining the target charging / discharging power of other energy storage subsystems in the energy storage system except the charging / discharging limiting energy storage subsystem according to the difference total charging / discharging power. The technical scheme of the application realizes the balancing of the battery energy of the energy storage system and improves the overall availability of the energy storage system.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to an energy balancing method, a method for determining the balancing coefficient, a system, and a storage medium. Background Technology

[0002] A large-capacity energy storage system can be composed of multiple small-capacity energy storage subsystems connected in parallel. Each energy storage subsystem includes an energy storage battery and an energy storage bidirectional converter. The DC side of each energy storage bidirectional converter is independently connected to the energy storage battery, and the AC side is connected in parallel to the AC bus W1.

[0003] Because the battery characteristics (internal resistance, efficiency, capacity, etc.) of the energy storage batteries in different energy storage subsystems vary, the change in battery capacity also differs after long-term operation. This results in the actual battery capacities of the energy storage batteries in each subsystem being different. Even when determining the battery energy of an energy storage subsystem using batteries of the same capacity in related technologies, the problem of battery capacity imbalance still exists. This imbalance leads to a decrease in the overall availability of the energy storage system. Summary of the Invention

[0004] This application provides an energy balancing method, a method for determining the balancing coefficient, a system, and a storage medium, aiming to solve the problem of reduced overall availability of the energy storage system due to uneven battery energy in the energy storage subsystem.

[0005] This application provides an energy balancing method for an energy storage system, applied to an energy storage system including at least two parallel-connected energy storage subsystems. The energy balancing method for the energy storage system includes:

[0006] Based on the target power and equalization coefficient of the energy storage system, as well as the battery capacity and state of charge of the energy storage subsystem, the current charging / discharging power of the energy storage subsystem is determined.

[0007] The current total charging / discharging power of the energy storage system is determined based on the current charging / discharging power of each of the energy storage subsystems.

[0008] When the current total charging / discharging power is less than the target power lower limit, the difference in total charging / discharging power is determined based on the total charging / discharging power corresponding to the charging / discharging limit energy storage subsystem and the target power.

[0009] The target charge / discharge power of other energy storage subsystems in the energy storage system, other than the charge / discharge limit energy storage subsystem, is determined based on the differential total charge / discharge power.

[0010] Optionally, the step of determining the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, and the battery capacity and state of charge of the energy storage subsystem includes:

[0011] The average state of charge of all energy storage subsystems is determined based on the battery capacity and state of charge of each energy storage subsystem.

[0012] The current charge / discharge power of each energy storage subsystem is determined based on the target power and equalization coefficient of the energy storage system, the battery capacity and state of charge of each energy storage subsystem, the number of energy storage subsystems, and the average state of charge of the batteries.

[0013] Optionally, the step of determining the current charge / discharge power of each energy storage subsystem based on the target power and equalization coefficient corresponding to the energy storage system, the battery capacity and state of charge of each energy storage subsystem, the number of energy storage subsystems, and the average state of charge of the batteries includes:

[0014] Determine the ratio of the battery capacity corresponding to each energy storage subsystem to the total battery capacity of the energy storage system, and determine the difference between the battery state of charge corresponding to each energy storage subsystem and the average battery state of charge.

[0015] Determine the first product between the balance coefficient, the proportion, the number of energy storage subsystems, and the difference, and determine the second product between the proportion and the target power;

[0016] The current charge / discharge power of each energy storage subsystem is determined based on the difference between the second product and the first product.

[0017] Optionally, the step of determining the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, and the battery capacity and state of charge of the energy storage subsystem, includes:

[0018] Obtain the operating status of the energy storage system;

[0019] When the operating state is charging state, the current charging power of each energy storage subsystem is determined based on the target power corresponding to the energy storage system, the equalization coefficient, and the battery capacity and state of charge corresponding to the energy storage subsystem; or,

[0020] When the operating state is the discharge state, the current discharge power of each energy storage subsystem is determined based on the target power corresponding to the energy storage system, the equalization coefficient, the battery capacity corresponding to the energy storage subsystem, and the battery state of charge.

[0021] Optionally, the step of determining the difference in total charging / discharging power based on the total charging / discharging power corresponding to the charging / discharging limit energy storage subsystem and the target power when the current total charging / discharging power is less than the target power lower limit includes:

[0022] When the current total charging / discharging power is less than the target power lower limit, the energy storage subsystem with the current discharge power greater than or equal to the maximum discharge power or the current charging power less than or equal to the maximum charge power is identified as the charging / discharging limited energy storage subsystem.

[0023] The difference between the target power and the total charge / discharge power corresponding to all the charge / discharge limited energy storage subsystems is determined as the differential total charge / discharge power.

[0024] Optionally, the step of determining the target charge / discharge power of other energy storage subsystems besides the charge / discharge limiting energy storage subsystem in the energy storage system based on the differential total charge / discharge power includes:

[0025] Obtain the battery capacity and state of charge of other energy storage subsystems;

[0026] The target charge / discharge power of the other energy storage subsystems is determined based on the differential total charge / discharge power and equalization coefficient of the other energy storage subsystems, as well as the battery capacity and state of charge of the corresponding other energy storage subsystems.

[0027] Optionally, the step of determining the current total charging / discharging power of the energy storage system based on the current charging / discharging power of each of the energy storage subsystems includes:

[0028] The current total charge / discharge power of the energy storage system is determined based on the weighted value of the current charge / discharge power of each of the energy storage subsystems.

[0029] Optionally, after the step of determining the current total charging / discharging power of the energy storage system based on the current charging / discharging power of each of the energy storage subsystems, the method further includes:

[0030] When the current total charge / discharge power is greater than or equal to the target power lower limit, each energy storage subsystem is controlled to operate at the corresponding current charge / discharge power.

[0031] Based on the same inventive concept, the present invention also provides a method for determining the equilibrium coefficient, the method comprising:

[0032] Select the maximum equilibrium difference from the difference between the battery state of charge and the average battery state of charge for each energy storage subsystem;

[0033] When the maximum difference in equilibrium exceeds the equilibrium threshold, the equilibrium coefficient is determined based on the objective function;

[0034] When the maximum difference in the equilibrium is less than or equal to the equilibrium threshold, the preset equilibrium coefficient is determined as the equilibrium coefficient.

[0035] Optionally, the step of determining the equilibrium coefficient based on the objective function when the maximum equilibrium difference is greater than the equilibrium threshold includes:

[0036] When the maximum difference in the equilibrium is greater than the equilibrium threshold, the average charge / discharge power of all energy storage subsystems is determined based on the target power of the energy storage system and the number of energy storage subsystems.

[0037] Select the largest variance from the variances corresponding to the current charge / discharge power and the average charge / discharge power of each of the energy storage subsystems;

[0038] The equilibrium coefficient is determined based on the variance.

[0039] Furthermore, to achieve the above objectives, the present invention also provides an energy storage system comprising: at least two parallel-connected energy storage subsystems, each of the energy storage subsystems comprising a series-connected energy storage battery and an energy storage bidirectional converter; the energy storage system further comprising an energy balancing device, wherein the energy balancing device is communicatively connected to each of the energy storage subsystems, the energy balancing device comprising: a memory, a processor, and an energy balancing program or a balancing coefficient determination program stored in the memory and executable on the processor, wherein when the energy balancing program is executed by the processor, it implements the steps of the energy balancing method of the energy storage system described above, or the balancing coefficient determination program is configured to implement the steps of the balancing coefficient determination method described above.

[0040] In addition, to achieve the above objectives, the present invention also provides a computer-readable storage medium storing an energy balancing program or a program for determining the balancing coefficient of an energy storage system. When the energy balancing program of the energy storage system is executed by a processor, it implements the steps of the energy balancing method of the energy storage system described above, or when the program for determining the balancing coefficient is executed by a processor, it implements the steps of the method for determining the balancing coefficient described above.

[0041] The energy balancing method, balancing coefficient determination method, system, and storage medium provided in this application embodiment employ a technical solution that determines the current charging / discharging power of each energy storage subsystem based on the target power and balancing coefficient of the energy storage system, as well as the battery capacity and state of charge of the corresponding energy storage subsystem. Then, based on the current charging / discharging power of each energy storage subsystem, the current total charging / discharging power of the entire energy storage system is determined. When the current total charging / discharging power is less than the target power lower limit, a differential total charging / discharging power is determined based on the total charging / discharging power of the energy storage subsystem with charging / discharging limitations and the target power. Finally, based on this differential total charging / discharging power, the target charging / discharging power of other energy storage subsystems outside the energy storage subsystem with charging / discharging limitations is determined. This technical solution ensures that when battery energy is unbalanced, i.e., when the current total charging / discharging power is less than the target power lower limit, the differential total charging / discharging power is allocated to other energy storage subsystems outside the energy storage subsystem with charging / discharging limitations, enabling the energy storage system to operate normally and improving the overall availability of the energy storage system. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the energy storage system involved in the embodiments of the present invention;

[0043] Figure 2 This is a schematic diagram of the energy balancing device of the energy storage system involved in the embodiment of the present invention;

[0044] Figure 3 This is a flowchart illustrating the first embodiment of the energy balancing method for the energy storage system of the present invention;

[0045] Figure 4 This is a flowchart illustrating the third embodiment of the energy storage system of the present invention.

[0046] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. The accompanying drawings are only one embodiment and not the entirety of the invention. Detailed Implementation

[0047] To address the problem of reduced overall availability of energy storage systems due to energy imbalance among battery subsystems, this application proposes an energy balancing method for energy storage systems. This method determines the current charge / discharge power of each energy storage subsystem based on its target power and balancing coefficient, as well as the battery capacity and state of charge of each subsystem. Then, it determines the total current charge / discharge power of the entire energy storage system based on the current charge / discharge power of each subsystem. When the total current charge / discharge power is less than the target power lower limit, it determines the differential charge / discharge power based on the total charge / discharge power of the energy storage subsystem with charge / discharge limitations and the target power. Finally, it determines the target charge / discharge power of other energy storage subsystems outside the energy storage subsystem with charge / discharge limitations based on this differential charge / discharge power. Because the differential charge / discharge power is allocated to other energy storage subsystems outside the energy storage subsystem with charge / discharge limitations when battery energy is unbalanced (i.e., when the current total charge / discharge power is less than the target power lower limit), the energy storage system can operate normally, improving its overall availability.

[0048] To better understand the above technical solutions, exemplary embodiments of this disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0049] like Figure 1 As shown, Figure 1 This is a schematic diagram of the hardware operating environment involved in the embodiments of the present invention.

[0050] It should be noted that, Figure 1 This can be a structural diagram of the hardware operating environment of the energy storage system.

[0051] The energy storage system 2000 includes an energy storage subsystem connected in parallel to the same AC bus W1 and an energy balancing device 1000 for the energy storage system. The energy storage system 2000 consists of multiple energy storage subsystems connected in parallel. Each energy storage subsystem includes an energy storage battery and an energy storage bidirectional converter. The DC side of each energy storage bidirectional converter is independently connected to the energy storage battery, and the AC side is connected in parallel to the AC bus. The energy storage batteries in the energy storage subsystems can be individual cells, battery packs, or battery modules. The energy storage batteries included in different energy storage subsystems can be of different types, or have different power ratings and capacities.

[0052] Optionally, such as Figure 2As shown, the energy balancing device 1000 of the energy storage system may include: a processor 1001, such as a CPU; a memory 1005; a user interface 1003; a network interface 1004; and a communication bus 1002. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be a high-speed RAM or a stable, non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001.

[0053] like Figure 2 As shown, the memory 1005, which serves as a storage medium, may include an operating system, a network communication module, a user interface module, and an energy balancing program or a program for determining the balancing coefficient of the energy storage system. The operating system is a program that manages and controls the hardware and software resources of the energy balancing device of the energy storage system, the energy balancing program or the program for determining the balancing coefficient of the energy storage system, and the operation of other software or programs.

[0054] exist Figure 2 In the energy balancing device of the energy storage system shown, the user interface 1003 is mainly used to connect to the terminal and communicate data with the terminal; the network interface 1004 is mainly used to communicate data with the back-end server; the processor 1001 can be used to call the energy balancing program or the program for determining the balancing coefficient of the energy storage system stored in the memory 1005.

[0055] Those skilled in the art will understand that Figure 2 The energy balancing device structure of the energy storage system shown does not constitute a limitation on the energy balancing device of the energy storage system. It may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0056] The technical solution of this application will be specifically described below by way of embodiments.

[0057] First embodiment.

[0058] like Figure 2 As shown, in the first embodiment of this application, the energy balancing method of the energy storage system of this application includes the following steps:

[0059] Step S110: Determine the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, as well as the battery capacity and state of charge of the energy storage subsystem.

[0060] In this embodiment, due to differences in battery characteristics (internal resistance, efficiency, or capacity, etc.) among the energy storage subsystems, significant battery energy imbalances will occur after prolonged operation. The battery energy level of an energy storage subsystem can be directly reflected by parameters such as battery voltage and battery SOC (State of Charge). Therefore, when there is an energy imbalance among the energy storage subsystems, the battery voltage or SOC of the energy storage subsystem can be used as a balancing control variable to distribute the differential charging / discharging power to other energy storage subsystems outside the charging / discharging-limited subsystems. This gradually reduces the energy imbalance among the energy storage subsystems, enabling the energy storage system to operate normally and improving its overall availability.

[0061] In this embodiment, the target power is the rated power of the energy storage system. The balancing coefficient can be a default coefficient or it can be optimized and determined according to the actual situation during the battery energy balancing distribution process. The balancing coefficient can be determined according to different situations. Battery capacity is one of the important performance indicators for measuring battery performance. It represents the amount of electricity released by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.), usually measured in ampere-hours. Battery capacity is divided into actual capacity, theoretical capacity, and rated capacity according to different conditions. The battery capacity of each energy storage subsystem may change after operating for a period of time. Therefore, the battery capacity of the energy storage battery in each energy storage subsystem can be obtained in real time during the charging and discharging process. The battery state of charge (SOC) refers to the ratio of the remaining capacity of the energy storage battery after a period of use or long-term storage to its fully charged state of charge. The SOC of the energy storage battery in each energy storage subsystem can be obtained in real time during the charging and discharging process.

[0062] Optionally, the entire energy storage system requires the installation of load meters, PCC meters, and energy storage meters. The load meters are used to evaluate system indicators and measure the battery state of charge (SOC). One load meter can be connected to each energy storage subsystem to measure the SOC of the batteries in each subsystem. Before measurement, all load meters need to be synchronized to ensure consistent timekeeping and prevent measurement errors caused by time discrepancies.

[0063] Optionally, during the charging process of the energy storage system, after measuring the battery capacity and state of charge of each energy storage subsystem, and obtaining the target power and equalization coefficient of the energy storage system, the current charging power of each energy storage subsystem can be determined based on the target power, equalization coefficient, battery capacity of each energy storage subsystem, and state of charge of the energy storage batteries in each energy storage subsystem.

[0064] Optionally, during the discharge process of the energy storage system, after measuring the battery capacity and state of charge of each energy storage subsystem, and obtaining the target power and equalization coefficient of the energy storage system, the current discharge power of each energy storage subsystem can be determined based on the target power, equalization coefficient, battery capacity of each energy storage subsystem, and state of charge of the energy storage batteries in each energy storage subsystem.

[0065] Step S120: Determine the current total charging / discharging power of the energy storage system based on the current charging / discharging power of each of the energy storage subsystems.

[0066] In this embodiment, after determining the current charging / discharging power of each energy storage subsystem, the current total charging / discharging power of the energy storage system can be determined based on the current charging / discharging power. Here, the current total charging power is the actual total charging power of all energy storage subsystems in the current energy storage system, and the current total discharging power is the actual total discharging power of all energy storage subsystems in the current energy storage system. Optionally, the operating mode of the current energy storage system can be obtained. When the operating mode is charging mode, the current total charging power of the energy storage system can be determined based on the current charging power of each energy storage subsystem. Optionally, when the operating mode of the current energy storage system is discharging mode, the current total discharging power of the energy storage system can be determined based on the current discharging power of each energy storage subsystem.

[0067] Step S130: When the current total charging / discharging power is less than the target power lower limit, determine the difference in total charging / discharging power based on the total charging / discharging power corresponding to the charging / discharging limit energy storage subsystem and the target power.

[0068] Step S140: Determine the target charge / discharge power of other energy storage subsystems in the energy storage system other than the charge / discharge limiting energy storage subsystem based on the differential total charge / discharge power.

[0069] In this embodiment, the lower limit of the target power can be determined based on the power dead zone value. The charge / discharge limited energy storage subsystem can be determined by marking the limit boundary. The energy storage subsystem under charge / discharge limitation cannot charge / discharge.

[0070] Specifically, after determining the current total charge / discharge power, the energy balance of the energy storage system is checked. If the current total charge / discharge power is less than the target power lower limit, it indicates that the energy balance of the energy storage system is not achieved. At this point, it is necessary to identify the energy storage subsystems that have reached their charge / discharge limits and those that have not. Then, based on the total charge / discharge power of the subsystems that have reached their limits and the target power of the energy storage system, the difference in total charge / discharge power is determined. This difference in total charge / discharge power is then distributed to the other energy storage subsystems except for those with limited charge / discharge power, until the current total charge / discharge power gradually approaches the target power.

[0071] Optionally, after determining the current total charging power, it is checked whether the battery energy of the energy storage system has reached equilibrium. If the current total charging power is less than the first target power lower limit, it indicates that the battery energy of the current energy storage system has not reached equilibrium. At this time, it is necessary to identify the energy storage subsystems that have reached the charging limit and those that have not, and then determine the difference in total charging power based on the total charging power corresponding to the energy storage subsystems that have reached the charging limit and the target power of the energy storage system. The difference in total charging power is then distributed to other energy storage subsystems other than the energy storage subsystems with charging limits until the current total charging power gradually approaches the target power.

[0072] Optionally, after determining the current total discharge power, it is checked whether the battery energy of the energy storage system has reached equilibrium. If the current total discharge power is less than the second target power lower limit, it indicates that the battery energy of the current energy storage system has not reached equilibrium. This second target power lower limit can be the same as or different from the first target power lower limit, and can be set according to actual conditions. If the battery energy of the current energy storage system has not reached equilibrium, it is necessary to identify the energy storage subsystems that have reached their discharge limits and those that have not. Then, based on the total discharge power corresponding to the energy storage subsystems that have reached their discharge limits and the target power of the energy storage system, the differential total discharge power is determined. This differential total discharge power is then distributed to other energy storage subsystems besides those with discharge limits until the current total discharge power gradually approaches the target power.

[0073] This embodiment, based on the above technical solution, employs a method that determines the current charging / discharging power of each energy storage subsystem based on the target power and equalization coefficient of the energy storage system, as well as the battery capacity and state of charge of the corresponding energy storage subsystem. Then, it determines the current total charging / discharging power of the entire energy storage system based on the current charging / discharging power of each subsystem. When the current total charging / discharging power is less than the target power lower limit, it determines the differential total charging / discharging power based on the total charging / discharging power of the energy storage subsystem with charging / discharging limitations and the target power. Finally, it determines the target charging / discharging power of other energy storage subsystems outside the energy storage subsystem with charging / discharging limitations based on this differential total charging / discharging power. Because when battery energy is unbalanced, i.e., when the current total charging / discharging power is less than the target power lower limit, the differential total charging / discharging power is allocated to other energy storage subsystems outside the energy storage subsystem with charging / discharging limitations, the energy storage system can operate normally, improving the overall availability of the energy storage system.

[0074] Optionally, determining the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, as well as the battery capacity and state of charge of the energy storage subsystem, may specifically include the following steps:

[0075] Step S111: Determine the average battery state of charge of all energy storage subsystems based on the battery capacity and battery state of charge of each energy storage subsystem.

[0076] In this embodiment, the average state of charge of all energy storage subsystems can be determined using the following formula:

[0077]

[0078] Among them, C i Let SOCi be the battery capacity of the i-th energy storage subsystem, and SOCi be the battery state of charge of the i-th energy storage subsystem. When the battery capacity is used as the equalization control variable, it is the average battery state of charge of all energy storage subsystems. This average battery state of charge is the weighted average battery state of charge of all energy storage subsystems, and is defined as SOCavg.

[0079] Step S112: Determine the current charging / discharging power of each energy storage subsystem based on the target power and equalization coefficient of the energy storage system, the battery capacity and state of charge of each energy storage subsystem, the number of energy storage subsystems, and the average state of charge of the batteries.

[0080] In this embodiment, after determining the average state of charge of the battery, the current charging / discharging power of each energy storage subsystem can be further determined based on the average state of charge of the battery, combined with the target power and equalization coefficient of the energy storage system, the battery capacity and state of charge of each energy storage subsystem, and the number of energy storage subsystems.

[0081] Optionally, the ratio of the battery capacity corresponding to each of the energy storage subsystems to the total battery capacity of the energy storage system can be determined. And determine the difference between the battery state of charge (SOC) and the average SOC of each energy storage subsystem. i -SOC avg Determine the first product between the balance coefficient, the proportion, the number of energy storage subsystems, and the difference. And determine the second product between the percentage and the target power. The current charge / discharge power of each energy storage subsystem is determined based on the difference between the second product and the first product. Specifically, the current charge / discharge power of each energy storage subsystem can be determined according to the following formula:

[0082]

[0083] Among them, P t λ represents the target power of the energy storage system; λ represents the balance coefficient of the energy storage system; N is the number of current energy storage subsystems, which is essentially the number of energy storage subsystems that have not yet reached their charging limits. The current charging power or current discharging power of each energy storage subsystem can be calculated using the above formula.

[0084] After verification, without considering the charge / discharge limits for the time being, assuming a target power Pt = 100 kW, and assuming the battery capacity of the energy storage subsystem is C1 = 100, C2 = 300, SOC1 = 10%, SOC2 = 30%, λ = 100, and SOC... avg =100%*(100*10%+300*100) / 400=25%, if the equilibrium strategy in this paper is adopted:

[0085] P1=100*(100 / 400)-100*(10%-25%)*2*100 / 400=32.5;

[0086] P2=100*(300 / 400)-100*(30%-25%)*2*300 / 400=67.5;

[0087] At this point, we can see that P1 + P2 = Pt, which satisfies the basic requirements of the equilibrium strategy.

[0088] Based on the above technical solution, this application corrects and optimizes the calculation method of the current charging / discharging power of the energy storage subsystem by taking into account the different battery capacities of the energy storage batteries in each energy storage subsystem, thereby improving the accuracy of the current charging / discharging power of the energy storage subsystem.

[0089] Optionally, the aforementioned charging / discharging power includes charging power or discharging power. The step of determining the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient corresponding to the energy storage system, and the battery capacity and state of charge corresponding to the energy storage subsystem, includes:

[0090] Step S211: Obtain the operating status of the energy storage system;

[0091] Step S212: When the working state is the charging state, determine the current charging power of each energy storage subsystem according to the target power corresponding to the energy storage system and the equalization coefficient, as well as the battery capacity and battery state of charge corresponding to the energy storage subsystem.

[0092] Alternatively, in step S213, when the operating state is the discharge state, the current discharge power of each energy storage subsystem is determined based on the target power corresponding to the energy storage system and the equalization coefficient, as well as the battery capacity and battery state of charge corresponding to the energy storage subsystem.

[0093] In this embodiment, the operating state of the energy storage system is determined, which can be viewed using an energy storage meter. After determining the operating state of the energy storage system, if the operating state is charging, the current power of each energy storage subsystem can be determined based on the target power of the energy storage system, the balancing coefficient, the battery capacity of the energy storage subsystem, and the battery state of charge. This current power is the current charging power. Optionally, if the operating state of the energy storage system is determined to be discharging, the current power of each energy storage subsystem can be determined based on the target power of the energy storage system, the balancing coefficient, the battery capacity of the energy storage subsystem, and the battery state of charge. This current power is the current discharging power. Optionally, the operating state of the energy storage system can be set before obtaining the operating state, and the operating state of the energy storage system can also be adaptively switched according to actual conditions.

[0094] According to the above technical solution, this embodiment can set the working state of the energy storage system and determine the current charging power or current discharging power of each energy storage subsystem under different working states, so as to achieve the balance of battery energy of the energy storage system under different working states.

[0095] Optionally, after determining the current charging / discharging power of each energy storage subsystem, the current charging / discharging power of each energy storage subsystem can be summed, and the current total charging / discharging power of the energy storage system can be determined based on the weighted value of the current charging / discharging power of each energy storage subsystem. Specifically, the current charging power of each energy storage subsystem can be summed, and the current total charging power of the energy storage system can be determined based on the weighted value of the current charging power of each energy storage subsystem. Alternatively, the current discharging power of each energy storage subsystem can be summed, and the current total discharging power of the energy storage system can be determined based on the weighted value of the current discharging power of each energy storage subsystem.

[0096] Optionally, after determining the current total charge / discharge power of the energy storage system, it is further determined whether the battery energy of the energy storage system is balanced. Optionally, when the current total charge / discharge power is less than the target power lower limit, determining the difference in total charge / discharge power based on the total charge / discharge power corresponding to the charge / discharge limit energy storage subsystem and the target power specifically includes the following steps:

[0097] Step S131: When the current total charging / discharging power is less than the target power lower limit, the energy storage subsystem with the current discharge power greater than or equal to the maximum discharge power or the current charging power less than or equal to the maximum charge power is determined as the charging / discharging limited energy storage subsystem.

[0098] Step S132: The difference between the target power and the total charge / discharge power corresponding to all the charge / discharge limited energy storage subsystems is determined as the differential total charge / discharge power.

[0099] Optionally, the current total charge / discharge power can be compared with the target power of the energy storage system. If the current total charge / discharge power is less than the lower limit of the target power, the energy of the energy storage system is determined to be unbalanced. In this case, the battery state-of-charge (POC) balancing calculation needs to be performed again. Before performing the recalculation, it is necessary to identify which energy storage subsystems have reached their charge / discharge limits and which have not. Then, the balancing calculation is performed based on the energy storage subsystems that have reached their charge / discharge limits.

[0100] Optionally, it is necessary to determine whether the current charging / discharging power of each energy storage subsystem is within the charging / discharging limit range. If not, the energy storage subsystem that is not within the charging / discharging limit range is identified as an energy storage subsystem that has not reached the charging / discharging limit; if it is, the energy storage subsystem that is within the charging / discharging limit range is identified as an energy storage subsystem that has reached the charging / discharging limit.

[0101] Optionally, the limiting range includes the maximum discharge power and the maximum rechargeable power. When the current total charge / discharge power is less than the target power lower limit, the energy storage battery with a current discharge power greater than or equal to the maximum discharge power or a current charging power less than or equal to the maximum rechargeable power is identified as a charge / discharge limited energy storage subsystem. Specifically, when the current total discharge power is less than the target power lower limit, the energy storage subsystem with a current discharge power greater than or equal to the maximum discharge power is identified as a discharge limited energy storage subsystem; otherwise, it is identified as an energy storage subsystem that has not reached the discharge limit. Alternatively, when the current total charging power is less than the target power lower limit, the energy storage subsystem with a current charging power less than or equal to the maximum rechargeable power is identified as a charge limited energy storage subsystem; otherwise, it is identified as an energy storage subsystem that has not reached the charging limit.

[0102] Optionally, after determining the charge-limited or discharge-limited energy storage subsystems, the difference between the target power and the total charge / discharge power corresponding to all the charge / discharge-limited energy storage subsystems is determined as the differential total charge / discharge power. Specifically, first, the energy storage subsystems that have reached the charge limit or the discharge limit are marked, and the power M of these energy storage subsystems that have reached the charge limit or the discharge limit is recorded. The sum of these power values ​​is PSM (the total charge / discharge power corresponding to the charge / discharge-limited energy storage subsystems). The remaining energy storage subsystems that have not reached the charge limit or the discharge limit are counted as combination V. At this time, the differential total charge power or differential total discharge power is Pt = Pt - PSM.

[0103] According to the above technical solution, when the battery energy of the energy storage system is uneven, this application identifies the energy storage subsystem that has not reached the charging limit or the energy storage subsystem that has reached the discharging limit, and then performs balancing calculations based on the energy storage subsystem that has not reached the charging limit or the energy storage subsystem that has reached the discharging limit, thereby solving the balancing control problem caused by the inconsistent battery pack capacity and improving the overall availability of the energy storage system.

[0104] Optionally, determining the target charge / discharge power of other energy storage subsystems besides the charge / discharge limiting energy storage subsystem in the energy storage system based on the differential total charge / discharge power may specifically include the following steps:

[0105] Step S141: Obtain the battery capacity and battery state of charge of other energy storage subsystems.

[0106] Step S142: Determine the target charging / discharging power of the other energy storage subsystems based on the differential total charging / discharging power and equalization coefficient of the other energy storage subsystems, as well as the battery capacity and battery state of charge of the other energy storage subsystems.

[0107] In this embodiment, after determining the differential total charge / discharge power, a rebalancing calculation is performed based on the energy storage subsystems that have not reached their charging limits or have reached their discharging limits. These energy storage subsystems are those other than those that have reached their charging / discharging limits. Specifically, the battery capacity and state of charge of the other energy storage subsystems can be obtained, and the target charging power or target discharging power of the other energy storage subsystems is calculated again based on the following formula:

[0108]

[0109] Among them, the other energy storage subsystems can be regarded as a "whole", P t λ represents the differential total charging / discharging power of the "whole"; λ represents the balancing coefficient of the "whole"; N is the number of energy storage subsystems in the current "whole", which is essentially the number of energy storage subsystems that have not yet reached their charging limits. The target charging power or target discharging power of each energy storage subsystem in the "whole" can be calculated using the above formula.

[0110] Based on the above technical solution, this application addresses the issue of uneven battery capacity caused by limiting the target charging / discharging power of other energy storage subsystems outside the energy storage subsystem when the battery energy in the energy storage system is uneven, thereby improving the overall availability of the energy storage system.

[0111] Optionally, the energy balancing method for the energy storage system of this application may further include the following steps:

[0112] Step S110: Determine the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, as well as the battery capacity and state of charge of the energy storage subsystem.

[0113] Step S120: Determine the current total charging / discharging power of the energy storage system based on the current charging / discharging power of each of the energy storage subsystems;

[0114] Step S150: When the current total charging / discharging power is greater than or equal to the target power lower limit, control each energy storage subsystem to operate at the corresponding current charging / discharging power.

[0115] In this embodiment, when the current total charging / discharging power of the energy storage system is greater than or equal to the target power lower limit, it indicates that the battery energy in the current energy storage system is balanced. Each energy storage subsystem can be controlled to operate at the corresponding current charging power or current discharging power, thereby enabling the energy storage system to operate normally.

[0116] Second embodiment.

[0117] Based on the same inventive concept, the present application also proposes a method for determining the balance coefficient. In the second embodiment of the present application, the method for determining the balance coefficient of the present application may include the following steps:

[0118] Step S310: Select the maximum balance difference from the differences between the state of charge of each energy storage subsystem and the average value of the state of charge of the batteries.

[0119] Step S320: When the maximum balance difference is greater than the balance threshold, determine the balance coefficient based on the objective function.

[0120] Step S330: When the maximum balance difference is less than or equal to the balance threshold, determine the preset balance coefficient as the balance coefficient.

[0121] In this embodiment, the balance threshold can be set according to the actual situation. During the process of achieving battery energy balance, the battery energy balance is also affected by the continuous charge / discharge time. Even if λ is set very small, if the continuous discharge time or charge time is long enough, balance can be achieved; if λ is set large enough, due to the limitation of Pdis_charge_max < Pi < PPcharge_max (indicating that the current discharge power is less than the maximum dischargeable power or the current charge power is greater than the maximum chargeable power. Here, Pdis_charge_max is the maximum dischargeable power, and PPcharge_max is the maximum chargeable power), the difference between ∑Pi and Pt will be too large, resulting in a large deviation from the control expectation; the charge / discharge time of energy storage is limited, so it is necessary to achieve the balance effect as quickly as possible, but this will also affect the control effect if it is too fast, which is not worth it; therefore, it is necessary to reasonably set the value of λ according to the actual situation, and whether λ is set appropriately directly affects the control target and the balance effect.

[0122] Optionally, after determining the current total charge / discharge power of the current energy storage system, the present application calculates in real time the magnitude relationship between the state of charge of each energy storage subsystem and the average value of the state of charge of all energy storage subsystems, and determines the value of λ based on this magnitude relationship.

[0123] Specifically, during the operation of each energy storage subsystem, the state of charge of the battery corresponding to each energy storage subsystem is obtained in real time, and the balance difference between the state of charge of the battery corresponding to each energy storage subsystem and the average value of the state of charge of the batteries of all energy storage subsystems is determined. The maximum balance difference is selected from all the balance differences, that is, the maximum balance difference. The maximum balance difference is compared with the balance threshold. When the maximum balance difference is less than or equal to the balance threshold, it indicates that the battery energy of the energy storage system is relatively balanced at this time, and the default preset balance coefficient and balance formula are directly used to calculate the current charge / discharge power of each energy storage subsystem. When the maximum balance difference is greater than the balance threshold, it indicates that the battery energy of each energy storage subsystem of the energy storage system varies greatly at this time, and it is necessary to optimize and determine the balance coefficient, and then calculate the current charge / discharge power of each energy storage subsystem based on the optimized balance coefficient and the above balance formula.

[0124] Optionally, during the optimization of the balance coefficient, in fact, it is to find the optimal solution of the objective function. Therefore, this application proposes a method for quickly iteratively calculating λ; λ can be regarded as the solution of an equation H(P). The above is the solution scheme:

[0125] 2.1) Core idea. When the variance S 2 is maximized in the sequence P = [P1, P2, P3... Pn], it indicates that the discretization program is the largest, and the balance speed is the fastest at this time. We use this idea to find the value of λ, then;

[0126] 2.2) Objective function modeling. H(P) takes the maximum variance of P = [P1, P2, P3... Pn] as the objective function to obtain the current charge / discharge power Pi of each energy storage subsystem:

[0127]

[0128] Among them, is the average charge / discharge power of all energy storage subsystems. P t is the target power of the energy storage system, N is the number of energy storage subsystems in the energy storage system. The limit interval of Pi is Pdis_charge_max < Pi < Ppcharge_max. It can be solved by substituting parameters. There are many mathematical methods for solving (quadratic function solving), which are not introduced in this article. Taking the maximum value of H(P) as the goal, the current value of λ is obtained. After obtaining the value of λ, the charge / discharge power P = [P1, P2... Pn] of all energy storage subsystems in the energy storage system is calculated based on this value of λ and the above balance formula. After determining the current charge / discharge power of all energy storage subsystems, P1, P2... Pn powers are sent to the energy storage subsystems by the controller respectively.

[0129] According to the above technical solution, this application achieves a rapid balancing effect by determining the balancing coefficient through an objective function when the maximum balancing difference is greater than the balancing threshold.

[0130] Third embodiment.

[0131] Reference Figure 4 Based on the first and second embodiments, the third embodiment of this application includes:

[0132] 1. Real-time calculation and acquisition of the battery state of charge (SOCi), battery capacity (Ci), maximum rechargeable power (Ppcharge_max), maximum dischargeable power (Pdischarge_max), and target power (Pt) issued by the scheduling module for each energy storage subsystem;

[0133] 2. Calculate the average state of charge (SOCavg) of all energy storage subsystems in the current energy storage subsystem;

[0134] 3. Calculate the maximum deviation of SOC in real time, the maximum difference of equilibrium SOCd = MAX(SOCi - SOCavg). If SOCd ≤ equilibrium threshold d, proceed to 4; otherwise, proceed to 5.

[0135] 4. Using the default balance coefficient λ, solve the balance formula to obtain the power Pi of each energy storage subsystem. After passing the safety boundary limit, output Pi and proceed to step 7.

[0136] Safety boundary limits:

[0137] 4.1 When the energy storage is being charged (power > 0), Pi = MIN(Pi, Ppcharge_max);

[0138] 4.2 When the stored energy is discharged (power < 0), Pi = MAX(Pi, Pdis_charge_max);

[0139] 5. Based on the objective function, the equilibrium system λ with the maximum dispersion is obtained through the iterative process of the coefficient λ value or other methods. Then, λ is substituted into the equilibrium formula to obtain the power Pi allocated to each energy storage subsystem. After the safety boundary constraint, Pi is output and proceed to step 6.

[0140] Safety boundary limits:

[0141] 5.1 When the energy storage is being charged (power > 0), Pi = MIN(Pi, Ppcharge_max);

[0142] 5.2 When the stored energy is discharged (power < 0), Pi = MAX(Pi, Pdis_charge_max);

[0143] Among them, Pdis_charge_max <Pi<PPcharge_max。

[0144] 6. First, determine whether the current total charging / discharging power SUM(Pi) of the energy storage system is within the target power Pt±k, where k is the power dead zone value. If it is not within the range, proceed to 7; otherwise, proceed to 8.

[0145] 7. First, mark the M energy storage subsystems that have reached the charge and discharge limit. Record the M power P that these energy storage subsystems have already output and sum them up to PSM. Then, the remaining energy storage subsystems that have not reached the limit are counted as the combination V. At this time, the target power is Pt = Pt - PSM. Proceed to step 2.

[0146] 8. At this point, all N energy storage subsystems have been calculated, and Pi is distributed to each energy storage subsystem.

[0147] Based on the above technical solution, this application not only achieves equalization control but also improves the equalization speed.

[0148] This invention provides an embodiment of an energy balancing method for an energy storage system. It should be noted that although the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0149] Based on the same inventive concept, this application also provides a computer-readable storage medium storing an energy balancing program or a program for determining the balancing coefficient of an energy storage system. When the energy balancing program of the energy storage system is executed by a processor, it implements the various steps of the energy balancing method of the energy storage system as described above. Or, when the program for determining the balancing coefficient is executed by a processor, it implements the various steps of the method for determining the balancing coefficient as described above, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0150] Since the storage medium provided in this application embodiment is the storage medium used to implement the method of this application embodiment, those skilled in the art can understand the specific structure and variations of the storage medium based on the method described in this application embodiment, and therefore will not be repeated here. All storage media used in the method of this application embodiment are within the scope of protection of this application.

[0151] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0152] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0153] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0154] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0155] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0156] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0157] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An energy balancing method for an energy storage system, characterized in that, Applied to an energy storage system, the energy storage system comprising at least two parallel-connected energy storage subsystems, the energy balancing method of the energy storage system includes: Based on the target power and equalization coefficient of the energy storage system, as well as the battery capacity and state of charge of the energy storage subsystem, the current charging / discharging power of the energy storage subsystem is determined. The current total charging / discharging power of the energy storage system is determined based on the current charging / discharging power of each of the energy storage subsystems. When the current total charge / discharge power is less than the target power lower limit, the energy storage subsystem with the current discharge power greater than or equal to the maximum discharge power or the current charge power less than or equal to the maximum charge power is identified as a charge / discharge limited energy storage subsystem; the differential total charge / discharge power is determined based on the total charge / discharge power corresponding to the charge / discharge limited energy storage subsystem and the target power. The target charge / discharge power of other energy storage subsystems in the energy storage system, other than the charge / discharge limit energy storage subsystem, is determined based on the differential total charge / discharge power.

2. The method as described in claim 1, characterized in that, The step of determining the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, and the battery capacity and state of charge of the energy storage subsystem includes: The average state of charge of all energy storage subsystems is determined based on the battery capacity and state of charge of each energy storage subsystem. The current charge / discharge power of each energy storage subsystem is determined based on the target power and equalization coefficient of the energy storage system, the battery capacity and state of charge of each energy storage subsystem, the number of energy storage subsystems, and the average state of charge of the batteries.

3. The method as described in claim 2, characterized in that, The step of determining the current charge / discharge power of each energy storage subsystem based on the target power and equalization coefficient of the energy storage system, the battery capacity and state of charge of each energy storage subsystem, the number of energy storage subsystems, and the average state of charge of the batteries includes: Determine the ratio of the battery capacity corresponding to each energy storage subsystem to the total battery capacity of the energy storage system, and determine the difference between the battery state of charge corresponding to each energy storage subsystem and the average battery state of charge. Determine the first product between the balance coefficient, the proportion, the number of energy storage subsystems, and the difference, and determine the second product between the proportion and the target power; The current charge / discharge power of each energy storage subsystem is determined based on the difference between the second product and the first product.

4. The method as described in claim 1, characterized in that, The step of determining the current charging / discharging power of the energy storage subsystem based on the target power and equalization coefficient of the energy storage system, and the battery capacity and state of charge of the energy storage subsystem, includes: Obtain the operating status of the energy storage system; When the operating state is charging state, the current charging power of each energy storage subsystem is determined based on the target power corresponding to the energy storage system, the equalization coefficient, and the battery capacity and state of charge corresponding to the energy storage subsystem; or, When the operating state is the discharge state, the current discharge power of each energy storage subsystem is determined based on the target power corresponding to the energy storage system, the equalization coefficient, the battery capacity corresponding to the energy storage subsystem, and the battery state of charge.

5. The method as described in claim 4, characterized in that, The step of determining the differential total charge / discharge power based on the total charge / discharge power corresponding to the charge / discharge limited energy storage subsystem and the target power includes: The difference between the target power and the total charge / discharge power corresponding to all the charge / discharge limited energy storage subsystems is determined as the differential total charge / discharge power.

6. The method as described in claim 1, characterized in that, The step of determining the target charge / discharge power of other energy storage subsystems in the energy storage system other than the charge / discharge limiting subsystem based on the differential total charge / discharge power includes: Obtain the battery capacity and state of charge of other energy storage subsystems; The target charge / discharge power of the other energy storage subsystems is determined based on the differential total charge / discharge power and equalization coefficient of the other energy storage subsystems, as well as the battery capacity and state of charge of the corresponding other energy storage subsystems.

7. The method as described in claim 1, characterized in that, The step of determining the current total charging / discharging power of the energy storage system based on the current charging / discharging power of each of the energy storage subsystems includes: The current total charge / discharge power of the energy storage system is determined based on the weighted value of the current charge / discharge power of each of the energy storage subsystems.

8. The method as described in claim 1, characterized in that, After the step of determining the current total charging / discharging power of the energy storage system based on the current charging / discharging power of each of the energy storage subsystems, the method further includes: When the current total charge / discharge power is greater than or equal to the target power lower limit, each energy storage subsystem is controlled to operate at the corresponding current charge / discharge power.

9. The method as described in claim 6, characterized in that, The method includes: Select the maximum equilibrium difference from the difference between the battery state of charge and the average battery state of charge for each energy storage subsystem; When the maximum difference in equilibrium exceeds the equilibrium threshold, the equilibrium coefficient is determined based on the objective function; When the maximum difference in the equilibrium is less than or equal to the equilibrium threshold, the preset equilibrium coefficient is determined as the equilibrium coefficient.

10. The method as described in claim 9, characterized in that, The step of determining the equilibrium coefficient based on the objective function when the maximum equilibrium difference is greater than the equilibrium threshold includes: When the maximum difference in the equilibrium is greater than the equilibrium threshold, the average charge / discharge power of all energy storage subsystems is determined based on the target power of the energy storage system and the number of energy storage subsystems. The equilibrium coefficient is calculated based on the objective function obtained by summing the squares of the differences between the current charging / discharging power and the average charging / discharging power of each energy storage subsystem.

11. An energy storage system, characterized in that, The energy storage system includes at least two parallel-connected energy storage subsystems, and each of the energy storage subsystems includes an energy storage battery and an energy storage bidirectional converter connected in series. The energy storage system further includes an energy balancing device, which has a communication connection with each of the energy storage subsystems. The energy balancing device includes a memory, a processor, and an energy balancing program or a program for determining the balancing coefficient stored in the memory and executable on the processor. The energy balancing program is configured to implement the steps of the energy balancing method of the energy storage system as described in any one of claims 1-10.

12. A computer-readable storage medium, characterized in that, It stores an energy balancing program or a program for determining the balancing coefficient of the energy storage system. When the energy balancing program of the energy storage system is executed by the processor, it implements the steps of the energy balancing method of the energy storage system as described in any one of claims 1-10.

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