Method, device and system for restraining circulating current of energy storage system based on dynamic impedance compensation

Abstract

The invention provides an energy storage system circulating current suppression method, device and system based on dynamic impedance compensation, and relates to the technical field of power grids. According to the invention, the controllable impedance module is connected in series between the battery clusters and the DC bus, the real-time current and the real-time SOC of each battery cluster and the voltage of the DC bus are monitored in real time, and whether the work of each battery cluster is abnormal is determined according to the real-time current and the real-time SOC of each battery cluster. And when the target battery cluster works abnormally, the impedance value of the controllable impedance module is adjusted according to the real-time current and the real-time SOC of each battery cluster and the DC bus voltage, so that the current among the battery clusters of the energy storage system is balanced, the circulating current among the battery clusters of the energy storage system is suppressed, and circulating current suppression among the parallel battery clusters of the energy storage system is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power grids, and particularly to a method, device and system for suppressing circulating current in an energy storage system based on dynamic impedance compensation. Background Art

[0002] In the application of parallel connection of multiple large-scale power energy storage and battery clusters on the DC side, as the batteries are used, the difference in internal resistance of each battery cluster gradually increases. In addition, the impedance of each device in the connection circuit of each battery cluster may change due to maintenance, ultimately resulting in different impedances among multiple parallel-connected battery clusters, causing an increase in circulating current during the parallel connection of battery clusters and inconsistent currents during charging and discharging of different battery clusters. Further, it may also lead to an increase in the calculation error of the SOC of each battery cluster, and ultimately cause the SOC difference of each battery cluster to gradually increase. And the energy storage strategy often conducts charge and discharge regulation according to the SOC of each battery cluster, and a large SOC difference seriously affects the charge and discharge efficiency of the entire energy storage system.

[0003] Therefore, in the current scenario of parallel operation of multiple battery clusters, due to differences such as connection impedance and battery internal resistance, there is a circulating current phenomenon between the parallel-connected battery clusters, which affects the operation reliability of the parallel-connected battery clusters. Summary of the Invention

[0004] The present invention provides a method, device and system for suppressing circulating current in an energy storage system based on dynamic impedance compensation. It solves the problem of circulating current between battery clusters in the energy storage system and realizes the suppression of circulating current between battery clusters in the energy storage system.

[0005] In a first aspect, the present invention provides a method for suppressing circulating current in an energy storage system based on dynamic impedance compensation, which is applied to an SOC balancing system. The SOC balancing system includes multiple battery clusters, and each battery cluster is connected to a DC bus through a controllable impedance module. The DC bus is connected to a large power grid through a PCS. The method includes: monitoring the real-time current, real-time SOC of each battery cluster, and the DC bus voltage; determining the status information of the target battery cluster based on the real-time current and real-time SOC of each battery cluster, where the status information includes normal operation or abnormal operation, and abnormal operation includes abnormal SOC and / or abnormal current; the target battery cluster is any one of the multiple battery clusters; if the target battery cluster operates abnormally, then determine the impedance target value of the target battery cluster based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage; adjust the controllable impedance module of the target battery cluster based on the impedance target value to achieve suppression of circulating current in the energy storage system.

[0006] In a possible implementation, based on the real-time current and real-time SOC of each battery cluster, the state information of the target battery cluster is determined, including: calculating the average current and average SOC of each battery cluster based on the real-time current and real-time SOC of each battery cluster; if the current difference between the real-time current and the average current of the target battery cluster is less than or equal to the current threshold, and the SOC difference between the real-time SOC and the average SOC is less than or equal to the SOC threshold, it is determined that the target battery cluster is operating normally; if the current difference between the real-time current and the average current of the target battery cluster is greater than the current threshold, and the SOC difference between the real-time SOC and the average SOC is less than or equal to the SOC threshold, it is determined that the current of the target battery cluster is abnormal; if the current difference between the real-time current and the average current of the target battery cluster is less than or equal to the current threshold, and the SOC difference between the real-time SOC and the average SOC is greater than the SOC threshold, it is determined that the SOC of the target battery cluster is abnormal; if the current difference between the real-time current and the average current of the target battery cluster is greater than the current threshold, and the SOC difference between the real-time SOC and the average SOC is greater than the SOC threshold, it is determined that the SOC of the target battery cluster is abnormal and the current is abnormal.

[0007] In a possible implementation, based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage, the impedance target value of the target battery cluster is determined, including: if the current of the target battery cluster is abnormal, calculating an impedance adjustment value based on the real-time current of the target battery cluster, the DC bus voltage, and the average current of each battery cluster; calculating the impedance target value based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster.

[0008] In a possible implementation, calculating the impedance adjustment value based on the real-time current, DC bus voltage, and average current of the target battery cluster, including: if the real-time current of the target battery cluster is greater than the average current, determining the impedance adjustment value based on the first formula and determining that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster; if the real-time current of the target battery cluster is less than the average current, determining the impedance adjustment value based on the first formula and determining that the impedance adjustment value is negative to decrease the real-time impedance of the controllable impedance module of the target battery cluster; where the first formula is ; is the impedance adjustment value, is the DC bus voltage, is the real-time current of the target battery cluster, is the average current of each battery cluster.

[0009] In a possible implementation, based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage, determining the impedance target value of the target battery cluster includes: if the SOC of the target battery cluster is abnormal, calculating the current target value based on the average current and average SOC of each battery cluster, and the real-time SOC of the target battery cluster; determining the impedance adjustment value based on the real-time current, current target value of the target battery cluster, and the DC bus voltage; calculating the impedance target value based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster.

[0010] In a possible implementation, based on the real-time current, current target value of the target battery cluster, and the DC bus voltage, determining the impedance adjustment value includes: if the SOC equalization system is in the charging state and the real-time SOC of the target battery cluster is less than the average SOC, determining the impedance adjustment value based on the second formula and determining that the impedance adjustment value is negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster; if the SOC equalization system is in the charging state and the real-time SOC of the target battery cluster is greater than the average SOC, determining the impedance adjustment value based on the second formula and determining that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster; where the second formula is ; is the impedance adjustment value, is the DC bus voltage, is the real-time current of the target battery cluster, is the current target value.

[0011] In a possible implementation, based on the real-time current, current target value of the target battery cluster, and the DC bus voltage, determining the impedance adjustment value includes: if the SOC equalization system is in the discharging state and the real-time SOC of the target battery cluster is less than the average SOC, determining the impedance adjustment value based on the second formula and determining that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster; if the SOC equalization system is in the discharging state and the real-time SOC of the target battery cluster is greater than the average SOC, determining the impedance adjustment value based on the second formula and determining that the impedance adjustment value is negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster.

[0012] Second aspect, an embodiment of the present invention provides a circulating current suppression device for an energy storage system based on dynamic impedance compensation, which is applied to an SOC balancing system. The SOC balancing system includes multiple battery clusters, and each battery cluster is connected to a DC bus through a controllable impedance module. The DC bus is connected to a large power grid through a PCS; the device includes: a communication module and a processing module; the communication module is used to monitor the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage; the processing module is used to determine the status information of the target battery cluster based on the real-time current and real-time SOC of each battery cluster. The status information includes normal operation or abnormal operation, and abnormal operation includes abnormal SOC and / or abnormal current; the target battery cluster is any one of the multiple battery clusters; if the target battery cluster operates abnormally, then based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage, determine the impedance target value of the target battery cluster; based on the impedance target value, adjust the controllable impedance module of the target battery cluster to achieve circulating current suppression of the energy storage system.

[0013] In a possible implementation manner, the processing module is specifically configured to, if the current of the target battery cluster is abnormal, calculate an impedance adjustment value based on the real-time current of the target battery cluster, the DC bus voltage, and the average current of each battery cluster; based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster, calculate the impedance target value.

[0014] Third aspect, an embodiment of the present invention provides an SOC balancing system, which includes multiple battery clusters and controllable impedance modules. Each battery cluster is connected to a DC bus through a controllable impedance module, and the DC bus is connected to a large power grid through a PCS; the controllable impedance module includes a memory and a processor. The memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to execute the steps of the method described in the first aspect and any possible implementation manner in the first aspect.

[0015] Fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program, and is characterized in that when the computer program is executed by a processor, it implements the steps of the method described in the first aspect and any possible implementation manner in the first aspect.

[0016] The present invention provides a method, device and system for suppressing circulating current in an energy storage system based on dynamic impedance compensation. The present invention connects a controllable impedance module in series between the battery cluster and the DC bus, and monitors the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage in real time, and determines whether the operation of each battery cluster is abnormal according to the real-time current and real-time SOC of each battery cluster. When the target battery cluster operates abnormally, the impedance value of the controllable impedance module is adjusted according to the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage, so that the current balance between the battery clusters of the energy storage system is achieved, the circulating current problem between the battery clusters of the energy storage system is suppressed, and the suppression of the circulating current between the parallel battery clusters of the energy storage system is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 is a schematic diagram of the architecture of an existing energy storage system; Figure 2 is a schematic diagram of the architecture of a SOC balancing system provided by an embodiment of the present invention; Figure 3 is a schematic flowchart of a method for suppressing circulating current in an energy storage system based on dynamic impedance compensation provided by an embodiment of the present invention; Figure 4 is a schematic flowchart of the adjustment of a controllable impedance module provided by an embodiment of the present invention; Figure 5 is a schematic diagram of the structure of a device for suppressing circulating current in an energy storage system based on dynamic impedance compensation provided by an embodiment of the present invention.

[0019] Figure 6 is a schematic diagram of the structure of a controllable impedance module provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0021] In the description of the present invention, unless otherwise specified, " / " means "or". For example, A / B may represent A or B. The "and / or" herein is merely a correlative relationship describing related objects, indicating that there can be three relationships. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, "at least one" and "a plurality of" mean two or more. The words such as "first" and "second" do not limit the quantity and execution order, and the words such as "first" and "second" do not necessarily limit to be different.

[0022] In the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner for easy understanding.

[0023] In addition, the terms "comprising" and "having" and any variations thereof mentioned in the description of the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally further include other unlisted steps or modules, or may optionally further include other steps or modules inherent to these processes, methods, products or devices.

[0024] To make the objectives, technical solutions and advantages of the present invention clearer, the following will be described through specific embodiments in conjunction with the drawings of the present invention.

[0025] Such as Figure 1As shown, there is currently an energy storage system. In this energy storage system, the battery management system (BMS) is divided into three layers: Each battery pack (PACK) contains one battery management unit (BMU) for functions such as collecting the voltage and temperature of each battery cell and calculating the state of charge (SOC) of the single battery. Each BMU communicates with the battery cluster management unit (BCMU) in the high-voltage box of its cluster; Each high-voltage box contains one BCMU for controlling the DC circuit breaker of the high-voltage box, collecting the current of each cluster, and forwarding the BMU data to the battery array management unit (BAMU); The BAMU is used to collect information from each PACK and each cluster and interact with the power conversion system (PCS). In the figure, each PACK in each battery cluster is composed of multiple battery cells connected in series; The PACKs within each battery cluster are connected in series; After the series connection within the battery cluster, the total positive of the batteries within the battery cluster and the total negative of the batteries within the battery cluster are connected to the high-voltage box of each battery cluster; The high-voltage boxes of each battery cluster connect the PACKs after series connection of each battery cluster in parallel to the DC bus through the DC circuit breaker; The DC bus is connected to the PCS; The PCS can charge or discharge the batteries of each battery cluster through the bus (when the battery is charging, the PCS converts the grid AC power into DC power to the bus, and when the battery is discharging, the PCS converts the battery DC power into AC power and discharges it to the large grid). When the impedances of each battery cluster are inconsistent, since each battery cluster is in parallel (i.e., the voltages are the same), according to Ohm's law, the current of the battery cluster with a smaller impedance is larger during charging and discharging, and the current of the battery cluster with a larger impedance is smaller; And the SOC of each battery cluster is usually calculated by the ampere-hour integration method, and the different currents will inevitably lead to inconsistent changes in the SOC of each battery cluster.

[0026] In addition, due to the difference in the current magnitude of each battery cluster, the actual charging amount of the batteries in each battery cluster will be different, that is, the actual battery voltages of each battery cluster are different (assuming the impedance of the battery cluster is R c , when the charging is about to stop, the voltage of the entire battery cluster is the voltage of the battery cluster impedance U Rc + the actual voltage U of the battery cluster Re , so the actual battery voltages of each battery cluster are different). If each battery cluster disconnects from the bus and then closes the bus again, different battery cluster impedances will cause a large circulating current (that is, the battery cluster with a higher voltage charges the battery cluster with a lower voltage).

[0027] Exemplarily, in the existing energy storage system with battery clusters connected in parallel on the DC side, the circulating current and SOC imbalance are mainly caused by the following reasons: Connection impedance difference: Cable aging, contact resistance change, and temperature gradient lead to inconsistent impedances.

[0028] Battery internal resistance difference: The aging degree, temperature, and manufacturing tolerance of the batteries in different battery clusters result in internal resistance differences.

[0029] Loop voltage mismatch: The impedance difference causes a voltage difference between battery clusters, forming a circulating current path.

[0030] Therefore, in the charging and discharging scenarios of parallel battery clusters, due to reasons such as differences in connection impedance, battery internal resistance, and loop voltage mismatch, there is a circulating current phenomenon between parallel battery clusters, which affects the charging and discharging efficiency and operation reliability of parallel battery clusters.

[0031] To solve the above technical problems, as Figure 2 shown, an embodiment of the present invention provides a SOC balancing system. The SOC balancing system includes multiple battery clusters, each battery cluster is connected to the DC bus through a controllable impedance module, and the DC bus is connected to the large power grid through a PCS.

[0032] In some embodiments, each battery cluster corresponds to each controllable impedance module one by one. Each battery cluster is connected in series with an independent controllable impedance module.

[0033] The first end of the main circuit of the controllable impedance module is connected to the battery cluster, and the second end is connected to the high-voltage box. The control circuit of the controllable impedance module is connected to the battery array management unit and communicates with the battery array management unit BAMU. After receiving the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage sent by the BAMU, and analyzing and processing them, the impedance value is adjusted to achieve circulating current suppression.

[0034] Exemplarily, the controllable impedance module can be a Buck-Boost type variable impedance, or it can also be a linear mode + switch modulation.

[0035] In some embodiments, the PCS: performs constant power charging and discharging on the battery clusters connected in parallel to the DC side through the bus.

[0036] The BAMU: collects the current, voltage, and SOC of each battery cluster, and sends the bus voltage and the minimum battery cluster current in each battery cluster to the controllable impedance module of each battery cluster in real time.

[0037] The BCMU: collects the voltage, current, and BMU information in the PACK of each battery cluster in real time.

[0038] Based on Figure 2 the SOC balancing system shown, as Figure 3 shown, an embodiment of the present invention provides a method for suppressing circulating current in an energy storage system based on dynamic impedance compensation. The method includes steps S101 - S104.

[0039] S101. Monitor the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage.

[0040] S102. Determine the status information of the target battery cluster based on the real-time current and real-time SOC of each battery cluster.

[0041] In the embodiments of the present application, the status information includes normal operation or abnormal operation, and the abnormal operation includes SOC abnormality and / or current abnormality; the target battery cluster is any one of multiple battery clusters.

[0042] As a possible implementation manner, step S102 can be specifically implemented as steps S1021 - S1025.

[0043] S1021. Calculate the average current and average SOC of each battery cluster based on the real-time current and real-time SOC of each battery cluster.

[0044] S1022. If the current difference between the real-time current and the average current of the target battery cluster is less than or equal to the current threshold, and the SOC difference between the real-time SOC and the average SOC is less than or equal to the SOC threshold, it is determined that the target battery cluster is operating normally.

[0045] S1023. If the current difference between the real-time current and the average current of the target battery cluster is greater than the current threshold, and the SOC difference between the real-time SOC and the average SOC is less than or equal to the SOC threshold, it is determined that the current of the target battery cluster is abnormal.

[0046] S1024. If the current difference between the real-time current and the average current of the target battery cluster is less than or equal to the current threshold, and the SOC difference between the real-time SOC and the average SOC is greater than the SOC threshold, it is determined that the SOC of the target battery cluster is abnormal.

[0047] S1025. If the current difference between the real-time current and the average current of the target battery cluster is greater than the current threshold, and the SOC difference between the real-time SOC and the average SOC is greater than the SOC threshold, it is determined that the SOC of the target battery cluster is abnormal and the current is abnormal.

[0048] S103. If the target battery cluster is operating abnormally, determine the impedance target value of the target battery cluster based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage.

[0049] As a possible implementation manner, step S103 can be specifically implemented as steps A1 - A2.

[0050] A1. If the current of the target battery cluster is abnormal, calculate the impedance adjustment value based on the real-time current of the target battery cluster, the DC bus voltage, and the average current of each battery cluster.

[0051] Exemplarily, if the real-time current of the target battery cluster is greater than the average current, determine the impedance adjustment value based on the first formula and determine that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster.

[0052] Another exemplary case is that if the real-time current of the target battery cluster is less than the average current, the impedance adjustment value is determined based on the first formula, and the impedance adjustment value is determined to be negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster.

[0053] Wherein, the first formula is ; is the impedance adjustment value, is the DC bus voltage, is the real-time current of the target battery cluster, is the average current of each battery cluster.

[0054] A2. Calculate the impedance target value based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster.

[0055] It should be noted that as Figure 4 shown, when the SOC of each battery cluster is the same and there are current differences, that is, the current is abnormal. Then ① each battery cluster controllable impedance module receives the current values of each battery cluster broadcast by the BAMU. The battery cluster n with a smaller current calculates the impedance ΔZ that needs to be reduced according to the current I n of this battery cluster, the average current I avg of each battery cluster and the DC bus voltage V, and changes the impedance accordingly; ② after the impedance of this battery cluster becomes smaller, the current of this battery cluster increases, and at the same time the currents of other battery clusters become smaller. Each battery cluster BCMU uploads the corresponding information to the BAMU in real time; ③ the BAMU broadcasts the information of each battery cluster received in real time to each battery cluster controllable impedance module; ④ the battery cluster controllable impedance module continues to adjust according to the method in ① until the currents of each battery cluster are balanced.

[0056] As another possible implementation manner, step S103 can be specifically implemented as steps B1 - B3.

[0057] B1. If the SOC of the target battery cluster is abnormal, calculate the current target value based on the average current and average SOC of each battery cluster, and the real-time SOC of the target battery cluster.

[0058] Exemplarily, in the embodiments of the present invention, the current target value can be calculated according to the following formula.

[0059] ; Wherein, is the current target value, is the average SOC, is the real-time SOC of the target battery cluster. T is the set duration, that is, the expected duration from the existence of current differences to current balance.

[0060] In this way, each battery cluster controllable impedance module obtains the average SOC of each battery cluster SOC by receiving the information of each battery cluster broadcast by the BAMU. The battery cluster n with a smaller SOC avg and the average current I of each battery cluster avg , aiming at equalizing the average SOC within time T, calculates the target current value that the battery cluster n needs to set.

[0061] B2. Based on the real-time current, current target value and DC bus voltage of the target battery cluster, determine the impedance adjustment value.

[0062] Exemplarily, if the SOC equalization system is in the charging state and the real-time SOC of the target battery cluster is less than the average SOC, the impedance adjustment value is determined based on the second formula, and it is determined that the impedance adjustment value is negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster.

[0063] Another exemplarily, if the SOC equalization system is in the charging state and the real-time SOC of the target battery cluster is greater than the average SOC, the impedance adjustment value is determined based on the second formula, and it is determined that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster.

[0064] Wherein, the second formula is ; is the impedance adjustment value, is the DC bus voltage, is the real-time current of the target battery cluster, is the current target value.

[0065] Another exemplarily, if the SOC equalization system is in the discharging state and the real-time SOC of the target battery cluster is less than the average SOC, the impedance adjustment value is determined based on the second formula, and it is determined that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster.

[0066] Another exemplarily, if the SOC equalization system is in the discharging state and the real-time SOC of the target battery cluster is greater than the average SOC, the impedance adjustment value is determined based on the second formula, and it is determined that the impedance adjustment value is negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster.

[0067] B3. Based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster, calculate the impedance target value.

[0068] It should be noted that, as Figure 4 shown, when the currents of each battery cluster are the same and there are differences in SOC, that is, the SOC is abnormal. For example, due to the replacement or repair of the battery cells in a certain battery cluster, there are differences in the SOC between a certain battery cluster and the SOC of other battery clusters, but the impedances are basically the same.

[0069] Charging scenario: ① Each battery cluster's controllable impedance module obtains the SOC average value SOC of each battery cluster and the average current value I of each battery cluster by receiving the information of each battery cluster broadcast by the BAMU. The battery cluster n with a smaller SOC calculates the current I that the battery cluster n needs to set with the goal of equalizing the average SOC within time T. avg ② The controllable impedance module of the battery cluster n adjusts the impedance of this battery cluster until the current output is I, calculates the impedance ΔZ that needs to be reduced, and makes the corresponding change to the impedance. avg ③ After the impedance of the battery cluster n becomes smaller, the current of the battery cluster n increases, while the currents of other battery clusters decrease. Each battery cluster's BCMU uploads the corresponding information to the BAMU in real time. ntarget ④ The BAMU broadcasts the information of each battery cluster received in real time to each battery cluster's controllable impedance module. ntarget ⑤ The controllable impedance module of the battery cluster continues to adjust according to the method in ① until the SOCs of all battery clusters are balanced.

[0070] Discharging scenario: ① Each battery cluster's controllable impedance module obtains the SOC average value SOC of each battery cluster and the average current value I of each battery cluster by receiving the information of each battery cluster broadcast by the BAMU. The battery cluster n with a smaller SOC calculates the current I that the battery cluster n needs to set with the goal of equalizing the average SOC within time T. avg ② The controllable impedance module of the battery cluster n adjusts the impedance of this battery cluster until the current output is I, calculates the impedance ΔZ that needs to be increased, and makes the corresponding change to the impedance. avg ③ After the impedance of the battery cluster n becomes larger, the current of the battery cluster n decreases, while the currents of other battery clusters increase. Each battery cluster's BCMU uploads the corresponding information to the BAMU in real time. ntarget ④ The BAMU broadcasts the information of each battery cluster received in real time to each cluster's controllable impedance module. ntarget ⑤ The controllable impedance module of the battery cluster continues to adjust from ① until the SOCs of all battery clusters are balanced.

[0071] As another possible implementation, when the SOCs of each battery cluster are different and the currents are different, the embodiments of the present invention can adjust the currents of each battery cluster based on steps A1 - A2, adjust the SOC equalization system to a state where the currents are basically the same and the SOCs are different, and then adjust the SOCs of each battery cluster based on steps B1 - B3 to suppress the circulating current while realizing the battery equalization of each battery cluster.

[0072] S104. Based on the impedance target value, adjust the controllable impedance module of the target battery cluster to achieve the suppression of the circulating current in the energy storage system.

[0073] The present invention provides a method for suppressing parallel circulating current based on dynamic impedance compensation. By connecting a controllable impedance module in series between the battery clusters and the DC bus, and monitoring the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage in real time, it is determined whether the operation of each battery cluster is abnormal according to the real-time current and real-time SOC of each battery cluster. When the target battery cluster operates abnormally, the impedance value of the controllable impedance module is adjusted according to the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage, so that the currents between the battery clusters of the energy storage system are balanced, the problem of circulating current between the battery clusters of the energy storage system is suppressed, and the suppression of the circulating current between the parallel battery clusters of the energy storage system is realized.

[0074] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0075] The following is an apparatus embodiment of the present invention. For the details not described in detail therein, reference may be made to the corresponding method embodiments above.

[0076] Figure 5 The structural schematic diagram of an apparatus for suppressing circulating current in an energy storage system based on dynamic impedance compensation provided by an embodiment of the present invention is shown. The parallel circulating current suppression apparatus 200 includes a communication module 201 and a processing module 202.

[0077] The communication module 201 is used to monitor the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage.

[0078] The processing module 202 is used to determine the status information of the target battery cluster based on the real-time current and real-time SOC of each battery cluster. The status information includes normal operation or abnormal operation, and abnormal operation includes SOC abnormality and / or current abnormality; the target battery cluster is any one of multiple battery clusters; if the target battery cluster operates abnormally, then based on the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage, determine the impedance target value of the target battery cluster; based on the impedance target value, adjust the controllable impedance module of the target battery cluster to achieve the suppression of the circulating current in the energy storage system.

[0079] Figure 6 The structural schematic diagram of a controllable impedance module provided by an embodiment of the present invention is shown. The controllable impedance module 300 includes: a processor 301, a memory 302, and a computer program 303 stored in the memory 302 and operable on the processor 301. When the processor 301 executes the computer program 303, the steps in the above method embodiments are implemented. Or, when the processor 301 executes the computer program 303, the functions of each module / unit in the above apparatus embodiments are implemented.

[0080] Exemplarily, the computer program 303 may be divided into one or more modules / units, which are stored in the memory 302 and executed by the processor 301 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program 303 in the controllable impedance module 300.

[0081] The so-called processor 301 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0082] The memory 302 may be an internal storage unit of the controllable impedance module 300, such as the hard disk or memory of the controllable impedance module 300. The memory 302 may also be an external storage device of the controllable impedance module 300, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the controllable impedance module 300. Further, the memory 302 may also include both the internal storage unit and the external storage device of the controllable impedance module 300. The memory 302 is used to store the computer program and other programs and data required by the terminal. The memory 302 may also be used to temporarily store the data that has been output or will be output.

[0083] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for suppressing circulating current in an energy storage system based on dynamic impedance compensation, characterized in that, Applied to the SOC balancing system, the SOC balancing system includes multiple battery clusters, each battery cluster is connected to the DC bus through a controllable impedance module, and the DC bus is connected to the large power grid through a PCS; the method includes: Monitoring the real-time current and real-time SOC of each battery cluster, as well as the DC bus voltage; Based on the real-time current and real-time SOC of each battery cluster, determining the status information of the target battery cluster, the status information includes normal operation or abnormal operation, and the abnormal operation includes SOC abnormality and / or current abnormality; the target battery cluster is any one of the multiple battery clusters; If the target battery cluster operates abnormally, then based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage, determining the impedance target value of the target battery cluster; Based on the impedance target value, adjusting the controllable impedance module of the target battery cluster to achieve the suppression of the energy storage system circulating current.

2. The method for suppressing circulating current in an energy storage system based on dynamic impedance compensation according to claim 1, wherein The determining the status information of the target battery cluster based on the real-time current and real-time SOC of each battery cluster includes: Based on the real-time current and real-time SOC of each battery cluster, calculating the average current and average SOC of each battery cluster; If the current difference between the real-time current and the average current of the target battery cluster is less than or equal to the current threshold, and the SOC difference between the real-time SOC and the average SOC is less than or equal to the SOC threshold, then it is determined that the target battery cluster operates normally; If the current difference between the real-time current and the average current of the target battery cluster is greater than the current threshold, and the SOC difference between the real-time SOC and the average SOC is less than or equal to the SOC threshold, then it is determined that the current of the target battery cluster is abnormal; If the current difference between the real-time current and the average current of the target battery cluster is less than or equal to the current threshold, and the SOC difference between the real-time SOC and the average SOC is greater than the SOC threshold, then it is determined that the SOC of the target battery cluster is abnormal; If the current difference between the real-time current and the average current of the target battery cluster is greater than the current threshold, and the SOC difference between the real-time SOC and the average SOC is greater than the SOC threshold, then it is determined that the SOC of the target battery cluster is abnormal and the current is abnormal.

3. The method for suppressing circulating current of an energy storage system based on dynamic impedance compensation according to claim 1, wherein The determining the impedance target value of the target battery cluster based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage includes: If the current of the target battery cluster is abnormal, then based on the real-time current of the target battery cluster, the DC bus voltage, and the average current of each battery cluster, calculating the impedance adjustment value; Based on the impedance adjustment value, and the real-time impedance value of the controllable impedance module of the target battery cluster, calculating the impedance target value.

4. The method for suppressing circulating current of an energy storage system based on dynamic impedance compensation according to claim 3, wherein, The calculating the impedance adjustment value based on the real-time current of the target battery cluster, the DC bus voltage, and the average current includes: If the real-time current of the target battery cluster is greater than the average current, then determining the impedance adjustment value based on the first formula and determining that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster; If the real-time current of the target battery cluster is less than the average current, then determining the impedance adjustment value based on the first formula and determining that the impedance adjustment value is negative to decrease the real-time impedance of the controllable impedance module of the target battery cluster; Among them, the first formula is ; is the impedance adjustment value, is the DC bus voltage, is the real-time current of the target battery cluster, is the average current of each battery cluster.

5. The method for suppressing circulating current of an energy storage system based on dynamic impedance compensation according to claim 1, characterized in that, Determining the impedance target value of the target battery cluster based on the real-time current, real-time SOC of each battery cluster, and the DC bus voltage includes: If the SOC of the target battery cluster is abnormal, calculate the current target value based on the average current and average SOC of each battery cluster, and the real-time SOC of the target battery cluster; Determine the impedance adjustment value based on the real-time current of the target battery cluster, the current target value, and the DC bus voltage; Calculate the impedance target value based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster.

6. The method for suppressing circulating current in an energy storage system based on dynamic impedance compensation according to claim 5, wherein The determining the impedance adjustment value based on the real-time current of the target battery cluster, the current target value, and the DC bus voltage includes: If the SOC equalization system is in the charging state and the real-time SOC of the target battery cluster is less than the average SOC, determine the impedance adjustment value based on the second formula and determine that the impedance adjustment value is negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster; If the SOC equalization system is in the charging state and the real-time SOC of the target battery cluster is greater than the average SOC, determine the impedance adjustment value based on the second formula and determine that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster; Among them, the second formula is ; is the impedance adjustment value, is the DC bus voltage, is the real-time current of the target battery cluster, is the current target value.

7. The method for suppressing circulating current in an energy storage system based on dynamic impedance compensation according to claim 6, wherein The determining the impedance adjustment value based on the real-time current of the target battery cluster, the current target value, and the DC bus voltage includes: If the SOC equalization system is in the discharging state and the real-time SOC of the target battery cluster is less than the average SOC, determine the impedance adjustment value based on the second formula and determine that the impedance adjustment value is positive to increase the real-time impedance of the controllable impedance module of the target battery cluster; If the SOC equalization system is in the discharging state and the real-time SOC of the target battery cluster is greater than the average SOC, determine the impedance adjustment value based on the second formula and determine that the impedance adjustment value is negative to reduce the real-time impedance of the controllable impedance module of the target battery cluster.

8. A circulating current suppression device for an energy storage system based on dynamic impedance compensation, characterized in that, Applied to an SOC equalization system, the SOC equalization system includes a plurality of battery clusters, each battery cluster is connected to the DC bus through a controllable impedance module, and the DC bus is connected to the large power grid through a PCS; the device includes: A communication module for monitoring the real-time current and real-time SOC of each battery cluster, and the DC bus voltage; A processing module for determining the status information of the target battery cluster based on the real-time current and real-time SOC of each battery cluster, the status information includes normal operation or abnormal operation, and the abnormal operation includes SOC abnormality and / or current abnormality; the target battery cluster is any one of the plurality of battery clusters; if the target battery cluster operates abnormally, determine the impedance target value of the target battery cluster based on the real-time current and real-time SOC of each battery cluster, and the DC bus voltage; based on the impedance target value, adjust the controllable impedance module of the target battery cluster to achieve the suppression of the circulating current in the energy storage system.

9. The device for suppressing circulating current of an energy storage system based on dynamic impedance compensation according to claim 8, wherein Specifically, if the current of the target battery cluster is abnormal, the processing module calculates the impedance adjustment value based on the real-time current of the target battery cluster, the DC bus voltage, and the average current of each battery cluster; calculates the impedance target value based on the impedance adjustment value and the real-time impedance value of the controllable impedance module of the target battery cluster.

10. A SOC balancing system, characterized in that, The SOC balancing system includes a plurality of battery clusters and a controllable impedance module. Each battery cluster is connected to the DC bus through the controllable impedance module, and the DC bus is connected to the large power grid through the PCS. The controllable impedance module includes a memory and a processor. The memory stores a computer program, and the processor is configured to call and run the computer program stored in the memory to execute the steps of the method according to any one of claims 1 to 7.

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