Energy storage system, circulation suppression method, device and medium in energy storage system

Abstract

The present invention provides an energy storage system, a method, device and medium for suppressing circulating current in an energy storage system. There are multiple energy storage units and a DC bus, wherein the energy storage unit includes a battery cluster, a transformer and a first switch, the battery cluster is connected to the DC bus via the first switch, the battery clusters in different energy storage units are connected in parallel via the DC bus, the primary side of the transformer is connected to the battery cluster, and the secondary side of the transformer is connected to the DC bus, wherein the transformer is used to transfer the energy of the battery cluster to the DC bus without passing through the first switch. In the technical solution of the present invention, the setting of the transformer can enable the energy storage system to adjust the voltage of each battery cluster internally before discharging to the outside, thereby reducing the loss of the circulating current phenomenon during use and extending the service life of the battery cluster and each component in the energy storage system.

Description

Technical Field

[0001] The present invention relates to an energy storage system, and specifically provides an energy storage system, a method, a device and a medium for suppressing circulating current in the energy storage system. Background Art

[0002] In existing energy storage systems, especially those involving multiple battery clusters running in parallel, circulation is prone to occur between battery clusters. This circulation phenomenon causes energy to circulate ineffectively between battery clusters, thereby increasing energy loss, reducing system efficiency, and may cause overheating or damage to battery clusters and other circuit components, shortening the battery life.

[0003] Accordingly, the art needs a new solution for suppressing circulating current between battery clusters to solve the above problems. Summary of the invention

[0004] In order to overcome the above defects, the present invention is proposed to solve or at least partially solve the technical problem that the circulation phenomenon is easy to occur between battery clusters in the prior art.

[0005] In a first aspect, the present invention provides an energy storage system, comprising: a plurality of energy storage units and a DC bus, wherein the energy storage unit comprises a battery cluster, a transformer and a first switch, the battery cluster is connected to the DC bus via the first switch, the battery clusters in different energy storage units are connected in parallel via the DC bus, the primary side of the transformer is connected to the battery cluster, the secondary side of the transformer is connected to the DC bus, wherein the transformer is used to transfer the energy of the battery cluster to the DC bus without passing through the first switch.

[0006] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, the energy storage system further includes a second switch, wherein the second switch is used to control the connection between the battery cluster and the transformer.

[0007] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, an inverter is provided on the primary side of the transformer, wherein the inverter converts the current output by the battery cluster during energy transfer into alternating current on the primary side of the transformer.

[0008] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the second switch includes: a first field effect transistor and a second field effect transistor, wherein the first end of the first field effect transistor is connected in series with the first end of the second field effect transistor, the second end of the first field effect transistor is connected to the primary side of the transformer, and the second end of the second field effect transistor is connected to the first pole of the battery cluster, wherein the first field effect transistor and the second field effect transistor are connected in a back-to-back manner; and / or, the second switch includes: a third field effect transistor and a fourth field effect transistor, wherein the first end of the third field effect transistor is connected in series with the first end of the fourth field effect transistor, the second end of the third field effect transistor is connected to the second end of the primary side of the transformer, the second end of the first field effect transistor is connected to the first end of the primary side of the transformer, and the second end of the fourth field effect transistor is connected to the second pole of the battery cluster, wherein the third field effect transistor and the fourth field effect transistor are connected in a back-to-back manner.

[0009] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the first field effect transistor and the second field effect transistor are both N-channel field effect transistors, and the first field effect transistor and the second field effect transistor both include a body diode, and the anode of the body diode is connected to the drain of the N-channel field effect transistor, and the cathode of the body diode is connected to the source of the N-channel field effect transistor.

[0010] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the energy storage system also includes a first capacitor and a second capacitor, wherein the first end and the second end of the first capacitor are respectively connected to the two endpoints of the primary side of the transformer, and the first end and the second end of the second capacitor are respectively connected to the two endpoints of the secondary side of the transformer.

[0011] In a second aspect, the present invention provides a method for suppressing circulating current in an energy storage system, the method comprising: wherein the energy storage system comprises a plurality of battery clusters and a power electronic conversion device, the battery cluster being connected to a DC bus via a first switch, the battery clusters being connected in parallel via a DC bus, wherein a first side of the power electronic conversion device is connected to the battery cluster, and a second side is connected to the DC bus, wherein the power electronic conversion device is used to transfer the energy of the battery cluster to the DC bus without passing through the first switch, the method comprising: obtaining an initial voltage of the battery cluster; performing energy transfer through the power electronic conversion device based on the initial voltage of the battery cluster, until the voltage of the battery cluster of the energy transfer recipient reaches a preset threshold, and then stopping the energy transfer.

[0012] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the energy storage system also includes a second switch, wherein the second switch is used to control the connection between the battery cluster and the power electronic conversion device; energy transfer is performed through the power electronic conversion device based on the initial voltage of the battery cluster, including: controlling the first switch corresponding to the battery cluster of the energy transfer sender to be in an off state, the second switch corresponding to the battery cluster of the energy transfer sender to be in an on state, the first switch corresponding to the battery cluster of the energy transfer receiver to be in an on state, and the second switch corresponding to the battery cluster of the energy transfer receiver to be in an off state.

[0013] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the initial voltage of the battery cluster is obtained and the battery cluster is divided into a first type of battery cluster and a second type of battery cluster based on the initial voltage of the battery cluster, wherein the initial voltage of the battery cluster in the first type of battery cluster is higher than the initial voltage of the battery cluster in the second type of battery cluster; at least one first battery cluster in the first type of battery cluster is controlled to transfer energy to at least one second battery cluster in the second type of battery cluster through a power electronic conversion device until the voltage of the second battery cluster reaches a preset threshold, and the energy transfer is stopped.

[0014] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the power electronic conversion device includes a transformer, wherein the primary side of the transformer is the first side of the power electronic conversion device, and the secondary side of the transformer is the second side of the power electronic conversion device, wherein an inverter is also provided on the primary side of the transformer, wherein the inverter converts the current output by the battery cluster in energy transfer into alternating current on the primary side of the transformer.

[0015] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the inverter is an electronic switch, wherein the inverter converts the current output by the battery cluster in energy transfer into alternating current on the primary side of the transformer, including: obtaining the current value on the DC bus; and controlling at least the switching frequency or the switching duty cycle of the inverter based on the current value.

[0016] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the switching frequency and switching duty cycle of the inverter are controlled based on the current value, including: when the current is greater than the current threshold, the duty cycle of the inverter is reduced; or, when the current is greater than the current threshold, the switching frequency of the inverter is reduced.

[0017] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the method for obtaining the preset threshold includes: obtaining the initial voltage of the battery cluster in the energy storage system; obtaining an average voltage based on the initial voltage of the battery cluster in the energy storage system; and using the average voltage as the preset threshold.

[0018] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the method for obtaining the preset threshold value includes: obtaining a voltage reduction curve of a battery cluster in the energy storage system; determining a voltage reduction range of the battery cluster based on the voltage reduction curve; taking the voltage reduction range of the battery cluster as a first constraint condition, combining the initial voltage and based on at least a first objective function, obtaining an optimized voltage of the corresponding battery cluster, wherein the first objective function minimizes the circulating energy loss of the energy storage system during external discharge; and taking the optimized voltage of the corresponding battery cluster as the preset threshold value of the corresponding battery cluster.

[0019] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the voltage reduction range of the battery cluster is taken as the first constraint condition, combined with the initial voltage and based on at least the first objective function, to obtain the optimized voltage of the corresponding battery cluster, including: taking the voltage reduction range of the battery cluster as the first constraint condition, combined with the initial voltage and based on the first objective function and the second objective function, to obtain the optimized voltage of the corresponding battery cluster, wherein the second objective function minimizes the voltage difference between the battery clusters during the external discharge of the energy storage system.

[0020] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the voltage reduction range of the battery cluster is taken as the first constraint condition, combined with the initial voltage and based on the first objective function and the second objective function, to obtain the optimized voltage of the corresponding battery cluster, including: assigning a preset first weight to the first objective function; assigning a preset second weight to the second objective function; adding the first objective function assigned with the preset first weight and the second objective function assigned with the preset second weight to obtain a third objective function; taking the voltage reduction range of the battery cluster as the first constraint condition, combining the initial voltage and the third objective function, to obtain the optimized voltage of the corresponding battery cluster.

[0021] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, determining the voltage reduction range of the battery cluster based on the voltage reduction curve includes: adjusting the acquired voltage reduction curve to a voltage reduction curve under the same load; inputting the initial voltage of the battery cluster and the adjusted voltage reduction curve into a trained neural network model to obtain the voltage reduction range of the battery cluster.

[0022] In a third aspect, a control device is provided, which includes a processor and a storage device, wherein the storage device is suitable for storing multiple computer programs, and the computer programs are suitable for being loaded and run by the processor to execute the method for suppressing circulating current in the energy storage system described in any one of the technical solutions of the method for suppressing circulating current in the energy storage system.

[0023] In a fourth aspect, a computer-readable storage medium is provided, which stores a plurality of computer programs, wherein the computer programs are suitable for being loaded and run by a processor to execute the method for suppressing circulating current in an energy storage system described in any one of the technical solutions of the method for suppressing circulating current in an energy storage system.

[0024] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0025] In the technical solution of the present invention, the transformer can be set to adjust the voltage of each battery cluster internally before the energy storage system is discharged to the outside, thereby reducing the loss of circulating current during use. In addition, the transformer can be set to adjust the current waveform on the transformer to control the strength of energy transfer in the process, thereby protecting the battery cluster and extending the service life of the battery cluster and various components in the energy storage system.

[0026] Furthermore, by using a power electronic conversion device to orderly regulate the energy transfer between battery clusters without triggering the first switch, the precise balance of the battery cluster voltage is achieved, so that the circulation phenomenon does not occur between the battery clusters. This significantly reduces the ineffective circulation of energy between battery clusters and improves the energy efficiency of the entire energy storage system. At the same time, this solution also avoids the risk of overheating or damage to the battery cluster, prolongs the service life of the battery, enhances the stability and reliability of the system, and ensures the efficient use of energy and the long-term operation safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, among which:

[0028] Figure 1 is a schematic diagram of an energy storage unit of an energy storage system according to an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of three energy storage units in an energy storage system according to an embodiment of the present invention;

[0030] Figure 3is a schematic flow chart of main steps of a method for suppressing circulating current in an energy storage system according to an embodiment of the present invention;

[0031] Figure 4 is a schematic flow chart of steps for obtaining a preset threshold value in a method for suppressing circulating current in an energy storage system according to an embodiment of the present invention;

[0032] Figure 5 It is a schematic flow chart of the steps of obtaining an optimized voltage in a method for suppressing circulating current in an energy storage system according to an embodiment of the present invention.

[0033] List of reference numerals:

[0034] Positive contactor, Y1; negative contactor, Y2; first field effect transistor, Q1; second field effect transistor, Q2; third field effect transistor, Q3; fourth field effect transistor, Q4; electronic switch, Q5; first capacitor, C1; second capacitor, C2; transformer, T1. DETAILED DESCRIPTION

[0035] Some embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0036] In the description of the present invention, "module" and "processor" may include hardware, software or a combination of the two. A module may include hardware circuits, various suitable sensors, communication ports, and memories, and may also include software parts, such as computer programs, or a combination of software and hardware. The processor may be a central processing unit, a microprocessor, an image processor, a digital signal processor, or any other suitable processor. The processor has data and / or signal processing functions. The processor may be implemented in software, hardware, or a combination of the two. Non-temporary computer-readable storage media include any suitable medium that can store computer programs, such as magnetic disks, hard disks, optical disks, flash memory, read-only memory, random access memory, etc. The term "A and / or B" means all possible combinations of A and B, such as only A, only B, or A and B. The term "at least one A or B" or "at least one of A and B" has a similar meaning to "A and / or B", and may include only A, only B, or A and B. The singular terms "one" and "the" may also include plural forms.

[0037] Embodiment 1:

[0038] See attached Figure 1 , Figure 1 Schematic diagram of a minimum unit (energy storage unit) in an energy storage system according to an embodiment of the present invention. Figure 2It is a schematic diagram of multiple energy storage units in the energy storage system, where Figure 2 An energy storage system consisting of three energy storage units is demonstrated.

[0039] In this embodiment, the energy storage system includes multiple energy storage units and a DC bus, wherein the energy storage unit includes a battery cluster, a power electronic conversion device and a first switch, the battery cluster is connected to the DC bus through the first switch, and the battery clusters in different energy storage units are connected in parallel through the DC bus, wherein the first side of the power electronic conversion device is connected to the battery cluster, and the second side is connected to the DC bus, wherein the power electronic conversion device is used to transfer the energy of the battery cluster to the DC bus without passing through the first switch. In one embodiment, the power electronic conversion device is a transformer.

[0040] In one embodiment, each battery cluster is connected to the DC bus through a first switch, and all battery clusters are connected in parallel through the DC bus, thereby ensuring that a parallel structure is formed between the battery clusters to facilitate external power supply. The first switch includes a positive contactor Y1 and a negative contactor Y2, wherein the positive contactor Y1 is used to control the connection between the battery cluster and the positive electrode of the DC bus, and is located between the positive electrode of the battery cluster and the positive electrode of the DC bus. The negative contactor Y2 is used to control the connection between the battery cluster and the negative electrode of the DC bus, and is located between the negative electrode of the battery cluster and the negative electrode of the DC bus. When the first switch is in the off state, the positive contactor Y1 and the negative contactor Y2 are both in the off state, and vice versa. The use of two contactors can ensure that when the power is off or the battery cluster needs to be isolated for maintenance, the electrical connection between the battery cluster and the rest of the system can be completely disconnected, which helps prevent accidental current flow and provides a safer working environment.

[0041] The power electronic conversion device can convert the direct current from the battery cluster into alternating current with different voltage or current characteristics. The power electronic conversion device can reduce the energy transfer rate between the battery clusters during energy transfer through scheduling, thereby protecting the battery cluster. The first side of the power electronic conversion device is connected to the battery cluster, and the second side is connected to the DC bus. Such a configuration allows the power electronic conversion device to directly transfer the energy of the battery cluster to the DC bus without passing through the first switch. At this time, the power electronic conversion device also plays the role of isolating the battery cluster.

[0042] Furthermore, based on the above circuit, a corresponding control method is proposed, namely, a circulating current suppression method in an energy storage system, which specifically includes step A and step B, such as Figure 3 As shown, the details are as follows:

[0043] Step A: Obtain the initial voltage of the battery cluster.

[0044] In one embodiment, the initial voltage of the battery cluster is obtained through a battery management system (BMS). The BMS is responsible for monitoring key parameters of the battery cluster, including voltage, temperature, etc. The battery management system monitors each battery cluster in real time to ensure that all components operate within safe and preset operating parameters.

[0045] In this embodiment, the initial voltage of the battery cluster directly determines the demand and limitation of energy transfer. Only by accurately understanding the initial voltage state of each battery cluster can the operation of the power electronic conversion device be effectively controlled to ensure that energy is transferred with optimal efficiency.

[0046] In one implementation, step A includes step A01, which is specifically as follows:

[0047] Step A01: acquiring initial voltages of battery clusters and classifying the battery clusters into first-type battery clusters and second-type battery clusters based on the initial voltages of the battery clusters.

[0048] In one embodiment, an initial voltage of the battery clusters in the first type of battery clusters is higher than an initial voltage of the battery clusters in the second type of battery clusters.

[0049] Furthermore, in one embodiment, first, the BMS obtains the initial voltage of each battery cluster. Then, the system calculates the average value of the voltages of all battery clusters, that is, the average voltage. This average voltage is used to classify the battery clusters into two categories: battery clusters with initial voltages higher than the average value are classified as first-category battery clusters; battery clusters with initial voltages lower than the average value are classified as second-category battery clusters.

[0050] The main reason for classifying battery clusters is to achieve effective energy management and optimize the charging and discharging process of battery clusters. If battery clusters with initial voltages higher than the average and battery clusters with initial voltages lower than the average are charged together without interference, a circulation phenomenon will occur. Therefore, the purpose of classifying battery clusters is to eventually adjust all battery clusters to the same voltage level to reduce circulation losses. Circulation losses are caused by voltage imbalance between battery clusters. When battery clusters are connected in parallel with different voltages, the battery cluster with higher voltage will transfer current to the battery cluster with lower voltage, causing energy loss and accelerating battery aging. This situation can be effectively avoided by adjusting the initial voltage of the battery cluster before the system outputs power.

[0051] In this embodiment, the battery clusters are divided into a first battery cluster and a second battery cluster by the average voltage, so that in subsequent processing, the energy storage system can adjust the battery clusters to the same voltage with higher efficiency, thereby reducing circulation losses and improving the performance and economic benefits of the entire system.

[0052] Step B: Energy transfer is performed through a power electronic conversion device based on the initial voltage of the battery cluster until the voltage of the battery cluster at the energy transfer recipient reaches a preset threshold, and then the energy transfer is stopped.

[0053] In one embodiment, in an energy storage system, the process of energy transfer using a power electronic conversion device involves transferring electrical energy from a battery cluster with a higher voltage (energy transfer sender) to a battery cluster with a lower voltage (energy transfer receiver). In order to accurately control this process, a first switch and a second switch are introduced into the system.

[0054] In one embodiment, the energy storage system further includes a second switch, wherein the second switch is used to control the connection between the battery cluster and the power electronic conversion device. During the energy transfer process, the first switch corresponding to the battery cluster of the energy transfer sender is controlled to be in an off state, the second switch corresponding to the battery cluster of the energy transfer sender is controlled to be in an on state, the first switch corresponding to the battery cluster of the energy transfer receiver is controlled to be in an on state, and the second switch corresponding to the battery cluster of the energy transfer receiver is controlled to be in an off state.

[0055] The function of the second switch is to control the connection between the battery cluster and the power electronic conversion device. In the specific execution of energy transfer, the first switch corresponding to the battery cluster of the energy transfer sender is in the disconnected state, and the second switch is in the on state, which can ensure that the energy of the battery cluster of the energy transfer sender is directly transmitted to the power electronic conversion device, and the energy is input to the DC bus through the power electronic conversion device, rather than directly through the DC bus. At the same time, the first switch of the battery cluster of the energy transfer receiver is in the on state, and the second switch is in the off state, which allows the battery cluster of the energy transfer receiver to receive energy directly from the DC bus. This switch configuration ensures the directness and priority of the energy transmission path, and the rate of energy transfer can be regulated by regulating the power electronic conversion device.

[0056] In this embodiment, a stable and controllable energy transfer path is constructed through the above-mentioned switch opening and closing scheme. By precisely controlling which switches are turned on and which are turned off, the system can effectively manage the flow of energy to ensure that energy is exchanged only between the required battery clusters without affecting other parts of the system. This not only improves the efficiency of energy transfer, but also significantly improves the safety and accuracy of system operation. By preventing energy exchange between battery clusters directly through the DC bus, the system can avoid the problem of uncontrolled current that is easily caused when energy is transferred directly through the bus. This uncontrolled current phenomenon can easily damage the battery cluster that is performing energy transfer.

[0057] In addition, this energy transfer method allows the system to perform internal voltage regulation and balancing when it is not outputting power to the outside, reducing circulation losses. By adjusting and balancing the initial voltage of the battery cluster before the system has yet to output power to the outside, the energy storage system can reach a more stable and efficient working state before starting external output.

[0058] Furthermore, energy transfer is performed through step B01, as follows.

[0059] Step B01: Control at least one first battery cluster in the first type of battery clusters to transfer energy to at least one second battery cluster in the second type of battery clusters through a power electronic conversion device until the voltage of the second battery cluster reaches a preset threshold, and then stop the energy transfer.

[0060] In one embodiment, the system first identifies the battery cluster with the highest initial voltage among the first type of battery clusters, i.e., the first battery cluster with the highest initial voltage ranking, and the second battery cluster with the lowest initial voltage among the second type of battery clusters, i.e., the second battery cluster with the lowest initial voltage ranking. This selection is based on transferring energy from the battery cluster with the high initial voltage to the battery cluster with the low initial voltage, aiming to quickly balance the voltage gap between the battery clusters.

[0061] In this embodiment, the control strategy does not stop at the initial energy transfer. Once the voltage of the first battery cluster reaches the average voltage during the transfer process, and the voltage of the related second battery cluster has not yet reached the average voltage, the system will automatically adjust to instruct the battery cluster with the second highest initial voltage in the first type of battery clusters to continue to supply energy to the same battery cluster in the second type of battery clusters.

[0062] On the contrary, if the voltage of the second battery cluster reaches the average voltage of the system first during the energy transfer process, while the voltage of the first battery cluster is still high, the transfer direction will continue from the first battery cluster to the second battery cluster with the second highest initial voltage ranking from low to high in the second battery cluster, until the voltage of one of the battery clusters also approaches the average value. The advantage of this strategy is that it can flexibly cope with the dynamics of voltage changes between battery clusters, gradually and evenly balance the voltages of each battery cluster, and enhance the overall stability and reliability of the system.

[0063] Furthermore, in one embodiment, the power electronic conversion device includes a transformer T1, wherein the primary side of the transformer T1 is the first side of the power electronic conversion device, and the secondary side of the transformer T1 is the second side of the power electronic conversion device, wherein an inverter is also provided on the primary side of the transformer T1, wherein the inverter converts the current output by the first battery cluster into alternating current on the primary side of the transformer T1.

[0064] The method further includes steps B02-B03, which are specifically as follows:

[0065] Step B02: Obtain the current value on the DC bus.

[0066] In one implementation, obtaining the current value is achieved by a current sensor installed on the DC bus.

[0067] Step B03: Control at least the switching frequency or the switching duty ratio of the inverter based on the current value.

[0068] In this embodiment, the inverter is an electronic switch Q5.

[0069] In one embodiment, the switching frequency or duty cycle of the inverter directly affects the output characteristics of the AC power, including voltage waveform, frequency and amplitude. Adjusting the switching frequency or duty cycle of the inverter can accurately control the output of energy to control the intensity of the entire energy transfer process.

[0070] Furthermore, in one embodiment, when the current is greater than the current threshold, the duty cycle of the inverter is reduced; or, when the current is greater than the current threshold, the switching frequency of the inverter is reduced.

[0071] When the monitored current value exceeds the preset current threshold, it indicates that the current in the system may be too high. At this time, by reducing the duty cycle or switching frequency of the inverter, the current output on the AC side can be reduced to avoid the risks caused by excessive current.

[0072] In this embodiment, the energy storage system not only needs high efficiency during the energy transfer process, but also needs to ensure the safety of the process. Step B is essentially a circulation, which is different from the general circulation in that the circuit in the circulation process can be effectively controlled by the control of the power electronic conversion device and the inverter.

[0073] When the current is too large, it will not only increase energy loss, but also cause the battery cluster to overheat or even be damaged, reducing the life of the battery cluster. In addition, when the power electronic conversion device is a transformer T1, the large current may also cause unnecessary electromagnetic interference, affecting the normal operation of the system and surrounding equipment. In this embodiment, steps B02 and B03 not only ensure the efficiency of energy transfer, but also improve the safety and stability of the system. By monitoring the current in real time and adjusting the operation of the inverter accordingly, this mechanism effectively controls the circulating current during the energy transfer process, ensuring the stable and controllable operation of the entire system.

[0074] Furthermore, in one embodiment, the second switch includes: a first field effect transistor Q1 and a second field effect transistor Q2, wherein a first end of the first field effect transistor Q1 is connected in series with a first end of the second field effect transistor Q2, a second end of the first field effect transistor Q1 is connected to a first side of the power electronic conversion device, and a second end of the second field effect transistor Q2 is connected to a first pole of the battery cluster, wherein the first field effect transistor Q1 and the second field effect transistor Q2 are connected back to back.

[0075] Furthermore, in one embodiment, the first field effect transistor Q1 and the second field effect transistor Q2 are both N-channel field effect transistors, and the first field effect transistor Q1 and the second field effect transistor Q2 both include a body diode, wherein the anode of the body diode is connected to the drain of the N-channel field effect transistor, and the cathode of the body diode is connected to the source of the N-channel field effect transistor.

[0076] In this embodiment, the second switch adopts a series configuration of a first field effect transistor Q1 and a second field effect transistor Q2, and the two field effect transistors are connected in a back-to-back manner. In this embodiment, the first end of the first field effect transistor Q1 is connected in series with the first end of the second field effect transistor Q2, and the other end (second end) of the first field effect transistor Q1 is connected to the first side of the power electronic conversion device, and the other end (second end) of the second field effect transistor Q2 is connected to the first pole of the battery cluster. The back-to-back arrangement in this connection method is mainly to ensure the unidirectional flow of current and provide reverse current protection, especially to resist peak current at the moment of opening and closing the second switch.

[0077] Furthermore, each field effect tube contains a body diode, so the peak current can be resisted in a back-to-back manner. In this embodiment, the source of the first field effect tube Q1 serves as the first end of the first field effect tube Q1, the drain of the first field effect tube Q1 serves as the second end of the first field effect tube Q1, the drain of the second field effect tube Q2 serves as the first end of the second field effect tube Q2, and the source of the second field effect tube Q2 serves as the second end of the second field effect tube Q2. In this embodiment, the presence of the body diode can prevent unexpected current from flowing in reverse when the field effect tube is turned off, thereby improving the overall safety of the system.

[0078] In this embodiment, the configuration of the first field effect transistor Q1 and the second field effect transistor Q2 also improves the fault tolerance of the energy storage system. When one of the first field effect transistor Q1 or the second field effect transistor Q2 is short-circuited, the other field effect transistor can still work.

[0079] Furthermore, in one embodiment, N-channel field effect transistors are used due to their high efficiency in conducting electricity and low on-resistance, which enable N-channel field effect transistors to switch at high power and high frequency.

[0080] Furthermore, in one embodiment, the second switch also includes: a third field effect transistor Q3 and a fourth field effect transistor Q4, wherein the first end of the third field effect transistor Q3 is connected in series with the first end of the fourth field effect transistor Q4, the second end of the third field effect transistor Q3 is connected to the second end of the first side of the power electronic conversion device, the second end of the first field effect transistor Q1 is connected to the first end of the first side of the power electronic conversion device, and the second end of the fourth field effect transistor Q4 is connected to the second pole of the battery cluster, wherein the third field effect transistor Q3 and the fourth field effect transistor Q4 are connected in a back-to-back manner.

[0081] The functions of the third field effect transistor Q3 and the fourth field effect transistor Q4 are similar to those of the first field effect transistor Q1 and the second field effect transistor Q2, and will not be described in detail here. The difference is that they are arranged at the second pole of the battery cluster to protect the second pole from being affected by the peak current when the second switch is turned on and off. The first pole and the second pole of the battery cluster are opposite electrodes. When the first pole of the battery cluster is the positive pole, the second pole of the battery cluster is the negative pole, and vice versa.

[0082] Furthermore, in one embodiment, the energy storage system also includes a first capacitor C1 and a second capacitor C2, wherein the first end and the second end of the first capacitor C1 are respectively connected to the two endpoints of the first side of the transformer T1, and the first end and the second end of the second capacitor C2 are respectively connected to the two endpoints of the second side of the transformer T1.

[0083] In this embodiment, the first capacitor C1 and the second capacitor C2 are used to protect the circuit. Specifically, the transformer T1 may generate voltage fluctuations during the energy conversion process. The first capacitor C1 and the second capacitor C2 can smooth these instantaneous voltage fluctuations through the stored charges, thereby protecting the sensitive components in the circuit from damage. In addition, the first capacitor C1 and the second capacitor C2 can also absorb the peak current generated by the second switch opening and closing, thereby protecting the entire energy storage system.

[0084] Embodiment 2:

[0085] Most of the technologies in this embodiment are the same as those in Embodiment 1, except that the preset threshold in this embodiment is not the average voltage. Other than that, the remaining technologies are the same as those in Embodiment 1 and will not be described in detail here.

[0086] In the first embodiment, the preset threshold is the average voltage. The current always moves in the direction of the voltage difference, so the average voltage can ensure that there is no circulating current between the battery clusters in the energy storage system.

[0087] However, in actual operation, by detecting the outward output power of the battery cluster, it was found that sometimes there was still power loss that could not be explained by heat loss. Through research, it was found that the cause of the problem was that the use of average voltage could not always guarantee that there would be no circulation phenomenon during the operation of the energy storage system. Through further research, it was found that the voltage reduction curves of the various battery clusters in the energy storage system were different, resulting in different battery cluster voltages in the energy storage system during the discharge process, which led to the generation of circulation phenomenon.

[0088] In the use of the energy storage system, the second switch is in the closed state, and the battery clusters turned on in the energy storage system are connected in parallel through the DC bus. In this process, if the voltages between the battery clusters are different, a circulating current will be generated. However, unlike the energy transfer through the power electronic conversion device, this circulating current is an uncontrolled circulating current.

[0089] Uncontrolled circulating current in the energy storage system is very dangerous to the battery cluster. Excessive current will greatly damage the life of the battery cluster. In addition, this uncontrolled circulating current consumption will greatly affect the power released by the energy storage system to the outside, causing large power fluctuations.

[0090] Therefore, based on the embodiments, the inventors have proposed a new technical problem, namely, how to reduce as much as possible the circulating current loss caused by the circulating current phenomenon in the energy storage system during the discharge process.

[0091] To address this problem, steps B04-B07 are designed, such as Figure 4 As shown, the details are as follows:

[0092] Step B04: Obtain the voltage reduction curve of the battery cluster in the energy storage system.

[0093] In one embodiment, the voltage reduction curve describes the characteristics of the voltage change over time of the battery cluster during the discharge process, and can reflect the actual working state of the battery cluster under different load conditions.

[0094] In this embodiment, the voltage and current data of each battery cluster in the energy storage system are monitored and recorded by the battery management system, and the voltage reduction curve of each battery cluster can be drawn.

[0095] In one embodiment, the obtained voltage reduction curve is converted into a voltage reduction curve under the same load (unit load). In one embodiment, the battery management system records the voltage reduction curves of the same battery cluster under different load conditions, and then processes and corrects the data. The voltage reduction curves of different battery clusters that originally correspond to different loads are converted into voltage reduction curves for the same load (unit load). In this way, the influence of different load conditions on the voltage reduction curve can be eliminated, making the voltage reduction curves of each battery cluster comparable.

[0096] In this embodiment, by analyzing the voltage reduction curve under the same load, the aging degree of different battery clusters can be understood.

[0097] Step B05: Determine the voltage reduction range of the battery cluster based on the voltage reduction curve.

[0098] In one embodiment, the voltage reduction range of the battery cluster is determined by a neural network method, which uses the initial voltage and voltage reduction curve of the battery cluster to analyze and calculate through a neural network model to determine the voltage adjustment range that each battery cluster can achieve during the energy transfer process.

[0099] In one embodiment, the voltage reduction curve of each battery cluster is obtained in step B04 and adjusted to the curve under the same load. This adjustment is to reduce the noise impact of the voltage reduction curve under different load conditions, so that the neural network can more accurately understand the voltage change characteristics represented by the curve during the analysis process. By eliminating the interference of different load conditions on the voltage reduction curve, the accuracy of the voltage reduction range prediction can be improved, so that the neural network can more reliably output the voltage adjustment range of the battery cluster during the energy transfer process.

[0100] Afterwards, the initial voltage of the battery cluster and the adjusted voltage reduction curve are input into the neural network model. In one embodiment, the neural network model includes an input layer, an LSTM layer, a fully connected layer, and an output layer. The input layer receives the initial voltage and voltage reduction curve data of the battery cluster, and the LSTM layer processes the voltage reduction curve to extract the time series features and patterns therein. The fully connected layer combines the initial voltage and the output of the LSTM layer, further processes these features, and generates the final voltage reduction range at the output layer.

[0101] Specifically, the fully connected layer is responsible for further comparing and analyzing the characteristics of the voltage reduction curves of different battery clusters extracted by the LSTM layer, so as to obtain the subtle differences. Then the fully connected layer will assign weights to these differences and analyze them together with the initial voltages of each battery cluster input, and input the analysis results to the output layer.

[0102] In this embodiment, by adjusting the voltage drop curve to data under the same load, the noise interference in the analysis process can be reduced and the accuracy of the voltage drop range prediction can be improved. Secondly, the obtained voltage drop range is used as a constraint condition to limit the numerical boundary in the energy transfer process, thereby narrowing the range for subsequent optimization calculations and making the optimization process more efficient and accurate. In addition, the neural network method can avoid many factors that affect the voltage drop range of the battery cluster, such as battery capacity. Under a relatively simple premise, the neural network can better handle these complex factors and achieve accurate prediction of the voltage drop range. Finally, with the accumulation of usage data, the neural network model can be continuously iterated and optimized, so that the output voltage drop range becomes more and more accurate.

[0103] Furthermore, in one embodiment, during the training of the neural network model, a large amount of historical data is used for training to ensure that the neural network can capture the laws and characteristics of the battery cluster voltage changes. The training goal of the neural network model is to minimize the error between the predicted voltage reduction range and the actual voltage reduction range. By continuously adjusting the model parameters, the accuracy and reliability of the prediction are improved.

[0104] In summary, a neural network is used to determine the voltage reduction range of the battery cluster. By adjusting the voltage reduction curve and analyzing the neural network, the voltage adjustment range of the battery cluster during the energy transfer process can be accurately predicted. This method is not only simple, but also provides important constraints for subsequent optimization calculations. With the accumulation of data and model optimization, the neural network can provide more and more accurate predictions of the voltage reduction range, further improving the overall performance and reliability of the energy storage system.

[0105] Step B06: taking the voltage reduction range of the battery cluster as the first constraint condition, combining the initial voltage and based at least on the first objective function, to obtain the optimized voltage of the corresponding battery cluster.

[0106] In this embodiment, the first objective function minimizes the circulating energy loss of the energy storage system during external discharge.

[0107] In one implementation, a derivation method of the first objective function is given here, as follows:

[0108] For multiple battery clusters (assuming there are N battery clusters), first calculate the circulation loss between each pair of battery clusters and sum them up. Assume that the discharge curve of each battery cluster is as follows:

[0109] ;

[0110] The discharge curve is expressed as a function, where x represents the number of the battery cluster.

[0111] For any two battery clusters i and j, the circulating current is:

[0112] ;

[0113] in, is the equivalent internal resistance between battery clusters i and j, where is the voltage of the ith battery cluster at time t, is the voltage of the jth battery cluster at time t.

[0114] The corresponding circulation energy loss is:

[0115] ;

[0116] The total circulating energy loss is:

[0117] ;

[0118] This formula indicates that the circulation loss of the battery cluster i=1 and the battery cluster i=2~N will be calculated, and the circulation loss generated by the battery cluster i=2 and the battery cluster i=3~N will also be calculated. Until i=N-1. And the superposition of all the circulation losses calculated above is the circulation loss in the entire discharge process. Where T is the time for the energy storage system to discharge outwards. This discharge time is usually related to the requirements during use and is a preset value.

[0119] In this implementation, the first objective function can be derived according to the above content as follows:

[0120] .

[0121] In one embodiment, the voltage reduction range of the battery cluster is used as the first constraint condition, and the battery cluster voltage is input into the circulating loss model, and the optimized voltage of the corresponding battery cluster is obtained based on the first objective function and the second objective function, wherein the second objective function minimizes the voltage difference between the battery clusters during the external discharge of the energy storage system.

[0122] By combining the first objective function, the voltage reduction range and the initial voltage of each battery cluster, the voltage of each battery cluster with the minimum circulating energy loss during the external discharge of the energy storage system can be obtained, which is the optimized voltage of the battery cluster.

[0123] Furthermore, in one embodiment, the present application also proposes a second objective function, and step B06 includes: taking the voltage reduction range of the battery cluster as the first constraint condition, combining the initial voltage and based on the first objective function and the second objective function, to obtain the optimized voltage of the corresponding battery cluster, wherein the second objective function minimizes the voltage difference between the battery clusters during the external discharge of the energy storage system.

[0124] In one implementation, the mathematical expression of the second objective function is as follows:

[0125] ;

[0126] in Indicates the start time of discharge. Indicates the discharge end time.

[0127] The second objective function is set to ensure that the voltage difference between battery clusters is as small as possible during the entire discharge process. The significance of this goal is to reduce the circulating current and thus protect the battery cluster. Although circulating current is inevitable when the energy storage system is discharged, the damage to the battery cluster can be minimized by controlling the size of the circulating current. Therefore, minimizing the voltage difference protects the battery cluster and prolongs its service life.

[0128] In one embodiment, the first objective function and the second objective function are combined through steps B06-1 to B026-4 to obtain, such as Figure 5 shown.

[0129] Step B06-1: assigning a preset first weight to the first objective function.

[0130] Step B06-2: assigning a preset second weight to the second objective function.

[0131] Step B06-3: Add the first objective function assigned with the preset first weight and the second objective function assigned with the preset second weight to obtain a third objective function.

[0132] In one implementation, the mathematical expression of the third objective function is as follows:

[0133] ;

[0134] in, and are the first weight and the second weight respectively.

[0135] In this embodiment, the importance of minimizing the circulating current energy loss and the voltage difference is balanced by setting the first weight and the second weight, wherein the first weight and the second weight are preset values.

[0136] Furthermore, in one embodiment, the dimensionless mathematical expression of the third objective function is as follows:

[0137] ;

[0138] is the first objective function after dimensionless transformation, It is the second objective function after dimensionless transformation.

[0139] The specific steps of dimensionless transformation are: calculate the first objective function and the second objective function respectively, and standardize the results of the calculation. Specifically, all the circulation losses obtained in the calculation process of the first objective function are transformed, and all the circulation losses are transformed into standard normal distribution by calculating the mean and standard deviation. Similarly, this method is used to process the results calculated in the second objective function in the same way.

[0140] The reason for the above processing is to make the first objective function and the second objective function dimensionless so that they can be compared and weighted on the same scale.

[0141] Step B06-4: taking the voltage reduction range of the battery cluster as the first constraint condition, combining the battery cluster voltage and the third objective function, and obtaining the optimized voltage of the corresponding battery cluster.

[0142] In one implementation, the third objective function is calculated by gradient descent until convergence, thereby obtaining the optimized voltage of each battery cluster.

[0143] Step B07: using the optimized voltage of the corresponding battery cluster as the preset threshold of the corresponding battery cluster.

[0144] In one embodiment, the optimized voltage is used as a preset threshold to ensure that the overall circulation loss of each battery cluster in the energy storage system is minimized during the voltage change during the discharge process, and the current when the circulation occurs is minimized, thereby protecting each battery cluster in the energy storage system.

[0145] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, different steps do not have to be performed in such an order. They can be performed simultaneously (in parallel) or in other orders. These changes are within the scope of protection of the present invention.

[0146] It is understood by those skilled in the art that the present invention implements all or part of the processes in the method of the above embodiment, and can also be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of each of the above method embodiments when executed by the processor. Among them, the computer program includes a computer program, and the computer program can be in source code form, object code form, executable file or some intermediate form. The computer-readable storage medium may include: any entity or device, medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium that can carry the computer program. It should be noted that the content contained in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electric carrier signals and telecommunication signals.

[0147] Furthermore, the present invention also provides a control device. In an embodiment of a control device according to the present invention, the control device includes a processor and a storage device. The storage device can be configured to store a program for executing the method for suppressing circulating current in an energy storage system in the above method embodiment. The processor can be configured to execute the program in the storage device, which includes but is not limited to a program for executing the method for suppressing circulating current in an energy storage system in the above method embodiment. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The control device can be a control device device formed by various electronic devices.

[0148] Furthermore, the present invention also provides a computer-readable storage medium. In a computer-readable storage medium embodiment according to the present invention, the computer-readable storage medium can be configured to store a program for executing the circulation suppression method in the energy storage system of the above-mentioned method embodiment, and the program can be loaded and run by the processor to implement the circulation suppression method in the above-mentioned energy storage system. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The computer-readable storage medium can be a storage device formed by various electronic devices. Optionally, the computer-readable storage medium in the embodiment of the present invention is a non-temporary computer-readable storage medium.

[0149] Further, it should be understood that since the setting of each module is only for illustrating the functional units of the device of the present invention, the physical devices corresponding to these modules may be the processor itself, or a part of the software in the processor, a part of the hardware, or a part of the combination of software and hardware. Therefore, the number of each module in the figure is only schematic.

[0150] It is understood by those skilled in the art that the modules in the device can be adaptively split or merged. Such splitting or merging of specific modules will not cause the technical solution to deviate from the principle of the present invention, and therefore, the technical solutions after splitting or merging will fall within the protection scope of the present invention.

[0151] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. An energy storage system, characterized in that: include: A plurality of energy storage units and a DC bus, wherein the energy storage unit comprises a battery cluster, a transformer and a first switch, the battery cluster is connected to the DC bus via the first switch, the battery clusters in different energy storage units are connected in parallel via the DC bus, the primary side of the transformer is connected to the battery cluster, the secondary side of the transformer is connected to the DC bus, wherein the transformer is used to transfer the energy of the battery cluster to the DC bus without passing through the first switch; The energy storage system further includes a second switch, the second switch being used to control the connection between the battery cluster and the transformer; The second switch includes: a first field effect transistor and a second field effect transistor, wherein the first end of the first field effect transistor is connected in series with the first end of the second field effect transistor, the second end of the first field effect transistor is connected to the primary side of the transformer, the second end of the second field effect transistor is connected to the first pole of the battery cluster, and the first field effect transistor and the second field effect transistor are connected in a back-to-back manner; And / or, the second switch includes: a third field effect transistor and a fourth field effect transistor, the first end of the third field effect transistor is connected in series with the first end of the fourth field effect transistor, the second end of the third field effect transistor is connected to the second end of the primary side of the transformer, the second end of the first field effect transistor is connected to the first end of the primary side of the transformer, the second end of the fourth field effect transistor is connected to the second pole of the battery cluster, and the third field effect transistor and the fourth field effect transistor are connected in a back-to-back manner.

2. The energy storage system according to claim 1, characterized in that: An inverter is provided on the primary side of the transformer, wherein the inverter converts the current output by the battery cluster during energy transfer into alternating current on the primary side of the transformer.

3. The energy storage system according to claim 1, characterized in that: The first field effect transistor and the second field effect transistor are both N-channel field effect transistors, and the first field effect transistor and the second field effect transistor both include a body diode, wherein the anode of the body diode is connected to the drain of the N-channel field effect transistor, and the cathode of the body diode is connected to the source of the N-channel field effect transistor.

4. The energy storage system according to any one of claims 1 to 3, characterized in that: The energy storage system also includes a first capacitor and a second capacitor, wherein the first end and the second end of the first capacitor are respectively connected to the two endpoints of the primary side of the transformer, and the first end and the second end of the second capacitor are respectively connected to the two endpoints of the secondary side of the transformer.

5. A method for suppressing circulating current in an energy storage system, characterized in that: The energy storage system includes a plurality of battery clusters and a power electronic conversion device, wherein the battery cluster is connected to a DC bus through a first switch, and the battery clusters are connected in parallel through the DC bus, wherein a first side of the power electronic conversion device is connected to the battery cluster, and a second side is connected to the DC bus, wherein the power electronic conversion device is used to transfer the energy of the battery cluster to the DC bus without passing through the first switch, and the method includes: obtaining an initial voltage of the battery cluster; Based on the initial voltage of the battery cluster, energy transfer is performed through the power electronic conversion device until the voltage of the battery cluster of the energy transfer recipient reaches a preset threshold, and the energy transfer is stopped; The power electronic conversion device comprises a transformer, the primary side of the transformer is the first side of the power electronic conversion device, and the secondary side of the transformer is the second side of the power electronic conversion device; The energy storage system further includes a second switch, the second switch being used to control the connection between the battery cluster and the power electronic conversion device; The second switch includes: a first field effect transistor and a second field effect transistor, wherein the first end of the first field effect transistor is connected in series with the first end of the second field effect transistor, the second end of the first field effect transistor is connected to the primary side of the transformer, the second end of the second field effect transistor is connected to the first pole of the battery cluster, and the first field effect transistor and the second field effect transistor are connected in a back-to-back manner; And / or, the second switch includes: a third field effect transistor and a fourth field effect transistor, the first end of the third field effect transistor is connected in series with the first end of the fourth field effect transistor, the second end of the third field effect transistor is connected to the second end of the primary side of the transformer, the second end of the first field effect transistor is connected to the first end of the primary side of the transformer, the second end of the fourth field effect transistor is connected to the second pole of the battery cluster, and the third field effect transistor and the fourth field effect transistor are connected in a back-to-back manner.

6. The method for suppressing circulating current in an energy storage system according to claim 5, characterized in that: Energy transfer is performed through the power electronic conversion device based on the initial voltage of the battery cluster, comprising: Control the first switch corresponding to the battery cluster of the energy transfer sender to be in an off state, the second switch corresponding to the battery cluster of the energy transfer sender to be in an on state, the first switch corresponding to the battery cluster of the energy transfer receiver to be in an on state, and the second switch corresponding to the battery cluster of the energy transfer receiver to be in an off state.

7. The method for suppressing circulating current in an energy storage system according to claim 5, characterized in that: acquiring initial voltages of the battery clusters and classifying the battery clusters into first-type battery clusters and second-type battery clusters based on the initial voltages of the battery clusters, wherein the initial voltages of the battery clusters in the first-type battery clusters are higher than the initial voltages of the battery clusters in the second-type battery clusters; The energy transfer is performed through the power electronic conversion device based on the initial voltage of the battery cluster until the voltage of the battery cluster of the energy transfer recipient reaches a preset threshold value, and the energy transfer is stopped, including: At least one first battery cluster in the first type of battery cluster is controlled to transfer energy to at least one second battery cluster in the second type of battery cluster through a power electronic conversion device until the voltage of the second battery cluster reaches a preset threshold, and the energy transfer is stopped.

8. The method for suppressing circulating current in an energy storage system according to any one of claims 5 to 7, characterized in that: An inverter is provided on the primary side of the transformer, wherein the inverter converts the current output by the battery cluster during energy transfer into alternating current on the primary side of the transformer.

9. The method for suppressing circulating current in an energy storage system according to claim 8, characterized in that: The inverter is an electronic switch, which converts the current output by the battery cluster during energy transfer into alternating current on the primary side of the transformer, and includes: Get the current value on the DC bus; Based on the current value, at least the switching frequency or the switching duty cycle of the inverter is controlled to adjust the current value on the DC bus.

10. The method for suppressing circulating current in an energy storage system according to claim 9, characterized in that: The step of controlling at least the switching frequency or the switching duty cycle of the inverter based on the current value comprises: When the current value is greater than the current threshold, the duty cycle of the inverter is reduced; or, When the current value is greater than the current threshold, the switching frequency of the inverter is reduced.

11. The method for suppressing circulating current in an energy storage system according to claim 5, characterized in that: The method for obtaining the preset threshold value includes: Obtaining an initial voltage of a battery cluster in the energy storage system; Based on the initial voltage of the battery cluster in the energy storage system, an average voltage is obtained; The average voltage is used as a preset threshold.

12. The method for suppressing circulating current in an energy storage system according to claim 5, characterized in that: The method for obtaining the preset threshold value includes: Obtaining a voltage reduction curve of a battery cluster in the energy storage system; Determining a voltage reduction range of the battery cluster based on the voltage reduction curve; Taking the voltage reduction range of the battery cluster as a first constraint condition, combining the initial voltage and at least based on a first objective function, obtaining an optimized voltage of the corresponding battery cluster, wherein the first objective function minimizes the circulating energy loss of the energy storage system during external discharge; The optimized voltage of the corresponding battery cluster is used as the preset threshold of the corresponding battery cluster.

13. The method for suppressing circulating current in an energy storage system according to claim 12, characterized in that: The step of taking the voltage reduction range of the battery cluster as the first constraint condition, combining the initial voltage and at least based on the first objective function, obtaining the optimized voltage of the corresponding battery cluster includes: The voltage reduction range of the battery cluster is used as the first constraint condition, combined with the initial voltage and based on the first objective function and the second objective function to obtain the optimized voltage of the corresponding battery cluster, wherein the second objective function minimizes the voltage difference between the battery clusters during the external discharge of the energy storage system.

14. The method for suppressing circulating current in an energy storage system according to claim 13, characterized in that: The step of taking the voltage reduction range of the battery cluster as the first constraint condition, combining the initial voltage and based on the first objective function and the second objective function, obtaining the optimized voltage of the corresponding battery cluster includes: Assigning a preset first weight to the first objective function; Assigning a preset second weight to the second objective function; Adding the first objective function assigned a preset first weight to the second objective function assigned a preset second weight to obtain a third objective function; The voltage reduction range of the battery cluster is taken as the first constraint condition, and the initial voltage and the third objective function are combined to obtain the optimized voltage of the corresponding battery cluster.

15. The circulating current suppression method in an energy storage system according to any one of claims 12 to 14, wherein determining the voltage reduction range of the battery cluster based on the voltage reduction curve comprises: Adjust the obtained voltage reduction curve to a voltage reduction curve under the same load; The initial voltage of the battery cluster and the adjusted voltage reduction curve are input into the trained neural network model to obtain the voltage reduction range of the battery cluster.

16. A control device, comprising a processor and a storage device, wherein the storage device is suitable for storing a plurality of computer programs, characterized in that: The computer program is suitable for being loaded and run by the processor to execute the circulating current suppression method in the energy storage system according to any one of claims 5 to 15.

17. A computer-readable storage medium storing a plurality of computer programs, characterized in that: The computer program is suitable for being loaded and run by a processor to execute the circulating current suppression method in the energy storage system according to any one of claims 5 to 15.

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