Energy storage system and method compatible with different ratios and different voltages

Abstract

The application relates to a compatible energy storage system and method of different magnifications and different voltages, which comprises n battery clusters and an SVB, each of the battery clusters comprises m battery modules connected in series; one end of each of the battery clusters is connected to a DC bus, the other end of each of the battery clusters is connected to the DC bus through the SVB, the n battery clusters are connected in parallel through the DC bus to form a battery stack, the SVB is used for realizing DC / DC conversion, and the battery stack is converted into alternating current through a PCS for being connected to a power grid. The application is compatible with different magnification (such as 0.5C / 1C) batteries, is convenient and flexible in capacity expansion; supports cluster balancing, reduces parallel capacity loss, avoids energy loss caused by circulating current, supports mixed use of new and old batteries, enables phased deployment, effectively reduces initial cost; supports low-voltage compensation, makes the battery configuration of the energy storage system more flexible, is beneficial to reducing battery capacity over-provisioning, and indirectly reduces the cost of the energy storage system.

Description

Technical Field

[0001] This invention relates to an energy storage system and method compatible with different rates and voltages, and pertains to the field of energy storage technology. Background Technology

[0002] With the rapid development of new energy sources, their integration has become a critical issue, highlighting the increasing importance of energy storage systems as a key component. Containerized energy storage systems, characterized by their small footprint, convenient installation and transportation, short construction period, strong environmental adaptability, high integration, and flexible expansion capabilities, significantly reduce the construction cycle and save project costs for new energy power plants, making them increasingly common in such projects. However, the cost of containerized energy storage systems is a key constraint for companies seeking to promote them in the market. While energy storage technology has made significant progress over the years, shortcomings remain in refined energy management, including low system efficiency and short lifespan, all of which indirectly increase economic costs.

[0003] Most existing technologies employ the approach of connecting multiple battery clusters in parallel to form a battery stack, which is then centrally connected to a power storage converter (PCS). However, inconsistencies in lithium-ion battery cell manufacturing and significant temperature differences during long-term operation further exacerbate internal resistance variations, intensifying the internal friction of the energy storage system. This "weakest link" effect also significantly shortens the lifespan of the energy storage system. Existing centralized battery stacks, such as... Figure 1 As shown, DC BUS represents the DC bus, n represents the number of battery clusters, and m represents the number of battery modules in each battery cluster. M battery modules are connected in series to form a battery cluster, and n battery clusters are connected in parallel through the DC bus to form a battery stack, which is then converted into AC power by the PCS and connected to the power grid.

[0004] The existing centralized battery stack implementation has the following drawbacks, mainly including: 1) Due to the inconsistency of lithium battery cells, direct parallel connection of battery clusters will lead to capacity mismatch. Due to the barrel effect, the usable capacity of the battery stack will be lower than expected, and the performance of the energy storage battery cannot be fully utilized. Therefore, it is often necessary to over-produce the energy storage battery to meet the performance requirements after aging, which increases the economic cost significantly; 2) The inconsistency of battery internal resistance will lead to inter-cluster circulating current and internal loss, reducing the charging and discharging efficiency of the energy storage system; 3) Cells with higher internal resistance generate more heat during operation and operate in a harsher temperature environment, which will accelerate the aging of the cells and fall into a vicious cycle. Due to the barrel effect, the lifespan of the energy storage system will be significantly shortened; 4) The battery stack is composed of battery modules connected in series and parallel. Sometimes, when the number of modules in series in the battery cluster is determined according to the actual required power, it is found that the minimum voltage of the battery cluster is lower than the DC operating voltage range of the PCS, and the voltage difference is not large. However, adding one more module to each cluster to meet the cluster voltage requirements will lead to battery stack capacity over-produce, increasing the system cost. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide an energy storage system and method that is compatible with different rates and voltages, capable of supporting inter-cluster equalization, avoiding capacity loss caused by circulating current, effectively reducing the cost of energy storage systems, and improving the lifespan of energy storage systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides an energy storage system compatible with different rates and voltages. The system includes n battery clusters and an SVB. Each battery cluster includes m battery modules connected in series. One end of each battery cluster is connected to the positive or negative terminal of a DC bus, and the other end of each battery cluster is connected to the negative or positive terminal of the DC bus via the SVB. The n battery clusters are connected in parallel via the DC bus to form a battery stack. The SVB is used to realize DC / DC conversion.

[0008] Furthermore, each SVB is equipped with more than one output interface and supports parallel expansion.

[0009] Furthermore, depending on the multiplier, any one of the battery clusters is connected in series or in parallel to the output interface of the SVB; or, two or more of the battery clusters are connected in series to multiple output interfaces of the SVB.

[0010] Furthermore, the SVB is also equipped with a controller unit, which communicates with the BMS via a communication interface.

[0011] Furthermore, the SVB includes two topologies:

[0012] The first topology: The SVB uses two dual-winding isolation transformers to achieve independent control between the two branches. The input side draws power from different places, and the input side in1, input side in2, and output side out1 and output side out2 are all used in parallel to achieve capacity expansion.

[0013] The second topology: The SVB uses a three-winding isolation transformer with one input and two outputs. The input side is one channel, which is directly powered by the DC BUS. The two outputs are independently controlled, and the outputs out1 and out2 are used in parallel to achieve capacity expansion.

[0014] Secondly, the present invention also provides an inter-cluster equalization method compatible with energy storage systems of different rates and voltages, comprising the following steps:

[0015] The energy storage system receives the dispatched power P;

[0016] The BMS calculates the total DC current Ia = P / U based on the DC bus voltage U.

[0017] BMS is based on the SOC of the nth cluster. n and SOH n Calculate the discharge current distribution coefficient DSOXn and the charging current distribution coefficient CSOXn for the nth cluster:

[0018] Determine whether the dispatch power P is a discharge. If it is, set the real-time current allocation coefficient SOXn = DSOXn for the nth cluster. If not, set the real-time current allocation coefficient SOXn = CSOXn for the nth cluster.

[0019] BMS calculates the output current In of the nth cluster;

[0020] The BMS controls the voltage value of the SVB to change the current value of the nth cluster, so that it outputs power according to the calculated current value, thus completing the balance between battery clusters.

[0021] Furthermore, the discharge current allocation coefficient DSOXn and the charging current allocation coefficient CSOXn of the nth cluster are:

[0022] DSOXn = SOCn * SOHn;

[0023] CSOXn=(1-SOCn)*SOHn;

[0024] Where SOCn is the remaining battery capacity percentage of the nth cluster, and SOHn is the battery health status percentage of the nth cluster.

[0025] Furthermore, the BMS calculates the output current In of the nth cluster as In = SOXn / (SOX1 + SOX2 + ... + SOXn) * Ia.

[0026] Furthermore, when the k-th cluster cannot rely on the output current Ik, where k≤n, the SVB of the k-th cluster feeds back a signal to the BMS, and the BMS sends a signal to the SVBs of other clusters to raise the voltage of the SVBs of other clusters; or, when the k-th cluster cannot rely on the output current Ik, where k≤n, the SVB of the k-th cluster draws power from the outside to compensate for the output current Ik.

[0027] Thirdly, the voltage compensation method for energy storage systems compatible with different rates and voltages provided by the present invention includes the following steps:

[0028] Get the initial real-time output voltage of the nth SVB cluster as Usvb(n), and the lowest real-time voltage of the battery cluster as Ubat;

[0029] Based on the minimum DC side voltage Umin of the PCS and the theoretical minimum voltage UL of the battery cluster, calculate the compensation voltage Ub and the real-time voltage difference ΔU;

[0030] Determine whether ΔU is less than Uc, where Uc is the voltage difference limit between the lowest voltage of the battery cluster and the lowest voltage of the DC side of the PCS. When the real-time voltage difference ΔU is less than Uc, voltage compensation is activated, raising the output voltage of all SVBs by a voltage compensation value Ub. Then the real-time output voltage of the nth SVB cluster is: Usvb(n) = Usvb(n) + Ub.

[0031] Furthermore, the compensation voltage Ub = Umin - UL; the real-time voltage difference ΔU = Ubat - Umin.

[0032] Because the present invention adopts the above technical solution, it has the following characteristics:

[0033] 1. The energy storage system provided by this invention is compatible with batteries of different rates (such as 0.5C / 1C), which facilitates flexible capacity expansion; it supports inter-cluster equalization, reduces parallel capacity loss, avoids energy loss caused by circulating current, supports the use of new and old batteries, enables phased deployment, and effectively reduces initial costs; it supports low voltage compensation, making the battery configuration of the energy storage system more flexible, which is conducive to reducing battery capacity over-provisioning and indirectly reducing the cost of the energy storage system.

[0034] 2. The energy storage system provided by this invention supports parallel expansion. An SVB (Series Voltage Equalizer) contains more than one output interface, and the output interfaces support parallel use. For example, an SVB contains two independent output interfaces, which can be connected to two battery clusters respectively. When the power of a single interface is insufficient, it supports the parallel use of two interfaces to achieve current expansion, thereby supporting batteries of different rates.

[0035] 3. After the energy storage system provided by the present invention connects the battery clusters in series with SVB, inter-cluster balancing can be achieved through an inter-cluster balancing strategy, and voltage compensation can be achieved when the battery clusters are at low voltage through a voltage compensation strategy.

[0036] 4. The energy storage system of this invention adds an SVB between clusters. By controlling the SVB, inter-cluster balancing is achieved, making full use of the capacity of the battery clusters. This effectively improves the usable capacity of the battery stack, fully utilizes the performance of the energy storage system, and reduces the cost of the energy storage system. Through the control of the SVB, inter-cluster decoupling is achieved, and each cluster can be controlled independently, with virtually no inter-cluster circulating current, reducing internal system losses and improving the system's charge and discharge efficiency. Through the SVB's inter-cluster balancing strategy, fine control of the charge and discharge current of different clusters is achieved. Battery clusters with higher internal resistance (more severely aged battery clusters) output less power (smaller charge and discharge current), while battery clusters with lower internal resistance (less severely aged battery clusters) output more power (larger charge and discharge current). This mitigates the aggravation of inconsistency between battery clusters, compensates for the weakest link in the bottleneck effect, and extends the life of the energy storage system. When the minimum voltage of a battery cluster is slightly lower than the minimum voltage requirement of the PCS DC side, voltage compensation can be performed on the battery cluster by connecting the SVB in series, so that the minimum voltage of the battery cluster is higher than the minimum voltage requirement of the PCS DC side, thereby achieving compatibility with the PCS.

[0037] In summary, this invention can be widely applied to energy storage systems. Attached Figure Description

[0038] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0039] Figure 1 This is a schematic diagram of a centralized battery stack structure in the prior art.

[0040] Figure 2 This is a schematic diagram of the battery stack structure according to an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the battery stack structure according to an embodiment of the present invention.

[0042] Figure 4 (a) and (b) are schematic diagrams of the SVB topology in an embodiment of the present invention.

[0043] Figure 5 This is a schematic diagram of an LLC resonant bidirectional full-bridge DC / DC structure according to an embodiment of the present invention.

[0044] Figure 6 This is a schematic diagram of the control flow of the inter-cluster balancing strategy according to an embodiment of the present invention.

[0045] Figure 7 This is a schematic diagram of the voltage compensation strategy control process according to an embodiment of the present invention. Detailed Implementation

[0046] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0047] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "above," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure.

[0048] This invention provides an energy storage system and method compatible with different rates and voltages. The system includes n battery clusters and an SVB (Self-Brain Controller). Each battery cluster includes m battery modules connected in series. One end of each battery cluster is connected to the positive or negative terminal of a DC bus, and the other end of each battery cluster is connected to the negative or positive terminal of the DC bus via the SVB. The n battery clusters are connected in parallel via the DC bus to form a battery stack. The SVB is used to achieve DC / DC conversion. The battery stack is converted to AC power by a PCS (Power Control System) for grid connection. The energy storage system provided by this invention is compatible with batteries of different rates (e.g., 0.5C / 1C), facilitating flexible capacity expansion; it supports inter-cluster balancing, reducing parallel capacity loss and avoiding energy loss due to circulating current; it supports the use of mixed new and old batteries, enabling phased deployment and effectively reducing initial costs; and it supports low-voltage compensation, making the battery configuration of the energy storage system more flexible, which helps reduce battery over-sizing and indirectly reduces the cost of the energy storage system.

[0049] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0050] like Figure 2As shown, the energy storage system compatible with different rates and voltages provided in this embodiment includes n battery clusters connected in parallel. Each battery cluster contains m battery modules connected in series, and each battery cluster is connected to an SVB and then to a DC bus to form a battery stack. The power is then converted to AC power by a PCS and connected to the power grid. It should be noted that the battery clusters in this embodiment do not include conventional control and protection devices such as contactors and fuses. There may be more than one contactor and fuse in the battery cluster circuit. These devices can be configured independently without being set in the SVB, or they can be set in the SVB. There is no limitation here, and they can be selected according to actual needs.

[0051] In a preferred embodiment, considering the flexibility of the application and to facilitate expansion, each SVB is equipped with more than one output interface and supports parallel expansion. One, two, or more output interfaces can be selected according to actual needs, and no limitation is made here.

[0052] Furthermore, depending on the battery rate, any battery cluster can be connected in series or parallel to the SVB's output interface; or, two or more battery clusters can be connected in series to multiple output interfaces of the SVB. Specifically, an SVB contains more than one output interface, and the output interfaces support parallel use. For example, an SVB may contain two independent output interfaces, which can be connected to two battery clusters respectively. When the power of a single interface is insufficient, two interfaces can be used in parallel to expand the current capacity, thereby supporting batteries of different rates. For example, when the SVB receives messages from two battery clusters and detects two high voltages on the high-voltage side, it can achieve group operation. The SVB's DC input circuit is not directly connected, and it enters a low-rate mode, such as... Figure 2 As shown; when SVB receives only one battery cluster message and the high-voltage side detects only one high voltage, it is considered that SVB is only connected to one cluster and can run in high-rate mode. The two originally independent access circuits of the SVB battery can be directly connected, which can improve the conversion efficiency of SVB under single-cluster high-power conditions. Figure 3 As shown.

[0053] Furthermore, such as Figure 2 As shown, this embodiment uses an SVB with two independent output interfaces as an example. The two independent output interfaces of the SVB are connected to two battery clusters respectively, specifically:

[0054] The SVB has two independent output interfaces, and each SVB output interface is connected in series to two battery clusters, for example... Figure 2 Battery cluster 1 and battery cluster 2 in the system support parallel use of two interfaces when the power of one output interface is insufficient, thereby expanding the current capacity and supporting batteries of different rates.

[0055] In a preferred embodiment, such as Figure 3 As shown, the SVB includes a controller unit, which can use a microcontroller or SPI. The controller unit communicates with the BMS (Battery Management System) via an RS485, RS232, or CAN interface.

[0056] In a preferred embodiment, the SVB is actually a DC / DC converter unit. The SVB's power input is directly drawn from the battery side or the DC bus side, and the SVB's output is directly connected in series with the battery pack's DC circuit. The SVB indirectly controls the charging and discharging current of the battery pack by controlling its output voltage. The SVB can have the following two topologies:

[0057] like Figure 4 The topology (a) shown uses two double-winding isolation transformers to achieve independent control between the two branches. The input side can draw power from different places. The input side in1, input side in2, and output side out1 and output side out2 can all be used in parallel to achieve capacity expansion.

[0058] like Figure 4 The topology (b) shown uses a three-winding isolation transformer for its SVB, with one input and two outputs. There is only one input, which can be directly powered by the DC bus. The two independent outputs can be controlled independently. Outputs out1 and out2 can be used in parallel to achieve capacity expansion.

[0059] Of course, if there are more than two output interfaces, a multi-winding isolation transformer can be used, which will not be elaborated here.

[0060] Furthermore, SVB's DC / DC topology can be implemented in various ways, generally using a two-stage topology transformation. For example, power conversion can be achieved using a Buck-Boost circuit + LLC circuit, such as... Figure 5 As shown, the SVB DC / DC topology in this embodiment is implemented using an LLC resonant bidirectional full-bridge DC / DC converter. This is just one example, and the implementation is not limited to this.

[0061] With the addition of SVB to the energy storage system, this embodiment can also achieve voltage compensation and inter-cluster equalization by controlling SVB, which will be explained in detail below.

[0062] After adding an SVB to the energy storage system, the SVB can perform voltage compensation, making the minimum voltage of the battery cluster higher than the minimum DC-side voltage requirement of the PCS, thereby achieving compatibility with the PCS. This embodiment provides a voltage compensation method for the energy storage system, including:

[0063] A1. Initially, the real-time output voltage of the nth SVB cluster is obtained as Usvb(n), and the lowest real-time voltage of the battery cluster is Ubat;

[0064] A2. Based on the minimum DC-side voltage Umin of the PCS and the theoretical minimum voltage UL of the battery cluster, calculate the compensation voltage and real-time voltage difference:

[0065] Compensation voltage Ub = Umin - UL

[0066] Real-time pressure difference ΔU = Ubat - Umin;

[0067] A3. Determine if ΔU is less than Uc. Uc is the voltage difference limit between the lowest voltage of the battery cluster and the lowest voltage of the PCS DC side. Uc is minimum to 0. Generally, considering a certain dynamic response margin, Uc can be 1 or other positive values, which can be set according to the actual situation. When the real-time voltage difference ΔU is less than Uc, the BMS starts voltage compensation, raising the SVB output voltage of all n clusters by a voltage compensation value Ub. Then, the real-time output voltage of the nth cluster SVB is: Usvb(n) = Usvb(n) + Ub. The voltage compensation value of SVB can be obtained from the positive and negative terminals of the battery cluster or from an external power supply.

[0068] In summary, battery stacks are composed of battery modules connected in series and parallel. Sometimes, when determining the number of modules in series for a battery cluster based on the actual required capacity, it is found that the minimum voltage of the battery cluster is lower than the DC operating voltage range of the PCS, and the voltage difference is not significant. Adding an extra module to each cluster to meet the voltage requirement would lead to over-sizing of the battery stack, increasing system costs. When the battery is at the end of its discharge phase, the voltage is low, and the battery cluster voltage may be lower than the DC operating voltage range of the PCS, causing the PCS to malfunction. After connecting the battery cluster in series with a SVB (Self-Voltage Module), the SVB can perform voltage compensation, ensuring that the minimum voltage of the battery cluster is higher than the minimum DC voltage requirement of the PCS, thus achieving compatibility with the PCS.

[0069] like Figure 6 As shown, this embodiment also provides an inter-cluster equalization method for energy storage systems, including:

[0070] S1, The energy storage system receives dispatch power P from the EMS;

[0071] S2 and BMS calculate the total DC current Ia = P / U based on the DC bus voltage U;

[0072] S3, BMS are based on the SOC of the nth cluster. n and SOH n Calculate the discharge current distribution coefficient DSOXn and the charging current distribution coefficient CSOXn for the nth cluster:

[0073] DSOXn = SOCn * SOHn

[0074] CSOXn=(1-SOCn)*SOHn;

[0075] Where SOCn is the remaining battery capacity percentage of the nth cluster, and SOHn is the battery health status percentage of the nth cluster;

[0076] S4. Determine whether the dispatch power P is discharging based on the dispatch power value of the energy storage system (the sign of the dispatch power value of the energy storage system determines whether it is charging or discharging; generally, a positive value of the dispatch power of the energy storage system represents discharging, and a negative value represents charging). If it is, set the real-time current allocation coefficient SOXn = DSOXn for the nth cluster; otherwise, set the real-time current allocation coefficient SOXn = CSOXn for the nth cluster.

[0077] S5 and BMS calculate the output current of the nth cluster as follows:

[0078] In=SOXn / (SOX1+SOX2+…+SOXn)*Ia;

[0079] S6 and BMS control the output current of the nth cluster SVB, so that the nth cluster outputs power according to the calculated current value, thus completing the balance between battery clusters.

[0080] Furthermore, when the k-th cluster cannot output current Ik, where k≤n, the SVB of the k-th cluster feeds back a signal to the BMS, and the BMS sends a signal to the SVBs of other clusters to raise the voltage of the SVBs of other clusters.

[0081] Specifically, upon receiving the current value calculated by the BMS, the SVB sends commands to the current control devices (such as switching transistors) of the battery cluster to control their operating state and thus control the cluster's output current. This can be achieved by actively raising or lowering the SVB voltage to change the current value of the battery cluster, reducing inter-cluster differences. When a single cluster voltage is high, the BMS controls the SVB to actively raise the voltage of that cluster, making its output voltage slightly higher than other clusters, thereby increasing the cluster's output and reducing inter-cluster differences. Conversely, when a single cluster voltage is low, the BMS controls the SVB to actively lower the voltage of that cluster, making its output voltage slightly lower than other clusters, thereby decreasing the cluster's output and reducing inter-cluster differences.

[0082] Furthermore, when the k-th cluster cannot rely on the output current Ik, where k≤n, the SVB of the k-th cluster draws power from an external power source to compensate for the output current Ik.

[0083] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In the description of this specification, references to terms such as "a preferred embodiment" and "furthermore" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the embodiments in this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions 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.

Claims

1. An energy storage system compatible with different rates and voltages, characterized in that, The system includes n battery clusters and SVBs, and each battery cluster includes m battery modules connected in series. One end of each battery cluster is connected to the positive or negative terminal of the DC bus, and the other end of each battery cluster is connected to the negative or positive terminal of the DC bus via the SVB. n battery clusters are connected in parallel via the DC bus to form a battery stack. The SVB is used to achieve DC / DC conversion. The voltage compensation process of the energy storage system is as follows: Get the initial real-time output voltage of the nth SVB cluster as Usvb(n), and the lowest real-time voltage of the battery cluster as Ubat; Based on the minimum DC side voltage Umin of the PCS and the theoretical minimum voltage UL of the battery cluster, calculate the compensation voltage Ub and the real-time voltage difference ΔU = Ubat - Umin; Determine whether ΔU is less than Uc, where Uc is the voltage difference limit between the lowest voltage of the battery cluster and the lowest voltage of the DC side of the PCS. When the real-time voltage difference ΔU is less than Uc, start voltage compensation and raise the output voltage of all SVBs by a voltage compensation value Ub. Then the real-time output voltage of the nth SVB cluster is: Usvb(n) = Usvb(n) + Ub.

2. The energy storage system compatible with different rates and voltages according to claim 1, characterized in that, Each SVB has one or more output interfaces and supports parallel expansion.

3. The energy storage system compatible with different rates and voltages according to claim 2, characterized in that, Depending on the multiplier, any one of the battery clusters is connected in series or in parallel to the output interface of the SVB; or, two or more of the battery clusters are connected in series to multiple output interfaces of the SVB.

4. The energy storage system compatible with different rates and voltages according to claim 1, characterized in that, The SVB is also equipped with a controller unit, which communicates with the BMS via a communication interface.

5. The energy storage system compatible with different rates and voltages according to claim 1, characterized in that, The SVB includes two topologies: The first topology: The SVB uses two dual-winding isolation transformers to achieve independent control between the two branches. The input side draws power from different places, and the input side in1, input side in2, and output side out1 and output side out2 are all used in parallel to achieve capacity expansion. The second topology: The SVB uses a three-winding isolation transformer with one input and two outputs. The input side is one channel, which is directly powered by the DC BUS. The two outputs are independently controlled, and the outputs out1 and out2 are used in parallel to achieve capacity expansion.

6. A cluster equalization method based on any one of claims 1 to 5 for energy storage systems compatible with different rates and voltages, characterized in that... include: The energy storage system receives the dispatched power P; The BMS calculates the total DC current Ia = P / U based on the DC bus voltage U. BMS is based on the SOC of the nth cluster. n and SOH n Calculate the discharge current allocation coefficient DSOXn and the charging current allocation coefficient CSOXn for the nth cluster: Determine whether the dispatch power P is discharging. If it is, set the real-time current allocation coefficient SOXn=DSOXn for the nth cluster. If not, set the real-time current allocation coefficient SOXn=CSOXn for the nth cluster. BMS calculates the output current In of the nth cluster; The BMS controls the voltage value of the SVB to change the current value of the nth cluster, so that it outputs power according to the calculated current value, thus completing the balance between battery clusters.

7. The inter-cluster equalization method according to claim 6, characterized in that, The discharge current allocation coefficient DSOXn and the charging current allocation coefficient CSOXn of the nth cluster: DSOXn = SOCn * SOHn; CSOXn=(1-SOCn)*SOHn; Where SOCn is the remaining battery capacity percentage of the nth cluster, and SOHn is the battery health status percentage of the nth cluster.

8. The inter-cluster equalization method according to claim 6 or 7, characterized in that, BMS calculates the output current In of the nth cluster as In = SOXn / (SOX1 + SOX2 + ... + SOXn) * Ia.

9. The inter-cluster equalization method according to claim 8, characterized in that, When the k-th cluster cannot respond to the output current Ik, where k≤n, the SVB of the k-th cluster feeds a signal to the BMS, and the BMS sends signals to the SVBs of other clusters, raising the voltage of the SVBs of other clusters; or, When the k-th cluster cannot be powered by the output current Ik, where k≤n, the SVB of the k-th cluster draws power from the outside to compensate for the output current Ik.

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