An energy storage system and its control method

Abstract

The present application provides an energy storage system and a control method thereof. The energy storage system of the present application includes: a busbar, M additional DC buses, M DC / DC converters, N battery clusters and a controller. One end of each of the M DC / DC converters is connected to one of the M additional DC buses respectively, and the second ends of the M DC / DC converters are connected to the busbar; wherein, M is less than or equal to 0.5N, and M and N are positive integers greater than 1; the controller divides the N battery clusters into K groups of battery clusters based on the cluster-level power of the N battery clusters, and the absolute value of the difference in the cluster-level power between the battery clusters within each group of battery clusters is less than or equal to a first threshold; wherein, K is less than or equal to M, the first threshold is greater than or equal to 0, and the cluster-level power is the sum of the state of charge (SOC) of all the batteries on the battery cluster or the sum of the voltage values. The controller controls the K groups of battery clusters to be connected to different DC / DC converters through the additional DC buses and then connected to the busbar, and each DC / DC converter is connected to at most one group of battery clusters. After the N battery clusters are grouped into battery cluster groups in the present application, the battery clusters with relatively close cluster-level power are grouped together, and only one DC / DC converter is used to connect to it. Therefore, it is possible to reduce the internal circulation in the battery cluster group while reducing the use of DC / DC converters, which can save costs and has strong engineering applicability.

Description

Technical Field

[0001] The present application relates to an energy storage system and a control method thereof, in particular to an energy storage system and a control method thereof that can reduce circulating current and cost during the charging and discharging process. Background Art

[0002] An energy storage system can be used to provide electric energy or store electric energy. It usually includes multiple battery clusters. The multiple battery clusters are connected to a power converter PCS through a busbar, and the power converter PCS is connected to an external system. This external system is usually a power grid, and can also include a solar panel for charging the energy storage system, or a load consuming electric energy. Or the power converter PCS can also be connected to the solar panel and the load consuming electric energy at the same time; that is, the energy storage system can charge and discharge the external system.

[0003] However, during the normal operation of the energy storage system, the aging degrees of different battery clusters may be different, or the performance of the battery clusters at the time of factory may be inconsistent. Therefore, circulating current will be generated between different battery clusters through the busbar, affecting the charging and discharging efficiency of the energy storage system for the external system. For this problem, the current common solutions are as Figure 1 shown, each battery cluster is connected to the busbar after passing through a DC / DC converter. Through the adjustment of the DC / DC converter, the charges between the battery clusters can tend to be balanced. However, such a setting method will result in a high cost.

[0004] For the above technical problems, no better solution has been proposed yet that can solve the circulating current problem of the energy storage system while taking into account the cost problem. Summary of the Invention

[0005] The embodiments of the present application provide an energy storage system and a control method thereof, which are solutions that can reduce the circulating current of the energy storage system while reducing the cost.

[0006] According to one aspect of the embodiments of the present application, the present application provides a busbar; N battery clusters; M additional DC buses, and M DC / DC converters, wherein the first ends of the M DC / DC converters are respectively and correspondingly connected to the M additional DC buses; the second ends of the M DC / DC converters are connected to the busbar; wherein, M is less than or equal to 0.5N, and M and N are positive integers greater than 1; a controller, which divides the N battery clusters into K groups of battery cluster groups based on the cluster-level power of the N battery clusters, and the absolute value of the difference in the cluster-level power between the battery clusters within each group of the battery cluster groups is less than or equal to a first threshold; wherein, K is less than or equal to M, the first threshold is greater than or equal to 0, and the cluster-level power is the sum of the state of charge (SOC) of all the batteries on the battery cluster or the sum of the voltage values; the controller controls the K groups of battery cluster groups to be connected to different DC / DC converters through the additional DC buses and then connected to the busbar; and each DC / DC converter is connected to at most one group of the battery cluster groups.

[0007] In some embodiments of the present application, the energy storage system further includes: N first array switches, which are arranged corresponding to the N battery clusters one by one; each of the first array switches includes M first switches, the first ends of the M first switches are connected to the corresponding battery cluster, and the second ends of the M first switches are respectively connected to the M DC / DC converters.

[0008] In some embodiments of the present application, when the energy storage system is on standby, the controller re-groups the N battery clusters to form new battery cluster groups.

[0009] In some embodiments of the present application, when K is less than M, the controller selects K DC / DC converters from the M DC / DC converters based on a conventional charge and discharge strategy, and connects the K groups of battery cluster groups to the K DC / DC converters; the conventional charge and discharge strategy is: based on the number of times of use of each DC / DC converter among the M DC / DC converters, select the K DC / DC converters with the least number of times of use.

[0010] In some embodiments of the present application, the rated powers of the M DC / DC converters are different; the controller allocates DC / DC converters with different rated powers to the K groups of battery cluster groups according to the group-level maximum rechargeable amount or the group-level maximum dischargeable amount of the K groups of battery cluster groups.

[0011] In some embodiments of the present application, when charging, the controller connects the battery cluster group with a larger group-level maximum rechargeable amount to a DC / DC converter with a larger rated power, and when discharging, the controller connects the battery cluster group with a larger group-level maximum dischargeable amount to a DC / DC converter with a larger rated power.

[0012] In some embodiments of the present application, when K is less than M and the power grid performs an emergency dispatch on the energy storage system, the controller selects K DC / DC converters from the M DC / DC converters based on an emergency charge and discharge strategy, and connects K battery cluster groups to the K DC / DC converters, where the emergency charge and discharge strategy is: select the K DC / DC converters with the largest rated power from the M DC / DC converters.

[0013] In some embodiments of the present application, if K after grouping is greater than M, the controller gradually increases the first threshold until the updated K is less than or equal to M; if K is still greater than M when the first threshold reaches the set maximum first threshold, then the controller disconnects K - M battery cluster groups from the DC / DC converter under the condition of meeting the charge and discharge power of the energy storage system.

[0014] On the other hand, the present application provides a control method based on the above energy storage system. The controller includes a cluster-level management unit BCMU of the N battery clusters and a battery stack management unit BAMU; the control method includes the following steps:

[0015] Step 1: The cluster-level management unit BCMU of the battery cluster collects the cluster-level power of the corresponding battery cluster and sends it to the battery stack management unit BAMU.

[0016] Step 2: The battery stack management unit BAMU groups the N battery clusters based on the cluster-level power of the N battery clusters to obtain K battery cluster groups, and makes the absolute value of the difference in the cluster-level power between the battery clusters within each battery cluster group less than the first threshold, where K is less than or equal to M.

[0017] Step 3: The battery stack management unit BAMU controls the K battery cluster groups to be connected to different DC / DC converters through the additional DC bus and then connected to the busbar; and each DC / DC converter is connected to at most one battery cluster group.

[0018] On the other hand, the present application provides a computer-readable storage medium storing a control program for controlling an energy storage system. The control program can be executed by at least one processor to enable the at least one processor to execute the steps of the above control method.

[0019] In the embodiments of the present application, the controller of the energy storage system groups N battery clusters to form K battery cluster groups. The cluster-level power between the battery clusters within each battery cluster group is less than the first threshold. The K battery cluster groups are connected to different DC / DC converters through an additional DC bus and then connected to the busbar. And each DC / DC converter is connected to at most one group of battery cluster groups. With such a setting, the battery clusters with relatively close cluster-level power are placed in one group. Therefore, the circulating current within the battery cluster group can be reduced. And each group of battery cluster groups only uses one DC / DC converter. Therefore, while reducing the circulating current within the battery cluster group, the use of DC / DC converters can also be reduced. And the battery cluster groups are all connected to the busbar through DC / DC converters, so that the circulating current between the battery cluster groups is small and can even be ignored. Therefore, the solution of the present application can take into account the cost issue while reducing the overall circulating current of the energy storage system. Description of the Drawings

[0020] To more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content shown in these drawings. The drawings described here are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the protection scope of the present application. In the drawings:

[0021] Figure 1 is a schematic diagram of an energy storage system according to the related art;

[0022] Figure 2 is a schematic diagram of an energy storage system according to an embodiment of the present application;

[0023] Figure 3 is a schematic diagram after grouping the energy storage system according to an embodiment of the present application;

[0024] Figure 4 is a flowchart of the control method of the energy storage system according to an embodiment of the present application.

[0025] Explanation of the Reference Numerals in the Drawings:

[0026] Energy storage system 1; Battery cluster 11; DC / DC converter 12; Busbar 13; Power converter PCS 14; First array switch 15; Additional DC bus 16; Controller 17; Battery cluster group 18. Detailed Embodiments

[0027] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0029] The realization of the purpose of this application, functional features, and advantages will be further described with reference to the embodiments and the accompanying drawings.

[0030] As Figure 1 shown in the energy storage system, a plurality of battery clusters 11 are provided in the energy storage system 1. Each battery cluster 11 is connected to the busbar 13 through a DC / DC converter 12. The busbar 13 is connected to the power converter PCS 14, and the power converter PCS 14 is connected to an external system. The external system is usually a power grid and may include a solar panel for charging the energy storage system 1, or a load consuming electric energy, or the power converter PCS 14 may also be connected to the solar panel and the load consuming electric energy at the same time, that is, the energy storage system 1 can charge and discharge the external system. In this energy storage system 1, the setting of DC / DC can prevent the formation of circulating current. However, a DC / DC converter 12 is correspondingly provided for each battery cluster 11. Such a setting method increases the extra and costly DC / DC converters, increasing the cost. For example, especially for large-scale photovoltaic power plants or power grid systems, due to the large number of battery clusters 11, a correspondingly large number of DC / DC converters 12 need to be provided, which will increase the cost of building the entire energy storage system 1.

[0031] To solve the above problems, this application provides an energy storage system 1 that can reduce the formation of circulating current and save costs at the same time. In some embodiments, as Figure 2 、 3As shown in the figure, the energy storage system 1 includes a busbar 13, M additional DC buses 16, M DC / DC converters 12, and N battery clusters 11, where M is less than or equal to 0.5N, and M and N are positive integers greater than 1; the first ends of the M DC / DC converters 12 are correspondingly connected to the M additional DC buses 16, and the second ends of the M DC / DC converters 12 are connected to the busbar 13, that is, one DC / DC converter 12 is provided on each additional DC bus 16, and the M DC / DC converters 12 are all connected to the busbar 13;

[0032] Among them, in this application, the number M of the DC / DC converters is set to be less than or equal to half of the number N of the battery clusters, that is, 0.5N. This is mainly by statistically analyzing the difference distribution of the cluster-level power among the battery clusters in the existing energy storage system and comprehensively setting the first threshold, and selecting M less than or equal to 0.5N. This setting method of this application compared with Figure 1 the related technologies in it can save at least half of the DC / DC converters 12.

[0033] The energy storage system 1 further includes a controller 17. The controller 17 divides the N battery clusters 11 into K battery cluster groups 18 based on the cluster-level power of the N battery clusters 11, and the absolute value of the difference in the cluster-level power between the battery clusters 11 within the battery cluster group 18 is less than or equal to the first threshold, where K is less than or equal to M, and the first threshold is greater than or equal to 0; the cluster-level power refers to the sum of the battery charge SOCs of all the batteries on the battery cluster 11 or the sum of the voltage values of all the batteries on the battery cluster 11.

[0034] In practical applications, a relatively small circulating current will not have too much impact on the energy storage system 1. Therefore, during the actual application process, a relatively small circulating current is allowed to exist. Correspondingly, the absolute value of the difference in cluster-level power among the individual battery clusters 11 of the battery cluster group 18 is allowed to be within a certain range. Controlling the absolute value of the difference in cluster-level power among the individual battery clusters 11 of the battery cluster group 18 within a certain range is to prevent the circulating current inside the battery cluster group 18 from being too large and having too much impact on the energy storage system. Therefore, it can be understood that the smaller the absolute value of the difference in cluster-level power among the individual battery clusters 11 of the battery cluster group 18, the smaller the circulating current generated inside the battery cluster group 18. At this time, a balance needs to be obtained between the magnitude of the circulating current and the number of DC / DC converters 12 used (i.e., cost). Therefore, in practical applications, according to the maximum acceptable circulating current, the maximum allowable value of the absolute value of the difference in cluster-level power among the individual battery clusters 11 within the battery cluster group 18 is obtained, and this value is set as the maximum first threshold. Therefore, usually the first threshold is selected as a value from 0 to the maximum first threshold. And in order to make the circulating current inside the battery cluster group 18 relatively small, the first threshold is usually set to be relatively small, that is, a relatively small value is taken from 0 to the maximum first threshold. Correspondingly, the number of DC / DC converters used will also be more, and the DC / DC converters 12 already set in the energy storage system 1 can be fully utilized.

[0035] Therefore, it can be understood that battery clusters 11 with more closely similar cluster-level power will be grouped together, so that the circulating current within the same battery cluster group 18 can be reduced. The controller 17 controls the K battery cluster groups 18 to be connected to different DC / DC converters 12 through the additional DC bus 16 and then connected to the busbar 13, and at most one battery cluster group 18 is connected to each additional DC bus 16 (which can also be said to each DC / DC converter 12). The energy storage system 1 can avoid the circulating current between different battery cluster groups 18 through different DC / DC converters 12.

[0036] In this application, since the circulating current inside each battery cluster group 18 has been reduced through the grouping method, and the circulating current between the battery cluster groups 18 is avoided through the voltage transformation of the DC / DC converters 12, therefore, the overall circulating current of the energy storage system 1 has been controlled and reduced through the above grouping and the setting of the DC / DC converters 12. At the same time, the use of the DC / DC converters 12 has been reduced, making it more applicable to engineering practice.

[0037] Specifically, in one embodiment, as Figure 3 shown, N = 6, that is, it includes 6 battery clusters 11, and M = 2, that is, it includes 2 DC / DC converters. For the sake of easy distinction, they are respectively denoted as battery clusters 11-1 to battery clusters 11-6; the DC / DC converters are respectively denoted as 12-1 to 12-2.

[0038] The cluster-level voltage of the battery cluster 11-1 is 666V;

[0039] The cluster level voltage of battery cluster 11-2 is 665V;

[0040] The cluster level voltage of battery cluster 11-3 is 665V;

[0041] The cluster level voltage of battery cluster 11-4 is 661V;

[0042] The cluster level voltage of battery cluster 11-5 is 662V;

[0043] The cluster level voltage of the battery cluster 11 - 6 is 661V.

[0044] When the value of the first threshold is 2, battery clusters 11-1 to 11-3 form a group to form a first battery cluster group 18, and battery clusters 11-4 to 11-6 form a group to form a second battery cluster group 18. The first battery cluster group 18 is connected to the DC / DC converter 12-1, and the second battery cluster group is connected to the DC / DC converter 12-2. In this way, the absolute value of the difference between the cluster-level charges of the battery clusters 11 in the first battery cluster group 18 and the second battery cluster group 18 after grouping is controlled at 1V, and the resulting circulation is small. If the first threshold 2 is not used for restriction, battery clusters 11-1 and battery clusters 11-6 may be grouped together, and the absolute value of the difference between the cluster-level charges is 5V, and the resulting circulation is large. It can be seen that the former method of using thresholds to limit the grouping of battery cluster groups 18 is more beneficial to the energy storage system 1 than the latter method.

[0045] In some embodiments, see Figure 2 , Figure 3 As shown, in order to facilitate the controller 17 to realize the grouping of different battery clusters 11, that is, to realize the connection between the battery clusters 11 and the corresponding DC / DC converters 12, the energy storage system 1 also includes N first array switches 15, and the N first array switches 15 are arranged in a one-to-one correspondence with the N battery clusters 11 of the energy storage system 1, that is, each battery cluster 11 is correspondingly provided with a first array switch 15. Each first array switch includes M switches, the first ends of the M switches are connected to the corresponding battery clusters 11, and the second ends of the M switches are respectively connected to the M DC / DC converters 12. The controller 17 can control the conduction or disconnection of each switch in the first switch array 15, so that the battery clusters 11 corresponding to the first array switches 15 can be selectively connected to different DC / DC converters 12 according to the grouping situation.

[0046] Specifically, in one embodiment, Figure 3As shown, for example, when N = 6 and M = 2, the energy storage system 1 further includes six first array switches 15. These six switch arrays 15 are arranged in one-to-one correspondence with six battery clusters. Each first array switch 15 includes two switches. The first ends of the two switches are connected to the battery cluster 11, and the second ends of the two switches are respectively connected to the DC / DC converter 12-1 and the DC / DC converter 12-2.

[0047] Specifically, as Figure 3 shown, when the battery clusters 11-1 to 11-3 form a group of battery clusters 18 and need to be connected to the DC / DC converter 12-1, and the battery clusters 11-4 to 11-6 form another group of battery clusters 18 and need to be connected to the DC / DC converter 12-2, the controller 17 controls the switches connecting the battery clusters 11-1 to 11-3 to the DC / DC converter 12-1 to close, and the remaining switches (i.e., the other switch) to open. And the controller 17 controls the switches connecting the battery clusters 11-4 to 11-6 to the DC / DC converter 12-2 to close and the remaining switches (i.e., the other switch) to open.

[0048] In some embodiments, when the energy storage system 1 is on standby, the controller 17 regroupes the N battery clusters 11 to form new battery cluster groups 18. At this time, the number of new battery cluster groups 18 may be different from or the same as before. The controller 17 is connected to the busbar DC bus 13 through the additional DC bus 16 based on the grouping of the new battery cluster groups 18, thereby forming a new grouping connection method.

[0049] As the energy storage system 1 operates or its health state changes, the determined K groups of battery cluster groups 18 may not be suitable for the current energy storage system 1. If the grouping of the K battery cluster groups 18 is fixed for a long time, as the energy storage system 1 operates or its health state changes, the internal circulating current in the energy storage system 1 may exceed the acceptable range, resulting in low efficiency of the energy storage system 1. Therefore, it is necessary to regularly regroup the N battery clusters 11 to ensure that the internal circulating current in the energy storage system 1 remains within the acceptable range continuously. And in order not to affect the normal operation of the energy storage system 1, the time point for regrouping is set when the energy storage system 1 is on standby.

[0050] In some embodiments, when K is less than M, i.e., some of the DC / DC converters 12 are in an idle state; the controller 17 selects K DC / DC converters 12 from the M DC / DC converters 12 based on a conventional charge and discharge strategy, and connects K battery cluster groups 18 to the K DC / DC converters 12. The conventional charge and discharge strategy is: based on the usage times of each of the M DC / DC converters 12, select the K DC / DC converters 12 with the least usage times. Through this charge and discharge strategy, all the DC / DC converters 12 can be used evenly, rather than concentrating on using some DC / DC converters 12, so as to improve the overall service life of the M DC / DC converters 12 and further reduce costs.

[0051] In the actual application process, the larger the rated power of the DC / DC converter 12, the more expensive it is. In the prior art, as Figure 1 shown, DC / DC converters 12 with the same rated power are used. And in order to meet the power requirements of charge and discharge, usually each DC / DC converter 12 in the energy storage system 1 will select a DC / DC converter 12 with a larger power, resulting in an increase in cost. In the energy storage system 1 designed in the present invention, since the battery clusters 11 are connected to different DC / DC converters 12 in a grouped manner, thus forming K battery cluster groups 18, there are differences in the charge and discharge powers of different battery cluster groups 18. And the battery cluster groups 18 with small charge and discharge powers do not need to use DC / DC converters 12 with large rated powers.

[0052] For the above reasons, in some embodiments, in order to further solve the cost problem, the energy storage system 1 includes M DC / DC converters 12 with different rated powers, that is, not all use DC / DC converters 12 with large rated powers, but use DC / DC converters 12 with different rated powers; the controller 17 allocates DC / DC converters 12 with different rated powers to the K battery cluster groups 18 according to the maximum rechargeable amount or the group-level maximum dischargeable amount of the K battery cluster groups 18.

[0053] In one embodiment, the controller 17, according to the maximum rechargeable amount or the group-level maximum dischargeable amount of the K battery cluster groups 18, during discharge, the controller evaluates the maximum dischargeable amount of each battery cluster group 18, that is, the remaining power, and connects the battery cluster group with a larger group-level maximum dischargeable amount to a DC / DC converter with a larger rated power. During charging, the controller evaluates the maximum rechargeable amount of each battery cluster group 18, that is, the power required from the current state to full charge, and connects the battery cluster group 18 with a larger group-level maximum rechargeable amount to a DC / DC converter with a larger rated power. The group-level maximum charge amount or the group-level maximum discharge amount refers to the sum of the maximum charge amounts or the maximum discharge amounts of all the battery clusters 11 in the battery cluster group 18.

[0054] It should be noted that:

[0055] When the energy storage system 1 discharges, since the larger the maximum group-level discharge capacity, the more power the battery cluster group 18 can provide compared to other battery cluster groups 18. Then, the rated power of the DC / DC converter 12 allocated to the battery cluster group 18 should be greater. Similarly, the smaller the maximum group-level discharge capacity, the less power the battery cluster group 18 can provide compared to other battery clusters 18. Therefore, the rated power of the DC / DC converter 12 allocated to the battery cluster group 18 should be smaller.

[0056] When the energy storage system 1 charges, since the larger the maximum group-level charge capacity, the more charge the battery cluster group 18 can store compared to other battery cluster groups 18. Then, the rated power of the DC / DC converter 12 allocated to the battery cluster group 18 should be greater. Similarly, the smaller the maximum group-level charge capacity, the less power the battery cluster group 18 needs compared to other battery cluster groups 18. Therefore, the rated power of the DC / DC converter 12 allocated to the battery cluster group 18 should be smaller.

[0057] The above adjustment and scheduling method can help each battery cluster group 18 gradually approach charge balance during the charge and discharge process in groups. That is, during the charging process, the battery cluster group 18 with a smaller maximum group-level charge capacity charges less, and the battery cluster group 18 with a larger maximum group-level charge capacity charges more. During the discharging process, the battery cluster group 18 with a larger maximum group-level discharge capacity discharges more, and the battery cluster group 18 with a smaller maximum group-level discharge capacity discharges less.

[0058] Therefore, when the energy storage system 1 is to discharge, the controller 17 connects the battery cluster group 18 with a larger maximum group-level discharge capacity to the DC / DC converter 12 with a larger rated power; when the energy storage system 1 is to charge, the battery cluster group 18 with a larger maximum group-level charge capacity is connected to the DC / DC converter 12 with a larger rated power.

[0059] In some embodiments, the controller 17 groups the battery clusters to obtain K battery cluster groups 18.

[0060] When K is less than M and the power grid performs emergency dispatching on the energy storage system 1, the controller 17 selects K DC / DC converters 12 from the M DC / DC converters 12 based on the emergency charge and discharge strategy, and connects K battery cluster groups 18 to the K DC / DC converters 12. Among them, the emergency charge and discharge strategy is: select the K DC / DC converters 12 with the largest rated power from the M DC / DC converters 12. That is, when emergency dispatching is required, the controller 17 selects the K DC / DC converters 12 with the largest rated power and allocates them to the K battery cluster groups 18, so that the N battery clusters 11 included in the K battery cluster groups 18 can be charged and discharged with higher efficiency. With such a setting, it can be ensured that the DC / DC converters 12 with larger rated power can be used, thereby increasing the charge and discharge efficiency.

[0061] In some embodiments, if K after grouping is greater than M, that is, the number of groups into which the controller 17 groups the N battery clusters 11 is more than the number of DC / DC converters 12, it will cause some battery cluster groups 18 to have no corresponding DC / DC converter 12 to connect. At this time, the controller 17 gradually increases the first threshold until the updated K is less than or equal to M, so as to ensure that all battery cluster groups 18 can be connected to a DC / DC converter 12. At this time, it can be ensured that the internal circulating current of the energy storage system 1 meets the requirements under the setting of a certain number of DC / DC converters 12.

[0062] If when the first threshold reaches the set maximum first threshold, K is still greater than M, then under the condition of meeting the charge and discharge power of the energy storage system 1, the controller 17 disconnects K - M battery cluster groups 18 from the energy storage system 1. That is to say, as long as the remaining M battery cluster groups can ensure the charge and discharge power, any K - M groups of battery cluster groups 18 can be selected not to be connected to any DC / DC connector 12 to ensure the charge and discharge power requirements of the energy storage system 1 and the circulating current meets the requirements. And when the energy storage system 1 is on standby, the controller 17 can also regroup the battery cluster groups 18 that are not connected to any DC / DC connector 12 by re - grouping and execute the above - mentioned grouping method.

[0063] According to the above - mentioned embodiments of the present application, a control method based on the above - mentioned energy storage system is provided.

[0064] Figure 4 It is a control method of an energy storage system according to an embodiment of the present application, as Figure 4 shown,

[0065] The controller 17 includes a cluster - level management unit BCMU for N battery clusters and a battery stack management unit BAMU; the cluster - level management unit BCMU is used to monitor and manage each battery cluster, and the battery stack management unit BAMU is used to collect various information of the battery clusters uploaded by the BCMU and perform analysis and management.

[0066] The control method includes the following steps:

[0067] Step 1: The cluster-level management unit BCMU of the battery cluster collects the cluster-level power of the corresponding battery cluster and sends it to the battery stack management unit BAMU;

[0068] Step 2: Based on the cluster-level powers of the N battery clusters, the battery stack management unit BAMU groups the N battery clusters to obtain K battery cluster groups, and makes the absolute value of the difference in the cluster-level powers between the battery clusters within the battery cluster group less than a first threshold, where K is less than or equal to M;

[0069] Step 3: The battery stack management unit BAMU controls the K groups of battery cluster groups to be connected to different DC / DC converters through an additional DC bus and then connected to the busbar; and each DC / DC converter is connected to at most one group of battery cluster groups.

[0070] In the control method of this application, the cluster-level management unit BCMU of the battery cluster and the battery stack management unit BAMU are used as the controller 17 respectively to complete different matters, thereby realizing the allocation of the battery clusters of the energy storage system 1, reducing the circulating current while also reducing the cost.

[0071] According to the above control method of this application, this application also includes a computer-readable storage medium storing a control program for controlling the energy storage system, and the control program can be executed by at least one processor to enable the at least one processor to execute the steps of the above control method.

[0072] Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The aforementioned storage medium includes: USB flash drives, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), mobile hard disks, magnetic disks, or optical discs, etc., which can store program codes.

[0073] The above are only the preferred embodiments of this application. It should be noted that for those of ordinary skill in the art, without departing from the principle of this application and on the premise that the technical solutions do not conflict, different embodiments can be combined with each other, and the combined technical solutions should also be regarded as the protection scope of this application. And the above embodiments are only the preferred embodiments of this application, and do not limit the scope of rights of this application accordingly.

Claims

1. An energy storage system, characterized in that, it includes: a busbar, the busbar is connected to 1 PCS; N battery clusters; M additional DC busbars, M DC / DC converters, and the first ends of the M DC / DC converters are connected to the M additional DC busbars in a one-to-one correspondence; the second ends of the M DC / DC converters are connected to the busbar; where M is less than or equal to 0.5N, and M and N are positive integers greater than 1; a controller, when the energy storage system is on standby, the controller regroupes the N battery clusters to form new battery cluster groups; the controller divides the N battery clusters into K battery cluster groups based on the cluster-level power of the N battery clusters, and the absolute value of the difference in cluster-level power between the battery clusters within each battery cluster group is less than or equal to a first threshold; where K is less than or equal to M, the first threshold is greater than or equal to 0, and the cluster-level power is the sum of the state of charge (SOC) of all the batteries on the battery cluster or the sum of the voltage values; the controller controls the K battery cluster groups to be connected to different DC / DC converters through the additional DC busbars and then connected to the busbar; and each DC / DC converter is connected to at most one battery cluster group; wherein, the rated powers of the M DC / DC converters are different; the controller allocates DC / DC converters with different rated powers to the K battery cluster groups according to the group-level maximum chargeable amount or group-level maximum dischargeable amount of the K battery cluster groups; when charging, the controller connects the battery cluster group with a larger group-level maximum chargeable amount to the DC / DC converter with a larger rated power, and when discharging, the controller connects the battery cluster group with a larger group-level maximum dischargeable amount to the DC / DC converter with a larger rated power.

2. The energy storage system according to claim 1, characterized in that, it further includes: N first array switches, the N first array switches are arranged in one-to-one correspondence with the N battery clusters; each of the first array switches includes M first switches, the first ends of the M first switches are connected to the corresponding battery cluster, and the second ends of the M first switches are respectively connected to the M DC / DC converters.

3. The energy storage system according to claim 1, characterized in that, when K is less than M, the controller selects K DC / DC converters from the M DC / DC converters based on a conventional charge and discharge strategy, and connects the K battery cluster groups to the K DC / DC converters; the conventional charge and discharge strategy is: based on the usage times of each DC / DC converter among the M DC / DC converters, select the K with the least usage times.

4. The energy storage system according to claim 1, characterized in that, When K is less than M and the power grid performs emergency dispatching on the energy storage system, the controller selects K DC / DC converters from the M DC / DC converters based on an emergency charge and discharge strategy, and connects K battery cluster groups to the K DC / DC converters, where the emergency charge and discharge strategy is: select the K DC / DC converters with the largest rated power from the M DC / DC converters.

5. The energy storage system according to claim 1, characterized in that if K after grouping is greater than M, the controller gradually increases the first threshold until the updated K is less than or equal to M; if K is still greater than M when the first threshold reaches the set maximum first threshold, then the controller disconnects K - M battery cluster groups from the DC / DC converter when the charge and discharge power of the energy storage system is satisfied.

6. The control method of the energy storage system according to any one of claims 1 - 5, characterized in that the controller includes a cluster - level management unit BCMU of the N battery clusters and a battery stack management unit BAMU; the control method includes the following steps: Step 1: The cluster - level management unit BCMU of the battery cluster collects the cluster - level power of the corresponding battery cluster and sends it to the battery stack management unit BAMU; Step 2: The battery stack management unit BAMU groups the N battery clusters based on the cluster - level power of the N battery clusters to obtain K battery cluster groups, and makes the absolute value of the difference in cluster - level power between the battery clusters within each battery cluster group less than the first threshold, where K is less than or equal to M; Step 3: The battery stack management unit BAMU controls the K battery cluster groups to be connected to different DC / DC converters through the additional DC bus and then connected to the busbar; and each DC / DC converter is connected to at most one battery cluster group; wherein, the rated powers of the M DC / DC converters are different; the controller assigns DC / DC converters with different rated powers to the K battery cluster groups according to the group - level maximum chargeable amount or group - level maximum dischargeable amount of the K battery cluster groups; Step 4: When charging, the controller connects the battery cluster group with a larger group - level maximum chargeable amount to the DC / DC converter with a larger rated power, and when discharging, the controller connects the battery cluster group with a larger group - level maximum dischargeable amount to the DC / DC converter with a larger rated power.

7. A computer - readable storage medium, characterized in that the computer - readable storage medium stores a control program for controlling the energy storage system, and the control program can be executed by at least one processor to enable the at least one processor to execute the steps of the control method according to claim 6.

Images