Energy storage system

Abstract

Provided in the present application is an energy storage system. The energy storage system comprises a battery cluster, which comprises a plurality of battery packs, a first battery pack protection circuit, a second battery pack protection circuit and a first protection circuit, wherein the plurality of battery packs are connected in series between a positive output end and a negative output end of the battery cluster, and the plurality of battery packs comprise a first battery pack and a second battery pack, which are respectively connected to the positive output end and the negative output end of the battery cluster. The first protection circuit is turned on when the voltage between an output end of the battery cluster and a reference ground is greater than a first voltage threshold value. The first battery pack protection circuit is turned on when the voltage between an output end of the first battery pack and the reference ground is greater than a second voltage threshold value, and the first voltage threshold value is greater than an output voltage of the battery cluster and less than the second voltage threshold value. The second battery pack protection circuit is turned on when the voltage between an output end of the second battery pack and the reference ground is greater than the second voltage threshold. Therefore, effective lightning protection can be realized when there is a lightning strike current at an output end of a battery cluster.

Description

Energy storage system

[0001] This application claims priority to Chinese Patent Application No. 202520526415.6, filed on March 24, 2025, with the invention entitled "Energy Storage System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of power supply technology, and more particularly to an energy storage system. Background Technology

[0003] With the large-scale application of energy storage systems, the DC side of the energy storage box (including multiple battery clusters) is connected to the DC side of the energy storage converter via cables. The length of the cables is generally at least 6m. In outdoor scenarios, the possibility of being struck by lightning is high. Problems such as failure and arcing caused by lightning strikes will occur. Therefore, it is particularly important to improve the reliability and safety of the energy storage system.

[0004] Currently, energy storage systems mainly employ the circuit structure shown in Figure 1 to achieve lightning protection. As shown in Figure 1, the energy storage converter in the energy storage system has an internal lightning protection circuit. In the event of a lightning strike between the output side of the battery cluster and the DC side of the energy storage converter, the voltage across the lightning protection circuit exceeds the conduction voltage threshold of the lightning protection circuit, causing the lightning protection circuit to conduct. This allows the lightning current to be discharged through the lightning protection circuit, thereby achieving lightning protection for the energy storage converter.

[0005] When a lightning strike occurs between the output side of the battery cluster and the DC side of the energy storage converter, part of the lightning current flows to the energy storage converter and the other part flows to the battery cluster. The solution of having a built-in lightning protection circuit in the energy storage converter can only protect the energy storage converter from lightning. Therefore, when a lightning strike occurs between the output side of the battery cluster and the DC side of the energy storage converter, the energy storage system shown in Figure 1 cannot effectively protect the battery cluster from lightning. Summary of the Invention

[0006] This application provides an energy storage system in which the battery clusters can achieve effective lightning protection when there is lightning current at their output terminals, thereby improving the safety and reliability of the energy storage system under severe lightning weather conditions.

[0007] In a first aspect, this application provides an energy storage system comprising a battery cluster, which includes multiple battery packs, a first battery pack protection circuit, a second battery pack protection circuit, and a first protection circuit. The battery cluster has an output terminal including a positive output terminal and a negative output terminal. The multiple battery packs are connected in series between the positive and negative output terminals of the battery cluster, and each battery pack includes a first battery pack and a second battery pack respectively connected to the positive and negative output terminals of the battery cluster. The first protection circuit is connected between the output terminal of the battery cluster and a reference ground, and is configured to be in a conducting state when the voltage between the output terminal of the battery cluster and the reference ground is greater than a first voltage threshold, wherein the first voltage threshold is greater than the output voltage of the battery cluster. The first battery pack protection circuit is connected between the output terminal of the first battery pack and the reference ground, and is configured to be in a conducting state when the voltage between the output terminal of the first battery pack and the reference ground is greater than a second voltage threshold, wherein the second voltage threshold is greater than the first voltage threshold. The second battery pack protection circuit is connected between the output terminal of the second battery pack and the reference ground, and is configured to be in a conducting state when the voltage between the output terminal of the second battery pack and the reference ground is greater than a second voltage threshold.

[0008] In this embodiment, when a lightning strike current is present at the output terminal of the battery cluster, if the voltage between the output terminal of the battery cluster and the reference ground exceeds a first voltage threshold, the first protection circuit is activated, thereby discharging most of the lightning strike current at the output terminal of the battery cluster to the reference ground. A small portion of the lightning strike current at the output terminal of the battery cluster flows to the first and second battery packs formed by connecting multiple battery packs in series. Two battery pack protection circuits (i.e., the first battery pack protection circuit and the second battery pack protection circuit) are respectively installed between the output terminals of the first and second battery packs and the reference ground. These circuits are activated when a lightning strike current is present at the output terminals of the first and second battery packs, thereby discharging the lightning strike current at the output terminals of the first and second battery packs to the reference ground and preventing the lightning strike current from further flowing to other battery packs besides the first and second battery packs. Therefore, the battery cluster can achieve effective lightning protection when a lightning strike current is present at its output terminal, thereby improving the safety and reliability of the energy storage system under severe lightning weather conditions.

[0009] In conjunction with the first aspect, in a first possible implementation, the first battery pack protection circuit is located inside the first battery pack, and the second battery pack protection circuit is located inside the second battery pack.

[0010] In this embodiment, the protection circuits of each battery pack are placed inside their respective connected battery packs, which can effectively utilize the existing internal space of the battery packs without increasing the volume of the battery clusters, thus facilitating the miniaturization design of the battery clusters.

[0011] In conjunction with the first aspect or the first possible implementation of the first aspect, in the second possible implementation, the plurality of battery packs includes an i-th battery pack, and the battery cluster includes an i-th battery pack protection circuit corresponding to the i-th battery pack, where 1 ≤ i ≤ n and n > 2, and n is the number of battery packs in the battery cluster. The i-th battery pack protection circuit is connected between the output terminal of the i-th battery pack and a reference ground, and is used to be in a conducting state when the voltage between the output terminal of the i-th battery pack and the reference ground is greater than a second voltage threshold.

[0012] In this embodiment, considering that the protection circuits of the two battery packs corresponding to the first and last battery packs may be abnormal, resulting in the failure of protection for the n battery packs in the battery cluster, a battery pack protection circuit corresponding to each battery pack is provided between the output terminal of each of the n battery packs and the reference ground to improve the reliability of the battery cluster when performing lightning protection.

[0013] In conjunction with the second possible implementation of the first aspect, in the third possible implementation, the protection circuit of the i-th battery pack is located inside the i-th battery pack.

[0014] In this embodiment, the protection circuits of each battery pack are placed inside their respective connected battery packs, which can effectively utilize the existing internal space of the battery packs without increasing the volume of the battery clusters, thus facilitating the miniaturization design of the battery clusters.

[0015] In a fourth possible embodiment, combining any of the first to third possible implementations of the first aspect, the first battery pack protection circuit includes two first protection units and a second protection unit. The output terminal of the first battery pack includes a positive output terminal and a negative output terminal. One end of one of the two first protection units is connected to the positive output terminal of the first battery pack, and one end of the other first protection unit is connected to the negative output terminal of the first battery pack. The other ends of the two first protection units are connected and then connected to a reference ground through the second protection unit. One first protection unit and the second protection unit are configured to be in a conducting state when the voltage between the positive output terminal of the first battery pack and the reference ground is greater than a second voltage threshold. The other first protection unit and the second protection unit are configured to be in a conducting state when the voltage between the negative output terminal of the first battery pack and the reference ground is greater than the second voltage threshold.

[0016] In this embodiment, the first battery pack protection circuit adopts a Y-connected protection circuit, which has a simple circuit structure and is easy to implement. In addition, the two first protection units share one second protection unit, which helps to reduce circuit costs.

[0017] In a fifth possible embodiment, in conjunction with any of the first to third possible implementations of the first aspect, the first battery pack protection circuit includes two first protection units and two second protection units, and the output terminals of the first battery pack include a positive output terminal and a negative output terminal. Specifically, one first protection unit and one second protection unit of the first battery pack protection circuit are connected in series between the positive output terminal of the first battery pack and a reference ground, and are configured to be in a conducting state when the voltage between the positive output terminal of the first battery pack and the reference ground exceeds a second voltage threshold. The other first protection unit and the other second protection unit of the first battery pack protection circuit are connected in series between the negative output terminal of the first battery pack and the reference ground, and are configured to be in a conducting state when the voltage between the negative output terminal of the first battery pack and the reference ground exceeds the second voltage threshold.

[0018] In this embodiment, the first battery pack protection circuit adopts a type II connection protection circuit. Since the protection branch between the positive output terminal of the first battery pack and the reference ground and the protection branch between the negative output terminal of the first battery pack and the reference ground are independent of each other, the other protection branch can still work normally when one of the two protection branches is abnormal, thereby improving the reliability of the first battery pack protection circuit.

[0019] In conjunction with the fourth or fifth possible implementation of the first aspect, in the sixth possible implementation, each of the first and second protection units includes a protection element, or at least two protection elements connected in series and / or in parallel, wherein the protection element includes a gas discharge tube, a varistor, or a transient suppression diode.

[0020] In this embodiment, the structure of each protection unit in the first battery pack protection circuit and the types of protection elements in each protection unit are diverse, which can improve the diversity of battery cluster structure and increase flexibility.

[0021] In conjunction with the first aspect to the sixth possible implementation, in the seventh possible implementation, the battery cluster further includes a cluster control box, and the first protection circuit is located inside the cluster control box.

[0022] In this embodiment, the first protection circuit is located inside the cluster control box, which can effectively utilize the existing internal space of the cluster control box, thus not increasing the volume of the battery cluster, which is beneficial to the miniaturization design of the battery cluster.

[0023] In conjunction with the first to seventh possible embodiments of the first aspect, in the eighth possible embodiment, the first protection circuit includes two third protection units and a fourth protection unit. One end of one of the two third protection units is connected to the positive output terminal of the battery cluster, and one end of the other third protection unit is connected to the negative output terminal of the battery cluster. The other ends of the two third protection units are connected and then connected to a reference ground via the fourth protection unit. One third protection unit and the fourth protection unit are configured to be in a conducting state when the voltage between the positive output terminal of the battery cluster and the reference ground is greater than a first voltage threshold. The other third protection unit and the fourth protection unit are configured to be in a conducting state when the voltage between the negative output terminal of the battery cluster and the reference ground is greater than the first voltage threshold.

[0024] In this embodiment, the first protection circuit adopts a Y-connected protection circuit, which has a simple circuit structure and is easy to implement. In addition, the two third protection units share a fourth protection unit, which helps to reduce circuit costs.

[0025] In conjunction with the first to seventh possible embodiments of the first aspect, in the ninth possible embodiment, the first protection circuit includes two third protection units and two fourth protection units. Specifically, one third protection unit and one fourth protection unit of the first protection circuit are connected in series between the positive output terminal of the battery cluster and reference ground, and are configured to be in a conducting state when the voltage between the positive output terminal of the battery cluster and reference ground exceeds a first voltage threshold. The other third protection unit and the other fourth protection unit of the first protection circuit are connected in series between the negative output terminal of the battery cluster and reference ground, and are configured to be in a conducting state when the voltage between the negative output terminal of the battery cluster and reference ground exceeds the first voltage threshold.

[0026] In this embodiment, the first protection circuit adopts a type II connection protection circuit. Since the protection branch between the positive output terminal of the battery cluster and the reference ground and the protection branch between the negative output terminal of the battery cluster and the reference ground are independent of each other, the other protection branch can still work normally when one of the two protection branches is abnormal, thereby improving the reliability of the first protection circuit.

[0027] In conjunction with the eighth or ninth possible implementation of the first aspect, in the tenth possible implementation, each of the third and fourth protection units includes a protection element, or at least two protection elements connected in series and / or in parallel, wherein the protection element includes a gas discharge tube, a varistor, or a transient suppression diode.

[0028] In this embodiment, the structure of each protection unit in the first protection circuit and the types of protection elements in each protection unit are diverse, which can improve the diversity of battery cluster structure and increase flexibility.

[0029] In conjunction with any of the first to tenth possible embodiments of the first aspect, in the eleventh possible embodiment, the energy storage system further includes an energy storage converter, the DC terminal of which is connected to the output terminal of the battery cluster. The energy storage converter includes a second protection circuit connected between the DC terminal of the energy storage converter and a reference ground, for being in a conducting state when the voltage between the DC terminal of the energy storage converter and the reference ground is greater than a first voltage threshold.

[0030] In this embodiment, the operating voltage threshold (i.e., the first voltage threshold) when the second protection circuit in the energy storage converter and the first protection circuit in the battery cluster switch from the off state to the on state is the same. This prevents the lightning current between the DC terminal of the energy storage converter and the output terminal of the battery cluster from flowing to the device with the lower operating voltage threshold of the protection circuit, thereby reducing the damage of the lightning current to the battery cluster or the energy storage converter. Furthermore, by installing a second protection circuit between its DC terminal and the reference ground in the energy storage converter, even when there is a lightning current between the DC terminal of the energy storage converter and the output terminal of the battery cluster, the conducting second protection circuit can discharge the lightning current at the DC terminal of the energy storage converter to the reference ground, thus achieving lightning protection for the energy storage converter and further improving the safety and reliability of the energy storage system under severe lightning weather conditions. Attached Figure Description

[0031] Figure 1 is a schematic diagram of the structure of an energy storage system provided by existing technology;

[0032] Figure 2 is a schematic diagram of the application scenario of the energy storage system provided in this application;

[0033] Figure 3 is a schematic diagram of the structure of the battery cluster provided in this application;

[0034] Figure 4 is a structural schematic diagram of the energy storage system provided in this application;

[0035] Figure 5a is another structural schematic diagram of the energy storage system provided in this application;

[0036] Figure 5b is another structural schematic diagram of the energy storage system provided in this application;

[0037] Figure 6a is another structural schematic diagram of the energy storage system provided in this application;

[0038] Figure 6b is another structural schematic diagram of the energy storage system provided in this application;

[0039] Figure 7 is another structural schematic diagram of the energy storage system provided in this application;

[0040] Figure 8 is another structural schematic diagram of the energy storage system provided in this application. Detailed Implementation

[0041] The energy storage system provided in this application is applicable to various fields, including energy storage backup power (such as residential energy storage, industrial and commercial energy storage, power plant energy storage, and power battery backup power), new energy smart microgrids, and power transmission and distribution. It is suitable for different application scenarios, such as energy storage power supply scenarios, photovoltaic-energy storage hybrid power supply scenarios, and UPS power supply scenarios. The following explanation uses the energy storage power supply scenario as an example.

[0042] Referring to Figure 2, which is a schematic diagram of the application scenario of the energy storage system provided in this application. In the energy storage power supply scenario, the energy storage system provided in this application is the energy storage system shown in Figure 2, which includes a battery cluster 1 and an energy storage converter 2. The two DC terminals of the energy storage converter 2 are connected to the positive output terminal (i.e., positive pole) BAT+ and the negative output terminal (i.e., negative pole) BAT- of the battery cluster 1, respectively. The AC terminal of the energy storage converter 2 is connected to the AC power grid and the AC load. The specific circuit structure of the battery cluster 1 is shown in Figure 3, including multiple battery packs (battery pack PACK1, battery pack PACK2, ..., battery pack PACKn), a battery pack protection circuit 111, a battery pack protection circuit 11n, and a first protection circuit 12, where n is an integer greater than 1. Each battery pack consists of multiple cells connected in series, with battery packs PACK1, PACK2, ..., PACKn connected in series between the positive pole BAT+ and the negative pole BAT- of the battery cluster 1. Battery pack PACK1 and battery pack PACKn are connected to the positive terminal BAT+ and negative terminal BAT- of battery cluster 1, respectively. First protection circuit 12 is connected between the output terminal of battery cluster 1 and reference ground PE. Battery pack protection circuit 111 is connected between the output terminal of battery pack PACK1 and reference ground PE, and battery pack protection circuit 11n is connected between battery pack PACKn and reference ground PE.

[0043] After the energy storage system starts operating, the energy storage converter 2 sequentially converts and inverts the DC power output from battery cluster 1, outputting AC power to the AC grid and AC loads to supply power to them. Simultaneously, if a lightning strike current occurs at the output of battery cluster 1, and the voltage between the output of battery cluster 1 and the reference ground PE exceeds a first voltage threshold, the first protection circuit 12 is activated, allowing most of the lightning strike current at the output of battery cluster 1 to be discharged to the reference ground PE. The remaining small portion of the lightning strike current flows along the internal cables of battery cluster 1 to battery packs PACK1 and PACKn, causing the voltages between the outputs of battery pack PACK1 and the reference ground PE, and the voltages between the outputs of battery pack PACKn and the reference ground PE, to both exceed a second voltage threshold. When the voltage between the output of battery pack PACK1 and the reference ground PE exceeds the second voltage threshold, the battery pack protection circuit 111 is activated, thereby discharging the lightning strike current at the output of battery pack PACK1 to the reference ground PE. When the voltage between the output terminal of the battery pack PACKn and the reference ground PE is greater than the second voltage threshold, the battery pack protection circuit 11n is in the conducting state, thereby discharging the lightning current at the output terminal of the battery pack PACKn to the reference ground PE.

[0044] Specifically, the first voltage threshold is greater than the output voltage of battery cluster 1, and the second voltage threshold is greater than the first voltage threshold. Here, the first voltage threshold being greater than the output voltage of battery cluster 1 ensures that the first protection circuit 12 is in a cut-off state when there is no lightning strike current at the output terminal of battery cluster 1, thus guaranteeing that battery cluster 1 can output voltage normally when there is no lightning strike current at its output terminal. The second voltage threshold being greater than the first voltage threshold ensures that, in the event of a lightning strike current at the output terminal of battery cluster 1, the first protection circuit 12 conducts before the battery pack protection circuits 111 and 11n, thereby allowing most of the lightning strike current to be discharged at the output terminal of battery cluster 1 through the first protection circuit 12, thus preventing most of the lightning strike current from flowing into the battery cluster 1.

[0045] Understandably, when a lightning strike current exists at the output terminal of battery cluster 1, battery cluster 1 can discharge most of the lightning strike current to the reference ground PE by first turning on the first protection circuit 12 at its output terminal. After the first protection circuit 12 is turned on, the voltage between the output terminal of battery cluster 1 and the reference ground PE is clamped to a certain value. This ensures that when a small portion of the lightning strike current flows through the first and last battery packs (PACK1 and PACKn) formed by multiple battery packs connected in series, the voltage between the output terminals of both the first and last battery packs and the reference ground PE is greater than a second voltage threshold. Consequently, the two battery pack protection circuits (PACK11 and PACKn) respectively located at the output terminals of the first and last battery packs are both turned on, discharging the lightning strike current to the reference ground PE and preventing the lightning strike current from flowing further to other battery packs besides the first and last battery packs. Therefore, battery cluster 1 can achieve effective lightning protection when a lightning strike current exists at its output terminal.

[0046] The above are merely examples of application scenarios for the energy storage system provided in this application, and are not exhaustive. This application does not limit the application scenarios.

[0047] The working principle of the energy storage system provided in this application will be illustrated below with reference to Figures 4 and 8.

[0048] Referring to Figure 4, which is a structural schematic diagram of the energy storage system provided in this application, the energy storage system includes a battery cluster 1. The specific circuit structure of the battery cluster 1 is described in the corresponding part of the embodiment shown in Figure 3 above, and will not be repeated here.

[0049] In one embodiment, when a lightning strike current exists at the output terminals (including the positive terminal BAT+ and the negative terminal BAT-) of battery cluster 1, and the voltage between the output terminal of battery cluster 1 and the reference ground PE is greater than a first voltage threshold, the first protection circuit 12 is in a conducting state, allowing most of the lightning strike current at the output terminal of battery cluster 1 to be discharged to the reference ground PE through the first protection circuit 12. The remaining small portion of the lightning strike current flows along the internal cables of battery cluster 1 to battery packs PACK1 and PACKn, causing the voltage between the output terminals of battery packs PACK1 and PE, and the voltage between the output terminals of battery packs PACKn and PE, to both exceed a second voltage threshold. When the voltage between the output terminal of battery pack PACK1 and PE exceeds the second voltage threshold, the battery pack protection circuit 111 is in a conducting state, thereby discharging the lightning strike current at the output terminal of battery pack PACK1 to the reference ground PE. When the voltage between the output terminal of battery pack PACKn and PE exceeds the second voltage threshold, the battery pack protection circuit 11n is in a conducting state, thereby discharging the lightning strike current at the output terminal of battery pack PACKn to the reference ground PE.

[0050] The first voltage threshold is the operating voltage threshold when the first protection circuit 12 switches from the off state to the on state, and the second voltage threshold is the operating voltage threshold when each battery pack protection circuit switches from the off state to the on state. The first voltage threshold is greater than the output voltage of battery cluster 1, and the second voltage threshold is greater than the first voltage threshold. Furthermore, each battery pack protection circuit and the first protection circuit 12 in this application can be a Y-type connection protection circuit or a II-type connection protection circuit.

[0051] In one embodiment, the battery pack protection circuit 111 and the battery pack protection circuit 11n are protection circuits with Y-type connection, and the first protection circuit 12 can be a protection circuit with II-type connection.

[0052] As shown in Figure 5a, the battery pack protection circuit 111 includes a first protection unit 1111, a first protection unit 1112, and a second protection unit 1113. One end of the first protection unit 1111 is connected to the positive output terminal (i.e., positive terminal) of the battery pack PACK1, and one end of the first protection unit 1112 is connected to the negative output terminal (i.e., negative terminal) of the battery pack PACK1. The other end of the first protection unit 1111 is connected to the other end of the first protection unit 1112 and then connected to the reference ground PE through the second protection unit 1113. The battery pack protection circuit 11n includes a first protection unit 11n1, a first protection unit 11n2, and a second protection unit 11n3. One end of the first protection unit 11n1 is connected to the positive output terminal (i.e., positive terminal) of the battery pack PACKn, and one end of the first protection unit 11n2 is connected to the negative output terminal (i.e., negative terminal) of the battery pack PACKn. The other end of the first protection unit 11n1 is connected to the other end of the first protection unit 11n2 and then connected to the reference ground PE through the second protection unit 11n3. The first protection circuit 12 includes a third protection unit 121, a third protection unit 122, a fourth protection unit 123, and a fourth protection unit 124. The third protection unit 121 and the fourth protection unit 123 are connected in series between the positive terminal BAT+ of the battery cluster 1 and the reference ground PE, and the third protection unit 122 and the fourth protection unit 124 are connected in series between the negative terminal BAT- of the battery cluster 1 and the reference ground PE.

[0053] Specifically, when a lightning strike current exists between the positive terminal BAT+ of battery cluster 1 and the reference ground PE, the voltage between the positive terminal BAT+ of battery cluster 1 and the reference ground PE is greater than the first voltage threshold. Therefore, both the third protection unit 121 and the fourth protection unit 123 are in a conducting state, thereby discharging most of the lightning strike current of the positive terminal BAT+ of battery cluster 1 to the reference ground PE. When a lightning strike current exists between the negative terminal BAT- of battery cluster 1 and the reference ground PE, the voltage between the negative terminal BAT- of battery cluster 1 and the reference ground PE is greater than the first voltage threshold. Therefore, both the third protection unit 122 and the fourth protection unit 124 are in a conducting state, thereby discharging most of the lightning strike current of the negative terminal BAT- of battery cluster 1 to the reference ground PE. A small portion of the lightning strike current of the positive terminal BAT+ of battery cluster 1 flows along the cable to battery pack PACK1, causing the voltage between both the positive and negative terminals of battery pack PACK1 and the reference ground PE to exceed the second voltage threshold. When the voltage between the positive terminal of battery pack PACK1 and the reference ground PE exceeds the second voltage threshold, both the first protection unit 1111 and the second protection unit 1113 are in a conducting state; when the voltage between the negative terminal of battery pack PACK1 and the reference ground PE exceeds the second voltage threshold, both the first protection unit 1112 and the second protection unit 1113 are in a conducting state. Thus, the lightning current at the output terminals (including the positive and negative terminals) of battery pack PACK1 is discharged to the reference ground PE. Similarly, a small portion of the lightning current at the negative terminal BAT- of battery cluster 1 flows along the cable to battery pack PACKn, causing the voltage between both the positive and negative terminals of battery pack PACKn and the reference ground PE to exceed the second voltage threshold. When the voltage between the positive terminal of the battery pack PACKn and the reference ground PE exceeds the second voltage threshold, both the first protection unit 11n1 and the second protection unit 11n3 are in the conducting state; when the voltage between the negative terminal of the battery pack PACKn and the reference ground PE exceeds the second voltage threshold, both the first protection unit 11n2 and the second protection unit 11n3 are in the conducting state. Thus, the lightning current at the output terminals (including the positive and negative terminals) of the battery pack PACKn is discharged to the reference ground PE.

[0054] Here, each protection unit in the battery pack protection circuit 111, battery pack protection circuit 11n, and first protection circuit 12 includes a protection element, or at least two protection elements connected in series and / or in parallel. The protection element includes a gas discharge tube, a varistor, or a transient suppression diode.

[0055] For example, each first protection unit in battery pack protection circuit 111 and battery pack protection circuit 11n includes a varistor, and each second protection unit includes a varistor and a gas discharge tube; each third protection unit in first protection circuit 12 includes two varistors, and each fourth protection unit includes a gas discharge tube. See Figure 5b for details of the energy storage system. As shown in Figure 5b, first protection unit 1111 includes a varistor RV111, first protection unit 1112 includes a varistor RV112, and second protection unit 1113 includes a varistor RV113 connected in series with a gas discharge tube GDT111. First protection unit 11n1 includes a varistor RV1n1, first protection unit 11n2 includes a varistor RV1n2, and second protection unit 11n3 includes a varistor RV1n3 connected in series with a gas discharge tube GDT1n1. The third protection unit 121 includes varistors RV21 and RV22 connected in series, and the fourth protection unit 123 includes a gas discharge tube GDT21. The third protection unit 122 includes varistors RV23 and RV24, and the fourth protection unit 124 includes a gas discharge tube GDT22.

[0056] In another embodiment, the battery pack protection circuit 111 and the battery pack protection circuit 11n are protection circuits using type II connections, and the first protection circuit 12 can be a protection circuit using type Y connections.

[0057] As shown in Figure 6a, the battery pack protection circuit 111 includes a first protection unit 1111, a first protection unit 1112, a second protection unit 1113, and a second protection unit 1114. The first protection unit 1111 and the second protection unit 1113 are connected in series between the positive terminal of the battery pack PACK1 and the reference ground PE, and the first protection unit 1112 and the second protection unit 1114 are connected in series between the negative terminal of the battery pack PACK1 and the reference ground PE. The battery pack protection circuit 11n includes a first protection unit 11n1, a first protection unit 11n2, a second protection unit 11n3, and a second protection unit 11n4. The first protection unit 11n1 and the second protection unit 11n3 are connected in series between the positive terminal of the battery pack PACKn and the reference ground PE, and the first protection unit 11n2 and the second protection unit 11n4 are connected in series between the negative terminal of the battery pack PACKn and the reference ground PE. The first protection circuit 12 includes a third protection unit 121, a third protection unit 122, and a fourth protection unit 123. One end of the third protection unit 121 is connected to the positive terminal BAT+ of the battery cluster 1, one end of the third protection unit 122 is connected to the negative terminal BAT- of the battery cluster 1, and the other end of the third protection unit 121 is connected to the other end of the third protection unit 122 and then connected to the reference ground PE through the fourth protection unit 123.

[0058] Specifically, when a lightning strike current exists between the positive terminal BAT+ of battery cluster 1 and the reference ground PE, the voltage between the positive terminal BAT+ of battery cluster 1 and the reference ground PE is greater than the first voltage threshold. Therefore, both the third protection unit 121 and the fourth protection unit 123 are in a conducting state, thereby discharging most of the lightning strike current of the positive terminal BAT+ of battery cluster 1 to the reference ground PE. When a lightning strike current exists between the negative terminal BAT- of battery cluster 1 and the reference ground PE, the voltage between the negative terminal BAT- of battery cluster 1 and the reference ground PE is greater than the first voltage threshold. Therefore, both the third protection unit 122 and the fourth protection unit 123 are in a conducting state, thereby discharging most of the lightning strike current of the negative terminal BAT- of battery cluster 1 to the reference ground PE. A small portion of the lightning strike current of the positive terminal BAT+ of battery cluster 1 flows along the cable to battery pack PACK1, causing the voltage between both the positive and negative terminals of battery pack PACK1 and the reference ground PE to exceed the second voltage threshold. When the voltage between the positive terminal of battery pack PACK1 and the reference ground PE exceeds the second voltage threshold, both the first protection unit 1111 and the second protection unit 1113 are in a conducting state; when the voltage between the negative terminal of battery pack PACK1 and the reference ground PE exceeds the second voltage threshold, both the first protection unit 1112 and the second protection unit 1114 are in a conducting state. This discharges the lightning current at the output terminal of battery pack PACK1 to the reference ground PE. Similarly, a small portion of the lightning current at the negative terminal BAT- of battery cluster 1 flows along the cable to battery pack PACKn, causing the voltage between both the positive and negative terminals of battery pack PACKn and the reference ground PE to exceed the second voltage threshold. When the voltage between the positive terminal of battery pack PACKn and the reference ground PE exceeds the second voltage threshold, both the first protection unit 11n1 and the second protection unit 11n3 are in a conducting state; when the voltage between the negative terminal of battery pack PACKn and the reference ground PE exceeds the second voltage threshold, both the first protection unit 11n2 and the second protection unit 11n4 are in a conducting state. This allows the lightning current at the output of the battery pack PACKn to be discharged to the reference ground PE.

[0059] Here, each protection unit in the battery pack protection circuit 111, battery pack protection circuit 11n, and first protection circuit 12 includes a protection element, or at least two protection elements connected in series and / or in parallel. The protection element includes a gas discharge tube, a varistor, or a transient suppression diode.

[0060] For example, each first protection unit in battery pack protection circuit 111 and battery pack protection circuit 11n includes two varistors, and each second protection unit includes a gas discharge tube; each third protection unit in first protection circuit 12 includes one varistor, and each fourth protection unit includes a varistor and a gas discharge tube. See Figure 6b for details of the energy storage system. As shown in Figure 6b, first protection unit 1111 includes varistors RV111 and RV113 connected in series, first protection unit 1112 includes varistors RV112 and RV114 connected in series, second protection unit 1113 includes a gas discharge tube GDT111, and second protection unit 1114 includes a gas discharge tube GDT112. The first protection unit 11n1 includes varistors RV1n1 and RV1n3 connected in series; the first protection unit 11n2 includes varistors RV1n2 and RV1n4 connected in series; the second protection unit 11n3 includes a gas discharge tube GDT1n1; and the second protection unit 11n4 includes a gas discharge tube GDT1n2. The third protection unit 121 includes a varistor RV21; the third protection unit 122 includes a varistor RV23; and the fourth protection unit 123 includes a varistor RV22 and a gas discharge tube GDT21 connected in series.

[0061] Battery pack protection circuit 111, battery pack protection circuit 11n, and first protection circuit 12 are all protection circuits using type II connection. For details, please refer to the description of the corresponding parts in the embodiments shown in Figures 5a and 6a, which will not be repeated here.

[0062] In another embodiment, the battery pack protection circuit 111, the battery pack protection circuit 11n, and the first protection circuit 12 are all protection circuits with Y-type connections. Please refer to the description of the corresponding parts in the embodiments shown in Figures 5a and 6a for details, which will not be repeated here.

[0063] It is understandable that both the battery pack protection circuit and the first protection circuit 12 in battery cluster 1 can adopt Y-type or II-type connection protection circuits. Therefore, it can be known that there are four possible combinations of each battery pack protection circuit and the first protection circuit 12: Y-type + Y-type, II-type + II-type, Y-type + II-type, and II-type + Y-type. The variety of combinations can improve the diversity of the battery cluster 1 structure and increase its flexibility.

[0064] Optionally, the battery cluster 1 shown in Figure 4 also includes a cluster control box, as detailed in Figure 7. As shown in Figure 7, the battery cluster 1 also includes a cluster control box 13, which is located between the n battery packs and the output terminal of the battery cluster 1. The cluster control box 13 includes a protection switch 131 and a controller 132. The n battery packs are connected in series and then connected to the output terminal of the battery cluster 1 via the protection switch 131. The controller 132 is used to control the protection switch 131 to open in the event of a fault in the battery cluster 1 (such as a short circuit at the output terminal of the battery cluster 1), to prevent the fault in the battery cluster 1 from spreading to the energy storage converter 2.

[0065] It should be noted that the first protection circuit 12 can be placed inside or outside the cluster control box 13, and this application does not impose any restrictions on this. When the first protection circuit 12 is located inside the cluster control box 13, the existing internal space of the cluster control box 13 can be effectively utilized, thereby not increasing the volume of the battery cluster 1, which is beneficial to the miniaturization design of the battery cluster 1.

[0066] Optionally, the battery cluster 1 shown in Figure 4 may further include n DC / DC circuits corresponding one-to-one with the aforementioned n battery packs. The i-th DC / DC circuit in the n DC / DC circuits corresponds to the i-th battery pack in the n battery packs, where 1 ≤ i ≤ n. The two input terminals of the i-th DC / DC circuit are connected to the positive and negative terminals of the i-th battery pack, respectively, and the two output terminals of the i-th DC / DC circuit are connected to the positive DC bus and the negative DC bus, respectively. The i-th DC / DC circuit is used to transfer the energy of the i-th battery pack between the positive and negative DC buses when the energy (e.g., state of charge, output voltage) of the i-th battery pack is high; and to transfer the energy between the positive and negative DC buses to the i-th battery pack when the energy of the i-th battery pack is low. Thus, by setting DC / DC circuits corresponding to each battery pack in the battery cluster 1, energy balance among the aforementioned n battery packs is achieved. Furthermore, the n DC / DC circuits corresponding to the n battery packs can be placed inside or outside their respective battery packs; this application does not impose any restrictions on this. Moreover, to save on circuit costs, the aforementioned n battery packs can also share the same DC / DC circuit, thus requiring only one DC / DC circuit in battery cluster 1 to achieve energy balance among the n battery packs.

[0067] Furthermore, the energy storage system shown in Figure 4 also includes an energy storage converter, as detailed in Figure 7. As shown in Figure 7, the energy storage system also includes an energy storage converter 2. The DC terminal of the energy storage converter 2 is connected to the output terminal of the battery cluster 1, and the AC terminal of the energy storage converter 2 is used to connect to the AC power grid. The energy storage converter 2 includes a DC / DC circuit 21, a DC / AC circuit 22, and a second protection circuit 23. The DC terminal of the DC / AC circuit 22 is connected to the DC terminal of the energy storage converter 2 through the DC / DC circuit 21, and the AC terminal of the DC / AC circuit 22 is connected to the AC terminal of the energy storage converter 2. The second protection circuit 23 is connected between the DC terminal of the energy storage converter 2 and the reference ground PE. It is used to be in a conducting state when the voltage between the DC terminal of the energy storage converter 2 and the reference ground PE is greater than a first voltage threshold. Thus, when there is a lightning strike current at the DC terminal of the energy storage converter 2, the conducting second protection circuit 23 can discharge the lightning strike current at the DC terminal of the energy storage converter 2 to the reference ground PE, thereby achieving lightning protection for the energy storage converter 2. Furthermore, since the operating voltage thresholds of the second protection circuit 23 and the first protection circuit 12 when switching from the off state to the on state are the same, the specific circuit structure and working principle of the second protection circuit 23 can be found in the corresponding description of the first protection circuit 12 in the above embodiments, and will not be repeated here.

[0068] It should be understood that the battery cluster 1 shown in Figures 4 to 7 is illustrated using the example of setting battery pack protection circuits only at the first and last battery packs formed by connecting the above n battery packs in series. Considering that the two battery pack protection circuits at the first and last battery packs may malfunction, resulting in the failure of protection for the above n battery packs, battery cluster 1 is equipped with a battery pack protection circuit at each of the above n battery packs to improve the reliability of battery cluster 1 when performing lightning protection. Please refer to Figure 8 for details. As shown in Figure 8, battery cluster 1 includes battery pack protection circuit 111, battery pack protection circuit 112, ..., and battery pack protection circuit 11n, for a total of n battery pack protection circuits. Among them, battery pack protection circuit 112 is connected between the output terminal of battery pack PACK2 and the reference ground PE. It is in a conducting state when the voltage between the output terminal of battery pack PACK2 and the reference ground PE is greater than a second voltage threshold, so as to discharge the lightning current at the output terminal of battery pack PACK2 to the reference ground PE; ...; battery pack protection circuit 11(n-1) is connected between the output terminal of battery pack PACK(n-1) and the reference ground PE. It is in a conducting state when the voltage between the output terminal of battery pack PACK(n-1) and the reference ground PE is greater than a second voltage threshold, so as to discharge the lightning current at the output terminal of battery pack PACK(n-1) to the reference ground PE. For the specific circuit structure and working principle of each battery pack protection circuit in battery pack protection circuits 112 to 11(n-1), please refer to the description of battery pack protection circuit 111 in the above embodiments; for the other circuits in the energy storage system besides the battery pack protection circuits and their working principles, please refer to the description of the corresponding parts in the energy storage system shown in Figures 4 to 7, which will not be repeated here.

[0069] It should be noted that the battery pack protection circuit connected to the output terminal of the battery pack in battery cluster 1 can be placed outside or inside the connected battery pack, and this application does not impose any restrictions on this. When the battery pack protection circuit is located inside the connected battery pack, the existing internal space of the battery pack can be effectively utilized, thereby not increasing the volume of battery cluster 1, which is beneficial to the miniaturization design of battery cluster 1.

[0070] In this application, when a lightning strike current exists at the output terminal of battery cluster 1, battery cluster 1 can discharge most of the lightning strike current to the reference ground PE by first turning on the first protection circuit 12 at its output terminal. A small portion of the lightning strike current at the output terminal of battery cluster 1 will flow to the first and last battery packs formed by multiple battery packs connected in series. Two battery pack protection circuits are respectively provided between the output terminals of the first and last battery packs and the reference ground. These circuits can be turned on when a lightning strike current exists at the output terminals of the first and last battery packs, thereby discharging the lightning strike current at the output terminals of the first and last battery packs to the reference ground PE, preventing the lightning strike current from further flowing to other battery packs besides the first and last battery packs. Therefore, battery cluster 1 can achieve effective lightning protection when a lightning strike current exists at its output terminal.

[0071] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. An energy storage system, characterized in that, The energy storage system includes a battery cluster, which comprises multiple battery packs, a first battery pack protection circuit, a second battery pack protection circuit, and a first protection circuit. The output terminals of the battery cluster include a positive output terminal and a negative output terminal, wherein: The plurality of battery packs are connected in series between the positive output terminal and the negative output terminal of the battery cluster, and the plurality of battery packs include a first battery pack and a second battery pack respectively connected to the positive output terminal and the negative output terminal of the battery cluster; The first protection circuit is connected between the output terminal of the battery cluster and the reference ground, and is used to be in a conducting state when the voltage between the output terminal of the battery cluster and the reference ground is greater than a first voltage threshold, wherein the first voltage threshold is greater than the output voltage of the battery cluster; The first battery pack protection circuit is connected between the output terminal of the first battery pack and the reference ground, and is used to be in a conducting state when the voltage between the output terminal of the first battery pack and the reference ground is greater than a second voltage threshold, wherein the second voltage threshold is greater than the first voltage threshold. The second battery pack protection circuit is connected between the output terminal of the second battery pack and the reference ground, and is used to be in a conducting state when the voltage between the output terminal of the second battery pack and the reference ground is greater than the second voltage threshold.

2. The energy storage system according to claim 1, characterized in that, The first battery pack protection circuit is located inside the first battery pack, and the second battery pack protection circuit is located inside the second battery pack.

3. The energy storage system according to claim 1 or 2, characterized in that, The plurality of battery packs includes an i-th battery pack, and the battery cluster includes an i-th battery pack protection circuit corresponding to the i-th battery pack, 1≤i≤n and n>2, where n is the number of battery packs in the battery cluster; The protection circuit for the i-th battery pack is connected between the output terminal of the i-th battery pack and the reference ground, and is used to be in a conducting state when the voltage between the output terminal of the i-th battery pack and the reference ground is greater than the second voltage threshold.

4. The energy storage system according to claim 3, characterized in that, The protection circuit for the i-th battery pack is located within the i-th battery pack.

5. The energy storage system according to any one of claims 1-4, characterized in that, The first battery pack protection circuit includes two first protection units and a second protection unit. The output terminals of the first battery pack include a positive output terminal and a negative output terminal, wherein: One end of one of the two first protection units is connected to the positive output terminal of the first battery pack, and one end of the other first protection unit is connected to the negative output terminal of the first battery pack. The other ends of the two first protection units are connected and then connected to the reference ground through the second protection unit. The first protection unit and the second protection unit are configured to be in an on state when the voltage between the positive output terminal of the first battery pack and the reference ground is greater than the second voltage threshold. The other first protection unit and the second protection unit are configured to be in an on state when the voltage between the negative output terminal of the first battery pack and the reference ground is greater than the second voltage threshold.

6. The energy storage system according to any one of claims 1-4, characterized in that, The first battery pack protection circuit includes two first protection units and two second protection units. The output terminals of the first battery pack include a positive output terminal and a negative output terminal, wherein: A first protection unit and a second protection unit in the first battery pack protection circuit are connected in series between the positive output terminal of the first battery pack and the reference ground, and are used to be in the conducting state when the voltage between the positive output terminal of the first battery pack and the reference ground is greater than the second voltage threshold. Another first protection unit and another second protection unit in the first battery pack protection circuit are connected in series between the negative output terminal of the first battery pack and the reference ground, and are used to be in the conducting state when the voltage between the negative output terminal of the first battery pack and the reference ground is greater than the second voltage threshold.

7. The energy storage system according to claim 5 or 6, characterized in that, Each of the first protection unit and the second protection unit includes a protection element, or at least two protection elements connected in series and / or in parallel, wherein the protection element includes a gas discharge tube, a varistor, or a transient suppression diode.

8. The energy storage system according to any one of claims 1-7, characterized in that, The battery cluster also includes a cluster control box, and the first protection circuit is located inside the cluster control box.

9. The energy storage system according to any one of claims 1-8, characterized in that, The first protection circuit includes two third protection units and a fourth protection unit, wherein: One end of one of the two third protection units is connected to the positive output terminal of the battery cluster, and one end of the other third protection unit is connected to the negative output terminal of the battery cluster. The other ends of the two third protection units are connected to the reference ground through the fourth protection unit. The third protection unit and the fourth protection unit are configured to be in an on state when the voltage between the positive output terminal of the battery cluster and the reference ground is greater than the first voltage threshold. The other third protection unit and the fourth protection unit are configured to be in a conducting state when the voltage between the negative output terminal of the battery cluster and the reference ground is greater than the first voltage threshold.

10. The energy storage system according to any one of claims 1-8, characterized in that, The first protection circuit includes two third protection units and two fourth protection units, wherein: A third protection unit and a fourth protection unit in the first protection circuit are connected in series between the positive output terminal of the battery cluster and the reference ground, and are used to be in the conducting state when the voltage between the positive output terminal of the battery cluster and the reference ground is greater than the first voltage threshold. The third and fourth protection units in the first protection circuit are connected in series between the negative output terminal of the battery cluster and the reference ground, and are used to be in the conducting state when the voltage between the negative output terminal of the battery cluster and the reference ground is greater than the first voltage threshold.

11. The energy storage system according to claim 9 or 10, characterized in that, Each of the third and fourth protection units includes a protection element, or at least two protection elements connected in series and / or in parallel, wherein the protection element includes a gas discharge tube, a varistor, or a transient suppression diode.

12. The energy storage system according to any one of claims 1-11, characterized in that, The energy storage system also includes an energy storage converter, the DC terminal of which is connected to the output terminal of the battery cluster. The energy storage converter includes a second protection circuit, which is connected between the DC terminal of the energy storage converter and the reference ground. The second protection circuit is used to be in a conducting state when the voltage between the DC terminal of the energy storage converter and the reference ground is greater than the first voltage threshold.

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