Energy storage system and cooling method thereof

Abstract

The invention discloses an energy storage system and a cooling method thereof, and relates to the technical field of energy storage equipment. The energy storage system comprises a box body, a battery pack, an energy storage converter and a liquid cooling unit, and the battery pack and the energy storage converter are provided with a first liquid cooling plate and a second liquid cooling plate respectively; a liquid outlet pipeline is connected between a liquid outlet of the liquid cooling unit and the first liquid cooling plate, a liquid return pipeline is connected between a liquid return port of the liquid cooling unit and the first liquid cooling plate, and the second liquid cooling plate is connected with the liquid return pipeline, so that cooling liquid can flow through the second liquid cooling plate and return to the liquid cooling unit. Based on the technical scheme disclosed by the invention, the liquid discharged from the liquid cooling unit can pass through the battery pack, then pass through the energy storage converter and then return to the liquid cooling unit, so that the number of systems can be reduced, the cost and the energy consumption can be reduced, and the energy efficiency of the energy storage system is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of energy storage equipment technology, and more specifically to an energy storage system and its cooling method. Background Technology

[0002] An energy storage system is a device or system that can store electrical energy (or other forms of energy) and release it for use when needed. Its core function is to solve the problem of "asynchronous power production and use", such as scenarios where there is more photovoltaic power generation during the day and more electricity consumption at night.

[0003] Currently, in existing energy storage systems, the liquid from the liquid cooler flows through the battery pack and back to the liquid cooler without passing through any other products. The heat dissipation of the power conversion system (PCS) is usually achieved by installing a fan at the PCS exhaust port for ventilation, or by adding a separate module and circuit to the liquid cooler to dissipate heat from the PCS.

[0004] In related technologies, since the temperature control systems of the battery pack and the PCS are two independent systems, and both systems use energy from the energy storage system, the operating cost and energy consumption of the existing energy storage system are relatively high, which affects the energy efficiency of the energy storage system. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose an energy storage system and its cooling method to solve the technical problems of high cost and energy consumption and low energy efficiency of existing energy storage systems.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an energy storage system, including a housing, a battery pack, an energy storage converter, and a liquid cooling unit. A first liquid cooling plate and a second liquid cooling plate are respectively provided at the battery pack and the energy storage converter. An outlet pipe is connected between the outlet of the liquid cooling unit and the first liquid cooling plate, and a return pipe is connected between the return port of the liquid cooling unit and the first liquid cooling plate. The second liquid cooling plate is connected to the return pipe so that the coolant can flow through the second liquid cooling plate and return to the liquid cooling unit.

[0007] In some embodiments, the battery pack is provided in multiple ways, and the first liquid cooling plate is provided in a one-to-one correspondence with the battery pack; the liquid outlet pipeline is sequentially connected to each of the first liquid cooling plates.

[0008] In some embodiments, the energy storage converter is located below the battery pack within the housing.

[0009] In some embodiments, the enclosure includes a battery compartment and an electrical compartment that are isolated from each other, with the battery pack disposed in the battery compartment and the energy storage converter and / or the liquid cooling unit disposed in the electrical compartment.

[0010] In some embodiments, the inner diameter of the return liquid pipeline is larger than the inner diameter of the inner pipeline of the second liquid cooling plate.

[0011] In some embodiments, an electric reversing valve is provided on the return pipeline, and the electric reversing valve is provided with a first outlet and a second outlet respectively. The first outlet is connected to the liquid inlet of the second liquid cooling plate, and the second outlet is connected to the return port of the liquid cooling unit through a pipeline.

[0012] In some embodiments, temperature sensors are provided at both the battery pack and the energy storage converter. The temperature sensors are electrically connected to a control module, which is electrically connected to the liquid chiller unit to achieve automatic control of the liquid chiller unit.

[0013] Secondly, the present invention also provides a cooling method for an energy storage system, which, using the above-mentioned energy storage system, includes the following steps: Turn on the liquid cooling unit; Control the flow of liquid into the first liquid cooling plate to cool or heat the battery pack; The liquid discharged from the first liquid cooling plate is controlled to flow into the second liquid cooling plate to cool the energy storage converter; Control the return of coolant from the second liquid cooling plate to the liquid cooling unit; Control the liquid cooling unit to stop, or repeat the above steps to achieve cyclic operation.

[0014] In some embodiments, before starting the liquid-cooled unit, the cooling method further includes: Monitor the temperature of the battery pack and energy storage converter; Determine whether to start the liquid cooling unit based on the temperature of the battery pack and energy storage converter; The conditions for determining whether to start the liquid cooling unit are: the temperature of the battery pack is as low as the low temperature threshold or exceeds the high temperature threshold, or the temperature of the energy storage converter exceeds the high temperature threshold.

[0015] In some embodiments, before starting the liquid-cooled unit, the cooling method further includes: Monitor the temperature of the battery pack and energy storage converter; Adjust the operating status of the electric reversing valve according to the temperature of the battery pack and energy storage converter; The electric reversing valve has at least two operating states: connected to the second liquid cooling plate and disconnected from the second liquid cooling plate.

[0016] Compared with the prior art, the present invention provides an energy storage system and its cooling method, which connects the liquid cooling unit and the first liquid cooling plate at the battery pack through the liquid outlet pipeline, and sets the second liquid cooling plate on the return pipeline between the first liquid cooling plate and the liquid cooling unit, so that the coolant can flow through the second liquid cooling plate and return to the liquid cooling unit after being discharged through the first liquid cooling plate.

[0017] In this way, the temperatures of both the battery pack and the energy storage converter are controlled by the same liquid chiller, reducing the number of systems, which helps to lower costs and energy consumption, and improve the energy efficiency of the energy storage system. Simultaneously, the liquid discharged from the liquid chiller first passes through the battery pack, then through the energy storage converter, and finally back to the liquid chiller. In winter, the heat from the energy storage converter is used to heat the liquid, eliminating the need for the liquid chiller to discharge the hot liquid used to heat the battery pack. This significantly reduces the operating energy consumption of the liquid chiller and further improves the energy efficiency of the energy storage system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of an energy storage system in one embodiment of the present invention; Figure 2 This is a schematic diagram of the liquid circulation path in one embodiment of the present invention; Figure 3 This is a schematic diagram of the liquid circulation path in another embodiment of the present invention; Figure 4 This is a schematic flowchart of a cooling method for an energy storage system in one embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the working principle of the energy storage system in summer according to one embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the working principle of the energy storage system in winter according to one embodiment of the present invention.

[0019] Explanation of reference numerals in the attached drawings: 1. Housing; 11. Battery compartment; 12. Electrical compartment; 2. Battery pack; 3. Energy storage converter; 4. Liquid cooling unit; 5. First liquid cooling plate; 6. Second liquid cooling plate; 7. Liquid outlet pipe; 8. Liquid return pipe; 81. First liquid return pipe; 82. Second liquid return pipe; 9. Electric reversing valve. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] To address the aforementioned technical problems, this invention provides an energy storage system and its cooling method, which allows the liquid coolant discharged from the liquid cooler unit to first pass through the battery pack, then through the energy storage converter, and finally back to the liquid cooler unit. This reduces the number of systems, helps to lower costs and energy consumption, and significantly improves the energy efficiency of the energy storage system.

[0022] Please see Figure 1 , Figure 1 The diagram below shows the overall structure of an energy storage system according to an embodiment of the present invention. The energy storage system includes a housing 1, in which a battery pack 2, an energy storage converter 3 (PCS), and a liquid cooling unit 4 are respectively installed. A first liquid cooling plate 5 and a second liquid cooling plate 6 are respectively installed at the battery pack 2 and the energy storage converter 3. Both the first liquid cooling plate 5 and the second liquid cooling plate 6 can be connected to the liquid cooling unit 4 through pipelines, so that the liquid cooling unit 4 can simultaneously meet the temperature control requirements of the battery pack 2 and the energy storage converter 3.

[0023] In this embodiment, the interior of the housing 1 can be divided into a battery compartment 11 and an electrical compartment 12 by a partition, with the battery compartment 11 positioned above the electrical compartment 12. Based on this, the aforementioned battery pack 2 can be installed inside the battery compartment 11, while the energy storage converter 3 and the liquid cooling unit 4 can be installed in the electrical compartment 12.

[0024] At this point, inside the housing 1, the battery pack 2 is located above the energy storage converter 3, while the liquid cooling unit 4 can be located at the bottom of the housing 1 (i.e., the bottom of the electrical compartment 12) and below the energy storage converter 3. Based on this, the aforementioned first liquid cooling plate 5 can be located at the bottom of the battery pack 2, and the second liquid cooling plate 6 can be located at the bottom of the energy storage converter 3.

[0025] It is understood that in this embodiment, the battery compartment 11 and the electrical compartment 12 are separated inside the housing 1 for installing the battery pack 2 and the energy storage converter 3, respectively. However, in some other embodiments, the internal space of the housing 1 may not be separated. For example, the battery pack 2 and the energy storage converter 3 can be installed in the battery compartment 11 at the same time. The specific design can be determined according to the design requirements and is not specifically limited here.

[0026] Based on the above-mentioned configuration of housing 1, battery pack 2, energy storage converter 3 and liquid cooling unit 4, in order to achieve temperature control of battery pack 2 and energy storage converter 3, liquid outlet pipe 7 and liquid return pipe 8 are respectively installed in housing 1.

[0027] One end of the liquid outlet pipe 7 can be connected to the liquid outlet of the liquid cooling unit 4, and the other end can be connected to the liquid inlet of the first liquid cooling plate 5. In this way, the liquid discharged from the liquid cooling unit 4 can enter the first liquid cooling plate 5 through the liquid outlet pipe 7 to cool or heat the battery pack 2.

[0028] Please see Figure 2The aforementioned return liquid pipeline 8 may include a first return liquid pipeline 81 and a second return liquid pipeline 82. One end of the first return liquid pipeline 81 is connected to the liquid outlet of the first liquid cooling plate 5, while the other end can be connected to the liquid inlet of the second liquid cooling plate 6. The two ends of the second return liquid pipeline 82 can be connected to the liquid outlet of the second liquid cooling plate 6 and the return liquid inlet of the liquid cooling unit 4, respectively.

[0029] In this way, the liquid discharged from the first liquid cooling plate 5 can flow into the second liquid cooling plate 6 through the first return liquid pipeline 81 and cool the energy storage converter 3; finally, the liquid discharged from the second liquid cooling plate 6 can return to the liquid cooling unit 4 through the second return liquid pipeline 82, which facilitates the realization of cyclic operation.

[0030] Meanwhile, it is understandable that since the energy storage converter 3 is located below the battery pack 2, the liquid from the battery pack 2 flows downward through the energy storage converter 3, and the system can flow smoothly without pressurization, which helps to reduce the output power of the liquid cooling unit 4.

[0031] It should be noted that in this embodiment, the battery pack 2 can be configured as one or multiple units within the housing 1.

[0032] When multiple battery packs 2 are provided, the aforementioned first liquid cooling plate 5 is provided in a one-to-one correspondence with the battery pack 2. Each first liquid cooling plate 5 can be provided at the bottom of the corresponding battery pack 2 so as to cool or heat the corresponding battery pack 2.

[0033] At this time, the liquid outlet pipe 7 can be connected to each of the first liquid cooling plates 5 in sequence, so that the liquid discharged from the liquid cooling unit 4 can enter each of the first liquid cooling plates 5 respectively, and cool or heat each of the battery packs 2 respectively.

[0034] In one embodiment, to improve the heat absorption and dissipation effect of the second liquid cooling plate 6, the inner diameter of the return liquid pipe 8 can be larger than the inner diameter of the inner pipe of the second liquid cooling plate 6. Preferably, the inner diameter of the return liquid pipe 8 can be 1.2-2 times the inner diameter of the inner pipe of the second liquid cooling plate 6.

[0035] In this way, the inner diameter of the inner pipe of the second liquid cooling plate 6 is smaller than the inner diameter of the return pipe 8, and the liquid flow rate from the return pipe 8 to the second liquid cooling plate 6 increases, which is beneficial for the second liquid cooling plate 6 to absorb and dissipate heat. At the same time, it can reduce the pressure, reduce the stress on the second liquid cooling plate 6, and prevent the second liquid cooling plate 6 from leaking.

[0036] In one embodiment, please refer to Figure 3 An electric reversing valve 9 is installed on the return line 8, which can control the direction of liquid flow.

[0037] Specifically, the electric reversing valve 9 can be installed on the first return liquid line 81, and the electric reversing valve 9 is provided with a first outlet and a second outlet. The first outlet can be connected to the liquid inlet of the second liquid cooling plate 6, and the second outlet can be directly connected to the second return liquid line 82 through a pipeline. One end of the second return liquid line 82 can be connected to the liquid outlet of the second liquid cooling plate 6, and the other end can be connected to the return liquid port of the liquid cooling unit 4.

[0038] In this way, after the liquid is discharged through the first liquid cooling plate 5, when it flows through the electric reversing valve 9, the electric reversing valve 9 can adjust the liquid flow direction according to actual needs, so that the liquid can either flow directly to the return port of the liquid cooling unit 4, or flow through the second liquid cooling plate 6 to the return port of the liquid cooling unit.

[0039] For example, when the ambient temperature is not high, the battery pack 2 needs to be cooled, but the energy storage converter 3 does not need to be cooled. The electric reversing valve 9 can disconnect the first outlet and make the second outlet open. In this way, when the liquid flows through the electric reversing valve 9, it can go directly back to the liquid cooler 4 without passing through the energy storage converter 3, thereby reducing the power consumption of the liquid cooler 4.

[0040] When the energy storage converter 3 also needs to be cooled, the first outlet of the electric reversing valve 9 can be opened and the second outlet can be closed, so that the liquid discharged through the first liquid cooling plate 5 can flow normally to the second liquid cooling plate 6 and cool the energy storage converter 3.

[0041] To facilitate determining the start-up timing of the liquid-cooled unit 4, temperature sensors can be installed at key nodes of the energy storage system, along with a matching control module, to achieve automatic control of the liquid-cooled unit 4.

[0042] For example, in one embodiment, temperature sensors (not shown in the figure) can be installed at both the battery pack 2 and the energy storage converter 3. The temperature sensors can be electrically connected to the matching control module (such as a PLC controller or industrial computer) via wired or wireless means, and the control module can be further electrically connected to the liquid cooling unit 4.

[0043] In this way, with the help of temperature sensors, the system can monitor the temperature of battery pack 2 and energy storage converter 3 in real time. When the temperature of either part of battery pack 2 or energy storage converter 3 reaches the preset value, the control module can automatically use liquid cooling unit 4 to cool or heat battery pack 2, or to cool down energy storage converter 3.

[0044] In this way, the working state of the liquid cooling unit 4 can be triggered bidirectionally by the temperature of the battery pack 2 and the PCS. That is, by setting temperature sensors to monitor the temperature of the battery pack 2 and the energy storage converter 3 in real time, the high or low temperature threshold of the battery pack 2 and the high temperature threshold of the energy storage converter 3 can trigger the corresponding control program to start the liquid cooling unit 4 to work.

[0045] Based on the energy storage system described above, please refer to [link / reference]. Figure 4 The present invention also provides a cooling method for an energy storage system, comprising the following steps: Turn on liquid cooling unit 4; Control the flow of liquid into the first liquid cooling plate 5 to cool or heat the battery pack 2; The liquid discharged from the first liquid cooling plate 5 is controlled to flow into the second liquid cooling plate 6 to cool the energy storage converter 3; Control the coolant in the second liquid cooling plate 6 to return to the liquid cooling unit 4; Control the liquid cooling unit 4 to stop, or repeat the above steps to achieve cyclic operation.

[0046] Understandably, before starting the liquid chiller unit 4, one can determine whether it is necessary to start the liquid chiller unit 4 based on the temperature of the relevant nodes in the system.

[0047] For example, in one embodiment, before turning on the liquid cooling unit 4, the cooling method may further include the following steps: Monitor the temperature of battery pack 2 and energy storage converter 3; Determine whether to turn on the liquid cooling unit 4 based on the temperature of the battery pack 2 and the energy storage converter 3; The conditions for determining to start the liquid cooling unit 4 are: the temperature of the battery pack 2 is lower than the low temperature threshold or exceeds the high temperature threshold, or the temperature of the energy storage converter 3 exceeds the high temperature threshold.

[0048] In practical applications, temperature sensors installed at battery pack 2 and energy storage converter 3, along with a matching control module, can be used to monitor the temperatures of battery pack 2 and energy storage converter 3 in real time. Based on the monitoring data and the actual parameters of battery pack 2 and energy storage converter 3, it can be determined whether battery pack 2 needs cooling or heating, and whether energy storage converter 3 needs cooling.

[0049] Taking battery pack 2 as an example, in actual judgment, either the low temperature threshold or the high temperature threshold of battery pack 2 can trigger the system's control program to start the liquid cooling unit 4. For example, when the temperature of battery pack 2 drops to its low temperature threshold or exceeds its high temperature threshold, the liquid cooling unit 4 can be turned on to heat or cool the battery pack 2.

[0050] As for the energy storage converter 3, when its temperature exceeds the high temperature threshold, the control module can also automatically start the liquid cooling unit 4 to cool down the energy storage converter 3.

[0051] It should be noted that during normal operation, the operating temperature of the battery pack 2 is generally much lower than that of the energy storage converter 3. For example, in one embodiment, the operating temperature of the battery pack 2 is generally controlled at 20-30℃, and the operating temperature of the energy storage converter 3 is controlled below 50℃.

[0052] Therefore, the temperature of the liquid discharged through the first liquid cooling plate 5 is usually lower than the temperature of the energy storage converter 3. Thus, the liquid discharged through the first liquid cooling plate 5 can be controlled to enter the second liquid cooling plate 6 and continue to absorb the heat of the energy storage converter 3 to cool the energy storage converter 3.

[0053] Meanwhile, the temperature of battery pack 2 is related to the ambient temperature, and the operating temperature of battery pack 2 cannot be too high or too low, otherwise it will affect the working performance of battery pack 2.

[0054] Therefore, when the ambient temperature is relatively high, the battery pack 2 usually triggers the start-up procedure of the liquid cooling unit 4 through the high temperature threshold; while when the ambient temperature is low, the operating temperature of the battery pack 2 is too low, and the start-up procedure of the liquid cooling unit 4 may be triggered through the low temperature threshold.

[0055] In one embodiment, please refer to Figure 3 For the case where the electric reversing valve 9 is installed in the system, before starting the liquid cooling unit 4, the cooling method further includes the following steps: Monitor the temperature of battery pack 2 and energy storage converter 3; Adjust the operating state of the electric reversing valve 9 according to the temperature of the battery pack 2 and the energy storage converter 3; The electric reversing valve 9 has at least two operating states: connected to the second liquid cooling plate 6 and disconnected from the second liquid cooling plate 6.

[0056] At this time, based on the temperatures of the battery pack 2 and the energy storage converter 3, it can be determined whether the battery pack 2 needs to be heated or cooled, and whether the energy storage converter 3 needs to be cooled down. Based on the monitoring results, the working state of the electric reversing valve 9 can be adjusted so that the first outlet of the electric reversing valve 9 is open and the second outlet is closed, or the first outlet is closed and the second outlet is open.

[0057] In fact, as explained above, the system monitors the temperature of battery pack 2 and energy storage converter 3 through temperature sensors. In conjunction with the control module, the liquid cooling unit 4 can be automatically started when it is necessary to start the liquid cooling unit 4.

[0058] During this process, the electric reversing valve 9 can also be electrically connected to the control module, so that under certain circumstances, the control module can control the electric reversing valve 9 to achieve automatic reversing.

[0059] For example, when the ambient temperature is not high and the battery pack 2 needs cooling, but the energy storage converter 3 does not require cooling, the control module can transmit an electrical signal to the electric reversing valve 9 and control the first outlet of the electric reversing valve 9 to close and the second outlet to open, so that the liquid discharged through the first liquid cooling plate 5 can return directly to the liquid cooling unit 4 without passing through the second liquid cooling plate 6. In this way, the liquid is prevented from absorbing heat from the energy storage converter 3, which helps to reduce the power consumption of the liquid cooling unit 4.

[0060] When the temperature of the energy storage converter 3 reaches the corresponding threshold, the control module can control the electric reversing valve 9 to switch, so that the first outlet is open and the second outlet is closed, so that the liquid discharged through the first liquid cooling plate 5 can flow normally into the second liquid cooling plate 6 and cool the energy storage converter 3.

[0061] It should be noted that, in this embodiment, due to the difference in operating temperature between the battery pack 2 and the energy storage converter 3, the energy storage system can adjust its actual operating state according to regional and / or seasonal temperature changes.

[0062] For example, in summer, such as Figure 5 As shown, the liquid cooling unit 4 can discharge cold water (i.e., low-temperature liquid) at X℃, which passes through the first liquid cooling plate 5 at the bottom of the battery pack 2 to cool the battery pack 2. The temperature of the liquid discharged through the first liquid cooling plate 5 (i.e., medium-temperature liquid) is expected to be around X+5℃, which is still much lower than the temperature of the energy storage converter 3. Therefore, the liquid can pass through the second liquid cooling plate 6 to absorb the heat of the energy storage converter 3 to achieve a cooling effect on the energy storage converter 3. After absorbing the heat of the energy storage converter 3, the liquid becomes a high-temperature liquid.

[0063] In winter, such as Figure 6 As shown, the liquid cooling unit 4 can discharge hot water at Y℃ (i.e., medium-temperature liquid), which heats the battery pack 2 by passing through the first liquid cooling plate 5 at the bottom of the battery pack 2. The temperature of the liquid discharged after passing through the first liquid cooling plate 5 (i.e., low-temperature liquid) is expected to be around Y-5℃, which is still much lower than the temperature of the PCS. Therefore, the liquid can pass through the second liquid cooling plate 6 to absorb heat from the energy storage converter 3, thereby achieving a cooling effect on the PCS. The liquid (i.e., medium-temperature liquid) returning to the liquid cooling unit 4 after passing through the second liquid cooling plate 6 returns to a temperature of around Y℃. Therefore, the liquid cooling unit 4 does not need to perform excessive heating and can directly discharge the liquid for circulation.

[0064] Understandably, the definitions of so-called low temperature, medium temperature, and high temperature are relative and need to be defined in conjunction with the temperatures of battery pack 2 and energy storage converter 3.

[0065] By using the above methods, not only can the number of systems be reduced, which helps to lower costs and energy consumption, but the energy efficiency of the energy storage system can also be greatly improved.

[0066] In the description of this application, it should be noted that the terms "upper" and "lower," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0067] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0068] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An energy storage system, characterized in that, The device includes a housing, a battery pack, an energy storage converter, and a liquid cooling unit. A first liquid cooling plate and a second liquid cooling plate are respectively installed at the battery pack and the energy storage converter. An outlet pipe is connected between the outlet of the liquid cooling unit and the first liquid cooling plate, and a return pipe is connected between the return port of the liquid cooling unit and the first liquid cooling plate. The second liquid cooling plate is connected to the return pipe so that the coolant can flow through the second liquid cooling plate and return to the liquid cooling unit.

2. The energy storage system according to claim 1, characterized in that, The battery pack is provided in multiple ways, and the first liquid cooling plate is provided in a one-to-one correspondence with the battery pack; the liquid outlet pipe is connected to each of the first liquid cooling plates in sequence.

3. The energy storage system according to claim 1, characterized in that, The energy storage converter is located below the battery pack inside the enclosure.

4. The energy storage system according to claim 3, characterized in that, The enclosure includes a battery compartment and an electrical compartment that are isolated from each other. The battery pack is located in the battery compartment, while the energy storage converter and / or the liquid cooling unit is located in the electrical compartment.

5. The energy storage system according to claim 1, characterized in that, The inner diameter of the return liquid pipeline is larger than the inner diameter of the inner pipeline of the second liquid cooling plate.

6. The energy storage system according to claim 1, characterized in that, An electric reversing valve is installed on the return pipeline. The electric reversing valve is provided with a first outlet and a second outlet. The first outlet is connected to the liquid inlet of the second liquid cooling plate. The second outlet and the liquid outlet of the second liquid cooling plate are both connected to the return port of the liquid cooling unit through pipelines.

7. The energy storage system according to any one of claims 1-6, characterized in that, Temperature sensors are installed at both the battery pack and the energy storage converter. The temperature sensors are electrically connected to a control module, which is electrically connected to the liquid chiller unit to achieve automatic control of the liquid chiller unit.

8. A cooling method for an energy storage system, characterized in that, The application of the energy storage system as described in any one of claims 1-7 includes the following steps: Turn on the liquid cooling unit; Control the flow of liquid into the first liquid cooling plate to cool or heat the battery pack; The liquid discharged from the first liquid cooling plate is controlled to flow into the second liquid cooling plate to cool the energy storage converter; Control the return of coolant from the second liquid cooling plate to the liquid cooling unit; Control the liquid cooling unit to stop, or repeat the above steps to achieve cyclic operation.

9. The cooling method for the energy storage system according to claim 8, characterized in that, Before starting the liquid-cooled unit, the cooling method further includes: Monitor the temperature of the battery pack and energy storage converter; Determine whether to start the liquid cooling unit based on the temperature of the battery pack and energy storage converter; The conditions for determining whether to start the liquid cooling unit are: the temperature of the battery pack is as low as the low temperature threshold or exceeds the high temperature threshold, or the temperature of the energy storage converter exceeds the high temperature threshold.

10. The cooling method for the energy storage system according to claim 8, characterized in that, Before starting the liquid-cooled unit, the cooling method further includes: Monitor the temperature of the battery pack and energy storage converter; Adjust the operating status of the electric reversing valve according to the temperature of the battery pack and energy storage converter; The electric reversing valve has at least two operating states: connected to the second liquid cooling plate and disconnected from the second liquid cooling plate.

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