Energy storage system, control method for energy storage system, and storage medium

Abstract

The present application provides an energy storage system, a control method for an energy storage system, and a storage medium. The energy storage system (10) is connected to a power grid (20). The energy storage system (10) comprises: a battery module (11), the voltage range of the battery module (11) being between a first voltage and a second voltage; and an energy storage converter (12), the energy storage converter (12) being separately connected to the battery module (11) and the power grid (20). The energy storage system (10) is used for adjusting the voltage range of the energy storage converter (12) from an initial voltage range to a target voltage range.

Description

An energy storage system, a control method for the energy storage system, and a storage medium.

[0001] This application claims priority to Chinese Patent Application No. 202411930446.4, filed with the Chinese Patent Office on December 25, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of energy storage technology, specifically to an energy storage system, a control method for the energy storage system, and a storage medium. Background Technology

[0003] Energy storage systems are systems capable of storing electrical energy and releasing it when needed. They play a crucial role in power systems, improving energy efficiency, balancing supply and demand, providing backup power, supporting the integration of renewable energy sources, and enhancing grid stability and reliability. Energy storage converters are a vital component of energy storage systems, serving as a bridge connecting the energy storage system to the power grid. Technical issues

[0004] Electrochemical energy storage, as an important resource in the construction of new power systems, is applied to battery modules in energy storage systems. However, due to the wide voltage range of battery modules, their voltage range cannot be matched with that of energy storage converters. Related technologies attempt to match the battery module's voltage range to the energy storage converter by either increasing or decreasing its discharge cut-off voltage. However, this method sacrifices some of the battery module's capacity, thus reducing the energy utilization rate of the energy storage system. Technical solutions

[0005] In a first aspect, this application provides an energy storage system connected to the power grid, the energy storage system comprising:

[0006] The battery module has a voltage range between a first voltage and a second voltage, where the second voltage is greater than the first voltage.

[0007] The energy storage converter has its first terminal connected to the battery module and its second terminal connected to the power grid. The initial voltage range of the energy storage converter is between the initial lower limit voltage and the initial upper limit voltage, where the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage.

[0008] The energy storage system is used to adjust the voltage range of the energy storage converter from an initial voltage range to a target voltage range so that the target voltage range matches the voltage range of the battery module. The target voltage range is between a target lower voltage limit and a target upper voltage limit, where the target lower voltage limit is less than or equal to a first voltage and the target upper voltage limit is greater than or equal to a second voltage.

[0009] Secondly, this application provides a control method for an energy storage system connected to the power grid. The energy storage system includes a battery module and an energy storage converter. The voltage range of the battery module is between a first voltage and a second voltage, where the second voltage is greater than the first voltage. A first terminal of the energy storage converter is connected to the battery module, and a second terminal of the energy storage converter is connected to the power grid. The method includes:

[0010] In response to the adjustment command, the initial voltage range of the energy storage converter is obtained, wherein the initial voltage range of the energy storage converter is between the initial lower limit voltage and the initial upper limit voltage, and the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage;

[0011] Based on a preset adjustment strategy, the voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range so that the target voltage range matches the voltage range of the battery module. The target voltage range is between the target lower limit voltage and the target upper limit voltage, the target lower limit voltage is less than or equal to the first voltage, and the target upper limit voltage is greater than or equal to the second voltage.

[0012] Thirdly, this application provides a computer-readable storage medium storing computer program code, which, when run on a computer, implements the steps of the control method for the energy storage system described above. Beneficial effects

[0013] This application provides an energy storage system, a control method for the energy storage system, and a storage medium. The energy storage system is connected to the power grid and includes a battery module and an energy storage converter. The voltage range of the battery module is between a first voltage and a second voltage, where the second voltage is greater than the first voltage. A first terminal of the energy storage converter is connected to the battery module, and a second terminal of the energy storage converter is connected to the power grid. The initial voltage range of the energy storage converter is between an initial lower limit voltage and an initial upper limit voltage, where the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage. The energy storage system is used to adjust the voltage range of the energy storage converter from the initial voltage range to a target voltage range, so that the target lower limit voltage in the target voltage range of the energy storage converter is less than or equal to the first voltage, and the target upper limit voltage is greater than or equal to the second voltage. This allows the adjusted target voltage range of the energy storage converter to cover the voltage range of the battery module, thereby improving the energy utilization rate of the energy storage system. Attached Figure Description

[0014] Figure 1 is a schematic diagram of the first structure of the energy storage system provided in an embodiment of this application;

[0015] Figure 2 is a schematic diagram of a second structure of the energy storage system provided in an embodiment of this application;

[0016] Figure 3 is a schematic diagram of a third structure of the energy storage system provided in an embodiment of this application;

[0017] Figure 4 is a schematic diagram of the fourth structure of the energy storage system provided in the embodiments of this application;

[0018] Figure 5 is a flowchart illustrating the control method of the energy storage system provided in an embodiment of this application. Embodiments of the present invention

[0019] Energy storage converters and battery modules are crucial components of energy storage systems. However, the wide voltage range of battery modules makes it difficult to match the voltage range of the energy storage converter. Related technologies attempt to match the battery module's voltage range with the energy storage converter by either increasing or decreasing its discharge cut-off voltage. However, this method sacrifices some of the battery module's capacity, thus reducing the energy utilization rate of the energy storage system.

[0020] Firstly, this application provides an energy storage system in possible implementations, which will be described in detail below. It should be noted that the order in which the possible implementations are described is not intended to limit the preferred order of the possible implementations.

[0021] It should be noted that an energy storage system may include components such as battery modules, energy storage converters, battery management systems, energy management systems, fire protection systems, and temperature control systems. Among these, the battery module is the core component of the energy storage system, responsible for the actual storage and release of energy; the energy storage converter is responsible for converting the DC power from the battery module into AC power for transmission to the grid and its loads, or rectifying the AC power from the grid into DC power for transmission to the battery module; the battery management module monitors and manages the voltage, current, temperature, and remaining battery power of the battery module, ensuring its safe, reliable, and efficient operation; the energy management system is responsible for the energy scheduling and optimization management of the entire energy storage system, formulating reasonable charging and discharging strategies based on grid demand, electricity price signals, and renewable energy generation to improve the economy and efficiency of the energy storage system; the fire protection system ensures the safety of the energy storage system and prevents fires and other safety accidents; and the temperature control system regulates the operating temperature of the energy storage equipment, maintaining it within a suitable temperature range to improve system performance and extend equipment lifespan.

[0022] Please refer to Figure 1, which is a schematic diagram of a first possible structure of the energy storage system provided in this application. The energy storage system 10 provided in this embodiment is connected to the power grid 20, such as electrically connecting the energy storage system 10 to the power grid 20 to realize power transmission between the energy storage system 10 and the power grid 20. The energy storage system 10 can be an outdoor energy storage device, such as an outdoor energy storage cabinet, which is suitable for industrial and commercial scenarios, microgrids, backup power supplies, and other applications.

[0023] In some possible implementations, the energy storage system 10 may include a battery module 11 and an energy storage converter 12. The voltage range of the battery module 11 may be between a first voltage and a second voltage, where the second voltage is greater than the first voltage. The battery module 11 may be an electrochemical battery module such as a sodium-ion battery module or a lithium-ion battery module. If the battery module 11 is a sodium-ion battery module, it may include multiple sodium-ion battery cells, each with a voltage range between 1.5V and 3.95V.

[0024] The battery module 11 is composed of multiple sodium-ion battery cells connected in series to meet the required voltage and capacity. The voltage range of the battery module 11 is directly proportional to the number of sodium-ion battery cells connected in series. For example, if the battery module 11 includes 100 sodium-ion battery cells connected in series, the voltage range of the battery module 11 is between 150V and 395V, i.e., the first voltage is 150V and the second voltage is 395V. If the battery module 11 includes 400 sodium-ion battery cells connected in series, the voltage range of the battery module 11 is between 600V and 1580V, i.e., the first voltage is 600V and the second voltage is 1580V. It should be noted that the series connection method of the multiple sodium-ion battery cells in the battery module 11 is not specifically limited here and can be set according to the actual situation, such as a 1-in-16-in-series configuration or a 1-in-8-in-series configuration.

[0025] Accordingly, if the battery module 11 is a lithium-ion battery module, then the battery module 11 may include multiple lithium-ion battery cells, each of which has a voltage range between 3.0V and 4.2V. In contrast, due to the potential changes caused by the electrochemical reaction between the electrode material and the electrolyte during the charging and discharging process of sodium-ion battery cells, the voltage range of sodium-ion battery cells is wider than that of lithium-ion battery cells.

[0026] It should be noted that the energy storage converter, acting as a bridge between the battery module and the power grid, can rectify the AC power from the grid into DC power for transmission to the battery module, and can also invert the DC power from the battery module into AC power for transmission to the grid and its loads. Therefore, in order for the battery module and the energy storage converter to operate normally, the voltage range of the energy storage converter needs to be compatible with the voltage range of the battery module. That is, the voltage range of the battery module should be within the voltage range that the energy storage converter can accept. This ensures the sufficiency and efficiency of the power conversion between the battery module and the grid, and also ensures the safety and stability of the battery module during charging and discharging, avoiding damage to the battery module due to excessively high or low voltage.

[0027] The voltage range of energy storage converters is typically between 600V and 1000V, or between 1000V and 1500V. If the battery module is a lithium-ion battery module, since the voltage range of a single lithium-ion battery cell is between 3.0V and 4.2V, if the battery module includes 200 lithium-ion battery cells connected in series, the voltage range of the battery module is between 600V and 840V. In this case, an energy storage converter with a voltage range between 600V and 1000V can cover the voltage range of the battery module. If the battery module includes 350 lithium-ion battery cells connected in series, the voltage range of the battery module is between 1050V and 1470V. In this case, an energy storage converter with a voltage range between 1000V and 1500V can cover the voltage range of the battery module. It is understandable that if the battery module is a lithium-ion battery module, since the voltage range of a single lithium-ion battery cell is relatively narrow, the voltage range of the energy storage converter can cover the voltage range of the battery module. Under the condition that the battery module is fully discharged and the voltage range of the energy storage converter is not adjusted, the voltage range of the energy storage converter can still cover the voltage range of the lithium-ion battery module, so that the energy storage converter and the lithium-ion battery module are compatible.

[0028] Conversely, if the battery module is a sodium-ion battery module, since the voltage range of a single sodium-ion battery cell is between 1.5V and 3.95V, and if the battery module includes 400 interconnected lithium-ion battery cells, then the voltage range of the battery module is between 600V and 1580V. In this case, energy storage inverters with voltage ranges between 600V and 1000V or 1000V and 1500V cannot cover the voltage range of the battery module, thus preventing both the battery module and the energy storage inverter from functioning properly. This possible solution addresses the mismatch between the battery module and the energy storage inverter voltage range caused by the wide voltage range of sodium-ion battery cells. While ensuring the sodium-ion battery module can be fully charged and discharged, this solution adjusts the voltage range of the energy storage inverter to match the voltage range of the sodium-ion battery module and the energy storage inverter, ensuring both the battery module and the energy storage inverter can function properly, thereby improving the energy utilization rate of the energy storage system.

[0029] Specifically, the energy storage system 10 includes an energy storage converter 12. The first end of the energy storage converter 12 is connected to the battery module 11, such as an electrical connection. The second end of the energy storage converter 12 is connected to the power grid 20, such as an electrical connection. The initial voltage range of the energy storage converter 12 is between an initial lower limit voltage and an initial upper limit voltage. The initial lower limit voltage is greater than a first voltage or the initial upper limit voltage is less than a second voltage.

[0030] The energy storage converter 12 is positioned between the battery module 11 and the power grid 20. The first end of the energy storage converter 12 is closer to the battery module 11 and further away from the power grid 20. Since the energy storage converter 12 can rectify the AC power from the power grid 20 into DC power and transmit it to the battery module 11, the first end of the energy storage converter 12 can be an AC output terminal on the AC side. The energy storage converter can also invert the DC power from the battery module into AC power and transmit it to the power grid and its loads; therefore, the first end of the energy storage converter 12 can be a DC input terminal on the DC side. Correspondingly, the second end of the energy storage converter 12 is closer to the power grid 20 and further away from the battery module 11. The second end of the energy storage converter 12 can be an AC input terminal on the AC side and a DC output terminal on the DC side.

[0031] The initial voltage range of the energy storage converter 12 is the voltage range before adjustment. For example, the initial voltage range can be between 600V and 1000V or between 1000V and 1500V. This initial voltage range can be adapted to the lithium-ion battery module. However, since the voltage range of the sodium-ion battery module is wider, this initial voltage range is not compatible with the voltage range of the lithium-ion battery module. In this possible implementation, the battery module 11 is a sodium-ion battery module. The voltage range of the battery module 11 is between a first voltage and a second voltage. Since the initial voltage range is not compatible with the voltage range of the lithium-ion battery module, the initial lower limit voltage of the initial voltage range is greater than the first voltage of the battery module 11, or the initial upper limit voltage is less than the second voltage of the battery module 11. For example, if the voltage range of the battery module 11 is between 600V and 1580V, the initial lower limit voltage can be 1000V, which is greater than the first voltage of the battery module 11 (600V); or the initial upper limit voltage can be 1500V, which is less than the second voltage of the battery module 11 (1580V).

[0032] Understandably, in order to ensure that the voltage range of the energy storage converter 12 covers the voltage range of the battery module 11, this possible implementation adjusts the voltage range of the energy storage converter 12 from an initial voltage range to a target voltage range, so that the target voltage range matches the voltage range of the battery module 11. Specifically, the target voltage range is between a target lower voltage limit and a target upper voltage limit, where the target lower voltage limit is less than or equal to a first voltage, and the target upper voltage limit is greater than or equal to a second voltage. For example, if the lower limit voltage of the energy storage converter 12 is adjusted from the initial lower limit voltage of 1000V to the target lower limit voltage of 600V, then the target lower limit voltage is equal to the first voltage of the battery module 11, 600V; if the upper limit voltage of the energy storage converter 12 is adjusted from the initial upper limit voltage of 1500V to the target upper limit voltage of 1600V, then the target upper limit voltage is greater than the second voltage of the battery module 11, 1580V. This allows the target voltage range of 600V-1500V to cover the voltage range of the battery module 11, 600V-1580V, so that the voltage range of the battery module 11 matches the target voltage range of the energy storage converter 12. Under fully discharged conditions, the battery module 11 and the energy storage converter 12 can be guaranteed to work normally, thereby improving the energy utilization rate of the energy storage system 10.

[0033] In some possible implementations, the operating voltage range of a single sodium-ion battery cell can typically be less than 1.5V-3.95V. For example, the voltage range of a single sodium-ion battery cell can be 1.5V-3.75V. If the battery module 11 consists of 400 sodium-ion battery cells connected in series, then the voltage range of the battery module 11 is between 600V and 1500V, i.e., the first voltage is 600V and the second voltage is 1500V. In this case, since the initial upper limit voltage of the energy storage converter 12, 1500V, is equal to the second voltage, and the initial lower limit voltage, 1000V, is greater than the first voltage, 600V, when adjusting the voltage range of the energy storage converter 12, only the lower limit voltage needs to be adjusted, without adjusting the upper limit voltage. That is, the initial lower limit voltage of 1000V is adjusted to the target lower limit voltage of 600V, while the initial upper limit voltage of 1500V is equal to the target upper limit voltage of 1500V, thereby improving the adjustment efficiency of the energy storage converter 12. Of course, it is also possible to adjust only the initial upper limit voltage without adjusting the initial lower limit voltage. The specific adjustment strategy needs to be set according to the initial voltage range and the voltage range of the battery module 12, and is not specifically limited here. The voltage range of the battery module 12 is related to the voltage range of its internal sodium-ion battery cells and the number of sodium-ion battery cells.

[0034] In some possible implementations, the energy storage system 20 may also include a control module that is electrically connected to the energy storage converter 12, or the control module may be located inside the energy storage converter 12. The control module may be used to adjust the voltage range of the energy storage converter 12 from the initial voltage range to the target voltage range based on parameter adjustment strategies and / or mode adjustment strategies.

[0035] Optionally, using parameter adjustment strategies as an example, if the voltage range of the battery module 11 is 600V-1580V and the initial voltage range of the energy storage converter 12 is 1000V-1500V, then the internal control algorithm of the energy storage converter 12 is adjusted to change its voltage control strategy, enabling it to adapt to input voltages below 1000V or above 1500V. The energy storage converter 12 can still operate normally and output a stable current when it detects an input voltage below 1000V or above 1500V. For example, the minimum and maximum operating voltage values ​​set internally by the energy storage converter 12 are lowered, i.e., the voltage range of the energy storage converter 12 is adjusted to the target voltage range, allowing it to accept the input voltage of the battery module 11. Simultaneously, the settings of other relevant parameters of the energy storage converter 12, such as current or power, are adjusted to match the target voltage range to ensure the normal operation and safety of the energy storage converter 12.

[0036] Optionally, using a mode adjustment strategy, if the voltage range of battery module 11 is 600V-1580V and the initial voltage range of energy storage converter 12 is 1000V-1500V, then if the input voltage of battery module 11 is within the initial voltage range, the output power of energy storage converter 12 is the rated power, and the operating mode of energy storage converter 12 is the normal operating mode. If the input voltage of battery module 11 is not within the initial voltage range, then by reducing or increasing the output power of energy storage converter 12, the operating mode of energy storage converter 12 is adjusted to a derating operating mode or a scaling operating mode. Specifically, by dynamically adjusting the operating mode of the energy storage converter 12 by acquiring the input voltage of the energy storage converter 12 in real time, the target voltage range can be made to cover the voltage range of the battery module 11 to ensure the normal operation of both the energy storage converter 12 and the battery module 11. In the real-time monitoring of the energy storage converter 12, it can be ensured that faults such as voltage abnormality, overload, and overheating are detected in a timely manner during the operation of the energy storage converter 12 in derating or maximizing operating modes, and corresponding protection measures are taken in a timely manner, such as reducing the output power and starting the cooling system, to ensure the safe operation of the energy storage converter 12.

[0037] As can be seen from the above, the energy storage system 10 provided by this possible implementation includes a battery module 11 and an energy storage converter 12. The voltage range of the battery module 11 is between a first voltage and a second voltage, where the second voltage is greater than the first voltage. The first terminal of the energy storage converter 12 is connected to the battery module 11, and the second terminal of the energy storage converter 12 is connected to the power grid 20. The initial voltage range of the energy storage converter 12 is between an initial lower limit voltage and an initial upper limit voltage, where the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage. The energy storage system 10 is used to adjust the voltage range of the energy storage converter 12 from the initial voltage range to the target voltage range, so that the target lower limit voltage in the target voltage range of the energy storage converter 12 is less than or equal to the first voltage, and the target upper limit voltage is greater than or equal to the second voltage. This allows the adjusted target voltage range of the energy storage converter 12 to cover the voltage range of the battery module 11 without sacrificing the battery module's capacity to meet the voltage range matching requirements of the energy storage converter, thus improving the energy utilization rate of the energy storage system.

[0038] It should be noted that the second terminal of the energy storage converter 12 of the energy storage system 10, namely the DC output terminal or AC input terminal, is a three-phase three-wire system. A three-phase three-wire circuit includes three phase lines but no neutral line. It can only provide line voltage but not phase voltage. It is suitable for three-phase symmetrical loads but not for single-phase loads. However, the application scenarios of energy storage systems, such as outdoor energy storage cabinets, are mostly industrial and commercial energy storage, photovoltaic energy storage and charging, etc. In these application scenarios, the load types are diverse. There are three-phase symmetrical loads such as large machinery and air conditioning systems, as well as single-phase loads such as lighting and sockets. The three-phase three-wire system cannot provide the phase voltage required by single-phase loads, such as 220V, and therefore cannot meet the power demand of single-phase loads.

[0039] Furthermore, if the three-phase three-wire connection at the second terminal of the energy storage converter 12 is directly connected to the power grid, there will be an electrical connection between the power grid's grounding system and the battery module 11. The power grid's grounding system will interfere with the insulation detection of the battery module 11, causing abnormal current in the detection circuit and rendering the insulation detection function of the battery module 11 ineffective. During the operation of the energy storage system, the insulation resistance will be very low. If a DC-to-ground short circuit occurs, the short circuit current will flow back to the battery module through the power grid's grounding system, forming a short circuit loop, which is quite dangerous. Harmonics from the power grid or load will affect the normal operation of the battery module or the energy storage system. When the harmonics are severe, they will affect the sampling of the battery management system of the energy storage system, causing deviations and making it impossible for the battery management system to accurately determine the status of the battery module. Therefore, the three-phase three-wire connection at the second terminal of the energy storage converter 12 is not suitable for energy storage systems such as outdoor energy storage cabinets.

[0040] Since directly connecting a three-phase, three-wire energy storage converter to the power grid may cause some adverse effects, this possible implementation adds an isolation transformer between the energy storage converter and the power grid, so that the connection side of the energy storage system to the power grid is a three-phase, four-wire system. Specifically, please refer to Figure 2, which is a schematic diagram of a second structural design of the energy storage system provided by this possible implementation. The energy storage system 10 may also include an isolation transformer 13, which is disposed between the energy storage converter 12 and the power grid 20. Specifically, the first end of the isolation transformer 13 is connected to the second end of the energy storage converter 12, such as an electrical connection, and the second end of the isolation transformer 13 is connected to the power grid 20, such as an electrical connection.

[0041] The second terminal of the energy storage converter 12 is a three-phase three-wire system, meaning it has three phase wires. The second terminal of the isolation transformer 13 is a three-phase four-wire system, meaning it has one neutral wire and three phase wires. The isolation transformer 13 is used to convert the three-phase three-wire system at the second terminal of the energy storage converter 12 to a three-phase four-wire system at the second terminal of the isolation transformer 13.

[0042] Optionally, the isolation transformer 13 can be a Dyn11 type isolation transformer, where Dyn11 represents the connection method and phase relationship of the isolation transformer windings. D indicates that the high-voltage winding adopts a delta connection method. The delta connection winding can provide better resistance to lightning impulses and will not generate zero-sequence current in the event of a single-phase ground fault, which is beneficial to the protection of the energy storage system 10. y indicates that the low-voltage winding adopts a star connection method. The star connection winding can provide a neutral point, which is convenient for leading out the neutral line of the isolation transformer and is suitable for occasions that require phase voltage. n indicates that the neutral point of the low-voltage winding is directly grounded. This grounding method helps to stabilize the voltage on the low-voltage side and improve the safety and reliability of the energy storage system 10. 11 represents the phase relationship between the high-voltage winding and the low-voltage winding, that is, the voltage phasor of the low-voltage winding lags behind the voltage phasor of the high-voltage winding by 330° or leads by 30°. This phase relationship helps to reduce the influence of harmonics.

[0043] It should be noted that a three-phase four-wire system can provide both line voltage and phase voltage simultaneously, meeting the power requirements of both three-phase and single-phase loads. It is suitable for both symmetrical and asymmetrical loads. By introducing a neutral line, the adverse effects of voltage fluctuations and power quality can be effectively reduced, improving system stability and the operational reliability of the energy storage system. Furthermore, the neutral line can provide a current loop to balance the three-phase load, enhancing the safety and reliability of the energy storage system. Since the application scenarios of energy storage systems 10, such as outdoor energy storage cabinets, are mostly industrial and commercial energy storage, photovoltaic energy storage and charging, etc., and the loads include both three-phase and single-phase loads, by setting the connection side of the energy storage system 10 to the grid 20 as a three-phase four-wire system, that is, by converting the three-phase three-wire system at the second end of the energy storage converter 12 to a three-phase four-wire system at the second end of the isolation transformer 13, the power requirements of both three-phase and single-phase loads in industrial and commercial energy storage, photovoltaic energy storage and charging scenarios can be met.

[0044] In some possible implementations, since the isolation transformer 13 is located between the battery module 11 and the power grid 20, if the DC positive / negative terminals of the battery module are short-circuited to ground, the isolation transformer 13 can interrupt the circuit, ensuring that the short circuit in the energy storage system 10 will not affect the power grid 20. Conversely, a short circuit in the power grid 20 will also be blocked by the isolation transformer 13 and will not affect the energy storage system 10. Furthermore, since the input and output terminals of the isolation transformer 13 are completely isolated, the voltage at the input terminal will not affect the output terminal, thereby reducing the risk of electric shock and making the energy storage system 10 safer. The isolation transformer 13 can also effectively prevent personal injury caused by accidents such as leakage and electric shock.

[0045] In some possible implementations, the isolation transformer 13 can isolate harmonics generated by the power grid or load to prevent the energy storage system 10 from being subjected to electromagnetic interference, reduce the impact of electromagnetic compatibility on the energy storage system, enable the battery module or energy storage system to work normally, thereby improving the sampling accuracy of the battery management module and improving the accuracy of the state judgment of the battery module.

[0046] Please refer to Figure 3, which is a schematic diagram of a third possible structure of the energy storage system provided in this application. The energy storage system 10 may further include a load 14, which is connected to the second terminal of an isolation transformer 13. The isolation transformer 13 is used to transmit the output voltage of the battery module 11 to the load 14. The three-phase four-wire configuration of the second terminal of the isolation transformer 13 includes one neutral line and three phase lines. The load 14 is connected to the neutral line and one of the phase lines of the second terminal of the isolation transformer 13, so that the output voltage of the battery module 11 can be transmitted to the load 14 after passing through the isolation transformer 13.

[0047] It should be noted that the isolation transformer 13 not only converts the three-phase three-wire system at the second end of the energy storage converter 12 into a three-phase four-wire system at the second end of the isolation transformer 13 so that the energy storage system 10 can be connected to the power grid, but also, due to the neutral line, the second end of the isolation transformer 13 can be connected to the load 14. The isolation transformer 13 is used to transmit the output voltage of the battery module 11 to the load 14, so that the load 14 can receive power from both the power grid 20 and the battery module 11. If the power grid 20 fails and cannot supply power to the load 14, the load 14 can be powered by the discharge of the battery module 11 of the energy storage system 10, so as to ensure the normal operation of the load 14 and improve the safety and economy of the energy storage system 10.

[0048] In some possible implementations, please refer to Figure 4, which is a schematic diagram of a fourth structure of the energy storage system provided by a possible implementation of this application. The load 14 may include devices such as an uninterruptible power supply (UPS) 141 and a liquid chiller 142. A UPS is a device capable of providing a continuous and stable power supply. The UPS not only stabilizes the voltage in the energy storage system 10 when voltage instability occurs, but also provides uninterrupted power protection for important loads in the energy storage system 10, such as the battery management system and fire protection system, when the mains power is interrupted. The liquid chiller 142 ensures that the battery cells of the battery module 11 operate within a suitable temperature range, thereby improving the service life of the battery module 11 and the operating efficiency of the energy storage system 10.

[0049] In addition, the energy storage system 10 may also include a high-voltage box 15, which is disposed between the battery module 11 and the energy storage inverter 12. Specifically, the first end of the high-voltage box 15 is connected to the second end of the battery module 11, and the second end of the high-voltage box 15 is connected to the first end of the energy storage inverter 12. The high-voltage box 15 can realize functions such as charging and discharging control, protection, and monitoring of the energy storage system 10. Through its control and protection functions, the high-voltage box 15 can effectively prevent electrical faults and safety accidents from occurring in the energy storage system 10 during operation, ensuring the safety and reliability of the energy storage system 10.

[0050] Secondly, a possible implementation of this application also provides a control method for an energy storage system. Please refer to Figure 5, which is a flowchart illustrating the control method for the energy storage system provided in a possible implementation of this application. The energy storage system is connected to the power grid and may include battery modules and an energy storage converter. The voltage range of the battery modules is between a first voltage and a second voltage, where the second voltage is greater than the first voltage. The first terminal of the energy storage converter is connected to the battery modules, and the second terminal of the energy storage converter is connected to the power grid. The specific flow of the control method for this energy storage system can be as follows:

[0051] 101. In response to the adjustment command, obtain the initial voltage range of the energy storage converter, wherein the initial voltage range of the energy storage converter is between the initial lower limit voltage and the initial upper limit voltage, and the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage.

[0052] The voltage range of energy storage converters is typically between 600V and 1000V, or between 1000V and 1500V. If the battery module is a sodium-ion battery module, since the voltage range of a single sodium-ion battery cell is between 1.5V and 3.95V, and if the battery module includes 400 lithium-ion battery cells connected in series, then the voltage range of the battery module is between 600V and 1580V. In this case, energy storage converters with voltage ranges between 600V and 1000V, or between 1000V and 1500V, cannot cover the voltage range of the battery module, thus preventing both the battery module and the energy storage converter from functioning properly. Because the wide voltage range of sodium-ion battery cells leads to a mismatch between the voltage range of the battery module and the voltage range of the energy storage inverter, this possible solution, while ensuring that the sodium-ion battery module can be fully charged and discharged, adjusts the voltage range of the energy storage inverter to make the voltage range of the sodium-ion battery module and the voltage range of the energy storage inverter compatible, thereby ensuring that the battery module and the energy storage inverter can work normally and thus improving the energy utilization rate of the energy storage system.

[0053] The initial voltage range of the energy storage converter 12 is the voltage range before adjustment. For example, the initial voltage range can be between 600V and 1000V or between 1000V and 1500V. Since the voltage range of the sodium-ion battery module is relatively wide, the initial voltage range is not compatible with the voltage range of the lithium-ion battery module. Therefore, the voltage range of the energy storage converter needs to be adjusted. Specifically, in response to the adjustment command, the initial voltage range of the energy storage converter is obtained. The voltage range of the battery module 11 is between the first voltage and the second voltage. Since the initial voltage range does not match the voltage range of the lithium-ion battery module, the initial lower limit voltage of the initial voltage range is greater than the first voltage of the battery module 11 or the initial upper limit voltage is less than the second voltage of the battery module 11. For example, if the voltage range of the battery module 11 is between 600V and 1580V, the initial lower limit voltage can be 1000V, which is greater than the first voltage of the battery module 11 (600V); or the initial upper limit voltage can be 1500V, which is less than the second voltage of the battery module 11 (1580V).

[0054] 102. Based on a preset adjustment strategy, the voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range so that the target voltage range matches the voltage range of the battery module. The target voltage range is between the target lower limit voltage and the target upper limit voltage, the target lower limit voltage is less than or equal to the first voltage, and the target upper limit voltage is greater than or equal to the second voltage.

[0055] Understandably, in order to ensure that the voltage range of the energy storage converter 12 covers the voltage range of the battery module 11, this possible implementation adjusts the voltage range of the energy storage converter 12 from an initial voltage range to a target voltage range, so that the target voltage range matches the voltage range of the battery module 11. Specifically, the target voltage range is between a target lower voltage limit and a target upper voltage limit, where the target lower voltage limit is less than or equal to a first voltage, and the target upper voltage limit is greater than or equal to a second voltage. For example, if the lower limit voltage of the energy storage converter 12 is adjusted from the initial lower limit voltage of 1000V to the target lower limit voltage of 600V, then the target lower limit voltage is equal to the first voltage of the battery module 11, 600V; if the upper limit voltage of the energy storage converter 12 is adjusted from the initial upper limit voltage of 1500V to the target upper limit voltage of 1600V, then the target upper limit voltage is greater than the second voltage of the battery module 11, 1580V. This allows the target voltage range of 600V-1500V to cover the voltage range of the battery module 11, 600V-1580V, so that the voltage range of the battery module 11 matches the target voltage range of the energy storage converter 12. Under fully discharged conditions, the battery module 11 and the energy storage converter 12 can be guaranteed to work normally, thereby improving the energy utilization rate of the energy storage system 10.

[0056] In some possible implementations, the operating voltage range of a single sodium-ion battery cell can typically be less than 1.5V-3.95V. For example, the voltage range of a single sodium-ion battery cell can be 1.5V-3.75V. If the battery module 11 consists of 400 sodium-ion battery cells connected in series, then the voltage range of the battery module 11 is between 600V and 1500V, i.e., the first voltage is 600V and the second voltage is 1500V. In this case, since the initial upper limit voltage of the energy storage converter 12, 1500V, is equal to the second voltage, and the initial lower limit voltage, 1000V, is greater than the first voltage, 600V, when adjusting the voltage range of the energy storage converter 12, only the lower limit voltage needs to be adjusted, without adjusting the upper limit voltage. That is, the initial lower limit voltage of 1000V is adjusted to the target lower limit voltage of 600V, while the initial upper limit voltage of 1500V is equal to the target upper limit voltage of 1500V, thereby improving the adjustment efficiency of the energy storage converter 12. Of course, it is also possible to adjust only the initial upper limit voltage without adjusting the initial lower limit voltage. The specific adjustment strategy needs to be set according to the initial voltage range and the voltage range of the battery module 12, and is not specifically limited here. The voltage range of the battery module 12 is related to the voltage range of its internal sodium-ion battery cells and the number of sodium-ion battery cells.

[0057] In some possible implementations, the voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range based on parameter adjustment strategies and / or mode adjustment strategies.

[0058] Optionally, using parameter adjustment strategies as an example, if the voltage range of the battery module 11 is 600V-1580V and the initial voltage range of the energy storage converter 12 is 1000V-1500V, then the internal control algorithm of the energy storage converter 12 is adjusted to change its voltage control strategy, enabling it to adapt to input voltages below 1000V or above 1500V. The energy storage converter 12 can still operate normally and output a stable current when it detects an input voltage below 1000V or above 1500V. For example, the minimum and maximum operating voltage values ​​set internally by the energy storage converter 12 are lowered, i.e., the voltage range of the energy storage converter 12 is adjusted to the target voltage range, allowing it to accept the input voltage of the battery module 11. Simultaneously, the settings of other relevant parameters of the energy storage converter 12, such as current or power, are adjusted to match the target voltage range to ensure the normal operation and safety of the energy storage converter 12.

[0059] Optionally, using a mode adjustment strategy, if the voltage range of battery module 11 is 600V-1580V and the initial voltage range of energy storage converter 12 is 1000V-1500V, then if the input voltage of battery module 11 is within the initial voltage range, the output power of energy storage converter 12 is the rated power, and the operating mode of energy storage converter 12 is the normal operating mode. If the input voltage of battery module 11 is not within the initial voltage range, then by reducing or increasing the output power of energy storage converter 12, the operating mode of energy storage converter 12 is adjusted to a derating operating mode or a scaling operating mode. Specifically, by dynamically adjusting the operating mode of the energy storage converter 12 by acquiring the input voltage of the energy storage converter 12 in real time, the target voltage range can be made to cover the voltage range of the battery module 11 to ensure the normal operation of both the energy storage converter 12 and the battery module 11. In the real-time monitoring of the energy storage converter 12, it can be ensured that faults such as voltage abnormality, overload, and overheating are detected in a timely manner during the operation of the energy storage converter 12 in derating or maximizing operating modes, and corresponding protection measures are taken in a timely manner, such as reducing the output power and starting the cooling system, to ensure the safe operation of the energy storage converter 12.

[0060] As can be seen from the above, a possible implementation of this application obtains the initial voltage range of the energy storage converter in response to an adjustment command, and adjusts the voltage range of the energy storage converter from the initial voltage range to the target voltage range based on a preset adjustment strategy, so that the target voltage range matches the voltage range of the battery module. This possible implementation adjusts the voltage range of the energy storage converter to the target voltage range, making the target lower limit voltage of the energy storage converter less than or equal to the first voltage of the battery module, and the target upper limit voltage of the energy storage converter greater than or equal to the second voltage of the battery module. Thus, the adjusted target voltage range of the energy storage converter covers the voltage range of the battery module, improving the energy utilization rate of the energy storage system.

[0061] Those skilled in the art will understand that all or part of the steps in the various methods of the above possible implementations can be accomplished by instructions, or by instructions controlling related hardware, which can be stored in a computer-readable storage medium and loaded and executed by a processor.

[0062] Thirdly, a possible implementation of this application provides a computer-readable storage medium storing computer program code. When the computer program code is executed on a computer, it causes the computer to perform the aforementioned method steps to implement the control method for an energy storage system provided by the possible implementation. The computer-readable storage medium can be non-volatile or volatile. For example, the following steps can be specifically executed:

[0063] In response to the adjustment command, the initial voltage range of the energy storage converter is obtained, wherein the initial voltage range of the energy storage converter is between the initial lower limit voltage and the initial upper limit voltage, and the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage;

[0064] Based on a preset adjustment strategy, the voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range so that the target voltage range matches the voltage range of the battery module. The target voltage range is between the target lower limit voltage and the target upper limit voltage, the target lower limit voltage is less than or equal to the first voltage, and the target upper limit voltage is greater than or equal to the second voltage.

[0065] For details on the specific implementation of each of the above operations, please refer to the possible implementation methods mentioned above, which will not be repeated here.

[0066] The storage medium may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

Claims

1. An energy storage system, the energy storage system being connected to a power grid, the energy storage system comprising: A battery module, wherein the voltage range of the battery module is between a first voltage and a second voltage, wherein the second voltage is greater than the first voltage; An energy storage converter, wherein a first terminal of the energy storage converter is connected to the battery module, a second terminal of the energy storage converter is connected to the power grid, and the initial voltage range of the energy storage converter is between an initial lower limit voltage and an initial upper limit voltage, wherein the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage; The energy storage system is used to adjust the voltage range of the energy storage converter from the initial voltage range to a target voltage range so that the target voltage range matches the voltage range of the battery module, wherein the target voltage range is between a target lower voltage limit and a target upper voltage limit, the target lower voltage limit is less than or equal to the first voltage, and the target upper voltage limit is greater than or equal to the second voltage.

2. The energy storage system according to claim 1, further comprising an isolation transformer, wherein the isolation transformer is disposed between the energy storage converter and the power grid, wherein a first end of the isolation transformer is connected to a second end of the energy storage converter, and the second end of the isolation transformer is connected to the power grid.

3. The energy storage system according to claim 2, wherein, The second terminal of the energy storage converter is a three-phase three-wire system, and the second terminal of the isolation transformer is a three-phase four-wire system; The isolation transformer is used to convert the three-phase three-wire system at the second end of the energy storage converter into a three-phase four-wire system at the second end of the isolation transformer.

4. The energy storage system according to claim 3, the energy storage system further includes a load, the load being connected to the second end of the isolation transformer, the isolation transformer being used to transmit the output voltage of the battery module to the load.

5. The energy storage system according to claim 4, wherein, The three-phase four-wire system at the second end of the isolation transformer includes one neutral line and three phase lines, and the load is connected to the neutral line and one of the phase lines at the second end of the isolation transformer.

6. The energy storage system according to claim 1, further comprising a control module, the control module being configured to adjust the voltage range of the energy storage converter from the initial voltage range to the target voltage range based on a parameter adjustment strategy and / or a mode adjustment strategy.

7. The energy storage system according to claim 1, wherein, The battery module is a sodium-ion battery module, which includes multiple sodium-ion battery cells, each of which has a voltage range between 1.5V and 3.95V.

8. The energy storage system according to any one of claims 2 to 5, wherein, The isolation transformer is a Dyn11 type isolation transformer.

9. A control method for an energy storage system, the energy storage system being connected to a power grid, the energy storage system comprising a battery module and an energy storage converter, wherein the voltage range of the battery module is between a first voltage and a second voltage, the second voltage being greater than the first voltage; The first terminal of the energy storage converter is connected to the battery module, and the second terminal of the energy storage converter is connected to the power grid. The method includes: In response to an adjustment command, the initial voltage range of the energy storage converter is obtained, wherein the initial voltage range of the energy storage converter is between an initial lower limit voltage and an initial upper limit voltage, and the initial lower limit voltage is greater than the first voltage or the initial upper limit voltage is less than the second voltage; Based on a preset adjustment strategy, the voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range so that the target voltage range matches the voltage range of the battery module. The target voltage range is between the target lower limit voltage and the target upper limit voltage, the target lower limit voltage is less than or equal to the first voltage, and the target upper limit voltage is greater than or equal to the second voltage.

10. The control method for an energy storage system according to claim 9, wherein, The step of adjusting the voltage range of the energy storage converter from the initial voltage range to the target voltage range based on a preset adjustment strategy, so that the target voltage range matches the voltage range of the battery module, includes: The voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range based on parameter adjustment strategies and / or mode adjustment strategies.

11. A computer-readable storage medium storing computer program code that, when the computer program is run on a computer, implements the steps of the control method for the energy storage system as described in claim 9 or 10.

Images