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

Abstract

The invention provides an energy storage system, a control method of the energy storage system and a storage medium, the energy storage system is connected with a power grid, the energy storage system comprises a battery module, the voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage; a first end of the energy storage converter is connected with the battery module, a second end of the energy storage converter is connected with a power grid, an 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 smaller than the second voltage; the energy storage system is used for adjusting the voltage range of the energy storage converter from an initial voltage range to a target voltage range, so that the target voltage range is matched with the voltage range of the battery module, the target voltage range is between a target lower limit voltage and a target upper limit voltage, and the target lower limit voltage is smaller than or equal to the first voltage; the target upper limit voltage is greater than or equal to the second voltage. The target voltage range adjusted by the energy storage converter can cover the voltage range of the battery module, and the energy utilization rate of the energy storage system is improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to an energy storage system, a control method for the energy storage system, and a storage medium. Background Art

[0002] Energy storage systems are systems that can store electrical energy and release it when needed. Energy storage systems play a vital role in power systems, improving energy efficiency, balancing supply and demand, providing backup power, supporting the integration of renewable energy, and enhancing the stability and reliability of the power grid. Among them, energy storage converters are an important part of energy storage systems and serve as a bridge between energy storage systems and power grids.

[0003] As an important resource in the construction of new power systems, electrochemical energy storage is applied to the battery modules of energy storage systems. However, due to the wide voltage range of the battery modules, their voltage range cannot match the voltage range of the energy storage inverter. In related technologies, the battery modules are matched with the voltage range of the energy storage inverter by increasing the discharge cut-off voltage of the battery modules or reducing the discharge cut-off voltage of the battery modules. However, this method will sacrifice the power of some battery modules, thereby reducing the energy utilization rate of the energy storage system. Summary of the invention

[0004] The present application provides an energy storage system, a control method for the energy storage system, and a storage medium, which improve the energy utilization rate of the energy storage system.

[0005] In a first aspect, the present application provides an energy storage system, wherein the energy storage system is connected to a power grid, and the energy storage system comprises:

[0006] A battery module, wherein a voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage;

[0007] An energy storage converter, wherein a first end of the energy storage converter is connected to the battery module, a second end of the energy storage converter is connected to the power grid, an 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;

[0008] The energy storage system is used to adjust the voltage range of the energy storage inverter from the initial voltage range to the 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 limit voltage and a 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.

[0009] In some embodiments of the present application, the energy storage system also includes an isolation transformer, which is arranged between the energy storage inverter and the power grid, the first end of the isolation transformer is connected to the second end of the energy storage inverter, and the second end of the isolation transformer is connected to the power grid.

[0010] In some embodiments of the present application, the second end of the energy storage converter is a three-phase three-wire system, and the second end of the isolation transformer is a three-phase four-wire system;

[0011] 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.

[0012] In some embodiments of the present application, the energy storage system further includes a load, the load is connected to the second end of the isolation transformer, and the isolation transformer is used to transmit the output voltage of the battery module to the load.

[0013] In some embodiments of the present application, the three-phase four-wire system at the second end of the isolation transformer includes a 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.

[0014] In some embodiments of the present application, the energy storage system further includes a control module, which is used 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.

[0015] In some embodiments of the present application, the battery module is a sodium-ion battery module, and the battery module includes a plurality of sodium-ion battery cells, and a voltage range of each of the sodium-ion battery cells is between 1.5V and 3.95V.

[0016] In some embodiments of the present application, the isolation transformer is a Dyn11 type isolation transformer.

[0017] In a second aspect, the present application provides a control method for an energy storage system, wherein the energy storage system is connected to a power grid, the energy storage system comprises a battery module and an energy storage converter, the voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage; a first end of the energy storage converter is connected to the battery module, and a second end of the energy storage converter is connected to the power grid, the method comprising:

[0018] In response to the adjustment instruction, an initial voltage range of the energy storage converter is acquired, 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;

[0019] Based on a preset adjustment strategy, the voltage range of the energy storage inverter 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, wherein the target voltage range is between a target lower limit voltage and a 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.

[0020] In some embodiments of the present application, 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:

[0021] The voltage range of the energy storage converter is adjusted from the initial voltage range to the target voltage range based on a parameter adjustment strategy and / or a mode adjustment strategy.

[0022] In a third aspect, the present application provides a computer-readable storage medium storing computer program code, which implements the steps of the control method of the energy storage system as described above when the computer program is executed on a computer.

[0023] The present 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 a power grid, and the energy storage system includes a battery module and an energy storage inverter, wherein a voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage; a first end of the energy storage inverter is connected to the battery module, and a second end of the energy storage inverter is connected to the power grid; an initial voltage range of the energy storage inverter 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; the energy storage system is used to adjust the voltage range of the energy storage inverter from the initial voltage range to a target voltage range, so that a target lower limit voltage in the target voltage range of the energy storage inverter is less than or equal to the first voltage, and a target upper limit voltage is greater than or equal to the second voltage, so that the adjusted target voltage range of the energy storage inverter can cover the voltage range of the battery module, thereby improving the energy utilization rate of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a schematic diagram of the first structure of the energy storage system provided in the embodiment of the present application;

[0026] Figure 2 is a second structural schematic diagram of the energy storage system provided in an embodiment of the present application;

[0027] Figure 3 is a third structural schematic diagram of the energy storage system provided in the embodiment of the present application;

[0028] Figure 4 is a fourth structural schematic diagram of the energy storage system provided in the embodiment of the present application;

[0029] Figure 5 It is a flow chart of a control method for an energy storage system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0031] When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Instead, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims.

[0032] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0033] The energy storage inverter and battery module are important components of the energy storage system, but the voltage range of the battery module is wide, which makes it impossible to match the voltage range of the energy storage inverter. In the related art, the discharge cut-off voltage of the battery module is increased or decreased to match the voltage range of the battery module with that of the energy storage inverter, but this method will sacrifice the power of part of the battery module, thereby reducing the energy utilization rate of the energy storage system.

[0034] In order to solve the problems in the related art, the embodiments of the present application provide an energy storage system, which are described in detail below. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments.

[0035] It should be noted that the 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 them, the battery module is the core part of the energy storage system, responsible for the actual energy storage and release; the energy storage converter is responsible for converting the DC power of the battery module into AC power and transmitting it to the power grid and its load, or rectifying the AC power of the power grid into DC power and transmitting it to the battery module; the battery management module is used to monitor and manage the voltage, current, temperature, and remaining battery power of the battery module to ensure the safe, reliable, and efficient operation of the battery module; the energy management system is responsible for the energy scheduling and optimization management of the entire energy storage system, and formulates reasonable charging and discharging strategies based on factors such as power grid demand, electricity price signals, and renewable energy generation to improve the economy and efficiency of the energy storage system; the fire protection system is used to ensure the safety of the energy storage system and prevent the occurrence of safety accidents such as fire; the temperature control system is used to adjust the working temperature of the energy storage equipment to keep it working within a suitable temperature range, improve system performance, and extend equipment life.

[0036] See also Figure 1 , Figure 1 1 is a schematic diagram of the first structure of the energy storage system provided in the embodiment of the present application. The energy storage system 10 provided in the present embodiment is connected to the power grid 20, such as the energy storage system 10 is electrically connected to the power grid 20 to achieve 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 can be suitable for industrial and commercial scenarios, microgrids, backup power supplies and other applications.

[0037] In some embodiments, 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, and 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, the battery module 11 may include a plurality of sodium ion battery cells, and the voltage range of each sodium ion battery cell is between 1.5V and 3.95V.

[0038] Among them, the battery module 11 is composed of multiple sodium ion battery cells connected in series to meet the required voltage and capacity, and the voltage range of the battery module 11 is positively correlated with 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, that is, 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, that is, the first voltage is 600V and the second voltage is 1580V. It should be noted that the series connection method of multiple sodium ion battery cells in the battery module 11 is not specifically limited here, and can be set accordingly according to actual conditions, such as 1 in parallel and 16 in series, 1 in parallel and 8 in series, etc.

[0039] Correspondingly, if the battery module 11 is a lithium-ion battery module, the battery module 11 may include a plurality of lithium-ion battery cells, and the voltage range of each lithium-ion battery cell is between 3.0 V and 4.2 V. Among them, due to the potential change caused by the electrochemical reaction between the electrode material and the electrolyte during the charge and discharge process of the sodium-ion battery cell, the voltage range of the sodium-ion battery cell is wider than that of the lithium-ion battery cell.

[0040] It should be noted that the energy storage inverter, as a bridge connecting the battery module and the power grid, can rectify the AC power of the power grid into DC power and transmit it to the battery module, and can also invert the DC power of the battery module into AC power and transmit it to the power grid and its load. Therefore, in order for the battery module and the energy storage inverter to work normally, the voltage range of the energy storage AC 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 inverter can accept, so as to ensure the adequacy and conversion efficiency of the power conversion between the battery module and the power grid, and also ensure the safety and stability of the battery module during the charging and discharging process, and avoid damage to the battery module due to excessively high or low voltage.

[0041] The voltage range of the energy storage converter is usually between 600V and 1000V, or between 1000V and 1500V. If the battery module is a lithium-ion battery module, since the voltage range of lithium-ion battery cells 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. At this time, the energy storage converter with a voltage range of 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. At this time, the energy storage converter with a voltage range of 1000V and 1500V can cover the voltage range of the battery module. It can be understood that if the battery module is a lithium-ion battery module, since the voltage range of the lithium-ion battery cell is relatively narrow, the voltage range of the energy storage inverter can cover the voltage range of the battery module. While ensuring that the battery module is fully discharged and the voltage range of the energy storage inverter is not adjusted, it can still be ensured that the voltage range of the energy storage inverter covers the voltage range of the lithium-ion battery module, so that the energy storage inverter is compatible with the lithium-ion battery module.

[0042] Correspondingly, if the battery module is a sodium ion battery module, since the voltage range of the sodium ion battery cell is between 1.5V and 3.95V, if the battery module includes 400 lithium ion battery cells connected in series, the voltage range of the battery module is between 600V and 1580V. At this time, the energy storage converter with a voltage range between 600V and 1000V or between 1000V and 1500V cannot cover the voltage range of the battery module, so that the battery module and the energy storage converter cannot work normally. In order to solve the problem that the voltage range of the battery module and the energy storage converter is not compatible due to the wide voltage range of the sodium ion battery cell, this embodiment adjusts the voltage range of the energy storage converter to make the sodium ion battery module and the energy storage converter compatible while ensuring that the sodium ion battery module can be fully charged and discharged, so as to ensure that the battery module and the energy storage converter can work normally, thereby improving the energy utilization rate of the energy storage system.

[0043] Specifically, the energy storage system 10 includes an energy storage inverter 12, a first end of the energy storage inverter 12 is connected to the battery module 11, such as electrically connected, and a second end of the energy storage inverter 12 is connected to the power grid 20, such as electrically connected. The initial voltage range of the energy storage inverter 12 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.

[0044] Among them, the energy storage converter 12 is arranged between the battery module 11 and the power grid 20, and the first end of the energy storage converter 12 is close to the battery module 11 and far away from the power grid 20. Since the energy storage converter 12 can rectify the AC power of 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 end on the AC side; the energy storage converter can also invert the DC power of the battery module into AC power and transmit it to the power grid and its load, so the first end of the energy storage converter 12 can be a DC input end on the DC side. Correspondingly, the second end of the energy storage converter 12 is close to the power grid 20 and far away from the battery module 11. The second end of the energy storage converter 12 can be an AC input end on the AC side and a DC output end on the DC side.

[0045] The initial voltage range of the energy storage inverter 12 is the voltage range before adjustment. For example, the initial voltage range can be between 600V and 1000V or between 1000V and 1500V. The initial voltage range can be compatible with the lithium-ion battery module, but because the voltage range of the sodium-ion battery module is wider, the initial voltage range is not compatible with the voltage range of the lithium-ion battery module. The battery module 11 in this embodiment is a sodium ion battery module, and the voltage range of the battery module 11 is between the first voltage and the 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 may be 1000V, which is greater than the first voltage of the battery module 11, 600V; or the initial upper limit voltage may be 1500V, which is less than the second voltage of the battery module 11, 1580V.

[0046] It can be understood that in order to make the voltage range of the energy storage converter 12 cover the voltage range of the battery module 11, the voltage range of the energy storage converter 12 is adjusted in this embodiment, and the voltage range of the energy storage converter 12 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 11. Among them, 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. For example, the lower limit voltage of the energy storage inverter 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 600V of the battery module 11; the upper limit voltage of the energy storage inverter 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 1580V of the battery module 11, so that the target voltage range of 600V-1500V can cover the voltage range of 600V-1580V of the battery module 11, so that the voltage range of the battery module 11 matches the target voltage range of the energy storage inverter 12, and the battery module 11 can ensure the normal operation of the battery module 11 and the energy storage inverter 12 when it is fully discharged, thereby improving the energy utilization rate of the energy storage system 10.

[0047] In some embodiments, the voltage range of the sodium ion battery cell during operation can generally be less than the voltage range of 1.5V-3.95V. For example, the voltage range of the sodium ion battery cell can be 1.5V-3.75V. If the battery module 11 is composed of 400 sodium ion battery cells connected in series, the voltage range of the battery module 11 is between 600V-1500V, that is, the first voltage is 600V and the second voltage is 1500V. At this time, since the initial upper limit voltage 1500V of the energy storage converter 12 is equal to the second voltage 1500V, 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 1000V is adjusted to the target lower limit voltage 600V, and the initial upper limit voltage 1500V is equal to the target upper limit voltage 1500V, thereby improving the adjustment efficiency of the energy storage converter 12. Of course, it is also possible to adjust only the initial upper voltage limit without adjusting the initial lower voltage limit. The specific adjustment strategy needs to be set accordingly according to the initial voltage range and the voltage range of the battery module 12, which is not specifically limited here. The voltage range of the battery module 12 is related to the number of sodium ion battery cells according to the voltage range of the sodium ion battery cells therein.

[0048] In some embodiments, the energy storage system 20 may further include a control module, which may be electrically connected to the energy storage inverter 12, or the control module may be disposed inside the energy storage inverter 12. The control module may be used to adjust the voltage range of the energy storage inverter 12 from an initial voltage range to a target voltage range based on a parameter adjustment strategy and / or a mode adjustment strategy.

[0049] Optionally, the parameter adjustment strategy is used for explanation. If the voltage range of the battery module 11 is 600V-1580V, and the initial voltage range of the energy storage inverter 12 is 1000V-1500V, the internal control algorithm of the energy storage inverter 12 is adjusted to change the voltage control strategy of the energy storage inverter 12, so that it can adapt to the input voltage lower than 1000V or higher than 1500V. When the energy storage inverter 12 detects that the input voltage is lower than 1000V or higher than 1500V, it can still work normally and output a stable current. For example, the minimum operating voltage value and the maximum operating voltage value set inside the energy storage inverter 12 are reduced, that is, the voltage range of the energy storage inverter 12 is adjusted to the target voltage range so that it can accept the input voltage of the battery module 11. At the same time, the set values ​​of other relevant parameters of the energy storage inverter 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 inverter 12.

[0050] Optionally, the mode adjustment strategy is used for explanation. If the voltage range of the battery module 11 is 600V-1580V, the initial voltage range of the energy storage inverter 12 is 1000V-1500V. If the input voltage of the battery module 11 is within the initial voltage range, the output power of the energy storage inverter 12 is the rated power, and the working mode of the energy storage inverter 12 is the normal working mode; if the input voltage of the battery module 11 is not within the initial voltage range, the working mode of the energy storage inverter 12 is adjusted to the derated working mode or the increased working mode by reducing or increasing the output power of the energy storage inverter 12. Specifically, the working mode of the energy storage inverter 12 is dynamically adjusted by acquiring the input voltage of the energy storage inverter 12 in real time, so that the target voltage range covers the voltage range of the battery module 11 to ensure the normal operation of the energy storage inverter 12 and the battery module 11, and in the real-time monitoring process of the energy storage inverter 12, it can ensure that the energy storage inverter 12 can detect voltage anomalies, overloads, overheating and other faults in time during the operation of the derating working mode or the increasing working mode, and take corresponding protection measures in time, such as reducing the output power, starting the cooling system, etc., to ensure the safe operation of the energy storage inverter 12.

[0051] As can be seen from the above, the energy storage system 10 provided in this embodiment includes a battery module 11 and an energy storage inverter 12, wherein the voltage range of the battery module 11 is between a first voltage and a second voltage, and the second voltage is greater than the first voltage; the first end of the energy storage inverter 12 is connected to the battery module 11, and the second end of the energy storage inverter 12 is connected to the power grid 20, and the initial voltage range of the energy storage inverter 12 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; the energy storage system 10 is used to adjust the voltage range of the energy storage inverter 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 inverter 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, so that the adjusted target voltage range of the energy storage inverter 12 can cover the voltage range of the battery module 11, without sacrificing the power of the battery module to match the voltage range of the energy storage inverter, thereby improving the energy utilization of the energy storage system.

[0052] It should be noted that the second end of the energy storage inverter 12 of the energy storage system 10, i.e., the DC output end or the AC input end, is a three-phase three-wire system. The three-phase three-wire circuit includes three phase lines and no neutral line. It can only provide line voltage but not phase voltage. It is suitable for three-phase symmetrical loads but not single-phase loads. The application scenarios of energy storage systems such as energy storage outdoor cabinets are mostly industrial and commercial storage, photovoltaic storage and charging, etc. In the application scenarios of industrial and commercial storage, photovoltaic storage and charging, etc., the load types are diverse, including both three-phase symmetrical loads such as large machinery and equipment, air-conditioning systems, etc., and single-phase loads such as lighting, sockets, etc. The three-phase three-wire system cannot provide the phase voltage required by single-phase loads, such as 220V, and cannot meet the power demand of single-phase loads.

[0053] In addition, if the three-phase three-wire system at the second end of the energy storage inverter 12 is directly connected to the power grid, there is an electrical connection between the grounding system of the power grid and the battery module 11. The grounding system of the power grid will interfere with the insulation detection of the battery module 11, resulting in abnormal current in the detection circuit, so that the insulation detection function of the battery module 11 will fail; when the energy storage system is running, the insulation resistance will be very low. If a DC short circuit to the ground occurs, the short-circuit current will flow back to the battery module through the grounding system of the power grid and form a short-circuit circuit, which is very harmful; the harmonics of the power grid or the load will affect the normal operation of the battery module or the energy storage system. When the harmonics are serious, it will affect the sampling of the battery management system of the energy storage system, resulting in deviations, causing the battery management system to be unable to accurately judge the status of the battery module, that is, the three-phase three-wire system at the second end of the energy storage inverter 12 is directly connected to the power grid, which is not suitable for energy storage systems such as outdoor energy storage cabinets.

[0054] In order to solve the above problems caused by the direct connection of the three-phase three-wire energy storage converter to the power grid, this embodiment adds an isolation transformer between the energy storage converter and the power grid, so that the energy storage system is connected to the power grid with a three-phase four-wire system. Figure 2 , Figure 2 1 is a second structural diagram of the energy storage system provided in the embodiment of the present application. The energy storage system 10 may further include an isolation transformer 13, which is disposed between the energy storage converter 12 and the power grid 20. Specifically, a first end of the isolation transformer 13 is connected to a second end of the energy storage converter 12, such as electrically connected, and a second end of the isolation transformer 13 is connected to the power grid 20, such as electrically connected.

[0055] Among them, the second end of the energy storage converter 12 is a three-phase three-wire system, that is, the second end of the energy storage converter 12 includes three phase lines; the second end of the isolation transformer 13 is a three-phase four-wire system, that is, the second end of the isolation transformer 13 includes a neutral line and three phase lines. The isolation transformer 13 is used to convert the three-phase three-wire system of the second end of the energy storage converter 12 into a three-phase four-wire system of the second end of the isolation transformer 13.

[0056] Optionally, the isolation transformer 13 can be a Dyn11 type isolation transformer, wherein Dyn11 represents the connection method and phase relationship of the isolation transformer windings, D represents that the high-voltage winding adopts a triangle connection method, and the triangle-connected winding can provide better lightning impulse resistance and will not generate zero-sequence current when a single-phase grounding fault occurs, which is beneficial to protecting the energy storage system 10; y represents that the low-voltage winding adopts a star connection method, and the star-connected winding can provide a neutral point, which is convenient for leading out the neutral line of the isolation transformer and is suitable for occasions where phase voltage needs to be provided; n represents 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 330° or leads 30° relative to the voltage phasor of the high-voltage winding. This phase relationship helps to reduce the impact of harmonics.

[0057] It should be noted that the three-phase four-wire system can provide line voltage and phase voltage at the same time, can meet the power demand of three-phase loads and single-phase loads, and is suitable for symmetrical and asymmetrical loads. The introduction of the neutral line can effectively reduce voltage fluctuations and power quality problems, improve the stability of the system and the operational reliability of the energy storage system, and the neutral line can provide a current loop to balance the three-phase load, thereby improving the safety and reliability of the energy storage system. Since the application scenarios of the energy storage system 10, such as the energy storage outdoor cabinet, are mostly industrial and commercial storage, photovoltaic storage and charging, etc., the load includes three-phase loads and single-phase loads. Therefore, by setting one side of the energy storage system 10 connected to the power grid 20 to a three-phase four-wire system, that is, converting the three-phase three-wire system at the second end of the energy storage inverter 12 into a three-phase four-wire system at the second end of the isolation transformer 13 through the isolation transformer 13, it can meet the power demand of three-phase loads and single-phase loads in scenarios such as industrial and commercial storage, photovoltaic storage and charging.

[0058] In some embodiments, since the isolation transformer 13 is disposed between the battery module 11 and the power grid 20, if the DC positive / negative poles of the battery module are short-circuited to the ground, the isolation transformer 13 can block the loop so that the short circuit of the energy storage system 10 will not affect the power grid 20. Correspondingly, the short circuit of the power grid 20 will also be blocked by the isolation transformer 13 and will not affect the energy storage system 10. In addition, since the input and output ends of the isolation transformer 13 are completely isolated, the voltage at the input end will not affect the output end, thereby reducing the risk of electric shock, making the energy storage system 10 safer, and the isolation transformer 13 can effectively prevent personal injury caused by accidents such as leakage and electric shock.

[0059] In some embodiments, the isolation transformer 13 can isolate the harmonics generated by the power grid or the load to prevent the energy storage system 10 from being subjected to electromagnetic interference, thereby reducing the impact of electromagnetic compatibility issues on the energy storage system, enabling the battery module or the energy storage system to operate normally, thereby improving the sampling accuracy of the battery management module and improving the accuracy of the battery module status judgment.

[0060] See also Figure 3 , Figure 3 1 is a third structural diagram of the energy storage system provided in the embodiment of the present application. The energy storage system 10 may further include a load 14, which is connected to the second end of the isolation transformer 13, and 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 system at the second end of the isolation transformer 13 includes a neutral line and three phase lines, and the load 14 is connected to the neutral line and one of the phase lines at the second end 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.

[0061] It should be noted that the isolation transformer 13 can not only convert the three-phase three-wire system at the second end of the energy storage inverter 12 into the 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 the three-phase four-wire system at the second end of the isolation transformer 13 is provided with a neutral line, so that the second end of the isolation transformer 13 can also 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 not only receive the electric energy of the power grid 20, but also receive the electric energy of 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 to ensure the normal operation of the load 14, thereby improving the safety and economy of the energy storage system 10.

[0062] In some embodiments, see Figure 4 , Figure 4 This is a fourth structural diagram of the energy storage system provided in the embodiment of the present application. Among them, the load 14 may include an uninterruptible power supply 141 (UPS) and a liquid cooler 142 and other equipment. The UPS is a device that can provide continuous and stable power supply. The UPS can not only stabilize the voltage when the voltage of the energy storage system 10 is unstable, but also provide uninterrupted power guarantee for important loads in the energy storage system 10 such as the battery management system and the fire protection system when the city power is interrupted; the liquid cooler 142 can ensure that the battery cells of the battery module 11 work in a suitable temperature range to improve the service life of the battery module 11 and the working efficiency of the energy storage system 10.

[0063] In addition, the energy storage system 10 may further include a high-voltage box 15, which is disposed between the battery module 11 and the energy storage converter 12. Specifically, a first end of the high-voltage box 15 is connected to a second end of the battery module 11, and a second end of the high-voltage box 15 is connected to a first end of the energy storage converter 12. The high-voltage box 15 can realize functions such as charge and discharge control, protection, and monitoring of the energy storage system 10. The high-voltage box 15 can effectively prevent electrical failures and safety accidents from occurring during the operation of the energy storage system 10 through control and protection functions, thereby ensuring the safety and reliability of the energy storage system 10.

[0064] To further introduce the energy storage system, the present application also provides a control method for the energy storage system, please refer to Figure 5 , Figure 5It is a flow chart of the control method of the energy storage system provided by the embodiment of the present application. Among them, the energy storage system is connected to the power grid, and the energy storage system may include a battery module and an energy storage converter. The voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage. The first end of the energy storage converter is connected to the battery module, and the second end of the energy storage converter is connected to the power grid. The specific process of the control method of the energy storage system can be as follows:

[0065] 101. In response to an adjustment instruction, obtain an initial voltage range of the energy storage converter, 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 a first voltage or the initial upper limit voltage is less than a second voltage.

[0066] The voltage range of the energy storage converter is usually between 600V and 1000V, or between 1000V and 1500V. If the battery module is a sodium-ion battery module, since the voltage range of the sodium-ion battery monomer is between 1.5V and 3.95V, if the battery module includes 400 lithium-ion battery monomers connected in series, the voltage range of the battery module is between 600V and 1580V. At this time, the energy storage converter with a voltage range between 600V and 1000V or between 1000V and 1500V cannot cover the voltage range of the battery module, so that the battery module and the energy storage converter cannot work normally. In order to solve the problem that the voltage range of the battery module and the energy storage inverter is not compatible due to the wide voltage range of the sodium ion battery monomer, this embodiment adjusts the voltage range of the energy storage inverter while ensuring that the sodium ion battery module can be fully charged and discharged, so that the voltage range of the sodium ion battery module and the energy storage inverter are adapted to each other, thereby ensuring that the battery module and the energy storage inverter can work normally, thereby improving the energy utilization rate of the energy storage system.

[0067] The initial voltage range of the energy storage inverter 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 wider, 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 inverter needs to be adjusted. Specifically, in response to the adjustment instruction, the initial voltage range of the energy storage inverter is obtained, and the voltage range of the battery module 11 is between the first voltage and the 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 may be 1000V, which is greater than the first voltage of the battery module 11, 600V; or the initial upper limit voltage may be 1500V, which is less than the second voltage of the battery module 11, 1580V.

[0068] 102. Based on a preset adjustment strategy, the voltage range of the energy storage inverter is adjusted from an 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 limit voltage and a 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.

[0069] It can be understood that in order to make the voltage range of the energy storage converter 12 cover the voltage range of the battery module 11, the voltage range of the energy storage converter 12 is adjusted in this embodiment, and the voltage range of the energy storage converter 12 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 11. Among them, 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. For example, the lower limit voltage of the energy storage inverter 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 600V of the battery module 11; the upper limit voltage of the energy storage inverter 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 1580V of the battery module 11, so that the target voltage range of 600V-1500V can cover the voltage range of 600V-1580V of the battery module 11, so that the voltage range of the battery module 11 matches the target voltage range of the energy storage inverter 12, and the battery module 11 can ensure the normal operation of the battery module 11 and the energy storage inverter 12 when it is fully discharged, thereby improving the energy utilization rate of the energy storage system 10.

[0070] In some embodiments, the voltage range of the sodium ion battery cell during operation can generally be less than the voltage range of 1.5V-3.95V. For example, the voltage range of the sodium ion battery cell can be 1.5V-3.75V. If the battery module 11 is composed of 400 sodium ion battery cells connected in series, the voltage range of the battery module 11 is between 600V-1500V, that is, the first voltage is 600V and the second voltage is 1500V. At this time, since the initial upper limit voltage 1500V of the energy storage converter 12 is equal to the second voltage 1500V, 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 1000V is adjusted to the target lower limit voltage 600V, and the initial upper limit voltage 1500V is equal to the target upper limit voltage 1500V, thereby improving the adjustment efficiency of the energy storage converter 12. Of course, it is also possible to adjust only the initial upper voltage limit without adjusting the initial lower voltage limit. The specific adjustment strategy needs to be set accordingly according to the initial voltage range and the voltage range of the battery module 12, which is not specifically limited here. The voltage range of the battery module 12 is related to the number of sodium ion battery cells according to the voltage range of the sodium ion battery cells therein.

[0071] In some embodiments, the voltage range of the energy storage converter is adjusted from an initial voltage range to a target voltage range based on a parameter adjustment strategy and / or a mode adjustment strategy.

[0072] Optionally, the parameter adjustment strategy is used for explanation. If the voltage range of the battery module 11 is 600V-1580V, and the initial voltage range of the energy storage inverter 12 is 1000V-1500V, the internal control algorithm of the energy storage inverter 12 is adjusted to change the voltage control strategy of the energy storage inverter 12, so that it can adapt to the input voltage lower than 1000V or higher than 1500V. When the energy storage inverter 12 detects that the input voltage is lower than 1000V or higher than 1500V, it can still work normally and output a stable current. For example, the minimum operating voltage value and the maximum operating voltage value set inside the energy storage inverter 12 are reduced, that is, the voltage range of the energy storage inverter 12 is adjusted to the target voltage range so that it can accept the input voltage of the battery module 11. At the same time, the set values ​​of other relevant parameters of the energy storage inverter 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 inverter 12.

[0073] Optionally, the mode adjustment strategy is used for explanation. If the voltage range of the battery module 11 is 600V-1580V, the initial voltage range of the energy storage inverter 12 is 1000V-1500V. If the input voltage of the battery module 11 is within the initial voltage range, the output power of the energy storage inverter 12 is the rated power, and the working mode of the energy storage inverter 12 is the normal working mode; if the input voltage of the battery module 11 is not within the initial voltage range, the working mode of the energy storage inverter 12 is adjusted to the derated working mode or the increased working mode by reducing or increasing the output power of the energy storage inverter 12. Specifically, the working mode of the energy storage inverter 12 is dynamically adjusted by acquiring the input voltage of the energy storage inverter 12 in real time, so that the target voltage range covers the voltage range of the battery module 11 to ensure the normal operation of the energy storage inverter 12 and the battery module 11, and in the real-time monitoring process of the energy storage inverter 12, it can ensure that the energy storage inverter 12 can detect voltage anomalies, overloads, overheating and other faults in time during the operation of the derating working mode or the increasing working mode, and take corresponding protection measures in time, such as reducing the output power, starting the cooling system, etc., to ensure the safe operation of the energy storage inverter 12.

[0074] As can be seen from the above, the embodiment of the present application obtains the initial voltage range of the energy storage inverter by responding to the adjustment instruction, and adjusts the voltage range of the energy storage inverter from the initial voltage range to the target voltage range based on the preset adjustment strategy, so that the target voltage range matches the voltage range of the battery module. This embodiment adjusts the voltage range of the energy storage inverter to the target voltage range, so that the target lower limit voltage of the energy storage inverter is less than or equal to the first voltage of the battery module, and the target upper limit voltage of the energy storage inverter is greater than or equal to the second voltage of the battery module, so that the adjusted target voltage range of the energy storage inverter covers the voltage range of the battery module, thereby improving the energy utilization of the energy storage system.

[0075] A person of ordinary skill in the art will appreciate that all or part of the steps in the various methods of the above embodiments may be completed by instructions, or by controlling related hardware through instructions. The instructions may be stored in a computer-readable storage medium and loaded and executed by a processor.

[0076] To this end, an embodiment of the present application provides a computer-readable storage medium, in which a computer program code is stored. When the computer program code is executed on a computer, the computer executes the above-mentioned related method steps to implement the steps of a control method for an energy storage system provided in the above-mentioned embodiment. For example, the following steps may be specifically performed:

[0077] In response to the adjustment instruction, an initial voltage range of the energy storage converter is acquired, 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;

[0078] Based on a preset adjustment strategy, the voltage range of the energy storage inverter is adjusted from an 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 limit voltage and a 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.

[0079] The specific implementation of the above operations can be found in the previous embodiments, which will not be described in detail here.

[0080] The storage medium may include: a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0081] Since the computer program code stored in the storage medium can execute the steps in any one of the energy storage system control methods provided in the embodiments of the present application, the beneficial effects that can be achieved by any one of the energy storage system control methods provided in the embodiments of the present application can be achieved. For details, please refer to the previous embodiments and will not be repeated here.

[0082] The above is a detailed introduction to an energy storage system, a control method for an energy storage system, and a storage medium provided in an embodiment of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An energy storage system, characterized in that: The energy storage system is connected to the power grid, and the energy storage system includes: A battery module, wherein a voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage; An energy storage converter, wherein a first end of the energy storage converter is connected to the battery module, a second end of the energy storage converter is connected to the power grid, an 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; The energy storage system is used to adjust the voltage range of the energy storage inverter from the initial voltage range to the 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 limit voltage and a 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.

2. The energy storage system according to claim 1, characterized in that: The energy storage system further includes an isolation transformer, which 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 a second end of the isolation transformer is connected to the power grid.

3. The energy storage system according to claim 2, characterized in that: The second end of the energy storage converter is a three-phase three-wire system, and the second end 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, characterized in that: The energy storage system further includes a load, which is connected to the second end of the isolation transformer, and the isolation transformer is used to transmit the output voltage of the battery module to the load.

5. The energy storage system according to claim 4, characterized in that: The three-phase four-wire system at the second end of the isolation transformer includes a 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, characterized in that: The energy storage system further includes a control module, which is used 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, characterized in that: The battery module is a sodium ion battery module, which includes a plurality of sodium ion battery cells, and a voltage range of each of the sodium ion battery cells is between 1.5V and 3.95V.

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

9. A control method for an energy storage system, characterized in that: The energy storage system is connected to a power grid, and includes a battery module and an energy storage converter, wherein a voltage range of the battery module is between a first voltage and a second voltage, and the second voltage is greater than the first voltage; The first end of the energy storage converter is connected to the battery module, and the second end of the energy storage converter is connected to the power grid. The method includes: In response to the adjustment instruction, an initial voltage range of the energy storage converter is acquired, 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 inverter 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, wherein the target voltage range is between a target lower limit voltage and a 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 of the energy storage system according to claim 9, characterized in that: 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 a parameter adjustment strategy and / or a mode adjustment strategy.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program code, and when the computer program is executed on a computer, the steps of the method for controlling the energy storage system according to claim 9 or 10 are implemented.

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