Control method of energy storage system, energy storage system, and control device

Abstract

This application provides a control method, energy storage system, and control device for an energy storage system. The method includes: when the AC bus is disconnected from the power grid, acquiring the power output of the power generation system to the AC bus and the maximum rechargeable power of the energy storage device; determining a target frequency for the AC bus voltage based on the relationship between the power output and the maximum rechargeable power; generating a control signal based on the target frequency; and using the control signal to control the energy storage device to adjust the bus voltage frequency of the AC bus voltage output to the AC bus to the target frequency, so that the power generation system adjusts its power output based on the target frequency to be less than the maximum rechargeable power. The control method for the energy storage system provided in this application can reduce the probability of off-grid failure under off-grid conditions.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method for an energy storage system, an energy storage system, and a control device. Background Technology

[0002] With the development of new energy technologies, more and more families are installing renewable energy power generation systems, such as photovoltaic power generation systems and residential wind power generation systems. Because renewable energy (such as solar and wind power) is intermittent and unstable, many families are also installing energy storage systems to store excess electricity generated by solar or wind power for use when needed, thereby improving energy efficiency.

[0003] However, if the energy storage system and the power generation system are manufactured by different companies, they may be unable to establish communication, thus hindering their ability to coordinate and supply power to the load. In particular, under off-grid conditions, if the power generation capacity of the power generation system, the charging and discharging power of the energy storage system, and the power consumption of the load cannot achieve a dynamic balance, off-grid failure will occur, jeopardizing power safety. Summary of the Invention

[0004] In view of this, this application provides a control method, energy storage system and control equipment for an energy storage system, which can reduce the probability of off-grid failure under off-grid conditions.

[0005] This application provides a control method for an energy storage system, the energy storage system including an AC bus and an energy storage device, the AC bus being used to connect a power generation system, the energy storage device, and a power grid. The method includes: when the AC bus is disconnected from the power grid, acquiring the power generation output from the power generation system to the AC bus and the maximum rechargeable power of the energy storage device; determining a target frequency of the AC bus voltage on the AC bus based on the relationship between the power generation and the maximum rechargeable power; generating a control signal based on the target frequency; the control signal being used to control the energy storage device to adjust the bus voltage frequency of the AC bus voltage output to the AC bus to the target frequency, so that the power generation system adjusts its power generation to be less than the maximum rechargeable power based on the target frequency.

[0006] In one embodiment, determining the target frequency of the AC bus voltage on the AC bus based on the relationship between the generated power and the maximum rechargeable power includes: increasing the target frequency by a first preset step size when the generated power is greater than a first power threshold, and the target frequency being less than or equal to the overfrequency protection threshold of the power generation system; decreasing the target frequency by a second preset step size when the generated power is less than a second power threshold, and the target frequency being greater than or equal to the grid rated frequency; wherein the first power threshold is the product of the maximum rechargeable power and a first coefficient; the second power threshold is the product of the maximum rechargeable power and a second coefficient; the first coefficient is greater than the second coefficient, and both the first coefficient and the second coefficient are less than 1.

[0007] In one embodiment, the energy storage system further includes a switching system; the switching system includes a first switch connected between the power generation system and the AC bus; the method further includes: controlling the first switch to open when the power generation is greater than a third power threshold, wherein the third power threshold is the product of the maximum rechargeable power and a third coefficient; the third coefficient is greater than the first coefficient; the third coefficient is less than or equal to 1.

[0008] In one embodiment, the switching system further includes a second switch connected between the AC bus and the power grid. The method further includes: controlling the first switch to open when a normal power grid condition is detected; generating a pre-synchronization signal; the pre-synchronization signal being used to control the output voltage of the energy storage system to pre-synchronize with the grid voltage; controlling the second switch to close after pre-synchronization is completed; and controlling the first switch to close after the second switch is closed.

[0009] In one embodiment, the method further includes: when the power generation is greater than a third power threshold, using a frequency value greater than or equal to an overfrequency protection threshold as a target frequency, so that the power generation system triggers overfrequency protection based on the target frequency; wherein, the third power threshold is the product of the maximum rechargeable power and a third coefficient; the third coefficient is greater than the first coefficient; and the third coefficient is less than or equal to 1.

[0010] In one embodiment, the method further includes: after the power generation system triggers overfrequency protection, using a preset upper limit value of the grid connection frequency as the target frequency; after a preset duration, using the grid rated frequency as the target frequency, so that the power generation system can restore power output based on the target frequency; the preset duration is positively correlated with the number of times the power generation system is triggered to enter overfrequency protection.

[0011] In one embodiment, the energy storage system further includes a switching system; the switching system includes a second switch connected between the AC bus and the power grid. The method further includes: when a normal power grid condition is detected, determining a frequency value greater than or equal to an overfrequency protection threshold as a target frequency, so that the power generation system triggers overfrequency protection based on the target frequency; generating a pre-synchronization signal; the pre-synchronization signal is used to control the output voltage of the energy storage system to pre-synchronize with the grid voltage; and after pre-synchronization is completed, controlling the second switch to close.

[0012] In one embodiment, increasing the target frequency according to a first preset step size includes: obtaining the bus voltage frequency of the AC bus voltage; when the bus voltage frequency is less than or equal to a preset frequency dead zone threshold, determining the preset frequency dead zone threshold as the target frequency; and when the bus voltage frequency is greater than the preset frequency dead zone threshold, increasing the target frequency according to the first preset step size.

[0013] The second aspect of this application provides an energy storage system, which includes an AC bus, an energy storage device, a memory, and a processor. The AC bus is used to connect a power generation system, the energy storage device, and a power grid. The processor is used to execute a computer program stored in the memory to implement the control method of the energy storage system as described above.

[0014] A third aspect of this application provides a control device, which includes a memory and a processor; the memory stores a computer program so that when the processor executes the computer program, it implements the control method of the energy storage system as described above.

[0015] The control method for the energy storage system provided in this application obtains the power output of the power generation system to the AC bus and the maximum rechargeable power of the energy storage device when the AC bus is disconnected from the grid. Based on the relationship between the power output and the maximum rechargeable power, a target frequency for the AC bus voltage on the AC bus is determined, and a control signal is generated according to the target frequency. This control signal controls the energy storage device to adjust the frequency of the AC bus voltage output to the AC bus to the target frequency. This allows the power generation system to adjust its power output according to the target frequency, ensuring that the power output is less than the maximum rechargeable power. Therefore, it avoids situations where the power output of the power generation system exceeds the maximum rechargeable power of the energy storage device, preventing the energy storage device from absorbing the excess power and ultimately causing grid disconnection failure. In other words, this method reduces the probability of grid disconnection failure of the energy storage system and improves the power safety of the energy storage system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation on the scope of protection of this application. In the various drawings, similar components are numbered similarly.

[0017] Figure 1 This is a schematic diagram of the application environment of an energy storage system provided in an embodiment of this application.

[0018] Figure 2 This is a schematic flowchart of a control method for an energy storage system provided in an embodiment of this application.

[0019] Figure 3 This is a flowchart illustrating the sub-steps of step S202 provided in an embodiment of this application.

[0020] Figure 4 This is a flowchart illustrating the sub-steps of step S301 provided in an embodiment of this application.

[0021] Figure 5 This is a flowchart illustrating a control method for detecting a normal power grid according to an embodiment of this application.

[0022] Figure 6 This is a flowchart illustrating a control method provided in an embodiment of this application after the overfrequency protection of a power generation system is triggered.

[0023] Figure 7 This is a flowchart illustrating a control method for detecting a normal power grid, provided as another embodiment of this application.

[0024] Figure 8 A block diagram of an energy storage system provided in an embodiment of this application.

[0025] Figure 9 This is a block diagram of a control device provided in one embodiment of this application.

[0026] Figure 10 A functional block diagram of a computer-readable storage medium provided in an embodiment of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0028] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have an intervening component. When a component is considered to be "placed" on another component, it can be directly placed on the other component or may also have an intervening component.

[0029] It should also be noted that the methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged, and some steps can also be deleted.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0031] Some embodiments will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] With the development of new energy technologies, more and more families are installing renewable energy power generation systems, such as photovoltaic power generation systems and residential wind power generation systems. Because renewable energy (such as solar and wind power) is intermittent and unstable, many families are also installing energy storage systems to store excess electricity generated by solar or wind power for use when needed, thereby improving energy efficiency.

[0033] For example, please see Figure 1 , Figure 1 This is a schematic diagram of an energy storage system according to an embodiment of this application. The energy storage system 10 includes at least an energy storage device 11 and an AC bus 12. The AC bus 12 is used to connect the power generation system 20, the power grid 30, and the energy storage device 11. The AC bus 12 is also used to connect loads, such as a backup load 40 and a non-backup load 50. Thus, when the power grid 30 malfunctions, on the one hand, at least one of the energy storage system 10 and the power generation system 20 can supply power to the load. On the other hand, the energy storage system 10 can store excess power on the AC bus 12 to supply power to the load when the power grid 30 malfunctions and the power generation system 20 is insufficient to provide the power required by the load.

[0034] In some embodiments, the energy storage device 11 includes at least one battery cell and a power conversion module (not shown). When the energy storage device 11 includes multiple battery cells, the multiple battery cells can be connected in at least one of the following circuit configurations: series and parallel. The power conversion module includes at least an AC / DC circuit. The AC / DC circuit is used to convert the direct current output from the battery cell into alternating current and output it to the AC bus 12, or to draw power from the AC bus 12 and convert it into direct current to charge the battery cell.

[0035] The power generation system 20 can be a renewable energy power generation system, such as a photovoltaic power generation system or a wind power generation system. In one embodiment of this application, when the power generation system 20 is a photovoltaic power generation system, the power generation system 20 includes a photovoltaic module 21 and a photovoltaic inverter 22. The photovoltaic module 21 includes a plurality of photovoltaic panels. The photovoltaic panels convert light energy into electrical energy to output direct current. This application does not limit the connection method of the photovoltaic panels in the photovoltaic module 21. For example, in some embodiments, the photovoltaic panels of the photovoltaic module 21 can be connected in series, in parallel, or in series followed by parallel, etc. The input terminal of the photovoltaic inverter 22 is provided with a maximum power point tracking circuit, and the input terminal of the photovoltaic inverter 22 is also connected to the output terminal of the photovoltaic module 21. The maximum power point tracking circuit is used to perform maximum power point tracking on the photovoltaic power of the photovoltaic module 21 and output DC power. The photovoltaic inverter 22 also includes an inverter circuit, and the input terminal of the inverter circuit is connected to the output terminal of the maximum power point tracking circuit, and the output terminal of the inverter circuit is connected to the output terminal of the photovoltaic inverter 22, so as to convert the DC power output by the maximum power point tracking circuit into AC power and output it to the AC bus 12.

[0036] The power grid 30 may be, for example, a municipal power grid or other power distribution system. This application does not limit the type of AC power in the power grid 30; for example, the power grid 30 may be single-phase AC, split-phase AC, three-phase AC, or other multi-phase AC.

[0037] The backup load 40 can be a load that needs to maintain operation after the power grid 30 is disconnected from the AC bus 12, such as an emergency lighting system, refrigerator, and communication system. The non-backup load 50 can be a load that does not need to maintain operation after the power grid 30 is disconnected from the AC bus 12, such as an air conditioner and a washing machine. Thus, after an anomaly occurs in the power grid 30, at least one of the energy storage system 10 and the power generation system 20 will supply power to the backup load 40. It is understood that the user can classify the loads connected to the AC bus 12 into backup load 40 and non-backup load 50. It is understood that in other embodiments, the load can also be directly connected to the AC bus 12 through the fifth switch 135, and the branch where the non-backup load 50 is located can be omitted. This application does not require that the loads connected to the AC bus 12 must be distinguished.

[0038] In some embodiments, the energy storage system 10 further includes a power generation device 14. The power generation device 14 may be a device that includes both power generation and power supply functions, used to output alternating current to the AC bus 12. That is, the power generation device 14 may include a power generation unit and a power supply unit for realizing energy control. The power generation device 14 may include, but is not limited to, a diesel generator, a gasoline generator, a gas generator, a wind turbine or a hydroelectric generator, a multi-fuel generator, etc., and is not limited thereto.

[0039] In some embodiments, the energy storage system 10 further includes a switching system 13. The switching system 13 may include a first switch 131, a second switch 132, a third switch 133, a fourth switch 134, a fifth switch 135, a sixth switch 136, and a seventh switch 137. The first switch 131 is connected between the power generation system 20 and the AC bus 12. The second switch 132 is connected between the AC bus 12 and the power grid 30. The third switch 133 is connected between the power generation device 14 and the AC bus 12. The fourth switch 134 is connected between the energy storage device 11 and the AC bus 12. The fifth switch 135 is connected between the backup load 40 and the AC bus 12. On the AC bus 12, one end of the fifth switch 135 connected to the AC bus 12 is also connected to the second switch 132 via the sixth switch 136, so that the connection to the power grid 30 is achieved through the sixth switch 136 and the second switch 132. One end of the seventh switch 137 is connected to the non-backup load 50, and the other end of the seventh switch 137 is connected between the sixth switch 136 and the second switch 132.

[0040] In some embodiments, the second switch 132 may include a circuit breaker B2, the third switch 133 may include a circuit breaker B3, the sixth switch 136 may include a relay R6, and the seventh switch 137 may include a circuit breaker B7. The first switch 131, the fourth switch 134, and the fifth switch 135 each include a circuit breaker, a relay, and a current sampling element (not shown) connected in series. For example, the first switch 131 includes a circuit breaker B1 and a relay R1, the fourth switch 134 includes a circuit breaker B4 and a relay R4, and the fifth switch 135 includes a circuit breaker B5 and a relay R5. Thus, the relays can be switched on and off based on the sampled current from the current sampling element, or based on a received control command. The circuit breaker is used to disconnect the power supply branch when an overcurrent occurs, protecting the electronic devices connected to that branch. Therefore, by using relays and circuit breakers to collaboratively control the switching on and off of the power supply branch, the probability of load damage is reduced, and the safety of the energy storage system 10 is improved.

[0041] In some embodiments, the energy storage device 11, the AC bus 12, and the switching system 13 can be integrated into the same electronic device. In other embodiments, the AC bus 12 and the switching system 13 can be used as a single electronic device, such as a power distribution device or distribution cabinet with a manual / automatic transfer switch, to be separately installed from the energy storage device 11. This application does not limit the installation form of the energy storage device 11, the AC bus 12, and the switching system 13 in the energy storage system 10.

[0042] Thus, in the energy storage system 10, the opening and closing of the first switch 131 to the seventh switch 137 can be controlled based on the state of the power grid 30, the power generation capacity of the power generation system 20, the operating state of the power generation equipment 14, and the power demand of the backup load 40 and the non-backup load 50, so as to meet the power demand of the backup load 40 and the non-backup load 50 under different operating conditions. Specifically, in the off-grid operating condition, the first switch 131 and the third switch 133 are not closed simultaneously to prevent the power generation system 20 from flooding the power generation equipment 14, reducing the probability of damage to the power generation equipment 14 and improving the safety of the energy storage system 10.

[0043] Specifically, when the power grid 30 is normal, the second switch 132, the seventh switch 137, the sixth switch 136, and the fifth switch 135 can be closed to put the energy storage system 10 into grid-connected operation, so as to connect to the power grid 30 to supply power to the backup load 40 and the non-backup load 50. When the fourth switch 134 is closed, the energy storage device 11 can be connected to the grid, so that the power grid 30 and the energy storage device 11 jointly supply power to the backup load 40 and the non-backup load 50, or while the power grid 30 supplies power to the backup load 40 and the non-backup load 50, the energy storage device 11 draws power from the AC bus 12 for charging. When the first switch 131 is closed, the energy storage device 11 and the power generation system 20 can be connected to the grid, so that the power grid 30, the energy storage device 11 and the power generation system 20 can jointly supply power to the backup load 40 and the non-backup load 50; or while the power generation system 20 supplies power to the backup load 40 and the non-backup load 50, the energy storage device 11 obtains power from the AC bus 12 for charging, and / or the AC bus 12 feeds power to the power grid 30.

[0044] When the power grid 30 is abnormal, the sixth switch 136 can be controlled to open, so that the energy storage system 10 is in an off-grid condition, thereby enabling the power generation system 20 and the energy storage device 11 to jointly supply power to the backup load 40, or the power generation system 20 supplies power to the backup load 40 while the energy storage device 11 obtains power from the AC bus 12 for charging.

[0045] However, if the energy storage system 10 and the power generation system 20 are manufactured by different manufacturers, they may be unable to establish communication, thus preventing them from coordinating to supply power to the load. In particular, under off-grid conditions, if the power generation of the power generation system 20, the charging and discharging power of the energy storage system 10, and the power consumption of the load, such as the power consumption of the backup load 40, cannot achieve dynamic balance, off-grid failure will occur, which is detrimental to power safety.

[0046] Therefore, this application provides a control method, energy storage system and control equipment for an energy storage system, which can reduce the probability of off-grid failure under off-grid conditions.

[0047] It is worth noting that, Figure 1 Although the energy storage system 10 shown includes an energy storage device 11 and a power generation device 14, and the AC bus 12 is also connected to a power generation system 20, in other embodiments, the energy storage system 10 may be equipped with multiple energy storage devices 11 and multiple power generation devices 14, and the AC bus 12 may also connect to more power generation systems 20. This application does not limit the number of energy storage devices 11 and power generation devices 14 in the energy storage system 10, or the number of power generation systems 20 connected to the AC bus 12.

[0048] It is understood that the control method for the energy storage system provided in this application, in addition to being applied to... Figure 1 The energy storage system 10 shown can also be applied to other application environments that require the simultaneous operation of the energy storage system 10 and the power generation system 20. Figure 1 The schematic diagram of the application environment shown does not limit the control method, energy storage system and control equipment of the energy storage system provided in this application.

[0049] In the following embodiments, in order to simplify the explanation of the working principle and process of the control method of the energy storage system, the control method of the energy storage system is applied to... Figure 1 The energy storage system 10 shown is used as an example.

[0050] Please see Figure 2 , Figure 2 This is a schematic flowchart illustrating a control method for an energy storage system provided in an embodiment of this application. It can be understood that... Figure 2 The control method of the energy storage system shown can be controlled by the processor in the energy storage system 10. Figure 1 The method can be executed by a processor independent of the energy storage system 10 (not shown), or by a processor independent of the energy storage system 10. The method includes the following steps S201-S203.

[0051] Step S201: When the AC bus is disconnected from the grid, obtain the power output of the power generation system to the AC bus and the maximum rechargeable power of the energy storage device.

[0052] In some embodiments, when an anomaly is determined to occur in the power grid 30, the processor can control the sixth switch 136 in the switching system 13 to open, thereby disconnecting the AC bus 12 from the power grid 30 and allowing the energy storage system 10 to enter an off-grid operating condition. This reduces the probability of damage to the electronic devices connected to the AC bus 12 due to the anomaly in the power grid 30. Specifically, at least one of a current sampling circuit, a voltage sampling circuit, and a power sampling circuit can be provided at the end of the second switch 132 connected to the power grid 30. When the processor determines that at least one of the grid current sampled by the current sampling circuit, the grid voltage sampled by the voltage sampling circuit, and the grid power sampled by the power sampling circuit is within an abnormal range, the processor can determine that an anomaly has occurred in the power grid 30 and control the sixth switch 136 to open. In other embodiments, the processor can also receive a control command from a host computer to open the sixth switch 136, thereby allowing the energy storage system 10 to enter an off-grid operating condition. For example, the host computer can be a control device or server that communicates with the energy storage system 10 via wired communication, or a mobile communication device or cloud server that communicates wirelessly with the energy storage system 10. It is understood that after the energy storage system 10 enters the off-grid operating condition, the energy storage device 11 and / or the power generation system 20 can supply power to the backup load 40.

[0053] Understandably, in the energy storage system 10, a power sampling circuit can be set at one end of the first switch 131 connected to the power generation system 20 to obtain the power output of the power generation system 20 to the AC bus 12.

[0054] The maximum rechargeable power of the energy storage device 11 is affected by various factors, such as battery state of charge, temperature, number of charging cycles, and voltage, causing variations in the maximum rechargeable power. In some embodiments, the processor of the energy storage device 11 is further equipped with a Battery Management System (BMS) (not shown) for protecting and managing the energy storage device 11. The BMS can collect at least one of the following battery parameters of the energy storage device 11: battery state of charge (SOC), temperature, charging current, charging voltage, and battery state of health (SOH), and estimate the maximum rechargeable power of the energy storage device 11 in real time based on a preset real-time state of power (SOP) estimation algorithm. This application does not limit the specific steps of the preset real-time SOP estimation algorithm. Understandably, when the processor of the energy storage system 10 and the processor of the energy storage device 11 are not the same processor, the processor of the energy storage system 10 can communicate with the energy storage device 11 to obtain the maximum rechargeable power of the energy storage device 11 in real time.

[0055] Step S202: Determine the target frequency of the AC bus voltage on the AC bus based on the relationship between the power generation and the maximum rechargeable power.

[0056] It is understandable that since the power generation of the power generation system 20, the power demand of the backup load 40, and the maximum rechargeable power of the energy storage device 11 are all variable, when the energy storage system 10 is in off-grid operation, it is easy for the power generation to exceed the sum of the power demand of the backup load 40 and the maximum rechargeable power of the energy storage device 11. For example, if there is a delay or communication failure between the energy storage system 10 and the power generation system 20, preventing the energy storage system 10 from timely notifying the power generation system 20 to limit the power generation, or if the power demand of the backup load 40 suddenly decreases, or if the power generation suddenly increases due to sufficient sunlight, or if the maximum rechargeable power decreases, etc., the power generation may exceed the sum of the power demand and the maximum rechargeable power. When the generated power exceeds the sum of the demand power and the maximum rechargeable power, it indicates that the actual power flowing into the energy storage device 11 from the AC bus 12 may be greater than the maximum rechargeable power of the energy storage device 11. Furthermore, under constant voltage conditions, this may manifest as the current input from the AC bus 12 to the energy storage device 11 exceeding the rated charging current that the energy storage device 11 can withstand. Clearly, excessive charging power and current can damage the energy storage device 11. Moreover, when the charging current reaches a preset current threshold, it may trigger the overcurrent protection of the energy storage device 11, causing charging interruption. Thus, when the generated power exceeds the sum of the demand power and the maximum rechargeable power, making it impossible for the energy storage system 10 to absorb the power difference between the generated power output from the power generation system 20 and the demand power of the backup load 40, it is highly likely that the energy storage system 10 will fail to disconnect from the grid.

[0057] Therefore, in energy storage system 10, when the generated power is greater than or equal to the demand power of the backup load 40, the difference between the generated power and the demand power of the backup load 40 must be greater than the change in the maximum rechargeable power. Considering that the demand power of the backup load 40 may decrease, in the extreme case, when the backup load 40 is disconnected from the AC bus 12, i.e., when the fifth switch 135 is open, the generated power must be less than the maximum rechargeable power of the energy storage device 11 to ensure that the generated power does not exceed the sum of the demand power and the maximum rechargeable power. Therefore, by ensuring that the generated power of the power generation system 20 is less than the maximum rechargeable power of the energy storage device 11, the failure of the energy storage system 10 to disconnect from the grid due to the generated power exceeding the sum of the demand power and the maximum rechargeable power can be avoided.

[0058] Furthermore, since the photovoltaic inverter 22 in the power generation system 20 can be connected to the grid, and grid connection safety regulations require the photovoltaic inverter 22 to have frequency active power regulation function, that is, the photovoltaic inverter 22 can automatically adjust the power generation at its output terminal according to the real-time changes in the grid frequency. In other words, the photovoltaic inverter 22 can adjust the power generation output at its output terminal according to the bus voltage frequency of the AC bus voltage on the AC bus 12 connected to its output terminal. Among them, when the bus voltage frequency on the AC bus 12 is greater than a preset frequency threshold, the power generation output by the photovoltaic inverter 22 is negatively correlated with the bus voltage frequency.

[0059] Thus, in step S202, when the power generation is less than the maximum rechargeable power and the power deviation between the maximum rechargeable power and the power generation is small, the target frequency can be increased. Then, when the frequency of the AC bus 12 is adjusted to the target frequency, the photovoltaic inverter 22 reduces its power generation, ensuring that the power generation is less than the maximum rechargeable power, thereby reducing the probability of the energy storage system 10 failing to disconnect from the grid. When the power generation is less than the maximum rechargeable power and the power deviation between the maximum rechargeable power and the power generation is large, the target frequency can be decreased. Then, when the frequency of the AC bus 12 is adjusted to the target frequency, the photovoltaic inverter 22 appropriately increases its power generation, and the increased power generation is less than the maximum rechargeable power. This reduces the probability of the energy storage system 10 failing to disconnect from the grid while improving the utilization efficiency of the energy from the power generation system 20. When the power generation is greater than the maximum rechargeable power, the processor of the energy storage system 10 promptly disconnects the connection between the energy storage system 10 and the power generation system 20 to improve the safety of the energy storage system 10.

[0060] This application does not impose any restrictions on the algorithm for determining the specific value of the target frequency in step S202.

[0061] Step S203: Generate a control signal based on the target frequency; the control signal is used to control the energy storage device to adjust the frequency of the AC bus voltage output to the AC bus to the target frequency, so that the power generation system adjusts the power generation power to be less than the maximum rechargeable power based on the target frequency.

[0062] The control signal can be a PWM control signal generated by a deviation controller through a deviation adjustment algorithm. For example, based on the deviation adjustment algorithm, deviation adjustment can be performed according to the frequency deviation between the target frequency and the actual frequency of the current AC bus 12 to determine the duty cycle and frequency of the control signal of the switching transistor in the AC / DC circuit of the energy storage device 11. Thus, when the control signal controls the AC / DC circuit in the energy storage device 11 to operate, the frequency of the AC bus voltage output to the AC bus 12 can be adjusted to the target frequency. Furthermore, the photovoltaic inverter 22 can respond to the frequency change on the AC bus 12, automatically adjust the power generation at the output of the photovoltaic inverter 22, and make the power generation less than the maximum rechargeable power, thereby reducing the probability of grid disconnection failure of the energy storage system 10.

[0063] In some embodiments, when the switching system 13 is located within the power distribution equipment, and the power distribution equipment and the energy storage device 11 are separate units, the above method can also be executed by a processor located within the power distribution equipment. Therefore, the power distribution equipment can also generate a frequency synchronization signal based on the target frequency and output it to the energy storage device 11 via a communication line. The frequency of the frequency synchronization signal is the same as the target frequency. Thus, after receiving the frequency synchronization signal, the energy storage device 11 can determine the target frequency based on the frequency synchronization signal, thereby generating a control signal based on the target frequency. When the control signal controls the AC / DC circuit in the energy storage device 11 to operate, the bus voltage frequency of the AC bus voltage output by the AC / DC circuit to the AC bus 12 can be adjusted to the target frequency.

[0064] In summary, the control method for the energy storage system provided in this application obtains the power output of the power generation system 20 to the AC bus 12 and the maximum rechargeable power of the energy storage device 11 when the AC bus 12 is disconnected from the power grid 30. Based on the relationship between the power generation and the maximum rechargeable power, a target frequency of the AC bus voltage on the AC bus 12 is determined, and a control signal is generated according to the target frequency. This control signal controls the energy storage device 11 to adjust the bus voltage frequency of the AC bus voltage output to the AC bus 12 to the target frequency, and the power generation system 20 can adjust its power generation according to the bus voltage frequency. Thus, when the power generation is less than the maximum rechargeable power and the power deviation between the maximum rechargeable power and the power generation is small, the processor adjusts the bus voltage frequency on the AC bus, causing the power generation system 20 to reduce its power generation, thereby ensuring that the power generation is less than the maximum rechargeable power and reducing the probability of the energy storage system 10 failing to disconnect from the grid. Furthermore, when the power generation is less than the maximum rechargeable power and the power deviation between the maximum rechargeable power and the power generation is large, the processor adjusts the bus voltage frequency on the AC bus so that the power generation system 20 can appropriately increase the power generation, and the increased power generation is less than the maximum rechargeable power. This reduces the probability of the energy storage system 10 failing to go off-grid while improving the utilization efficiency of the energy storage system 10 for the energy output of the power generation system 20.

[0065] Please see Figure 3 In some embodiments, step S202 includes the following steps S301-S302.

[0066] Step S301: When the power generation is greater than the first power threshold, the target frequency is increased according to the first preset step size, and the target frequency is less than or equal to the overfrequency protection threshold of the power generation system.

[0067] The first power threshold is the product of the maximum rechargeable power and a first coefficient, where the first coefficient is less than 1. This ensures that the first power threshold is less than the maximum rechargeable power. In some embodiments, the first coefficient may be greater than 0.5, for example, it may be 0.8 or 0.9. This application does not limit the specific value of the first coefficient.

[0068] It is understandable that when the power generation exceeds the first power threshold, it indicates that the power generation exceeds the maximum rechargeable power, which may lead to the failure of the energy storage system 10 to disconnect from the grid. At this time, the target frequency is increased according to the first preset step size, so that a control signal is subsequently generated according to the target frequency to adjust the bus voltage frequency on the AC bus 12 to the target frequency. This causes the power generation system 20 to reduce the power generation according to the bus voltage frequency, thereby reducing the probability of the energy storage system 10 failing to disconnect from the grid.

[0069] In step S301, the overfrequency protection threshold represents the critical frequency value that triggers the overfrequency protection of the power generation system 20. It can be understood that when the power generation system 20 confirms that the bus voltage frequency is greater than the overfrequency protection threshold, it will trigger the overfrequency protection and thus stop outputting power. Therefore, in step S301, by increasing the target frequency while controlling it to be less than or equal to the overfrequency protection threshold, the number of shutdowns of the power generation system 20 can be reduced, further improving the energy utilization rate of the power generation system 20.

[0070] Step S302: When the power generation is less than the second power threshold, the target frequency is reduced according to the second preset step size, and the target frequency is greater than or equal to the grid rated frequency.

[0071] The second power threshold is the product of the maximum rechargeable power and a second coefficient; the first coefficient is greater than the second coefficient, and the second coefficient is less than 1. That is, the first power threshold is greater than the second power threshold. In some embodiments, the second coefficient is greater than 0 and less than 0.5. This application does not limit the specific value of the second coefficient, as long as the second coefficient is less than the first coefficient.

[0072] It is understandable that when the power generation is less than the second power threshold, it indicates a large power difference between the power generation and the maximum rechargeable power, suggesting that the power generation of the power generation system 20 may be reduced due to factors such as decreased light intensity. In this case, the target frequency is reduced according to the second preset step size. Subsequently, a control signal is generated based on the target frequency to adjust the bus voltage frequency on the AC bus 12 to the target frequency. This allows the power generation system 20 to increase its power generation according to the bus voltage frequency, thereby improving the utilization rate of the energy output by the energy storage system 10.

[0073] In some embodiments, the grid rated frequency may be, for example, 50Hz. Understandably, the grid rated frequency may vary in different regions, and this application does not limit the specific value of the grid rated frequency. In step S302, while reducing the target frequency, it is ensured that the target frequency is greater than or equal to the grid rated frequency to prevent the photovoltaic inverter 22 in the power generation system 20 from triggering underfrequency protection and shutting down, and to prepare for the subsequent off-grid to grid connection of the power generation system 20.

[0074] In summary, by executing steps S301 and S302, the target frequency of the AC bus voltage can be determined according to the magnitude of the power generation, thereby effectively adjusting the power generation to maximize the utilization rate of the energy storage system 10 on the energy output of the power generation system 20 while ensuring that the power generation is less than the maximum rechargeable power of the energy storage device 11.

[0075] In some embodiments, the first preset step size and the second preset step size can be fixed preset values. In other embodiments, the first preset step size and the second preset step size can also be dynamically changing values. This application does not limit the specific values ​​of the first preset step size and the second preset step size in steps S301-S302; the first preset step size and the second preset step size can be equal or unequal.

[0076] Please see Figure 4 In some embodiments, step S301 includes the following steps S401-S403.

[0077] Step S401: Obtain the bus voltage frequency of the AC bus voltage.

[0078] In some embodiments, the AC bus voltage on AC bus 12 can be sampled, and phase-locked to determine the bus voltage frequency. This application does not limit the specific algorithm for obtaining the bus voltage frequency in step S401.

[0079] Step S402: When the bus voltage frequency is less than or equal to the preset frequency dead zone threshold, determine the preset frequency dead zone threshold as the target frequency.

[0080] The preset frequency dead zone threshold represents the critical frequency value at which the power generation system 20 reduces its power generation as the bus voltage frequency increases, and this preset frequency dead zone threshold is greater than the grid's rated frequency. In other words, when the bus voltage frequency is greater than or equal to the preset frequency dead zone threshold, the power generation is negatively correlated with the bus voltage frequency. Thus, by executing step S402, the target frequency can be quickly adjusted to the preset frequency dead zone threshold, causing a rapid decrease in power generation and thereby quickly reducing the risk of the energy storage system 10 failing to disconnect from the grid.

[0081] It is understood that the preset frequency dead zone threshold can be determined based on the grid rated frequency and the frequency error threshold. The frequency error threshold can be determined based on the frequency accuracy error of the energy storage system 10 and the frequency accuracy error of the photovoltaic inverter 22. This application does not limit the size of the preset frequency dead zone threshold.

[0082] Step S403: When the bus voltage frequency is greater than the preset frequency dead zone threshold, increase the target frequency according to the first preset step size.

[0083] In some embodiments, a first preset step size can be used as the increment of the target frequency for each step, thereby gradually increasing the target frequency. In other embodiments, the increment of the target frequency for each step can also be determined based on the product of the first preset step size and an adjustment coefficient. The adjustment coefficient can be a preset coefficient or a variable coefficient, thus allowing for more flexible and rapid determination of the target frequency to achieve rapid adjustment of power generation. Understandably, this application does not limit the specific algorithm for increasing the target frequency based on the first preset step size. In other embodiments, other algorithms can also be used to increase the target frequency based on the first preset step size.

[0084] In summary, by executing steps S401-S403, the target frequency can be quickly and flexibly determined when the power generation exceeds the first power threshold, so as to adjust the power generation according to the target frequency, thereby reducing the risk of the energy storage system 10 failing to go off-grid.

[0085] Accordingly, in step S302, when the power generation is less than the second power threshold and the bus voltage frequency is less than the grid rated frequency, the grid rated frequency is determined as the target frequency; when the power generation is less than the second power threshold and the bus voltage frequency is greater than the grid rated frequency, the target frequency is reduced according to the second preset step size.

[0086] In some embodiments, the second preset step size can be used as the reduction amount of the target frequency each time to gradually reduce the target frequency. In other embodiments, the reduction amount of the target frequency each time can also be determined based on the product of the second preset step size and an adjustment coefficient, and the adjustment coefficient can be a preset coefficient or a variable coefficient. This application does not limit the specific algorithm for reducing the target frequency based on the second preset step size.

[0087] In some embodiments, the photovoltaic inverter 22 in the power generation system 20 can adjust the power generation power according to the bus voltage frequency based on the following formula.

[0088]

[0089] Where p represents the power generation capacity; p pre p represents the power generation sampled at the previous moment; rate Indicates rated generating power; f represents the current bus voltage frequency; f of Indicates the preset frequency dead zone threshold; f n Indicates the rated frequency of the power grid; k of p represents the over-frequency droop coefficient. min This represents the minimum generating capacity. Where f... of =f n +db of db of This is a dead zone due to low frequency.

[0090] Thus, based on the above formula, when the bus voltage frequency is greater than the preset frequency dead zone threshold, the power generation is negatively correlated with the bus voltage frequency. This causes the power generation to decrease as the bus voltage frequency increases until it reaches its minimum value, and the power generation to increase as the bus voltage frequency decreases until it reaches its maximum value.

[0091] In some embodiments, the control method for the energy storage system further includes:

[0092] When the power generation is greater than the third power threshold, the first switch is opened. The third power threshold is the product of the maximum rechargeable power and the third coefficient. The third coefficient is greater than the first coefficient. The third coefficient is less than or equal to 1.

[0093] In other words, the maximum rechargeable power is greater than or equal to the third power threshold, and the third power threshold is greater than the first power threshold.

[0094] In some embodiments, the third coefficient may also be greater than 0.5. This application does not limit the specific value of the first coefficient, as long as the third coefficient is greater than the first coefficient.

[0095] It is understandable that when the power generation is greater than the third power threshold, it means that the power generation is very close to the maximum rechargeable power. At this time, in order to avoid the failure of the energy storage system 10 to go off the grid, the processor of the energy storage system 10 actively controls the first switch 131 to disconnect the connection between the energy storage system 10 and the power generation system 20, thereby avoiding the failure of the energy storage system 10 to go off the grid.

[0096] In some embodiments, when the power generation exceeds a third power threshold, the relay R1 in the first switch 131 can be opened, thereby disconnecting the energy storage system 10 from the power generation system 20. In other embodiments, the circuit breaker B1 in the first switch 131 can be opened, or both the circuit breaker B1 and the relay R1 in the first switch 131 can be opened, thereby disconnecting the energy storage system 10 from the power generation system 20.

[0097] Thus, by implementing this embodiment, the energy storage system 10 can be disconnected from the power generation system 20 in a timely manner according to the power generation capacity, thereby reducing the probability of the energy storage system 10 failing to go off-grid.

[0098] Please see Figure 5 In some embodiments, the method for the energy storage system further includes the following steps S501-S504 to realize the off-grid to grid connection of the energy storage system 10.

[0099] Step S501: When the power grid is detected to be normal, the first switch is opened.

[0100] In some embodiments, when the processor determines that the grid current sampled by the current sampling circuit and the grid voltage sampled by the voltage sampling circuit are both within a preset range, the processor can determine that the grid 30 is normal.

[0101] Understandably, the first switch 131 can be disconnected by controlling the relay R1 and / or circuit breaker B1 in the first switch 131 to disconnect.

[0102] Thus, by executing step S501, the connection between the power generation system 20 and the energy storage system 10 is disconnected to prevent the power generation system 20 from affecting the pre-synchronization of the energy storage system 10.

[0103] Step S502: Generate a pre-synchronization signal; the pre-synchronization signal is used to control the output voltage of the energy storage system to be pre-synchronized with the grid voltage.

[0104] In step S502, the grid voltage can be sampled and phase-locked to obtain the output phase angle and amplitude of the grid voltage. A pre-synchronization signal is then generated based on the output phase angle, and the effective edge of the pre-synchronization signal corresponds to a preset phase of the output phase angle. Thus, when the energy storage device 11 in the energy storage system 10 receives the pre-synchronization signal, it can determine the pre-synchronization angular frequency, i.e., the real-time angular frequency of the grid voltage, based on the pre-synchronization angular frequency. Phase tracking is then performed based on the deviation between the pre-synchronization angular frequency and the output angular frequency of the output voltage from the energy storage device 11 to the AC bus 12, thereby achieving phase synchronization between the output voltage of the energy storage system 10 and the grid voltage.

[0105] In some embodiments, the energy storage device 11 also adjusts the amplitude of the output voltage according to the amplitude deviation between the grid voltage amplitude and the output voltage amplitude, so as to achieve synchronization between the output voltage of the energy storage system 10 and the grid voltage amplitude.

[0106] Thus, when the energy storage device 11 achieves phase synchronization and amplitude synchronization, it can be confirmed that the output voltage of the energy storage system 10 is pre-synchronized with the grid voltage.

[0107] Step S503: After completing the pre-synchronization, control the second switch to close.

[0108] Understandably, after pre-synchronization is completed, the amplitude of the output voltage of the energy storage system 10 is close to or even equal to the amplitude of the grid voltage, and the phase of the output voltage of the energy storage system 10 is close to or even equal to the phase of the grid voltage. At this time, controlling the second switch 132 to close can realize the safe grid connection of the energy storage system 10.

[0109] Step S504: After the second switch is closed, control the first switch to close.

[0110] Understandably, closing the first switch 131 means closing both the circuit breaker B1 and the relay R1 in the first switch 131, so that the energy storage system 10 is connected to the power generation system 20.

[0111] After the first control switch 131 is closed, the photovoltaic inverter 22 in the power generation system 20 can adjust its output power generation voltage according to the AC bus voltage on the AC bus 12, so as to realize the synchronization of the power generation voltage with the AC bus voltage, thereby realizing the grid connection of the power generation system 20.

[0112] In summary, by executing steps S501-S504, when the grid 30 is detected to be normal, the energy storage system 10 and the power generation system 20 can be safely connected to the grid, thereby maximizing the utilization of the power generation capacity of the power generation system 20. During the switch from off-grid to on-grid, by first disconnecting the output of the power generation device 14, and then controlling the power generation device 14 to output again after the energy storage device 11 has completed its connection with the grid 30, the problem of grid connection failure due to asynchronous output of the power generation device 14 can be avoided.

[0113] In some embodiments, the control method for the energy storage system further includes:

[0114] When the power generation is greater than the third power threshold, the frequency value that is greater than or equal to the overfrequency protection threshold is used as the target frequency so that the power generation system can trigger overfrequency protection based on the target frequency.

[0115] It is understandable that using a frequency value greater than or equal to the over-frequency protection threshold as the target frequency can make the bus voltage frequency on AC bus 12 greater than or equal to the over-frequency protection threshold. This will cause the power generation system 20 to actively stop outputting power to AC bus 12 after triggering over-frequency protection, thereby reducing the probability of the energy storage system 10 failing to go off-grid due to the power generation exceeding the maximum rechargeable power.

[0116] Thus, by implementing this embodiment, even if the energy storage system 10 is not equipped with a switching circuit connected to the power generation system 20, the power generation system 20 can actively disconnect from the energy storage system 10, thereby reducing the probability of the energy storage system 10 failing to go off-grid.

[0117] Please see Figure 6 In some embodiments, the control method for the energy storage system further includes the following steps S601-S602.

[0118] Step S601: After the power generation system triggers overfrequency protection, the preset grid connection frequency upper limit value is used as the target frequency.

[0119] Specifically, the preset upper limit of the grid connection frequency is lower than the over-frequency protection threshold and higher than the grid's rated frequency. Therefore, using the preset upper limit of the grid connection frequency as the target frequency will not trigger the over-frequency protection of the power generation system 20. Furthermore, because the preset upper limit of the grid connection frequency is used as the target frequency, the bus voltage frequency is maintained at a relatively high value, thereby limiting the output power of the power generation system 20. This effectively suppresses the power generation of the power generation system 20 and reduces the risk of the energy storage system 10 failing to disconnect from the grid.

[0120] Step S602: After a preset duration, the grid rated frequency is used as the target frequency so that the power generation system can restore power output based on the target frequency; the preset duration is positively correlated with the number of times the power generation system is triggered to enter overfrequency protection.

[0121] In step S602, when the grid rated frequency is used as the target frequency, the photovoltaic inverter 22 in the power generation system 20 can be used to regulate the frequency of power generation, enabling the power generation system 20 to output full power. This allows the power generation system 20 to resume power output to the energy storage system 10 after triggering overfrequency protection, thereby improving the energy utilization rate of the power generation system 20 and maximizing user benefits. Understandably, after setting the grid rated frequency as the target frequency, if changes in sunlight intensity cause changes in power generation, the target frequency can be determined based on step S202 to allow the power generation system 20 to adjust its own power output.

[0122] In some embodiments, after each time a frequency value greater than or equal to the overfrequency protection threshold is used as the target frequency, when the power generation is detected to be 0 or less than a preset power threshold, a counter is incremented by 1, and the counter value is used as the number of times the power generation system 20 enters overfrequency protection. The preset duration is determined based on a reference duration and the number of overfrequency protection cycles. For example, the product of the reference duration and the number of overfrequency protection cycles can be used as the preset duration. The reference duration can be, for example, 1 minute. It is understood that in other embodiments, the preset duration can also be determined based on other algorithms, using the reference duration and the number of overfrequency protection cycles.

[0123] In summary, by executing steps S601-S602, after using a frequency value greater than or equal to the overfrequency protection threshold as the target frequency to trigger the overfrequency protection of the power generation system 20, the energy storage system 10 can be reconnected to the power generation system 20 to improve the energy utilization rate of the power generation system 20 and maximize user benefits.

[0124] Please see Figure 7 In some embodiments, when the switching system 13 further includes a second switch 132 connected between the AC bus 12 and the power grid 30, the method of the energy storage system further includes the following steps S701-S703.

[0125] Step S701: When the power grid is detected to be normal, the frequency value that is greater than or equal to the overfrequency protection threshold is determined as the target frequency so that the power generation system triggers overfrequency protection based on the target frequency.

[0126] Thus, in step S701, when the power grid is detected to be normal, by determining the frequency value that is greater than or equal to the overfrequency protection threshold as the target frequency, the bus voltage frequency can be greater than or equal to the overfrequency protection threshold, thereby causing the power generation system 20 to trigger overfrequency protection and actively stop outputting power generation to the AC bus 12, thereby avoiding the power generation system 20 from affecting the pre-synchronization of the energy storage system 10.

[0127] Step S702: Generate a pre-synchronization signal; the pre-synchronization signal is used to control the output voltage of the energy storage system to be pre-synchronized with the grid voltage.

[0128] The specific process of generating the pre-synchronization signal in step S702 is roughly the same as that in step S502. Please refer to the relevant content in step S502 for details, which will not be repeated here.

[0129] Step S703: After completing the pre-synchronization, control the second switch to close.

[0130] Understandably, after pre-synchronization is completed, closing the second switch 132 allows the energy storage system 10 to be connected to the grid.

[0131] In summary, by executing steps S701-S703, even if the energy storage system 10 is not equipped with a switching circuit connected to the power generation system 20, the power generation system 20 can actively disconnect from the energy storage system 10 when the grid 30 is detected to be normal, thereby reducing the interference of the power generation system 20 on the grid connection of the energy storage system 10.

[0132] In some embodiments, after the second switch is closed, the grid rated frequency is also used as the target frequency so that the power generation system 20 can restore power output based on the target frequency, thereby achieving safe grid connection of the power generation system 20.

[0133] Please see Figure 8 One embodiment of this application also provides an energy storage system 10, including an AC bus 12, an energy storage device 11, a memory 15, and a processor 16. The AC bus 12 is used to connect a power generation system 20, an energy storage device 11, and a power grid 30. The processor 16 is used to execute a computer program stored in the memory 15 to implement the control method of the energy storage system as described in any of the above embodiments.

[0134] Please refer to it again. Figure 1 In some embodiments, the energy storage system 10 further includes a switching system 13 and / or a power generation device 14. The switching system 13 may be a separate power distribution device, or it may be integrated into the energy storage device 11.

[0135] Please see Figure 9 An embodiment of this application also provides a control device 100, including a memory 15 and a processor 16. The memory 15 stores a computer program so that when the processor 16 executes the computer program, it implements the control method of the energy storage system as described in any of the above embodiments.

[0136] It is understood that the control device 100 can be a standalone electronic device or integrated into the energy storage device 11. The control device 100 can also be integrated with the switching system 13 on the power distribution equipment. This application does not limit the specific form of the control device 100.

[0137] Please see Figure 10 This application also provides a computer-readable storage medium 200 storing a computer program 201 thereon. When executed by a processor, the computer program 201 implements the control method of the energy storage system as described in the above technical solutions. The computer-readable storage medium may be a portable compact disc read-only memory (CD-ROM) and include program code, and may run on a terminal device, such as a personal computer. However, the program product of this invention is not limited thereto. In this document, the readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0138] It is understood that the processor 16 mentioned in this application may include a central processing unit (CPU), other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, etc.

[0139] The above-described program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0140] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0141] The program code contained on the readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0142] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0143] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0144] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method of an energy storage system including an AC bus for connecting a power generation system, an energy storage device, and a power grid, and the energy storage device, characterized by, The method includes: When the AC bus is disconnected from the power grid, the power output of the power generation system to the AC bus and the maximum rechargeable power of the energy storage device are obtained. The target frequency of the AC bus voltage on the AC bus is determined based on the relationship between the power generation capacity and the maximum rechargeable power. A control signal is generated based on the target frequency; the control signal is used to control the energy storage device to adjust the bus voltage frequency of the AC bus voltage output to the AC bus to the target frequency, so that the power generation system adjusts the power generation power to be less than the maximum rechargeable power based on the target frequency.

2. The method of claim 1, wherein, Determining the target frequency of the AC bus voltage on the AC bus based on the relationship between the generated power and the maximum rechargeable power includes: When the power generation is greater than the first power threshold, the target frequency is increased according to the first preset step size, and the target frequency is less than or equal to the overfrequency protection threshold of the power generation system. When the power generation is less than the second power threshold, the target frequency is reduced according to the second preset step size, and the target frequency is greater than or equal to the grid rated frequency; wherein, the first power threshold is the product of the maximum rechargeable power and the first coefficient; the second power threshold is the product of the maximum rechargeable power and the second coefficient; the first coefficient is greater than the second coefficient, and both the first coefficient and the second coefficient are less than 1.

3. The method of claim 2, wherein, The energy storage system further includes a switching system; the switching system includes a first switch connected between the power generation system and the AC bus; the method further includes: When the power generation is greater than the third power threshold, the first switch is controlled to open, wherein the third power threshold is the product of the maximum rechargeable power and the third coefficient; the third coefficient is greater than the first coefficient; and the third coefficient is less than or equal to 1.

4. The method of claim 3, wherein, The switching system further includes a second switch connected between the AC bus and the power grid; the method further includes: When the power grid is detected to be normal, the first switch is controlled to open; A pre-synchronization signal is generated; the pre-synchronization signal is used to control the output voltage of the energy storage system to be pre-synchronized with the grid voltage. After pre-synchronization is completed, control the second switch to close; After the second switch is closed, the first switch is controlled to close.

5. The method of claim 2, wherein, The method further includes: When the power generation is greater than the third power threshold, a frequency value greater than or equal to the overfrequency protection threshold is used as the target frequency, so that the power generation system triggers overfrequency protection based on the target frequency; wherein, the third power threshold is the product of the maximum rechargeable power and the third coefficient; the third coefficient is greater than the first coefficient; the third coefficient is less than or equal to 1.

6. The control method according to claim 5, characterized in that, The method further includes: After the power generation system triggers overfrequency protection, the preset upper limit of the grid connection frequency is used as the target frequency; After a preset duration, the grid rated frequency is used as the target frequency so that the power generation system can restore power output based on the target frequency; the preset duration is positively correlated with the number of times the power generation system is triggered to enter overfrequency protection.

7. The method according to claim 5, characterized in that, The energy storage system further includes a switching system; the switching system includes a second switch connected between the AC bus and the power grid; the method further includes: When the power grid is detected to be normal, a frequency value greater than or equal to the overfrequency protection threshold is determined as the target frequency, so that the power generation system triggers overfrequency protection based on the target frequency; A pre-synchronization signal is generated; the pre-synchronization signal is used to control the output voltage of the energy storage system to be pre-synchronized with the grid voltage. After pre-synchronization is completed, the second switch is closed.

8. The method according to claim 2, characterized in that, Increasing the target frequency according to a first preset step size includes: Obtain the bus voltage frequency of the AC bus voltage; When the bus voltage frequency is less than or equal to a preset frequency dead zone threshold, the preset frequency dead zone threshold is determined as the target frequency; When the bus voltage frequency is greater than the preset frequency dead zone threshold, the target frequency is increased according to the first preset step size.

9. An energy storage system, characterized in that, The energy storage system includes an AC bus, an energy storage device, a memory, and a processor. The AC bus is used to connect the power generation system, the energy storage device, and the power grid. The processor is used to execute a computer program stored in the memory to implement the control method of the energy storage system as described in any one of claims 1 to 8.

10. A control device, characterized in that, The control device includes a memory and a processor; the memory stores a computer program such that when the processor executes the computer program, it implements the control method of the energy storage system as described in any one of claims 1 to 8.

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