Energy storage system and operating method thereof

Abstract

This application provides an energy storage system and its operation method. The energy storage system provides power regulation to the power grid with a maximum value equal to a predetermined capacity. The energy storage system includes an energy storage unit, a measurement unit, and a control unit. The measurement unit measures the operating frequency of the power grid. The control unit receives the operating frequency of the power grid measured by the measurement unit. When the operating frequency of the power grid is greater than or equal to a third frequency boundary value and less than or equal to a fourth frequency, the control unit sets a regulation ratio less than or equal to a second operating ratio and greater than or equal to a second input boundary value. The third frequency boundary value is greater than the second frequency boundary value, the second operating ratio is less than the first operating ratio, and the second efficiency value of charging the energy storage unit from the power grid at the second operating ratio is greater than the first efficiency value of charging the energy storage unit from the power grid at the first operating ratio, which is greater than a first efficiency threshold.

Description

Technical Field

[0001] This case relates to an energy storage system and its operating method, particularly an energy storage system and its operating method that can improve efficiency. Prior Art

[0002] In response to increasing energy and environmental demands, renewable energy sources such as wind and solar power are playing an increasingly important role in power systems and are steadily increasing their share of electricity supply. However, the volatile nature of renewable energy also poses numerous management challenges for traditional power grids. Energy storage systems, which enhance reliability, resilience, and flexibility, are increasingly being used in power grids. Energy storage systems can include battery systems (e.g., fuel cells and lithium-ion batteries, which are energy conversion devices) and energy management systems, providing functions such as voltage and frequency regulation.

[0003] To address the volatility of renewable energy and the variability of power generation mix and demand, power companies have developed a range of ancillary services and established corresponding electricity market rules to enhance grid stability and resilience. These services include frequency regulation, voltage regulation, demand response, and black starts. Each of these services has specific rules governing energy storage responses. However, directly regulating energy storage according to these rules can lead to poor system performance. Furthermore, factors such as energy storage system configuration, power topology, the surrounding environment (such as temperature and humidity), and grid conditions can cause the energy storage system to operate at an inefficient state or excessively wear out the system, shortening its service life. Therefore, the comprehensive integration of energy storage systems to achieve optimal operation, effectively utilizing site configurations, improving or regulating the energy storage efficiency curve, and extending battery life, is a pressing need. Summary of the Invention

[0004] The purpose of this case is to provide an energy storage system and its operation method to solve the aforementioned technical problems.

[0005] To achieve the above objectives, this invention provides an energy storage system for coupling to a power grid to provide power regulation to the grid with a maximum agreed capacity. When the operating frequency of the power grid is greater than or equal to a first frequency and less than or equal to a second frequency, the power regulation ratio of the energy storage system is greater than or equal to a first input boundary value and less than or equal to a first output boundary value. When the operating frequency of the power grid is greater than or equal to a third frequency and less than or equal to the first frequency, the power regulation ratio of the energy storage system is greater than or equal to the first input boundary value and less than or equal to a second output boundary value. When the operating frequency decreases from the first frequency to the third frequency, the plurality of first upper limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first output boundary value to the second output boundary value, and the plurality of first lower limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first input boundary value to the second output boundary value. When the operating frequency of the power grid is greater than or equal to the second frequency and less than or equal to a fourth frequency, the power regulation ratio of the energy storage system is greater than or equal to the second input boundary value and less than or equal to the first output boundary value. When the operating frequency increases from the second frequency to the fourth frequency, the plurality of second upper limits of the adjustment ratio corresponding to the change in operating frequency correspondingly decrease from the first output boundary value to the second input boundary value, and the plurality of second lower limits of the adjustment ratio corresponding to the change in operating frequency correspondingly decrease from the first input boundary value to the second input boundary value. The energy storage system includes an energy storage unit, a measuring unit, and a control unit. The energy storage unit is used to store and provide electrical energy. The measuring unit is used to measure the operating frequency of the power grid. The control unit is coupled to the measuring unit and the energy storage unit and is used to receive the operating frequency of the power grid measured by the measuring unit. When the state of charge of the energy storage unit is greater than a first charge, the energy storage unit is in a normal charge state; when the state of charge of the energy storage unit is less than the first charge, the energy storage unit is in a low charge state. When the control unit sets the adjustment ratio of the energy storage system's power regulation to be greater than 0, the control unit sets the energy storage unit to supply power to the power grid at the adjustment ratio of the agreed capacity. When the control unit sets the adjustment ratio of the energy storage system's power regulation to be less than 0, the control unit sets the energy storage unit to charge from the power grid at the adjustment ratio of the agreed capacity. When the operating frequency of the power grid measured by the measurement unit is greater than or equal to a first frequency boundary value and less than or equal to a second frequency boundary value, the control unit sets the power regulation adjustment ratio to a first operating ratio, where the first operating ratio is less than or equal to 0 and greater than or equal to a first input boundary value. The first frequency boundary value is less than the first frequency and / or the second frequency boundary value is greater than the second frequency. When the operating frequency of the power grid measured by the measurement unit is greater than or equal to a third frequency boundary value and less than or equal to a fourth frequency, the control unit sets the power regulation adjustment ratio to be less than or equal to the second operating ratio and greater than or equal to the second input boundary value. The third frequency boundary value is greater than the second frequency boundary value, the second operating ratio is less than the first operating ratio, and a second efficiency value of charging the energy storage unit from the power grid at the second operating ratio is greater than a first efficiency threshold value compared to a first efficiency value of charging the energy storage unit from the power grid at the first operating ratio.

[0006] To achieve the above objectives, the present invention further provides an operating method for an energy storage system, wherein the energy storage system is coupled to a power grid to provide power regulation to the power grid with a maximum agreed capacity. When the operating frequency of the power grid is greater than or equal to a first frequency and less than or equal to a second frequency, the power regulation ratio of the energy storage system is greater than or equal to a first input boundary value and less than or equal to a first output boundary value. When the operating frequency of the power grid is greater than or equal to a third frequency and less than or equal to the first frequency, the power regulation ratio of the energy storage system is greater than or equal to the first input boundary value and less than or equal to a second output boundary value. When the operating frequency decreases from the first frequency to the third frequency, a plurality of first upper limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first output boundary value to the second output boundary value, and a plurality of first lower limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first input boundary value to the second output boundary value. When the operating frequency of the power grid is greater than or equal to the second frequency and less than or equal to a fourth frequency, the power regulation ratio of the energy storage system is greater than or equal to the second input boundary value and less than or equal to the first output boundary value. When the operating frequency increases from the second frequency to the fourth frequency, the plurality of second upper limits of the adjustment ratio corresponding to the change in operating frequency correspondingly decrease from the first output boundary value to the second input boundary value, and the plurality of second lower limits of the adjustment ratio corresponding to the change in operating frequency correspondingly decrease from the first input boundary value to the second input boundary value. The energy storage system includes an energy storage unit, a measuring unit, and a control unit. The energy storage unit is used to store and provide electrical energy. The measuring unit is used to measure the operating frequency of the power grid. The control unit is coupled to the measuring unit and the energy storage unit and is used to receive the operating frequency of the power grid measured by the measuring unit. When the state of charge of the energy storage unit is greater than a first charge, the energy storage unit is in a normal charge state; when the state of charge of the energy storage unit is less than the first charge, the energy storage unit is in a low charge state. When the control unit sets the adjustment ratio of the energy storage system's power regulation to be greater than 0, the control unit sets the energy storage unit to supply power to the power grid at the adjustment ratio of the agreed capacity. When the control unit sets the adjustment ratio of the energy storage system's power regulation to be less than 0, the control unit sets the energy storage unit to charge from the power grid at the adjustment ratio of the agreed capacity.The operating method includes: when the operating frequency of the power grid measured by the measurement unit is greater than or equal to a first frequency boundary value and less than or equal to a second frequency boundary value, configuring the control unit to set the power regulation adjustment ratio to a first operating ratio, wherein the first operating ratio is less than or equal to 0 and greater than or equal to a first input boundary value, the first frequency boundary value is less than the first frequency, and / or the second frequency boundary value is greater than the second frequency; and when the operating frequency of the power grid measured by the measurement unit is greater than or equal to a third frequency boundary value and less than or equal to a fourth frequency, configuring the control unit to set the power regulation adjustment ratio to be less than or equal to a second operating ratio and greater than or equal to the second input boundary value, wherein the third frequency boundary value is greater than the second frequency boundary value, the second operating ratio is less than the first operating ratio, and a second efficiency value of charging the energy storage unit from the power grid at the second operating ratio is greater than a first efficiency threshold value compared to a first efficiency value of charging the energy storage unit from the power grid at the first operating ratio.

[0007] The aforementioned embodiments can improve the efficiency of the energy storage system and can optimize and adjust the batteries of the energy storage system to optimize the battery life, thereby achieving power optimization and reducing power loss. Simple diagram description

[0008] FIG1 is a schematic diagram of the architecture of an energy storage system according to an embodiment of the present invention.

[0009] FIG. 2 illustrates an embodiment of the energy storage unit of FIG. 1 .

[0010] FIG3 is a schematic diagram showing a reference relationship between the regulation ratio of power regulation provided by the energy storage system and the operating frequency of the power grid.

[0011] 4A is a schematic diagram of an embodiment of an adjustment ratio of power regulation provided by an energy storage system corresponding to the operating frequency of a power grid when the energy storage unit is in a normal power state.

[0012] FIG4B is a schematic diagram of an embodiment of the efficiency of the energy storage system and the adjustment ratio of the power regulation provided by the energy storage unit when the energy storage unit is in a normal power state.

[0013] FIG4C is a schematic diagram of another embodiment of the efficiency of the energy storage system and the adjustment ratio of the power regulation provided by the energy storage unit when the energy storage unit is in a normal power state.

[0014] 5A is a schematic diagram of another embodiment of an adjustment ratio of power regulation provided by an energy storage system corresponding to the operating frequency of a power grid when the energy storage unit is in a normal power state.

[0015] FIG5B is a schematic diagram of another embodiment of the efficiency of the energy storage system and the adjustment ratio of the power regulation provided by the energy storage unit when the energy storage unit is in a normal power state.

[0016] 6A is a schematic diagram of another embodiment of the adjustment ratio of the power regulation provided by the energy storage system corresponding to the operating frequency of the power grid when the energy storage unit is in a normal power state.

[0017] FIG6B is a schematic diagram of another embodiment of the efficiency of the energy storage system and the adjustment ratio of the power regulation provided by the energy storage unit when the energy storage unit is in a normal power state.

[0018] 7A is a schematic diagram of an embodiment of an adjustment ratio of power regulation provided by an energy storage system corresponding to the operating frequency of a power grid when an energy storage unit is in a low-power state.

[0019] FIG7B is a schematic diagram of an embodiment of the efficiency of the energy storage system and the adjustment ratio of the power regulation provided by the energy storage unit when the energy storage unit is in a low power state.

[0020] FIG8 is a schematic diagram of another embodiment of the adjustment ratio of the power regulation provided by the energy storage system corresponding to the operating frequency of the power grid when the energy storage unit is in a low-power state.

[0021] 9A is a schematic diagram of an embodiment of an adjustment ratio of power regulation provided by an energy storage system corresponding to the operating frequency of a power grid when the energy storage unit is in a high power state.

[0022] FIG9B is a schematic diagram of an embodiment of the efficiency of the energy storage system and the adjustment ratio of the power regulation provided by the energy storage unit when the energy storage unit is in a high power state.

[0023] FIG10 is a schematic diagram of another embodiment of the adjustment ratio of the power regulation provided by the energy storage system corresponding to the operating frequency of the power grid when the energy storage unit is in a high power state. Implementation Method

[0024] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following sections. It should be understood that this invention can have various variations in different aspects without departing from the scope of this invention.

[0025] Figure 1 is a schematic diagram of the architecture of an embodiment of the energy storage system of this invention. As shown in Figure 1 , energy storage system 1 is coupled to power grid 3 via grid connection point 2 to provide power conditioning for grid 3. The maximum power conditioning provided by energy storage system 1 is an agreed capacity. For example, the agreed capacity of energy storage system 1 can be set to the volume accepted by the power company. In this embodiment, energy storage system 1 includes an energy storage unit 11, a measurement unit 12, a control unit 13, and an auxiliary power supply device 14. Energy storage unit 11, measurement unit 12, and auxiliary power supply device 14 are respectively coupled to grid connection point 2, and control unit 13 is coupled to energy storage unit 11 and measurement unit 12. For simplicity and ease of illustration, other components of energy storage system 1 are not shown in Figure 1. In this embodiment, energy storage system 1 is divided into energy storage unit 11, measurement unit 12, control unit 13, and auxiliary power supply device 14 to clearly illustrate the operation of energy storage system 1. Each component of energy storage system 1 can be configured in an appropriate number, for example, one or more auxiliary power supply devices. Furthermore, the above units may be implemented separately using appropriate components, or may be integrated or implemented separately using one or more components. For example, the measurement unit 12 and the control unit 13 may perform their functions in the same circuit composed of discrete components and / or integrated circuit components.

[0026] The measurement unit 12 can be an electric meter or other suitable measuring device. It can measure electrical parameters at the grid connection point 2 or other suitable locations through direct or indirect coupling to obtain operating information such as the voltage, frequency, and power of the power grid 3. The control unit 13 can include components such as logic circuits to control the operation of the energy storage unit 11. For example, the control unit 13 receives information such as the operating frequency and / or voltage of the power grid 3 measured by the measurement unit 12 and obtains the state of charge of the energy storage unit 11. Based on this information, the control unit 13 controls the energy storage unit 11 to supply power to or receive power from the power grid 3, thereby achieving power regulation of the power grid 3. The auxiliary power supply device 14 can adopt a suitable power conversion architecture to provide the required auxiliary voltage, which is used to power internal components of the energy storage system 1, such as the cooling system, communications equipment, fire protection equipment, and sensors.

[0027] In the embodiment shown in FIG. 1 , the energy storage unit 11 of the energy storage system 1 includes a plurality of energy storage devices 11_1, 11_2, ..., 11_n. The number of energy storage units 11 in the energy storage system 1 of the present invention is not limited, and the energy storage unit 11 can be configured to include one or more energy storage devices.

[0028] An energy storage device can employ a suitable architecture to provide energy storage functionality. Figure 2 illustrates a possible implementation of the energy storage device 11_n of Figure 1 . In the implementation shown in Figure 2 , the energy storage device 11_n comprises a plurality of battery modules 111, a plurality of power conditioners 112, and a transformer 113. The plurality of battery modules 111 are electrically connected to the plurality of power conditioners 112, which are electrically connected to the transformer 113, which is electrically connected to the grid connection point 2. The battery module 111 can be implemented using lithium batteries, solid-state batteries, fuel cells, or thermal batteries. In some embodiments, the battery module 111 further includes a DC-DC converter (direct current to direct current converter) for converting electrical energy provided by the energy storage battery into an appropriate voltage for supply to the power conditioner 112, or for converting electrical energy received from the power conditioner 112 into an appropriate voltage for storage in the battery module 111, thereby ensuring voltage stability. The power conditioner 112 is used to perform bidirectional power conversion and can be, for example, a bidirectional DC / AC converter. The transformer 113 is used to transmit and adjust the voltage of alternating current (AC) and can be configured with isolation or a non-isolated architecture. In the embodiment shown in FIG2 , the transformer 113 can be a multi-winding transformer having multiple windings on the side connected to the plurality of power conditioners 112. In another embodiment, the energy storage device 11_n includes multiple transformers. In another embodiment, the energy storage device includes an electrically connected battery module 111, a power conditioner 112, and a transformer 113, wherein the transformer 113 is electrically connected to the grid connection point 2. In another embodiment, the energy storage device includes an electrically connected battery module 111 and a power conditioner 112, wherein the power conditioner 112 is electrically connected to the grid connection point 2. The power conditioner 112 provides power to or receives power from the grid 3 directly through the grid connection point 2, without passing through a transformer.

[0029] Grid ancillary services regulations may vary across regions or power companies. Referring to the embodiment of Figure 3, a schematic diagram illustrating the reference relationship between the power regulation ratio provided by energy storage system 1 and the operating frequency of power grid 3 is shown, showing the upper and lower limits of the power regulation ratio provided by energy storage system 1 for different operating frequencies of power grid 3. The power regulation ratio provided by energy storage system 1 is controlled by its control unit 13, with the maximum power regulation value being an agreed capacity (e.g., a 10MW power regulation capacity agreed with the power company). When the control unit 13 sets the power regulation ratio of the energy storage system 1 to be greater than 0 (i.e., greater than 0 and less than or equal to 100%), the control unit 13 sets the energy storage unit 11 to supply power to the grid 3 at the agreed capacity regulation ratio. When the control unit 13 sets the power regulation ratio of the energy storage system 1 to be less than 0 (i.e., less than 0 and greater than or equal to -100%), the control unit 13 sets the energy storage unit 11 to charge from the grid 3 at the absolute value of the agreed capacity regulation ratio (for ease of explanation, the "absolute value of the regulation ratio" will be omitted in the following paragraphs when referring to the energy storage unit 11 charging from the grid 3). It should be noted that the curve in FIG. 3 is formed by connecting a plurality of discrete reference points, each of which represents the upper limit and / or lower limit of the regulation ratio corresponding to an operating frequency.

[0030] To comply with the power regulation specifications of Figure 3 , when the operating frequency of grid 3 is greater than or equal to the first frequency fr1 and less than or equal to the second frequency fr2, the power regulation ratio of energy storage system 1 should be set to be greater than or equal to the first input limit value IL1 and less than or equal to the first output limit value OL1. f0 in Figure 3 can be the preset power supply frequency of grid 3, for example, 50 Hz or 60 Hz.

[0031] When the operating frequency of power grid 3 is greater than or equal to the third frequency fr3 and less than or equal to the first frequency fr1, the power regulation ratio of energy storage system 1 should be set to be greater than or equal to the first input boundary value IL1 and less than or equal to the second output boundary value OL2. When the operating frequency decreases from the first frequency fr1 to the third frequency fr3, the plurality of first upper limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first output boundary value OL1 to the second output boundary value OL2, and the plurality of first lower limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first input boundary value IL1 to the second output boundary value OL2.

[0032] When the operating frequency of power grid 3 is greater than or equal to the second frequency fr2 and less than or equal to the fourth frequency fr4, the power regulation ratio of energy storage system 1 should be set to be greater than or equal to the second input boundary value IL2 and less than or equal to the first output boundary value OL1. When the operating frequency increases from the second frequency fr2 to the fourth frequency fr4, the plurality of second upper limits of the regulation ratio corresponding to the change in operating frequency correspondingly decrease from the first output boundary value OL1 to the second input boundary value IL2, and the plurality of second lower limits of the regulation ratio corresponding to the change in operating frequency correspondingly decrease from the first input boundary value IL1 to the second input boundary value IL2.

[0033] When the operating frequency of power grid 3 is greater than or equal to the fifth frequency fr5 and less than or equal to the third frequency fr3, the power regulation ratio of energy storage system 1 should be set to be greater than or equal to the second output limit value OL2 and less than or equal to the third output limit value OL3. When the operating frequency decreases from the third frequency fr3 to the fifth frequency fr5, the regulation ratio corresponding to the change in operating frequency increases from the second output limit value OL2 to the third output limit value OL3. When the operating frequency of power grid 3 is less than the fifth frequency fr5, the power regulation ratio of energy storage system 1 should be set to be equal to the third output limit value OL3.

[0034] When the operating frequency of power grid 3 is greater than or equal to the fourth frequency fr4 and less than or equal to the sixth frequency fr6, the power regulation ratio of energy storage system 1 should be set to be greater than or equal to the third input boundary value IL3 and less than or equal to the second input boundary value IL2. When the operating frequency increases from the fourth frequency fr4 to the sixth frequency fr6, the regulation ratio corresponding to the change in operating frequency correspondingly decreases from the second input boundary value IL2 to the third input boundary value IL3. When the operating frequency of power grid 3 is greater than the sixth frequency fr6, the power regulation ratio of energy storage system 1 should be set to be equal to the third input boundary value IL3.

[0035] In the embodiment of Figure 3 , the magnitudes of the boundary values ​​are OL3 > OL2 > OL1 > IL1 > IL2 > IL3, and the magnitudes of the frequencies are fr6 > fr4 > fr2 > f0 > fr1 > fr3 > fr5. However, the specific values ​​of the aforementioned frequencies, input boundary values, and output boundary values ​​depend on the frequency response specifications for grid ancillary services in each region or power company. However, the relative magnitudes of the frequencies and the relative magnitudes of the input boundary values ​​and output boundary values ​​can be similar to those shown in Figure 3 .

[0036] During the operation of the energy storage system 1, the control unit 13 can set the power regulation ratio of the energy storage system 1 based on conditions such as the state of charge of the energy storage unit 11, the operating frequency of the power grid 3, and the efficiency of the energy storage system 1, so that the energy storage unit 11 can supply power to the power grid 3 or charge from the power grid 3 at the agreed capacity regulation ratio. The specific setting method is illustrated below.

[0037] The control unit 13 evaluates the state of charge (SOC) of the energy storage unit 11. For example, when the SOC of the energy storage unit 11 is greater than a first charge, the control unit 13 determines that the energy storage unit 11 is in a normal charge state. When the SOC of the energy storage unit 11 is less than the first charge, the control unit 13 determines that the energy storage unit 11 is in a low charge state. When the SOC of the energy storage unit 11 is greater than a second charge (where the second charge is greater than the first charge), the control unit 13 determines that the energy storage unit 11 is in a high charge state. The specific values ​​of the first and second charges can be determined based on actual needs. In another embodiment, the energy storage system 1 can be configured to provide power regulation functions corresponding to one or more of three states, for example, power regulation only corresponding to normal and low charge states, power regulation only corresponding to high and low charge states, or power regulation only corresponding to normal and high charge states, and power regulation functions are provided using the following methods for each SOC.

[0038] Figure 4A is a schematic diagram illustrating an embodiment of the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a normal power state. The curve in Figure 4A is formed by connecting a plurality of discrete operating points, each of which represents the regulation ratio corresponding to an operating frequency. When the energy storage unit 11 is in a normal power state, as shown in Figure 4A , when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the first frequency boundary value f11 and less than or equal to the second frequency boundary value f12 (i.e., between operating points 1E and 1F), the control unit 13 sets the power regulation ratio to a first operating ratio R11, where the first operating ratio R11 is less than or equal to 0 and greater than or equal to the first input boundary value IL1. Furthermore, the control unit 13 sets the first frequency boundary value f11 to be less than the first frequency fr1 and / or sets the second frequency boundary value f12 to be greater than the second frequency fr2. In this embodiment, at least one of the first two conditions is met. In some embodiments, the control unit 13 sets the first operating ratio R11 to zero, meaning that the energy storage system 1 neither supplies power to the grid 3 nor receives power from the grid 3. In other embodiments, the energy storage system 1 includes an auxiliary power supply device 14 (as shown in FIG1 ). Therefore, the control unit 13 sets the first operating ratio R11 to less than zero, so that the input power received by the energy storage system 1 from the grid 3 is greater than or equal to the auxiliary power required by the auxiliary power supply device 14. In this case, the auxiliary power supply device 14 is effectively powered directly from the grid 3. In frequency ranges where power regulation is not required, setting the first operating ratio R11 to less than zero allows the grid 3 to directly power the auxiliary power supply device 14. This not only reduces the burden on the grid 3 but also avoids energy loss by first storing power in the energy storage unit 11 before supplying it to the auxiliary power supply device 14. This also prevents unnecessary charging and discharging, thereby extending the service life of the energy storage unit 11.

[0039] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the third frequency boundary f13 (i.e., between the operating points 1A and 1D), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the second output boundary OL2 and greater than or equal to the second operating ratio R12, where the third frequency boundary f13 is greater than the third frequency fr3 and less than the first frequency boundary f11. The second operating ratio R12 is greater than the first operating ratio R11, and the efficiency of the energy storage system 1 supplying power to the power grid 3 at the second operating ratio R12 is greater than the efficiency of the energy storage system 1 supplying power to the power grid 3 at the first operating ratio R11, which is greater than a first efficiency threshold TH1. As shown in FIG4A , when the operating frequency of the power grid 3 decreases from the first frequency boundary f11 to the third frequency boundary f13, the power regulation adjustment ratio correspondingly jumps from the first operating ratio R11 to the second operating ratio R12.

[0040] When the energy storage unit 11 is in a normal charge state, and the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency boundary value f14 and less than or equal to the third frequency boundary value f13 (i.e., between operating points 1C and 1D), the control unit 13 sets the power regulation adjustment ratio to be substantially equal to (i.e., within an allowable error range) the first upper limit value corresponding to the operating frequency. Furthermore, the control unit 13 sets the fourth frequency boundary value f14 to be greater than the third frequency boundary value f13 and less than the third frequency boundary value f13. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fifth frequency boundary value f15 and less than or equal to the fourth frequency boundary value f14 (i.e., between operating points 1B and 1C), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the first upper limit value corresponding to the operating frequency at the fifth frequency boundary value f15 and greater than or equal to the first upper limit value corresponding to the operating frequency at the fourth frequency boundary value f14. Furthermore, the control unit 13 sets the power regulation adjustment ratio to increase or remain constant as the operating frequency decreases (maintaining a constant ratio is used as an example in FIG4A ). Furthermore, the control unit 13 sets the fifth frequency limit f15 to be greater than the third frequency fr3 and less than the fourth frequency limit f14. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the fifth frequency limit f15 (i.e., between the operating point 1A and the operating point 1B), the control unit 13 sets the power regulation adjustment ratio to increase as the operating frequency decreases. For example, the power regulation adjustment ratio is set to be substantially equal to the first lower limit corresponding to the operating frequency.

[0041] When the operating frequency of the power grid 3 measured by the measurement unit 12 is less than or equal to the third frequency fr3, in this embodiment, the power company does not provide the energy storage system 1 with any adjustment space (see FIG. 3 ). Therefore, the relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3 is the same as shown in FIG. 3 .

[0042] Furthermore, when the energy storage unit 11 is in a normal charge state, and the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary value f16 and less than or equal to the fourth frequency fr4 (i.e., between the operating points 1G and 1J), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the fourth operating ratio R14 and greater than or equal to the second input boundary value IL2, wherein the sixth frequency boundary value f16 is greater than the second frequency boundary value f12 and less than the fourth frequency fr4. The fourth operating ratio R14 is less than the first operating ratio R11, and the efficiency of the energy storage unit 11 charging from the power grid 3 at the fourth operating ratio R14 is greater than the efficiency of the energy storage unit 11 charging from the power grid 3 at the first operating ratio R11 by a second efficiency threshold TH2. As shown in FIG. 4A , when the operating frequency of the power grid 3 increases from the second frequency boundary value f12 to the sixth frequency boundary value f16, the power regulation adjustment ratio is correspondingly reduced from the first operating ratio R11 to the fourth operating ratio R14.

[0043] When the energy storage unit 11 is in a normal power state, and the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary value f16 and less than or equal to the seventh frequency boundary value f17 (i.e., between operating points 1G and 1H), the control unit 13 sets the power regulation adjustment ratio to be substantially equal to the second lower limit corresponding to the operating frequency. Furthermore, the control unit 13 sets the seventh frequency boundary value f17 to be greater than the sixth frequency boundary value f16 and less than the fourth frequency fr4. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the seventh frequency boundary value f17 and less than or equal to the eighth frequency boundary value f18 (i.e., between operating points 1H and 1I), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the second lower limit corresponding to the operating frequency at the seventh frequency boundary value f17 and greater than or equal to the second lower limit corresponding to the operating frequency at the eighth frequency boundary value f18. Furthermore, the control unit 13 sets the power regulation adjustment ratio to decrease or remain constant as the operating frequency increases (maintaining a constant ratio is used as an example in FIG4A ). Furthermore, the control unit 13 sets the eighth frequency boundary value f18 to be greater than the seventh frequency boundary value f17 and less than the fourth frequency fr4. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the eighth frequency boundary value f18 and less than or equal to the fourth frequency fr4 (i.e., between the operating point 1I and the operating point 1J), the control unit 13 sets the power regulation adjustment ratio to decrease as the operating frequency increases. For example, the power regulation adjustment ratio is set to be substantially equal to the second upper limit corresponding to the operating frequency.

[0044] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency fr4, in this embodiment, the power company does not provide the energy storage system 1 with any adjustment space (see FIG. 3 ). Therefore, the relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3 is the same as shown in FIG. 3 .

[0045] Figure 4B is a schematic diagram of an embodiment of the charge-discharge efficiency of the energy storage system 1 and the adjustment ratio of the power it provides when the energy storage unit 11 is in a normal charge state. The right curve in Figure 4B represents the power supply efficiency curve when the energy storage system 1 supplies power to the grid 3, while the left curve in Figure 4B represents the charging efficiency curve when the energy storage system 1 charges the energy storage unit 11 from the grid 3. The power supply efficiency curve and charging efficiency curve in Figure 4B are not necessarily linear or symmetrical. If the energy storage system 1 selects a poor adjustment ratio, it will result in poor efficiency and may even cause wear and tear on the energy storage system 1, reducing its charge-discharge performance and service life. For example, when the operating frequency of the grid 3 is the first frequency limit value f11, although the energy storage system 1 can select the adjustment ratio of the first output limit value OL1 to supply power to the grid 3, as shown in Figure 4B, the efficiency of the energy storage system 1 is still poor when supplying power at the adjustment ratio of the first output limit value OL1. Therefore, in this embodiment, the energy storage system 1 waits until the operating frequency of the power grid 3 drops to the third frequency boundary value f13 before supplying power to the power grid 3 at the second operating ratio R12. As shown in FIG4B , compared to the adjustment ratio corresponding to the first output boundary value OL1, the energy storage system 1 corresponding to the second operating ratio R12 has higher operating efficiency and can more efficiently supply power to the power grid 3. Referring to FIG3 , 4A , and 4B , in one embodiment, when the energy storage unit 11 is in a normal power state, when the operating frequency of the power grid 3 decreases from the third frequency boundary value f13 to the third frequency fr3 , the efficiency of the first upper limit of the adjustment ratio corresponding to the operating frequency may decrease in some sections as the operating frequency decreases (as shown in the curve corresponding to the adjustment ratio in FIG4B for the section between the second operating ratio R12, the third operating ratio R13, and the second output boundary value OL2 ). Therefore, the energy storage system 1 needs to select the adjustment ratio with the optimal efficiency value to supply power to the power grid 3. For example, when the operating frequency of the power grid 3 is between the third frequency boundary value f13 and the fourth frequency boundary value f14, the energy storage system 1 can use the first upper limit of these adjustment ratios to supply power to the power grid 3. The corresponding efficiency curve in FIG4B is a rising curve corresponding to the adjustment ratio in the section between the second operating ratio R12 and the third operating ratio R13. Because the efficiency value corresponding to the adjustment ratio of the third operating ratio R13 is substantially optimal, and the corresponding efficiency value begins to decline when the adjustment ratio exceeds the third operating ratio R13, when the operating frequency of the power grid 3 is between the fourth frequency boundary value f14 and the fifth frequency boundary value f15, the energy storage system 1 supplies power to the power grid 3 using the adjustment ratio of the third operating ratio R13.When the operating frequency of grid 3 is between the fifth frequency boundary value f15 and the third frequency fr3, since the regulation ratio of energy storage system 1 must be greater than or equal to the first lower limit of the regulation ratio, energy storage system 1 uses the first lower limit of the regulation ratio substantially corresponding to these regulation ratios to supply power to grid 3. The corresponding efficiency curve in FIG4B is the curve corresponding to the regulation ratio between the third operating ratio R13 and the second output boundary value OL2. In one embodiment, the first lower limit of the regulation ratio corresponding to the fifth frequency boundary value f15 may be greater than the third operating ratio R13. Therefore, when the operating frequency of grid 3 is at the fifth frequency boundary value f15, energy storage system 1 must supply power to grid 3 at the first lower limit of the regulation ratio substantially corresponding to the operating frequency.

[0046] In one embodiment, the third frequency boundary value f13 is selected based on the difference between the efficiency of the energy storage system 1 at the second operating ratio R12 and the efficiency at the first operating ratio R11 being greater than the first efficiency threshold TH1. Specifically, the third frequency boundary value f13 corresponding to the second operating ratio R12 is selected only if the difference between the efficiency of the energy storage system 1 at the second operating ratio R12 and the efficiency at the first operating ratio R11 is greater than the first efficiency threshold TH1. In another embodiment, when the operating frequency of the power grid 3 is between the first critical frequency fx and the preset power supply frequency f0 (see FIG3 ), the power provided by the energy storage system 1 is always regulated at the first operating ratio R11. When the operating frequency of the power grid 3 drops to or below the first critical frequency fx, the energy storage system 1 must supply power to the power grid 3 at a regulation ratio greater than or equal to zero. At this point, the energy storage system 1 selects the regulation ratio corresponding to the highest efficiency within the allowable regulation ratio range as the second operating ratio R12 to supply power to the power grid 3.

[0047] Similarly, when the energy storage unit 11 is charging from the grid 3, when the operating frequency of the grid 3 is at the second frequency limit f12, the energy storage system 1 can choose to charge the energy storage unit 11 from the grid 3 at the adjustment ratio of the first input limit IL1. However, as shown in FIG4B , when the energy storage unit 11 is charged from the grid 3 at the adjustment ratio of the first input limit IL1, the efficiency of the energy storage system 1 is still poor. Therefore, in this embodiment, the energy storage system 1 waits until the operating frequency of the grid 3 rises to the sixth frequency limit f16 before charging the energy storage unit 11 from the grid 3 at the adjustment ratio of the fourth operating ratio R14. As shown in FIG4B , compared to the adjustment ratio of the first input limit IL1, the energy storage system 1 operating efficiency corresponding to the fourth operating ratio R14 is higher, allowing the energy storage unit 11 to charge from the grid 3 more efficiently. Referring to Figures 3, 4A, and 4B, in one embodiment, when the energy storage unit 11 is in a normal state of charge, when the operating frequency of the power grid 3 increases from the sixth frequency boundary value f16 to the fourth frequency fr4, the efficiency of the second lower limit of the adjustment ratio corresponding to this operating frequency may decrease in some sections as the operating frequency increases (as shown in the curve corresponding to the section of the adjustment ratio between the fourth operating ratio R14, the fifth operating ratio R15, and the second input boundary value IL2 in Figure 4B). Therefore, the energy storage system 1 needs to select the adjustment ratio with the best efficiency value to charge the energy storage unit 11 from the power grid 3. For example, when the operating frequency of the power grid 3 is between the sixth frequency boundary value f16 and the seventh frequency boundary value f17, the energy storage unit 11 can be supplied from the power grid 3 using the second lower limit of these adjustment ratios. The corresponding efficiency curve in Figure 4B is the rising curve corresponding to the section of the adjustment ratio between the fourth operating ratio R14 and the fifth operating ratio R15. Since the efficiency value corresponding to the fifth operating ratio R15 is substantially optimal, and the corresponding efficiency value begins to decline when the adjustment ratio is less than the fifth operating ratio R15, when the operating frequency of the power grid 3 is between the seventh frequency boundary value f17 and the eighth frequency boundary value f18, the energy storage unit 11 is charged from the power grid 3 at the adjustment ratio of the fifth operating ratio R15. When the operating frequency of the power grid 3 is between the eighth frequency boundary value f18 and the fourth frequency fr4, since the adjustment ratio of the energy storage system 1 must be less than or equal to the second upper limit of the adjustment ratio, the energy storage unit 11 is charged from the power grid 3 using the second upper limit substantially corresponding to these adjustment ratios. The corresponding efficiency curve in FIG4B is the curve corresponding to the adjustment ratio between the fifth operating ratio R15 and the second input boundary value IL2. In one embodiment, the second upper limit of the adjustment ratio corresponding to the eighth frequency boundary value f18 may be less than the fifth operating ratio R15. Therefore, when the operating frequency of the power grid 3 is at the eighth frequency boundary value f18, the energy storage unit 11 must be charged from the power grid 3 at the second upper limit of the adjustment ratio substantially corresponding to the operating frequency.

[0048] In one embodiment, the sixth frequency boundary value f16 is selected based on the difference between the efficiency of the energy storage system 1 at the fourth operating ratio R14 and the efficiency at the first operating ratio R11 being greater than the second efficiency threshold TH2. Specifically, the sixth frequency boundary value f16 corresponding to the fourth operating ratio R14 is selected only if the difference between the efficiency of the energy storage system 1 at the fourth operating ratio R14 and the efficiency at the first operating ratio R11 is greater than the second efficiency threshold TH2. In another embodiment, when the operating frequency of the power grid 3 is between the second critical frequency fy and the predetermined power supply frequency f0 (see FIG. 3 ), the power provided by the energy storage system 1 is always regulated at the first operating ratio R11. When the operating frequency of the power grid 3 rises to or above the second critical frequency fy, the energy storage unit 11 must be charged from the power grid 3 at a regulation ratio less than or equal to zero. At this point, the energy storage system 1 selects the regulation ratio corresponding to the highest efficiency within the allowable regulation ratio range to charge the energy storage unit 11 from the power grid 3.

[0049] FIG4C is a schematic diagram of another embodiment of the charge and discharge efficiency of the energy storage system 1 and the adjustment ratio of the power it provides when the energy storage unit 11 is in a normal charge state. Compared to the embodiment of FIG4B , the efficiency values ​​corresponding to the third operating ratio R13 and / or the second output boundary value OL2 in the power supply efficiency curve of the embodiment of FIG4C do not reach the optimal value; and the efficiency values ​​corresponding to the fifth operating ratio R15 and / or the second input boundary value IL2 in the charging efficiency curve do not reach the optimal value. In the embodiment of FIG4C , the efficiency of the third operating ratio R13 and / or the fifth operating ratio R15 may not be optimal due to performance limitations of the energy storage system 1, to protect the service life of the energy storage unit 11, or other design considerations. For example, the third operating ratio R13 and the fifth operating ratio R15 may be set equal to the second operating ratio R12 and the fourth operating ratio R14, respectively. However, the energy storage system 1 waits until the operating frequency of the grid 3 drops to the third frequency limit value f13 before increasing from the first operating ratio R11 to the second operating ratio R12 to supply power to the grid 3. Alternatively, the energy storage system 1 waits until the operating frequency of the grid 3 rises to the sixth frequency limit value f16 before decreasing from the first operating ratio R11 to the fourth operating ratio R14 to charge from the grid 3. Both of these methods optimize the energy storage system 1 by improving the power supply efficiency and / or charging efficiency, thereby extending the service life of the energy storage unit 11 and reducing power loss.

[0050] In other embodiments, the power regulation ratio provided by the energy storage system 1 can also be adjusted accordingly based on the efficiency curve of the energy storage system 1. For example, FIG5A is a schematic diagram illustrating another embodiment of the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a normal power state. FIG5B is a schematic diagram illustrating another embodiment of the efficiency of the energy storage system 1 and the power regulation ratio provided by the energy storage system 1 when the energy storage unit 11 is in a normal power state. Similar operating points to those in FIG4A are denoted by the same reference numerals and are not further described here. However, in this embodiment, as shown in FIG5A and FIG5B , when the energy storage system 1 supplies power to the power grid 3, the energy storage system 1 achieves a better or optimal efficiency when supplying power to the power grid 3 at the regulation ratio of the second output limit value OL2. Correspondingly, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the third frequency boundary f13 (i.e., between operating points 1A and 1D), the control unit 13 sets the power regulation ratio to be substantially equal to the first upper limit corresponding to the operating frequency, thereby optimizing the efficiency of the energy storage system 1. Furthermore, when the energy storage unit 11 is charging from the power grid 3, the energy storage system 1 has better or optimal efficiency when the energy storage unit 11 is charging from the power grid 3 at the regulation ratio of the second input boundary IL2. Correspondingly, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary f16 and less than or equal to the fourth frequency fr4 (i.e., between operating points 1G and 1J), the control unit 13 sets the power regulation ratio to be substantially equal to the second lower limit corresponding to the operating frequency, thereby optimizing the efficiency of the energy storage system 1.

[0051] According to another embodiment, the efficiency curve of the energy storage system 1 is shown in Figure 6A, which shows the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a normal state of charge. Figure 6B shows the efficiency of the energy storage system 1 and the power regulation ratio provided when the energy storage unit 11 is in a normal state of charge. Similar operating points to those in Figure 4A are denoted by the same reference numerals and are not further described here. However, in this embodiment, as shown in Figures 6A and 6B, when the energy storage system 1 supplies power to the power grid 3, the energy storage system 1 achieves optimal efficiency when supplying power to the power grid 3 at the regulation ratio of the second operating ratio R12. Therefore, as the operating frequency of the power grid 3 decreases from the third frequency boundary value f13 to the third frequency fr3, the energy storage system 1 supplies power to the power grid 3 at the regulation ratio of the second operating ratio R12 until the energy storage system 1 must supply power to the power grid 3 at the lower limit of the regulation ratio. Specifically, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency boundary value f14a and less than or equal to the third frequency boundary value f13 (i.e., between operating points 1Ba and 1D), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the first upper limit value corresponding to the operating frequency at the fourth frequency boundary value f14a and greater than or equal to the first upper limit value corresponding to the operating frequency at the third frequency boundary value f13. The control unit 13 also sets the power regulation adjustment ratio to increase or remain constant as the operating frequency decreases (using the example of maintaining constant in FIG6A ). Furthermore, the control unit 13 sets the fourth frequency boundary value f14a to be greater than the third frequency fr3 and less than the third frequency boundary value f13. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the fourth frequency boundary value f14a (i.e., between operating points 1A and 1Ba), the control unit 13 sets the power regulation adjustment ratio to increase as the operating frequency decreases, for example, setting the power regulation adjustment ratio to be substantially equal to the first lower limit value corresponding to the operating frequency. In another embodiment, similar to the embodiment of FIG. 4C , the efficiency value corresponding to the second operating ratio R12 and / or the second output boundary value OL2 may not yet reach the optimal value due to performance limitations of the energy storage system 1, protecting the service life of the energy storage unit 11, or other design considerations. However, the energy storage system 1 jumps from the first operating ratio R11 to the second operating ratio R12 to supply power to the grid 3. By improving the power supply efficiency, the energy storage system 1 can be optimized and adjusted, thereby extending the service life of the energy storage unit 11 and reducing power loss.

[0052] Similarly, when the energy storage unit 11 is charging from the grid 3, the energy storage system 1 achieves optimal efficiency when the energy storage unit 11 is charging from the grid 3 at the fourth operating ratio R14. Therefore, as the operating frequency of the grid 3 increases from the sixth frequency boundary value f16 to the fourth frequency fr4, the energy storage unit 11 is charged from the grid 3 at the fourth operating ratio R14, until the energy storage unit 11 must charge from the grid 3 at the upper limit of the operating ratio. Specifically, when the operating frequency of the grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary value f16 and less than or equal to the seventh frequency boundary value f17a (i.e., between the operating points 1G and 11a), the control unit 13 sets the power regulation ratio to be less than or equal to the second lower limit corresponding to the operating frequency at the sixth frequency boundary value f16 and greater than or equal to the second lower limit corresponding to the operating frequency at the seventh frequency boundary value f17a. Furthermore, the control unit 13 sets the power regulation ratio to decrease or remain constant as the operating frequency increases (maintaining constant is used as an example in FIG6A ). Furthermore, the control unit 13 sets the seventh frequency boundary value f17a to be greater than the sixth frequency boundary value f16 and less than the fourth frequency fr4. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the seventh frequency boundary value f17a and less than or equal to the fourth frequency fr4 (i.e., between the operating point 11a and the operating point 1J), the control unit 13 sets the power regulation adjustment ratio to decrease as the operating frequency increases. For example, the power regulation adjustment ratio is set to be substantially equal to the second upper limit corresponding to the operating frequency. In another embodiment, similar to the embodiment of FIG4C , the efficiency corresponding to the fourth operating ratio R14 and / or the second input boundary value IL2 may not yet reach the optimal value due to performance limitations of the energy storage system 1, protecting the service life of the energy storage unit 11, or other design considerations. However, the energy storage system 1 is charged from the power grid 3 at the fourth operating ratio R14 by reducing the first operating ratio R11. This improves the charging efficiency, optimizes the regulation of the energy storage system 1, extends the service life of the energy storage unit 11, and reduces power loss.

[0053] FIG7A is a schematic diagram illustrating an embodiment of the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a low-battery state. The curve in FIG7A is formed by connecting a plurality of discrete operating points, each of which represents the regulation ratio corresponding to an operating frequency. When the energy storage unit 11 is in a low-battery state, as shown in FIG7A , when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the first frequency boundary value f21 and less than or equal to the second frequency boundary value f22 (i.e., between operating points 2D and 2E, for example, the second frequency boundary value f22 can be set to the preset power supply frequency f0, set to be less than the preset power supply frequency f0, or set to the first frequency boundary value f21), the control unit 13 sets the power regulation ratio to a first operating ratio R21, where the first operating ratio R21 is less than or equal to 0 and greater than or equal to the first input boundary value IL1. Furthermore, the control unit 13 sets the first frequency boundary value f21 to be less than the first frequency fr1, and sets the second frequency boundary value f22 to be greater than the first frequency fr1 and less than the second frequency fr2. In some embodiments, the control unit 13 sets the first operating ratio R21 to zero, meaning that the energy storage system 1 neither supplies power to the grid 3 nor receives power from the grid 3. In other embodiments, the energy storage system 1 includes an auxiliary power supply device 14 (as shown in FIG1 ). Therefore, the control unit 13 sets the first operating ratio R21 to less than zero, so that the input power received by the energy storage system 1 from the grid 3 is greater than or equal to the auxiliary power required by the auxiliary power supply device 14. In this case, the auxiliary power supply device 14 is effectively powered directly by the grid 3. In frequency ranges where power regulation is not required, setting the first operating ratio R21 to less than zero allows the grid 3 to directly power the auxiliary power supply device 14. This not only reduces the burden on the grid 3 but also avoids energy loss by first storing power in the energy storage unit 11 before supplying it to the auxiliary power supply device 14. This also prevents unnecessary charging and discharging, thereby extending the service life of the energy storage unit 11.

[0054] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the third frequency boundary f23 (i.e., between the operating points 2A and 2Cb), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the second output boundary OL2 and greater than or equal to the second operating ratio R22, where the third frequency boundary f23 is greater than the third frequency fr3 and less than the first frequency boundary f21. The second operating ratio R22 is greater than the first operating ratio R21, and the efficiency of the energy storage system 1 supplying power to the power grid 3 at the second operating ratio R22 is greater than the efficiency of the energy storage system 1 supplying power to the power grid 3 at the first operating ratio R21, which is greater than a third efficiency threshold TH3. As shown in FIG7A , when the operating frequency of the power grid 3 decreases from the first frequency boundary f21 to the third frequency boundary f23, the power regulation adjustment ratio correspondingly jumps from the first operating ratio R21 to the second operating ratio R22.

[0055] In some embodiments, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency boundary value f24 and less than or equal to the third frequency boundary value f23 (i.e., between the operating points 2Ca and 2Cb), the control unit 13 sets the power regulation adjustment ratio to remain constant as the operating frequency decreases. Furthermore, the control unit 13 sets the fourth frequency boundary value f24 to be greater than the third frequency fr3 and less than the third frequency boundary value f23. By appropriately selecting the value of the third efficiency threshold TH3 and maintaining the adjustment ratio constant as the operating frequency decreases between the operating points 2Ca and 2Cb, the energy storage system 1 can provide power regulation for the power grid 3 with greater efficiency and lower discharge limits. This balances power regulation with the discharge capacity of the energy storage system 1, minimizing damage to the energy storage unit 11 due to excessively low charge.

[0056] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fifth frequency boundary value f25 and less than or equal to the fourth frequency boundary value f24 (i.e., between operating points 2B and 2Ca), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the first lower limit value corresponding to the operating frequency at the fifth frequency boundary value f25 and greater than or equal to the first lower limit value corresponding to the operating frequency at the fourth frequency boundary value f24. The control unit 13 also sets the power regulation adjustment ratio to increase as the operating frequency decreases. Furthermore, the control unit 13 sets the fifth frequency boundary value f25 to be greater than the third frequency fr3 and less than the fourth frequency boundary value f24. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the fifth frequency boundary value f25 (i.e., between operating points 2A and 2B), the control unit 13 sets the power regulation adjustment ratio to increase as the operating frequency decreases, for example, setting the power regulation adjustment ratio to be substantially equal to the first lower limit value corresponding to the operating frequency.

[0057] When the operating frequency of the power grid 3 measured by the measurement unit 12 is less than or equal to the third frequency fr3, in this embodiment, the power company does not provide the energy storage system 1 with any adjustment space (see FIG. 3 ). Therefore, the relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3 is the same as shown in FIG. 3 .

[0058] Furthermore, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary value f26 and less than or equal to the fourth frequency fr4 (i.e., between the operating points 2F and 2H), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the fourth operating ratio R24 and greater than or equal to the second input boundary value IL2, wherein the sixth frequency boundary value f26 is greater than the second frequency boundary value f22 and less than the fourth frequency fr4. The fourth operating ratio R24 is less than the first operating ratio R21, and the efficiency of the energy storage unit 11 charging from the power grid 3 at the fourth operating ratio R24 is greater than the efficiency of the energy storage unit 11 charging from the power grid 3 at the first operating ratio R21 by a fourth efficiency threshold TH4. As shown in FIG. 7A , when the operating frequency of the power grid 3 increases from the second frequency boundary value f22 to the sixth frequency boundary value f26, the power regulation adjustment ratio is correspondingly reduced from the first operating ratio R21 to the fourth operating ratio R24. In this embodiment, the fourth operating ratio R24 is substantially equal to the first input boundary value IL1.

[0059] In some embodiments, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary value f26 and less than or equal to the second frequency fr2 (i.e., between the operating point 2F and the operating point 2G), the control unit 13 sets the power regulation adjustment ratio to be substantially equal to the first input boundary value IL1. Furthermore, the control unit 13 sets the sixth frequency boundary value f26 to be greater than the second frequency boundary value f22 and less than the second frequency fr2. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the second frequency fr2 and less than or equal to the fourth frequency fr4, the control unit 13 sets the power regulation adjustment ratio to decrease as the operating frequency increases, for example, setting the power regulation adjustment ratio to be substantially equal to the second lower limit corresponding to the operating frequency.

[0060] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency fr4, in this embodiment, the power company does not provide the energy storage system 1 with any adjustment space (see FIG. 3 ). Therefore, the relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3 is the same as shown in FIG. 3 .

[0061] Figure 7B is a schematic diagram of an embodiment of the efficiency of the energy storage system 1 and the adjustment ratio of the power it provides when the energy storage unit 11 is in a low-charge state. The right curve in Figure 7B represents the power supply efficiency curve when the energy storage system 1 supplies power to the grid 3, while the left curve in Figure 7B represents the charging efficiency curve when the energy storage system 1 charges the energy storage unit 11 from the grid 3. The power supply efficiency curve and charging efficiency curve in Figure 7B are not necessarily linear or symmetrical. If the energy storage system 1 selects a poor adjustment ratio, the efficiency of the energy storage system 1 will be poor, and may even cause wear and tear on the energy storage system 1, reducing its charging and discharging performance and service life. For example, when the operating frequency of the grid 3 is the first frequency limit value f21, the energy storage system 1 can select the adjustment ratio of the first output limit value OL1 to supply power to the grid 3. However, as shown in Figure 7B, when the energy storage system 1 supplies power at the adjustment ratio of the first output limit value OL1, the efficiency of the energy storage system 1 is still poor. Therefore, in this embodiment, the energy storage system 1 waits until the operating frequency of the power grid 3 drops to the third frequency boundary value f23 before supplying power to the power grid 3 at the second operating ratio R22. As shown in FIG7B , compared to the adjustment ratio corresponding to the first output boundary value OL1, the energy storage system 1 corresponding to the second operating ratio R22 has higher operating efficiency and can more efficiently supply power to the power grid 3. Referring to FIG3 , 7A , and 7B , in one embodiment, when the energy storage unit 11 is in a low-charge state, when the operating frequency of the power grid 3 decreases from the third frequency boundary value f23 to the third frequency fr3 , the efficiency of the first upper limit of the adjustment ratio corresponding to this operating frequency may decrease in some sections as the operating frequency decreases (as shown in the curve corresponding to the section of the adjustment ratio between the second operating ratio R22, the third operating ratio R23, and the second output boundary value OL2 in FIG7B ). Therefore, the energy storage system 1 needs to balance efficiency with the energy storage unit 11's charge level to select an appropriate adjustment ratio for supplying power to the power grid 3. For example, when the operating frequency of grid 3 is between the third frequency boundary value f23 and the fourth frequency boundary value f24, energy storage system 1 maintains a fixed modulation ratio of the second operating ratio R22 to supply power to grid 3. This allows energy storage system 1 to discharge energy more efficiently and at a lower limit, providing power regulation for grid 3. This balances power regulation with the discharge capacity of energy storage system 1, minimizing damage to energy storage unit 11 due to low charge. When the operating frequency of grid 3 is between the fourth frequency boundary value f24 and the fifth frequency boundary value f25, the modulation ratio used by energy storage system 1 increases as the operating frequency of grid 3 decreases, gradually increasing the efficiency of energy storage system 1. The corresponding efficiency curve in FIG7B shows an upward curve corresponding to the modulation ratio between the second operating ratio R22 and the third operating ratio R23. The efficiency value corresponding to the modulation ratio of the third operating ratio R23 is substantially optimal. When the modulation ratio exceeds the third operating ratio R23, the corresponding efficiency value begins to decline.When the operating frequency of grid 3 is between the fifth frequency boundary value f25 and the third frequency fr3, since the regulation ratio of energy storage system 1 must be greater than or equal to the first lower limit of the regulation ratio, energy storage system 1 uses the first lower limit value substantially corresponding to these regulation ratios to supply power to grid 3. The corresponding efficiency curve in FIG7B is the curve corresponding to the regulation ratio section between the third operating ratio R23 and the second output boundary value OL2.

[0062] In one embodiment, the third frequency boundary value f23 is selected based on the difference between the efficiency of the energy storage system 1 at the second operating ratio R22 and the efficiency at the first operating ratio R21 being greater than a third efficiency threshold TH3. Specifically, the third frequency boundary value f23 corresponding to the second operating ratio R22 is selected only if the difference between the efficiency of the energy storage system 1 at the second operating ratio R22 and the efficiency at the first operating ratio R21 is greater than the third efficiency threshold TH3. In another embodiment, when the operating frequency of the power grid 3 is between the first critical frequency fx and the preset power supply frequency f0 (see FIG3 ), the power provided by the energy storage system 1 is always regulated at the first operating ratio R21. When the operating frequency of the power grid 3 drops to the first critical frequency fx, the energy storage system 1 must supply power to the power grid 3 at a regulation ratio greater than or equal to zero. At this point, the energy storage system 1 selects the regulation ratio corresponding to the highest efficiency within the allowable regulation ratio range as the second operating ratio R22 to supply power to the power grid 3.

[0063] When the energy storage unit 11 is charging from the grid 3, since the energy storage unit 11 is already in a low-charge state, the energy storage system 1 prioritizes increasing the charge level of the energy storage unit 11 when selecting the adjustment ratio. For example, when the operating frequency of the grid 3 is between the sixth frequency boundary value f26 and the second frequency fr2, the energy storage unit 11 is charged from the grid 3 at a value substantially corresponding to the lower limit of these adjustment ratios (i.e., the first input boundary value IL1). When the operating frequency of the grid 3 is between the second frequency fr2 and the fourth frequency fr4, the energy storage unit 11 is charged from the grid 3 at the second lower limit of the adjustment ratio substantially corresponding to the operating frequency.

[0064] Based on the low state of charge of the energy storage unit 11, the sixth frequency boundary value f26 can also be set as close as possible to the first frequency boundary value f21, thereby charging the energy storage unit 11 as quickly as possible to avoid damaging the energy storage unit 11. In another embodiment, to maximize the charge of the energy storage unit 11, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the first frequency boundary value f21 and less than or equal to the first frequency fr1, the control unit 13 sets the power regulation ratio equal to the fourth operating ratio R24 or the first input boundary value IL1. In another embodiment, similar to the embodiment of FIG4C , due to performance limitations of the energy storage system 1, protecting the service life of the energy storage unit 11, or other design considerations, the efficiency values ​​corresponding to the second operating ratio R22, the third operating ratio R23, and / or the second output boundary value OL2 in the power supply efficiency curve may not reach the optimal value; and / or the efficiency values ​​corresponding to the fourth operating ratio R24 and / or the second input boundary value IL2 in the charging efficiency curve may not reach the optimal value. However, the energy storage system 1 waits until the operating frequency of the grid 3 drops to the third frequency limit value f23 before increasing from the first operating ratio R21 to the second operating ratio R22 to supply power to the grid 3. Alternatively, the energy storage system 1 waits until the operating frequency of the grid 3 rises to the sixth frequency limit value f26 before decreasing from the first operating ratio R21 to the fourth operating ratio R24 to charge from the grid 3. Both of these methods optimize the energy storage system 1 by improving the power supply efficiency and / or charging efficiency, thereby extending the service life of the energy storage unit 11 and reducing power loss.

[0065] FIG8 is a schematic diagram of another embodiment of the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a low-battery state. Operating points similar to those in FIG7A are denoted by the same reference numerals and are not further described herein. However, in this embodiment, as shown in FIG8 , when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fifth frequency boundary value f25 and less than or equal to the third frequency boundary value f23 (i.e., between operating points 2B and 2Cb), the control unit 13 sets the power regulation ratio to be less than or equal to the first lower limit corresponding to the operating frequency at the fifth frequency boundary value f25 and greater than or equal to the first lower limit corresponding to the operating frequency at the third frequency boundary value f23. Furthermore, the control unit 13 sets the power regulation ratio to increase or remain constant as the operating frequency decreases (in FIG8 , the power regulation ratio is set to increase as the operating frequency decreases as an example). In the section between operating point 2B and operating point 2Cb, if the control unit 13 sets the power regulation adjustment ratio to remain constant as the operating frequency decreases, the energy storage system 1 can discharge more efficiently and to a lower limit to provide the power regulation function of the power grid 3, while taking into account both power regulation and the discharge capacity of the energy storage system 1, thereby minimizing damage to the energy storage unit 11 due to low power. If the control unit 13 sets the power regulation adjustment ratio to increase as the operating frequency decreases, the efficiency of the energy storage system 1 can be improved.

[0066] FIG9A is a schematic diagram illustrating an embodiment of the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a high-charge state. The curve in FIG9A is formed by connecting a plurality of discrete operating points, each of which represents the regulation ratio corresponding to an operating frequency. When the energy storage unit 11 is in a high-charge state, as shown in FIG9A , when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the first frequency boundary value f31 and less than or equal to the second frequency boundary value f32 (i.e., between operating points 3D and 3E, for example, the first frequency boundary value f31 can be set to the preset power supply frequency f0, set to be greater than the preset power supply frequency f0, or set to the second frequency boundary value f32), the control unit 13 sets the power regulation ratio to a first operating ratio R31, where the first operating ratio R31 is less than or equal to 0 and greater than or equal to the first input boundary value IL1. Furthermore, the control unit 13 sets the second frequency boundary value f32 to be greater than the second frequency fr2, and sets the first frequency boundary value f31 to be greater than the first frequency fr1 and less than the second frequency fr2. In some embodiments, the control unit 13 sets the first operating ratio R31 to zero, meaning that the energy storage system 1 neither supplies power to the grid 3 nor receives power from the grid 3. In other embodiments, the energy storage system 1 includes an auxiliary power supply device 14 (as shown in FIG1 ). Therefore, the control unit 13 sets the first operating ratio R31 to less than zero, so that the input power received by the energy storage system 1 from the grid 3 is greater than or equal to the auxiliary power required by the auxiliary power supply device 14. In this case, the auxiliary power supply device 14 is effectively powered directly by the grid 3. In frequency ranges where power regulation is not required, by setting the first operating ratio R31 to less than zero, the grid 3 is used to directly power the auxiliary power supply device 14. This not only reduces the burden on the grid 3 but also avoids energy loss by first storing power in the energy storage unit 11 before supplying it to the auxiliary power supply device 14. This also prevents unnecessary charging and discharging, thereby extending the service life of the energy storage unit 11.

[0067] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the third frequency boundary f33 (i.e., between the operating points 3A and 3C), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the second output boundary OL2 and greater than or equal to the second operating ratio R32, where the third frequency boundary f33 is greater than the third frequency fr3 and less than the first frequency boundary f31. The second operating ratio R32 is greater than the first operating ratio R31, and the efficiency of the energy storage system 1 supplying power to the power grid 3 at the second operating ratio R32 is greater than the efficiency of the energy storage system 1 supplying power to the power grid 3 at the first operating ratio R31, which is greater than a fifth efficiency threshold TH5. As shown in FIG9A , when the operating frequency of the power grid 3 decreases from the first frequency boundary f31 to the third frequency boundary f33, the power regulation adjustment ratio correspondingly jumps from the first operating ratio R31 to the second operating ratio R32. In this embodiment, the second operating ratio R32 is substantially equal to the first output boundary OL1.

[0068] In some embodiments, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the first frequency fr1 and less than or equal to the third frequency boundary value f33 (i.e., between the operating point 3B and the operating point 3C), the control unit 13 sets the power regulation adjustment ratio to be substantially equal to the first output boundary value OL1. Furthermore, the control unit 13 sets the third frequency boundary value f33 to be greater than the first frequency fr1 and less than the first frequency boundary value f31. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the third frequency fr3 and less than or equal to the first frequency fr1, the control unit 13 sets the power regulation adjustment ratio to increase as the operating frequency decreases. For example, the power regulation adjustment ratio is set to be substantially equal to the first upper limit value corresponding to the operating frequency.

[0069] When the operating frequency of the power grid 3 measured by the measurement unit 12 is less than or equal to the third frequency fr3, in this embodiment, the power company does not provide the energy storage system 1 with any adjustment space (see FIG. 3 ). Therefore, the relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3 is the same as shown in FIG. 3 .

[0070] Furthermore, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency boundary value f34 and less than or equal to the fourth frequency fr4 (i.e., between the operating points 3Fa and 3H), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the third operating ratio R33 and greater than or equal to the second input boundary value IL2, wherein the fourth frequency boundary value f34 is greater than the second frequency boundary value f32 and less than the fourth frequency fr4. The third operating ratio R33 is less than the first operating ratio R31, and the efficiency of the energy storage unit 11 charging from the power grid 3 at the third operating ratio R33 is greater than the efficiency of the energy storage unit 11 charging from the power grid 3 at the first operating ratio R31 by a sixth efficiency threshold TH6. As shown in FIG. 9A , when the operating frequency of the power grid 3 increases from the second frequency boundary value f32 to the fourth frequency boundary value f34, the power regulation adjustment ratio is correspondingly reduced from the first operating ratio R31 to the third operating ratio R33.

[0071] In some embodiments, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency boundary value f34 and less than or equal to the fifth frequency boundary value f35 (i.e., between the operating points 3Fa and 3Fb), the control unit 13 sets the power regulation ratio to remain constant as the operating frequency increases. Furthermore, the control unit 13 sets the fifth frequency boundary value f35 to be greater than the fourth frequency boundary value f34 and less than the fourth frequency fr4. By maintaining the regulation ratio constant as the operating frequency increases between the operating points 3Fa and 3Fb, the energy storage system 1 can receive power from the power grid 3 more efficiently and with lower limits, providing power regulation for the power grid 3. This balances power regulation with the charge level of the energy storage system 1, minimizing the amount of charge in the energy storage unit 11.

[0072] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fifth frequency boundary value f35 and less than or equal to the sixth frequency boundary value f36 (i.e., between operating points 3Fb and 3G), the control unit 13 sets the power regulation adjustment ratio to be less than or equal to the second upper limit value corresponding to the operating frequency at the fifth frequency boundary value f35 and greater than or equal to the second upper limit value corresponding to the operating frequency at the sixth frequency boundary value f36. Furthermore, the control unit 13 sets the power regulation adjustment ratio to decrease as the operating frequency increases. Furthermore, the control unit 13 sets the sixth frequency boundary value f36 to be greater than the fifth frequency boundary value f35 and less than the fourth frequency fr4. When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the sixth frequency boundary value f36 and less than or equal to the fourth frequency fr4 (i.e., between operating points 3G and 3H), the control unit 13 sets the power regulation adjustment ratio to decrease as the operating frequency increases, for example, setting the power regulation adjustment ratio to be substantially equal to the second upper limit value corresponding to the operating frequency.

[0073] When the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency fr4, in this embodiment, the power company does not provide the energy storage system 1 with any adjustment space (see FIG. 3 ). Therefore, the relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3 is the same as shown in FIG. 3 .

[0074] Figure 9B is a schematic diagram of an embodiment of the efficiency of the energy storage system 1 and the adjustment ratio of the power it provides when the energy storage unit 11 is in a high-charge state. The right curve in Figure 9B represents the power supply efficiency curve when the energy storage system 1 supplies power to the grid 3, while the left curve in Figure 9B represents the charging efficiency curve when the energy storage system 1 charges the energy storage unit 11 from the grid 3. The power supply efficiency curve and charging efficiency curve in Figure 9B are not necessarily linear or symmetrical. If the energy storage system 1 selects a poor adjustment ratio, the efficiency of the energy storage system 1 will be poor, and may even cause wear and tear on the energy storage system 1, reducing its charging and discharging performance and service life. When the energy storage system 1 supplies power to the grid 3, since the energy storage unit 11 is already in a high-charge state, the energy storage system 1 selects the adjustment ratio with a priority on reducing the charge of the energy storage unit 11. For example, when the operating frequency of the grid 3 is between the third frequency limit f33 and the first frequency fr1, the energy storage system 1 supplies power to the grid 3 at a value substantially corresponding to the upper limit of these adjustment ratios (i.e., the first output limit OL1). When the operating frequency of the power grid 3 is between the first frequency fr1 and the third frequency fr3, the energy storage system 1 supplies power to the power grid 3 at a first upper limit value of the regulation ratio substantially corresponding to the operating frequency.

[0075] When the energy storage unit 11 is charging from the grid 3, when the operating frequency of the grid 3 is at the second frequency limit f32, the energy storage system 1 can choose to charge the energy storage unit 11 from the grid 3 at the adjustment ratio of the first input limit IL1. However, as shown in FIG9B , when the energy storage unit 11 is charged from the grid 3 at the adjustment ratio of the first input limit IL1, the efficiency of the energy storage system 1 is still poor. Therefore, in this embodiment, the energy storage system 1 waits until the operating frequency of the grid 3 rises to the fourth frequency limit f34 before charging the energy storage unit 11 from the grid 3 at the adjustment ratio of the third operating ratio R33. As shown in FIG9B , compared to the adjustment ratio of the first input limit IL1, the energy storage system 1 operating efficiency corresponding to the third operating ratio R33 is higher, and the energy storage unit 11 can be charged from the grid 3 more efficiently. Referring to Figures 3, 9A, and 9B, in one embodiment, when the energy storage unit 11 is in a high-charge state, as the operating frequency of the power grid 3 increases from the fourth frequency boundary value f34 to the fourth frequency fr4, the efficiency of the second upper limit of the adjustment ratio corresponding to the operating frequency may decrease in some sections as the operating frequency increases (as shown in the curve corresponding to the section of the adjustment ratio between the third operating ratio R33, the fourth operating ratio R34, and the second input boundary value IL2 in Figure 9B). Therefore, the energy storage system 1 needs to balance efficiency and the energy storage unit 11's charge capacity to select an appropriate adjustment ratio to supply power to the power grid 3. For example, when the operating frequency of the power grid 3 is between the fourth frequency boundary value f34 and the fifth frequency boundary value f35, the energy storage system 1 uses a fixed adjustment ratio of the third operating ratio R33 to charge the energy storage unit 11 from the power grid 3. This allows the energy storage system 1 to receive power from the power grid 3 more efficiently and at a lower limit, thereby providing power regulation for the power grid 3. This balances power regulation with the charge capacity of the energy storage system 1, minimizing the energy storage unit 11's charge capacity. When the operating frequency of the power grid 3 is between the fifth frequency boundary f35 and the sixth frequency boundary f36, the regulation ratio used by the energy storage system 1 decreases as the operating frequency of the power grid 3 increases, resulting in a gradual increase in the efficiency of the energy storage system 1. The corresponding efficiency curve in FIG9B is the rising curve corresponding to the regulation ratio between the third operating ratio R33 and the fourth operating ratio R34. The efficiency value corresponding to the regulation ratio of the fourth operating ratio R34 is substantially optimal. When the regulation ratio is less than the fourth operating ratio R34, the corresponding efficiency value begins to decrease. When the operating frequency of the power grid 3 is between the sixth frequency boundary f36 and the fourth frequency fr4, since the regulation ratio of the energy storage system 1 must be less than or equal to the second upper limit of the regulation ratio, the energy storage unit 11 charges from the power grid 3 at a value substantially corresponding to the second upper limit of these regulation ratios. The corresponding efficiency curve in FIG9B is the curve corresponding to the regulation ratio between the fourth operating ratio R34 and the second input boundary IL2.

[0076] In one embodiment, the fourth frequency boundary value f34 is selected based on the difference between the efficiency of the energy storage system 1 at the third operating ratio R33 and the efficiency at the first operating ratio R31 being greater than a sixth efficiency threshold TH6. Specifically, the fourth frequency boundary value f34 corresponding to the third operating ratio R33 is selected only if the difference between the efficiency of the energy storage system 1 at the third operating ratio R33 and the efficiency at the first operating ratio R31 is greater than the sixth efficiency threshold TH6. In another embodiment, when the operating frequency of the power grid 3 is between the second critical frequency fy and the predetermined power supply frequency f0 (see FIG. 3 ), the power provided by the energy storage system 1 is regulated at the first operating ratio R31. When the operating frequency of the power grid 3 rises to the second critical frequency fy, the energy storage system 1 must supply power to the power grid 3 at a regulation ratio less than or equal to zero. At this point, the energy storage system 1 selects the regulation ratio corresponding to the highest efficiency within the allowable regulation ratio range as the third operating ratio R33, allowing the energy storage unit 11 to charge from the power grid 3.

[0077] Due to the high state of charge of the energy storage unit 11, the third frequency limit f33 can also be set as close as possible to the second frequency limit f32 to discharge the energy storage unit 11 as quickly as possible. In another embodiment, to minimize the charge of the energy storage unit 11, when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the first frequency limit f31 and less than or equal to the second frequency fr2, the control unit 13 sets the power regulation ratio equal to the second operating ratio R32 or the first output limit OL1.

[0078] In another embodiment, similar to the embodiment of FIG4C , due to performance limitations of energy storage system 1, to protect the service life of energy storage unit 11, or other design considerations, the efficiency values ​​corresponding to the second operating ratio R32 and / or the second output limit OL2 in the power supply efficiency curve may not reach the optimal value; and / or the efficiency values ​​corresponding to the third operating ratio R33, the fourth operating ratio R34, and / or the second input limit IL2 in the charging efficiency curve may not reach the optimal value. However, energy storage system 1 can wait until the operating frequency of grid 3 drops to the third frequency limit f33 before increasing from the first operating ratio R31 to the second operating ratio R32 to supply power to grid 3, or wait until the operating frequency of grid 3 rises to the fourth frequency limit f34 before decreasing from the first operating ratio R31 to the third operating ratio R33 to charge from grid 3. Both of these improvements in power supply efficiency and / or charging efficiency optimize the energy storage system 1, thereby extending the service life of energy storage unit 11 and reducing power loss.

[0079] FIG10 is a schematic diagram illustrating another embodiment of the power regulation ratio provided by the energy storage system 1 in response to the operating frequency of the power grid 3 when the energy storage unit 11 is in a high charge state. Operating points similar to those in FIG9A are denoted by the same reference numerals and are not further described herein. However, in this embodiment, as shown in FIG10 , when the operating frequency of the power grid 3 measured by the measurement unit 12 is greater than or equal to the fourth frequency boundary value f34 and less than or equal to the sixth frequency boundary value f36 (i.e., between operating points 3Fa and 3G), the control unit 13 sets the power regulation ratio to be less than or equal to the second upper limit corresponding to the operating frequency at the fourth frequency boundary value f34 and greater than or equal to the second upper limit corresponding to the operating frequency at the sixth frequency boundary value f36. Furthermore, the control unit 13 sets the power regulation ratio to remain constant or decrease as the operating frequency increases ( FIG10 illustrates a decrease as the operating frequency increases as an example). In the section between operating point 3Fa and operating point 3G, if the control unit 13 sets the power regulation adjustment ratio to remain constant as the operating frequency increases, the energy storage system 1 can receive power from the power grid 3 more efficiently and to a lower limit, thereby providing the power regulation function of the power grid 3. At the same time, it takes into account both power regulation and the charging capacity of the energy storage system 1, thereby minimizing the amount of charge in the energy storage unit 11 from being too high. If the control unit 13 sets the power regulation adjustment ratio to decrease as the operating frequency increases, the efficiency of the energy storage system 1 can be improved.

[0080] In summary, this case provides an energy storage system and an operating method thereof, which sets the adjustment ratio of the power regulation of the energy storage system according to the charge state of the energy storage unit in the energy storage system, the operating frequency of the power grid and the efficiency of the energy storage system, so that the energy storage unit supplies power to the power grid or charges itself from the power grid at the adjustment ratio of the agreed capacity, thereby making the energy storage system operate at a higher efficiency state.

[0081] It should be noted that the above description is merely a preferred embodiment of the present invention and is not limited to the described embodiment. The scope of the present invention is determined by the scope of the attached patent application. Furthermore, the present invention is subject to various modifications by those skilled in the art, provided that they do not deviate from the intended scope of the attached patent application.

[0082] 1: Energy storage system 2: Grid connection point 3: Power grid 11: Energy storage unit 11_1, 11_2, 11_n: Energy storage device 12: Measuring unit 13: Control unit 14: Auxiliary power supply device 111:Battery module 112: Power Regulator 113: Transformer fr1: first frequency fr2: second frequency fr3: third frequency fr4: fourth frequency fr5: fifth frequency fr6: sixth frequency IL1: First input boundary value IL2: Second input boundary value IL3: Third input boundary value OL1: First output boundary value OL2: Second output boundary value OL3: The third output boundary value f11, f21, f31: first frequency boundary value f12, f22, f32: second frequency boundary value f13, f23, f33: third frequency boundary value f14, f14a, f24, f34: fourth frequency boundary value f15, f25, f35: fifth frequency boundary value f16, f26, f36: sixth frequency boundary value f17, f17a: seventh frequency boundary value f18: eighth frequency boundary value R11, R21, R31: first operating ratio R12, R22, R32: Second operating ratio R13, R23, R33: The third operating ratio R14, R24, R34: Fourth operating ratio R15: The fifth operating ratio 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1Ba, 1Ia: Working point 2A, 2B, 2Ca, 2Cb, 2D, 2E, 2F, 2G, 2H: operating points 3A, 3B, 3C, 3D, 3E, 3Fa, 3Fb, 3G, 3H: working points f0: preset power supply frequency fx: first critical frequency fy: second critical frequency TH1: First efficiency threshold TH2: Second efficiency threshold TH3: Third efficiency threshold TH4: Fourth efficiency threshold TH5: Fifth efficiency threshold TH6: Sixth efficiency threshold

Claims

1. An energy storage system for coupling to a power grid to provide power regulation to the power grid with a maximum value of a predetermined capacity, wherein when an operating frequency of the power grid is greater than or equal to a first frequency and less than or equal to a second frequency, a regulation ratio of the power regulation of the energy storage system is greater than or equal to a first input boundary value and less than or equal to a first output boundary value; when the operating frequency of the power grid is greater than or equal to a third frequency and less than or equal to the first frequency, the regulation ratio of the power regulation of the energy storage system is greater than or equal to the first input boundary value and less than or equal to a second output boundary value; when the operating frequency decreases from the first frequency to the third frequency, a plurality of first upper limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first output boundary value to the second output boundary value, and a plurality of first lower limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first input boundary value to the second output boundary value; When the operating frequency of the power grid is greater than or equal to the second frequency and less than or equal to a fourth frequency, the regulation ratio of the power regulation of the energy storage system is greater than or equal to a second input boundary value and less than or equal to the first output boundary value; when the operating frequency increases from the second frequency to the fourth frequency, a plurality of second upper limits corresponding to the change in operating frequency decrease from the first output boundary value to the second input boundary value, and a plurality of second lower limits corresponding to the change in operating frequency decrease from the first input boundary value to the second input boundary value; the energy storage system includes: an energy storage unit for storing and providing electrical energy; a measurement unit for measuring the operating frequency of the power grid; and a control unit coupled to the measurement unit and the energy storage unit for receiving the operating frequency of the power grid measured by the measurement unit; wherein... When the state of charge (SBC) of the energy storage unit is greater than a first charge level, the energy storage unit is in a normal charge state; when the SBC of the energy storage unit is less than the first charge level, the energy storage unit is in a low charge state; when the control unit sets the regulation ratio of the power regulation of the energy storage system to be greater than 0, the control unit sets the energy storage unit to supply power to the grid at the regulation ratio of the agreed capacity; when the control unit sets the regulation ratio of the power regulation of the energy storage system to be less than 0, the control unit sets the energy storage unit to charge itself from the grid at the regulation ratio of the agreed capacity; when the operating frequency of the grid measured by the measurement unit is greater than or equal to a first frequency boundary value and less than or equal to a second frequency boundary value, the control unit sets the regulation ratio of the power regulation to a first operating ratio, the first operating ratio being less than or equal to 0 and greater than or equal to the first input boundary value; the first frequency boundary value is less than the first frequency and / or the second frequency boundary value is greater than the second frequency; When the operating frequency of the power grid measured by the measurement unit is greater than or equal to a third frequency boundary value and less than or equal to the fourth frequency, the control unit sets the adjustment ratio of the power regulation to be less than or equal to a second operating ratio and greater than or equal to the second input boundary value; the third frequency boundary value is greater than the second frequency boundary value; the second operating ratio is less than the first operating ratio, and a second efficiency value for charging the energy storage unit from the power grid at the second operating ratio is greater than a first efficiency threshold than a first efficiency value for charging the energy storage unit from the power grid at the first operating ratio.

2. The energy storage system as claimed in claim 1, wherein when the energy storage unit is in the normal power state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, the control unit sets the power regulation ratio to be substantially equal to the second lower limit value corresponding to the operating frequency; the fourth frequency boundary value is less than the fourth frequency.

3. The energy storage system as claimed in claim 2, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to a fifth frequency boundary value, the control unit sets the adjustment ratio of the power regulation to be less than or equal to the second lower limit value corresponding to the fourth frequency boundary value and greater than the second lower limit value corresponding to the fifth frequency boundary value, and the control unit sets the adjustment ratio of the power regulation to decrease or remain fixed as the operating frequency increases; the fifth frequency boundary value is less than the fourth frequency.

4. The energy storage system as claimed in claim 3, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fifth frequency boundary value and less than or equal to the fourth frequency, the control unit sets the regulation ratio of the power regulation to decrease as the operating frequency increases.

5. The energy storage system as claimed in claim 4, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fifth frequency boundary value and less than or equal to the fourth frequency, the control unit sets the regulation ratio of the power regulation to be substantially equal to the second upper limit value corresponding to the operating frequency.

6. The energy storage system as claimed in claim 1, wherein when the energy storage unit is in the normal power state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, the control unit sets the power regulation adjustment ratio to be less than or equal to the second lower limit value corresponding to the third frequency boundary value and greater than the second lower limit value corresponding to the fourth frequency boundary value, and the control unit sets the power regulation adjustment ratio to decrease or remain fixed as the operating frequency increases; the fourth frequency boundary value is less than the fourth frequency.

7. The energy storage system as claimed in claim 6, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to the fourth frequency, the control unit sets the regulation ratio of the power regulation to be substantially equal to the second upper limit value corresponding to the operating frequency.

8. The energy storage system as claimed in claim 1, wherein when the state of charge of the energy storage unit is greater than a second charge, the energy storage unit is in a high charge state, wherein the second charge is greater than the first charge; when the energy storage unit is in the high charge state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, the control unit sets the regulation ratio of the power regulation to remain fixed as the operating frequency increases; the fourth frequency boundary value is less than the fourth frequency.

9. The energy storage system as claimed in claim 8, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to a fifth frequency boundary value, the control unit sets the adjustment ratio of the power regulation to be less than or equal to the second upper limit value corresponding to the fourth frequency boundary value and greater than or equal to the second upper limit value corresponding to the fifth frequency boundary value, and the control unit sets the adjustment ratio of the power regulation to decrease as the operating frequency increases; the fifth frequency boundary value is less than the fourth frequency.

10. The energy storage system of claim 9, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fifth frequency boundary value and less than or equal to the fourth frequency, the control unit sets the regulation ratio of the power regulation to be equal to the second upper limit value corresponding to the operating frequency.

11. The energy storage system as claimed in claim 1, wherein when the state of charge of the energy storage unit is greater than a second charge, the energy storage unit is in a high charge state, wherein the second charge is greater than the first charge; when the energy storage unit is in the high charge state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, the control unit sets the adjustment ratio of the power regulation to be less than or equal to the second upper limit value corresponding to the third frequency boundary value and greater than or equal to the second upper limit value corresponding to the fourth frequency boundary value, and the control unit sets the adjustment ratio of the power regulation to decrease or remain fixed as the operating frequency increases; the fourth frequency boundary value is less than the fourth frequency.

12. The energy storage system as claimed in claim 11, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to the fourth frequency, the control unit sets the regulation ratio of the power regulation to be equal to the second upper limit value corresponding to the operating frequency.

13. The energy storage system of claim 1, wherein when the energy storage unit is in the low power state and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to the second frequency, the control unit sets the regulation ratio of the power regulation to be substantially equal to the first input boundary value; the third frequency boundary value is greater than the first frequency and less than the second frequency.

14. The energy storage system as claimed in claim 13, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the second frequency and less than or equal to the fourth frequency, the control unit sets the regulation ratio of the power regulation to be substantially equal to the second lower limit value corresponding to the operating frequency.

15. The energy storage system as claimed in claim 1, wherein when the energy storage unit is in the normal power state, the first frequency boundary value is less than the first frequency and the second frequency boundary value is greater than the second frequency.

16. The energy storage system as claimed in claim 1, wherein when the energy storage unit is in the low-power state, the first frequency boundary value is less than the first frequency.

17. The energy storage system of claim 1, wherein when the state of charge of the energy storage unit is greater than a second charge, the energy storage unit is in a high charge state, wherein the second charge is greater than the first charge; and when the energy storage unit is in the high charge state, the second frequency boundary value is greater than the second frequency.

18. The energy storage system of claim 1, further comprising an auxiliary power supply device, wherein the control unit sets the first operating ratio to be less than 0, such that an input electrical energy received by the energy storage system from the grid is greater than or equal to an auxiliary electrical energy provided by the auxiliary power supply device.

19. The energy storage system of claim 1, wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency and less than or equal to a fourth frequency boundary value, the control unit sets the regulation ratio of the power regulation to be less than or equal to the second output boundary value and greater than or equal to a third operating ratio; the fourth frequency boundary value is less than the first frequency boundary value; the third operating ratio is greater than the first operating ratio, and a third efficiency value of the energy storage system supplying power to the power grid at the third operating ratio is greater than a fourth efficiency value of the energy storage system supplying power to the power grid at the first operating ratio by a second efficiency threshold.

20. A method of operating an energy storage system, wherein the energy storage system is coupled to a power grid to provide the power grid with a power regulation of a maximum value of a predetermined capacity; when an operating frequency of the power grid is greater than or equal to a first frequency and less than or equal to a second frequency, a regulation ratio of the power regulation of the energy storage system is greater than or equal to a first input boundary value and less than or equal to a first output boundary value; when the operating frequency of the power grid is greater than or equal to a third frequency and less than or equal to the first frequency, the regulation ratio of the power regulation of the energy storage system is greater than or equal to the first input boundary value and less than or equal to a second output boundary value; when the operating frequency decreases from the first frequency to the third frequency, a plurality of first upper limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first output boundary value to the second output boundary value, and a plurality of first lower limits of the regulation ratio corresponding to the change in operating frequency correspondingly increase from the first input boundary value to the second output boundary value; When the operating frequency of the power grid is greater than or equal to the second frequency and less than or equal to a fourth frequency, the regulation ratio of the power regulation of the energy storage system is greater than or equal to a second input boundary value and less than or equal to the first output boundary value; when the operating frequency increases from the second frequency to the fourth frequency, the plurality of second upper limits of the regulation ratio corresponding to the change in operating frequency decrease from the first output boundary value to the second input boundary value, and the plurality of second lower limits of the regulation ratio corresponding to the change in operating frequency decrease from the first input boundary value to the second input boundary value. The energy storage system includes an energy storage unit, a measurement unit, and a control unit. The energy storage unit stores and provides electrical energy. The measurement unit measures the operating frequency of the power grid. The control unit is coupled to the measurement unit and the energy storage unit and receives the operating frequency of the power grid measured by the measurement unit. When the state of charge (SBC) of the energy storage unit is greater than a first charge level, the energy storage unit is in a normal charge state. When the SBC of the energy storage unit is less than the first charge level, the energy storage unit is in a low charge state. When the control unit sets the power regulation ratio of the energy storage system to be greater than 0, the control unit sets the energy storage unit to supply power to the power grid at the predetermined capacity regulation ratio. When the control unit sets the power regulation ratio of the energy storage system to be less than 0, the control unit sets the energy storage unit to charge itself from the power grid at the predetermined capacity regulation ratio. The operation method includes: When the operating frequency of the power grid measured by the measurement unit is greater than or equal to a first frequency boundary value and less than or equal to a second frequency boundary value, the control unit sets the adjustment ratio of the power regulation to a first operating ratio, wherein the first operating ratio is less than or equal to 0 and greater than or equal to the first input boundary value, the first frequency boundary value is less than the first frequency and / or the second frequency boundary value is greater than the second frequency.And when the operating frequency of the power grid measured by the measurement unit is greater than or equal to a third frequency boundary value and less than or equal to the fourth frequency, the control unit sets the adjustment ratio of the power regulation to be less than or equal to a second operating ratio and greater than or equal to the second input boundary value, wherein the third frequency boundary value is greater than the second frequency boundary value, the second operating ratio is less than the first operating ratio, and a second efficiency value for charging the energy storage unit from the power grid at the second operating ratio is greater than a first efficiency threshold than a first efficiency value for charging the energy storage unit from the power grid at the first operating ratio.

21. The operation method as described in claim 20 further comprises: when the energy storage unit is in the normal power state, and the operating frequency of the power grid measured by the measurement unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation substantially equal to the second lower limit value corresponding to the operating frequency, wherein the fourth frequency boundary value is less than the fourth frequency.

22. The operating method as described in claim 21 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to a fifth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation to be less than or equal to the second lower limit value corresponding to the fourth frequency boundary value and greater than the second lower limit value corresponding to the fifth frequency boundary value, and setting the control unit to set the adjustment ratio of the power regulation to decrease or remain fixed as the operating frequency increases, wherein the fifth frequency boundary value is less than the fourth frequency.

23. The operating method as described in claim 22 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fifth frequency boundary value and less than or equal to the fourth frequency, setting the control unit to set the adjustment ratio of the power regulation to decrease as the operating frequency increases.

24. The operating method as described in claim 23 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fifth frequency boundary value and less than or equal to the fourth frequency, setting the control unit to set the adjustment ratio of the power regulation to be substantially equal to the second upper limit value corresponding to the operating frequency.

25. The operating method as described in claim 20 further comprises: when the energy storage unit is in the normal power state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation to be less than or equal to the second lower limit value corresponding to the third frequency boundary value and greater than the second lower limit value corresponding to the fourth frequency boundary value, and setting the control unit to set the adjustment ratio of the power regulation to decrease or remain fixed as the operating frequency increases, wherein the fourth frequency boundary value is less than the fourth frequency.

26. The operating method as described in claim 25 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to the fourth frequency, setting the control unit to set the adjustment ratio of the power regulation to be substantially equal to the second upper limit value corresponding to the operating frequency.

27. The operating method as claimed in claim 20, wherein when the state of charge of the energy storage unit is greater than a second charge, the energy storage unit is in a high charge state, and the second charge is greater than the first charge; the operating method further comprises: when the energy storage unit is in the high charge state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation to remain fixed as the operating frequency increases, wherein the fourth frequency boundary value is less than the fourth frequency.

28. The operating method as described in claim 27 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to a fifth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation to be less than or equal to the second upper limit value corresponding to the fourth frequency boundary value and greater than or equal to the second upper limit value corresponding to the fifth frequency boundary value, and setting the control unit to set the adjustment ratio of the power regulation to decrease as the operating frequency increases, wherein the fifth frequency boundary value is less than the fourth frequency.

29. The operating method as described in claim 28 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fifth frequency boundary value and less than or equal to the fourth frequency, setting the control unit to set the adjustment ratio of the power regulation to be equal to the second upper limit value corresponding to the operating frequency.

30. The operating method as claimed in claim 20, wherein when the state of charge of the energy storage unit is greater than a second energy level, the energy storage unit is in a high energy level state, and the second energy level is greater than the first energy level; the operating method further comprises: when the energy storage unit is in the high energy level state, and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to a fourth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation to be less than or equal to the second upper limit value corresponding to the third frequency boundary value and greater than or equal to the second upper limit value corresponding to the fourth frequency boundary value, and setting the control unit to set the adjustment ratio of the power regulation to decrease or remain fixed as the operating frequency increases, wherein the fourth frequency boundary value is less than the fourth frequency.

31. The operating method as described in claim 30 further includes: wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the fourth frequency boundary value and less than or equal to the fourth frequency, the control unit sets the adjustment ratio of the power regulation to be equal to the second upper limit value corresponding to the operating frequency.

32. The operating method as described in claim 20 further comprises: when the energy storage unit is in the low power state and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency boundary value and less than or equal to the second frequency, setting the control unit to set the adjustment ratio of the power regulation to be substantially equal to the first input boundary value, wherein the third frequency boundary value is greater than the first frequency and less than the second frequency.

33. The operating method as described in claim 32 further comprises: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the second frequency and less than or equal to the fourth frequency, setting the control unit to set the adjustment ratio of the power regulation to be substantially equal to the second lower limit value corresponding to the operating frequency.

34. The method of operation as described in claim 20, wherein when the energy storage unit is in the normal power state, the first frequency boundary value is less than the first frequency and the second frequency boundary value is greater than the second frequency.

35. The method of operation as described in claim 20, wherein when the energy storage unit is in the low-power state, the first frequency boundary value is less than the first frequency.

36. The method of operation as described in claim 20, wherein when the state of charge of the energy storage unit is greater than a second charge, the energy storage unit is in a high charge state, wherein the second charge is greater than the first charge; and when the energy storage unit is in the high charge state, the second frequency boundary value is greater than the second frequency.

37. The method of operation as claimed in claim 20, wherein the energy storage system further includes an auxiliary power supply device, the method of operation further comprising: setting the control unit to set the first operating ratio to less than 0, such that an input electrical energy received by the energy storage system from the power grid is greater than or equal to an auxiliary electrical energy provided by the auxiliary power supply device.

38. The operating method as described in claim 20, further comprising: when the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency and less than or equal to a fourth frequency boundary value, setting the control unit to set the adjustment ratio of the power regulation to be less than or equal to the second output boundary value and greater than or equal to a third operating ratio, wherein, The fourth frequency boundary value is less than the first frequency boundary value; the third operating ratio is greater than the first operating ratio; and a third efficiency value of the energy storage system supplying power to the grid at the third operating ratio is greater than a second efficiency threshold than a fourth efficiency value of the energy storage system supplying power to the grid at the first operating ratio.

Images