Energy storage system and operation method therefor

Abstract

Provided in the present solution are an energy storage system and an operation method therefor. The energy storage system is configured to be coupled to a power grid so as to provide the power grid with power regulation of which the maximum value is an agreed capacity. The energy storage system comprises an energy storage unit, a measurement unit and a control unit. The measurement unit is used for measuring the operation frequency of the power grid. The control unit is coupled to the measurement unit and the energy storage unit and is used for receiving the operation frequency of the power grid that is measured by the measurement unit. When the operation frequency of the power grid that is measured by the measurement unit is greater than or equal to a first frequency boundary value and smaller than or equal to a second frequency boundary value, the control unit sets the regulation ratio of the power regulation to a first operation ratio, the first operation ratio being smaller than or equal to 0 and greater than or equal to a first input boundary value, the first frequency boundary value being smaller than a first frequency and / or the second frequency boundary value being greater than a second frequency.

Description

Energy storage system and operation method thereof Technical Field

[0001] This case involves an energy storage system and its operating method, particularly an energy storage system and its operating method that can improve efficiency. Background 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 continuously increasing their share of power supply. However, the volatile nature of renewable energy also poses many management challenges to traditional power grids. Energy storage systems, which can increase reliability, resilience, and flexibility, are increasingly being used in power grids. Energy storage systems can include battery systems (e.g., energy conversion devices such as fuel cells and lithium batteries) and energy management systems, providing functions such as voltage regulation and frequency regulation.

[0003] To address the instability of renewable energy and changes in the power system's generation structure and electricity demand, power companies have developed a series of ancillary service products and formulated corresponding electricity market rules to enhance grid stability and resilience, such as frequency regulation services, voltage regulation services, 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 may result in poor system performance. Furthermore, during operation, the energy storage system may operate in an inefficient state or suffer excessive wear and tear, shortening its service life, due to factors such as the energy storage system configuration, power topology, the energy storage environment (such as temperature and humidity), and the grid situation. Therefore, how to comprehensively integrate energy storage systems and operate them at the optimal operating point so that they can effectively utilize the site structure, improve or regulate the energy storage efficiency curve, and extend battery life is an urgent need.

[0004] Summary of the Invention

[0005] The purpose of this case is to provide an energy storage system and an operating method thereof to solve the aforementioned technical problems.

[0006] To achieve the above objectives, the present invention provides an energy storage system for coupling 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 the first frequency and less than or equal to the second 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 the first output boundary value. When the operating frequency of the power grid is greater than or equal to the 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 the second output boundary value. When the operating frequency decreases from the first frequency to the third frequency, the multiple 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 multiple 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 the 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 multiple second upper limits of the adjustment ratio corresponding to the change in the operating frequency are correspondingly reduced from the first output boundary value to the second input boundary value, and the multiple second lower limits of the adjustment ratio corresponding to the change in the operating frequency are correspondingly reduced 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 used to couple to the measuring unit and the energy storage unit and 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 the 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 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 power grid at the adjustment ratio of the agreed capacity; when the control unit sets the adjustment 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 from the power grid at the adjustment ratio of the agreed capacity. When the operating frequency of the power grid measured by the measuring 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, the first operating ratio being 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.

[0007] 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, multiple 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 multiple 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 multiple second upper limits of the adjustment ratio corresponding to the change in the operating frequency are correspondingly reduced from the first output boundary value to the second input boundary value, and the multiple second lower limits of the adjustment ratio corresponding to the change in the operating frequency are correspondingly reduced 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 used to couple to the measuring unit and the energy storage unit and 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 the 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 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 power grid at the adjustment ratio of the agreed capacity; when the control unit sets the adjustment 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 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 measuring unit is greater than or equal to a first frequency boundary value and less than or equal to a second frequency boundary value, setting the control unit to set 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 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.

[0008] 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 achieve an optimized battery life, thereby achieving power optimization and reducing power loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG1 is a schematic diagram of the architecture of an energy storage system according to an embodiment of the present invention;

[0010] FIG2 illustrates an embodiment of the energy storage unit of FIG1 ;

[0011] FIG3 is a schematic diagram showing a reference relationship between the power regulation ratio provided by the energy storage system and the operating frequency of the power grid;

[0012] 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;

[0013] 4B 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;

[0014] 4C 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;

[0015] 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;

[0016] 5B 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;

[0017] 6A 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;

[0018] 6B 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;

[0019] 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;

[0020] 7B 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;

[0021] FIG8 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 low-power state;

[0022] 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;

[0023] 9B 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;

[0024] FIG10 is a schematic diagram illustrating 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 high power state.

[0025] Explanation of the accompanying drawings 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: third output boundary value f11, f21, f31: first frequency boundary values ​​f12, f22, f32: second frequency boundary values ​​f13, f23, f33: third frequency boundary values ​​f14, f14a, f24, f34: fourth frequency boundary values ​​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 operation ratio R12, R22, R32: second operation ratio R13, R23, R33: third operation ratio R14, R24, R34: fourth operation ratio R15: fifth operation ratio 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1Ba, 1Ia: Operating point 2A, 2B, 2Ca, 2Cb, 2D, 2E, 2F, 2G, 2H: Operating points 3A, 3B, 3C, 3D, 3E, 3Fa, 3Fb, 3G, 3H: Operating points f0: Default 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 DETAILED DESCRIPTION

[0026] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different embodiments without departing from the scope of this invention.

[0027] 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 regulation for grid 3. The maximum power regulation 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 measuring unit 12, a control unit 13, and an auxiliary power supply device 14. Energy storage unit 11, measuring 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 measuring 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, measuring 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. In addition, the above units can be implemented separately using appropriate components, or can be integrated or implemented separately using one or more components. For example, the measurement unit 12 and the control unit 13 can perform their functions in the same circuit composed of discrete components and / or integrated circuit components.

[0028] The measuring unit 12 can be an electric meter or other suitable measuring device, and can measure the electrical parameters of 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 measuring unit 12 and obtains the state of charge of the energy storage unit 11. Based on the information such as the operating frequency and / or voltage of the power grid 3 and the state of charge of the energy storage unit 11, the control unit 13 controls the energy storage unit 11 to supply power to the power grid 3 or receive power from the power grid 3 to achieve 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, communication equipment, fire protection equipment, and sensors.

[0029] In the embodiment shown in FIG1 , 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.

[0030] The energy storage device can adopt a suitable architecture to provide energy storage function. Figure 2 illustrates a possible embodiment of the energy storage device 11_n of Figure 1. In the embodiment shown in Figure 2, the energy storage device 11_n includes multiple battery modules 111, multiple power conditioners 112 and a transformer 113, wherein the multiple battery modules 111 are electrically connected to the multiple power conditioners 112, the multiple power conditioners 112 are electrically connected to the transformer 113, and the transformer 113 is electrically connected to the grid connection point 2. The battery module 111 can be implemented in the form of lithium batteries, solid-state batteries, fuel cells or thermal batteries. In some embodiments, the battery module 111 also includes a DC-DC converter (DC to DC converter) for converting the electrical energy provided by the energy storage battery into an appropriate voltage and providing it to the power conditioner 112, or converting the electrical energy received from the power conditioner 112 into an appropriate voltage and storing it in the battery module 111 to ensure voltage stability. The power conditioner 112 is used to perform bidirectional power conversion, and a bidirectional DC / AC converter can be used, for example. The transformer 113 is used to transmit and adjust the voltage of alternating current, and can be set to have an isolation function or a non-isolated architecture. In the embodiment shown in Figure 2, the transformer 113 can be a multi-winding transformer, which has multiple windings on the side connected to the multiple 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 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 point 2, and the power conditioner 112 provides power to the grid 3 or receives power from the grid 3 directly through the grid point 2 without passing through the transformer.

[0031] Different regions or different power companies may have different regulations for grid ancillary services. Please refer to the embodiment of Figure 3, which is a schematic diagram showing the reference relationship between the power regulation ratio provided by the energy storage system 1 and the operating frequency of the power grid 3. It shows the upper and lower limits of the power regulation ratio provided by the energy storage system 1 corresponding to different operating frequencies of the power grid 3. The power regulation ratio provided by the energy storage system 1 is controlled by its control unit 13, where the maximum power regulation value is an agreed capacity (for example, a power regulation capacity of 10MW agreed with the power company). When the control unit 13 sets the adjustment ratio of the power regulation 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 power grid 3 at the adjustment ratio of the agreed capacity; when the control unit 13 sets the adjustment ratio of the power regulation 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 power grid 3 at the absolute value of the adjustment ratio of the agreed capacity (for ease of explanation, the following paragraphs will omit the "absolute value of the adjustment ratio" when referring to the energy storage unit 11 charging from the power grid 3). In addition, it should be noted that the curve in Figure 3 is composed of multiple discrete reference points connected, where each reference point represents the upper limit and / or lower limit of the adjustment ratio corresponding to an operating frequency.

[0032] To comply with the power regulation specification in 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 boundary value IL1 and less than or equal to the first output boundary value OL1 . f0 in Figure 3 can be the default supply frequency of grid 3, for example, 50 Hz or 60 Hz.

[0033] 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 multiple 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 multiple 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.

[0034] 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 multiple 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 multiple 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.

[0035] 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 adjustment ratio of energy storage system 1 should be set to be greater than or equal to the second output boundary value OL2 and less than or equal to the third output boundary value OL3. When the operating frequency decreases from the third frequency fr3 to the fifth frequency fr5, the adjustment ratio corresponding to the change in operating frequency increases from the second output boundary value OL2 to the third output boundary value OL3. When the operating frequency of power grid 3 is less than the fifth frequency fr5, the power regulation adjustment ratio of energy storage system 1 should be set to be equal to the third output boundary value OL3.

[0036] 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 adjustment 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 adjustment 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 adjustment ratio of energy storage system 1 should be set to be equal to the third input boundary value IL3.

[0037] 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 .

[0038] 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.

[0039] The control unit 13 evaluates the state of charge of the energy storage unit 11. For example, when the state of charge of the energy storage unit 11 is greater than the first charge, the control unit 13 determines that the energy storage unit 11 is in a normal charge state; when the state of charge 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 state of charge of the energy storage unit 11 is greater than the second charge (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 charge and the second charge can be determined according to actual needs. In another embodiment, the energy storage system 1 can be configured to provide power regulation functions corresponding to one or more of the three states, for example, configured to provide power regulation corresponding to only the two states of normal charge and low charge, configured to provide power regulation corresponding to only the two states of high charge and low charge, or configured to provide power regulation corresponding to only the two states of normal charge and high charge, and provide power regulation functions using the following methods for each state of charge.

[0040] FIG4A is a schematic diagram of 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 FIG4A is formed by connecting a plurality of discrete operating points, where each operating point represents the regulation ratio corresponding to an operating frequency. When the energy storage unit 11 is in a normal power state, as shown in FIG4A , 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 point 1E and operating point 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. In addition, 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 other words, 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 does not provide power to the grid 3 or receive power from the grid 3. In other embodiments, the energy storage system 1 includes an auxiliary power supply device 14 (as shown in FIG1 ), so 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 essentially powered directly by the grid 3. In this frequency range where power regulation is not required, by setting the first operating ratio R11 to less than zero, the grid 3 is used to directly power the auxiliary power supply device 14. This not only does not burden the grid 3, but also avoids energy loss by first storing power in the energy storage unit 11 before providing it to the auxiliary power supply device 14. It also avoids unnecessary charging and discharging, thereby extending the service life of the energy storage unit 11.

[0041] 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 by a value 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.

[0042] 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 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 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 constant 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 points 1A and 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.

[0043] When the operating frequency of the power grid 3 measured by the measuring 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 remains the same as shown in FIG. 3 .

[0044] 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.

[0045] When the energy storage unit 11 is in a normal charge state, 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 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.

[0046] When the operating frequency of the power grid 3 measured by the measuring 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 remains the same as shown in FIG. 3 .

[0047] FIG4B 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 power state. The right curve in FIG4B represents the power supply efficiency curve when the energy storage system 1 supplies power to the power grid 3, while the left curve in FIG4B represents the charging efficiency curve when the energy storage system 1 charges the energy storage unit 11 from the power grid 3. The power supply efficiency curve and charging efficiency curve in FIG4B 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 charge-discharge performance and service life. For example, when the operating frequency of the power grid 3 is the first frequency boundary value f11, although the energy storage system 1 can select the adjustment ratio of the first output boundary value OL1 to supply power to the power grid 3, as shown in FIG4B, the efficiency of the energy storage system 1 is still poor when the energy storage system 1 supplies power at the adjustment ratio of the first output boundary 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 at the first output boundary value OL1, the energy storage system 1 corresponding to the second operating ratio R12 has a higher operating efficiency and can more efficiently supply power to the power grid 3. Referring to FIG3 , FIG4A , and FIG4B , 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 section of the adjustment ratio between the second operating ratio R12, the third operating ratio R13, and the second output boundary value OL2 in FIG4B ). 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 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 decrease 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 at the adjustment ratio of the third operating ratio R13.When the operating frequency of the power grid 3 is between the fifth frequency boundary value f15 and the third frequency fr3, since the regulation ratio of the energy storage system 1 must be greater than or equal to the first lower limit of the regulation ratio, the energy storage system 1 uses the first lower limit of the regulation ratio substantially corresponding to these regulation ratios to supply power to the power grid 3. The corresponding efficiency curve in FIG4B is the curve corresponding to the regulation ratio section 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 the power grid 3 is at the fifth frequency boundary value f15, the energy storage system 1 must supply power to the power grid 3 at the first lower limit of the regulation ratio substantially corresponding to the operating frequency.

[0048] 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. That is, 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 default power supply frequency f0 (see FIG3 ), the power provided by the energy storage system 1 is 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 time, 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.

[0049] 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 boundary value 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 boundary value 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 boundary value 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 boundary value 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 boundary value IL1, the energy storage system 1 operating efficiency corresponding to the fourth operating ratio R14 is higher, allowing the energy storage unit 11 to be charged from the grid 3 more efficiently. 3 , 4A , and 4B , in one embodiment, when the energy storage unit 11 is in a normal charge state, when the operating frequency of the power grid 3 increases from the sixth frequency boundary value f16 to the fourth frequency fr4 , the efficiency corresponding to the second lower limit of the adjustment ratio of 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 fourth operating ratio R14 , the fifth operating ratio R15 , and the second input boundary value IL2 in FIG4B ). Therefore, the energy storage system 1 needs to select an adjustment ratio with a better 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 FIG4B is the rising curve corresponding to the section of the adjustment ratio between the fourth operating ratio R14 and the fifth operating ratio R15 . Because the efficiency value corresponding to the regulation ratio of the fifth operating ratio R15 is substantially optimal, and the corresponding efficiency value begins to decline when the regulation 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 regulation 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, because 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 is charged from the power grid 3 using the second upper limit substantially corresponding to these regulation ratios. The corresponding efficiency curve in FIG4B is the curve corresponding to the regulation ratio between the fifth operating ratio R15 and the second input boundary value IL2. In one embodiment, the second upper limit of the regulation 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 regulation ratio substantially corresponding to the operating frequency.

[0050] 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. That is, 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 default power supply frequency f0 (see FIG. 3 ), the power provided by the energy storage system 1 is 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 time, 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.

[0051] 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 regulation provided by the energy storage unit 11 when the energy storage unit 11 is in a normal power state. Compared with the embodiment of FIG4B , in the power supply efficiency curve of the embodiment of FIG4C , the efficiency value corresponding to the third operating ratio R13 and / or the second output boundary value OL2 does not reach the optimal value; and in the charging efficiency curve, the efficiency value corresponding to the fifth operating ratio R15 and / or the second input boundary value IL2 does 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 the optimal value due to the performance limitations of the energy storage system 1, 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 boundary value f13 before jumping 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 boundary value f16 before reducing the first operating ratio R11 to the fourth operating ratio R14 to charge from the grid 3. In both cases, by improving the power supply efficiency and / or charging 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] In other embodiments, the adjustment ratio of the power regulation 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 of another embodiment of the adjustment ratio of the power regulation provided by the energy storage system 1 corresponding to the operating frequency of the power grid 3 when the energy storage unit 11 is in a normal power state, and FIG5B is a schematic diagram of another embodiment of the efficiency of the energy storage system 1 and the adjustment ratio of the power regulation provided by it when the energy storage unit 11 is in a normal power state, wherein similar working points to FIG4A are represented by the same reference numerals and are not repeated 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 has a better or optimal efficiency when supplying power to the power grid 3 at the adjustment ratio of the second output boundary 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 adjustment 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 adjustment 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 adjustment 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.

[0053] According to another embodiment of the efficiency curve of the energy storage system 1, FIG6A is a schematic diagram showing 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. FIG6B is a schematic diagram showing 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 FIG6A and FIG6B , 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 the operating point 1Ba and the operating point 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 (maintaining constant is used as an example in FIG6A ). In addition, 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 the operating point 1A and the operating point 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 FIG4C , the efficiency value corresponding to the adjustment ratio of the second operating ratio R12 and / or the second output boundary value OL2 may not have reached the optimal value due to performance limitations of the energy storage system 1, protection of 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 adjustment ratio of 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.

[0054] 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 a constant ratio 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 value 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, and thereby extends the service life of the energy storage unit 11 and reduces power loss.

[0055] FIG7A is a schematic diagram of 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, where each operating point 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 the operating point 2D and the operating point 2E, for example, the second frequency boundary value f22 can be set to the default power supply frequency f0, set to be less than the default power supply frequency f0, or set to the first frequency boundary value f21), the control unit 13 sets the power regulation ratio to the 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. In addition, 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 does not provide power to the grid 3 or receive 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 essentially powered directly by the grid 3. In frequency ranges where power regulation is not required, by setting the first operating ratio R21 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 providing it to the auxiliary power supply device 14. It also avoids unnecessary charging and discharging, thereby extending the service life of the energy storage unit 11.

[0056] 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 by 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.

[0057] 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 be discharged more efficiently and at a lower limit to provide power regulation for the power grid 3, while simultaneously balancing power regulation and the discharge capacity of the energy storage system 1, thereby minimizing damage to the energy storage unit 11 due to excessively low charge.

[0058] 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 the 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 the 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.

[0059] When the operating frequency of the power grid 3 measured by the measuring 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 remains the same as shown in FIG. 3 .

[0060] 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.

[0061] 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.

[0062] When the operating frequency of the power grid 3 measured by the measuring 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 remains the same as shown in FIG. 3 .

[0063] 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 boundary value f21, the energy storage system 1 can choose to supply power to the grid 3 at the adjustment ratio of the first output boundary value OL1. However, as shown in Figure 7B, when the energy storage system 1 supplies power at the adjustment ratio of the first output boundary 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 at 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 , FIG7A , and FIG7B , 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 corresponding to the first upper limit of the adjustment ratio for the operating frequency may decrease in some sections as the operating frequency decreases (as shown in the curve corresponding to the adjustment ratio in FIG7B for the section between the second operating ratio R22, the third operating ratio R23, and the second output boundary value OL2). 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 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 the power grid 3 is between the fifth frequency boundary value f25 and the third frequency fr3, the regulation ratio of the energy storage system 1 must be greater than or equal to the first lower limit of the regulation ratio. Therefore, the energy storage system 1 uses the first lower limit value substantially corresponding to these regulation ratios to supply power to the power grid 3. The corresponding efficiency curve in FIG. 7B is the curve corresponding to the section of the regulation ratio between the third operating ratio R23 and the second output boundary value OL2.

[0064] 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. That is, 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 default power supply frequency f0 (see FIG3 ), the power provided by the energy storage system 1 is 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 time, 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.

[0065] 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.

[0066] 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 measuring 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 adjustment 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 do 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 do 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 boundary value f23 before jumping 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 boundary value f26 before lowering from the first operating ratio R21 to the fourth operating ratio R24 to charge from the grid 3. In both cases, by improving the power supply efficiency and / or charging 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.

[0067] 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 measuring 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 point 2B and operating point 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 adjustment ratio is shown as increasing as the operating frequency decreases). 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, so as to minimize 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.

[0068] FIG9A is a schematic diagram of 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 multiple discrete operating points, where each operating point 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 default power supply frequency f0, set to be greater than the default 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. In addition, 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 does not provide power to the grid 3 or receive 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 essentially powered directly by the grid 3. In this frequency range 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 providing it to the auxiliary power supply device 14. It also avoids unnecessary charging and discharging, thereby extending the service life of the energy storage unit 11.

[0069] 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.

[0070] 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, setting the power regulation adjustment ratio to be substantially equal to the first upper limit value corresponding to the operating frequency.

[0071] When the operating frequency of the power grid 3 measured by the measuring 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 remains the same as shown in FIG. 3 .

[0072] 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.

[0073] 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 point 3Fa and the operating point 3Fb), the control unit 13 sets the power regulation adjustment 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 adjustment ratio constant as the operating frequency increases between the operating points 3Fa and 3Fb, the energy storage system 1 can receive electrical energy from the power grid 3 more efficiently and with lower limits, thereby providing power regulation for the power grid 3. This balances power regulation with the charge level of the energy storage system 1, thereby minimizing the amount of charge in the energy storage unit 11.

[0074] 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 the 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 the 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.

[0075] When the operating frequency of the power grid 3 measured by the measuring 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 remains the same as shown in FIG. 3 .

[0076] 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 boundary value 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 boundary value 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.

[0077] When the energy storage unit 11 is charged 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. 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 adjustment ratio in the section between the third operating ratio R33 , the fourth operating ratio R34 , and the second input boundary value IL2 in FIG9B ). Therefore, the energy storage system 1 needs to balance efficiency and the charge of the energy storage unit 11 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 while balancing power regulation and the charge of the energy storage system 1 , thereby minimizing the charge of the energy storage unit 11. 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 at 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.

[0078] 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 default 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.

[0079] Based on the high state of charge of the energy storage unit 11, the third frequency limit value f33 may also be set as close as possible to the second frequency limit value 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 measuring unit 12 is greater than or equal to the first frequency limit value f31 and less than or equal to the second frequency fr2, the control unit 13 sets the power regulation ratio to the second operating ratio R32 or the first output limit value OL1.

[0080] In another embodiment, similar to the embodiment of FIG4C , 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, the efficiency values ​​corresponding to the second operating ratio R32 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 third operating ratio R33, the fourth operating ratio R34, 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 can wait until the operating frequency of the power grid 3 drops to the third frequency boundary value f33 before increasing the first operating ratio R31 to the second operating ratio R32 to supply power to the power grid 3, or the energy storage system 1 can wait until the operating frequency of the power grid 3 rises to the fourth frequency boundary value f34 before decreasing the first operating ratio R31 to the third operating ratio R33 to charge from the power grid 3. In both cases, by improving the power supply efficiency and / or charging efficiency, the energy storage system 1 can be optimized, thereby extending the service life of the energy storage unit 11 and reducing power loss.

[0081] FIG10 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 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 value corresponding to the operating frequency at the fourth frequency boundary value f34 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 ratio to remain constant or decrease as the operating frequency increases (in FIG10 , decreasing as the operating frequency increases is used 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 grid 3 more efficiently and to a lower limit, thereby providing the power regulation function of the grid 3, while taking into account both power regulation and the charging capacity of the energy storage system 1, so as to minimize the energy storage unit 11 from being overcharged. 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.

[0082] 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 can supply power to the power grid or charge 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.

[0083] It should be noted that the above description is merely a preferred embodiment for the purpose of illustrating the present invention. The present invention is not limited to the described embodiment. The scope of the present invention is determined by the appended claims. Furthermore, the present invention is subject to various modifications as conceived by those skilled in the art, without departing from the intended scope of the appended claims.

Claims

1. An energy storage system for coupling to a power grid to provide power conditioning to the power grid with a maximum value of an agreed capacity, When the operating frequency of the power grid is greater than or equal to a first frequency (fr1) and less than or equal to a second frequency (fr2), the power regulation ratio of the energy storage system is greater than or equal to a first input boundary value (IL1) and less than or equal to a first output boundary value (OL1); When the operating frequency of the power grid is greater than or equal to a third frequency (fr3) and less than or equal to the first frequency (fr1), the regulation ratio of the power regulation of the energy storage system is 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), a plurality of first upper limits of the regulation ratio corresponding to the change in the operating frequency correspondingly increase from the first output boundary value (OL1) to the second output boundary value (OL2), and a plurality of first lower limits of the regulation ratio corresponding to the change in the operating frequency correspondingly increase from the first input boundary value (IL1) to the second output boundary value (OL2); When the operating frequency of the power grid is greater than or equal to the second frequency (fr2) and less than or equal to a fourth frequency (fr4), the regulation ratio of the power regulation of the energy storage system is greater than or equal to a 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), a plurality of second upper limits of the regulation ratio corresponding to the change in the operating frequency correspondingly decrease from the first output boundary value (OL1) to the second input boundary value (IL2), and a plurality of second lower limits of the regulation ratio corresponding to the change in the operating frequency correspondingly decrease from the first input boundary value (IL1) to the second input boundary value (IL2); The energy storage system comprises: Energy storage unit, used to store and provide electrical energy; a measuring unit, configured to measure the operating frequency of the power grid; as well as a control unit, coupled to the measuring unit and the energy storage unit, and configured to receive the operating frequency of the power grid measured by the measuring unit; in, When the state of charge of the energy storage unit is greater than the first power level, the energy storage unit is in a normal power state; When the state of charge of the energy storage unit is less than the first power, the energy storage unit is in a low power state; When the control unit sets the adjustment ratio of the power adjustment 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 adjustment ratio of the agreed capacity; When the control unit sets the adjustment ratio of the power adjustment of the energy storage system 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 measuring unit is greater than or equal to a first frequency boundary value (f11) and less than or equal to a second frequency boundary value (f12), the control unit sets the adjustment ratio of the power adjustment to a first operating ratio (R11), wherein the first operating ratio (R11) is less than or equal to 0 and greater than or equal to the first input boundary value (IL1); The first frequency limit value (f11) is lower than the first frequency (fr1) and / or the second frequency limit value (f12) is higher than the second frequency (fr2).

2. The energy storage system according to claim 1, wherein when the energy storage unit is in the normal power state, the first frequency boundary value (f11) is less than the first frequency (fr1) and the second frequency boundary value (f12) is greater than the second frequency (fr2). 3 . The energy storage system according to claim 1 , wherein when the energy storage unit is in the low-power state, the first frequency boundary value ( f21 ) is less than the first frequency ( fr1 ).

4. The energy storage system according to 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; when the energy storage unit is in the high charge state, the second frequency boundary value (f32) is greater than the second frequency (fr2).

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

6. The energy storage system according to 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 (fr3) and less than or equal to a third frequency boundary value (f13, f23, f33), the control unit sets the adjustment ratio of the power adjustment to be less than or equal to the second output boundary value (OL2) and greater than or equal to a second operating ratio (R12, R22, R32); The third frequency boundary value (f13, f23, f33) is smaller than the first frequency boundary value (f11, f21, f31); The second operating ratio (R12, R22, R32) is greater than the first operating ratio (R11, R21, R31), and a second efficiency value of the energy storage system supplying power to the power grid at the second operating ratio (R12, R22, R32) is greater than the first efficiency value of the energy storage system supplying power to the power grid at the first operating ratio (R11, R21, R31) and is greater than an efficiency threshold.

7. The energy storage system according to 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; 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 (fr3) and less than or equal to a third frequency boundary value (f33), the control unit sets the adjustment ratio of the power adjustment to be less than or equal to the second output boundary value (OL2) and greater than or equal to a second operating ratio (R32); The third frequency boundary value (f33) is less than the first frequency boundary value (f31), and the first frequency boundary value (f31) is less than or equal to the second frequency boundary value (f32) of the default power supply frequency of the power grid; The second operating ratio (R32) is greater than the first operating ratio (R31), and a second efficiency value of the energy storage system supplying power to the power grid at the second operating ratio (R32) is greater than an efficiency threshold value of the energy storage system supplying power to the power grid at the first operating ratio (R31).

8. The energy storage system according to claim 1 , wherein when the operating frequency of the power grid measured by the measuring unit is greater than or equal to a third frequency boundary value (f16, f26, f34) and less than or equal to the fourth frequency (fr4), the control unit sets the adjustment ratio of the power adjustment to be less than or equal to a second operating ratio (R14, R24, R33) and greater than or equal to the second input boundary value (IL2); The third frequency boundary value (f16, f26, f34) is greater than the second frequency boundary value (f12, f22, f32); The second operating ratio (R14, R24, R33) is smaller than the first operating ratio (R11, R21, R31), and a second efficiency value of charging the energy storage unit from the power grid at the second operating ratio (R14, R24, R33) is greater than an efficiency threshold value than a first efficiency value of charging the energy storage unit from the power grid at the first operating ratio (R11, R21, R31).

9. The energy storage system according to claim 1 , wherein when the energy storage unit is in the low-battery state and the operating frequency of the power grid measured by the measuring unit is greater than or equal to a third frequency boundary value ( f26 ) and less than or equal to the fourth frequency ( fr4 ), the control unit sets the adjustment ratio of the power adjustment to be less than or equal to a second operating ratio ( R24 ) and greater than or equal to the second input boundary value ( IL2 ); The third frequency boundary value (f26) is greater than the second frequency boundary value (f22), and the second frequency boundary value (f22) is greater than or equal to the first frequency boundary value (f21) of the default power supply frequency of the power grid; The second operating ratio (R24) is smaller than the first operating ratio (R21), and the power grid operates at the second operating ratio. (R24) A second efficiency value of charging the energy storage unit from the grid is greater than an efficiency threshold value of a first efficiency value of charging the energy storage unit from the grid at the first operating ratio (R21).

10. A method for operating 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 value of an agreed capacity. When the operating frequency of the power grid is greater than or equal to a first frequency (fr1) and less than or equal to a second frequency (fr2), the power regulation ratio of the energy storage system is greater than or equal to a first input boundary value (IL1) and less than or equal to a first output boundary value (OL1); When the operating frequency of the power grid is greater than or equal to a third frequency (fr3) and less than or equal to the first frequency (fr1), the regulation ratio of the power regulation of the energy storage system is 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), a plurality of first upper limits of the regulation ratio corresponding to the change in the operating frequency correspondingly increase from the first output boundary value (OL1) to the second output boundary value (OL2), and a plurality of first lower limits of the regulation ratio corresponding to the change in the operating frequency correspondingly increase from the first input boundary value (IL1) to the second output boundary value (OL2); When the operating frequency of the power grid is greater than or equal to the second frequency (fr2) and less than or equal to a fourth frequency (fr4), the regulation ratio of the power regulation of the energy storage system is greater than or equal to a 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), a plurality of second upper limits of the regulation ratio corresponding to the change in the operating frequency correspondingly decrease from the first output boundary value (OL1) to the second input boundary value (IL2), and a plurality of second lower limits of the regulation ratio corresponding to the change in the operating frequency correspondingly decrease from the first input boundary value (IL1) to the second input boundary value (IL2); 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 electric energy, the measuring unit is used to measure the operating frequency of the power grid, and the control unit is used to couple to the measuring unit and the energy storage unit, and 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 power, the energy storage unit is in a normal power state; when the state of charge of the energy storage unit is less than the first power, the energy storage unit is in a low power state; when the control unit sets the adjustment 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 power grid at the adjustment ratio of the agreed capacity; when the control unit sets the adjustment 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 from the power grid at the adjustment ratio of the agreed capacity; The operation method includes: When the operating frequency of the power grid measured by the measuring unit is greater than or equal to a first frequency boundary value (f11) and less than or equal to a second frequency boundary value (f12), the control unit is configured to set the adjustment ratio of the power regulation to a first operating ratio (R11), wherein the first operating ratio (R11) is less than or equal to 0 and greater than or equal to the first input boundary value (IL1), the first frequency boundary value (f11) is less than the first frequency (fr1) and / or the second frequency boundary value (f12) is greater than the second frequency (fr2).

11. The operating method according to claim 10, wherein when the energy storage unit is in the normal power state, the first frequency boundary value (f11) is less than the first frequency (fr1) and the second frequency boundary value (f12) is greater than the second frequency (fr2). 12 . The operating method according to claim 10 , wherein when the energy storage unit is in the low-power state, the first frequency boundary value ( f21 ) is lower than the first frequency ( fr1 ).

13. The operating method according to claim 10, 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; when the energy storage unit is in the high charge state, the second frequency boundary value (f32) is greater than the second frequency (fr2).

14. The operating method according to claim 10, wherein the energy storage system further comprises an auxiliary power supply device, and the operating method further comprises: The control unit is configured to set the first operation ratio to be less than 0, so that the input power received by the energy storage system from the power grid is greater than or equal to the auxiliary power provided by the auxiliary power supply device.

15. The operating method according to claim 10, further comprising: When the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency (fr3) and less than or equal to a third frequency boundary value (f13, f23, f33), the control unit is configured to set the adjustment ratio of the power adjustment to be less than or equal to the second output boundary value (OL2) and greater than or equal to a second operating ratio (R12, R22, R32), in, The third frequency boundary value (f13, f23, f33) is smaller than the first frequency boundary value (f11, f21, f31); The second operating ratio (R12, R22, R32) is greater than the first operating ratio (R11, R21, R31), and a second efficiency value of the energy storage system supplying power to the power grid at the second operating ratio (R12, R22, R32) is greater than the first efficiency value of the energy storage system supplying power to the power grid at the first operating ratio (R11, R21, R31) and is greater than an efficiency threshold.

16. The operating method according to claim 10, 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 operating method further comprises: When the energy storage unit is in the high power state and the operating frequency of the power grid measured by the measuring unit is greater than or equal to the third frequency (fr3) and less than or equal to a third frequency boundary value (f33), the control unit is configured to set the adjustment ratio of the power adjustment to be less than or equal to the second output boundary value (OL2) and greater than or equal to a second operating ratio (R32); wherein the third frequency boundary value (f33) is less than the first frequency boundary value (f31), and the first frequency boundary value (f31) is less than or equal to the second frequency boundary value (f32) of the default power supply frequency of the power grid; The second operating ratio (R32) is greater than the first operating ratio (R31), and a second efficiency value of the energy storage system supplying power to the power grid at the second operating ratio (R32) is greater than an efficiency threshold value of the energy storage system supplying power to the power grid at the first operating ratio (R31).

17. The operating method according to claim 10, further comprising: When the operating frequency of the power grid measured by the measuring unit is greater than or equal to a third frequency boundary value (f16, f26, f34) and less than or equal to the fourth frequency (fr4), the control unit is configured to set the adjustment ratio of the power adjustment to be less than or equal to a second operating ratio (R14, R24, R33) and greater than or equal to the second input boundary value (IL2), in, The third frequency boundary value (f16, f26, f34) is greater than the second frequency boundary value (f12, f22, f32); The second operating ratio (R14, R24, R33) is smaller than the first operating ratio (R11, R21, R31), and a second efficiency value of charging the energy storage unit from the power grid at the second operating ratio (R14, R24, R33) is greater than an efficiency threshold value than a first efficiency value of charging the energy storage unit from the power grid at the first operating ratio (R11, R21, R31).

18. The operating method according to claim 10, further comprising: When the energy storage unit is in the low-battery state and the operating frequency of the power grid measured by the measuring unit is greater than or equal to a third frequency boundary value (f26) and less than or equal to the fourth frequency (fr4), the control unit is configured to set the adjustment ratio of the power adjustment to be less than or equal to a second operating ratio (R24) and greater than or equal to the second input boundary value (IL2); wherein the third frequency boundary value (f26) is greater than the second frequency boundary value (f22), and the second frequency boundary value (f22) is greater than or equal to the first frequency boundary value (f21) of the default power supply frequency of the power grid; and The second operating ratio (R24) is smaller than the first operating ratio (R21), and a second efficiency value of the grid charging the energy storage unit from the grid at the second operating ratio (R24) is greater than an efficiency threshold value than a first efficiency value of the grid charging the energy storage unit from the grid at the first operating ratio (R21).

Images