A control method and system for a energy storage system to participate in primary frequency regulation of the power grid

Abstract

The present invention relates to a control method and system for a energy storage system to participate in primary frequency regulation of a power grid. By a local controller installed on the side of the energy storage converter, the grid frequency is collected in real time, a charge-discharge power command value of the energy storage system is generated according to the collected grid frequency, and the charge-discharge power command value of the energy storage system is sent to the energy storage system. The energy storage system realizes fast active-frequency response of the energy storage system through a droop control algorithm, realizes a fast support effect of the energy storage system on the grid frequency, enables the energy storage system to better respond to system frequency changes, and prolongs the service life of the energy storage; it is applicable to parallel operation of multiple energy storage PCSs, and can be popularized and applied to energy storage power stations or new energy / storage power stations.

Description

Technical Field

[0001] The present invention relates to the technical field of primary frequency regulation control of power grids, and particularly relates to a control method and system for a energy storage system to participate in primary frequency regulation of a power grid. Background Art

[0002] In recent years, with global warming and the depletion of traditional fossil energy, in order to meet the strategic needs of energy security, countries around the world have been vigorously developing renewable energy represented by wind power. Currently, the output of new energy power generation is volatile and uncertain and does not have the inertia response characteristics of traditional power sources. After large-scale access, it will significantly increase the frequency regulation pressure of the power grid. To improve the ability of new energy power stations to participate in power grid frequency regulation, it is necessary to introduce new auxiliary frequency regulation means. Many patents and literatures have studied the participation of energy storage systems in primary frequency regulation of power grids. However, the core idea of these patents is that the upper-layer monitoring system detects a change in the power grid frequency and then sends the frequency value to each energy storage unit. The energy storage unit performs reasonable charge and discharge control according to the frequency deviation, so as to support the power grid frequency. Since the active-frequency response time is affected by the data communication time, the response speed is slow. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a control method and system for a energy storage system to participate in primary frequency regulation of a power grid. By a local controller installed on the side of the energy storage converter, the power grid frequency is collected in real time, a charge and discharge power command value of the energy storage system is generated according to the collected power grid frequency, and the charge and discharge power command value of the energy storage system is sent to the energy storage system. The energy storage system realizes the rapid active-frequency response of the energy storage system through a droop control algorithm, and realizes the rapid support of the energy storage system for the power grid frequency.

[0004] The purpose of the present invention is achieved by adopting the following technical solutions:

[0005] The present invention provides a control method for a energy storage system to participate in primary frequency regulation of a power grid, and the improvement lies in that the method includes:

[0006] Collect the power grid frequency in real time on the side of the energy storage converter;

[0007] Generate a charge and discharge power command value of the energy storage system according to the power grid frequency, and send the charge and discharge power command value of the energy storage system to the energy storage system.

[0008] Preferably, after generating a charge and discharge power command value of the energy storage system according to the power grid frequency and sending the charge and discharge power command value of the energy storage system to the energy storage system, it includes:

[0009] The control unit in the energy storage system controls the charge and discharge power of the energy storage system to the charge and discharge power command value of the energy storage system by using the droop control algorithm based on the charge and discharge power command value of the energy storage system.

[0010] Preferably, the real-time acquisition of the grid frequency on the energy storage converter side includes:

[0011] The grid frequency is real-time acquired by the local controller installed on the energy storage converter side.

[0012] Preferably, generating the charge and discharge power command value of the energy storage system according to the grid frequency and sending the charge and discharge power command value of the energy storage system to the energy storage system includes:

[0013] The local controller installed on the energy storage converter side generates the charge and discharge power command value of the energy storage system according to the grid frequency and sends the charge and discharge power command value of the energy storage system to the energy storage system.

[0014] Further, generating the charge and discharge power command value of the energy storage system according to the grid frequency includes:

[0015] If f N <f<f max and SOC≤SOC up , then the charge and discharge power command value of the energy storage system

[0016] If f N <f<f max and SOC up <SOC<SOC max , then the charge and discharge power command value of the energy storage system

[0017] If f min <f<f N and SOC≥SOC low , then the charge and discharge power command value of the energy storage system

[0018] If f min <f<f N and SOC min <SOC<SOC low , then the charge and discharge power command value of the energy storage system

[0019] If f≤f min and SOC min <SOC, then the charge and discharge power command value P cf =-P N ;

[0020] If f≥f max and SOC<SOC max , then the charge and discharge power command value P cf of the energy storage system is equal to P N ;

[0021] If |f - f N |≤f d and P current >0, SOC<SOC max , then the charge and discharge power command value P cf of the energy storage system is equal to P current ;

[0022] If |f - f N |≤f d and P current <0, SOC>SOC min , then the charge and discharge power command value P cf of the energy storage system is equal to P current ;

[0023] Otherwise, the charge and discharge power command value P cf of the energy storage system is equal to 0;

[0024] Among them, when P cf >0, P cf is the charging power command value of the energy storage system. When P cf <0, P cf is the discharging power command value of the energy storage system; P current is the current operating power value of the energy storage system; f is the grid frequency; f N is the rated grid frequency; f d is the dead - zone frequency of fast frequency response; f max is the upper limit of the grid frequency; SOC is the real - time state of charge value of the energy storage system; SOC up is the upper limit value of the state of charge operation of the energy storage system; SOC low is the lower limit value of the state of charge operation of the energy storage; SOC min is the lower limit protection value of the state of charge of the energy storage system; SOC max is the upper limit protection value of the state of charge of the energy storage system; f min is the lower limit value of the grid frequency; σ is the droop rate of fast frequency response of the energy storage; m is the proportionality coefficient; P N is the rated power value of the energy storage system.

[0025] The present invention provides a control system for an energy storage system to participate in primary frequency regulation of the power grid. The improvement lies in that the system includes:

[0026] Acquisition module: used to collect the grid frequency in real - time on the side of the energy storage converter;

[0027] Generation module: used to generate the charge-discharge power command value of the energy storage system according to the grid frequency, and send the charge-discharge power command value of the energy storage system to the energy storage system;

[0028] The system is installed on the side of the energy storage converter.

[0029] Preferably, the control unit in the energy storage system controls the charge-discharge power of the energy storage system to be the charge-discharge power command value of the energy storage system by using the droop control algorithm based on the charge-discharge power command value of the energy storage system.

[0030] Preferably, the generation module is used for:

[0031] If f N <f<f max and SOC≤SOC up , then the charge-discharge power command value of the energy storage system

[0032] If f N <f<f max and SOC up <SOC<SOC max , then the charge-discharge power command value of the energy storage system

[0033] If f min <f<f N and SOC≥SOC low , then the charge-discharge power command value of the energy storage system

[0034] If f min <f<f N and SOC min <SOC<SOC low , then the charge-discharge power command value of the energy storage system

[0035] If f≤f min and SOC min <SOC, then the charge-discharge power command value P of the energy storage system cf =-P N ;

[0036] If f≥f max and SOC<SOC max , then the charge-discharge power command value P of the energy storage system cf =P N ;

[0037] If |f - f N |≤f dAnd P current > 0, SOC < SOC max , then the charge-discharge power command value P of the energy storage system cf = P current ;

[0038] If |f - f N | ≤ f d And P current < 0, SOC > SOC min , then the charge-discharge power command value P of the energy storage system cf = P current ;

[0039] Otherwise, the charge-discharge power command value P of the energy storage system cf = 0;

[0040] Among them, when P cf > 0, P cf is the charge power command value of the energy storage system. When P cf < 0, P cf is the discharge power command value of the energy storage system; P current is the current operating power value of the energy storage system; f is the grid frequency; f N is the rated grid frequency; f d is the dead zone frequency of the fast frequency response; f max is the upper limit of the grid frequency; SOC is the real-time state of charge value of the energy storage system; SOC up is the upper limit value of the state of charge operation of the energy storage system; SOC low is the lower limit value of the state of charge operation of the energy storage; SOC min is the lower limit protection value of the state of charge of the energy storage system; SOC max is the upper limit protection value of the state of charge of the energy storage system; f min is the lower limit value of the grid frequency; σ is the droop rate of the fast frequency response of the energy storage; m is the proportionality coefficient; P N is the rated power value of the energy storage system.

[0041] Compared with the closest prior art, the beneficial effects of the present invention are as follows:

[0042] The control method and system provided by the present invention can realize the fast response of the active power - frequency of the energy storage system through the local controller installed on the side of the energy storage converter to collect the grid frequency in real time, generate the charge-discharge power command value of the energy storage system according to the collected grid frequency, and send the charge-discharge power command value of the energy storage system to the energy storage system. The energy storage system realizes the fast support for the grid frequency through the droop control algorithm, reduces the data communication time;

[0043] The control method and system provided by the present invention divide the interval of the real-time state of charge (SOC) of the energy storage system. For different operating conditions, the energy storage system has different responses, so that the energy storage system can better respond to the system frequency change and extend the service life of the energy storage;

[0044] The control method and system provided by the present invention are applicable to the parallel operation of multiple energy storage power conversion systems (PCS), and can be widely applied to energy storage power stations or new energy / energy storage power stations. Description of the Drawings

[0045] Figure 1 is a flowchart of a control method for an energy storage system to participate in primary frequency regulation of the power grid provided by the present invention;

[0046] Figure 2 is a structural diagram of a device for primary frequency regulation of energy storage provided by the present invention;

[0047] Figure 3 is a power response curve of frequency change provided by the present invention;

[0048] Figure 4 is a structural diagram of a control system for an energy storage system to participate in primary frequency regulation of the power grid provided by the present invention. Detailed Description of the Invention

[0049] The following further elaborates on the specific implementation of the present invention with reference to the drawings.

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0051] The present invention provides a control method for an energy storage system to participate in primary frequency regulation of the power grid, as Figure 1 shown, the method includes:

[0052] Collect the power grid frequency in real time on the side of the energy storage converter;

[0053] Generate a charge and discharge power command value for the energy storage system according to the power grid frequency, and send the charge and discharge power command value of the energy storage system to the energy storage system.

[0054] Specifically, after generating the charge and discharge power command value for the energy storage system according to the power grid frequency and sending the charge and discharge power command value of the energy storage system to the energy storage system, it includes:

[0055] The control unit in the energy storage system controls the charging and discharging power of the energy storage system to the charging and discharging power command value of the energy storage system by using a droop control algorithm based on the charging and discharging power command value of the energy storage system.

[0056] In the optimal embodiment of the present invention, the real-time acquisition of the grid frequency on the side of the energy storage converter includes:

[0057] The grid frequency is real-time acquired through a local controller installed on the side of the energy storage converter.

[0058] Specifically, the generation of the charging and discharging power command value of the energy storage system according to the grid frequency and the sending of the charging and discharging power command value of the energy storage system to the energy storage system include:

[0059] The charging and discharging power command value of the energy storage system is generated according to the grid frequency through a local controller installed on the side of the energy storage converter, and the charging and discharging power command value of the energy storage system is sent to the energy storage system.

[0060] Further, the generation of the charging and discharging power command value of the energy storage system according to the grid frequency includes:

[0061] If f N <f<f max and SOC≤SOC up , then the charging and discharging power command value of the energy storage system

[0062] If f N <f<f max and SOC up <SOC<SOC max , then the charging and discharging power command value of the energy storage system

[0063] If f min <f<f N and SOC≥SOC low , then the charging and discharging power command value of the energy storage system

[0064] If f min <f<f N and SOC min <SOC<SOC low , then the charging and discharging power command value of the energy storage system

[0065] If f≤f min and SOC min <SOC, then the charging and discharging power command value P cf =-P N ;

[0066] If f ≥ f max and SOC < SOC max , then the charge-discharge power command value P of the energy storage system cf = P N ;

[0067] If |f - f N | ≤ f d and P current > 0, SOC < SOC max , then the charge-discharge power command value P of the energy storage system cf = P current ;

[0068] If |f - f N | ≤ f d and P current < 0, SOC > SOC min , then the charge-discharge power command value P of the energy storage system cf = P current ;

[0069] Otherwise, the charge-discharge power command value P of the energy storage system cf = 0;

[0070] Among them, when P cf > 0, P cf is the charging power command value of the energy storage system, when P cf < 0, P cf is the discharging power command value of the energy storage system; P current is the current operating power value of the energy storage system; f is the grid frequency; f N is the rated grid frequency; f d is the dead-band frequency of fast frequency response; f max is the upper limit of the grid frequency; SOC is the real-time state of charge value of the energy storage system; SOC up is the upper limit value of the state of charge operation of the energy storage system; SOC low is the lower limit value of the state of charge operation of the energy storage; SOC min is the lower limit protection value of the state of charge of the energy storage system; SOC max is the upper limit protection value of the state of charge of the energy storage system; f min is the lower limit value of the grid frequency; σ is the droop rate of fast frequency response of the energy storage; m is the proportionality coefficient; P N is the rated power value of the energy storage system.

[0071] In the optimal embodiment of the present invention, as Figure 2As shown, two energy storage PCSs with a capacity of 500 kW each and a battery capacity of 548 kWh each are operated in parallel and connected to the public grid through a transformer for simulation to analyze the effectiveness of the control method provided by the present invention when the grid frequency changes. The energy storage system can quickly respond to the grid frequency change as Figure 3 shown, with a response time of about 2 s. The simulation steps include:

[0072] (1) When the grid frequency f is within the frequency modulation dead zone, the initial power P of the energy storage system cf = 0 kW;

[0073] (2) At time t1, the grid frequency f rises to 50.4 Hz, and the power P of the energy storage system cf rises from 0 kW to 82 kW;

[0074] (3) At time t2, the grid frequency f drops from 50.4 Hz to 50 Hz. At this time, the grid frequency f is within the frequency modulation dead zone, and the power of the energy storage system remains unchanged, that is, P cf = 82 kW;

[0075] (4) At time t3, the grid frequency f rises from 50 Hz to 50.4 Hz, and the power P of the energy storage system cf rises from 82 kW to 116.5 kW,

[0076] (5) At time t4, the grid frequency f drops from 50.4 Hz to 50 Hz. At this time, the frequency f is within the frequency modulation dead zone, and the power P of the energy storage system cf remains unchanged, that is, P out = 116.5 kW;

[0077] (6) At time t5, the grid frequency f drops from 50 Hz to 49.6 Hz, and the power P of the energy storage system cf drops from 116.5 kW to 82 kW;

[0078] (7) At time t6, the grid frequency f rises from 49.6 Hz to 50 Hz. At this time, the frequency f is within the frequency modulation dead zone, and the power P of the energy storage system cf remains unchanged, that is, P out = 82 kW;

[0079] (8) At time t7, the grid frequency f drops from 50 Hz to 49.6 Hz, and the power P of the energy storage system cf is 0;

[0080] (9) At time t8, the grid frequency f returns to 50 Hz. At this time, the frequency f is within the frequency modulation dead zone, and the power P of the energy storage system cf remains unchanged, that is, P cf = 0.

[0081] The present invention provides a control system for a energy storage system to participate in primary frequency regulation of the power grid, as Figure 4 shown, the system includes:

[0082] A collection module: used to collect the power grid frequency in real time on the side of the energy storage converter;

[0083] A generation module: used to generate a charge-discharge power command value of the energy storage system according to the power grid frequency, and send the charge-discharge power command value of the energy storage system to the energy storage system;

[0084] The system is installed on the side of the energy storage converter.

[0085] Specifically, the control unit in the energy storage system controls the charge-discharge power of the energy storage system to be the charge-discharge power command value of the energy storage system by using a droop control algorithm based on the charge-discharge power command value of the energy storage system.

[0086] Specifically, the generation module is used for:

[0087] If f N <f<f max and SOC≤SOC up , then the charge-discharge power command value of the energy storage system

[0088] If f N <f<f max and SOC up <SOC<SOC max , then the charge-discharge power command value of the energy storage system

[0089] If f min <f<f N and SOC≥SOC low , then the charge-discharge power command value of the energy storage system

[0090] If f min <f<f N and SOC min <SOC<SOC low , then the charge-discharge power command value of the energy storage system

[0091] If f≤f min and SOC min <SOC, then the charge-discharge power command value P cf =-P N ;

[0092] If f≥f max and SOC<SOCmax , then the charge-discharge power command value P of the energy storage system cf = P N ;

[0093] If |f - f N | ≤ f d and P current > 0, SOC < SOC max , then the charge-discharge power command value P of the energy storage system cf = P current ;

[0094] If |f - f N | ≤ f d and P current < 0, SOC > SOC min , then the charge-discharge power command value P of the energy storage system cf = P current ;

[0095] Otherwise, the charge-discharge power command value P of the energy storage system cf = 0;

[0096] Among them, when P cf > 0, P cf is the charging power command value of the energy storage system. When P cf < 0, P cf is the discharging power command value of the energy storage system; P current is the current operating power value of the energy storage system; f is the grid frequency; f N is the rated grid frequency; f d is the deadband frequency of fast frequency response; f max is the upper limit of the grid frequency; SOC is the real-time state of charge value of the energy storage system; SOC up is the upper limit value of the state of charge operation of the energy storage system; SOC low is the lower limit value of the state of charge operation of the energy storage; SOC min is the lower limit protection value of the state of charge of the energy storage system; SOC max is the upper limit protection value of the state of charge of the energy storage system; f min is the lower limit value of the grid frequency; σ is the droop rate of fast frequency response of the energy storage; m is the proportionality coefficient; P N is the rated power value of the energy storage system.

[0097] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0098] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of multiple flows and / or blocks.

[0099] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing devices to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of multiple flows and / or blocks.

[0100] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, such that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process, so that the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or the combination of multiple flows and / or blocks.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still modifications or equivalent replacements can be made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A control method for a energy storage system to participate in primary frequency regulation of the power grid, characterized in that, The method includes: Real-time collecting the grid frequency on the side of the energy storage converter; Generating a charge-discharge power command value of the energy storage system according to the grid frequency, and sending the charge-discharge power command value of the energy storage system to the energy storage system; The generating the charge-discharge power command value of the energy storage system according to the grid frequency includes: If f N <f < f max and SOC ≤ SOC up , then the charge-discharge power command value of the energy storage system If f N < f < f max and SOC up < SOC < SOC max , then the charge-discharge power command value of the energy storage system If f min < f < f N and SOC ≥ SOC low , then the charge-discharge power command value of the energy storage system If f min < f < f N and SOC min < SOC < SOC low , then the charge-discharge power command value of the energy storage system If f ≤ f min and SOC min < SOC, then the charge-discharge power command value P of the energy storage system cf = -P N ; If f ≥ f max and SOC < SOC max , then the charge-discharge power command value P of the energy storage system cf = P N ; If |f - f N | ≤ f d and P current > 0, SOC < SOC max , then the charge-discharge power command value P cf = P current ; If |f - f N | ≤ f d and P current < 0, SOC > SOC min , then the charge-discharge power command value P cf = P current ; Otherwise, the charge-discharge power command value P of the energy storage system cf = 0; Among them, when P cf > 0, P cf is the charging power command value of the energy storage system. When P cf < 0, P cf is the discharging power command value of the energy storage system; P current is the current operating power value of the energy storage system; f is the grid frequency; f N is the rated grid frequency; f d is the dead - zone frequency of fast frequency response; f max is the upper limit of the grid frequency; SOC is the real - time state of charge value of the energy storage system; SOC up is the upper limit value of the state of charge operation of the energy storage system; SOC low is the lower limit value of the state of charge operation of the energy storage; SOC min is the lower limit protection value of the state of charge of the energy storage system; SOC max is the upper limit protection value of the state of charge of the energy storage system; f min is the lower limit value of the grid frequency; σ is the droop rate of the fast frequency response of the energy storage; m is the proportionality coefficient; P N is the rated power value of the energy storage system; After the generating the charge-discharge power command value of the energy storage system according to the grid frequency and sending the charge-discharge power command value of the energy storage system to the energy storage system, it includes: The control unit in the energy storage system controls the charge-discharge power of the energy storage system to be the charge-discharge power command value of the energy storage system based on the charge-discharge power command value of the energy storage system by using a droop control algorithm.

2. The method according to claim 1, wherein The real-time collecting the grid frequency on the side of the energy storage converter includes: Real-time collecting the grid frequency through a local controller installed on the side of the energy storage converter.

3. The method according to claim 1, wherein The generating the charge-discharge power command value of the energy storage system according to the grid frequency and sending the charge-discharge power command value of the energy storage system to the energy storage system includes: Generating the charge-discharge power command value of the energy storage system according to the grid frequency through a local controller installed on the side of the energy storage converter, and sending the charge-discharge power command value of the energy storage system to the energy storage system.

4. A control system for a energy storage system to participate in the primary frequency regulation of the power grid, characterized in that, The system includes: A collection module: used for real-time collecting the grid frequency on the side of the energy storage converter; A generation module: used for generating the charge-discharge power command value of the energy storage system according to the grid frequency and sending the charge-discharge power command value of the energy storage system to the energy storage system; The generation module is used for: If f N <f < f max and SOC ≤ SOC up , then the charge-discharge power command value of the energy storage system If f N < f < f max and SOC up < SOC < SOC max , then the charge-discharge power command value of the energy storage system If f min < f < f N and SOC ≥ SOC low , then the charge and discharge power command value of the energy storage system If f min < f < f N and SOC min < SOC < SOC low , then the charge-discharge power command value of the energy storage system If f ≤ f min and SOC min < SOC, then the charge-discharge power command value P of the energy storage system cf = -P N ; If f ≥ f max and SOC < SOC max , then the charge-discharge power command value P of the energy storage system cf = P N ; If |f - f N | ≤ f d and P current > 0, SOC < SOC max , then the charge-discharge power command value P cf = P current ; If |f - f N | ≤ f d and P current < 0, SOC > SOC min , then the charge-discharge power command value P cf = P current ; Otherwise, the charge-discharge power command value P of the energy storage system cf = 0; Among them, when P cf > 0, P cf is the charging power command value of the energy storage system; when P cf < 0, P cf is the discharging power command value of the energy storage system; P current is the current operating power value of the energy storage system; f is the grid frequency; f N is the rated grid frequency; f d is the dead - zone frequency of fast frequency response; f max is the upper limit of the grid frequency; SOC is the real - time state of charge value of the energy storage system; SOC up is the upper limit value of the state of charge operation of the energy storage system; SOC low is the lower limit value of the state of charge operation of the energy storage; SOC min is the lower limit protection value of the state of charge of the energy storage system; SOC max is the upper limit protection value of the state of charge of the energy storage system; f min is the lower limit value of the grid frequency; σ is the droop rate of the fast frequency response of the energy storage; m is the proportionality coefficient; P N is the rated power value of the energy storage system; The control unit in the energy storage system controls the charge-discharge power of the energy storage system to be the charge-discharge power command value of the energy storage system based on the charge-discharge power command value of the energy storage system by using a droop control algorithm; The system is installed on the side of the energy storage converter.

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