Method for improving grid frequency characteristics by energy storage system and related devices

Abstract

The application provides a method for improving the frequency characteristics of a power grid by using an energy storage system and related devices. The energy storage system comprises at least one target energy storage module, a flywheel energy storage module, an energy storage converter and a rectifier. The output end of each flywheel energy storage module is connected to the AC end of the corresponding rectifier. The output end of each target energy storage module, the DC end of each energy storage converter and the DC end of each rectifier are all connected to a DC bus. The AC end of each energy storage converter is connected to a power grid bus. The method comprises using a VSG control method to control the energy storage converter so that the energy storage converter provides virtual rotor inertia to maintain the stability of the power grid frequency. The above method takes into account the characteristics of the flywheel energy storage module being a rotating system and therefore having a fast response speed. The flywheel energy storage module compensates for the slow response speed of the target energy storage module VSG of the non-rotating system, so that the energy storage converter provides virtual rotor inertia that is adaptive to changes in the power grid frequency, thereby improving the stability of the power grid frequency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage systems, and particularly relates to a method for improving frequency characteristics of a power grid by an energy storage system and a related device. BACKGROUND

[0002] A synchronous generator provides a large amount of mechanical inertia for the power grid, can be naturally coupled with the power grid, and participates in the regulation of the voltage and frequency of the power grid. When a fault occurs in the power system, the mechanical inertia of the synchronous generator can provide sufficient rotating reserve capacity to make up for the power loss. After the "double carbon" target is proposed, the proportion of photovoltaic energy storage systems connected to the grid is increasing, and the proportion of synchronous generators in the power system is also decreasing.

[0003] In order to make up for the lack of voltage and frequency regulation capability brought by the connection of photovoltaic energy storage systems to the grid, the prior art usually uses a VSG (Virtual Synchronous Generator) to embed the rotor motion equation of a synchronous generator and reactive droop control algorithm into an inverter control system. When the power grid is subjected to a fault or disturbance, the distributed power generation of the inverter control system is adjusted to realize the working characteristics similar to those of a synchronous generator. Although the photovoltaic energy storage VSG can increase the virtual inertia for the power grid, its response speed is slow, and the improvement effect on the stability of the power system is not good. SUMMARY

[0004] The embodiments of the present application provide a method for improving the frequency characteristics of a power grid by an energy storage system and a related device to solve the problem that the existing photovoltaic energy storage VSG has a poor improvement effect on the stability of the power system.

[0005] In a first aspect, the embodiments of the present application provide a method for improving the frequency characteristics of a power grid by an energy storage system, wherein the energy storage system includes a target energy storage module, a flywheel energy storage module, an energy storage converter, and a rectifier; the output end of the target energy storage module is connected to the direct current end of the energy storage converter; the output end of the energy storage converter is connected to a power grid bus; the output end of the flywheel energy storage module is connected to the alternating current end of the rectifier; and the direct current end of each rectifier is connected to the direct current end of the energy storage converter.

[0006] The method includes:

[0007] For any energy storage converter, a VSG control method is used to control the energy storage converter, so that the energy storage converter provides virtual rotor inertia to maintain the stability of the frequency of the power grid.

[0008] In a second aspect, an embodiment of the present application provides a device for improving frequency characteristics of a power grid by a storage system, the storage system comprising at least one target storage module, at least one flywheel storage module, a storage converter corresponding to each target storage module, and a rectifier corresponding to each flywheel storage module; an output end of each target storage module and a direct current end of each storage converter are connected to a direct current bus, respectively; an output end of each flywheel storage module is connected to an alternating current end of a corresponding rectifier; a direct current end of each rectifier is connected to the direct current bus; and an alternating current end of each storage converter is connected to a power grid bus.

[0009] The device comprises:

[0010] a VSG control module configured to control, for any storage converter, the storage converter by using a VSG control method, so that the storage converter provides a virtual rotor inertia to maintain stability of the power grid frequency.

[0011] In a third aspect, an embodiment of the present application provides a terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements steps of the method for improving frequency characteristics of a power grid by a storage system according to any possible implementation manner of the first aspect.

[0012] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executable on a processor to implement steps of the method for improving frequency characteristics of a power grid by a storage system according to any possible implementation manner of the first aspect.

[0013] In a fifth aspect, an embodiment of the present application provides a storage system, comprising at least one target storage module, at least one flywheel storage module, a storage converter corresponding to each target storage module, a rectifier corresponding to each flywheel storage module, and a terminal according to the third aspect.

[0014] An output end of each target storage module and a direct current end of each storage converter are connected to a direct current bus, respectively; an output end of each flywheel storage module is connected to an alternating current end of a corresponding rectifier; a direct current end of each rectifier is connected to the direct current bus; and an alternating current end of each storage converter is connected to a power grid bus.

[0015] The embodiment of the present application provides a method for improving the frequency characteristics of a power grid by a storage system and a related device, the storage system comprising a target storage module, a flywheel storage module, a storage converter and a rectifier, and for any storage converter, a VSG control method is used to control the storage converter, so that the storage converter provides virtual rotor inertia to maintain the stability of the power grid frequency. The above method considers that the flywheel storage module is a rotating system and has the characteristics of fast response speed, and the VSG control of the flywheel storage module corresponding to the inverter compensates for the slow response speed of the photovoltaic storage VSG of the non-rotating system, so as to jointly provide virtual inertia for the power grid and improve the stability of the power grid frequency. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 is an application scenario diagram of the method for improving the frequency characteristics of the power grid by the storage system provided by the embodiment of the present application;

[0018] Figure 2 is a flowchart of the method for improving the frequency characteristics of the power grid by the storage system provided by the embodiment of the present application;

[0019] Figure 3 is a VSG control flowchart provided by the embodiment of the present application;

[0020] Figure 4 is an SPWM signal generation flowchart provided by the embodiment of the present application;

[0021] Figure 5 is a structural schematic diagram of the device for improving the frequency characteristics of the power grid by the storage system provided by the embodiment of the present application;

[0022] Figure 6 is a schematic diagram of the terminal provided by the embodiment of the present application. DETAILED DESCRIPTION

[0023] In the following description, specific details are set forth in order to provide a thorough understanding of the embodiments of the present application, such as specific system structures, techniques, etc. However, it should be apparent to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits and methods are omitted so as not to obscure the description of the present application with unnecessary details.

[0024] In order to make the purpose, technical scheme and advantages of the present application clearer, specific embodiments will be described below with reference to the drawings.

[0025] Figure 1 The application scenario diagram of the VSG control method of the energy storage system provided by the embodiments of the present application is shown in FIG. 1. Figure 1 As shown in FIG. 1, the energy storage system comprises target energy storage modules BAT, flywheel energy storage modules M (M1, M2,..., MN), energy storage converters PCS (PCS1, PCS2,..., PCSn) and rectifiers AC / DC; the output end of each target energy storage module BAT and the DC end of each energy storage converter PCS are respectively connected to a DC bus, the output end of each flywheel energy storage module M is connected to the AC end of a corresponding rectifier AC / DC, the DC end of each rectifier AC / DC is connected to the DC bus, and the AC end of each energy storage converter PCS is connected to a grid bus; and the output end of each flywheel energy storage module is also used to connect the grid bus.

[0026] Specifically, the target energy storage module is an energy storage module other than the flywheel energy storage module, and can specifically include a photovoltaic energy storage module, a wind power energy storage module or an energy storage battery. When the target energy storage module is a photovoltaic energy storage module, the target energy storage module comprises a photovoltaic plate, a DCDC module and a battery module, and the photovoltaic plate is connected to one end of the DCDC module, and the other end of the DCDC is connected to the output end of the target energy storage module and the battery module. The method provided by the present application will be described in detail below taking the photovoltaic energy storage module as an example.

[0027] Referring to FIG. 2, it shows an implementation flowchart of the VSG control method of the energy storage system provided by the embodiments of the present application, which is described in detail as follows. Figure 2

[0028] S101: For any energy storage converter, the VSG control method is used to control the energy storage converter, so as to make the energy storage converter provide virtual rotor inertia and maintain the stability of the grid frequency.

[0029] The execution subject of the present embodiment is a control host of the energy storage system, which is communicatively connected to the controller of the target energy storage module, the controller of the rectifier and the controller of the energy storage converter, and is used to respectively issue power control instructions to the controller of the rectifier and the controller of the target energy storage module, and issue VSG control instructions to the controller of the energy storage converter, so that the flywheel energy storage module and the target energy storage module each provide power to the energy storage converter, so that the energy storage converter outputs corresponding virtual rotor inertia to maintain the stability of the grid frequency.

[0030] ​In the embodiment, the virtual synchronous machine technology is a technology of simulating the electromechanical transient characteristics of a synchronous unit, so that a power source or load using a converter has the operating external characteristics such as inertia, damping, frequency and voltage adjustment of the synchronous unit. Since a common energy storage system such as a photovoltaic energy storage system is usually a non-rotating system, the speed of the corresponding virtual synchronous generator in responding to the change of the grid frequency is slow, and thus the grid frequency cannot be adjusted in time when the grid fluctuation is large. In the primary frequency control stage, the flywheel energy storage module is connected to the grid in the embodiment, which does not cause further fluctuation of the grid, and the slow response speed of the photovoltaic energy storage VSG of the non-rotating system is compensated by the virtual inertia provided by the flywheel energy storage, so that the flywheel energy storage and the photovoltaic energy storage are used to provide virtual inertia for the grid when the grid frequency fluctuation is large, so that the grid frequency is quickly stabilized.

[0031] In one possible implementation, the specific implementation process of S101 includes:

[0032] Adaptively determining a virtual rotor inertia corresponding to the energy storage converter based on the grid frequency;

[0033] Dividing the virtual rotor inertia into a fixed first virtual rotor inertia and a second virtual rotor inertia that changes adaptively with the grid frequency;

[0034] Controlling the given output power of each target energy storage module based on the first virtual rotor inertia;

[0035] Controlling the given output power of each rectifier based on the second virtual rotor inertia;

[0036] Performing VSG control on the energy storage converter using the virtual rotor inertia.

[0037] In one possible implementation, the specific implementation process of determining the virtual rotor inertia includes:

[0038] Adaptively determining a virtual rotor inertia corresponding to the energy storage converter based on the grid frequency;

[0039]

[0040] Calculating the virtual rotor inertia;

[0041] In formula (1), J represents the virtual rotor inertia, J0 represents a steady-state value of the virtual rotor inertia, ω represents a virtual rotor angular velocity of the energy storage converter, ω g represents a grid angular velocity, and ω g = 2πf g , wherein f g represents the grid frequency, k represents a constant, and C represents a threshold value of a virtual rotor angular velocity change rate.

[0042] wherein J0 represents a virtual rotor inertia steady-state value, which can be determined based on a natural vibration angular velocity of the synchronous generator.

[0043] Specifically, the size of the virtual rotor inertia is determined by the difference between the virtual angular velocity of the VSG and the grid angular velocity, and the size of the virtual angular velocity, when the virtual angular velocity of the VSG is greater than the grid angular velocity and the virtual angular velocity of the VSG is greater than zero, the virtual rotor inertia will increase, when the virtual angular velocity of the VSG is greater than the grid angular velocity and the virtual angular velocity of the VSG is less than zero, the virtual rotor inertia will decrease, when the virtual angular velocity of the VSG is less than the grid angular velocity and the virtual angular velocity of the VSG is less than zero, the virtual rotor inertia will increase, when the virtual angular velocity of the VSG is less than the grid angular velocity and the virtual angular velocity of the VSG is greater than zero, the virtual rotor inertia will decrease. Based on the above principle, the present application determines the size of the virtual rotor inertia that the energy storage converter VSG needs to output based on the grid frequency, thereby improving the frequency response speed of the energy storage system.

[0044] In the present embodiment, the energy storage converter performs VSG control according to a fixed control period, and the calculation of the virtual rotor inertia J of the energy storage converter VSG in the present control period in the above formula (1) is obtained by the current grid frequency and the virtual rotor angular velocity of the VSG in the last control period. After determining the virtual rotor inertia J in the present control period, the virtual rotor inertia is divided into two parts (the first virtual rotor inertia and the second virtual rotor inertia), one part is provided by the output power of all flywheel energy storage modules, and the other part is provided by the output power of all target energy storage modules, so it is necessary to determine the given output power of each target energy storage module based on the first virtual rotor inertia, and to determine the given output power of the rectifier corresponding to each flywheel energy storage module based on the second virtual rotor inertia.

[0045] In one possible implementation, Figure 3 The control flow chart of the energy storage converter is shown as follows, Figure 3 As shown, the specific implementation process of using the virtual rotor inertia to perform VSG control on the energy storage converter includes:

[0046] S201: input the actual value U of the input voltage of the energy storage converter into the input voltage regulation loop, and output the given amplitude e of the VSG voltage of the energy storage converter o The input active power P of the energy storage converter is input into the input active-power-frequency regulation loop, and the phase of the VSG is output a The input active power P of the energy storage converter is input into the input active-power-frequency regulation loop, and the phase of the VSG is output b The input active power P of the energy storage converter is input into the input active-power-frequency regulation loop, and the phase of the VSG is output c ;

[0047] S202: input the input active power P of the energy storage converter into the input active-power-frequency regulation loop, and output the phase of the VSG The virtual rotor inertia is a parameter value in the input active-power-frequency regulation loop;

[0048] S203: Based on the given voltage amplitude e of the energy storage converter VSG a ,e b ,e c Phase with VSG Get the three-phase given voltage of the energy storage converter VSG.

[0049] In this embodiment, the input power of the energy storage converter is obtained by dividing the power of the DC bus by the number of energy storage converters, and the input active power and input reactive power of the energy storage converter are determined based on the input power of the energy storage converter.

[0050] Specifically, the specific implementation process of S201 includes:

[0051] Get the actual value of the input voltage U of the energy storage converter o ;

[0052] Set the input voltage rated value U ref Subtract the actual value of input voltage U o , get the input voltage error;

[0053] The reactive power Q ref Subtract the output reactive power Q of the energy storage converter after limiting to obtain the reactive power error;

[0054] The input voltage error and the voltage regulation coefficient k v Multiply them to get the first control quantity; multiply the reactive power error and the reactive power adjustment coefficient k q Multiply them to get the second control quantity;

[0055] Add the first control variable, the second control variable and the no-load electromotive force E0 of the energy storage converter VSG to obtain the given voltage amplitude e of the energy storage converter VSG a ,e b ,e c ;

[0056] Specifically, such as Figure 3 As shown, the specific implementation process of S202 includes:

[0057] The given active power P ref Subtract the input active power P of the energy storage converter to obtain the active power difference;

[0058] Based on the formula Calculate the virtual rotor angular velocity ω of VSG; integrate the virtual rotor angular velocity ω of VSG to obtain the phase of VSG

[0059] Where ω0 represents the synchronous angular velocity of the power grid, D represents the damping coefficient corresponding to the damping torque, and T dThe damping torque is from mechanical friction, stator loss, excitation and damping windings.

[0060] In one possible implementation, the specific implementation process of S203 includes:

[0061] Based on the formula

[0062]

[0063] The three-phase given voltage of the energy storage converter VSG is calculated.

[0064] In formula (2), e a represents the a-phase given voltage, e b represents the b-phase given voltage, e c represents the c-phase given voltage, E p represents the amplitude of the phase voltage, E represents the amplitude of the given energy storage converter VSG voltage, represents the phase of the VSG, and ω represents the virtual rotor angular velocity.

[0065] In one possible implementation, Figure 4 The generation process block diagram of the SPWM (Sinusoidal Pulse Width Modulation) signal for controlling the energy storage converter is shown. As shown in Figure 4 After obtaining the three-phase given voltage of the energy storage converter, the three-phase given voltage is input to Figure 4 As shown in the control loop, the SPWM signal is generated. Figure 4 In formula (3), i ref represents the rated grid-connected current, i a , i b and i c respectively represent the three-phase output currents; i e represents the output current deviation; PR is a proportional resonant regulator, L represents inductance, R represents local resistance, u m represents the voltage amplitude of the modulation signal.

[0066] In this embodiment, after obtaining the sinusoidal pulse width modulation signal, the sinusoidal pulse width modulation signal is used to control the respective switching tubes of the energy storage converter, so that the energy storage converter outputs the corresponding virtual rotor inertia.

[0067] From the above flow, the size of the virtual rotor angular velocity depends on the input power of the energy storage converter, and the input power of the energy storage converter is derived from the output power of the target energy storage module connected to the DC bus and the output power of the corresponding rectifier of the flywheel energy storage module, so the virtual rotor angular velocity of the VSG can be adjusted by setting the given output power of each rectifier and the given output power of each target energy storage module, and then the virtual rotor inertia output by the VSG is adjusted.

[0068] From the above embodiment, when the power grid system is relatively stable, the original photovoltaic energy storage module corresponding to the VSG is used to stabilize the power grid frequency. When the power grid frequency fluctuates greatly, based on the advantages of fast response speed of the adaptive virtual rotor inertia method and the fast response speed of the flywheel energy storage system as a rotating system, on the basis of the photovoltaic energy storage VSG, the flywheel energy storage provides virtual rotor inertia to fine-tune the power grid frequency, so as to not only fully utilize the fast response speed of the flywheel energy storage VSG rotating system, but also not need to configure a large-capacity flywheel energy storage module.

[0069] In one possible implementation, the specific implementation process of S101 includes:

[0070] Adaptively determining the virtual rotor inertia based on the power grid frequency;

[0071] Dividing the virtual rotor inertia into a first virtual rotor inertia that changes adaptively with the power grid frequency and a second virtual rotor inertia that is fixed;

[0072] Controlling the given output power of each target energy storage module based on the first virtual rotor inertia;

[0073] Controlling the given output power of each rectifier based on the second virtual rotor inertia;

[0074] Controlling the VSG of the energy storage converter using the virtual rotor inertia.

[0075] The embodiment can preferentially allocate a fixed output power to the rectifier corresponding to the flywheel energy storage module, and make the target energy storage module provide an output power that adaptively changes with the power grid frequency, thereby improving the response speed of the energy storage converter VSG and further improving the power grid frequency stability.

[0076] In one possible implementation, the specific implementation process of S101 includes:

[0077] Adaptively obtaining a virtual rotor inertia based on the power grid frequency;

[0078] if the virtual rotor inertia is less than or equal to the first virtual rotor inertia maximum value, the virtual rotor inertia is used to control the given output power of each target energy storage module, and the given output power of each rectifier is controlled to be zero;

[0079] if the virtual rotor inertia is greater than the first virtual rotor inertia maximum value, the first virtual rotor inertia maximum value is used to control the given output power of each target energy storage module, and a second virtual rotor inertia is used to control the given output power of each rectifier; the second virtual rotor inertia is the difference between the virtual rotor inertia and the first virtual rotor inertia maximum value;

[0080] the virtual rotor inertia is used to perform VSG control on the energy storage converter.

[0081] Specifically, the embodiment can preferentially use the target energy storage module to provide power for the energy storage converter VSG, and when the output power of the target energy storage module is insufficient to support the virtual rotor inertia demand of the energy storage converter VSG, the flywheel energy storage module is enabled to provide power for the energy storage converter. Wherein, the size of the virtual rotor angular velocity is positively correlated with the size of the input power of the energy storage converter, so when only the target energy storage module is used to supply power to the energy storage converter, the first virtual rotor inertia maximum value is the virtual rotor inertia output by the energy storage converter when the maximum overload capacity of all target energy storage modules.

[0082] In the embodiment, the control host determines that the output power of the target energy storage module cannot make the energy storage converter output sufficient virtual inertia to support the grid frequency when it is monitored that the virtual rotor inertia is equal to the first virtual rotor inertia maximum value for a first preset time duration, or the number of sampling time points at which the virtual rotor inertia is equal to the first virtual rotor inertia maximum value accounts for a preset percentage of the total number of sampling time points in a second preset time duration, and then controls the rectifier to output power to the energy storage converter to ensure that the energy storage converter VSG outputs sufficient virtual rotor inertia.

[0083] The preset percentage can be 60% to 80%.

[0084] In one possible implementation, the specific implementation process of S101 includes:

[0085] The virtual rotor inertia is adaptively obtained based on the grid frequency;

[0086] if the virtual rotor inertia is less than or equal to the second virtual rotor inertia maximum value, the virtual rotor inertia is used to control the given output power of each rectifier, and the given output power of each target energy storage module is controlled to be zero;

[0087] If the virtual rotor inertia is greater than the second virtual rotor inertia maximum value, the first virtual rotor inertia maximum value is adopted to control the given output power of each rectifier, and the second virtual rotor inertia is adopted to control the given output power of each target energy storage module; the second virtual rotor inertia is the difference between the virtual rotor inertia demand value and the first virtual rotor inertia maximum value;

[0088] The virtual rotor inertia is adopted to control the VSG of the energy storage converter.

[0089] Specifically, the embodiment can preferentially adopt each flywheel energy storage module to provide power for the VSG of the energy storage converter, and when the output power of the flywheel energy storage module is insufficient to support the virtual rotor inertia demand of the VSG of the energy storage converter, the target energy storage module is enabled to provide power for the energy storage converter. Wherein, the size of the virtual rotor angular velocity is positively correlated with the size of the input power of the energy storage converter, so when only the flywheel energy storage module is used to supply power to the energy storage converter, the second virtual rotor inertia maximum value is the virtual rotor inertia output by the energy storage converter when the maximum overload capacity of all flywheel energy storage modules.

[0090] In the embodiment, the control host determines that the output power of the flywheel energy storage module cannot make the energy storage converter output sufficient virtual inertia to support the grid frequency when it is monitored that the virtual rotor inertia is equal to the second virtual rotor inertia maximum value for a first preset time duration, or the number of sampling time points at which the virtual rotor inertia is equal to the second virtual rotor inertia maximum value accounts for a preset percentage of the total number of sampling time points in the second preset time duration, and then controls the target energy storage module to output power to the energy storage converter to ensure that the VSG of the energy storage converter outputs sufficient virtual rotor inertia. It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0091] The following is a device embodiment of the present application, and for details not described in detail, reference can be made to the corresponding method embodiments described above.

[0092] Figure 5 The structure schematic diagram of the device for improving the frequency characteristics of the energy storage system provided by the embodiment of the present application is shown, only the parts related to the embodiment of the present application are shown for the convenience of description, and the details are as follows:

[0093] As shown in Figure 5 The device for improving the frequency characteristics of the energy storage system 100 comprises:

[0094] The VSG control module 110 is configured to control, for any energy storage converter, the energy storage converter using a VSG control method to make the energy storage converter provide a virtual rotor inertia to maintain stability of the grid frequency.

[0095] In one possible implementation, the VSG control module 110 comprises:

[0096] a virtual rotor inertia obtaining unit configured to adaptively determine the virtual rotor inertia based on the grid frequency;

[0097] a first inertia partitioning unit configured to control a given output power of each target energy storage module based on the first virtual rotor inertia;

[0098] a target energy storage module control unit configured to control a given output power of each rectifier based on the second virtual rotor inertia;

[0099] a rectifier control unit configured to control a given output power of the rectifier based on the second virtual rotor inertia;

[0100] a VSG control unit configured to perform VSG control of the energy storage converter using the virtual rotor inertia.

[0101] In one possible implementation, the virtual rotor inertia obtaining unit comprises:

[0102] the virtual rotor inertia is calculated based on a formula

[0103] wherein J represents the virtual rotor inertia, J0 represents a virtual rotor inertia steady-state value, ω represents a virtual rotor angular velocity of the energy storage converter, ω g represents a grid angular velocity, and ω g = 2πf g wherein f g represents the grid frequency, and k represents a constant, C represents a threshold value of a virtual rotor angular velocity change rate.

[0104] In one possible implementation, the VSG control module 110 comprises:

[0105] the virtual rotor inertia is adaptively determined based on the grid frequency;

[0106] the virtual rotor inertia is partitioned into a first virtual rotor inertia that varies adaptively with the grid frequency and a second virtual rotor inertia that is fixed;

[0107] a given output power of each target energy storage module is controlled based on the first virtual rotor inertia;

[0108] a given output power of each rectifier is controlled based on the second virtual rotor inertia;​

[0109] The virtual rotor inertia is used to control the VSG of the energy storage converter.

[0110] In one possible implementation, the VSG control module 110 comprises:

[0111] The virtual rotor inertia is adaptively obtained based on the grid frequency;

[0112] If the virtual rotor inertia is less than or equal to a first virtual rotor inertia maximum value, the virtual rotor inertia is used to control the given output power of each target energy storage module, and the given output power of each rectifier is controlled to be zero;

[0113] If the virtual rotor inertia is greater than the first virtual rotor inertia maximum value, the first virtual rotor inertia maximum value is used to control the given output power of each target energy storage module, and a second virtual rotor inertia is used to control the given output power of each rectifier; the second virtual rotor inertia is the difference between the virtual rotor inertia and the first virtual rotor inertia maximum value;

[0114] The virtual rotor inertia is used to control the VSG of the energy storage converter.

[0115] In one possible implementation, the VSG control module 110 comprises:

[0116] The virtual rotor inertia is adaptively obtained based on the grid frequency;

[0117] If the virtual rotor inertia is less than or equal to a second virtual rotor inertia maximum value, the virtual rotor inertia is used to control the given output power of each rectifier, and the given output power of each target energy storage module is controlled to be zero;

[0118] If the virtual rotor inertia is greater than the second virtual rotor inertia maximum value, the first virtual rotor inertia maximum value is used to control the given output power of each rectifier, and a second virtual rotor inertia is used to control the given output power of each target energy storage module; the second virtual rotor inertia is the difference between the virtual rotor inertia and the first virtual rotor inertia maximum value;

[0119] The virtual rotor inertia is used to control the VSG of the energy storage converter.

[0120] From the above embodiment, it can be seen that the above device considers the fast response speed of the flywheel energy storage module as a rotating system, and compensates for the slow response speed of the target energy storage module of the non-rotating system, so as to jointly provide power for the energy storage converter, so that the energy storage converter provides a virtual rotor inertia that is adaptive to the change of the grid frequency, and improves the stability of the grid frequency.

[0121] Figure 6 is a schematic diagram of a terminal provided by an embodiment of the present application. As shown in the figure, the terminal 6 of this embodiment comprises a processor 60 and a memory 61. The memory 61 is configured to store a computer program 62, and the processor 60 is configured to invoke and run the computer program 62 stored in the memory 61 to perform the steps in the above-mentioned method embodiments for improving the frequency characteristics of the power grid by the energy storage system, such as the step 101 shown in the figure. Figure 6 Alternatively, the processor 60 is configured to invoke and run the computer program 62 stored in the memory 61 to implement the functions of the modules / units in the above-mentioned device embodiments, such as the functions of the module 110 shown in the figure. Figure 2 Figure 5 For example, the computer program 62 can be divided into one or more modules / units, which are stored in the memory 61 and executed by the processor 60 to complete the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program 62 in the terminal 6.

[0122] The terminal 6 can be a desktop computer, a notebook computer, a palm computer, a cloud server, and other computing devices. The terminal 6 can include, but is not limited to, the processor 60, the memory 61. Those skilled in the art can understand that The terminal 6 shown in the figure is merely an example and does not constitute a limitation on the terminal 6, which can include more or fewer components than those shown in the figure, or combine certain components, or different components, for example, the terminal can also include an input / output device, a network access device, a bus, etc.

[0123] The processor 60 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. Figure 6

[0124]

[0125] ​​The memory 61 can be an internal storage unit of the terminal 6, such as a hard disk or a memory of the terminal 6. The memory 61 can also be an external storage device of the terminal 6, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal 6. Further, the memory 61 can also include both the internal storage unit and the external storage device of the terminal 6. The memory 61 is used to store the computer program and other programs and data required by the terminal. The memory 61 can also be used to temporarily store data that has been output or will be output.

[0126] It can be clearly understood by those skilled in the art that, for the convenience and brevity of description, only the division of the above functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or in the form of software functional unit. In addition, the specific names of each functional unit and module are only for convenient distinction, and do not limit the protection scope of the present application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0127] The embodiment of the present application provides a kind of energy storage system, it includes at least one target energy storage module, at least one flywheel energy storage module, each target energy storage module corresponding energy storage converter, each flywheel energy storage module corresponding rectifier and as described above terminal;

[0128] The output end of each target energy storage module, the DC end of each energy storage converter is connected to DC bus respectively, the output end of each flywheel energy storage module is connected with the AC end of corresponding rectifier respectively, the DC end of each rectifier is all connected to the DC bus, and the AC end of each energy storage converter is connected with grid bus.

[0129] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0130] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / terminal and method can be implemented in other ways. For example, the apparatus / terminal embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between each set of interfaces can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or in other forms.

[0131] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. they can be located in one place, or distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0132] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0133] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the above-mentioned various energy storage system method embodiments for improving the grid frequency characteristics. The computer program includes computer program code, which can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practices, computer-readable media does not include electrical carrier signals and telecommunication signals.

[0134] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A method for improving grid frequency characteristics of an energy storage system, characterized by, The energy storage system comprises at least one target energy storage module, at least one flywheel energy storage module, an energy storage converter corresponding to each target energy storage module, and a rectifier corresponding to each flywheel energy storage module; the output end of each target energy storage module and the DC end of each energy storage converter are respectively connected to a DC bus, the output end of each flywheel energy storage module is connected to the AC end of the corresponding rectifier, the DC end of each rectifier is connected to the DC bus, and the AC end of each energy storage converter is connected to a grid bus; The method comprises: For any energy storage converter, a VSG control method is used to control the energy storage converter, so that the energy storage converter provides virtual rotor inertia to maintain the stability of the grid frequency; The VSG control method for any energy storage converter comprises: Adaptively determining the virtual rotor inertia corresponding to the energy storage converter based on the grid frequency; Dividing the virtual rotor inertia into a fixed first virtual rotor inertia and a second virtual rotor inertia that changes adaptively with the grid frequency, or dividing the virtual rotor inertia into a first virtual rotor inertia that changes adaptively with the grid frequency and a fixed second virtual rotor inertia; Controlling the given output power of each target energy storage module based on the first virtual rotor inertia; Controlling the given output power of each rectifier based on the second virtual rotor inertia; Controlling the energy storage converter using the virtual rotor inertia.

2. The method of claim 1, wherein the energy storage system improves grid frequency characteristics by, The method for adaptively determining the virtual rotor inertia corresponding to the energy storage converter based on the grid frequency comprises: Based on the formula computing the virtual rotor inertia; where J represents the virtual rotor inertia, J0 represents a virtual rotor inertia steady state value; ω represents a virtual rotor angular speed of the energy storage converter, ω g represents the grid angular speed, and ω g = 2πf g where f g represents the grid frequency, k represents a constant, and C represents a threshold value for the virtual rotor angular speed change rate.

3. The method of claim 1, wherein the energy storage system improves grid frequency characteristics by, The VSG control method for any energy storage converter comprises: Adaptively obtaining the virtual rotor inertia based on the grid frequency; If the virtual rotor inertia is less than or equal to the maximum value of the first virtual rotor inertia, the given output power of each target energy storage module is controlled using the virtual rotor inertia, and the given output power of each rectifier is controlled to be zero; If the virtual rotor inertia is greater than the maximum value of the first virtual rotor inertia, the given output power of each target energy storage module is controlled using the maximum value of the first virtual rotor inertia, and the given output power of each rectifier is controlled using the second virtual rotor inertia; the second virtual rotor inertia is the difference between the virtual rotor inertia and the maximum value of the first virtual rotor inertia; Controlling the energy storage converter using the virtual rotor inertia.

4. The method of claim 1, wherein the energy storage system improves grid frequency characteristics by, The VSG control method for any energy storage converter comprises: Adaptively obtaining the virtual rotor inertia based on the grid frequency; If the virtual rotor inertia is less than or equal to the maximum value of the second virtual rotor inertia, the given output power of each rectifier is controlled using the virtual rotor inertia, and the given output power of each target energy storage module is controlled to be zero; If the virtual rotor inertia is greater than the second virtual rotor inertia maximum value, the first virtual rotor inertia maximum value is used to control the given output power of each rectifier, and the second virtual rotor inertia is used to control the given output power of each target energy storage module; the second virtual rotor inertia is the difference between the virtual rotor inertia and the first virtual rotor inertia maximum value; The virtual rotor inertia is used to perform VSG control on the energy storage converter.

5. An apparatus for improving grid frequency characteristics of an energy storage system, comprising: Comprise: The energy storage system comprises at least one target energy storage module, at least one flywheel energy storage module, a corresponding energy storage converter of each target energy storage module, and a corresponding rectifier of each flywheel energy storage module; The output end of each target energy storage module and the DC end of each energy storage converter are respectively connected to a DC bus, the output end of each flywheel energy storage module is respectively connected to the AC end of the corresponding rectifier, the DC end of each rectifier is connected to the DC bus, and the AC end of each energy storage converter is connected to a power grid bus; The device comprises: A VSG control module is configured to control any energy storage converter using a VSG control method to make the energy storage converter provide a virtual rotor inertia and maintain the stability of the power grid frequency; The VSG control module comprises: Adaptively determining the virtual rotor inertia corresponding to the energy storage converter based on the power grid frequency; Dividing the virtual rotor inertia into a fixed first virtual rotor inertia and a second virtual rotor inertia that changes adaptively with the power grid frequency, or dividing the virtual rotor inertia into a first virtual rotor inertia that changes adaptively with the power grid frequency and a fixed second virtual rotor inertia; Controlling the given output power of each target energy storage module based on the first virtual rotor inertia; Controlling the given output power of each rectifier based on the second virtual rotor inertia; Using the virtual rotor inertia to perform VSG control on the energy storage converter.

6. A terminal, characterized by comprising: The computer program is executed by the processor to implement the steps of the method for improving the power grid frequency characteristics of the energy storage system according to any one of claims 1 to 4.

7. A computer-readable storage medium storing a computer program, wherein the computer program comprises the following steps of: receiving a request for a resource from a client; determining whether the client is authorized to access the resource; and if the client is authorized to access the resource, providing the resource to the client. The computer program is executed by the processor to implement the steps of the method for improving the power grid frequency characteristics of the energy storage system according to any one of claims 1 to 4.

8. An energy storage system characterized by, Comprise: At least one target energy storage module, at least one flywheel energy storage module, a corresponding energy storage converter of each target energy storage module, a corresponding rectifier of each flywheel energy storage module, and a terminal according to claim 6; The output end of each target energy storage module and the DC end of each energy storage converter are respectively connected to a DC bus, the output end of each flywheel energy storage module is respectively connected to the AC end of the corresponding rectifier, the DC end of each rectifier is connected to the DC bus, and the AC end of each energy storage converter is connected to a power grid bus.

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