Control method and controller of networking type energy storage system

Abstract

The invention provides a control method and a controller for a network-forming type energy storage system. The control method comprises the following steps: calculating a virtual torque at a current moment based on an angular frequency at a previous moment of the network-forming type energy storage system, a rated angular frequency of a power grid and a predetermined virtual damping coefficient; pI adjustment is carried out on the virtual torque at the current moment to determine the compensation angular frequency at the current moment; according to the current moment torque deviation integral value and the current moment compensation angular frequency, the current moment angular frequency of the net-forming type energy storage system is determined; generating a current moment control signal according to the current moment angular frequency and a pre-obtained potential amplitude in the current moment; and controlling the networking type energy storage system by using the control signal at the current moment. According to the control method of the network construction type energy storage system disclosed by the embodiment of the invention, through the virtual speed regulator and the virtual motion equation, the grid connection characteristic and the control stability of the network construction type energy storage system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy storage, and more particularly, to a control method and controller of a grid-forming energy storage system. BACKGROUND

[0002] In recent years, new energy such as wind power and photovoltaic power has developed rapidly, but the random fluctuation of new energy has brought challenges to power balance and stability of the power system.

[0003] Energy storage systems have become an effective means to solve the power fluctuation of new energy due to their rapid regulation capability. The control strategies of energy storage systems mainly include PQ control (active and reactive power decoupling), droop control, and grid-forming control.

[0004] The grid-forming control simulates the rotor equation and stator equation of the traditional synchronous generator, so that the energy storage system can obtain the external characteristics of the traditional synchronous generator, has inertia and damping, and plays a buffering role on the voltage and frequency fluctuation of the power grid. The grid-forming energy storage system simulates the rotational inertia and damping winding of the synchronous generator by adding a rotor mechanical motion equation, which can improve the frequency stability. In order to realize the primary frequency modulation function of the grid-forming energy storage system, a virtual governor control structure is introduced, and the virtual motion equation and the virtual governor jointly affect the frequency control stability of the grid-forming energy storage system.

[0005] At present, most of the control structures basically follow the classical virtual synchronous generator motion equation and virtual governor control, so that the frequency transient control and steady-state control are highly coupled, and in order to take into account the design of the grid-connected parameters, the control stability is sacrificed to a certain extent.

[0006] Additional damping control is used to compensate for the constraint on transient damping control, but this control method not only has a complex control structure, but also cannot fundamentally eliminate the deviation of damping power caused by steady-state frequency deviation. In addition, a phase-locked loop can be used to extract the frequency of the grid connection point to feed forward decouple the influence of the virtual damping winding on the steady-state frequency deviation, but the introduction of the phase-locked loop deviates from the original design intention of the grid-forming control, and the introduction of the phase-locked loop structure will also worsen the control stability of the system. SUMMARY

[0007] One of the purposes of the present disclosure is to provide a control method capable of improving the control stability of the frequency transient and steady state of the grid-forming energy storage system.

[0008] One of the purposes of the present disclosure is to provide a frequency control method based on a virtual governor and a virtual motion equation, which can improve the grid-connected characteristics and control stability of the grid-forming energy storage system.

[0009] According to a first aspect of the present disclosure, a control method of a grid-forming energy storage system is provided, the control method comprising: calculating a current time virtual torque based on a previous time angular frequency of the grid-forming energy storage system, a grid rated angular frequency, and a predetermined virtual damping coefficient; performing PI regulation on the current time virtual torque to determine a current time compensation angular frequency; determining a current time angular frequency of the grid-forming energy storage system according to a current time torque deviation integral value and the current time compensation angular frequency; generating a current time control signal according to the current time angular frequency and a previously obtained current time internal electromotive force amplitude; and controlling the grid-forming energy storage system by using the current time control signal.

[0010] According to an embodiment of the present disclosure, the step of determining the current time angular frequency of the grid-forming energy storage system according to the current time torque deviation integral value and the current time compensation angular frequency can comprise: determining a sum of the current time torque deviation integral value and the current time compensation angular frequency as the current time angular frequency.

[0011] According to an embodiment of the present disclosure, the current time torque deviation integral value can be obtained by: obtaining a current time total active power given value and a previous time active power measurement value of the grid-forming energy storage system; calculating a current time active power deviation value according to the current time total active power given value and the previous time active power measurement value; calculating a current time torque given difference value according to the current time active power deviation value and the grid rated angular frequency; determining a current time torque deviation according to a difference between the current time torque given difference value and the current time virtual torque; and integrating a ratio between the current time torque deviation and a virtual moment of inertia to obtain the current time torque deviation integral value.

[0012] According to an embodiment of the present disclosure, the current time total active power given value can be a sum of a current time frequency modulation power deviation value and an active power instruction value of the grid-forming energy storage system.

[0013] According to an embodiment of the present disclosure, the current time frequency modulation power deviation value after the lead-lag correction can be obtained by: obtaining a previous time angular frequency deviation value of the grid-forming energy storage system; calculating a current time primary frequency modulation power deviation value according to the previous time angular frequency deviation value and a droop coefficient; and performing lead-lag correction on the current time primary frequency modulation power deviation value to obtain the current time frequency modulation power deviation value.

[0014] According to an embodiment of the present disclosure, the current time internal electromotive force amplitude can be obtained from a virtual excitation control link of the grid-forming energy storage system.

[0015] According to an embodiment of the present disclosure, the current time internal electromotive force amplitude can be obtained from a virtual excitation control link of the grid-forming energy storage system.

[0016] According to an embodiment of the present disclosure, the virtual excitation control link is controlled by the following steps: obtaining a total reactive power given value of the grid-connected energy storage system at the current moment and a reactive power measurement value at the previous moment; calculating a reactive power deviation value at the current moment according to the total reactive power given value at the current moment and the reactive power measurement value at the previous moment; and integrating the reactive power deviation value at the current moment to determine the potential amplitude at the current moment.

[0017] According to an embodiment of the present disclosure, the total reactive power given value at the current moment can be the sum of a reactive power instruction value of the grid-connected energy storage system and a voltage droop reactive power deviation at the previous moment, wherein the voltage droop reactive power deviation at the previous moment is obtained according to a three-phase voltage amplitude of the grid-connected energy storage system at the previous moment, a rated voltage of the grid-connected energy storage system, and a voltage droop coefficient.

[0018] According to a second aspect of the present disclosure, a controller of a grid-connected energy storage system is provided, the controller comprising a memory and a processor, the memory storing instructions or programs, and when the instructions or programs are executed by the processor, the processor is caused to perform the above control method.

[0019] According to a third aspect of the present disclosure, a computer readable storage medium is provided, the computer readable storage medium storing a computer program, and when the computer program is executed by a processor, the processor is caused to perform the above control method.

[0020] According to an embodiment of the present disclosure, not only can the virtual motion equation and the virtual frequency regulator be decoupled from the control of the frequency, but also the damping of the transient frequency mutation and the suppression of the low-frequency oscillation can be further improved on the basis of ensuring that the injection of the steady-state frequency deviation power meets the design target. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flow chart illustrating a control method according to an embodiment of the present disclosure.

[0022] Figure 2 is a flow chart illustrating a method of obtaining a current angular frequency according to an embodiment of the present disclosure.

[0023] Figure 3 is a flow chart illustrating a method of obtaining a frequency deviation value at the current moment according to an embodiment of the present disclosure.

[0024] Figure 4 is a flow chart illustrating a control step of a virtual excitation control link according to an embodiment of the present disclosure.

[0025] Figure 5 is a control block diagram of a grid-connected energy storage system according to a first embodiment of the present disclosure.

[0026] Figure 6is a control block diagram illustrating a network-forming energy storage system according to a second embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] The following detailed description is to help obtain a comprehensive understanding of the methods, devices, and / or systems described herein. However, the order of the operations described herein is merely an example, and is not limited to those set forth herein, but can be identically replaced or changed except for operations that must occur or be performed in a specific order. Also, in order to be more clear and brief, the description of the contents well-known in the art will be omitted or simplified.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs after an understanding of the present disclosure. Unless specifically defined herein, otherwise, terms such as those defined in a general dictionary should be interpreted as having a meaning consistent with their meanings in the context of the relevant art and the present disclosure, and should not be interpreted ideally or too formally.

[0029] Unless otherwise specified, the same reference numbers generally refer to the same elements (e.g., components, steps, and methods). The reference numbers described in the previous embodiments, which reappear in the subsequent embodiments, can be omitted. In addition, the technical features described in different or the same embodiments can be combined in any manner, as long as the combined embodiments or technical solutions are complete and capable of solving the technical problems of the present application or achieving the technical effects described or not described in the present disclosure but can be determined according to the above complete technical solutions. The terms used in the present disclosure are described below.

[0030] Virtual governor: refers to a key module in virtual synchronous generator (VSG) control, which simulates the governor function of a synchronous generator. The virtual governor adjusts the output power of the energy storage system according to the frequency deviation and power deviation of the system, to achieve the regulation of the system frequency. The purpose is to enable the energy storage system to automatically adjust the output power according to the load change of the system, like a synchronous generator, to maintain the stability of the system frequency.

[0031] Virtual motion equation: is an equation describing the motion of the rotor of the virtual synchronous generator. It simulates the rotor motion equation of the synchronous generator, and introduces virtual inertia and virtual damping to make the energy storage system have inertia and damping characteristics similar to the synchronous generator. The role of the virtual motion equation is to enable the energy storage system to provide inertia support and damping effect when the system has power fluctuations, thereby improving the stability and reliability of the system.

[0032] The present disclosure improves the damping of transient frequency jumps and the suppression of low-frequency oscillations on the basis that the injection of steady-state frequency deviation power meets the design target. In addition, the present disclosure can decouple the control of frequency by the virtual motion equation and the virtual governor.

[0033] Figure 1 is a flow chart illustrating a control method according to an embodiment of the present disclosure, Figure 2 is a flow chart illustrating a method of obtaining a current angular frequency according to an embodiment of the present disclosure, Figure 3 is a flow chart illustrating a method of obtaining a current-time governor power deviation value according to an embodiment of the present disclosure, Figure 4 is a flow chart illustrating a control step of a virtual excitation control link according to an embodiment of the present disclosure, Figure 5 is a control block diagram of a grid-forming energy storage system according to a first embodiment of the present disclosure, Figure 6 is a control block diagram of a grid-forming energy storage system according to a second embodiment of the present disclosure.

[0034] The control method of the grid-forming energy storage system according to an embodiment of the present disclosure can include steps S110, S120, S130, S140 and S150.

[0035] In step S110, a current-time virtual torque is calculated based on a previous-time angular frequency of the grid-forming energy storage system, a grid rated angular frequency and a predetermined virtual damping coefficient.

[0036] The previous-time angular frequency can be a previous-time angular frequency obtained by a virtual motion equation. The angular frequency of the grid-forming energy storage system at any time can be obtained by iterative calculation. The initial-time angular frequency can be zero or the grid angular frequency at steady state (i.e., ω n = 2πf, and the frequency f is 50 Hz). When the frequency fluctuates, the control method of the present disclosure can improve the damping of transient frequency jumps and the suppression of low-frequency oscillations. In addition, the control method of the present disclosure can not need to obtain the grid phase through a phase-locked loop structure.

[0037] Here, the virtual motion equation is an existing mechanical motion equation used to simulate a conventional synchronous generator. Its simplified form can be represented by the following equation (1).

[0038]

[0039] In equation (1), J is a virtual moment of inertia used to simulate the inertia of the energy storage system; δ is the power angle, representing the phase difference of the energy storage system relative to the grid; D is a virtual damping coefficient used to simulate the damping effect and help suppress system oscillation; and respectively represent the rate of change of angular acceleration and angular velocity, and Pm is the active power provided by the energy storage system; P e is the electromagnetic power, related to the voltage and current in the energy storage system, reflecting the actual consumption or generation of electrical energy by the energy storage system. This equation describes the dynamic behavior of the "virtual rotor" of the energy storage system, which can participate in frequency regulation of the power grid by controlling the exchange of active power, providing necessary inertia support and damping effect, thereby enhancing the stability and dynamic response performance of the power grid. In practical applications, the virtual moment of inertia J and the virtual damping coefficient D can be designed and adjusted according to the requirements of the energy storage system.

[0040] The parameters of the virtual moment of inertia J can be designed according to the technical index requirements of the power grid frequency power inertia guide, and the virtual moment of inertia can be determined by the following equations (3) and (4).

[0041] The parameters of the power-frequency droop coefficient can be designed according to the technical index requirements of the power grid frequency power primary frequency modulation guide, and the primary frequency modulation power deviation value ΔP can be calculated by the following equation (2).

[0042]

[0043] According to the existing formula, the relationship between ΔP and Δω (Δf) is obtained, and the parameters of the power-frequency droop coefficient K f are designed; in equation (2), ΔP is the primary frequency modulation power deviation value, Δf is the frequency deviation (the deviation of the actual frequency of the power grid from the rated frequency), P n is the rated active power of the energy storage system, f n is the rated frequency of the power grid, and δ is the regulation coefficient.

[0044] According to the technical index requirements of the power grid frequency power inertia guide, T J can be calculated according to the following equations (3) and (4), and the virtual moment of inertia J can be designed; the virtual moment of inertia can be calculated by the following equation (3).

[0045]

[0046] In equation (3), ΔP is the primary frequency modulation power deviation value, Δf is the frequency deviation, f is the measured frequency, P n is the rated active power of the energy storage system, f n is the rated frequency of the power grid, ω n is the rated angular velocity, and T j is the equivalent inertia time constant.

[0047] According to the technical index requirements of the power grid damping guide, the maximum value of the damping active power change rate ΔP for suppressing low-frequency oscillation is not less than 10% P n and not more than 30% P n, the provided oscillation energy flow W should be less than zero, thus the virtual damping coefficient D or D p ; the oscillation energy W controlled by damping can be calculated by the following formula (4).

[0048] ΔP = D p *Δω

[0049] W = ∫(ΔP*2πΔf)dt (4)

[0050] The calculation method in the above formula (1)-(4) is only an example, the disclosure is not limited thereto, and the virtual damping coefficient D or D p may also be designed by other methods, for example, the above calculation method can be simplified.

[0051] In step S120, the current time virtual torque is PI (proportional integral) adjusted to determine the current time compensation angular frequency.

[0052] The transfer function of the proportional integral adjustment here can be represented by the following formula (5):

[0053]

[0054] In formula (5), K p is the proportional gain of PI adjustment, T i is the integral time constant of PI adjustment. The PI adjustment can be a PI adjustment in which the proportional term and the integral term are connected in series, so that the rapid response and the steady-state accuracy can be well considered, the deviation is quickly responded by the proportional term, and the steady-state error is continuously eliminated by the integral term.

[0055] In step S130, the current time angular frequency of the grid-forming energy storage system is determined according to the current time torque deviation integral value and the current time compensation angular frequency.

[0056] As an example, the step of determining the current time angular frequency of the grid-forming energy storage system according to the current time torque deviation integral value and the current time compensation angular frequency can include determining the sum of the current time torque deviation integral value and the current time compensation angular frequency as the current time angular frequency.

[0057] As an example, the sum of the product of the current time compensation angular frequency and a preset coefficient and the current time torque deviation integral value can be determined as the current time angular frequency, and the way of determining the current time angular frequency is not limited thereto.

[0058] The control method of the grid-forming energy storage system according to the embodiment of the disclosure can obtain the angular frequency or phase of the energy storage system through the virtual motion equation. The control method of the grid-forming energy storage system according to the embodiment of the disclosure can not need a phase-locked loop structure.

[0059] Referring to Figure 2The current-time torque deviation integral value can be obtained through step S131, step S132, step S133, step S134 and step S135.

[0060] In step S131, the current-time total active power given value of the grid-forming energy storage system and the previous-time active power measured value are obtained.

[0061] The current-time total active power given value of the grid-forming energy storage system can be obtained from the grid dispatch. The grid dispatch sends an instruction of the active power given value to the grid-forming energy storage system according to the operation and demand of the grid, and the energy storage system adjusts the output power according to the instruction to meet the requirements of the grid. The current-time total active power given value here can also include the primary frequency power deviation value.

[0062] In step S132, the current-time active power deviation value is calculated according to the current-time total active power given value and the previous-time active power measured value.

[0063] As an example, the difference between the current-time total active power given value and the previous-time active power measured value can be taken as the current-time active power deviation value. The previous-time active power measured value can be calculated according to the measured three-phase voltage (the measured value of the three-phase alternating current voltage at the machine end of the grid-forming energy storage system) and three-phase current (the measured value of the three-phase alternating current at the machine end of the grid-forming energy storage system) of the energy storage system.

[0064] In step S133, the current-time torque given difference value is calculated according to the current-time active frequency deviation value and the rated angular frequency of the grid. The current-time torque given difference value is the ratio of the current-time active frequency deviation value to the rated angular frequency of the grid.

[0065] In step S134, the current-time torque deviation is determined according to the difference between the current-time torque given difference value and the current-time virtual torque. The current-time virtual torque can be calculated by the product of the angular frequency deviation and the virtual damping coefficient.

[0066] In step S135, the ratio between the current-time torque deviation and the virtual moment of inertia is integrated to obtain the current-time torque deviation integral value. In the process of frequency control, the current-time torque deviation integral value can be adjusted to zero or close to zero.

[0067] In step S140, the current-time control signal is generated according to the current-time angular frequency and the pre-obtained current-time internal voltage amplitude.

[0068] As an example, the current-time internal voltage amplitude can be obtained from the virtual excitation control link of the grid-forming energy storage system.

[0069] The virtual excitation control link can be an existing virtual excitation control mode of the grid-connected energy storage system. The virtual excitation control link can generally be realized by adjusting the output voltage of the energy storage converter, so that the internal potential amplitude of the energy storage system can be controlled according to the demand of the energy storage system, to maintain the stable operation of the energy storage system. The common virtual excitation control mode can obtain the internal potential amplitude of the converter output based on the output voltage and the output current of the energy storage converter. By measuring the voltage and current at the output end, the amplitude of the internal potential can be calculated and compared with the reference value. Then, the control signal of the converter is adjusted by the regulator (such as proportional integral regulator) to make the internal potential amplitude track the reference value.

[0070] According to an embodiment of the present disclosure, with reference to Figure 4 , the virtual excitation control link can be controlled by the following steps: step S310, step S320 and step S330.

[0071] In step S310, the total reactive power given value at the current time of the grid-connected energy storage system and the reactive power measured value at the previous time are obtained.

[0072] The total reactive power given value at the current time of the grid-connected energy storage system can be obtained from the grid dispatch, or can be determined according to the operating state and demand of the grid. The reactive power measured value at the previous time can be determined based on the three-phase voltage, three-phase current, voltage droop coefficient, etc. of the grid-connected energy storage system measured at the previous time.

[0073] The active power measured value P, the reactive power value Q and the internal potential instantaneous value e abc of the grid-connected energy storage system at the current time can be calculated by the following formula (6).

[0074]

[0075] Wherein, E is the effective value of the internal potential of the grid-connected energy storage system, and the effective value of the internal potential can be the internal potential amplitude divided by e abc is the internal potential instantaneous value of the grid-connected energy storage system, e abc⊥ is the orthogonal quantity after the internal potential is phase-shifted by 90°, and the symbols < and > represent the inner product of the phasor. P and Q are the active power (i.e. the active power measured value) and the reactive power (i.e. the reactive power value) of the grid-connected energy storage system calculated according to the instantaneous power theory, respectively, and ω n is the rated angular frequency of the energy storage system.

[0076] In step S320, the reactive power deviation value at the current time is calculated according to the total reactive power given value at the current time and the reactive power measured value at the previous time.

[0077] The current time total reactive power given value is the sum of the reactive power instruction value of the grid-forming energy storage system and the voltage droop reactive power deviation of the previous time, wherein the voltage droop reactive power deviation of the previous time is obtained according to the three-phase voltage amplitude of the grid-forming energy storage system of the previous time, the rated voltage of the grid-forming energy storage system and the voltage droop coefficient. The reactive power measurement value of the previous time can be calculated according to the above formula (6), and the above calculation is also an iterative calculation, and the initial values of various parameters can be determined according to the specific design of the energy storage system. The amplitude V of the three-phase voltage of the grid-forming energy storage system at any time can be calculated according to the measured three-phase voltage.

[0078] In step S330, the current time reactive power deviation value is integrated to determine the internal potential amplitude at the current time.

[0079] As an example, the ratio of the current time reactive power deviation value and the reactive closed-loop integral time constant can be integrated to calculate the reactive power deviation integral value, so as to obtain the internal potential amplitude at the current time.

[0080] The phase angle can be obtained by integrating the current time angular frequency, and then the control signal is generated based on the obtained phase angle and the internal potential amplitude at the current time. The control signal can be generated based on the phase angle and the internal potential amplitude according to the existing mode, for example, the control voltage can be generated according to the mode of coordinate transformation and coordinate inverse transformation, which can be loaded into the pulse width modulation unit to generate the control signal.

[0081] In step S150, the grid-forming energy storage system is controlled by using the current time control signal.

[0082] The energy storage converter can adjust the active power of the energy storage system under the control of the control signal, thereby reducing the grid frequency deviation.

[0083] As described above, the PI control of the damping torque T D is added in the virtual motion equation, thereby compensating for the steady-state frequency deviation.

[0084] However, since the frequency deviation compensation of the damping power weakens the effect of transient damping to some extent, as a preferred embodiment, a lead-lag corrector can be connected in series with the frequency droop control of the virtual governor to increase the effect of transient damping. In this way, through the coordinated control of the improved virtual governor and the virtual motion equation on the frequency damping, not only the design target of the steady-state frequency deviation power injection is met, but also the flexibility of the control parameter design is improved due to the decoupling of the transient and steady-state control, and the frequency damping control stability is further enhanced.

[0085] For details, please refer to Figure 3The current time frequency modulation power deviation value after the lead and lag correction can be obtained through step S210, step S220 and step S230.

[0086] In step S210, the previous time angular frequency deviation value of the grid-connected energy storage system is obtained.

[0087] The previous time angular frequency deviation value can be the difference between the rated angular frequency of the energy storage system and the previous time angular frequency. The angular frequency at any time can be obtained by iterative calculation, and the initial angular frequency can be zero or the grid rated angular frequency, but this is only an example.

[0088] In step S220, the current time primary frequency modulation power deviation value is calculated according to the previous time angular frequency deviation value and the droop coefficient.

[0089] The primary frequency modulation power deviation value can be calculated by formula (2) above.

[0090] In step S230, the current time primary frequency modulation power deviation value is corrected in advance and lag to obtain the current time frequency modulation power deviation value.

[0091] The transfer function of the lead-lag correction is as follows:

[0092]

[0093] In formula (7), T1 is the first correction time constant of the lead-lag correction, and T2 is the second correction time constant of the lead-lag correction. The first correction time constant and the second time constant can be selected according to the previous engineering experience and the debugging data of similar systems, but this is only an example. The first time constant and the second time constant of the lead-lag correction can also be determined by calculation according to the mathematical model of the energy storage system and the control theory. As an example, the energy storage system can also be modeled and simulated by using simulation software, and the optimal first time constant and second time constant can be determined by adjusting the time constants of the lead-lag correction and observing the response and performance of the system.

[0094] The technical concept of the present disclosure will be described in detail below. Figure 5 and Figure 6 The technical concept of the present disclosure will be described in detail below.

[0095] Referring to Figure 5 and Figure 6 , in the virtual governor control link, the previous time angular frequency deviation value is determined according to the difference between the previous time angular frequency ω of the grid-connected energy storage system and the rated angular frequency ω n , and the previous time angular frequency deviation value is divided by the set droop coefficient K f to obtain the current time primary frequency modulation power deviation value ΔP.

[0096] The primary frequency power deviation value ΔP is controlled by leading-lagging correction, and the current time primary frequency power deviation value ΔP is obtained new .

[0097] According to the active power instruction P received by the energy storage system from the grid scheduling set and the corrected current time primary frequency power deviation value ΔP new The sum of the current time total active power given value of the energy storage system is obtained, and then the difference between the active power P obtained by measurement and calculation is divided by the rated angular frequency ω n The torque given difference value ΔT of the energy storage system (i.e. the current time torque given difference value) is obtained.

[0098] The previous time angular frequency ω of the energy storage system is subtracted from the rated angular frequency ω n , multiplied by the virtual damping coefficient D of the energy storage system p , and the current time virtual torque T D is obtained. The current time virtual torque T D is compensated by the damping torque, and the current time compensation angular frequency ω c is obtained.

[0099] The sum of the current time torque deviation integral value and the current time compensation angular frequency is the current time angular frequency of the grid-connected energy storage system. The current time torque deviation integral value can be obtained by integrating the difference between the torque given difference value ΔT of the energy storage system and the virtual damping torque T D .

[0100] Referring to Figure 6 , v abc is the measured value of the three-phase AC voltage at the machine terminal of the grid-connected energy storage system, i abc is the measured value of the three-phase AC current at the machine terminal of the grid-connected energy storage system, V is the amplitude of the AC voltage at the machine terminal of the energy storage system, V n is the rated AC voltage effective value at the machine terminal of the energy storage system. D q is the voltage droop coefficient, P set (i.e. the active power given value), Q set (i.e. the reactive power given value) are the active and reactive instruction reference values of the grid-connected energy storage system, K is the reactive closed-loop integral time constant, E is the internal potential effective value of the grid-connected energy storage system, e abc is the instantaneous value of the internal potential of the grid-connected energy storage system, P and Q are the active power (i.e. the active power measurement value) and the reactive power (i.e. the reactive power measurement value) calculated by the grid-connected energy storage system according to the instantaneous power theory. ω n is the rated angular frequency of the energy storage system, D p is the virtual damping coefficient, K fwherein K is the droop coefficient, J is the virtual moment of inertia, ω is the angular frequency of the energy storage system, and θ is the phase angle of the energy storage system.

[0101] The steady-state frequency deviation is compensated by adding PI control of the damping torque in the virtual motion equation.

[0102] Since the frequency deviation compensation of the damping torque weakens the effect of transient damping to some extent, a lead-lag corrector is connected in series with the frequency droop control of the virtual governor to increase the effect of transient damping. Thus, not only is the design goal of injecting the power of the steady-state frequency deviation met, but the flexibility of the design of the control parameters is improved due to the decoupling of the transient and steady-state controls, and the stability of the frequency damping control is further enhanced.

[0103] The controller of the networked energy storage system according to the embodiments of the present disclosure can include a memory and a processor, the memory stores instructions or programs, and when the instructions or programs are executed by the processor, the processor is caused to perform the control method described above.

[0104] The computer readable storage medium according to the embodiments of the present disclosure stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the control method described above.

[0105] The instructions stored in the computer readable storage medium described above can be run in an environment deployed in a computer device such as a client, a host, an agent device, a server, etc. It should be noted that the instructions can also be used to perform additional steps in addition to the steps described above or perform more specific processing when performing the steps described above. The content of these additional steps and further processing has been mentioned in the description of the related systems and methods, and therefore will not be described here in detail to avoid repetition. Figures 1 to 5 The description of the related systems and methods has been mentioned in the description process, and therefore will not be described here in detail to avoid repetition.

[0106] It should be noted that the control method according to the exemplary embodiments of the present disclosure can completely rely on the running of the computer program or instructions to realize the corresponding functions, i.e., each device corresponds to each step in the functional architecture of the computer program, so that the entire system is called by a special software package (e.g., lib library) to realize the corresponding functions.

[0107] On the other hand, when the systems, units or modules shown in the drawings are implemented in software, firmware, middleware or microcode, the program code or code segments for performing the corresponding operations can be stored in a computer readable medium such as a storage medium, so that at least one processor or at least one computing device can perform the corresponding operations by reading and running the corresponding program code or code segments, in addition, the computer readable medium or storage medium can cause the processor to perform the control method described above when the computer program is executed by the processor.

[0108] For example, according to the exemplary embodiments of the present disclosure, a computer device including a readable medium storing computer program instructions can be provided, wherein the instructions, when executed by at least one computing device, cause the at least one computing device to perform at least one of the above steps.

[0109] According to the control method of the embodiments of the present disclosure, the design of the frequency power droop coefficient in the virtual governor and the virtual damping coefficient in the virtual motion equation is decoupled, and the respective control of the steady-state frequency deviation and the transient frequency damping by the network-forming control strategy is decoupled.

[0110] According to the embodiments of the present disclosure, not only can the curve characteristics of primary frequency modulation be flexibly designed according to the different frequency power droop characteristics of the power grid, but also the parameters of the virtual damping can be flexibly and unrestrictedly designed according to the control stability and low-frequency oscillation suppression of the energy storage system, the tracking error of the active power instruction is avoided by using the damping frequency compensation, and the operation reliability of the energy storage system is improved.

[0111] According to the embodiments of the present disclosure, a lead-lag correction module is further used in the link of the virtual governor to further improve the transient damping effect, and the grid-connected characteristics and control stability of the network-forming energy storage system are improved through the coordinated frequency control of the virtual governor and the virtual motion equation.

[0112] The control method according to the embodiments of the present disclosure can improve the control stability of the frequency transient state.

[0113] The control method according to the embodiments of the present disclosure improves the grid-connected characteristics and control stability of the network-forming energy storage system through the coordinated frequency control of the virtual governor and the virtual motion equation.

[0114] The specific embodiments of the present disclosure are described in detail above, although some embodiments have been shown and described, those skilled in the art should understand that the embodiments can be combined, modified and improved without departing from the principles and spirits of the present disclosure, which are defined by the claims and their equivalents, and these combinations, modifications and improvements should also be within the protection scope of the present disclosure.

Claims

1. A control method for a grid-type energy storage system, characterized in that, The control method includes: The virtual torque at the current moment is calculated based on the previous angular frequency of the grid-type energy storage system, the rated angular frequency of the power grid, and the predetermined virtual damping coefficient. The virtual torque at the current moment is PI-adjusted to determine the compensation angular frequency at the current moment; The current angular frequency of the grid-type energy storage system is determined based on the integral value of the torque deviation at the current moment and the compensation angular frequency at the current moment. The control signal for the current moment is generated based on the current angular frequency and the pre-obtained potential amplitude for the current moment. The grid-type energy storage system is controlled using the current time control signal.

2. The control method for a grid-type energy storage system according to claim 1, characterized in that, The step of determining the current angular frequency of the grid-type energy storage system based on the current torque deviation integral value and the current compensation angular frequency includes: determining the current angular frequency as the sum of the current torque deviation integral value and the current compensation angular frequency.

3. The control method for a grid-type energy storage system according to claim 1, characterized in that, The integral value of the torque deviation at the current moment is obtained in the following way: Obtain the current total active power setpoint and the previous active power measurement value of the grid-type energy storage system; The active power deviation value at the current moment is calculated based on the given value of total active power at the current moment and the measured value of active power at the previous moment; Calculate the torque setpoint difference at the current moment based on the current active power deviation value and the rated angular frequency of the power grid; The torque deviation at the current moment is determined based on the difference between the current moment's torque given difference and the current moment's virtual torque; The ratio between the current torque deviation and the virtual moment of inertia is integrated to obtain the integral value of the current torque deviation.

4. The control method for a grid-type energy storage system according to claim 3, characterized in that, The current total active power given value is the sum of the current frequency regulation power deviation value and the active power command value of the grid-type energy storage system.

5. The control method for a grid-type energy storage system according to claim 4, characterized in that, The current frequency modulation power deviation value is the current frequency modulation power deviation value after lead and lag correction.

6. The control method for a grid-type energy storage system according to claim 5, characterized in that, The frequency modulation power deviation value at the current moment after lead and lag corrections is obtained as follows: Obtain the angular frequency deviation value of the grid-type energy storage system at the previous moment; Calculate the primary frequency modulation power deviation value at the current moment based on the angular frequency deviation value and droop coefficient at the previous moment. The frequency modulation power deviation value at the current moment is corrected by leading and lagging corrections to obtain the frequency modulation power deviation value at the current moment.

7. The control method for a grid-type energy storage system according to claim 1, characterized in that, The current potential amplitude is obtained from the virtual excitation control link of the grid-type energy storage system.

8. The control method for a grid-type energy storage system according to claim 7, characterized in that, The virtual excitation control circuit is controlled through the following steps: Obtain the current total reactive power setpoint and the previous reactive power measurement value of the grid-type energy storage system; Calculate the reactive power deviation value at the current moment based on the given total reactive power value at the current moment and the measured reactive power value at the previous moment. Integrate the reactive power deviation value at the current moment to determine the potential amplitude at the current moment.

9. The control method for a grid-type energy storage system according to claim 8, characterized in that, The current total reactive power setpoint is the sum of the reactive power command value of the grid-type energy storage system and the reactive power deviation due to voltage droop at the previous moment. The reactive power deviation due to voltage droop at the previous moment is calculated based on the three-phase voltage amplitude of the grid-type energy storage system at the previous moment, the rated voltage of the grid-type energy storage system, and the voltage droop coefficient.

10. A controller for a grid-type energy storage system, characterized in that, It includes a memory and a processor, the memory storing instructions or programs, and when the instructions or programs are executed by the processor, causing the processor to perform the control method according to any one of claims 1 to 9.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, causes the processor to perform the control method according to any one of claims 1 to 9.

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