A method and system for suppressing frequency fluctuation of a wind power grid-connected power system, and a medium

Abstract

A self-disturbance-resistant wind power grid-connected power system frequency fluctuation suppression method, system and medium, the method comprises the following steps: a wind power grid-connected system frequency dynamic response model containing variable speed wind turbine is established; based on the wind power grid-connected system frequency dynamic response model, the real-time state of the system frequency deviation is observed, the comprehensive disturbance in and outside the system is estimated, the active power output of the variable speed wind turbine is adjusted in real time to respond to the change of the grid frequency; real-time monitoring of the error between the system frequency deviation and the target frequency deviation, further adjusting the active power output of the variable speed wind turbine, realizing the wind power grid-connected frequency fluctuation suppression. The frequency response characteristic of the wind turbine is improved, and the influence of wind power fluctuation on the system frequency is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind power grid connection, in particular to a self-disturbance-resistant wind power grid connection power system frequency fluctuation suppression method, system and medium. BACKGROUND

[0002] New energy power generation represented by wind power has been rapidly developed and gradually replaced traditional thermal power units due to its advantages of being clean, low-carbon and efficient, which has accelerated the transformation pace of China's power system framework to a new type of power system dominated by new energy. As one of the most widely used models in the wind power industry, variable speed wind turbines are decoupled from the grid frequency through the grid-connected converter, and cannot respond to system frequency changes. Moreover, variable speed wind turbines usually operate in maximum power point tracking mode and do not have active frequency modulation capability. In a high proportion of wind power grid-connected power system, random changes in wind speed will cause large fluctuations in wind power, and may cause system frequency to exceed the limit when transmitted to the grid side, thereby triggering over-frequency tripping and low-frequency load shedding of relay protection devices, and even causing a "frequency collapse" of the entire grid.

[0003] The wind turbine improves the grid frequency regulation capability through virtual inertia control and energy storage auxiliary control, but in the face of large frequency deviation caused by severe wind power fluctuations, the cost of energy storage equipment is high, the regulation output is constrained by service life, and the control strategy is complex, so it is difficult to adjust the system frequency in real time according to wind power fluctuations, load demand and real-time state of the grid, increasing the burden of system frequency regulation. In addition, due to the characteristics of wind turbine converter input and output multivariable, nonlinearity and slow response of synchronous units, it is difficult to quickly track the random changes of wind power by calculating the frequency deviation of the actual measured frequency deviation to calculate the frequency modulation power of the variable speed wind turbine, which will result in poor wind turbine frequency modulation effect and insufficient rotor kinetic energy utilization. SUMMARY

[0004] In view of the above defects of the prior art, the present application provides a self-disturbance-resistant wind power grid connection power system frequency fluctuation suppression method, system and medium, which considers the influence of wind turbine converter input and output multivariable, nonlinearity and slow response of synchronous units, and uses the "observation + compensation" method based on the self-disturbance-resistant control algorithm to solve the nonlinearity and uncertainty disturbance in the system. A system frequency fluctuation suppression strategy based on self-disturbance-resistant control is proposed for frequency sensitive mode scenarios, which improves the frequency stability of the power system under high wind power penetration.

[0005] A self-disturbance-resistant wind power grid connection power system frequency fluctuation suppression method, comprising the following steps:

[0006] establishing a wind power grid connection system frequency dynamic response model containing variable speed wind turbines;

[0007] Based on the wind power grid-connected system frequency dynamic response model, the real-time state of system frequency deviation is observed, the comprehensive disturbance inside and outside the compensation system is estimated, and the active power output of variable speed wind turbine is adjusted in real time to respond to the change of grid frequency;

[0008] The error between the system frequency deviation and the target frequency deviation is monitored in real time, and the active power output of the variable speed wind turbine is further adjusted to suppress the frequency fluctuation of the wind power grid-connected system;

[0009] Further, the wind power grid-connected system frequency dynamic response model containing variable speed wind turbine is established, and the specific steps include:

[0010] The rotor side of the variable speed wind turbine adopts a typical power droop control structure, and the active power regulation increment and the active power reference value when the wind turbine frequency is suppressed are:

[0011] ΔP FR =-K p Δf sys (1)

[0012] P w =P MPPT +ΔP FR (2)

[0013] In the formula: K p =-1 / R is the fixed gain coefficient of the power droop control of the variable speed wind turbine; Δf sys is the frequency deviation of the measured frequency f sys of the alternating current system and the reference frequency 50Hz; ΔP FR is the active output increment of the wind turbine; P w is the active power reference value of the wind turbine; P MPPT is the active power output of the wind turbine in the maximum power point tracking mode.

[0014] The frequency dynamic response model of the system is characterized as:

[0015]

[0016] In the formula: P TSG is the active power reference value of the traditional synchronous unit; P TSG0 is the initial output of the traditional synchronous unit; ΔP TSG is the TSG frequency modulation increment power; P dtb is the power disturbance suffered by the system; P dtb0 is the original basic load of the system; ΔP dtb is the basic load sudden increment; H sys is the equivalent inertia time constant of the system; D sys is the equivalent damping coefficient of the system.

[0017] The active power of the traditional synchronous generator and the variable speed wind turbine meets the power balance with the basic load in the normal operation state of the system, i.e.

[0018] P TSG0 +P MPPT =P dtb0 (4)

[0019] The frequency dynamic response model of the system is linearized to obtain:

[0020]

[0021] In the formula: D sys ′=D sys +K p is the equivalent damping coefficient of the system with the variable speed wind turbine using power droop control.

[0022] Further, based on the frequency dynamic response model of the wind power grid-connected system, the real-time state of the system frequency deviation is observed, the comprehensive disturbance in and outside the system is estimated, and the active power of the variable speed wind turbine is adjusted in real time to respond to the change of the grid frequency, and the specific steps include:

[0023] The linear extended state observation algorithm is used to realize the real-time and accurate estimation of the disturbance and the real-time tracking of the system frequency deviation, to perceive the existence and change of the disturbance, so as to better offset the influence of the disturbance on the frequency modulation process. Let Δf sys =x be a state variable, and according to the linearized system frequency dynamic response model, the state space equation of the system frequency response model is written as:

[0024]

[0025] In the formula: F(x, E(t)) is the comprehensive disturbance of the wind power grid-connected system, including wind speed uncertainty, response speed of the traditional synchronous generator, external load change and other unknown disturbances that the system may face; E(t) is the external disturbance that the whole system may receive; b0 is a non-zero disturbance compensation coefficient of the real-time estimation value of the system comprehensive disturbance; u=u(t) and y=y(t) are respectively the control variable input and output of the system.

[0026] Each variable in the state space equation can be expressed as:

[0027]

[0028] The u(t) is introduced into the linear extended state observation algorithm through the real-time compensation of b0, and the real-time online connection with the system is established:

[0029]

[0030] The extended observation quantity of F(x, E(t)) is z2:

[0031]

[0032] The nonlinear system containing wind power frequency modulation is subjected to disturbance dynamic compensation linearization processing.

[0033]

[0034] In order to realize the observation of system disturbance, the state expansion is carried out on F(x, E(t)) in the state space equation and represented by state variable x2, and then the following state space expression is obtained:

[0035]

[0036] In the formula: x1 is Δf sys , x2 is the expansion state variable of system disturbance.

[0037] In order to realize accurate and real-time observation of state variable Δf sys change and "observation + compensation" of system F(x, E(t)), the state observation mechanism in linear expansion state observation algorithm for suppressing wind power grid-connected power fluctuation and the disturbance expansion compensation mode are designed, and the output equation is:

[0038]

[0039] In the formula: z1 is the observation value of system state variable x1; e is the deviation between the observation value of state variable and the actual state of the system. η1, η2 are the set control coefficients of linear expansion state observation algorithm, and η1 is 2 and η2 is 1.

[0040] According to the system expansion state observation design method of output equation, the disturbance dynamic compensation of linearized nonlinear system containing wind power frequency modulation is rewritten as:

[0041]

[0042] Further, the error between the real-time monitoring system frequency deviation and the target frequency deviation is further adjusted to adjust the active power output of the variable speed wind turbine, and the wind power grid-connected frequency fluctuation is suppressed, and the specific steps include:

[0043] The influence of disturbance is offset by linear error state feedback control algorithm, the rotor kinetic energy release of variable speed wind turbine following system real-time frequency state is improved, the wind power fluctuation is suppressed as much as possible, and x1 tends to Δf sys_ref The output of linear error state feedback control algorithm is designed as:

[0044] u0(t)=η3(Δf sys_ref -z1) (14)

[0045] In the formula: η 3 is a set linear error state feedback control algorithm control coefficient, η 3 =1 / 250h 2 Wherein h is a sampling step, the value is determined according to the system control accuracy, Δf sys_ref It is a frequency deviation, usually 0.

[0046] Combined with the linear extended state observation algorithm and the linear error state feedback control algorithm, the designed active regulation increment of the wind turbine frequency flattening is ultimately output as:

[0047]

[0048] In the formula, b0 mainly realizes the compensation of the system F(x, E(t)), and is strongly related to the inertia time constant of the system.

[0049] Further, b0 is 1 / (2H sys ).

[0050] An active disturbance rejection wind power grid-connected power system frequency fluctuation flattening system, comprising: a computer readable storage medium and a processor;

[0051] The computer readable storage medium is used to store executable instructions;

[0052] The processor is used to read the executable instructions stored in the computer readable storage medium, and execute the active disturbance rejection wind power grid-connected power system frequency fluctuation flattening method.

[0053] A non-transitory computer readable storage medium, having stored thereon a computer program, which is executed by a processor to implement the active disturbance rejection wind power grid-connected power system frequency fluctuation flattening method.

[0054] The present application has the following beneficial effects relative to the prior art:

[0055] The present application realizes real-time state accurate observation of frequency deviation, estimation and compensation of internal and external comprehensive disturbance of the system, and real-time monitoring of the error between the system frequency deviation and the target reference frequency deviation based on feedforward control, and forms a double closed-loop control structure by comprehensively combining the two, which can more effectively suppress unknown comprehensive disturbance of the system and ultimately offset the influence of the disturbance on the frequency fluctuation of the wind power grid-connected system, and enhances the disturbance suppression capability of the wind power grid-connected system. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 is a flowchart of a self-disturbance rejection wind power grid-connected power system frequency fluctuation flattening method provided by an embodiment of the present application;

[0057] Figure 2A self-disturbance-resistant wind power grid-connected power system frequency fluctuation suppression control structure diagram provided by the embodiment of the present application is shown in the figure.

[0058] Figure 3 A four-machine two-area system structure diagram with wind power grid connection provided by the embodiment of the present application is shown in the figure.

[0059] Figure 4 A random wind speed change diagram provided by the embodiment of the present application is shown in the figure.

[0060] Figure 5 A system frequency change diagram under the condition of random wind speed and 25% wind power penetration rate provided by the embodiment of the present application is shown in the figure.

[0061] Figure 6 A wind turbine active power output diagram under the condition of random wind speed and 25% wind power penetration rate provided by the embodiment of the present application is shown in the figure.

[0062] Figure 7 A system frequency deviation probability distribution diagram under the condition of random wind speed and 25% wind power penetration rate provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0063] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0064] Please refer to Figure 1 The first aspect of the present application provides a self-disturbance-resistant wind power grid-connected power system frequency fluctuation suppression method, comprising the following steps:

[0065] Step one, establish a wind power grid-connected system frequency dynamic response model containing variable speed wind turbine generators;

[0066] Step two, based on the wind power grid-connected system frequency dynamic response model, observe the real-time state of the system frequency deviation, estimate the compensation of the comprehensive disturbance inside and outside the system, and adjust the active power output of the variable speed wind turbine generator in real time to respond to the change of the grid frequency;

[0067] Step three, real-time monitor the error between the system frequency deviation and the target frequency deviation, further adjust the active power output of the variable speed wind turbine generator, and realize the wind power grid-connected frequency fluctuation suppression;

[0068] The step one of establishing a wind power grid-connected system frequency dynamic response model containing variable speed wind turbine generators comprises the following specific steps:

[0069] The rotor side of the variable speed wind turbine adopts a typical power droop control structure. The active power regulation increment and the active power reference value when the wind turbine frequency is stabilized are:

[0070] ΔP FR = -K p Δf sys (1)

[0071] P w = P MPPT + ΔP FR (2)

[0072] wherein: K p = -1 / R is a fixed gain coefficient of the power droop control adopted by the variable speed wind turbine; Δf sys is a frequency deviation of the measured frequency f sys of the alternating current system from the reference frequency 50 Hz; ΔP FR is an active output increment of the wind turbine; P w is a wind turbine active power reference value; P MPPT is an active output of the wind turbine in the maximum power point tracking mode.

[0073] The frequency dynamic response model of the system is represented as:

[0074]

[0075] wherein: P TSG is an active power reference value of the traditional synchronous unit; P TSG0 is an initial output of the traditional synchronous unit; ΔP TSG is a TSG frequency modulation increment power; P dtb is a power disturbance suffered by the system; P dtb0 is an original basic load of the system; ΔP dtb is a basic load sudden increment; H sys is an equivalent inertia time constant of the system; D sys is an equivalent damping coefficient of the system.

[0076] The active outputs of the traditional synchronous unit and the variable speed wind turbine and the basic load satisfy the power balance under the normal operation state of the system, i.e.

[0077] P TSG0 + P MPPT = P dtb0 (4)

[0078] The frequency dynamic response model of the system is linearized to obtain:

[0079]

[0080] wherein: D sys' = D sys + K p The equivalent damping coefficient of the system using power droop control for variable speed wind turbine.

[0081] The second step is based on the frequency dynamic response model of the wind power grid-connected system, observing the real-time state of the system frequency deviation, estimating the compensation of the comprehensive disturbance in and out of the system, and adjusting the active power output of the variable speed wind turbine in real time in response to the change of the grid frequency. The specific steps include:

[0082] The linear extended state observation algorithm is used to realize real-time and accurate estimation of the disturbance and real-time tracking of the system frequency deviation, so as to better offset the influence of the disturbance on the frequency modulation process. Let Δf sys = x as a state variable, according to the linearized system frequency dynamic response model, the state space equation of the system frequency response model is written as:

[0083]

[0084] In the formula: F(x, E(t)) is the comprehensive disturbance of the wind power grid-connected system, including wind speed uncertainty, response speed of traditional synchronous units, external load change and other unknown disturbances that the system may face; E(t) is the external disturbance that the whole system may receive; b0 is the non-zero disturbance compensation coefficient of the real-time estimation value of the system comprehensive disturbance; u = u(t) and y = y(t) are respectively the control variable input and output of the system.

[0085] The variables in the state space equation can be expressed as:

[0086]

[0087] The u(t) is introduced into the linear extended state observation algorithm after being compensated by b0 in real time, and the real-time online connection with the system is established:

[0088]

[0089] The extended observation quantity of F(x, E(t)) is z2:

[0090]

[0091] The nonlinear system containing wind power frequency modulation is linearized by disturbance dynamic compensation.

[0092]

[0093] In order to observe the system disturbance, F(x, E(t)) in the state space equation is state-extended and represented by state variable x2, and the following state space expression is obtained:

[0094]

[0095] In the formula, x1 is Δf sys , and x2 is the extended state variable of system disturbance.

[0096] To achieve accurate and real-time observation of the change of state variable Δf sys and "observation + compensation" of system F(x, E(t)), the state observation mechanism in the linear extended state observation algorithm for suppressing wind power grid fluctuation and the disturbance extension compensation method are designed, and the output equation is:

[0097]

[0098] In the formula, z1 is the observation value of the state variable x1 of the system; e is the deviation between the observation value of the state variable and the actual state of the system. η1 and η2 are the set control coefficients of the linear extended state observation algorithm, and η1 is 2 and η2 is 1.

[0099] According to the system extended state observation design method of the output equation, the disturbance dynamic compensation of the linearized nonlinear system containing wind power frequency regulation is rewritten as:

[0100]

[0101] The step three monitors the error between the system frequency deviation and the target frequency deviation in real time, further adjusts the active power output of the variable speed wind turbine, and realizes the suppression of wind power grid frequency fluctuation, and the specific steps include:

[0102] The influence of disturbance is offset by the linear error state feedback control algorithm, the rotor kinetic energy release of the variable speed wind turbine following the real-time frequency state of the system is improved, the wind power fluctuation is suppressed as much as possible, and x1 tends to Δf sys_ref . The output of the linear error state feedback control algorithm is designed as:

[0103] u0(t)=η3(Δf sys_ref -z1) (14)

[0104] In the formula, η3 is the set control coefficient of the linear error state feedback control algorithm, and η3=1 / 250h 2 , wherein h is the sampling step length, which is determined according to the system control accuracy, Δf sys_ref is the frequency deviation, which is usually 0.

[0105] Combining the linear extended state observation algorithm and the linear error state feedback control algorithm, the final output of the active regulation increment of the wind turbine frequency suppression is:

[0106]

[0107] In the formula, b0 mainly achieves the compensation of system F(x,E(t)), and its setting is strongly related to the system's inertial time constant, that is, b0 can be taken as 1 / (2H sys ).

[0108] The embodiments of the present invention adopt Figure 2 The self-disturbance rejection wind power grid-connected power system frequency fluctuation suppression control method shown is in Figure 3 Simulation analysis was conducted on the four-machine, two-area system with wind power grid connection shown. Figure 4 This paper presents the impact of wind turbine active power output on system frequency variation characteristics under four scenarios: wind turbine control with the present invention, variable gain droop control, traditional fixed gain droop control, and no frequency regulation control, based on a random, continuously varying wind speed of 8.42 m / s at a low wind penetration rate of 25%. Specifically, it compares these scenarios. In the case of no frequency regulation control, due to the decoupling between the wind turbine speed and the system frequency, the active power output of the turbine cannot effectively respond to changes in system frequency. The system mainly relies on traditional synchronous turbines to provide frequency support to the grid and suppress frequency fluctuations. In this case, random wind speed fluctuations will cause significant fluctuations in system frequency and wind turbine active power output. Figure 5 , 6 As shown. The present invention exhibits excellent frequency regulation performance in the embodiments; when the wind turbine uses the present invention, the overfrequency Δf... max With underfrequency Δf max Compared to maximum power point tracking, constant gain, and variable gain control, this reduces costs by 67.26%, 27.73%, and 3.95%, and by 48.70%, 17.78%, and 26.37%, respectively. Furthermore, from... Figure 7 As shown in the schematic diagram of the probability distribution of system frequency deviation, the probability that the steady-state frequency deviation of the present invention is concentrated in the ±0.1Hz range is greater than that of the other three control methods.

[0109] Another embodiment of the present invention provides a frequency fluctuation suppression system for wind power grid-connected power systems with self-disruption capability, comprising: a computer-readable storage medium and a processor;

[0110] The computer-readable storage medium is used to store executable instructions;

[0111] The processor is used to read executable instructions stored in the computer-readable storage medium and execute the self-disruption-resistant wind power grid-connected power system frequency fluctuation suppression method.

[0112] Another embodiment of the present invention provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the aforementioned method for suppressing frequency fluctuations in a wind power grid-connected system with self-disruption capability.

[0113] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0114] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0115] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0117] Finally, it should be noted that the above-mentioned embodiments are merely intended for describing and illustrating, not limiting the technical solutions of the present application. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A method for damping frequency fluctuations in a wind power grid-connected power system with active disturbance rejection, characterized in that, The method comprises the following steps: A frequency dynamic response model of a wind power grid-connected system containing variable-speed wind turbines is established; Based on the frequency dynamic response model of the wind power grid-connected system, a real-time state of a system frequency deviation is observed, a comprehensive disturbance in and outside the system is estimated, and an active power output of the variable-speed wind turbine is adjusted in real time to respond to a change in grid frequency; An error between the system frequency deviation and a target frequency deviation is monitored in real time, the active power output of the variable-speed wind turbine is further adjusted, and wind power grid-connected frequency fluctuation is suppressed; The error between the system frequency deviation and the target frequency deviation is monitored in real time, the active power output of the variable-speed wind turbine is further adjusted, and wind power grid-connected frequency fluctuation is suppressed, and the specific steps comprise: The influence of the disturbance is offset by a linear error state feedback control algorithm, the rotor kinetic energy release of the variable speed wind turbine following system is improved in real-time frequency state, the wind power fluctuation is as much as possible to be suppressed, and the system tends to the frequency deviation Δf with respect to the state variable x1 sys_ref The output of the linear error state feedback control algorithm is designed as: (14)； In the formula: η3 is a set linear error state feedback control algorithm control coefficient, η3 = 1 / 250h 2 Wherein h is a sampling step, the value is determined by system control accuracy, Δf sys_ref The frequency deviation; z1 is the observation value of the system to the state variable x1; In combination with a linear extended state observation algorithm and a linear error state feedback control algorithm, an active regulation increment of the wind turbine during frequency suppression is designed as follows: (15)； wherein K p is the fixed gain coefficient of power droop control for variable speed wind turbines, z2 is the extended observation of F(x, E(t)), F(x, E(t)) is the comprehensive disturbance of the wind power grid-connected system, including wind speed uncertainty, fast and slow response of traditional synchronous units, external load change and other unknown disturbances that the system may face, E(t) is the external disturbance that the entire system may be subjected to, b0 mainly realizes compensation of the system F(x, E(t)), and is strongly related to the setting of the system inertia time constant.

2. The method for suppressing frequency fluctuations of a wind power grid-connected power system with active disturbance rejection according to claim 1, characterized in that: The frequency dynamic response model of the wind power grid-connected system containing variable-speed wind turbines is established, and the specific steps comprise: The rotor side of the variable-speed wind turbine adopts a typical power droop control structure, and the active regulation increment of the wind turbine during frequency suppression and an active power reference value are as follows: (1)； (2)； In the formula: is the fixed gain coefficient for power droop control of variable speed wind turbine; Af sys is the measured frequency of AC system f sys is the frequency deviation from the reference frequency 50 Hz; AP FR is the active output increment of wind turbine; P w is the active power reference value of wind turbine; P MPPT is the active output of wind turbine in maximum power point tracking mode The frequency dynamic response model of the wind power grid-connected system is represented as follows: (3)； where: P TSG is the active power reference value of the conventional synchronous generator unit; P TSG0 is the initial output of the conventional synchronous generator unit; ΔP TSG is the TSG frequency modulation increased power; P dtb is the power disturbance suffered by the system; P dtb0 is the original basic load of the system; ΔP dtb is the basic load sudden increase; H sys is the equivalent inertia time constant of the system; D sys is the equivalent damping coefficient of the system; Under a normal operation state of the system, the active power output of the conventional synchronous unit and the variable-speed wind turbine and the basic load satisfy power balance, that is, (4)； The frequency dynamic response model of the wind power grid-connected system is linearized to obtain (5)； In the formula, D sys = D sys + K p is the equivalent damping coefficient of the system with power droop control for variable speed wind turbines.

3. The method for self-disturbance-immune wind power grid-connected power system frequency fluctuation mitigation according to claim 2, characterized in that: Based on the frequency dynamic response model of the wind power grid-connected system, the real-time state of the system frequency deviation is observed, the comprehensive disturbance in and outside the system is estimated, and the active power output of the variable-speed wind turbine is adjusted in real time to respond to the change in grid frequency, and the specific steps comprise: Real-time accurate estimation of the disturbance and real-time tracking of the system frequency deviation are realized by the linear extended state observation algorithm, the existence and change of the disturbance are perceived, and thus the influence of the disturbance on the frequency modulation process is better offset; let sys =x as a state variable, according to the linearized system frequency dynamic response model, the state space equation of the system frequency response model is written as: (6)； In the formula, F(x, E(t)) is a comprehensive disturbance of the wind power grid-connected system, including wind speed uncertainty, response speed of the conventional synchronous unit, external load change and other unknown disturbances that the system may face; E(t) is an external disturbance that the entire system may receive; b0 is a non-zero disturbance compensation coefficient of a real-time estimation value of the system comprehensive disturbance; u=u(t) and y=y(t) are respectively a control variable input and an output of the system; Each variable in the state space equation is represented as follows: (7)； The u(t) is compensated in real time by b0 and introduced into the linear extended state observation algorithm to establish real-time online connection with the system: (8)； The extended observation quantity of F(x, E(t)) is z2: (9)； The nonlinear system containing wind power frequency regulation is linearized by disturbance dynamic compensation; (10)； In order to observe the system disturbance, the state space equation F(x, E(t)) is extended by a state variable x2, and the following state space expression is obtained: (11)； where: x1 is Δf sys x2 is the extended state variable of system disturbance; To achieve accurate and real-time observation of the state variable Δf sys The state observation mechanism in the linear extended state observation algorithm for smoothing the grid-connected power fluctuation of wind power and the disturbance expansion compensation method are designed, and the output equation is as follows: (12)； In the formula, z1 is an observation value of the system on the state variable x1; e is a deviation of the observation value of the state variable from the actual state of the system, and η1 and η2 are control coefficients of the linear extended state observation algorithm, and η1 is 2 and η2 is 1; According to the system extended state observation design method of the output equation, the linearized nonlinear system containing wind power frequency regulation is rewritten by disturbance dynamic compensation as follows: (13)。 4. The method for self-disturbance-immune wind power grid-connected power system frequency fluctuation mitigation according to claim 1, characterized in that: b0 takes the value of 1 / (2H sys ).

5. The method for self-disturbance-immune wind power grid-connected power system frequency fluctuation mitigation according to claim 1, characterized in that: Frequency deviation Δf sys_ref Has a value of 0.

6. A self-disturbance-immune wind power grid-connected power system frequency fluctuation flattening system, comprising: The computer readable storage medium and the processor; The computer readable storage medium is used for storing executable instructions; The processor is configured to read executable instructions stored in the computer readable storage medium and execute the method for suppressing frequency fluctuation of a wind power grid-connected power system with active disturbance rejection according to any one of claims 1-5. 7.A non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method for suppressing frequency fluctuation of a wind power grid-connected power system with active disturbance rejection according to any one of claims 1-5.

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