Self-adaptive short-time frequency support method for wind turbine generator based on system view angle

Abstract

The invention provides a wind turbine generator self-adaptive short-time frequency support method based on a system view angle, which comprises the following steps: considering the frequency modulation power response speed cooperation of a wind turbine generator and a thermal power generating unit, and establishing a power track model in a frequency support stage of the wind turbine generator; establishing a wind power frequency modulation power peak value calculation method and a wind power frequency modulation power rise time establishment method under a composite working condition based on a load disturbance degree, a wind power permeability level and a thermal power generating unit output level under the constraint of a safe and stable operation domain of a wind power generating unit according to design parameters of a wind power track model in a support stage; and designing an output power model of the wind turbine generator in the frequency support quit stage by adopting a Logistic function. According to the method, the lowest point in the dynamic process of system frequency response can be remarkably improved, the risk of triggering low-frequency load shedding is effectively reduced, and the frequency overshoot phenomenon is inhibited. Meanwhile, in the implementation process of the method, the decreasing amplitude of the rotating speed is small, the time needed for supporting is short, and economic benefits of wind power manufacturers are taken into account while the power grid frequency supporting requirement is met.

Description

Technical Field

[0001] This invention relates to the technical field of wind turbine control, and in particular to an adaptive short-time frequency support method for wind turbines based on a system perspective. Background Technology

[0002] With the advancement of the "carbon peak and carbon neutrality" goals, China's installed wind power capacity has continued to grow rapidly. However, variable-speed wind turbines, represented by doubly-fed induction generators (DFIGs), suffer from isolation effects in their power electronics, making them unable to naturally respond to system frequency changes. Furthermore, these turbines typically operate in maximum power point tracking (MPPT) mode and do not participate in frequency regulation, leading to a significant decrease in inertia levels in power systems with high wind power penetration, posing a severe challenge to system frequency stability. Implementing reasonable control strategies to enable wind turbines to actively regulate frequencies has become an international consensus.

[0003] In recent years, scholars at home and abroad have proposed a variety of wind power frequency regulation control strategies, mainly including overspeed control, pitch control, energy storage-assisted control, and inertia control. Compared with the other three strategies, inertia control has significant economic benefits without reducing daily power generation and without requiring additional hardware modifications, thus it has great application potential. Existing inertia control can be divided into integrated inertia control and preset power trajectory control (PPTC). Integrated inertia control is heavily dependent on the accuracy of system frequency measurement, resulting in a slow response speed. In contrast, PPTC outputs active power according to a preset trajectory after activation, which can accelerate the frequency regulation response speed of wind turbines. The literature [ZHAO T, LIU H, WANGN, et al. An active power control of DFIG-based wind turbine generators for frequency regulation with expected dynamic performance[J]. Applied Energy, 2025, 391: 125948.] proposes a suboptimal curve short-time frequency support strategy, in which the increment of the power curve relative to the maximum power point tracking curve increases with increasing wind speed. Reference [YANG D, KIM J, KANG YC, et al. Temporary frequency support of a DFIG for high wind power penetration[J].IEEE Transactions on Power Systems, 2018, 33(3): 3428-3437.] proposes a short-time frequency support scheme combining step inertia control and torque limiting control. In this scheme, the magnitude of the frequency modulation power is designed based on the rotational speed and wind power penetration rate. Reference [KHESHTI M, LIN S, ZHAO X, et al. Gaussian Distribution-Based Inertial Control of Wind Turbine Generators for Fast Frequency Response in Low Inertia Systems[J].IEEE Transactions on Sustainable Energy, 2022, 13(3): 1641-1653.] uses a Gaussian curve to set the frequency modulation power trajectory and points out that setting the peak frequency modulation power to one-third to one-half of the unbalanced power can significantly improve the lowest frequency point.Reference [ZHOU Y, ZHU D, ZOU X, et al. Adaptive temporary frequency support for DFIG-based wind turbines[J]. IEEE Transactions on Energy Conversion, 2023, 38(3): 1937-1949.] proposes a short-time frequency support strategy based on an upward-opening parabolic trajectory. The peak frequency regulation power of this strategy is linearly adjusted according to the disturbance magnitude and the initial speed. Reference [RASOUL A., MOSTAFAM., TOMISLAV D. et al. A linear inertial response emulation for variable speed wind turbines[J]. IEEE Transactions on Power Systems, 2020, 35(2): 1198-1208.] proposes an improved torque-limiting control strategy, which establishes a proportional relationship between the maximum value of the wind power increment and the output power before the disturbance. The setting of wind power frequency regulation power needs to comprehensively consider factors such as system disturbance, wind power penetration rate and the initial state of the unit. However, existing research still has shortcomings in comprehensively considering these factors. Furthermore, the wind power output trajectory given by existing PPTC strategies typically has a step-like rising edge, neglecting the output coordination between wind turbines and synchronous generators. The literature [SUNM, MIN Y, CHEN L, et al. Optimal auxiliary frequency control of wind turbine generators and coordination with synchronous generators[J]. CSEE Journal of Power and Energy Systems, 2021, 7(1): 78-85.] points out that the energy used by wind turbines for frequency regulation should be released at an appropriate rate. However, how to plan the wind turbine output trajectory to achieve coordination with the synchronous generator response, thereby maximizing the frequency support effect, remains to be explored.

[0004] After the frequency support ends, an improperly designed frequency support exit scheme will cause a secondary frequency drop (SFD) in the system. Reference [Jiang Tao, Qiu Yuchen, Liu Xianchao, et al. Dynamic differentiated timing coordinated control strategy for multiple wind farms supporting grid frequency stability [J]. Automation of Electric Power Systems, 2024, 48(5): 162-173.] proposes a dynamic differentiated timing coordinated control strategy for multiple wind farm groups, and puts the wind farm groups into operation in batches to avoid the problem of secondary frequency drop caused by simultaneous frequency regulation of multiple wind farm groups. Reference [Qiao Ying, Guo Xiaoqian, Lu Zongxiang, et al. Determination method of auxiliary frequency regulation parameters of wind turbines considering secondary frequency drop in the system [J]. Power System Technology, 2020, 44(3): 807-815.] designs a setting scheme for frequency regulation control parameters and exit frequency regulation time, which reduces the degree of secondary frequency drop. References [Shan Yu, Wang Zhen, Zhou Changping, et al. Primary frequency regulation control strategy for wind turbines based on piecewise frequency change rate [J]. Automation of Electric Power Systems, 2022, 46(11): 19-26] and [Tang Yufeng, Yang Ping, Yang Yi. Frequency response control strategy for wind turbines considering frequency double drop [J]. Automation of Electric Power Systems, 2023, 47(9): 166-174.] proposed a time-based linear speed recovery scheme, which alleviated the SFD phenomenon, but the wind turbine speed recovery speed was slow. References [Tao Yukun, Yang Feifei, He Ping, et al. Flexible frequency response strategy for wind turbines considering frequency double drop and speed recovery [J]. Automation of Electric Power Systems, 2024, 48(13): 60-68.] designed a nonlinear speed recovery scheme, which improved the SFD problem and had a faster speed recovery speed. However, improper setting of the attenuation power in this scheme may cause the wind turbine output power to be greater than the MPPT wind power for a long time, thus slowing down the speed convergence to the initial speed.

[0005] Preset power trajectory control is an important technical approach for wind turbines to achieve short-term frequency support. However, from a system perspective, existing designs have the following two shortcomings: first, they lack coordination with the response speed of traditional power sources such as thermal power; second, their peak output is difficult to match the real-time power requirements of the system. Summary of the Invention

[0006] To address the technical problems of existing preset power trajectory control lacking coordination with the response speed of traditional power sources such as thermal power, and its peak output failing to meet the real-time power demand of the system, this invention proposes an adaptive short-time frequency support method for wind turbines based on a system perspective. On the one hand, under the designed ramp output mode, adaptive frequency support can be provided according to actual operating conditions such as load disturbances and wind power penetration, significantly improving the minimum point of the first frequency drop. At the same time, it avoids large frequency oscillations or even frequency overshoot during the frequency regulation process of torque-limiting strategies. On the other hand, the designed frequency support exit strategy effectively alleviates the problem of secondary frequency drop caused by traditional exit strategies. In addition, compared with torque-limiting strategies, the proposed strategy has a smaller speed drop and a shorter support time, meeting the frequency support requirements for the power grid while also taking into account the benefits for wind power manufacturers.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: a system-based adaptive short-time frequency support method for wind turbine generators, comprising:

[0008] Considering the coordination of frequency regulation power response speed between wind turbines and thermal power units, a power trajectory model for the frequency support stage of wind turbines is established.

[0009] For the design parameters of the wind power trajectory model in the support stage, under the constraints of the safe and stable operation domain of wind turbine units, a method for calculating the peak wind power frequency regulation power under composite working conditions and a method for determining the rise time of wind power frequency regulation power are established based on the load disturbance degree, wind power penetration rate and thermal power unit output level.

[0010] A model for the output power of wind turbines in the frequency support exit phase is designed using the Logistic function.

[0011] Preferably, the power trajectory of the wind turbine frequency support stage power trajectory model is curve AB′-C′, and the power trajectory of the frequency support exit stage is curve C′-D′-A, where A is the location of the initial power P0 at the initial time t0 and the initial speed ω0, point B' corresponds to the wind power frequency regulation power peak ΔP0′ and rise time d; point C' is the point on the wind power power trajectory where the wind turbine output power is equal to the initial power P0; and point D' is the lowest power point in the frequency exit stage.

[0012] Preferably, during the frequency support phase, the output electromagnetic power of the wind turbine increases linearly with time to point B' at time t. B′ After a certain time, as the rotor speed decreases, the power output decreases, and the wind turbine's electromagnetic power output is:

[0013]

[0014] In the formula: ΔP0′ is the peak value of wind power frequency regulation; t0 is the initial moment of frequency support; tC′ The frequency support exit time is Δω; the speed change during the rise of wind power is d = t. B′ -t0; P MPPT (ω0), P MPPT (ω min These represent the wind power output in MPPT mode at the initial speed and minimum speed, respectively.

[0015] Based on the rotor kinetic energy released during the rising phase of wind power frequency regulation, the change in rotational speed Δω during the rising phase can be obtained as follows:

[0016]

[0017] For the frequency regulation power reduction segment of wind power, i.e., the arc Linear approximation is used to obtain line segments This, together with the rising segment, constitutes the piecewise linear frequency modulation (LFM) power trajectory of the frequency support phase; using the piecewise LFM power as the system excitation signal, the following relationship is derived at the frequency peak:

[0018]

[0019] Where: h step (t) is the transfer function G( power disturbance-frequency change). S The unit step response of t; p The peak frequency moment; K r For line segments The slope;

[0020] Let the peak frequency time t p The time t is equal to the valley of the system frequency under load power disturbance. n This is to utilize the frequency response peak generated by wind power frequency regulation to compensate for the frequency trough under load disturbance, thereby increasing the frequency to the lowest point of the first drop.

[0021] Preferably, the method for calculating the peak wind power frequency regulation under the combined operating conditions is as follows:

[0022] Let max{ΔP W}=ρΔP0′, then Where ρ is the wind power penetration rate. This is an estimated value for the frequency regulation power of thermal power units;

[0023] Releasing rotor kinetic energy under ultimate torque constraint: P0 + ΔP0′ ≤ 0.9T lim (ω0-Δω); where P0 represents the initial power;

[0024] During frequency support, the rotor speed of the fan should be greater than the minimum speed ω. minThat is, ω-ω min >0, therefore:

[0025]

[0026] Where ω is the rotor speed of the wind turbine.

[0027] Preferably, based on the relationship between system frequency variation and unbalanced power, it can be seen that the system has an active power balance relationship at the frequency trough: ΔP T +ΔP W =-ΔP L +DΔf; where ΔP T For the frequency regulation power of thermal power units, ΔP W Where is the frequency regulation power of the wind turbine, D is the system damping coefficient, and Δf is the frequency change.

[0028] The design rule for peak wind power frequency regulation is max{ΔP} W}=-kP A -ΔP T In the formula, max{ΔP W} represents the peak wind power required for frequency regulation by the system; k is a correction factor greater than 1;

[0029] After being disturbed, the load disturbance amplitude and the rate of change of the initial frequency exhibit the following linear relationship:

[0030] Load disturbance estimate Among them, H SYS R is the system's equivalent inertial time constant. 200 The average frequency change rate after 200ms following the disturbance is ρ, where ρ is the wind power penetration rate.

[0031] Thermal power unit output ΔP at peak wind power frequency regulation T The estimated value of the frequency regulation power of the thermal power unit is obtained by estimation: In the formula: α is the ratio of the frequency regulation power of the thermal power unit to its steady-state frequency regulation power when the wind power frequency regulation power is at its peak; ΔP Tset / P A This represents the change in steady-state output of a thermal power unit under a unit step disturbance of the load.

[0032] Preferably, the equivalent inertial time constant of the system is Where: H i and S N,i Let be the inertial time constant and rated capacity of thermal power unit i, respectively; n be the total number of thermal power units; S W This refers to the total installed capacity of the wind turbine units;

[0033] The transfer function of power disturbance-thermal power unit output change is:

[0034]

[0035] Where, ΔP T (s) Frequency regulation power of thermal power units, ΔP L (s) represents the disturbance power; G1(s) and H(s) are the defined transfer functions;

[0036] According to the final value theorem, the magnitude is P. A Under load step disturbance, the steady-state frequency regulation power of the thermal power unit is:

[0037]

[0038] We can obtain:

[0039] Preferably, the rise time d is coupled with the wind power frequency regulation peak value ΔP0′. Based on the parameter scanning method, two simulation examples are used to study the relationship between the wind power frequency regulation peak value ΔP0′ and the rise time d. The frequency regulation power peak value is positively correlated with the power rise time.

[0040] Preferably, the rise time d of the frequency modulation power is taken as the average of the calculation times corresponding to multiple power peaks within the range of [0.1, 0.4] of the frequency modulation power peak value.

[0041] Preferably, the wind turbine output power model during the frequency support exit phase is as follows:

[0042]

[0043] Where: ΔP C′ The power change is preset for the frequency support exit phase; k1 is the participation factor constructed based on the Logistic function; b is the shape coefficient; P W (ω C′ ) is ω C′ Point wind power; P MPPT (ω) represents the output power of the wind turbine in MPPT mode; t C’ This indicates the time corresponding to point C' when the wind turbine's output power equals its initial power.

[0044] Preferably, the shape factor b is set to 0.3;

[0045] Preset power change ΔP C′ From ΔP C′ =min{x∈X|x>ε2} is determined; where: preset power change ΔP C′ The set of candidate values ​​X = {0.02, 0.03, 0.04, 0.05} has an intermediate coefficient ε² = P. W (ω C′ )-Pm (ω C' ), P W (ω C′ ), P m (ω C' ) represent rotational speed ω C′ The wind power output and captured mechanical power at that time.

[0046] Compared with existing technologies, the advantages of this invention are as follows: First, considering the coordination of frequency regulation power response speeds of wind turbines and thermal power units, a frequency regulation power trajectory model for wind turbines is established. Second, based on the system's active power balance, an adaptive rule for frequency regulation power peak value is constructed, taking into account the influence of load disturbances, wind power penetration rate, and thermal power output, and a constraint function for power peak value is established according to safe and stable operating conditions. Then, to suppress secondary frequency drops and accelerate speed recovery, a Logistic function is used to design the power trajectory for the exit phase. Finally, simulation studies are conducted using MATLAB / Simulink, and the simulation results verify the feasibility and effectiveness of the proposed strategy. This invention can significantly improve the minimum point of the system's frequency response dynamic process, effectively reduce the risk of triggering low-frequency load shedding, and suppress frequency overshoot. Simultaneously, this method results in a small speed drop and a short support time during implementation, meeting the grid frequency support requirements while also considering the economic benefits for wind power manufacturers.

[0047] This invention is proposed based on an in-depth study of the shortcomings of two traditional torque-limiting control strategies. Through theoretical research and simulation, the following conclusions are drawn:

[0048] (1) Frequency regulation power is not always better the higher it is. Traditional torque limiting control does not have the ability to adjust the frequency regulation power according to the actual operating conditions, which leads to large frequency oscillations or even frequency overshoot during the frequency regulation process. The wind turbine frequency regulation power trajectory and amplitude calculation model proposed in this invention has better load disturbance, wind power penetration rate and wind speed adaptive characteristics, significantly improves the minimum point of the first frequency drop and effectively suppresses frequency oscillation.

[0049] (2) Based on the Logistic function and the difference form, this invention designs a wind turbine frequency support withdrawal strategy, which effectively alleviates the problem of secondary frequency drops in the system. Taking into account the improvement capabilities of primary and secondary drops, the strategy proposed in this invention can effectively improve the lowest point of the dynamic process of system frequency response and reduce the possibility of triggering low-frequency load shedding.

[0050] (3) The proposed frequency support strategy has a small speed drop and a short support duration. In other words, the wind turbine has a longer time to operate in MPPT state, thus meeting the frequency support requirements for the power grid while also taking into account the revenue of wind power manufacturers. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the structure of the present invention.

[0053] Figure 2 Here is a system frequency response model for a power system with a high proportion of wind power, where (a) is the system frequency response model and (b) is the power frequency model of the wind turbine.

[0054] Figure 3 The short-time frequency support power trajectory diagram is shown, where (a) is the relationship between power and rotational speed, and (b) is the relationship between power and time.

[0055] Figure 4 This is a schematic diagram of strategy 2.

[0056] Figure 5 The graph shows a comparison of the impact of power increment on the system frequency response under different wind speeds, where (i) represents ρ = 20%, P A =0.05pu, (ii) is ρ=20%, P A =0.1pu, (iii) is ρ=30%, P A =0.05pu, (iv) is ρ=30%, P A =0.1pu.

[0057] Figure 6 This is a schematic diagram illustrating the impact of the initial operating point and the magnitude of the disturbance on the output of the thermal power unit.

[0058] Figure 7 This is a simulation topology diagram of a four-machine, two-zone power system.

[0059] Figure 8 The following is a comparison of simulation results under scenario 1 of the present invention, where (a) is the system frequency, (b) is the wind turbine rotation speed, (c) is the wind turbine output power, and (d) is the total output power of wind and fire.

[0060] Figure 9 The following is a comparison of simulation results under scenario 2 of the present invention, where (a) is the system frequency, (b) is the wind turbine rotation speed, (c) is the wind turbine output power, and (d) is the total output power of wind and fire.

[0061] Figure 10The following is a comparison of simulation results under scenario 3 of the present invention, where (a) is the system frequency, (b) is the wind turbine rotation speed, (c) is the wind turbine output power, and (d) is the total output power of wind and fire.

[0062] Figure 11 The following is a comparison of simulation results under scenario 4 of the present invention, where (a) is the system frequency, (b) is the wind turbine rotation speed, (c) is the wind turbine output power, and (d) is the total output power of wind and fire.

[0063] Figure 12 The following is a comparison of simulation results under scenario 5 of the present invention, where (a) is the system frequency, (b) is the wind turbine rotation speed, and (c) is the wind turbine output power. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] like Figure 1 As shown, an adaptive short-time frequency support method for wind turbines from a system perspective is proposed. This method considers the coordination of frequency regulation power output speeds between wind turbines and thermal power units, and designs the power trajectory of the wind turbines during the frequency support phase. Under the constraints of the wind turbine's safe and stable operation domain, a mathematical model of the peak frequency regulation power is established based on the load disturbance level, wind power penetration rate, and thermal power unit output level. Furthermore, a frequency support exit scheme based on the Logistic function is proposed. Finally, the system frequency characteristics under various control strategies and operating scenarios are compared using the MATLAB / Simnlink platform, verifying the effectiveness of the proposed strategy.

[0066] Mechanical power P captured by wind turbine m As shown in equation (1):

[0067]

[0068] In the formula: ρ a air density; S is the area swept by the wind turbine; v is the wind speed; C p (λ,β) represents the wind energy utilization coefficient; λ is the tip speed ratio; β is the blade pitch angle; S N,W The rated capacity of the wind turbine; coefficients c1 = 0.5176, c2 = 116, c3 = 0.4, c4 = 5, c5 = 21, c6 = 0.0068; λ i This is an intermediate coefficient.

[0069] To achieve efficient utilization of wind energy, wind turbines typically operate in maximum power point tracking (MPPT) mode. In this mode, the electromagnetic power P of the wind turbine... MPPT It can be represented as:

[0070]

[0071] In the formula: k opt C p,opt , λ opt These represent the maximum power point tracking coefficient, the optimal wind energy utilization coefficient, and the optimal tip speed ratio, respectively; ω is the rotor speed of the wind turbine; and R is the blade radius.

[0072] The equation of motion for a wind turbine rotor can be expressed as:

[0073]

[0074] Where: H W P is the inertial time constant of the wind turbine; W The electromagnetic power output by the wind turbine is P. MPPT It is electromagnetic power P w One power output mode, in the strategy of this invention, is that the wind turbine operates in MPPT mode during normal system operation, and the electromagnetic power P output by the wind power is... w =P MPPT .

[0075] Figure 2 A system frequency response (SFR) model incorporating wind turbines and thermal power units is presented. In Figure (a): ΔP L For disturbance power, when representing the power disturbance caused by an increase in load, ΔP L <0; ΔP T For the frequency regulation power of thermal power units; ΔP W ρ is the frequency regulation power of the wind turbine; H is the wind power penetration rate. SYS D is the system's equivalent inertial time constant; F is the system's damping coefficient; H The power ratio of the high-pressure cylinder in a thermal power unit; T R T is the reheat time constant of the thermal power unit; G is the inertial time constant of the speed governor; 1 / R is the droop coefficient; s is the Laplace operator.

[0076] Figure 2 Medium power disturbance-frequency change transfer function G( S )for:

[0077]

[0078] Where: power disturbance ΔP(S )represent Figure 1 Medium disturbance power ΔP L Or the frequency regulation power ΔP of the wind turbine W Δf( S () represents the frequency change.

[0079] Considering the step-like system power disturbance ΔP(t)=P A u(t), P A Let u(t) be the disturbance amplitude, and u(t) be the unit step function. Then:

[0080]

[0081] In the formula: d0, d1, d2, e0, e1, e2, e3 are intermediate variables, and

[0082]

[0083] The actual frequency response of the system is obtained by performing a partial fractional expansion of equation (5) using Cardano's formula and applying the inverse Laplace transform:

[0084]

[0085] In the formula: f1, f2, f3, δ, ζ, η, b1, b2, b3, Ω, x,A m These are intermediate variables, and the specific definitions of each parameter are as follows:

[0086]

[0087] It is worth noting that, given the shortcomings of the SFR model based on the low-order thermal power unit model in terms of the accuracy of dynamic reproduction of system frequency and the rationality of the identified parameters, the thermal power unit of this invention adopts a second-order model that considers the dynamics of the governor. That is, the time-domain analytical solution of the system frequency response given by equation (6) corresponds to the third-order SFR model.

[0088] Figure 3 Strategy 1 shown is a torque-limited short-time frequency support strategy. During normal operation of the wind turbine, the MPPT mode is used, and the power before disturbance P0 = P MPPT (ω0); After the disturbance occurs, the short-time frequency support strategy for limiting torque is triggered to increase the electromagnetic power to the torque limit power P at the instant. Tlim (ω0) = P0 + ΔP0, where the power increment ΔP0 is determined by the initial rotational speed ω0 at the trigger moment, i.e., the wind speed. During the frequency support phase, the electromagnetic power is greater than the mechanical power, causing the wind turbine rotor speed to decrease, thus providing frequency support by releasing rotor kinetic energy. For example... Figure 3As shown by line segment BC in (a), the output electromagnetic power of the wind turbine decreases as the rotor speed decreases during this stage. The relationship between the output electromagnetic power of the wind turbine and the rotor speed can be expressed as:

[0089]

[0090] Where: K P-ω ω is the slope of electromagnetic power with respect to rotational speed. min Minimum rotational speed; T lim For the limiting torque, we take 1.17 pu in this paper. MPPT (ω min ) represents the minimum rotational speed ω min MPPT mode output wind power; rotational speed ω A =ω0; ω C The rotational speed at which the wind power output equals the pre-disturbance power output under the traditional strategy; P Tlim (ω0) represents the torque limit power at the initial speed ω0.

[0091] The literature [Gu W, Chen Z, Li Q, et al. Torque Limit-based Inertial Control Method Based on Delayed Support for Primary Frequency Control of Wind Turbines[J]. Journal of Modern Power Systems and Clean Energy, 2024, 12(2): 561-570.] proposes an improved torque-limiting control strategy based on strategy 1 by introducing the wind turbine response delay. Figure 3 Strategy 2, its basic principle is as shown in equation (8) and Figure 4 According to the superposition principle of linear systems, the actual frequency response Δf(t) of the system can be regarded as the frequency component Δf caused only by load disturbance. L (t) and the frequency component Δf caused solely by wind power frequency regulation W (t) is the result of superposition.

[0092] Δf(t)=Δf L (t)+Δf W (t) (8)

[0093] Figure 4 middle Provide frequency support response delay time for wind turbine units; This refers to the time required for the frequency of the wind turbine to rise to its peak value under the action of frequency regulation power. This is the time required for the frequency to drop to its lowest value under load power disturbance. Figure 4It can be seen that, This strategy delays the start time of wind turbine frequency regulation, so that the peak frequency under wind power regulation arrives at the same time as the trough frequency under load power disturbance, thereby improving the lowest frequency point under load disturbance by wind power frequency regulation.

[0094] During the frequency support exit phase, the wind power under both Strategy 1 and Strategy 2 control can be expressed as:

[0095] P W =max{P W (ω C )-ΔP down ,P MPPT (ω)},ω C ≤ω<ω A (9)

[0096] Where: ΔP down P represents the power drop when frequency support is withdrawn. W (ω C ) represents the rotational speed ω C Wind power at that time, P MPPT (ω) corresponds to equation (2), which is the output wind power in MPPT mode.

[0097] The two traditional strategies mentioned above have the following problems:

[0098] (1) Support stage: After the triggering of strategy 1 and strategy 2, the electromagnetic power of the wind turbine suddenly increases. This output mode has a significant suppressive effect on the response intensity of the thermal power unit. In addition, the power increment amplitude is determined only by the rotational speed at the time of triggering and has no coupling relationship with the frequency disturbance, that is, it cannot provide corresponding support according to the actual disturbance level.

[0099] (2) Exit Phase: When frequency support exits, both Strategy 1 and Strategy 2 adopt a scheme of electromagnetic power step reduction. Even if the power step set for this scheme is very small, it will still cause the system frequency to drop twice.

[0100] The adaptive short-time frequency support strategy for wind turbines proposed in this invention includes wind power trajectory design during the frequency support phase and power trajectory design during the support exit phase. The specific implementation steps include:

[0101] Step 1: Consider the coordination of frequency regulation power response speed between wind turbines and thermal power units, and establish a power trajectory model for the frequency support stage of wind turbines.

[0102] Traditional torque-limiting control strategies increase the maximum power output of wind turbines under torque limitations under different operating conditions. However, research in the literature [Zhang Yubo, Yang Songhao, Hao Zhiguo. Frequency support control of grid-connected wind turbines maximizing the minimum frequency point of the power system [J]. Automation of Electric Power Systems, 2024, 48(08):141-151.] shows that the degree of improvement in the minimum frequency point of the system is not positively correlated with the peak power output supported by wind power. Based on this, this invention proposes an adaptive short-time frequency support strategy for optimizing the incremental power output of wind turbines under different wind speed conditions, penetration levels, and power disturbances. The schematic diagram is shown below. Figure 1 As shown. The power trajectory during the frequency support phase of this strategy is as follows. Figure 3 As shown by the curve AB′-C′, the power trajectory during the frequency support exit phase is as follows: Figure 3 The curve C′-D′-A is shown above. Point B′ corresponds to the rise time d; C′ is the point on the wind power trajectory where the output power of the wind turbine is equal to the initial power; D′ is determined by equation (25). When designing the power trajectory, only the trajectory shape is given, and the specific turning point or inflection point position is determined by the trajectory design parameters in the following text. In addition, the specific position of the point will be different under different operating conditions.

[0103] Frequency Support Stage: This invention proposes a rotor kinetic energy release scheme with controlled response speed. After the proposed strategy is triggered, the output electromagnetic power of the wind turbine increases linearly with time to t. B′ At time t B′ After a certain time, the power decreases as the rotor speed decreases. The expression for the output electromagnetic power of the wind turbine during this stage is:

[0104]

[0105] In the formula: ΔP0′ is the peak value of wind power frequency regulation; t0 is the start time of frequency support; t C′ Let d = t. This represents the moment when frequency support exits (the moment when wind power equals the initial power); Δω represents the change in rotational speed during the rising phase of wind power frequency regulation. B′ If -t0, then d is the rise time of wind power frequency regulation. MPPT (ω0), P MPPT (ω min The values ​​represent the output wind power in MPPT mode at the initial speed and minimum speed, respectively.

[0106] Based on the rotor kinetic energy released during the rising phase of wind power frequency regulation, the formula for calculating the speed change Δω during the rising phase is as follows:

[0107]

[0108] For the wind power frequency regulation power reduction phase ( Figure 3 (b) middle arc Perform linear approximation ( Figure 3 (b) midline segment This, together with the rising segment, constitutes the piecewise linear frequency modulation (LFM) power trajectory of the frequency support phase. This piecewise LFM power is then used as... Figure 2 The excitation signal of the system shown can be used to deduce the following relationship at the frequency peak:

[0109]

[0110] Where: h step (t) represents the unit step response of the transfer function G(S), h step (t) can be obtained by dividing the disturbance amplitude P by equation (6). A Find; t p The peak frequency moment; K r For line segments The slope of t. Let t p The time t is equal to the valley of the system frequency under load power disturbance. n This is to utilize the frequency response peak generated by wind power frequency regulation to compensate for the frequency trough under load disturbance, thereby increasing the frequency to the lowest point of the first drop.

[0111] Step 2: Based on the design parameters ΔP0′ and d of the wind power trajectory model in the support stage of Step 1, and under the constraints of the safe and stable operation domain of the wind turbine, establish a method for calculating the peak wind power frequency regulation power under composite operating conditions and a method for determining the rise time of wind power frequency regulation power, based on the load disturbance level, wind power penetration level, and thermal power unit output level.

[0112] Figure 5 The effects of different frequency-modulated power peak values ​​on the primary frequency minimum point of the proposed supporting power trajectory under varying wind speeds, wind power penetration rates, and load disturbances are presented. Comparative analysis reveals that when the frequency-modulated power peak value is too small, the primary frequency minimum point is not sufficiently raised, and its trough shape remains concave, similar to the original waveform. However, when the power increment is too large, a bulge appears in the waveform near the original frequency minimum point, causing the new frequency minimum point to shift to a subsequent extreme point. Figure 5 It can be seen that by setting an appropriate peak frequency regulation power, the frequency response curve can exhibit a smooth waveform near the first trough. Compared to a convex waveform, the lowest point of the first frequency trough is the same or similar in a smooth waveform, but the corresponding peak frequency regulation power setting reduces rotor kinetic energy release, thereby helping to reduce rotor kinetic energy demand and shorten the duration of the entire frequency support process. Wind speed, wind power penetration rate, and load disturbance all have their own effects on the peak frequency regulation power. Figure 5A set of curves for different operating conditions is presented. By comparing the different curves under varying conditions of a single factor, it can be concluded that each factor affects the required peak frequency regulation power. Furthermore, among the three factors of wind speed, wind power penetration, and load disturbance, the impact of penetration and load disturbance is significantly greater than that of wind speed, i.e., the impact of the initial operating state of the wind turbine. Therefore, the design of the peak frequency regulation power in the following section will focus on wind power penetration and load disturbance. It should be noted that... Figure 5 It is mainly used to display waveform information near the first frequency drop point, and no corresponding suppression measures are taken for the SFD problem.

[0113] From the relationship between system frequency variation and unbalanced power, it can be seen that the system has the active power balance relationship shown in equation (13) at the frequency trough:

[0114] ΔP T +ΔP W =-ΔP L +DΔf (13)

[0115] Where, ΔP T For the frequency regulation power of thermal power units, ΔP W Let be the frequency regulation power of the wind turbine, D be the system damping coefficient, and Δf be the frequency change.

[0116] Based on equation (13), this invention proposes the wind power frequency regulation power peak design rule shown in equation (14):

[0117] max{ΔP W}=-kP A -ΔP T (14)

[0118] In the formula: max{ΔP W} represents the peak wind power required for system frequency regulation; k is a correction coefficient greater than 1, which is used to compensate for the error introduced by the load disturbance estimation method described later and the power deviation corresponding to the system damping coefficient. In this invention, k is taken as 1.1.

[0119] After the system is disturbed, the load disturbance amplitude and the rate of change of the initial frequency exhibit the following linear relationship:

[0120]

[0121] Since the initial frequency change rate is difficult to measure in actual power grids, this invention uses the average frequency change rate R over 200ms after the disturbance. 200 Therefore, the estimated load disturbance value is approximated. for:

[0122]

[0123] H SYSIt can be calculated using equation (17).

[0124]

[0125] Where: H i and S N,i Let be the inertial time constant and rated capacity of thermal power unit i, respectively; n be the total number of thermal power units; S W This refers to the total installed capacity of wind turbine units.

[0126] Thermal power unit output ΔP at peak wind power frequency regulation T The estimated value of the frequency regulation power of the thermal power unit is obtained by estimating using equation (18):

[0127]

[0128] In the formula: α is the ratio of the frequency regulation power of the thermal power unit to its steady-state frequency regulation power when the wind power frequency regulation power is at its peak; ΔP Tset / P A This represents the change in steady-state output of a thermal power unit under a unit step disturbance of the load. Figure 6 The influence of the initial operating point and disturbance magnitude on the response of the thermal power unit is presented in the graph. For ease of comparison, the response curves at wind speeds of 9.6 m / s and 10.8 m / s (30% permeability, disturbance amplitude of 0.1 pu) are shifted to have the same initial values ​​as the response curve at 9.6 m / s and 20% permeability. Figure 6 The translations are labeled "Translation 1" and "Translation 2" respectively. Figure 6 It can be seen that the initial operating point of the thermal power unit and the comparison value α of the load disturbance magnitude have no effect.

[0129] exist Figure 2 In the equation (19), the transfer function C(s) of power disturbance-power output change of thermal power unit is shown.

[0130]

[0131] Where, ΔP T (s) Frequency regulation power of thermal power units, ΔP L G1(s) represents the disturbance power, and G1(s) and H(s) are the defined transfer functions.

[0132] According to the final value theorem, the magnitude is P. A Under load step disturbance, the steady-state frequency regulation power of the thermal power unit is:

[0133]

[0134] The transfer function C(s) is obtained from equation (19). The time-domain form of the step disturbance and its Laplace transform result are shown in equation (5) and the corresponding formula explanation.

[0135] From equation (20), we can obtain:

[0136]

[0137] Let max{ΔP W}=ρΔP0′,then,

[0138]

[0139] Where ρ is the wind power penetration rate. This is an estimated value for the frequency regulation power of thermal power units.

[0140] To ensure the safe operation of wind turbine units, the proposed strategy releases rotor kinetic energy under the constraint of ultimate torque, namely:

[0141] P0 + ΔP′0 ≤ 0.9T lim (ω0-Δω) (23)

[0142] Where P0 represents the power before the disturbance.

[0143] To avoid the risk of turbine tripping due to excessive wind turbine output, the rotor speed should be greater than the minimum speed ω during frequency support. min That is, ω-ω min If the result is greater than 0, then from equation (12) we get:

[0144]

[0145] ω is the rotor speed of the wind turbine.

[0146] Equations (22) to (24) together constitute the wind power frequency regulation peak calculation model under composite operating conditions, thereby ensuring that the wind turbine can achieve adaptive frequency support under the constraints of safe and stable operation.

[0147] Regarding the design of the rise time d of the wind power frequency regulation in the proposed strategy, it can be seen from the combination of equations (12), (18), and (22) that the rise time d is coupled with the peak value ΔP0′ of the wind power frequency regulation, and its value cannot be determined by calculation in sequence. Furthermore, the disturbance amplitude P... A The magnitude of the frequency valley time t nNo impact. In view of the above coupling, the present invention adopts the parameter scanning method: based on equation (12), relying on simulation examples 1 and 2, the system is scanned within the effective interval of ΔP0′ to analyze the value characteristics of rise time d. The results are summarized in Table 1. Table 1 shows that the peak frequency modulation power is positively correlated with the power rise time. The average rise time has a good approximation of the calculated rise time value within a large test range. Therefore, the frequency modulation power rise time of the strategy proposed in this invention is taken as the average value of the calculated time corresponding to multiple peak frequency modulation power values ​​within the test range [0.1, 0.4], that is, within the value range of ΔP′0 in Table 1.

[0148] Table 1 Relationship between peak frequency modulation power and rise time

[0149]

[0150] In Table 1, ε1| d =1, ε1| d＝11.7 The values ​​represent the percentage errors between the average rise time d (1s and 11.7s) and the calculated value in Examples 1 and 2, respectively. The power increment ΔP0 of strategies 1 and 2 varies with the initial rotational speed ω0. When the initial rotational speed ω0 varies within the range [0.7, 1.2], the peak wind power ΔP0 non-monotonically varies between 0.353 pu and 0.483 pu. Due to the presence of Δω in the proposed strategy, the maximum value of the peak wind power ΔP′0 under the proposed strategy is smaller than ΔP0 under the same initial rotational speed. Therefore, the test range in Table 1 effectively covers the possible value range of ΔP′0.

[0151] Step 3: Design the wind turbine output power model for the frequency support exit stage using the Logistic function.

[0152] Traditional nonlinear speed recovery strategies based on the Logistic function are mathematically modeled as the sum of MPPT power (or overspeed load reduction power) and a decaying power term. Compared to linear recovery strategies, although the nonlinear strategy based on the Logistic function applies a larger unbalanced torque to the wind turbine rotor in the early stage of speed recovery, when the decay rate of the decaying term is reduced to decrease the SFD degree, the electromagnetic power of the wind turbine will be greater than the maximum power tracking electromagnetic power for a long time, thus prolonging the latter half of the speed recovery. To address this, this invention designs a wind turbine output power model for the frequency support exit stage as shown in equation (25).

[0153]

[0154] Where: ΔP C′ The power change is preset for the frequency support exit phase; k1 is the participation factor constructed based on the Logistic function; b is the shape coefficient. P W (ω C′) represents the rotational speed ω at point C'. C′ wind power output; P MPPT (ω) represents the output power of the wind turbine in MPPT mode; t C’ Point C' represents the moment when the wind turbine's output power equals its initial power.

[0155] The appropriate selection of the shape factor b has a decisive impact on the SFD suppression effect and the wind turbine speed recovery speed. Based on multi-scenario simulation experiments, and considering both dynamic response performance and system stability requirements, this invention sets the shape factor b to 0.3. To ensure a smooth transition between the support phase and the support withdrawal phase, a preset power change ΔP is used. C′ Determined by equation (26):

[0156] ΔP C′ =min{x∈X|x>ε2} (26)

[0157] Where: Preset power change ΔP C′ The set of candidate values ​​X = {0.02, 0.03, 0.04, 0.05} has an intermediate coefficient ε² = P. W (ω C′ )-P m (ω C' ), P W (ω C′ ), P m (ω C' ) represent rotational speed ω C′ The wind power output and captured mechanical power at that time.

[0158] To verify the proposed strategy, a simulation model was built in MATLAB / Simulink. The proposed strategy was compared with a torque-limited frequency modulation strategy and a time-delayed torque-limited frequency modulation strategy (labeled "Strategy 1" and "Strategy 2" respectively in the simulation figures below). Two simulation examples and five simulation scenarios were set up. Scenarios 1-4 are based on simulation example 1. Figure 2 The SFR model shown is implemented, and the specific simulation parameters are shown in Table 2; Scenario 5 is implemented based on simulation example 2 (four-machine two-zone simulation model), and the topology is shown in Table 2. Figure 7 As shown. The wind farm, consisting of 400 1.5MW doubly fed wind turbines, is connected to bus 4. The parameters of the wind turbines are shown in Table 3. For the parameters of the synchronous generators and the power grid, please refer to the literature [KUNDUR P. Power system stability and control[M]. New York: McGraw-Hill, 1994.].

[0159] Table 2 Simulation Parameters

[0160]

[0161] Table 3 Wind Turbine Parameters

[0162]

[0163] Note: v Wmin The minimum wind speed required for frequency regulation is 20% of the rated power.

[0164] Scenario 1: In this scenario, the wind speed is 9.6 m / s, the wind power penetration rate is 20%, and the disturbance power ΔP L A step disturbance of 0.1 pu occurs at 70 s. Figure 8 Simulation results for the proposed strategy and two comparative strategies are presented. Figure 8 The primary frequency minimums of Strategy 1, Strategy 2, and the proposed strategy are 49.5005Hz, 49.5321Hz, and 49.5919Hz, respectively, with secondary frequency drops of 0.0068Hz, 0.01Hz, and 0.0015Hz, respectively. This demonstrates that the frequency support and support exit schemes designed in the proposed strategy effectively improve upon the two comparative strategies. Compared to the proposed strategy, although Strategy 1 and Strategy 2 have higher output power, the minimum system frequency of the wind turbine using the proposed strategy is higher than that of the two comparative strategies. This proves that the improvement in the minimum frequency is not simply achieved by increasing the frequency regulation power of the wind turbine. Furthermore, due to the "over-support" of the two comparative strategies, the system frequency exhibits significant oscillations near the trough of the primary frequency drop, while the waveform of the proposed strategy is flatter at this position. Figure 8 As can be seen from (d), the total frequency regulation output of the system power supply under the strategy proposed in this invention can quickly track the system disturbance demand while exhibiting smaller fluctuations in the power response transient process, thus providing a guarantee for reducing the oscillation at the bottom of the system frequency curve. Furthermore, from Figure 8 As shown in (b), the proposed strategy achieves good frequency support while utilizing less rotor kinetic energy and exhibiting a faster speed recovery. Rapid recovery of the initial operating point facilitates the wind turbine's response to subsequent frequency disturbances and also improves the economics of the wind farm.

[0165] Scenario 2: The wind power penetration rate in Scenario 1 is increased to 30%, while other conditions remain unchanged. Simulation results are shown below. Figure 9As shown. In this scenario, compared with scenario 1, due to the increase in wind power penetration, the wind turbine reduces the peak frequency regulation power according to the proposed peak frequency regulation power design rule (Equation (22)). Although the frequency regulation power is reduced, the proposed strategy still achieves the maximum improvement of the minimum primary frequency of the system among the three strategies. The minimum primary frequency of strategy 1, strategy 2 and the proposed strategy are 49.3963Hz, 49.4365Hz and 49.5634Hz, respectively. Due to the increase in wind power penetration, the frequency oscillation problem is more serious in the first frequency drop trough stage of the system under the control of strategy 1 and strategy 2. Due to the overcompensation of the system power deficit by wind power output, strategy 1 has a frequency overshoot problem, with the maximum frequency reaching 50.1314Hz. The frequency second drop of strategy 1, strategy 2 and the proposed strategy are 0.0149Hz, 0.0185Hz and 0.0107Hz, respectively.

[0166] Scenario 3: The wind speed in Scenario 2 is increased to 10.8 m / s, while other conditions remain unchanged. The simulation results are as follows: Figure 10 As shown, the minimum primary frequency points of Strategy 1, Strategy 2, and the proposed strategy are 49.4834Hz, 49.4981Hz, and 49.5781Hz, respectively. According to the frequency modulation power peak design rule of the proposed strategy, the peak frequency modulation power in this scenario is the same as that in Scenario 2. Under this parameter value, the proposed strategy still effectively improves the minimum primary frequency point of the system and has a significant advantage over the two comparative strategies. This also verifies the rationality of the proposed adaptive rule for peak frequency modulation power not considering the influence of wind speed. Similar to Scenario 2, Strategy 1 still has the problem of frequency overshoot, but the maximum frequency (50.0954Hz) is smaller than that in Scenario 2. This is because the maximum frequency modulation power in torque-limited control has the characteristic of nonlinear change with the initial speed. The secondary frequency drop of Strategy 1, Strategy 2, and the proposed strategy are 0.0697Hz, 0.0705Hz, and 0.021Hz, respectively.

[0167] Scenario 4: Reduce the load disturbance in Scenario 2 from 0.1 pu to 0.05 pu, while keeping other conditions unchanged. The simulation results are as follows. Figure 11 As shown, the peak frequency modulation power of the proposed strategy decreases as the disturbance amplitude decreases in this scenario. The lowest primary frequency points of Strategy 1, Strategy 2, and the proposed strategy are 49.6121Hz, 49.6259Hz, and 49.7903Hz, respectively. Figure 11(a) indicates that frequency overshoot occurred during the frequency adjustment process of both comparison strategies in this scenario. The maximum frequencies of Strategy 1 and Strategy 2 were 50.4674 Hz and 50.4254 Hz, respectively. The secondary frequency drops of Strategy 1, Strategy 2, and the proposed strategy were 0.0179 Hz, 0.0194 Hz, and 0.0201 Hz, respectively. From the perspective of system frequency safety, the minimum value of the system frequency response is a key indicator for setting low-frequency load shedding. Combining the frequency curves of scenarios 1-4, it can be seen that, with the cooperation of the proposed frequency support and support exit strategies, the minimum point of the dynamic process of the system frequency response in each scenario is significantly improved compared to the two comparison strategies under the action of the proposed strategy. Furthermore, the frequency waveform of the proposed strategy is the flattest among the three strategies, without serious frequency oscillations or frequency overshoot.

[0168] Scenario 5: In this scenario, the wind power penetration rate is 19.8% and the wind speed is 9.6 m / s. At t = 30 s, a 196 MW load power step disturbance occurs at node 7. The simulation results are as follows. Figure 12 As shown. By Figure 12 As shown in (a), strategy 1 again exhibits the frequency overshoot problem. Similar to scenarios 1-4, the proposed strategy has the lowest frequency modulation power and the least rotor kinetic energy consumption among the three strategies. However, the lowest point of the system frequency in the frequency response dynamic process is the highest among the three strategies, and no obvious frequency double drop problem occurs.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system-based adaptive short-time frequency support method for wind turbine generators, characterized in that, include: Considering the coordination of frequency regulation power response speed between wind turbines and thermal power units, a power trajectory model for the frequency support stage of wind turbines is established. For the design parameters of the wind power trajectory model in the support stage, under the constraints of the safe and stable operation domain of wind turbine units, a method for calculating the peak wind power frequency regulation power under composite working conditions and a method for determining the rise time of wind power frequency regulation power are established based on the load disturbance degree, wind power penetration rate and thermal power unit output level. A model for the output power of wind turbines in the frequency support exit phase is designed using the Logistic function.

2. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 1, characterized in that, The power trajectory of the wind turbine frequency support stage power trajectory model is a curve. The power trajectory during the frequency support exit phase is a curve. Where A is the initial time. Initial speed Initial power at time Location, point B', and wind power frequency regulation peak value. Corresponding to the rise time d; point C' is where the wind turbine output power on the wind power trajectory equals the initial power. Point D' is the point where the power is lowest during the frequency exit phase.

3. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 2, characterized in that, During the frequency support phase, the output electromagnetic power of the wind turbine increases linearly with time to point B'. After a certain time, as the rotor speed decreases, the power output decreases, and the wind turbine's electromagnetic power output is: ； In the formula: This represents the peak value of the wind power frequency regulation power. The initial moment supported by the frequency; To support the exit time of frequency; The change in rotational speed during the rise phase of wind power frequency regulation; the rise time of wind power frequency regulation. ; , The output wind power in MPPT mode at the initial speed and minimum speed are respectively; Based on the rotor kinetic energy released during the rising phase of wind power frequency regulation, the change in rotational speed during the rising phase can be obtained. for: ； For the frequency regulation power reduction segment of wind power, i.e., the arc Linear approximation is used to obtain line segments This, together with the rising segment, constitutes the piecewise linear frequency modulation power trajectory of the frequency support phase; using the piecewise linear frequency modulation power as the system excitation signal, the following relationship is derived at the frequency peak: ； In the formula: The transfer function of power perturbation-frequency variation The unit step response; This represents the peak frequency. For line segments The slope; Let the frequency peak time Equal to the time of the system frequency trough under load power disturbance This is to utilize the frequency response peak generated by wind power frequency regulation to compensate for the frequency trough under load disturbance, thereby increasing the frequency to the lowest point of the first drop.

4. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 3, characterized in that, The method for calculating the peak wind power frequency regulation power under the combined operating conditions is as follows: make ,but ;in, For wind power penetration rate, This is an estimated value for the frequency regulation power of thermal power units; Releasing rotor kinetic energy under ultimate torque constraint: ;in, Indicates the initial power; During frequency support, the rotor speed of the fan should be greater than the minimum speed. ,Right now ,have to: ； in, This refers to the rotor speed of the wind turbine.

5. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 3, characterized in that, The relationship between system frequency variation and unbalanced power shows that the system has an active power balance at frequency troughs: ;in, For the frequency regulation power of thermal power units, For wind turbine frequency regulation power, The system damping coefficient is... It is the change in frequency; The design rules for wind power frequency regulation peak power are as follows In the formula, This represents the peak value of the wind power frequency regulation required by the system. A correction factor greater than 1; After being disturbed, the load disturbance amplitude and the rate of change of the initial frequency exhibit the following linear relationship: ; Load disturbance estimate ;in, The system's equivalent inertial time constant. The average frequency change rate over 200 ms after the disturbance. Wind power penetration rate; Thermal power unit output at peak wind power frequency regulation The estimated value of the frequency regulation power of the thermal power unit is obtained by estimation: In the formula: The ratio of the frequency regulation power of a thermal power unit to its steady-state frequency regulation power when the wind power frequency regulation power is at its peak. This represents the change in steady-state output of a thermal power unit under a unit step disturbance of the load.

6. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 5, characterized in that, The equivalent inertial time constant of the system is In the formula: and thermal power units The inertial time constant and rated capacity; This represents the total number of thermal power units. This refers to the total installed capacity of the wind turbine units; The transfer function of power disturbance-thermal power unit output change is: ； in, Frequency regulation power of thermal power units The disturbance power; , The transfer function is defined. By the final value theorem, the magnitude is Under load step disturbance, the steady-state frequency regulation power of the thermal power unit is: ； We can obtain: .

7. The adaptive short-time frequency support method for wind turbines based on a system perspective according to any one of claims 3-6, characterized in that, The rise time Peak frequency regulation power of wind power Coupling, based on the parameter scanning method, uses two simulation examples to study the peak frequency regulation power of wind power. With rise time The relationship between the values ​​of frequency modulation power and power rise time was studied, and the peak power of frequency modulation power was positively correlated with the rise time of power.

8. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 7, characterized in that, Rise time of FM power Take the range of peak frequency modulation power The average calculation time corresponding to multiple power peaks.

9. The adaptive short-time frequency support method for wind turbines based on a system perspective according to any one of claims 3-6, characterized in that, The wind turbine output power model for the frequency support exit phase is as follows: ； In the formula: Preset power change amount for frequency support exit phase; These are the participation factors constructed based on the Logistic function; The shape factor; for Point wind power output; This refers to the output power of the wind turbine in MPPT mode; t C’ This indicates the time corresponding to point C' when the wind turbine's output power equals its initial power.

10. The adaptive short-time frequency support method for wind turbines based on a system perspective as described in claim 9, characterized in that, The shape factor Set to 0.3; Preset power change Depend on Determine; where: preset power change The set of alternative values Intermediate coefficient , , These represent rotational speeds. The wind power output and captured mechanical power at that time.

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