Wind power plant frequency coordination control method considering multi-state-quantity coupling constraint

Abstract

The invention relates to the field of power system protection and control, in particular to a wind power plant frequency coordination control method considering multi-state-quantity coupling constraint. The method comprises the steps of collecting power grid frequency in real time, and starting control when system frequency deviation exceeds a dead zone; evaluating the maximum power supporting capability of the doubly-fed wind turbine generator by utilizing a prediction model of the rotor speed, the pitch angle and the rotor current of the doubly-fed wind turbine generator and an optimization model taking the maximum active power of the doubly-fed wind turbine generator as a target; and calculating the contribution degree of the doubly-fed wind turbine generator according to the maximum active power of each wind turbine generator in the wind power plant, and further determining a power control constant value and implementing control. The method can accurately evaluate the power supporting capability of the doubly-fed wind turbine generator under the coupling constraint of the rotating speed, the pitch angle and the rotor current. The active power output is adjusted according to the contribution degree of each unit in the wind power plant, so that the rotating speed out-of-limit of the units in a low-wind-speed area can be avoided, the power supporting capacity of the doubly-fed wind turbine generator is fully played, and the frequency characteristic of the system is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of power system protection and control, and in particular to a wind farm frequency coordination control method considering multi-state quantity coupling constraints. Background Art

[0002] In response to the energy crisis, the penetration rate of wind power has continued to increase in recent years. Large-scale wind power grid connection has reduced the inertia level of the power system, and the system's anti-interference ability has continued to decline. Doubly-fed wind turbines are one of the mainstream models of wind power generation, with the advantages of high controllability, high wind energy utilization, and strong reliability. Doubly-fed wind turbines can improve the system frequency characteristics by quickly adjusting the active power output when unbalanced power appears in the power system. However, wind farms are usually composed of dozens or even hundreds of doubly-fed wind turbines. There are differences in the operating conditions of doubly-fed wind turbines in wind farms, resulting in different power support capabilities of doubly-fed wind turbines in wind farms, making the coordination of doubly-fed wind turbines in wind farms very difficult. Frequency control of high-proportion wind power power systems faces severe challenges.

[0003] At present, the integrated inertia control of doubly-fed wind turbines and the distribution of wind farm power control constants can be used to coordinate the participation of doubly-fed wind turbines in grid frequency control. Integrated inertia control simulates the inertia response and droop characteristics of synchronous machines, and changes the rotor rotation kinetic energy of doubly-fed wind turbines according to system frequency changes to provide additional power support for the grid. Traditional integrated inertia control uses fixed control parameters, which cannot take into account the differences in power support capabilities of different doubly-fed wind turbines in the wind farm, which may cause some doubly-fed wind turbines to reach speed limits and exit frequency control. Therefore, the idea of ​​adjusting the integrated inertia control parameters in real time according to the power support capabilities of doubly-fed wind turbines has attracted attention. Researchers use dynamic droop control to calculate the power tracking operating parameters of doubly-fed wind turbines. Some studies have proposed a method for calculating the droop coefficient without considering wind speed. Some studies have also proposed a method for setting control parameters for integrated inertia control that considers the frequency regulation energy of the unit. Researchers have also proposed an integrated inertia control method based on time-varying parameters. Wind farms often use average distribution or weight distribution methods to determine the power control constants of each doubly-fed wind turbine according to the grid frequency control requirements. However, the average distribution method sets the power control constant according to the unit capacity, ignoring the differences in the power support capabilities of the doubly-fed wind turbine units. The weight distribution method mostly considers the differences in the power support capabilities of doubly-fed wind turbine units from the perspectives of wind speed, rotation speed, etc. Some studies have considered the impact of wind speed fluctuations and proposed a wind power cluster frequency control method based on random hierarchical distributed model predictive control. Researchers proposed hierarchical optimal power control to reduce the speed differences and energy losses of doubly-fed wind turbines. Considering the impact of rotor speed and converter capacity on the power support capability of the unit, researchers proposed a wind farm frequency coordination control method based on margin factors. The comprehensive inertia control based on time-varying control parameters and the wind farm frequency control based on the weight distribution method take into account the differences in the power support capabilities of the units, but their control effects are determined by the accuracy of the power support capability assessment.

[0004] When the doubly-fed wind turbine provides power support, the rotor speed gradually decreases. If the rotor speed decreases to the minimum speed of the doubly-fed wind turbine, the doubly-fed wind turbine must exit frequency control and restore the power to the initial power to avoid the doubly-fed wind turbine from exiting operation. Therefore, the power support capacity of the doubly-fed wind turbine is limited by the rotor speed. At the same time, when the pitch angle is not zero, the speed change triggers the wind turbine pitch angle control, changing the pitch angle to increase the mechanical power. The change in mechanical power and the release of the rotational kinetic energy of the rotor simultaneously cause the change in the active power of the doubly-fed wind turbine. Therefore, the power support capacity of the doubly-fed wind turbine is also closely related to the pitch angle. In addition, the change in rotor speed causes the rotor induced electromotive force to change, changing the magnitude of the rotor current. In order to avoid damaging the rotor-side converter, there is a small upper limit on the rotor current. The speed change may cause the rotor current to be limited, limiting the output power of the doubly-fed wind turbine, thereby affecting the power support capacity of the doubly-fed wind turbine. Therefore, the power support capacity of the doubly-fed wind turbine is constrained by the coupling of the rotor speed, pitch angle and rotor current. Existing studies have ignored the mechanical power changes caused by pitch angle changes and the rotor current changes caused by speed changes, which may cause errors in the evaluation of the power support capacity of the doubly fed wind turbine. If the evaluation result of the power support capacity of the doubly fed wind turbine is too small, the power support capacity of the wind farm cannot be fully utilized; if the evaluation result is too large, the speed of the doubly fed wind turbine reaches the minimum speed and exits the frequency control, or the rotor current is limited and it is difficult to provide sufficient support, which deteriorates the system frequency.

[0005] In summary, considering the coupling constraints of multiple state quantities on the power support capacity of doubly-fed wind turbines, a wind farm frequency coordination control method based on the power support capacity of the unit is proposed to reduce the system frequency deviation caused by unbalanced power in the power grid, which is an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0006] In view of the deficiencies of the above-mentioned prior art, the present invention provides a wind farm frequency coordination control method considering multi-state quantity coupling constraints, which can solve the problem of unit frequency control exit caused by differences in the power support capacity of doubly-fed wind turbines in the prior art. By accurately characterizing and fully utilizing the power support capacity of the doubly-fed wind farm, the doubly-fed wind turbines are controlled after power disturbances occur in the power grid, which can effectively suppress the system frequency deviation caused by unbalanced power in the power grid.

[0007] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0008] A wind farm frequency coordination control method considering multi-state quantity coupling constraints comprises the following steps:

[0009] S101, collect the grid frequency in real time, and start control when the frequency deviation exceeds the dead zone;

[0010] S102, evaluating the maximum power support capacity of each doubly-fed wind turbine in the wind farm according to the prediction model of the rotor speed, pitch angle and rotor current and the optimization model with the goal of maximizing the active power of the doubly-fed wind turbine;

[0011] S103, calculating the contribution of each doubly-fed wind turbine generator set in the wind farm according to the maximum power support capacity of the doubly-fed wind turbine generator set;

[0012] S104, calculating the power control constant of the doubly-fed wind turbine generator set according to the frequency of the wind farm grid connection point and the contribution of the doubly-fed wind turbine generator set, and implementing control.

[0013] Preferably, in step S102, the prediction model of the rotor speed is established by the following method:

[0014] According to the rotor speed of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent damping of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a first speed parameter at the current moment is obtained;

[0015] According to the wind turbine speed of the doubly-fed wind turbine generator set at the previous moment and the ratio of the electromagnetic power of the doubly-fed wind turbine generator set to the rotational inertia of the induction motor corresponding to the control sampling interval, a second speed parameter at the current moment is obtained;

[0016] According to the angular displacement of the transmission shaft system of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent damping of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a third speed parameter at the current moment is obtained;

[0017] According to the angular displacement of the transmission shaft system of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent stiffness of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a fourth speed parameter at the current moment is obtained;

[0018] The rotor speed of the doubly-fed wind turbine generator set at the current moment is obtained according to the first speed parameter, the second speed parameter, the third speed parameter and the fourth speed parameter at the current moment.

[0019] Preferably, in step S102, the prediction model of the pitch angle is established by the following method:

[0020] According to the control adjustment variable of the pitch angle of the doubly-fed wind turbine generator set at the previous moment and the proportional relationship between the control sampling interval and the time constant of the pitch angle control, the first pitch angle parameter at the current moment is obtained;

[0021] According to the rotor speed of the doubly-fed wind turbine at the current moment and the ratio of the proportional coefficient of the PAC to the time constant of the pitch angle control, the second pitch angle parameter at the current moment is obtained;

[0022] According to the rotor speed of the doubly-fed wind turbine at the previous moment, as well as the control sampling interval, the proportional coefficient of the PAC, the integral coefficient, and the time constant of the pitch angle control, the third pitch angle parameter at the current moment is obtained;

[0023] According to the reference value of the rotor speed of the doubly-fed wind turbine and the ratio of the integral coefficient of the PAC to the time constant of the pitch angle control at the control sampling interval, the fourth pitch angle parameter at the current moment is obtained;

[0024] The pitch angle of the doubly-fed wind turbine generator set at the current moment is obtained according to the first pitch angle parameter, the second pitch angle parameter, the third pitch angle parameter, the fourth pitch angle parameter at the current moment and the pitch angle of the doubly-fed wind turbine generator set at the previous moment.

[0025] Preferably, in step S102, the prediction model of the rotor current is established by the following method:

[0026] According to the rotor current d-axis component of the doubly-fed wind turbine generator set at the previous moment, the control sampling interval, the rotor resistance, the rotor inductance, and the leakage magnetic coefficient, the first d-axis parameter at the current moment is obtained;

[0027] According to the d-axis component of the rotor voltage reference value, the rotor inductance, the leakage magnetic coefficient and the control sampling interval of the doubly-fed wind turbine generator set, the second d-axis parameter at the current moment is obtained;

[0028] According to the slip angular velocity, the d-axis component of the rotor current and the control sampling interval of the doubly-fed wind turbine generator set at the previous moment, the third d-axis parameter at the current moment is obtained;

[0029] According to the q-axis component of the rotor current of the doubly-fed wind turbine generator set at the previous moment, the control sampling interval, the rotor resistance, the rotor inductance, and the leakage magnetic coefficient, the first q-axis parameter at the current moment is obtained;

[0030] According to the q-axis component of the rotor voltage reference value, the rotor inductance, the leakage magnetic coefficient and the control sampling interval of the doubly-fed wind turbine generator set, the second q-axis parameter at the current moment is obtained;

[0031] According to the slip angular velocity, the q-axis component of the rotor current and the control sampling interval of the doubly-fed wind turbine generator set at the previous moment, the third q-axis parameter at the current moment is obtained;

[0032] According to the three d-axis parameters and three q-axis parameters corresponding to the current moment, the rotor current prediction result of the doubly-fed wind turbine generator set at the current moment is calculated.

[0033] Preferably, in step S102, the optimization model is established in the following manner:

[0034] The active power of the wind farm under the constraints of the rotor current and the rotor speed at each moment in the optimization time domain is sorted in descending order, and the first parameter of the maximum value of the active power of the wind farm under the constraints of the rotor current and the rotor speed in the optimization time domain is obtained;

[0035] The active power of the wind farm under the constraints of the rotor speed and pitch angle at each moment in the optimization time domain is sorted in descending order, and the second parameter of the maximum active power of the wind farm under the constraints of the rotor speed and pitch angle in the optimization time domain is obtained;

[0036] A smaller active power value is selected from the first parameter of the maximum active power value and the second parameter of the maximum active power value as the maximum active power value of the double-fed wind turbine generator set after optimization.

[0037] Preferably, in step S103, the maximum power support capability of the doubly-fed wind turbine generator set is determined by the following method:

[0038] S301, setting the optimized time domain T p , and according to the initial values ​​of the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine at time k, the rotor speed, pitch angle and rotor current prediction model is used to calculate the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine at time k+1, where time k is the time of starting control;

[0039] S302, calculating the active power of the doubly-fed wind turbine generator set at time k+1 using an optimization model according to the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine generator set at time k+1;

[0040] S303, iteratively calculate k+T using the prediction model and optimization model p The rotor speed, pitch angle, rotor current and active power of the doubly fed wind turbine at each moment are optimized, and the active power calculation results of the doubly fed wind turbine in the time domain are traversed and optimized, and the maximum value of the active power of the doubly fed wind turbine that meets the constraints is determined as the maximum power support capacity.

[0041] Preferably, in step S303, the constraint conditions include:

[0042] At the current moment, the rotor current of each doubly-fed wind turbine set is less than or equal to the maximum rotor current value; at the current moment, the rotor speed of each doubly-fed wind turbine set is less than or equal to the maximum allowable rotor speed value and greater than or equal to the minimum allowable rotor speed value; at the current moment, the pitch angle of each doubly-fed wind turbine set is less than or equal to the maximum allowable pitch angle value and greater than 0; at the current moment, the pitch angle deviation value of each doubly-fed wind turbine set is less than or equal to the maximum pitch angle deviation value and greater than or equal to the minimum pitch angle deviation value; the pitch angle deviation value of each doubly-fed wind turbine set at the current moment is the difference in pitch angle between the doubly-fed wind turbine set at the current moment and the previous moment.

[0043] Preferably, in step S104, the contribution of each doubly-fed wind turbine generator set is calculated by the following method:

[0044] According to the ratio of the maximum power support capacity of each wind turbine set to the sum of the maximum power support capacity of all wind turbine sets in the wind farm, the contribution of each doubly-fed wind turbine set is obtained.

[0045] Preferably, in step S104, the power control constant of each doubly-fed wind turbine generator set is calculated according to the following method:

[0046] According to the differential of the droop coefficient and the frequency deviation of each doubly-fed wind turbine generator set in the wind farm, a first control constant of each doubly-fed wind turbine generator set in the wind farm is obtained;

[0047] According to the product of the inertia coefficient of each doubly-fed wind turbine generator set in the wind farm and the frequency deviation, a second control constant of each doubly-fed wind turbine generator set in the wind farm is obtained;

[0048] Obtaining compensation power of the doubly-fed wind farm according to the sum of the first control constant and the second control constant of all doubly-fed wind turbines in the wind farm;

[0049] According to the product of the mechanical power and the control parameter of each doubly-fed wind turbine in the wind farm and the compensation power of the doubly-fed wind turbine in the wind farm, the power control constant of each doubly-fed wind turbine is obtained.

[0050] The present invention provides a wind farm frequency coordination control method considering multi-state quantity coupling constraints, which can fully utilize the power support capacity of the wind farm and effectively suppress the system frequency deviation caused by unbalanced power of the power grid by accurately describing the power support capacity of the doubly-fed wind farm and controlling the doubly-fed wind turbine after the power disturbance occurs in the power grid. Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. The prior art uses comprehensive inertia control to enable the wind farm to participate in the system frequency control. However, the comprehensive inertia control based on fixed control parameters cannot take into account the differences in the power support capabilities of different doubly-fed wind turbines in the wind farm, which may cause the speed of some doubly-fed wind turbines to reach the limit and exit the frequency control. The comprehensive inertia control based on dynamic control parameters only focuses on the impact of single variables such as wind speed and speed on the power support capability of the doubly-fed wind turbine, and ignores the coupling constraints of speed, pitch angle and rotor current on the power support capability of the doubly-fed wind turbine, resulting in errors in the evaluation of the power support capability of the doubly-fed wind turbine. The present invention accurately evaluates the power support capability of the doubly-fed wind turbine under the coupling constraints of speed, pitch angle and rotor current, and proposes a frequency coordination control method for doubly-fed wind farms based on contribution, thereby maximizing the utilization of the power support capability of the doubly-fed wind farm and effectively improving the system frequency characteristics.

[0052] 2. The existing technology adopts the wind farm frequency control based on the weight distribution method, and its weight coefficient is mostly set according to the wind speed or rotation speed, ignoring the coupling effect of the rotation speed, pitch angle and rotor current on the weight coefficient of the doubly fed wind turbine. It may be difficult to give full play to the power support capacity of the wind farm, or the unit rotor rotation kinetic energy release is too large to reach the minimum speed and exit the frequency control, thereby deteriorating the system frequency. The present invention adjusts the active output according to the contribution of each unit in the wind farm, which can avoid the unit speed limit in the low wind speed area, give full play to the power support capacity of the wind farm, and improve the system frequency characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0054] Figure 1 A flow chart of a wind farm frequency coordination control method considering multi-state quantity coupling constraints according to an embodiment of the present invention;

[0055] Figure 2 This is a diagram showing an example of a doubly-fed wind turbine generator system connected to the grid in an embodiment of the present invention;

[0056] Figure 3 This is a rendering of an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] The core of the present invention is to provide a wind farm frequency coordination control method that considers the coupling constraints of multiple state quantities, considers the influence of multiple state quantities including rotor speed, pitch angle and rotor current on the power support capacity of doubly-fed wind turbines, evaluates the maximum power support capacity of doubly-fed wind turbines, and coordinates the doubly-fed wind turbines in the wind farm to participate in frequency control, so as to make full use of the power support capacity of the wind farm. Compared with the prior art, the present invention achieves the maximum utilization of the power support capacity of the doubly-fed wind farm by accurately evaluating the power support capacity of the doubly-fed wind turbines under the coupling constraints of speed, pitch angle and rotor current, and effectively improves the frequency characteristics of the system. The present invention adjusts the active output according to the contribution of each unit in the wind farm, which can avoid the speed limit of the unit in the low wind speed area, give full play to the power support capacity of the wind farm, and improve the frequency characteristics of the system.

[0059] like Figure 1As shown, the embodiment of the present invention discloses a wind farm frequency coordination control method considering multi-state quantity coupling constraints, comprising the following steps:

[0060] S101, collect the grid frequency in real time, and start control when the frequency deviation exceeds the dead zone;

[0061] S102, evaluating the maximum power support capacity of each doubly-fed wind turbine in the wind farm according to the prediction model of the rotor speed, pitch angle and rotor current and the optimization model with the goal of maximizing the active power of the doubly-fed wind turbine;

[0062] S103, calculating the contribution of each doubly-fed wind turbine generator set in the wind farm according to the maximum power support capacity of the doubly-fed wind turbine generator set;

[0063] S104, calculating the power control constant of the doubly-fed wind turbine generator set according to the frequency of the wind farm grid connection point and the contribution of the doubly-fed wind turbine generator set, and implementing control.

[0064] It can be understood that when the control is started when the frequency deviation exceeds the dead zone, the wind farm frequency coordination control mechanism is started, that is, the subsequent steps S102-S104.

[0065] In the embodiment of the present invention, the rotor speed is one of the important indicators of the operating state of the doubly-fed wind turbine set, which directly affects the output power, efficiency and system stability of the wind turbine set. Therefore, establishing an accurate rotor speed prediction model is of great significance for optimizing the operation of the wind turbine set, improving the power generation efficiency and ensuring the safety of the system. The embodiment of the present invention uses information such as the equivalent damping of the transmission shaft system of the doubly-fed wind turbine set, the equivalent stiffness of the transmission shaft system, the moment of inertia of the induction motor, and the angular displacement of the transmission shaft system of the doubly-fed wind turbine set to construct a rotor speed prediction model to accurately evaluate the rotor speed for the power support capacity of the doubly-fed wind turbine set.

[0066] In specific implementation, in step S102, the rotor speed prediction model is established according to the following method:

[0067] According to the rotor speed of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent damping of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a first speed parameter at the current moment is obtained;

[0068] According to the wind turbine speed of the doubly-fed wind turbine generator set at the previous moment and the ratio of the electromagnetic power of the doubly-fed wind turbine generator set to the rotational inertia of the induction motor corresponding to the control sampling interval, a second speed parameter at the current moment is obtained;

[0069] According to the angular displacement of the transmission shaft system of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent damping of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a third speed parameter at the current moment is obtained;

[0070] According to the angular displacement of the transmission shaft system of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent stiffness of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a fourth speed parameter at the current moment is obtained;

[0071] The rotor speed of the doubly-fed wind turbine generator set at the current moment is obtained according to the first speed parameter, the second speed parameter, the third speed parameter and the fourth speed parameter at the current moment.

[0072] In some embodiments of the present invention, the rotor speed prediction model can be expressed as:

[0073]

[0074] In the formula, J m,i , J r,i are the rotational inertia of the wind turbine and induction motor of the i-th doubly-fed wind turbine group respectively; ω m,i (k),ω m,i (k+1) are the wind turbine speeds of the i-th doubly-fed wind turbine generator set at time k and time k+1 respectively; ω r,i (k),ω r,i (k+1) are the rotor speeds of the i-th doubly-fed wind turbine generator set at time k and time k+1 respectively; P m,i (k), P e,i (k) are the mechanical power and electromagnetic power of the i-th doubly-fed wind turbine generator set at time k; θ s,i (k),θ s,i (k+1) are the angular displacements of the transmission shaft system of the i-th doubly-fed wind turbine at time k and time k+1 respectively; K s,i is the equivalent stiffness of the transmission shaft system of the i-th doubly-fed wind turbine; D s,i is the equivalent damping of the transmission shaft of the i-th doubly-fed wind turbine; ΔT s To control the sampling interval; P m0,i is the initial mechanical power of the i-th doubly-fed wind turbine; ρ is the air density; R is the radius of the wind turbine blade; V w,i is the wind speed of the i-th doubly-fed wind turbine; β i (k) is the pitch angle of the i-th doubly fed wind turbine at time k, C p,i (ω m,i (k),β i (k)), χ i (k) and λ i (k) are all intermediate parameters in the calculation process, among which, C p,i (ω m,i (k),β i (k)) represents the coupled control function of the rotor speed and pitch angle at time k.

[0075] In an embodiment of the present invention, the prediction model of the pitch angle of a doubly-fed wind turbine is an important technology in a wind power generation system, which involves the precise control and optimization of the output power of a wind turbine. Pitch angle control refers to changing the aerodynamic characteristics of the blades by adjusting the pitch angle of the wind turbine blades (i.e., the angle between the blades and the wind rotor plane), thereby adjusting the output power of the wind turbine. The embodiment of the present invention uses the control adjustment variables of the doubly-fed wind turbine, the rotor speed of the doubly-fed wind turbine, and the proportion and integral coefficient of the PAC to construct a pitch angle prediction model to accurately evaluate the power support capability of the doubly-fed wind turbine based on the pitch angle.

[0076] In specific implementation, in step S102, the pitch angle prediction model is established according to the following method:

[0077] According to the control adjustment variable of the pitch angle of the doubly-fed wind turbine generator set at the previous moment and the proportional relationship between the control sampling interval and the time constant of the pitch angle control, the first pitch angle parameter at the current moment is obtained;

[0078] According to the rotor speed of the doubly-fed wind turbine at the current moment and the ratio of the proportional coefficient of the PAC to the time constant of the pitch angle control, the second pitch angle parameter at the current moment is obtained;

[0079] According to the rotor speed of the doubly-fed wind turbine at the previous moment, as well as the control sampling interval, the proportional coefficient of the PAC, the integral coefficient, and the time constant of the pitch angle control, the third pitch angle parameter at the current moment is obtained;

[0080] According to the reference value of the rotor speed of the doubly-fed wind turbine and the ratio of the integral coefficient of the PAC to the time constant of the pitch angle control at the control sampling interval, the fourth pitch angle parameter at the current moment is obtained;

[0081] The pitch angle of the doubly-fed wind turbine generator set at the current moment is obtained according to the first pitch angle parameter, the second pitch angle parameter, the third pitch angle parameter, the fourth pitch angle parameter at the current moment and the pitch angle of the doubly-fed wind turbine generator set at the previous moment.

[0082] In some embodiments of the present invention, the pitch angle prediction model may be expressed as:

[0083]

[0084] In the formula, x(k+1) and x(k) are the control variables of the pitch angle of the i-th doubly fed wind turbine at time k+1 and time k, ΔT s To control the sampling interval; T pac,i is the time constant of pitch angle control; k pp , k ip are the proportional and integral coefficients of PAC respectively; ωr,i (k),ω r,i (k+1) are the rotor speeds of the i-th doubly-fed wind turbine generator set at time k and time k+1 respectively; is the reference value of the rotor speed of the i-th doubly-fed wind turbine; β i (k+1), β i (k) is the pitch angle of the i-th doubly fed wind turbine at time k+1 and time k.

[0085] In an embodiment of the present invention, the rotor current prediction model of the doubly-fed wind turbine is a key part in the control of the wind power generation system, which is directly related to the operating efficiency and stability of the generator. In a doubly-fed wind power generation system, the control of the rotor current is an important means to achieve maximum power tracking, grid voltage orientation and stable operation of the system. Through the precise control of the rotor current, it can be ensured that the generator can maintain efficient and stable operation under different wind speeds and grid conditions. The embodiment of the present invention uses the d-axis and q-axis components of the rotor current of the doubly-fed wind turbine as well as the information such as the rotor resistance, rotor inductance, and leakage magnetic coefficient to construct a rotor current prediction model to accurately evaluate the rotor current's power support capability for the doubly-fed wind turbine.

[0086] In specific implementation, in step S102, the rotor current prediction model is established according to the following method:

[0087] According to the rotor current d-axis component of the doubly-fed wind turbine generator set at the previous moment, the control sampling interval, the rotor resistance, the rotor inductance, and the leakage magnetic coefficient, the first d-axis parameter at the current moment is obtained;

[0088] According to the d-axis component of the rotor voltage reference value, the rotor inductance, the leakage magnetic coefficient and the control sampling interval of the doubly-fed wind turbine generator set, the second d-axis parameter at the current moment is obtained;

[0089] According to the slip angular velocity, the d-axis component of the rotor current and the control sampling interval of the doubly-fed wind turbine generator set at the previous moment, the third d-axis parameter at the current moment is obtained;

[0090] According to the q-axis component of the rotor current of the doubly-fed wind turbine generator set at the previous moment, the control sampling interval, the rotor resistance, the rotor inductance, and the leakage magnetic coefficient, the first q-axis parameter at the current moment is obtained;

[0091] According to the q-axis component of the rotor voltage reference value, the rotor inductance, the leakage magnetic coefficient and the control sampling interval of the doubly-fed wind turbine generator set, the second q-axis parameter at the current moment is obtained;

[0092] According to the slip angular velocity, the q-axis component of the rotor current and the control sampling interval of the doubly-fed wind turbine generator set at the previous moment, the third q-axis parameter at the current moment is obtained;

[0093] According to the three d-axis parameters and three q-axis parameters corresponding to the current moment, the rotor current prediction result of the doubly-fed wind turbine generator set at the current moment is calculated.

[0094] In some embodiments of the present invention, the rotor current prediction model can be expressed as:

[0095]

[0096] In the formula, i rd,i (k), i rd,i (k+1) are the d-axis components of the rotor current of the i-th doubly-fed wind turbine generator set at time k and time k+1 respectively; i rq,i (k), i rq,i (k+1) are the q-axis components of the rotor current of the i-th doubly-fed wind turbine generator set at time k and time k+1 respectively; I r,i (k+1) is the rotor current of the i-th doubly-fed wind turbine generator set at time k+1; R r is the rotor resistance; ω s is the synchronous angular velocity; ω p,i (k) is the slip angular velocity of the i-th doubly fed wind turbine generator set at time k, where ω p,i (k) = ω s -ω r,i (k); L s , L r , L m They are stator inductance, rotor inductance and excitation inductance respectively; is the magnetic flux leakage coefficient; are the dq-axis components of the rotor voltage reference value of the i-th doubly-fed wind turbine; U s is the stator voltage amplitude.

[0097] Through the above embodiments, the prediction structure of the rotational speed, pitch angle and rotor current can be accurately measured, so as to further accurately evaluate the power support capability of the doubly-fed wind turbine generator set under the coupling constraints of the rotational speed, pitch angle and rotor current.

[0098] In specific implementation, in step S102, the optimization model is established in the following way:

[0099] The active power of the wind farm under the constraints of the rotor current and the rotor speed at each moment in the optimization time domain is sorted in descending order, and the first parameter of the maximum value of the active power of the wind farm under the constraints of the rotor current and the rotor speed in the optimization time domain is obtained;

[0100] The active power of the wind farm under the constraints of the rotor speed and pitch angle at each moment in the optimization time domain is sorted in descending order, and the second parameter of the maximum active power of the wind farm under the constraints of the rotor speed and pitch angle in the optimization time domain is obtained;

[0101] A smaller active power value is selected from the first parameter of the maximum active power value and the second parameter of the maximum active power value as the maximum active power value of the double-fed wind turbine generator set after optimization.

[0102] In specific implementation, the active power of the wind farm under the constraints of rotor current and rotor speed, and the active power of the wind farm under the constraints of rotor speed and pitch angle respectively meet the following requirements:

[0103]

[0104] Among them, Γ1(k+1) is the active power of the wind farm under the constraints of rotor current and rotor speed at time k+1, ω r,i (k) is the rotor speed of the i-th doubly-fed wind turbine generator set at time k, L m is the magnetizing inductance, U s is the stator voltage amplitude, I r,i (k+1) is the rotor current of the i-th doubly-fed wind turbine generator set at time k+1, ω s is the synchronous angular velocity, L s is the stator inductance, σ is the leakage coefficient, L r is the rotor inductance, R r is the rotor resistance, ω r,i (k+1) is the rotor speed of the i-th doubly-fed wind turbine generator set at time k+1, ω p,i (k+1) is the slip angular velocity of the i-th doubly fed wind turbine at time k+1, Γ2(k+1) is the active power of the wind farm under the constraints of rotor speed and pitch angle at time k+1, ρ is the air density, R is the radius of the wind turbine blade, V w,i is the wind speed C of the i-th doubly-fed wind turbine generator set p,i [ω m,i (k+1),β i (k+1)] is the coupling control function of the rotor speed and pitch angle at time k+1, J r,i is the moment of inertia of the induction motor of the i-th doubly-fed wind turbine, ΔT s Indicates the control sampling interval.

[0105] In specific implementation, in step S103, the maximum power support capacity of the doubly-fed wind turbine generator set is determined by the following method:

[0106] S301, setting the optimized time domain T p , and according to the initial values ​​of the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine at time k, the rotor speed, pitch angle and rotor current prediction model is used to calculate the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine at time k+1, where time k is the time of starting control;

[0107] S302, calculating the active power of the doubly-fed wind turbine generator set at time k+1 using an optimization model according to the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine generator set at time k+1;

[0108] S303, iteratively calculate k+T using the prediction model and optimization model p The rotor speed, pitch angle, rotor current and active power of the doubly fed wind turbine at each moment are optimized, and the active power calculation results of the doubly fed wind turbine in the time domain are traversed and optimized, and the maximum value of the active power of the doubly fed wind turbine that meets the constraints is determined as the maximum power support capacity.

[0109] In specific implementation, in step S303, the constraint conditions include:

[0110] 1) At the current moment, the rotor current of each doubly-fed wind turbine generator set is less than or equal to the maximum rotor current;

[0111] 2) At the current moment, the rotor speed of each doubly-fed wind turbine generator set is less than or equal to the maximum allowable rotor speed and greater than or equal to the minimum allowable rotor speed;

[0112] 3) At the current moment, the pitch angle of each doubly-fed wind turbine generator set is less than or equal to the maximum allowable pitch angle and greater than 0;

[0113] 4) At the current moment, the pitch angle deviation value of each doubly-fed wind turbine set is less than or equal to the maximum pitch angle deviation value and greater than or equal to the minimum pitch angle deviation value;

[0114] 5) The pitch angle deviation value of each doubly-fed wind turbine set at the current moment is the pitch angle difference between the doubly-fed wind turbine set at the current moment and the previous moment.

[0115] In specific implementation, in step S105, the contribution of the i-th doubly-fed wind turbine generator set is calculated according to the following method:

[0116] The contribution of each doubly-fed wind turbine is obtained based on the ratio of the maximum power support capacity of each wind turbine to the sum of the maximum power support capacity of all wind turbines in the wind farm. The embodiment of the present invention allocates compensation power in the same proportion according to the proportion of the active power of different doubly-fed wind turbines in the wind farm to the sum of the active power of all doubly-fed wind turbines in the wind farm. This method can avoid the speed limit of the unit in the low wind speed area, give full play to the power support capacity of the wind farm, and improve the system frequency characteristics.

[0117] In specific implementation, in step S104, the power control constant of each doubly-fed wind turbine generator set is calculated according to the following method:

[0118] According to the differential of the droop coefficient and the frequency deviation of each doubly-fed wind turbine generator set in the wind farm, a first control constant of each doubly-fed wind turbine generator set in the wind farm is obtained;

[0119] According to the product of the inertia coefficient of each doubly-fed wind turbine generator set in the wind farm and the frequency deviation, a second control constant of each doubly-fed wind turbine generator set in the wind farm is obtained;

[0120] Obtaining compensation power of the doubly-fed wind farm according to the sum of the first control constant and the second control constant of all doubly-fed wind turbines in the wind farm;

[0121] According to the product of the mechanical power and the control parameter of each doubly-fed wind turbine in the wind farm and the compensation power of the doubly-fed wind turbine in the wind farm, the power control constant of each doubly-fed wind turbine is obtained.

[0122] In some embodiments, the power control constant of the i-th doubly-fed wind turbine generator set can be expressed as:

[0123] P ctrl,i =P m,i +c i ΔP c

[0124]

[0125] In the formula, ΔP c is the compensation power of the doubly-fed wind farm; N w is the number of doubly-fed wind turbines in the wind farm; Δf is the frequency deviation; k d,i , k d,i are the droop coefficient and inertia coefficient of the i-th doubly-fed wind turbine generator set respectively.

[0126] It is understandable that if the method in the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or part of the contribution to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program code.

[0127] To verify the effectiveness of the method of the present invention, Figure 2The example system wiring diagram shown is used as an example for analysis. The capacity of the synchronous machines is 100MW respectively. There are 45 direct-drive wind turbines with a rated capacity of 1.5MW and a rated voltage of 575V. Considering the wind speed differences in the wind power clusters, the wind power clusters are weighted according to the capacity to be equivalent to 3 double-fed wind farms, and the input wind speeds are low wind speed, medium wind speed and high wind speed respectively. The present invention simulates different system frequency changes by changing the load L1 to verify the system frequency characteristics and unit response characteristics under different methods. Method 1 is the comparison group, which is the system frequency characteristics and unit response characteristics of the double-fed wind farm under comprehensive inertia control. Method 2 is the method of the present invention. Record and compare the system frequency waveform and the power waveform of the double-fed wind farm.

[0128] Figure 3 (a) is the system frequency waveform, Figure 3 (b), (c) and (d) are the power and state quantity waveforms of wind farms 1, 2 and 3 respectively. The horizontal axis in the figure is time; the red Method2 is the change curve of frequency, power and state quantity when the method of the present invention is adopted, and the blue Method1 is the change curve of frequency, power and state quantity when the comprehensive inertia control is adopted. The example shows that when the method of the present invention is adopted, the maximum frequency of the system is 49.87Hz, the maximum frequency under the comprehensive inertia control is 49.85Hz, and the system frequency deviation becomes smaller. Under the comprehensive inertia control, the wind turbines in the medium and low wind speed zone release too much rotational kinetic energy, resulting in the speed exceeding the allowable range, and the unit frequency control is exited, causing the system to have a secondary frequency drop. The method of the present invention reduces the contribution of wind turbines in the medium and low wind speed zone, increases the power support time of wind turbines in the medium and low wind speed zone, thereby avoiding the secondary drop of the system frequency, and at the same time changes the active output according to the power support capacity of each unit in the wind farm, thereby improving the system frequency characteristics. The method of the present invention avoids the exit of frequency control of wind farms 1 and 2 by increasing the contribution of wind farm 3. Under the method of the present invention, the maximum active power of the wind farm 3 is 1.14pu, the maximum rotor current is 1.05pu, the minimum rotation speed is 1.02pu, and the pitch angle is reduced from 0.75° to 0 to increase the active power output of the wind farm.

[0129] In summary, the method of the present invention adjusts the active output according to the contribution of each unit in the wind farm, which can avoid the unit speed exceeding the limit in the low wind speed area and reduce the system frequency deviation.

[0130] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A wind farm frequency coordination control method considering multi-state quantity coupling constraints, characterized in that: The method specifically comprises the following steps: S101, collect the grid frequency in real time, and start control when the frequency deviation exceeds the dead zone; S102, evaluating the maximum power support capacity of each doubly-fed wind turbine in the wind farm according to the prediction model of the rotor speed, pitch angle and rotor current and the optimization model with the goal of maximizing the active power of the doubly-fed wind turbine; S103, calculating the contribution of each doubly-fed wind turbine generator set in the wind farm according to the maximum power support capacity of the doubly-fed wind turbine generator set; S104, calculating the power control constant of the doubly-fed wind turbine generator set according to the frequency of the wind farm grid connection point and the contribution of the doubly-fed wind turbine generator set, and implementing control.

2. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S102, the prediction model of the rotor speed is established according to the following method: According to the rotor speed of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent damping of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a first speed parameter at the current moment is obtained; According to the wind turbine speed of the doubly-fed wind turbine generator set at the previous moment and the ratio of the electromagnetic power of the doubly-fed wind turbine generator set to the rotational inertia of the induction motor corresponding to the control sampling interval, a second speed parameter at the current moment is obtained; According to the angular displacement of the transmission shaft system of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent damping of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a third speed parameter at the current moment is obtained; According to the angular displacement of the transmission shaft system of the doubly-fed wind turbine generator set at the previous moment and the ratio of the equivalent stiffness of the transmission shaft system of the doubly-fed wind turbine generator set corresponding to the control sampling interval to the rotational inertia of the induction motor, a fourth speed parameter at the current moment is obtained; The rotor speed of the doubly-fed wind turbine generator set at the current moment is obtained according to the first speed parameter, the second speed parameter, the third speed parameter and the fourth speed parameter at the current moment.

3. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S102, the prediction model of the pitch angle is established according to the following method: According to the control adjustment variable of the pitch angle of the doubly-fed wind turbine generator set at the previous moment and the proportional relationship between the control sampling interval and the time constant of the pitch angle control, the first pitch angle parameter at the current moment is obtained; According to the rotor speed of the doubly-fed wind turbine at the current moment and the ratio of the proportional coefficient of the PAC to the time constant of the pitch angle control, the second pitch angle parameter at the current moment is obtained; According to the rotor speed of the doubly-fed wind turbine at the previous moment, as well as the control sampling interval, the proportional coefficient of the PAC, the integral coefficient, and the time constant of the pitch angle control, the third pitch angle parameter at the current moment is obtained; According to the reference value of the rotor speed of the doubly-fed wind turbine and the ratio of the integral coefficient of the PAC to the time constant of the pitch angle control at the control sampling interval, the fourth pitch angle parameter at the current moment is obtained; The pitch angle of the doubly-fed wind turbine generator set at the current moment is obtained according to the first pitch angle parameter, the second pitch angle parameter, the third pitch angle parameter, the fourth pitch angle parameter at the current moment and the pitch angle of the doubly-fed wind turbine generator set at the previous moment.

4. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S102, the prediction model of the rotor current is established according to the following method: According to the rotor current d-axis component of the doubly-fed wind turbine generator set at the previous moment, the control sampling interval, the rotor resistance, the rotor inductance, and the leakage magnetic coefficient, the first d-axis parameter at the current moment is obtained; According to the d-axis component of the rotor voltage reference value, the rotor inductance, the leakage magnetic coefficient and the control sampling interval of the doubly-fed wind turbine generator set, the second d-axis parameter at the current moment is obtained; According to the slip angular velocity, the d-axis component of the rotor current and the control sampling interval of the doubly-fed wind turbine generator set at the previous moment, the third d-axis parameter at the current moment is obtained; According to the q-axis component of the rotor current of the doubly-fed wind turbine generator set at the previous moment, the control sampling interval, the rotor resistance, the rotor inductance, and the leakage magnetic coefficient, the first q-axis parameter at the current moment is obtained; According to the q-axis component of the rotor voltage reference value, the rotor inductance, the leakage magnetic coefficient and the control sampling interval of the doubly-fed wind turbine generator set, the second q-axis parameter at the current moment is obtained; According to the slip angular velocity, the q-axis component of the rotor current and the control sampling interval of the doubly-fed wind turbine generator set at the previous moment, the third q-axis parameter at the current moment is obtained; According to the three d-axis parameters and three q-axis parameters corresponding to the current moment, the rotor current prediction result of the doubly-fed wind turbine generator set at the current moment is calculated.

5. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S102, the optimization model is established in the following way: The active power of the wind farm under the constraints of the rotor current and the rotor speed at each moment in the optimization time domain is sorted in descending order, and the first parameter of the maximum value of the active power of the wind farm under the constraints of the rotor current and the rotor speed in the optimization time domain is obtained; The active power of the wind farm under the constraints of the rotor speed and pitch angle at each moment in the optimization time domain is sorted in descending order, and the second parameter of the maximum active power of the wind farm under the constraints of the rotor speed and pitch angle in the optimization time domain is obtained; A smaller active power value is selected from the first parameter of the maximum active power value and the second parameter of the maximum active power value as the maximum active power value of the double-fed wind turbine generator set after optimization.

6. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 5, characterized in that: The active power of the wind farm under the constraints of rotor current and rotor speed, and the active power of the wind farm under the constraints of rotor speed and pitch angle satisfy: Where Γ1(k+1) is the active power of the wind farm under the constraints of rotor current and rotor speed at time k+1, ωr,i(k) is the rotor speed of the i-th doubly fed wind turbine at time k, and L m is the magnetizing inductance, U s is the stator voltage amplitude, Ir,i(k+1) is the rotor current of the i-th doubly fed wind turbine at time k+1, ω s is the synchronous angular velocity, L s is the stator inductance, σ is the leakage coefficient, L r is the rotor inductance, R r is the rotor resistance, ω r,i (k+1) is the rotor speed of the i-th doubly-fed wind turbine generator set at time k+1, ω p,i (k+1) is the slip angular velocity of the i-th doubly fed wind turbine at time k+1, Γ2(k+1) is the active power of the wind farm under the constraints of rotor speed and pitch angle at time k+1, ρ is the air density, R is the radius of the wind turbine blade, V w,i is the wind speed C of the i-th doubly-fed wind turbine p,i [ω m,i (k+1),β i (k+1)] is the coupling control function of the rotor speed and pitch angle at time k+1, J r,i is the moment of inertia of the induction motor of the i-th doubly-fed wind turbine, ΔT s Indicates the control sampling interval.

7. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S103, the maximum power support capability of the doubly-fed wind turbine generator set is determined by the following method: S301, setting the optimized time domain T p , and according to the initial values ​​of the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine at time k, the rotor speed, pitch angle and rotor current prediction model is used to calculate the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine at time k+1, where time k is the time of starting control; S302, calculating the active power of the doubly-fed wind turbine generator set at time k+1 using an optimization model according to the rotor speed, pitch angle and rotor current of the doubly-fed wind turbine generator set at time k+1; S303, iteratively calculate k+T using the prediction model and optimization model p The rotor speed, pitch angle, rotor current and active power of the doubly fed wind turbine at each moment are optimized, and the active power calculation results of the doubly fed wind turbine in the time domain are traversed and optimized, and the maximum value of the active power of the doubly fed wind turbine that meets the constraints is determined as the maximum power support capacity.

8. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 7, characterized in that: In step S303, the constraints include: At the current moment, the rotor current of each doubly-fed wind turbine set is less than or equal to the maximum rotor current value; at the current moment, the rotor speed of each doubly-fed wind turbine set is less than or equal to the maximum allowable rotor speed value and greater than or equal to the minimum allowable rotor speed value; at the current moment, the pitch angle of each doubly-fed wind turbine set is less than or equal to the maximum allowable pitch angle value and greater than 0; at the current moment, the pitch angle deviation value of each doubly-fed wind turbine set is less than or equal to the maximum pitch angle deviation value and greater than or equal to the minimum pitch angle deviation value; the pitch angle deviation value of each doubly-fed wind turbine set at the current moment is the difference in pitch angle between the doubly-fed wind turbine set at the current moment and the previous moment.

9. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S104, the contribution of each doubly-fed wind turbine generator set is calculated according to the following method: According to the ratio of the maximum power support capacity of each wind turbine set to the sum of the maximum power support capacity of all wind turbine sets in the wind farm, the contribution of each doubly-fed wind turbine set is obtained.

10. A wind farm frequency coordination control method considering multi-state quantity coupling constraints according to claim 1, characterized in that: In step S104, the power control constant of each doubly-fed wind turbine generator set is calculated according to the following method: According to the differential of the droop coefficient and the frequency deviation of each doubly-fed wind turbine generator set in the wind farm, a first control constant of each doubly-fed wind turbine generator set in the wind farm is obtained; According to the product of the inertia coefficient of each doubly-fed wind turbine generator set in the wind farm and the frequency deviation, a second control constant of each doubly-fed wind turbine generator set in the wind farm is obtained; Obtaining compensation power of the doubly-fed wind farm according to the sum of the first control constant and the second control constant of all doubly-fed wind turbines in the wind farm; According to the product of the mechanical power and the control parameter of each doubly-fed wind turbine in the wind farm and the compensation power of the doubly-fed wind turbine in the wind farm, the power control constant of each doubly-fed wind turbine is obtained.

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