Centralized primary frequency modulation coordination control method for wind power plant

Abstract

The invention provides a centralized primary frequency modulation coordination control method for a wind power plant, which comprises the following steps of: S1, determining wind turbine generators with frequency modulation capability, and dividing wind turbine groups; s2, calculating the actual additional energy of the wind turbine generator; s3, determining a relational expression between the net increment of the active output power of the wind turbine generator and the frequency modulation duration; s4, constructing a function L of the active output power net increment and the frequency modulation duration of the wind turbine group; s5, solving the function L to obtain an active output power net increment and frequency modulation duration; s6, whether the active output power net increment and the frequency modulation duration of the wind turbine group meet preset constraint conditions or not is judged; and S7, controlling each wind turbine group to carry out frequency active support according to the active output power net increment and the frequency modulation duration which meet preset constraint conditions. According to the method, the frequency modulation capability of the wind turbine generator can be estimated; and the active output power net increment and the frequency modulation duration adaptive to the frequency support characteristics of the wind turbine generator can be quickly determined.

Description

Technical Field

[0001] The present invention relates to the field of wind farm frequency regulation, and in particular to a wind farm centralized primary frequency regulation coordination control method. Background Art

[0002] Doubly-fed wind turbines are widely used as mainstream models in wind power generation systems due to their mature technology and high cost-effectiveness. However, actual project operation shows that due to the decoupling of the rotor speed of variable-speed wind turbines from the system frequency, doubly-fed wind turbines cannot slow down frequency changes like conventional generators when the system frequency drops. The higher the penetration rate of wind turbines, the less conducive it is to the stability of the grid frequency. Therefore, variable-speed wind turbines participating in system frequency regulation and achieving controllable operation are urgent requirements for the development of wind power grid-connected operation.

[0003] In order to solve the problem of doubly-fed wind turbines participating in system frequency regulation, existing research has proposed some effective control methods, including power reserve control, primary frequency regulation control, etc. However, under the reserve power mode, wind turbines reduce the utilization rate of wind energy, and the uncertainty of wind speed prediction has a great impact on the reserved reserve capacity of wind turbines. Primary frequency regulation control uses the rapid release of rotor kinetic energy to provide frequency support in the early stage of frequency response, and has a fast response speed. The existing technology does not take into account the frequency support characteristics of wind turbines with different wind speeds, and lacks reasonable coordination of wind turbines with different wind speeds participating in the frequency regulation process.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the present invention proposes a coordination and cooperation control strategy for wind turbines with different wind speeds to participate in the frequency modulation process according to the frequency support characteristics of wind turbines with different wind speeds.

[0006] The present invention provides a wind farm centralized primary frequency regulation coordinated control method, comprising the following steps:

[0007] S1. Real-time measurement of wind speed, determination of wind turbines with frequency modulation capability in the wind farm according to the wind speed, and division of wind turbines with frequency modulation capability into wind turbine groups with different wind speeds;

[0008] S2. Calculate the actual additional energy E of the wind turbine according to the total kinetic energy released by the wind turbine and the wind energy loss f ;

[0009] S3. According to the actual increase in energy E f Determine the net increase in active output power ΔP of the wind turbine e The relationship with the frequency modulation duration ΔT;

[0010] S4. Based on step S3, construct the net increase ΔP of the active output power of the wind turbine group b Function L of the frequency modulation duration ΔT;

[0011] S5. Solve the function L according to the conditional extreme value to obtain the net increase of active output power of the wind turbine group ΔP b and FM duration ΔT;

[0012] S6. Determine the net increase ΔP of the active output power of the wind turbine group obtained by solving b Whether the frequency modulation duration ΔT meets the preset constraint conditions, if so, the net increase of active output power ΔP is output b and the frequency modulation duration ΔT; if not, the boundary value of the parameter that does not meet the preset constraint condition is substituted into step S5 until the preset constraint condition is met;

[0013] S7. When the wind farm needs active frequency support, the wind farm centrally controls each wind turbine group to achieve a net increase in active output power ΔP that meets the preset constraints. b And the frequency modulation duration ΔT is used for active frequency support.

[0014] Further, in step S2, the actual additional energy E of the wind turbine is f Calculated by the following formula:

[0015]

[0016] Among them, E k Represents the total kinetic energy released by the wind turbine, E w Represents wind energy loss, H w represents the inertia time constant, ω0 represents the initial speed of the wind turbine, k represents the multiple of the rotor speed when it exits frequency modulation and the initial speed, ΔT represents the frequency modulation duration, ΔP m Indicates the change in mechanical power.

[0017] Further, in step S3, the net increase in active output power of the wind turbine generator set ΔP e The relationship with the frequency modulation duration ΔT is obtained by the following method:

[0018] Since the actual additional energy E of the wind turbine f The net increase of active output power of wind turbines ΔP e The following relationship exists:

[0019] E f =ΔP e ΔT (3.1)

[0020] Combining formulas (2.1) and (3.1), we can obtain the net increase in active output power of the wind turbine ΔPe The relationship with the frequency modulation duration ΔT is as follows:

[0021]

[0022] Among them, ΔP e It represents the net increase of active output power of wind turbine, H w represents the inertia time constant, ω0 represents the initial speed of the wind turbine, k represents the multiple of the rotor speed when it exits frequency modulation and the initial speed, ΔT represents the frequency modulation duration, ΔP m Indicates the change in mechanical power.

[0023] Furthermore, ΔP m Calculated by the following formula:

[0024]

[0025] Among them, P mopt represents the initial power of the wind turbine before frequency modulation, ρ represents the air density, π represents the circumference of a circle, R represents the radius of the wind turbine rotor, and v w Indicates wind speed, ΔC P Indicates the change in wind energy utilization coefficient.

[0026] Further, in step S4, the net increase in active output power of the wind turbine group ΔP b The relationship between the function L and the frequency modulation duration ΔT is as follows:

[0027]

[0028] Where a represents the serial number of the wind turbine in the first wind turbine group, A represents the total number of wind turbines in the first wind turbine group, ΔT represents the frequency modulation duration, ΔP b,1 , ΔP b,2 and ΔP b,n They represent the net increase in active output power of the first, second and nth wind turbine groups, d represents the sequence number of the wind turbine group in the second wind turbine group, D represents the total number of wind turbine groups in the second wind turbine group, λ represents the weight coefficient, ΔP L represents the load disturbance power;

[0029] The frequency modulation duration of all wind turbines in the same wind turbine group is the same; the net increase in active output power of the wind turbine group is obtained by adding the net increase in active output power of all wind turbines in the wind turbine group.

[0030] Further, in step S6, the preset constraint condition is:

[0031]

[0032] Where τ represents the minimum frequency modulation duration, ΔT n,max Indicates the maximum frequency modulation duration of the nth wind turbine group, ΔT n,rec It represents the maximum time required for the power of the n-1th wind turbine to recover to 0.9 times the initial power of the frequency regulation, ΔP b,n,max It represents the maximum net increase in active output power of the nth wind turbine group.

[0033] Further, in step S7, when the wind farm needs active frequency support, the net increase ΔP of the active output power of the wind turbine group that meets the preset constraint conditions is b,n It is input as a frequency modulation active power instruction to the wind turbine group, and the frequency of wind turbine groups with different wind speeds is modulated at the same time, and is executed until the frequency modulation duration meets the preset constraint conditions.

[0034] Further, in step S1, the wind turbine generator set with frequency modulation capability meets the following conditions: the wind speed of the wind turbine generator set in operation is greater than 6 m / s and less than or equal to 12 m / s.

[0035] The beneficial effects of the present invention are as follows: the present invention differentiates wind turbines according to wind speed, and determines the net increase in active output power and the frequency modulation duration of wind turbines with different wind speeds participating in the frequency modulation process by conditional extreme values ​​and setting preset constraints, so that the net increase in active output power and the frequency modulation duration can be adapted to the frequency support characteristics, thereby reducing the possibility of primary and secondary drops in the system frequency, and providing support for the frequency modulation of the wind turbine parameter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0037] Figure 1 It is a flow chart of the present invention;

[0038] Figure 2 It is a schematic diagram of wind speed zoning and operating characteristics of a doubly-fed wind turbine generator set in a specific implementation manner of the present invention;

[0039] Figure 3 It is a schematic diagram of frequency modulation power variation of a doubly-fed wind turbine generator set in a specific implementation manner of the present invention;

[0040] Figure 4 A graph showing the relationship between the frequency modulation duration and the output power increment of a doubly-fed wind turbine generator system at different wind speeds in a specific embodiment of the present invention;

[0041] Figure 5 It is a characteristic diagram of output power consumption of wind turbine groups with different wind speeds in a specific implementation manner of the present invention;

[0042] Figure 6 It is a schematic diagram of the structure of a simulation system in a specific implementation manner of the present invention;

[0043] Figure 7 It is a comparison of the effects of the proposed strategy in the specific implementation of the present invention and the strategy without active support for wind power;

[0044] Figure 8 The effect comparison between the proposed strategy in the implementation mode of the present invention and the strategy of simultaneously exiting the frequency regulation of wind power is shown in FIG. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings:

[0046] The present invention provides a wind farm centralized primary frequency regulation coordinated control method, comprising the following steps:

[0047] S1. Real-time measurement of wind speed, determination of wind turbines with frequency modulation capability in the wind farm according to the wind speed, and division of wind turbines with frequency modulation capability into wind turbine groups with different wind speeds;

[0048] S2. Calculate the actual additional energy E of the wind turbine according to the total kinetic energy released by the wind turbine and the wind energy loss f ;

[0049] S3. According to the actual increase in energy E f Determine the net increase in active output power ΔP of the wind turbine e The relationship with the frequency modulation duration ΔT;

[0050] S4. Based on step S3, construct the net increase ΔP of the active output power of the wind turbine group b Function L of the frequency modulation duration ΔT;

[0051] S5. Solve the function L according to the conditional extreme value to obtain the net increase of active output power of the wind turbine group ΔP b and FM duration ΔT;

[0052] S6. Determine the net increase ΔP of the active output power of the wind turbine group obtained by solving b Whether the frequency modulation duration ΔT meets the preset constraint conditions, if so, the net increase of active output power ΔP is output b and the frequency modulation duration ΔT; if not, the boundary value of the parameter that does not meet the preset constraint condition is substituted into step S5 until the preset constraint condition is met;

[0053] S7. When the wind farm needs active frequency support, the wind farm centrally controls each wind turbine group to achieve a net increase in active output power ΔP that meets the preset constraints. bThrough the above method, the net increase of active output power and the duration of frequency modulation that are adapted to the frequency support characteristics of the wind turbine can be quickly determined, thereby reducing the possibility of primary and secondary drops in system frequency.

[0054] In this embodiment, in step S1, the wind speed is measured in real time, and the wind turbines with frequency modulation capability in the wind farm are determined according to the wind speed, and the wind turbines with frequency modulation capability are divided into wind turbine groups with different wind speeds;

[0055] Wind turbines with frequency modulation capability meet the following conditions: the wind speed of the wind turbine in operation is greater than 6m / s and less than or equal to 12m / s; the relationship between the wind speed and operating characteristics of the wind turbine is shown in the figure below: Figure 2 As shown, extremely low wind speed refers to a wind speed of less than or equal to 6m / s; low wind speed refers to a wind speed greater than 6m / s and less than or equal to 11m / s; medium wind speed refers to a wind speed greater than 11m / s and less than or equal to 12m / s; high wind speed refers to a wind speed greater than 12m / s;

[0056] Since the rotor of a wind turbine with a wind speed lower than 6m / s (extremely low wind speed) can only maintain the optimal speed, the rotor kinetic energy is insufficient to participate in frequency modulation; while the output of a wind turbine with a wind speed greater than 12m / s (high wind speed) reaches the rated power, it does not participate in frequency modulation because it cannot exceed the limit. Through the above method, the wind turbines that can participate in frequency modulation can be accurately determined.

[0057] Wind turbines with frequency modulation capability (wind speed greater than 6m / s and less than or equal to 12m / s) are divided into wind turbine groups with different wind speeds. The specific division is based on experience. For example, wind turbines with wind speed greater than 6m / s and less than or equal to 7m / s are divided into one wind turbine group; wind turbines with wind speed greater than 7m / s and less than or equal to 8m / s are divided into one wind turbine group, and so on. The last wind turbine group includes wind turbines with wind speed greater than 11m / s and less than or equal to 12m / s. You can also divide Wind turbines with wind speeds greater than 6m / s and less than or equal to 6.5m / s are divided into one wind turbine group, wind turbines with wind speeds greater than 6.5m / s and less than or equal to 7.5m / s are divided into one wind turbine group, wind turbines with wind speeds greater than 7.5m / s and less than or equal to 8.5m / s are divided into one wind turbine group, and so on. The last wind turbine group includes wind turbines with wind speeds greater than 11.5m / s and less than or equal to 12m / s. The specific division method is divided according to experience or demand. By dividing wind turbines with similar wind speeds into one wind turbine group, it is easy to calculate and control.

[0058] In this embodiment, in step S2, the actual additional energy E of the wind turbine is calculated based on the total kinetic energy released by the wind turbine and the wind energy loss. f , the actual additional energy of the wind turbine Ef It is the data used to measure the frequency regulation capability of wind turbines. The greater the actual additional energy of a wind turbine, the stronger its frequency regulation capability.

[0059] The process of wind turbine parameter system frequency regulation is as follows Figure 3 As shown in the figure, the total kinetic energy released by the decrease in rotor speed is the area of ​​ABCD (S1+S2), the actual additional energy generated by the frequency regulation of the wind turbine is S1, ABCDEF is the change trajectory of the active power output of the wind turbine, ABCD is the frequency support stage, the wind energy loss caused by the reduction in wind energy utilization coefficient due to the decrease in speed corresponds to the area S2, and EF is the rotor speed recovery stage;

[0060] The actual additional energy E of wind turbines f Calculated by the following formula:

[0061]

[0062] Among them, E k It represents the total kinetic energy released by the wind turbine rotor when the speed drops, E w It represents the wind energy loss caused by the decrease of wind energy utilization coefficient due to the decrease of rotor speed, H w represents the inertia time constant, ω0 represents the initial speed of the wind turbine, k represents the rotor frequency modulation exit speed ω1 is k times the initial speed ω0, ΔT represents the frequency modulation duration, ΔP m Indicates the change in mechanical power.

[0063] Since the integral of the mechanical power change over time is difficult to obtain analytically, the area approximation calculation method is used to simplify the integral into the area of ​​a triangle, thereby simplifying the calculation.

[0064] Through the above method, the frequency regulation capabilities of different wind turbines can be determined, providing a basis for subsequent frequency regulation according to the frequency regulation capabilities.

[0065] In this embodiment, in step S3, according to the actual additional energy E f Determine the net increase in active output power ΔP of the wind turbine e The relationship with the frequency modulation duration ΔT;

[0066] The net increase of active output power of wind turbine is ΔP e The relationship with the frequency modulation duration ΔT is obtained by the following method:

[0067] Since the actual additional energy E of the wind turbine f The net increase of active output power of wind turbines ΔP e The following relationship exists:

[0068] E f=ΔP e ΔT (3.1)

[0069] Combining formulas (2.1) and (3.1), we can obtain the net increase in active output power of the wind turbine ΔP e The relationship with the frequency modulation duration ΔT is as follows:

[0070]

[0071] Among them, ΔP e It represents the net increase of active output power of wind turbine, H w represents the inertia time constant, ω0 represents the initial speed of the wind turbine, k represents the rotor frequency modulation exit speed is k times the initial speed ω0, ΔT represents the frequency modulation duration, ΔP m Indicates the change in mechanical power.

[0072] In this embodiment, since the wind turbine operates in the maximum power tracking mode at low wind speed, there is a corresponding relationship between the initial rotor speed and the wind speed, the wind energy loss E caused by the reduction of the wind energy utilization coefficient is w It can be simplified as a function of wind speed. Under medium wind speed, the rotor speed of the wind turbine is constant, that is, the initial speed before frequency modulation is constant. The wind energy loss E caused by the reduction of wind energy utilization coefficient is w It can be simplified as a function of wind speed, and the mechanical power change ΔP can be further expressed as m Simplified as a function of wind speed:

[0073] ΔP m Calculated by the following formula:

[0074]

[0075] Among them, P mopt represents the initial power of the wind turbine before frequency modulation, ρ represents the air density, π represents the circumference of a circle, R represents the radius of the wind turbine rotor, and v w Indicates wind speed, ΔC P Indicates the change in wind energy utilization coefficient.

[0076] In this embodiment, in step S4, the net increase of active output power of the wind turbine group ΔP is constructed. b The function L of the frequency modulation duration ΔT is related to the following formula:

[0077]

[0078] Where a represents the serial number of the wind turbine in the first wind turbine group, A represents the total number of wind turbines in the first wind turbine group, ΔT represents the frequency modulation duration, ΔP b,1 , ΔP b,2 and ΔPb,n They represent the net increase in active output power of the first, second and nth wind turbine groups, d represents the sequence number of the wind turbine group in the second wind turbine group, D represents the total number of wind turbine groups in the second wind turbine group, λ represents the weight coefficient, ΔP L represents the load disturbance power;

[0079] Among them, the frequency modulation duration of all wind turbines in the same wind turbine group is the same, and the net increase in active output power of the wind turbine group is obtained by adding the net increase in active output power of all wind turbines in the wind turbine group; It represents the net increase of active output power of the first wind turbine group;

[0080] Function L is transformed from objective function F and equality constraints;

[0081] The objective function F is:

[0082]

[0083] The equality constraints are:

[0084] ΔP b,1 +ΔP b,2 +…+ΔP b,n =ΔP total

[0085] Where N represents the total number of wind turbines, ΔP total Indicates the active power demand for system frequency regulation;

[0086] Function L is a Lagrangian function. Determining the Lagrangian function based on the objective function and the equality constraint function is a prior art and will not be described in detail here.

[0087] At the same time, the objective function F and the equality constraint are satisfied, which means that the sum of the net increase in active power output by all wind turbines is equal to the active power demand of the system frequency regulation; and the total output energy of all wind turbines is the minimum. Through the above method, the reasonable distribution of system frequency regulation power between wind turbines at different wind speeds can be designed.

[0088] In this embodiment, in step S5, the function L is solved according to the conditional extreme value to obtain the net increase ΔP of the active output power of the wind turbine group. b and the frequency modulation duration ΔT, wherein solving the function by conditional extreme value is a prior art and will not be described in detail here;

[0089] Frequency support characteristics: The relationship between frequency modulation duration and output power increment at different wind speeds is shown in the figure below: Figure 4As shown in the figure, when the speed drops to 0.7 times the steady-state speed, when the active output increment changes within the range of 0.01-0.1pu of the steady-state operating output power, the upper limit of the power increment output by the wind turbine with a lower wind speed is smaller than that of the wind turbine with a higher wind speed; when the speed of the wind turbine with a higher wind speed drops to the same degree, the change in output mechanical power is greater, resulting in that when the active output increment is low, the frequency regulation duration of the wind turbine with a high wind speed is shorter than that of the wind turbine with a low wind speed; therefore, the medium wind speed wind turbine performs short-term frequency regulation with a high power increment, which mainly plays a role in reducing the frequency change rate after the frequency event occurs; the low wind speed wind turbine performs long-term frequency regulation with a low power increment, which reduces the frequency deviation of the primary frequency regulation process; the output power consumption characteristics of wind turbines with different wind speeds are shown in the figure. Figure 5 As shown in the figure, when the output power increment per unit value is the same, the higher the wind speed, the higher the energy output by the wind turbine group.

[0090] By solving the function L through conditional extreme value, it can be ensured that the net increase of active output power of the wind turbine group obtained by solving ΔP b The frequency modulation duration ΔT is adapted to the output power increment and output power consumption of wind turbine groups with different wind speeds; and the reasonable distribution of system frequency modulation power among wind turbine groups with different wind speeds is achieved.

[0091] In this embodiment, in step S6, the net increase in active output power ΔP of the wind turbine group is determined. b Whether the frequency modulation duration ΔT meets the preset constraint conditions, if so, the net increase of active output power ΔP is output b and the frequency modulation duration ΔT; if not, the boundary value of the parameter that does not meet the preset constraint condition is substituted into step S5 until the preset constraint condition is met;

[0092] The default constraints are:

[0093]

[0094] Where τ represents the minimum frequency modulation duration, ΔT n,max Indicates the maximum frequency modulation duration of the nth wind turbine group, ΔT n,rec It represents the maximum time required for the power of the n-1th wind turbine to recover to 0.9 times the initial power of the frequency regulation, ΔP b,n,max Indicates the maximum net increase in active output power of the nth wind turbine group;

[0095] The frequency modulation duration of the wind turbine group that meets the preset constraint conditions should meet the following requirements: the greater the wind speed, the shorter the frequency modulation duration. Through the above method, it can be ensured that the minimum objective function and the frequency modulation duration are less than the maximum frequency modulation duration; and ΔT n -ΔT n-1 ≤ΔTn,rec It can ensure that the speed recovery time is sufficient to avoid the input power being insufficient to support the rotor speed recovery, thereby avoiding the reabsorption of a large amount of active power from the system, causing a shortage of system active power and a secondary drop in frequency.

[0096] In this embodiment, in step S7, when the wind farm needs active frequency support, the net increase ΔP of the active output power of the wind turbine group that meets the preset constraint conditions is b,n The frequency modulation active power command is input to the wind turbine group, and the frequency modulation is performed on wind turbine groups with different wind speeds at the same time, and the frequency modulation duration is executed to meet the preset constraint conditions. Through the above method, it is possible to exit the frequency modulation in order from high to low wind speeds, reducing the adverse effects of synchronous exit of the frequency modulation of the wind turbine group.

[0097] The specific implementation process of the embodiment of the present invention is as follows:

[0098] A wind turbine frequency modulation system model was built based on the matlab / Simulink simulation platform. Figure 6 As shown in the figure, the voltage level is 35kV and the total capacity is 26MW. It includes three 2MW doubly-fed wind turbines and one 20MW synchronous generator. During the simulation, the wind speeds of the wind turbines are set to 9m / s, 10m / s and 11m / s respectively.

[0099] At T = 4s, taking the sudden load increase of 0.5MW in the simulation system model as an example, the calculated active power output increment and frequency regulation duration of each unit are shown in Table 1;

[0100] Wind turbines Wind speed (m / s) <![CDATA[ΔP e (MW)]]> ΔT(s) DFIG1 9 0.12 22.34 DFIG2 10 0.17 19.87 DFIG3 11 0.21 18.54

[0101] Table 1 Calculation results of active power output increment and frequency modulation duration of each unit

[0102] The simulation results are as follows Figure 7 As shown in Figure 2, when there is no active support strategy, the lowest system frequency is 49.58 Hz. Figure 7 The proposed strategy is the wind farm centralized primary frequency regulation coordinated control method provided by this application), the system frequency change rate is also reduced, and the minimum frequency rises to 49.62Hz. Figure 8 As shown in Figure 2, when the wind turbines exit the frequency modulation at the same time, the lowest point of the second drop of the system frequency is 49.61Hz, which is greater than the lowest point of the first drop of the frequency. After adopting the proposed strategy ( Figure 8 The strategy proposed in is the centralized primary frequency regulation coordinated control method for wind farms provided in this application), and the lowest point of the second drop in system frequency is 49.64 Hz, which is lower than the lowest point of the first drop in frequency.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A wind farm centralized primary frequency regulation coordinated control method, characterized by: The following steps are involved: S1. Real-time measurement of wind speed, determination of wind turbines with frequency modulation capability in the wind farm according to the wind speed, and division of wind turbines with frequency modulation capability into wind turbine groups with different wind speeds; S2. Calculate the actual additional energy E of the wind turbine according to the total kinetic energy released by the wind turbine and the wind energy loss f ; S3. According to the actual increase in energy E f Determine the net increase in active output power ΔP of the wind turbine e The relationship with the frequency modulation duration ΔT; S4. Based on step S3, construct the net increase ΔP of the active output power of the wind turbine group b Function L of the frequency modulation duration ΔT; S5. Solve the function L according to the conditional extreme value to obtain the net increase of active output power of the wind turbine group ΔP b and FM duration ΔT; S6. Determine the net increase ΔP of the active output power of the wind turbine group obtained by solving b Whether the frequency modulation duration ΔT meets the preset constraint conditions, if so, the net increase of active output power ΔP is output b and the frequency modulation duration ΔT; if not, the boundary value of the parameter that does not meet the preset constraint condition is substituted into step S5 until the preset constraint condition is met; S7. When the wind farm needs active frequency support, the wind farm centrally controls each wind turbine group to achieve a net increase in active output power ΔP that meets the preset constraints. b And the frequency modulation duration ΔT is used for active frequency support.

2. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 1, characterized in that: In step S2, the actual additional energy E of the wind turbine is f Calculated by the following formula: Among them, E k Represents the total kinetic energy released by the wind turbine, E w Represents wind energy loss, H w represents the inertia time constant, ω0 represents the initial speed of the wind turbine, k represents the multiple of the rotor speed when it exits frequency modulation and the initial speed, ΔT represents the frequency modulation duration, ΔP m Indicates the change in mechanical power.

3. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 2, characterized in that: In step S3, the net increase in active output power of the wind turbine generator set is ΔP e The relationship with the frequency modulation duration ΔT is obtained by the following method: Since the actual additional energy E of the wind turbine f The net increase of active output power of wind turbines ΔP e The following relationship exists: E f =ΔP e ΔT (3.1) Combining formulas (2.1) and (3.1), we can obtain the net increase in active output power of the wind turbine ΔP e The relationship with the frequency modulation duration ΔT is as follows: Among them, ΔP e It represents the net increase of active output power of wind turbine, H w represents the inertia time constant, ω0 represents the initial speed of the wind turbine, k represents the multiple of the rotor speed when it exits frequency modulation and the initial speed, ΔT represents the frequency modulation duration, ΔP m Indicates the change in mechanical power.

4. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 3 is characterized in that: ΔP m Calculated by the following formula: Among them, P mopt represents the initial power of the wind turbine before frequency modulation, ρ represents the air density, π represents the circumference of a circle, R represents the radius of the wind turbine rotor, and v w Indicates wind speed, ΔC P Indicates the change in wind energy utilization coefficient.

5. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 3 is characterized in that: In step S4, the net increase in active output power of the wind turbine group is ΔP b The relationship between the function L and the frequency modulation duration ΔT is as follows: Where a represents the serial number of the wind turbine in the first wind turbine group, A represents the total number of wind turbines in the first wind turbine group, ΔT represents the frequency modulation duration, ΔP b,1 , ΔP b,2 and ΔP b,n They represent the net increase in active output power of the first, second and nth wind turbine groups, d represents the sequence number of the wind turbine group in the second wind turbine group, D represents the total number of wind turbine groups in the second wind turbine group, λ represents the weight coefficient, ΔP L represents the load disturbance power; The frequency modulation duration of all wind turbines in the same wind turbine group is the same; the net increase in active output power of the wind turbine group is obtained by adding the net increase in active output power of all wind turbines in the wind turbine group.

6. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 5, characterized in that: In step S6, the preset constraint conditions are: Where τ represents the minimum frequency modulation duration, ΔT n,max Indicates the maximum frequency modulation duration of the nth wind turbine group, ΔT n,rec It represents the maximum time required for the power of the n-1th wind turbine to recover to 0.9 times the initial power of the frequency regulation, ΔP b,n,max It represents the maximum net increase in active output power of the nth wind turbine group.

7. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 6, characterized in that: In step S7, when the wind farm needs active frequency support, the net increase ΔP of the active output power of the wind turbine group that meets the preset constraint conditions is b,n It is input as a frequency modulation active power instruction to the wind turbine group, and the frequency of wind turbine groups with different wind speeds is modulated at the same time, and is executed until the frequency modulation duration meets the preset constraint conditions.

8. The method for coordinated control of centralized primary frequency regulation in a wind farm according to claim 1, characterized in that: In step S1, the wind turbine generator set with frequency modulation capability meets the following conditions: the wind speed of the wind turbine generator set in operation is greater than 6 m / s and less than or equal to 12 m / s.

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