CN111900744A - Method for coordinating and controlling DFIG (distributed feed Induction Generator) participating in machine network under large-scale new energy grid connection - Google Patents

Abstract

The application provides a method for coordinating and controlling DFIG participation in a machine network under large-scale new energy grid connection, and provides a thought for setting the operation condition of a wind turbine generator according to wind speed sections, a virtual inertia control link and a variable droop control coefficient link based on the working condition are added on the basis of a traditional DFIG control strategy, and meanwhile, the value of a droop control parameter is subjected to optimization analysis, and the droop control coefficient values under different working conditions are set, so that the wind turbine generator can actively respond to the system inertia in each wind speed section; the method is characterized in that the comprehensive control method comprises the steps of setting a machine network coordination control strategy adaptive to working conditions by combining 4 modes of droop control, virtual inertia control, overspeed load shedding and variable pitch control under different working conditions according to the set DFIG operating working conditions, so that the fan can carry out frequency modulation more fully, the requirement of power grid frequency adjustment can be met, and the wind curtailment generated by fan load shedding standby can be reduced as much as possible.

Description

Method for coordinating and controlling DFIG (distributed feed Induction Generator) participating in machine network under large-scale new energy grid connection

Technical Field

The application relates to the technical field of wind power generation frequency modulation control, in particular to a large-scale new energy grid-connected DFIG (doubly Fed induction generator) participating machine grid coordination control method.

Background

With the rapid development of energy industry, in recent years, the popularization of sustainable and environment-friendly energy has become an important issue. The new energy permeability in the power grid increases year by year. Different from traditional energy sources such as thermal power, hydropower and the like, wind power generation which accounts for a large proportion in new energy sources has time pulsation and uncertainty. The rotating speed of the generator rotors of the steam turbine and the water turbine is coupled with the system frequency, so that the power grid coordination capability is better. And an inversion process exists in the wind turbine generator, so that the wind turbine generator presents a non-inertia state to a power grid end. Meanwhile, wind power is operated by adopting a maximum power point tracking strategy, and reserved standby power does not participate in system frequency modulation. When a fault or load sudden change occurs in the power system, the new energy unit cannot provide power support, and large-scale new energy grid connection can affect the aspects of stable power grid frequency, stable power output and the like.

Therefore, for the problem of machine-network coordination after new energy grid connection, the new energy electric field is required to have the frequency modulation capability capable of participating in machine-network coordination operation as a conventional electric field by parts of domestic and foreign power grids.

Disclosure of Invention

The application provides a method for coordinating and controlling DFIG participation in a machine network under a large-scale new energy grid-connected mode, and provides a thought for setting the operation condition of a wind turbine generator according to a wind speed section, a virtual inertia control link and a variable droop control coefficient link based on the condition are added on the basis of a traditional DFIG control strategy, so that the DFIG responds to the frequency change of a system to some extent, meanwhile, the value of a droop control parameter is subjected to optimization analysis, and 4 modes of droop control, virtual inertia control, overspeed load shedding and variable pitch control are combined to cooperate with each other under different conditions according to the set DFIG operation condition.

The technical scheme adopted by the application is as follows:

a method for coordinating and controlling DFIG participating in computer network under large-scale new energy networking comprises the following steps:

determining the current wind speed Vw of the DFIE;

a fixed value is taken for the virtual inertia coefficient, and a droop control coefficient K is determined according to the current operation condition_pD% of load shedding coefficient, control action and DFIG active output under limited power; the operation working conditions comprise a low wind speed section, a medium wind speed section and a high wind speed section;

if the current wind speed Vw is in a low wind speed section, calculating a droop control coefficient K of the low wind speed section_p1And a load shedding factor d_lPercent, adopting overspeed load shedding control action, and DFIG active power delta P under limited power₁；

If the current wind speed Vw is in the middle wind speed section, calculating the droop control coefficient K of the middle wind speed section_p2And a load shedding factor d_mPercent, adopting overspeed load shedding and variable pitch control action, and DFIG active power delta P under limited power₂；

If the current wind speed Vw is in a high wind speed section, calculating a droop control coefficient K of the high wind speed section_p3And a load shedding factor d_hPercent, adopting variable pitch control action, and DFIG active power delta P under limited power₃；

And determining the active power delta P input into the power grid by the DFIG according to the load reduction coefficient of the operation condition.

Further, the wind speed range of the low wind speed section is V_{Cutting into}-V_W1The wind speed range of the middle wind speed section is V_W1-V_W2The wind speed range of the high wind speed section is V_W2-V_{Cutting out}(ii) a The V is_W1At the dividing point of medium and low wind speeds, the V_W2At the dividing point of medium and high wind speed, the V_{Cutting into}For cutting into the wind speed, V_{Cutting out}To cut out the wind speed.

Further, if the current wind speed Vw is in a high wind speed section, the rotating speed of the wind wheel is controlled by adopting a variable pitch, and when the upper limit value of the rotating speed of the wind wheel is 1.2pu, the standby rotational kinetic energy participates in primary frequency modulation.

Further, calculating the droop control coefficient K under different wind speed sections_pThe maximum value mathematical model is as follows:

in the formula, P_mec,maxIs the maximum mechanical power,. DELTA.f_bandΔ f reaches the limit deviation value, Δ E, allowed by the system_kaFor maximum available rotational kinetic energy, T_fFor duration of primary modulation,. DELTA.f_sIs the amount of frequency change, K_dIs the virtual inertia coefficient, V_wFor the current wind speed, d% is the load shedding factor.

Further, in the case of considering only power fluctuation, the maximum value mathematical model of the droop control coefficient may be simplified as:

in the formula, P_mec,maxIs the maximum mechanical power,. DELTA.f_bandIs that Δ f reaches the limit deviation value, K, allowed by the system_dIs the virtual inertia coefficient, K_PIs the droop control coefficient, Δ E_kaFor maximum available rotational kinetic energy, d% is the load shedding factor.

The technical scheme of the application has the following beneficial effects:

(1) considering a variable droop control coefficient method under the current wind speed of a fan, and setting droop control coefficient values under different working conditions, so that a wind turbine generator can actively respond to system inertia at each wind speed section;

(2) by setting the operation condition of the DFIG, a machine-network coordination control strategy adaptive to the operation condition is formulated, so that the frequency of the fan is modulated more fully, the requirement of adjusting the frequency of a power network can be met, and the waste wind generated by fan load reduction standby can be reduced as much as possible.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1-a is a schematic diagram of a conventional control method;

FIG. 1-b is a schematic diagram of a control method provided in an embodiment of the present application;

FIG. 2 is a schematic diagram illustrating the division of DFIG operating conditions provided by the embodiment of the present application;

fig. 3 is a method for coordinating and controlling a network unit according to an embodiment of the present disclosure;

fig. 4 is a structural diagram of a simulation system provided in the embodiment of the present application;

FIG. 5 is a sample wind speed for use in the simulation system provided by an embodiment of the present application;

FIG. 6 is a comparison of a conventional control method and a control method provided by an embodiment of the present application with respect to DFIG rotor speed;

FIG. 7 is a comparison between the conventional control method and the control method provided in the embodiments of the present application in the case of DFIG active power;

FIG. 8 is a comparison of a conventional control method with a control method provided by an embodiment of the present application in terms of grid frequency;

FIG. 9 shows a control method provided in this embodiment of the present application when different K is used_pComparing the active power condition of the lower DFIG;

FIG. 10 shows an embodiment of the present application in which the control method is implemented with different K_pAnd comparing the lower grid frequency.

Detailed Description

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following examples do not represent all embodiments consistent with the present application. But merely as exemplifications of systems and methods consistent with certain aspects of the application, as recited in the claims.

Referring to fig. 1-a, a schematic diagram of a conventional control method; FIG. 1-b is a schematic diagram of a control method provided in an embodiment of the present application; FIG. 2 is a schematic diagram illustrating the division of DFIG operating conditions provided by the embodiment of the present application; fig. 3 is a method for coordinating and controlling a network unit according to an embodiment of the present disclosure; fig. 4 is a structural diagram of a simulation system provided in the embodiment of the present application; FIG. 5 is a sample wind speed for use in the simulation system provided by an embodiment of the present application; FIG. 6 is a comparison of a conventional control method and a control method provided by an embodiment of the present application with respect to DFIG rotor speed; FIG. 7 is a comparison between the conventional control method and the control method provided in the embodiments of the present application in the case of DFIG active power; FIG. 8 is a comparison of a conventional control method with a control method provided by an embodiment of the present application in terms of grid frequency; FIG. 9 is a comparison of the DFIG active power conditions under different Kp conditions by the control method provided by the embodiment of the present application; fig. 10 is a comparison of grid frequencies at different Kp according to the control method provided in the embodiment of the present application.

At present, the control strategy for a large-scale variable-pitch doubly-fed wind generating set is as follows: keeping the pitch angle of the wind turbine generator constant below a rated wind speed, and enabling the wind turbine generator to operate at the optimal inter-blade speed ratio by adjusting the rotating speed of a generator to realize maximum wind energy tracking control; above the rated wind speed, the conventional control strategy is shown in fig. 1-a by pitch angle adjustment to make the generator output power constant. The application adds delta f and

two loops as shown in fig. 1-b. Meanwhile, on the basis, the wind speed fluctuation condition and the power grid frequency variation are introduced into the droop control K_pAmong values, variable coefficient droop control is adopted.

Referring to fig. 1-b, the frequency fluctuation condition of the power grid end is introduced into a power control link, the active output of the DFIG is changed when the system frequency is disturbed, and the total output of the wind turbine generator is active

The additional active power output is P.

In the formula, K_dIs a virtual coefficient of inertia, K_pIs the droop control coefficient.

The additional control loop allows the rotor to absorb or release kinetic energy in response to changes in the grid frequency, providing power support in the event of fluctuations in the grid frequency. By adjusting K_dAnd K_pThe value of (A) is used for controlling the size of the kinetic energy absorbed or released by the rotor.

Droop control coefficient K_pThe value of (A) has important influence on the frequency modulation performance of the DFIG, and at present, the value of (A) is mostly on K_pAnd the value is fixed, so that the DFIG under each working condition can not be ensured to have good frequency modulation capability. Therefore, K is determined according to the actual operation condition of DFIG_pIt is important to make the adjustment.

Based on a primary frequency modulation control strategy of setting, dynamic K is adopted_pTaking values; virtual inertia coefficient K_dOf equal importance, different K_dThe value has great influence on the strength of frequency response, when K is_dThe transient frequency response of DFIG is enhanced when taking a larger value, and the electromagnetic power P_eWill be larger and be in the mechanical power P of the wind wheel rotor of the same shafting_mecWill also increase which will result in the rotor slowing down to the point where it is difficult to recover after the frequency modulation process has ended.

If K is_dAt smaller values, the transient frequency response of the DFIG is reduced. Except by virtualThe sag control coefficient K is adjusted in addition to the rotor kinetic energy of the quasi-inertia release_pRelease of the rotor can also be achieved.

Due to the difficulty in realizing simultaneous regulation and control of K_pAnd K_dAnd the frequency steady state is more important in the machine network coordination control process, the invention is to K_dTaking a fixed value, and aligning K according to different working conditions of DFIG operation_pAnd taking a variation value.

The core of the variable droop coefficient method provided by the application is that the frequency modulation is carried out by releasing the rotational kinetic energy stored by the rotor, and the partial rotational kinetic energy is in a reasonable range when K is used_pAnd (3) taking an extreme value, wherein the DFIG can still keep stable operation, and the mathematical model is as follows:

in the formula,. DELTA.E_kaFor maximum available rotational kinetic energy, T_fIs the primary frequency modulation duration, Δ f is the frequency variation, f is the system frequency, P_mecIs mechanical power, P_mec0For initial mechanical power, in conventional systems, T_fGenerally not exceeding 30 s.

From the energy conservation analysis in equation (3), the model is simplified due to the complexity of its integral calculation. The first simplification is to perform a simplified analysis in terms of power when the system frequency changes tend to be stable. If the delta f reaches the allowable limit deviation value delta f of the system_bandThe maximum available rotational kinetic energy and other reserve power f will be at T_fAnd (4) releasing. The formula (3) can be simplified into

It is noted that the wind speed does not fluctuate much on the time scale of the primary frequency modulation. Under a certain working condition, the maximum mechanical power of the DFIG is

In the formula, P_mec,maxIs the maximum mechanical power, rho is the air density, R is the wind wheel sweeping radius, beta is the impeller pitch angle, C_pFor the wind energy utilization, λ_optFor optimum tip speed ratio, λ_iIs an intermediate variable, ω_baseIs a reference rotational speed, G is the gear box drive coefficient, f_nIs the nominal frequency.

In the initial operating state, the DFIG is operated at an unloaded speed. In this primary control strategy, the load shedding control is achieved by overspeed load shedding and pitch control. Omega_delIs the wind wheel speed of the deloading operation. If V_wAnd d% give, omega_baseAnd ω_mpptCan be solved by the formula (5) and has the maximum available rotational kinetic energy of

In order to prevent the wind wheel rotating speed from being lower than omega in DFIG operation_mpptThe rotational kinetic energy is not fully released, and n% of the rotational kinetic energy is used as a safety margin, i.e.

ΔE_ka＝(1-n％)ΔE_km(7)

Under the constraint of an objective function

In the formula (f)_TfIs T_fSystem frequency of time, f₀Is the system initial frequency, Δ f_sIs the steady state frequency offset.

In summary, in practical applications, V is defined in conjunction with the DFIG operation conditions defined herein_w1Before the starting stage of the DFIG, in order to ensure that the wind turbine generator has good starting performance, droop control is not involved, and K is used at the moment_pWhen the value is 0, the combination formula (3) can obtain K under different working conditions_pThe value is shown in formula (9).

In practiceK_pThe wind speed characteristics are considered in the optimization. If K is adjusted in real time according to the wind speed_pDue to fluctuations in wind speed, K_pWill fluctuate rapidly within a small range. On the one hand, real-time small-range varying K_pThe influence of the value on the primary frequency modulation capability of the unit is not great. On the other hand, the wind speed changes almost all the time, which has high requirements on the sensitivity of the DFIG internal regulation signal. Therefore, K does not need to be adjusted in real time according to the wind speed_p. However, the fixed K is still adopted when the wind speed changes greatly_pThe DFIG is separated from the power grid when the wind speed is too high, and the powerful primary frequency modulation capability cannot be provided when the wind speed is too low.

To sum up, K_pIt is required to change according to the wind speed, rather than performing a real-time tracking transformation. In practical application, the operation condition of the wind turbine generator can be set into a plurality of sections, and K under corresponding conditions is calculated_pThe value is obtained.

Determining the current wind speed V of the DFIE_W. The wind turbine generator set is not constant in operation condition due to the pulsation of wind resources, and the wind speed V is_WThe mechanical power of the DFIG has a significant influence, and the mechanical power directly affects the active power.

V_W1For the dividing point of medium and low wind speed, V is defined_W2Is the dividing point of medium and high wind speed, V_{Cutting into}Position cut-in wind speed, V_{Cutting out}And cutting the wind speed.

Referring to fig. 2, the present application will divide the operating condition of the fan into low wind speed sections L_mMiddle wind velocity segment M_mHigh wind speed section H_m. Low wind speed section L_mIs in a wind speed range of V_{Cutting into}-V_W1Middle wind velocity segment M_mIs in a wind speed range of V_W1-V_W2High wind speed section H_mIs in a wind speed range of V_W2-V_{Cutting out}(ii) a Definition V_W1Is the dividing point of medium and low wind speed; when operating at V_W2At the same time, the rotating speed of the wind wheel reaches the rated upper limit of 1.2 pu.

A fixed value is taken for the virtual inertia coefficient and the current wind speed V is used_WThe wind speed section is used for determining a droop control coefficient, a load shedding coefficient and a control action.

The virtual inertia control has the characteristics of transient state and small time scale, and when power fluctuation occurs to the power grid, the DFIG added with the control strategy can provide stable support for the power grid by feeding power to the power grid or absorbing excess power of the power grid.

If the current wind speed V_WIn a low wind speed section L_mWind speed range V of_{Cutting into}-V_W1And when the wind wheel is in the inner stage, calculating the droop control coefficient and the load shedding coefficient of the low wind speed section, wherein the pitch angle of the fan is 0 degree, and the load shedding can be realized by increasing the rotating speed of the wind wheel.

If the current wind speed V_WIn the medium wind speed section M_mWind speed range V of_W1-V_W2When the wind wheel rotating speed reaches the maximum value, the load reduction can not be realized by further increasing the rotating speed, and the variable pitch control mechanism intervenes. The DFIG has a rapid frequency response characteristic, can rapidly release active power for load shedding standby, and effectively reduces fatigue load of a wind wheel while ensuring primary frequency modulation at a full wind speed section; the DFIG can continuously participate in primary frequency modulation by means of droop control; the control system of the DFIG achieves variable speed operation, with rotor speeds that can be operated over a relatively wide range.

If the current wind speed V_WAt high wind speed H_mWind speed range V of_W2-V_{Cutting out}And (4) calculating a droop control coefficient and a load shedding coefficient of the high wind speed section, and controlling the rotating speed of the wind wheel by adopting a variable pitch. When the DFIG operates in a high-speed wind section, the rotating speed of a wind wheel can reach 1.2pu, and in a low-speed wind section L_mThe rotor speed can reach 0.7pu, which means that at most 65.97% of the rotational kinetic energy can be used as power reserve, a conventional unit operates in the range of 0.95-1.0pu, and a DFIG unit can normally provide 9.75% of the rotational mechanical power as frequency modulated reserve. Therefore, when the rotating speed of the wind wheel is lower than 1.2pu, the standby rotating kinetic energy can participate in primary frequency modulation.

Referring to fig. 3, a specific flow of the method for cooperative control of the machines and networks of the DFIG participating in large-scale new energy grid connection provided by the embodiment of the present application is as follows:

measuring the current wind speed V_WJudging the current working condition;

when V is_{Cutting out}<V_WOr V_W<V_{Cutting into}Time V_{Cutting into}>V_WOr V_W>V_{Cutting out}And when the fan does not run, the unit does not carry out the machine network coordination control action:

in the low wind speed section L_mIn time, overspeed load shedding is carried out, and the load shedding coefficient is determined to be d_lPercent, droop control coefficient is K_P1And the virtual inertia control coefficient is taken as K_dActive power delta P of DFIG under limited power₁；

In the middle velocity stage M_mIn the process, a control mode of combining overspeed load shedding and variable pitch control is adopted, and the load shedding coefficient is calculated to be d_mPercent, droop control coefficient is K_P2And the virtual inertia control coefficient is taken as K_dActive power delta P of DFIG under limited power₁；

In the high wind speed section H_mThe method only adopts a variable pitch control mode to carry out load shedding standby, and calculates the load shedding coefficient as d_hPercent, droop control coefficient is K_P3And the virtual inertia control coefficient is taken as K_dActive power delta P of DFIG under limited power₁。

And determining the active power delta P input into the power grid by the DFIG according to the load shedding coefficient of the operation condition.

The following describes the application effect of the present invention in detail with reference to simulation.

In order to verify the effectiveness of the DFIG participating in the machine network coordination control strategy, PSASP software is utilized to combine certain power grid data to perform simulation analysis, and the power grid power generation capacity is 587MVA, wherein wind power installation machine 160MVA and photovoltaic 50MVA, and the rest are medium and small-scale hydroelectric plants and loads 476 MVA. Wind power permeability reaches 33.6%, photovoltaic permeability reaches 10.5%, and a structure diagram of the wind power field is shown in fig. 4, wherein a wind power field is located in the southeast, a photovoltaic electric field is located in the northeast, a main load is a certain city region in the west, and a tide flow direction is from the east to the west.

The wind speed sample is shown in fig. 5, the wind speed fluctuation is large at 12s, 30s and 50s, and 100MW negative is switched in the middle and the west of the power grid at 40sLoad shedding coefficient d under each working condition is set_h％＝12％、d_m％＝10％、d_lPercent is 7%, and the high, medium and low working conditions K are corresponding to the formulas (4) to (9)_pRespectively take K_p1＝4.23、K_p2＝5.67、K_p3The virtual inertia coefficient takes a fixed value K, 8.34_d5. By adopting the machine network coordination control strategy provided by the application, the obtained change situation of the rotating speed of the wind wheel, the change situation of the active power output by the wind turbine generator and the change situation of the frequency of the power grid are shown in fig. 6-8.

The double-fed wind turbine generator adopting the control method can carry out load shedding operation under various working conditions, reduces the waste wind, also considers the primary frequency modulation of the power grid, and improves the coordination of the power grid to the maximum extent.

As can be seen from fig. 6, before 40s of load shear, the rotor speed is higher after the coordinated control strategy of the present invention is applied compared to the conventional control strategy, because at this time, overspeed load shedding is performed, and the reserve power is reserved. After 40s of load shear, the wind turbine adopting the traditional control strategy has no response to the power shortage of the system, the wind turbine adopting the network coordination control strategy has response, and the rotor decelerates to release mechanical kinetic energy on the rotating shaft system.

Fig. 7 can effectively prove the above point, the wind turbine generator with the additional grid coordination control strategy can release the standby power after the transient fluctuation when the system has power shortage, and the wind turbine generator adopting the traditional control strategy does not provide additional power for the system.

As can be seen from fig. 8, since the virtual inertia control and the droop control of the wind turbine generator can respectively respond to the change rate of the system frequency and the system frequency deviation, when the system frequency drops, the control speed drops, and the kinetic energy of the rotor is released, when the wind turbine generator in the conventional control mode participates in frequency modulation, the frequency drops to 49.818Hz, while when the wind turbine generator with the grid coordination control strategy of the present invention participates in frequency modulation, an additional active support is provided, the system frequency is raised back to 49.839Hz, and at this time, the wind turbine generator provides an additional 0.13pu active output.

Adopting the simulation model, the input wind speed is taken as a constant value12m/s, 100MW load is increased in the middle and the west of the power grid at 40s, and K is calculated_pDifferent values are taken for simulation. Before and after the load is switched, the active output condition of the DFIG and the frequency fluctuation condition of the power grid are shown in FIGS. 9 and 10.

The 40s load is increased, the active output of the DFIG and the grid frequency are changed and disturbed, the active output of the DFIG is increased under the combined action of an additional inertia link and a droop control link on a DFIG control system, power support is provided, the grid frequency is recovered stably, and when the K is used, the DFIG can be used for increasing the active output of the DFIG and providing power support_pWhen the frequency is equal to 4, the output active power of the DFIG is increased to 0.75pu, and the system frequency drop amount is 0.041 Hz. When K is_pWhen the frequency is 6, the output active power of the DFIG is increased to 0.76pu, and the drop amount of the system frequency is 0.035 Hz. When K is_pAt 8, the output active power of the DFIG is increased to 0.78pu, and the system frequency drop amount is 0.029 Hz. When the power grid load is disturbed, K is increased_pThe value is effective to suppress frequency dips while the active power provided by the DFIG is also increased.

Different droop control coefficients participate in the grid coordination control, the frequency drop degree of the system is different near the load cut-off point because the active power provided by the DFIG is different, the value of the droop coefficient determines the depth of the DFIG participating in the grid coordination control, and the result is that the wind power permeability in the system is 33.6%.

According to the invention, on the idea of the coordinated control of the machine network, the operation condition of the wind turbine generator is set, different control strategies are formulated according to different working conditions, droop control coefficient values are optimized, and the effectiveness of the coordinated control strategy of the machine network provided by the invention is verified by adopting a variable wind speed sample and actual power grid data under the whole working conditions.

The embodiments provided in the present application are only a few examples of the general concept of the present application, and do not limit the scope of the present application. Any other embodiments extended according to the scheme of the present application without inventive efforts will be within the scope of protection of the present application for a person skilled in the art.

Claims (5)

1. A method for coordinating and controlling DFIG participating in computer network under large-scale new energy grid connection is characterized by comprising the following steps:

determining the current wind speed Vw of the DFIE;

for virtual inertia coefficient K_dTaking a fixed value, and determining a droop control coefficient K according to the current operation condition_pD% of load shedding coefficient, control action and DFIG active output under limited power; the operation working conditions comprise a low wind speed section, a medium wind speed section and a high wind speed section;

if the current wind speed Vw is in a low wind speed section, calculating a droop control coefficient K of the low wind speed section_p1And a load shedding factor d_lPercent, adopting overspeed load shedding control action, and DFIG active power delta P under limited power₁；

If the current wind speed Vw is in the middle wind speed section, calculating the droop control coefficient K of the middle wind speed section_p2And a load shedding factor d_mPercent, adopting overspeed load shedding and variable pitch control action, and DFIG active power delta P under limited power₂；

If the current wind speed Vw is in a high wind speed section, calculating a droop control coefficient K of the high wind speed section_p3And a load shedding factor d_hPercent, adopting variable pitch control action, and DFIG active power delta P under limited power₃；

And determining the active power delta P input into the power grid by the DFIG according to the load reduction coefficient of the operation condition.

2. The large-scale new energy grid-connected DFIG (doubly Fed Induction Generator) participating grid coordination control method according to claim 1, wherein the wind speed range of the low wind speed section is V_{Cutting into}-V_W1The wind speed range of the middle wind speed section is V_W1-V_W2The wind speed range of the high wind speed section is V_W2-V_{Cutting out}(ii) a The V is_W1At the dividing point of medium and low wind speeds, the V_W2At the dividing point of medium and high wind speed, the V_{Cutting into}For cutting into the wind speed, V_{Cutting out}To cut out the wind speed.

3. The large-scale new energy grid-connected DFIG participating grid-connected coordination control method according to claim 1, wherein if the current wind speed Vw is in a high wind speed section, the wind turbine speed is controlled by pitch variation, and when the upper limit value of the wind turbine speed is 1.2pu, the backup rotational kinetic energy participates in primary frequency modulation.

4. The large-scale new energy grid-connected DFIG (doubly fed induction generator) participating grid coordination control method according to claim 1, wherein the droop control coefficient K is calculated under different wind speed sections_pThe maximum value mathematical model is as follows:

in the formula, P_mec,maxIs the maximum mechanical power,. DELTA.f_bandΔ f reaches the limit deviation value, Δ E, allowed by the system_kaFor maximum available rotational kinetic energy, T_fFor duration of primary modulation,. DELTA.f_sIs the amount of frequency change, K_dIs the virtual inertia coefficient, V_wFor the current wind speed, d% is the load shedding factor.

5. The method for coordination control over the DFIG participating in the grid-connected unit under the large-scale new energy grid-connected condition according to claim 1, wherein under the condition that only power fluctuation is considered, a maximum value mathematical model of the droop control coefficient can be simplified as follows:

in the formula, P_mec,maxIs the maximum mechanical power,. DELTA.f_bandIs that Δ f reaches the limit deviation value, K, allowed by the system_dIs the virtual inertia coefficient, K_PIs the droop control coefficient, Δ E_kaFor maximum available rotational kinetic energy, d% is the load shedding factor.

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