CN117117897A

CN117117897A - Wind farm control method and device for multi-terminal flexible direct system grid connection

Info

Publication number: CN117117897A
Application number: CN202311058483.6A
Authority: CN
Inventors: 伍双喜; 刘洋; 武志韬; 刘昊宇; 朱誉
Original assignee: Guangdong Power Grid Co Ltd; Electric Power Dispatch Control Center of Guangdong Power Grid Co Ltd
Current assignee: Guangdong Power Grid Co Ltd; Electric Power Dispatch Control Center of Guangdong Power Grid Co Ltd
Priority date: 2023-08-21
Filing date: 2023-08-21
Publication date: 2023-11-24

Abstract

The invention discloses a wind farm control method and device for multi-terminal flexible direct system grid connection, wherein the method comprises the following steps: when frequency disturbance occurs in an alternating current system, each flexible direct current converter is set to be in a constant power mode; when the direct-current side capacitor of the converter station cannot enable the frequency to return to the frequency threshold range, dividing a plurality of wind fields according to the frequency modulation capacity; the first type wind field and the second type wind field are sequentially subjected to parameter adjustment control, the first type wind field and the second type wind field are controlled to enter rotation speed recovery operation, and frequency adjustment parameters are correspondingly adjusted according to the change of wind speed and the rotation speed of the fan; setting each flexible direct current converter as a sagging control mode, completing frequency control when the frequency of the alternating current system returns to the frequency threshold range, modifying the control mode of each flexible direct current converter into a constant power mode, and controlling the parameter adjustment of the first type wind field and the second type wind field to realize the frequency modulation accuracy of the fan frequency control method, inhibit the repeated frequency drop of the alternating current system and improve the frequency stability of the alternating current system.

Description

Wind farm control method and device for multi-terminal flexible direct system grid connection

Technical Field

The invention relates to the technical field of multi-terminal flexible direct-current transmission systems, in particular to a wind farm control method, a device and a storage medium for grid connection of a multi-terminal flexible direct-current system.

Background

The multi-terminal flexible direct-current transmission system is flexible in operation mode and has great advantages when wind power is connected. However, with the improvement of the wind power permeability, the wind power generation set with smaller inertia time constant gradually replaces part of the traditional synchronous generator set, and the decoupling effect of the flexible direct current transmission system also makes the wind field difficult to respond to the frequency change of the alternating current system. The improvement of the active frequency supporting capability of the fan is usually realized through load shedding control, comprehensive inertia control and other additional frequency control. The integrated inertia control realizes the frequency support of the fan to the alternating current system by simulating the inertia control and the sagging control of the synchronous generator, and compared with the load shedding control, the integrated inertia control is widely applied because the economic benefit of a wind field is not influenced, and the frequency control process of the fan can be divided into a frequency support stage and a rotating speed recovery stage.

However, existing integrated inertial control strategies suffer from the following three-point problems: 1) In the stage of fan frequency support, only the influence of the rotating speed of a fan rotor on the fan frequency modulation capacity is considered, the limitation of the active transmission capacity of the back-to-back converter is not considered, and the real-time frequency modulation capacity of the fan is difficult to accurately evaluate; 2) In the whole process of fan frequency control, only a single wind speed is considered, and the control effect of additional frequency control is difficult to ensure when the wind speed changes; 3) In the change process of the fan from the frequency support stage to the rotating speed recovery stage, cooperative frequency modulation of the converter and the wind field is not considered, so that the phenomenon of secondary frequency drop and even tertiary frequency drop often occurs. Therefore, the frequency control method of the existing fan has the problems that the frequency modulation accuracy is poor, the frequency modulation control effect is easily influenced by wind speed, the frequency stability of an alternating current system is poor, and the like.

Disclosure of Invention

The invention provides a wind power plant control method and device for multi-terminal flexible direct system grid connection, which are used for realizing the improvement of the frequency control accuracy of a fan, inhibiting the repeated frequency drop of an alternating current system and improving the frequency stability of the alternating current system through the parameter adjustment control of a first wind power plant and a second wind power plant.

The invention provides a wind farm control method for grid connection of a multi-terminal flexible direct system, wherein the multi-terminal flexible direct system comprises a plurality of alternating current systems and a plurality of wind farms; the alternating current systems and the wind fields are respectively integrated into a direct current power grid through respective converter stations; each of the converter stations includes a respective soft dc converter;

the control method comprises the following steps:

when frequency disturbance occurs in the first alternating current system, setting a soft direct current converter in each converter station to a constant power mode; when the frequency can not be returned to the frequency threshold range by controlling the synchronous generator in the first alternating current system and the direct current side capacitor of the first converter station corresponding to the first alternating current system respectively, stopping the frequency control of the direct current side capacitor of the first converter station, calculating the frequency modulation capacity of a plurality of wind fields, and dividing the wind fields into a first type wind field and a second type wind field according to the frequency modulation capacity; the frequency modulation capacity of the first type wind field is larger than that of the second type wind field;

According to the respective frequency modulation capacity and frequency deviation of the first type wind fields, calculating respective first frequency modulation parameters to carry out parameter modulation control on respective fans so as to complete the frequency control of each first type wind field; controlling each first type wind field to enter a rotational speed recovery operation, and calculating respective second frequency modulation parameters to perform parameter modulation control on respective fans according to respective frequency modulation capacity and frequency deviation of each second type wind field;

after the frequency control of each second type wind field is completed, controlling each second type wind field to enter a rotation speed recovery operation, and setting each flexible direct current converter into a sagging control mode; in the process of performing parameter adjustment control and rotational speed recovery operation on each fan in each first type wind field or second type wind field, correspondingly adjusting frequency modulation parameters of the fans according to the change of wind speed and fan rotational speed; and when the frequency of the alternating current system returns to the frequency threshold range, completing frequency control of all wind fields, and modifying the control mode of each soft direct current converter into a constant power mode.

Further, calculating frequency modulation capacity of a plurality of wind fields, and dividing the wind fields into a first wind field and a second wind field according to the frequency modulation capacity, wherein the frequency modulation capacity is as follows:

Calculating the frequency modulation capacity of each wind field, wherein the calculation formula of the frequency modulation capacity is as follows:

wherein G is _C,WF For frequency modulation capacity G _C,2,i Is the frequency modulation capacity omega of the ith fan in the wind field _r,max,i Is the upper threshold value omega of the rotating speed of the rotor of the ith fan _r,min,i The rotor rotating speed lower threshold value of the ith fan; n is the number of fans in the wind field;

and presetting a plurality of wind fields as first wind fields before ranking the frequency modulation capacity from large to small, and taking the rest wind fields as second wind fields.

Further, according to the respective frequency modulation capacity and frequency deviation of the first type wind fields, calculating respective first frequency modulation parameters to perform parameter modulation control on respective fans so as to complete frequency control of each first type wind field, wherein the method specifically comprises the following steps:

calculating a first inertia control factor according to the frequency modulation capacity and the wind field frequency change rate of the fans of the first wind fields; calculating a first sagging control factor according to the frequency modulation capacity and the wind field frequency deviation of the fans of the first wind fields; obtaining a first adaptive inertia control coefficient according to the first inertia control factor, and obtaining a first adaptive droop control coefficient according to the first droop control factor; calculating the increased active power of the first fans according to the first adaptive inertia control coefficient and the first adaptive droop control coefficient, and performing parameter adjustment control on the respective fans as a first frequency adjustment parameter;

When the first condition is met, completing the frequency control of each first type wind field;

the first condition is:wherein (1)>The change rate of the rotating speed of the fan rotor is set; />And collecting the frequency change rate of the system for the wind power plant of the first wind power plant.

Further, according to the respective frequency modulation capacity and frequency deviation of each second type wind field, calculating respective second frequency modulation parameters to perform parameter modulation control on respective fans, specifically:

calculating a second inertia control factor according to the frequency modulation capacity and the wind field frequency change rate of the fans of the wind fields of the second class; calculating a second sagging control factor according to the frequency modulation capacity and the wind field frequency deviation of the fans of the wind fields of the second class; obtaining a second adaptive inertia control coefficient according to the second inertia control factor, and obtaining a second adaptive droop control coefficient according to the second droop control factor; and calculating the increased active power of the second fans according to the second adaptive inertia control coefficient and the second adaptive droop control coefficient, and performing parameter adjustment control on the respective fans as second frequency adjustment parameters.

Further, in the process that each wind field of the first type or the second type carries out parameter adjustment control on each fan and enters rotational speed recovery operation, corresponding adjustment is carried out on frequency adjustment parameters of the fans according to the change of wind speed and rotational speed of the fans, specifically:

In the process of performing parameter adjustment control on each fan by each first type wind field or each second type wind field, taking the fan output optimal active power corresponding to the rotating speed of a fan rotor of each first type wind field or each second type wind field at the current wind speed as a first fan foundation output active power; adding the fan foundation output active power with the fan amplified active power of each first type wind field or second type wind field to obtain a first fan output active power reference value, and performing parameter adjustment control on each fan as a third frequency modulation parameter;

in the process that each wind field of the first type or the wind field of the second type carries out the operation of recovering the rotating speed of each fan, the rotating speed recovering factor and the driving factor are calculated according to the rotating speed of the fan rotor; and calculating a second fan output active power reference value according to the rotating speed recovery factor, the driving factor and the second fan basic output active power, and performing parameter adjustment control on each fan as a fourth frequency adjustment parameter.

Further, in the process that each wind field of the first type or the second type carries out parameter adjustment control on each fan and enters rotational speed recovery operation, corresponding adjustment is carried out on frequency adjustment parameters of the fans according to the change of wind speed and rotational speed of the fans, and the method further comprises the following steps:

In the process of performing parameter adjustment control on each fan by each first type wind field or second type wind field, when the wind speed is unchanged and the rotating speed of a fan rotor is a critical rotating speed, adjusting the output active power reference value of the first fan to be:

wherein P is _ref,P Outputting an active power reference value, P, for the first fan _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _ref,P (v ₀ ,ω _r,m1 ) Is the wind speedV is ₀ The rotation speed of the rotor is omega _r,m1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,m1 The critical rotation speed of the fan rotor;

when the rotating speed of the fan rotor is a first preset rotating speed and the wind speed is reduced from a first wind speed to a second wind speed, the active power output by the first fan foundation is adjusted to be:

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₁ ,ω _r,opt,1 )；

wherein P is _MPPT (ω _r,0 ) For a first wind speed v ₀ Under the condition of initial rotating speed omega of fan rotor _r,0 The corresponding fan outputs the optimal active power, P _MPPT (v ₁ ,ω _r,opt,1 ) For a second wind speed v ₁ Under the condition of optimum rotating speed omega of fan rotor _r,opt,1 The corresponding fans output optimal active power, and epsilon is a transmission factor; omega _r,c The first preset rotating speed is set;

when the rotating speed of the fan rotor is a first preset rotating speed, the wind speed is increased from the first wind speed to a third wind speed, and the mechanical power of the input fan is smaller than the electromagnetic power output by the fan, the active power output by the first fan foundation is adjusted to be:

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₂ ,ω _r,opt,2 )；

Wherein P is _MPPT (ω _r,0 ) For wind speed v ₀ Under the condition of initial rotating speed omega of fan rotor _r,0 The corresponding fan outputs the optimal active power, P _MPPT (v ₂ ,ω _r,opt,2 ) For a third wind speed v ₂ Under the condition of optimum rotating speed omega of fan rotor _r,opt,2 The corresponding fan outputs the optimal active power, epsilon is the transmissionA factor;

when the rotating speed of the fan rotor is a first preset rotating speed, the wind speed is increased from a first wind speed to a fourth wind speed, and the mechanical power input into the fan is not less than the electromagnetic power output by the fan, the active power reference value output by the first fan is adjusted to be:

wherein P is _ref,P (ω _r,c ) For the rotor speed to be critical speed omega _r,c The first fan outputs an active power reference value, P _MPPT (v ₃ ，ω _r,opt,3 ) For the wind speed of fourth wind speed v ₃ The rotating speed of the fan rotor is omega _r,opt,3 When the fan outputs optimal active power omega _r Is the rotation speed omega of the fan rotor _r,c For a first preset rotational speed omega _r,opt,3 For wind speed v ₃ And the optimal rotating speed of the fan rotor.

in the process that each first type wind field or second type wind field carries out the entering rotation speed recovery operation on each fan, when the rotation speed of the fan rotor is a second preset rotation speed and the wind speed is reduced from a first wind speed to a second wind speed, the output active power reference value of the second fan is adjusted to be:

Wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power,P _rec (v ₀ ,ω _r,d1 ) For a first wind speed v ₀ A second preset rotational speed omega _r,d1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,d1 For the first fan rotor speed corresponding to the moment when the wind speed starts to change, gamma (v ₁ ) For the wind speed of the second wind speed v ₁ At the time of rotational speed recovery factor, P _m (v ₁ ,ω _r ) For the wind speed of the second wind speed v ₁ The mechanical power of the fan at the time of the process,the change rate of the rotating speed of the fan rotor is set; gamma (v) ₁ ) For a second wind speed v ₁ The rotational speed recovery factor, omega _r,opt,1 For the wind speed of the second wind speed v ₁ The optimal rotating speed of the fan rotor is achieved;

when the rotating speed of the fan rotor is a third preset rotating speed and the wind speed is reduced from the first wind speed to the second wind speed; adjusting the second fan foundation output active power reference value to be:

P _sec (ω _r )＝(1-μ)P _m (v ₀ ,ω _r )+μP _m (v ₁ ,ω _r )

wherein P is _sec (ω _r ) For the second fan foundation to output active power reference value, mu is the transfer factor, P _m (v ₀ ,ω _r ) For wind speed v ₀ Fan mechanical power, P _m (v ₁ ,ω _r ) For wind speed v ₁ Fan mechanical power omega _r,d2 For the second fan rotor speed, omega corresponding to the moment when the wind speed begins to change _r,opt,1 For wind speed v ₁ The optimal rotating speed of the fan rotor is achieved;

calculating a rotational speed recovery factor when the wind speed is changed from the first wind speed to the second wind speed:

Wherein, gamma (omega) _r ) To recover the rotation speed recovery factor from the first wind speed to the second wind speed, γ (v) ₀ ,ω _r,d2 ) For wind speed v ₀ The rotation speed of the rotor is omega _r,d2 A rotational speed recovery factor at that time;

the output active power reference value of the second fan is adjusted to be:

P _rec (ω _r )＝(1-γ(ω _r ))P _sec (ω _r )+γ(ω _r )P _MPPT (ω _r )；

wherein P is _rec Outputting an active power reference value, P, for the second fan _MPPT (ω _r ) And outputting the optimal active power for the fan.

As a preferable scheme, the invention considers the limitation of the capacity of the back-to-back converter according to the limitation of the characteristics of the fan, and can more accurately evaluate the real-time frequency modulation capacity of the fan; the wind fields are classified according to the frequency modulation capacity, the first wind field starts to synthesize inertia control frequency support, and in the process, if the wind speed changes, the fan control strategy is correspondingly adjusted along with the wind speeds with different magnitudes. The control method provided by the invention considers the change of the wind speed in the control process, so that the rotor kinetic energy of the fan is utilized more fully and more safely to carry out frequency support;

after the frequency of the alternating current system tends to be stable, the first type wind field enters a rotating speed recovery stage, and the second type wind field starts to increase active power so as to inhibit secondary frequency drop possibly caused by the fact that the first type wind field exits frequency modulation; when the second type wind field finishes frequency modulation, the soft direct current converter starts to increase active power to inhibit three frequency drops possibly caused by the fact that the second type wind field exits from frequency modulation. Compared with the traditional control method, the control method provided by the invention effectively inhibits the repeated frequency drop of the alternating current system and improves the frequency stability of the alternating current system.

Correspondingly, the invention also provides a wind farm control device for grid connection of the multi-terminal flexible direct system, wherein the multi-terminal flexible direct system comprises a plurality of alternating current systems and a plurality of wind farms; the alternating current systems and the wind fields are respectively integrated into a direct current power grid through respective converter stations; each of the converter stations includes a respective soft dc converter; the device comprises: the system comprises a classification module, a parameter adjusting control module and a dynamic adjustment module;

the classification module is used for setting the soft direct current converter in each converter station to a constant power mode when frequency disturbance occurs in the first alternating current system; when the frequency can not be returned to the frequency threshold range by controlling the synchronous generator in the first alternating current system and the direct current side capacitor of the first converter station corresponding to the first alternating current system respectively, stopping the frequency control of the direct current side capacitor of the first converter station, calculating the frequency modulation capacity of a plurality of wind fields, and dividing the wind fields into a first type wind field and a second type wind field according to the frequency modulation capacity; the frequency modulation capacity of the first type wind field is larger than that of the second type wind field;

the parameter adjusting control module is used for calculating respective first frequency adjusting parameters to perform parameter adjusting control on respective fans according to respective frequency adjusting capacity and frequency deviation of the first type wind fields so as to complete frequency control of each first type wind field; controlling each first type wind field to enter a rotational speed recovery operation, and calculating respective second frequency modulation parameters to perform parameter modulation control on respective fans according to respective frequency modulation capacity and frequency deviation of each second type wind field; after the frequency control of each second type wind field is completed, controlling each second type wind field to enter a rotation speed recovery operation, and setting each flexible direct current converter into a sagging control mode;

The dynamic adjustment module is used for correspondingly adjusting the frequency modulation parameters of the fans according to the change of the wind speed and the fan rotation speed in the process of performing parameter adjustment control on the fans of the first type or the second type and entering the rotation speed recovery operation; and when the frequency of the alternating current system returns to the frequency threshold range, completing frequency control of all wind fields, and modifying the control mode of each soft direct current converter into a constant power mode.

As a preferable scheme, the device classification module considers the limitation of the capacity of the back-to-back converter according to the characteristic limitation of the fan, can more accurately evaluate the real-time frequency modulation capacity of the fan, and classifies wind fields according to the frequency modulation capacity;

the first wind field is controlled by the parameter adjusting control module to start comprehensive inertia control frequency support, in the process, if the wind speed changes, the dynamic adjustment module correspondingly adjusts a fan control strategy along with the wind speeds of different sizes, the change of the wind speed in the control process is considered, the frequency support is carried out by more fully and safely utilizing the rotor kinetic energy of the fan, and compared with the traditional control method which only considers single wind speed, the control method provided by the invention is more in line with the actual situation, and the frequency control accuracy of the fan is improved;

After the frequency of the alternating current system tends to be stable, controlling the first type wind field to enter a rotating speed recovery stage through the parameter adjusting control module, and starting to increase active power by the second type wind field to inhibit secondary frequency drop possibly caused by the fact that the first type wind field exits from frequency modulation; when the second type wind field finishes frequency modulation, the soft direct current converter starts to increase active power to inhibit three frequency drops possibly caused by the fact that the second type wind field exits from frequency modulation. Compared with the traditional control method, the control method provided by the invention effectively inhibits the repeated frequency drop of the alternating current system and improves the frequency stability of the alternating current system.

Accordingly, the present invention also provides a computer-readable storage medium including a stored computer program; the computer program controls the equipment where the computer readable storage medium is located to execute the wind farm control method of the multi-terminal flexible direct system grid connection according to the content of the invention when running.

Drawings

FIG. 1 is a flow diagram of one embodiment of a method for controlling a wind farm with a multi-terminal flexible direct system grid connection provided by the present invention;

FIG. 2 is a schematic diagram of a fan output active power reference value-rotor rotational speed curve when wind speeds change at different times in the process of performing parameter adjustment control according to an embodiment of a wind farm control method for multi-terminal flexible direct system grid connection provided by the invention;

FIG. 3 is a schematic diagram of a fan output active power reference value versus rotor speed curve at different times when wind speed changes during entering a speed recovery operation of an embodiment of a multi-terminal flexible direct system grid-connected wind farm control method provided by the present invention;

fig. 4 is a schematic structural diagram of an embodiment of a wind farm control device for multi-terminal flexible-direct system grid connection provided by the invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

Referring to fig. 1, a method for controlling a wind farm with multiple-terminal flexible-direct system grid connection provided by an embodiment of the present invention, where the multiple-terminal flexible-direct system includes a plurality of ac systems and a plurality of wind farms; the alternating current systems and the wind fields are respectively integrated into a direct current power grid through respective converter stations; each of the converter stations includes a respective soft dc converter; the control method comprises the steps of S101-S103:

Step S101: when frequency disturbance occurs in the first alternating current system, setting a soft direct current converter in each converter station to a constant power mode; when the frequency can not be returned to the frequency threshold range by controlling the synchronous generator in the first alternating current system and the direct current side capacitor of the first converter station corresponding to the first alternating current system respectively, stopping the frequency control of the direct current side capacitor of the first converter station, calculating the frequency modulation capacity of a plurality of wind fields, and dividing the wind fields into a first type wind field and a second type wind field according to the frequency modulation capacity; the frequency modulation capacity of the first type wind field is larger than that of the second type wind field;

In this embodiment, when a frequency disturbance event occurs in the ac system, the ac system synchronous generator first performs frequency control, and after the frequency deviation exceeds the allowable threshold value, the dc side capacitor of the converter station, the fan, and the soft dc converter sequentially perform frequency control.

The dc side capacitor of the converter station provides for a short frequency support first by discharging the energy stored by the capacitor.

Calculating the frequency f of a wind power plant collecting system of each wind field according to the following formula _wf ：

Wherein K is _wf For the frequency transmission coefficient of the wind power plant side converter station, f _wf ^* For wind farm collector system frequency reference value, U _dc For dc-side voltage of converter station, U _dc,ref Is the dc-side voltage reference of the converter station.

In this embodiment, there are multiple wind fields in the multi-terminal flexible direct current transmission system, the wind fields are divided into two types according to the frequency modulation capacity of the wind fields, the wind field with the frequency modulation capacity of the first 50% is the first type wind field, and the wind field with the smaller frequency modulation capacity of the rest wind fields is the second type wind field. The first wind field is preferentially supported in frequency, and when the frequency of the alternating current system is stable, the first wind field meets the requirement ofAnd when the wind field of the second type starts frequency support, the phenomenon of secondary frequency drop caused by the reduction of active power of the wind field of the first type is restrained.

Calculating the voltage offset delta U of the direct current side of the first wind field according to the following formula _dc,W1 ：

In the formula DeltaU _dc,W1,0 As the initial value of the voltage offset of the direct current side of the first wind field, deltaU _dcmar1 Sign (x) is a sign function for the direct-current side voltage dead zone of the first wind field.

Calculating the voltage offset delta U of the direct current side of the second type wind field according to the following formula _dc,W2 ：

In the formula DeltaU _dc,W2,0 As the initial value of the voltage offset of the direct current side of the second type wind field, deltaU _dcmar2 Sign (x) is a sign function for the direct-current side voltage dead zone of the first wind field.

Step S102: according to the respective frequency modulation capacity and frequency deviation of the first type wind fields, calculating respective first frequency modulation parameters to carry out parameter modulation control on respective fans so as to complete the frequency control of each first type wind field; controlling each first type wind field to enter a rotational speed recovery operation, and calculating respective second frequency modulation parameters to perform parameter modulation control on respective fans according to respective frequency modulation capacity and frequency deviation of each second type wind field;

In the embodiment, an alternating current system frequency parameter, a wind power plant current collection system frequency parameter, a fan back-to-back converter active transmission capacity parameter, a fan rotor rotating speed parameter and a converter station direct current side voltage parameter are obtained. The AC system frequency parameter comprises an AC system frequency f and an AC system frequency reference value f ^* The method comprises the steps of carrying out a first treatment on the surface of the The wind power plant collecting system frequency parameter comprises wind power plant collecting system frequency f _wf Frequency reference value f of wind farm collector system _wf ^* Frequency change rate of wind farm collector systemThe active conveying capacity parameter of the fan back-to-back converter comprises an active conveying capacity P of the fan back-to-back converter and an upper threshold P of the active conveying capacity P of the fan back-to-back converter _max Active power transmission capacity lower threshold P of fan back-to-back converter _min The method comprises the steps of carrying out a first treatment on the surface of the The fan rotor rotational speed parameter comprises the fan rotor rotational speed omega _r Upper threshold omega of fan rotor rotation speed _r,max Lower threshold omega of fan rotor rotation speed _r,min The method comprises the steps of carrying out a first treatment on the surface of the The converter station DC side voltage parameter comprises a converter station DC side voltage U _dc And a DC side voltage reference U of the converter station _dc,ref 。

Calculating an adaptive inertial control coefficient K _i The method specifically comprises the following steps:

under the condition of considering the constraint of the conveying capacity of the back-to-back converter, calculating an inertia control factor S according to the frequency modulation capacity of the fan and the frequency change rate of the wind power plant collecting system _i ：

Wherein P is the active conveying capacity of the back-to-back converter of the fan，P _max Upper threshold value P of active conveying capacity of back-to-back converter of fan _min Is the lower threshold value omega of the active transmission capacity of the back-to-back converter of the fan _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor,the rate of change of the frequency of the wind farm collector system,and (5) collecting an initial value of the frequency change rate of the system for the wind farm.

The adaptive inertial control coefficient K is calculated according to the following formula _i ：K _i ＝K _i0 S _i ；

Wherein K is _i0 Is the initial value of the self-adaptive inertia control coefficient, S _i Is an inertial control factor.

Calculating a self-adaptive droop control coefficient K _D The method specifically comprises the following steps:

calculating the frequency deviation delta f of the wind power plant collecting system according to the following formula: Δf=f _wf ^* -f _wf ；

Under the condition of considering the constraint of the conveying capacity of the back-to-back converter, calculating a sagging control factor S according to the frequency modulation capacity of the fan and the frequency deviation of the wind power plant collecting system _D ：

Wherein P is the active transmission capacity of the back-to-back converter of the fan, P _max Upper threshold value P of active conveying capacity of back-to-back converter of fan _min Is the lower threshold value omega of the active transmission capacity of the back-to-back converter of the fan _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min For the threshold value of the rotating speed of the fan rotor, alpha and beta are gain coefficients, delta f is the frequency deviation of a wind power plant current collection system, and delta f _max Is the wind power plant current collectorThe upper threshold value of the system frequency deviation,and collecting the frequency change rate of the system for the wind farm.

The adaptive droop control coefficient K is calculated according to the following formula _D ：K _D ＝K _D0 S _D ；

Wherein K is _D0 Is the initial value of the adaptive droop control coefficient, S _D Is a sagging control factor.

The fan power ΔP under the comprehensive inertia control is calculated according to the following formula _ref,P ：

Wherein K is _D K is an adaptive droop control coefficient _i For the adaptive inertial control coefficient, Δf is the wind farm collector system frequency deviation,and collecting the frequency change rate of the system for the wind farm.

Step S103: after the frequency control of each second type wind field is completed, controlling each second type wind field to enter a rotation speed recovery operation, and setting each flexible direct current converter into a sagging control mode; in the process of performing parameter adjustment control and rotational speed recovery operation on each fan in each first type wind field or second type wind field, correspondingly adjusting frequency modulation parameters of the fans according to the change of wind speed and fan rotational speed; and when the frequency of the alternating current system returns to the frequency threshold range, completing frequency control of all wind fields, and modifying the control mode of each soft direct current converter into a constant power mode.

wherein P is _ref,P Outputting an active power reference value, P, for the first fan _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _ref,P (v ₀ ,ω _r,m1 ) For wind speed v ₀ The rotation speed of the rotor is omega _r,m1 Active power reference for fan outputValue, omega _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,m1 The critical rotation speed of the fan rotor;

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₁ ,ω _r,opt,1 )；

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₂ ,ω _r,opt,2 )；

wherein P is _MPPT (ω _r,0 ) For wind speed v ₀ Under the condition of initial rotating speed omega of fan rotor _r,0 The corresponding fan outputs the optimal active power, P _MPPT (v ₂ ,ω _r,opt,2 ) For a third wind speed v ₂ Under the condition of optimum rotating speed omega of fan rotor _r,opt,2 The corresponding fans output optimal active power, and epsilon is a transmission factor;

wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _rec (v _0, ω _r,d1 ) For a first wind speed v ₀ Second pre-treatmentSetting the rotation speed omega _r,d1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,d1 For the first fan rotor speed corresponding to the moment when the wind speed starts to change, gamma (v ₁ ) For the wind speed of the second wind speed v ₁ At the time of rotational speed recovery factor, P _m (v ₁ ,ω _r ) For the wind speed of the second wind speed v ₁ The mechanical power of the fan at the time of the process,the change rate of the rotating speed of the fan rotor is set; gamma (v) ₁ ) For a second wind speed v ₁ The rotational speed recovery factor, omega _r,opt,1 For the wind speed of the second wind speed v ₁ The optimal rotating speed of the fan rotor is achieved;

P _sec (ω _r )＝(1-μ)P _m (v ₀ ,ω _r )+μP _m (v ₁ ,ω _r )

the output active power reference value of the second fan is adjusted to be:

P _rec (ω _r )＝(1-γ(ω _r ))P _sec (ω _r )+γ(ω _r )P _MPPT (ω _r )；

To better explain the present embodiment, please refer to fig. 2, a frequency support stage is provided, namely, in the process of performing parameter adjustment control on respective fans in each of the first type wind field or the second type wind field, the fans output active power reference values P when the wind speed changes at different moments _ref,P Is characterized by comprising the following adjustment process:

p in the figure _ref,P,0 (ω _r )、P _ref,P,1 (ω _r )、P _ref,P,2 (ω _r )、P _ref,P,3 (ω _r ) Respectively corresponding to wind speeds v ₀ 、v ₁ 、v ₂ 、v ₃ The fan outputs an active power reference value, P under the condition _m (ω _r ) For the mechanical power of the fan, P _set (ω _r ) Output active power for fan foundation, P _MPPT (ω _r ) And outputting the optimal active power for the fan.

When the wind speed does not change, the track of the active power reference value output by the fan is A-C-D-E. Wherein the reference value of the active power output by the fan in the A-C-D stage is P _ref,P ＝P _set +ΔP _ref,P The method comprises the steps of carrying out a first treatment on the surface of the When the rotating speed of the fan rotor is critical rotating speed omega _r,m1 When (corresponding to the point D), in order to avoid the rotor stall to cause the fan to cut, the line section DM of the reference value of the output active power of the fan is moved until the reference value of the output active power is equal to the wind speed v ₀ The corresponding fan mechanical power curve intersects at point E.

Calculating the reference value P of the output active power of the fan in the DE stage according to the following formula _refP ：

Wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _ref,P (v ₀ ,ω _r,m1 ) For wind speed v ₀ The rotation speed of the rotor is omega _r,m1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,m1 Is the critical rotating speed of the fan rotor.

When the rotor speed is omega _r,c At this time, consider that the wind speed suddenly decreases to v ₁ The fan foundation outputs active power P _set From an initial value P _MPPT (ω _r,0 ) Along the broken line BN to the wind speed v ₁ Under the condition of optimum rotating speed omega of fan rotor _r,opt,1 The corresponding fan outputs the optimal active power P _MPPT (v ₁ ,ω _r,opt,1 ) The active power reference value track output by the fan is made to be A-C-F-G.

The wind speed is reduced to v according to the following formula ₁ Active power P output by fan foundation _set ：

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₁ ,ω _r,opt,1 )；

Wherein P is _MPPT (ω _r,0 ) For wind speed v ₀ Under the condition of initial rotating speed omega of fan rotor _r,0 The corresponding fan outputs the optimal active power, P _MPPT (v ₁ ,ω _r,opt,1 ) For wind speed v ₁ Under the condition of optimum rotating speed omega of fan rotor _r,opt,1 The corresponding fans output the optimal active power, and epsilon is a transmission factor.

The transmission factor epsilon is calculated according to the following formula:

when the rotating speed of the fan rotor is critical rotating speed omega _r,m1 When (corresponding to the point F), in order to avoid the rotor stall to cause the fan to cut, the line section FM of the reference value of the output active power of the fan is moved until the wind speed v ₁ The corresponding fan mechanical power curve intersects at point G.

Calculating an active power reference value P output by the fan in the FG stage according to the following formula _refP ：

Wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _ref,P (v ₁ ,ω _r,m1 ) For wind speed v ₁ The rotation speed of the rotor is omega _r,m1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,m1 Is the critical rotating speed of the fan rotor.

When the rotor speed is omega _r,c At this time, consider that the wind speed suddenly increases to v ₂ The fan foundation outputs active power P _set From an initial value P _MPPT (ω _r,0 ) Along the dashed line BK to wind speed v ₂ Under the condition of optimum rotating speed omega of fan rotor _r,opt,2 The corresponding fan outputs the optimal active power P _MPPT (v ₂ ,ω _r,opt,2 ) The active power reference value track output by the fan is made to be A-C-H-I.

Calculating the wind speed increase to v according to the following formula ₂ Active power P output by fan foundation _set ：

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₂ ,ω _r,opt,2 )；

Wherein P is _MPPT (ω _r,0 ) For wind speed v ₀ Under the condition of initial rotating speed omega of fan rotor _r,0 The corresponding fan outputs the optimal active power, P _MPPT (v ₂ ,ω _r,opt,2 ) For wind speed v ₂ Under the condition of optimum rotating speed omega of fan rotor _r,opt,2 The corresponding fans output the optimal active power, and epsilon is a transmission factor.

When the rotating speed of the fan rotor is critical rotating speed omega _r,m1 When (corresponding to the point H), in order to avoid the rotor stall to cause the fan to cut, the line extension section HM of the reference value of the output active power of the fan is moved until the reference value of the output active power is equal to the wind speed v ₂ The corresponding fan mechanical power curves intersect at point I.

Calculating an HI stage fan output active power reference value P according to the following formula _refP ：

Wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _ref,P (v ₂ ,ω _r,m1 ) For wind speed v ₂ The rotation speed of the rotor is omega _r,m1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,m1 Is the critical rotating speed of the fan rotor.

When the rotor speed is omega _r,c At this time, consider that the wind speed suddenly increases to v ₃ At the moment, the mechanical power input into the fan is larger than the electromagnetic power output by the fan, the fan can not increase the active power by releasing the kinetic energy of the rotor, the rotating speed of the rotor of the fan starts to recover, and the reference value extension CJ of the active power output by the fan is adjusted to be equal to the wind speed v ₃ And the corresponding intersection point J of the mechanical power of the fan and the MPPT curve.

Calculating an active power reference value P of the fan output according to the following formula _refP ：

Wherein P is _ref,P (ω _r,c ) For rotor speed omega _r,c The fan outputs an active power reference value, P _MPPT (v ₃ ，ω _r,opt,3 ) For wind speed v ₃ The rotating speed of the fan rotor is omega _r,opt,3 When the fan outputs optimal active power omega _r Is the rotation speed omega of the fan rotor _r,c The rotational speed of the rotor of the fan at the point C, omega _r,opt,3 For wind speed v ₃ And the optimal rotating speed of the fan rotor.

For a better explanation of the present embodiment, please refer to fig. 3, a rotational speed recovery stage is provided, that is, during the process of entering rotational speed recovery operation of each fan by each wind field of the first type or the second type, the fan outputs an active power reference value P when the wind speed changes at different times _rec Is characterized by comprising the following adjustment process:

p in the figure _rec,0 (ω _r )、P _rec,2 (ω _r ) Respectively corresponding to wind speeds v ₀ 、v ₂ The fan outputs an active power reference value, P under the condition _rec,1,1 (ω _r )、P _rec,1,2 (ω _r )、P _rec,1,3 (ω _r ) Respectively correspond to the wind speeds from v ₀ Down to v ₁ The fans under three different scenes output active power reference values, P _sec (ω _r ) To convert power, P _m (ω _r ) For the mechanical power of the fan, P _MPPT (ω _r ) And outputting the optimal active power for the fan.

Assuming that the fan recovers the rotating speed from the point D, and when the wind speed is not changed, the track of the active power reference value output by the fan is D-B-F-H-A.

The rotational speed recovery factor γ is calculated according to the following formula:

wherein omega is _r Is the rotation speed omega of the fan rotor _r,0 For initial rotational speed of fan rotor omega _r,D The D point fan rotor speed.

The driving factor τ is calculated according to the following formula:

wherein omega is _r Is the rotation speed omega of the fan rotor _r,d The rotational speed of the rotor of the D-point fan, omega _r,m1 Is the critical rotating speed of the fan rotor.

Calculating an active power reference value P of the fan output according to the following formula _rec ：

P _rec ＝((1-γ(v ₀ ))P _sec (v ₀ ,ω _r )+γ(v ₀ )P _MPPT (ω _r ))·τ；

Wherein, gamma (v) ₀ ) For wind speed v ₀ At the time of rotational speed recovery factor, P _sec Output active power for fan foundation, P _MPPT (ω _r ) And outputting optimal active power for the fan, wherein tau is a driving factor.

Assume that scenario 1 is when the rotor speed is ω _r,d1 When (corresponding to point B), consider the wind speed from v ₀ Reduced to v ₁ Moving the line extension section BM of the fan output active power reference value until the line extension section BM is equal to the wind speed v ₁ The corresponding mechanical power curve of the fan is intersected at the point C, so that the track of the reference value of the output active power of the fan is formed by D-B-C-E.

Wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _rec (v ₀ ,ω _r,d1 ) For wind speed v ₀ Rotational speed omega _r,d1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,d1 For the fan rotor speed corresponding to the scene 1 wind speed change moment, gamma (v ₁ ) For wind speed v ₁ The rotational speed recovery factor at the timeSon, P _m (v ₁ ,ω _r ) For wind speed v ₁ The mechanical power of the fan at the time of the process,is the change rate of the rotating speed of the fan rotor.

The wind speed v is calculated according to the following formula ₁ At the time of rotational speed recovery factor gamma (v ₁ )：

Wherein omega is _r Is the rotation speed omega of the fan rotor _r,d1 The rotation speed omega of the fan rotor corresponding to the change moment of the wind speed of the scene 1 _r,opt,1 For wind speed v ₁ And the optimal rotating speed of the fan rotor.

Assume that scenario 2 is when the rotor speed is ω _r,d2 When (corresponding to point F), consider the wind speed from v ₀ Reduced to v ₁ Adjusting the output active power P of the fan foundation _sec The active power reference value track output by the fan is enabled to be D-B-F-E.

Calculating a fan foundation output active power reference value P according to the following formula _sec ：

P _sec (ω _r )＝(1-μ)P _m (v ₀ ,ω _r )+μP _m (v ₁ ,ω _r )；

Wherein μ is a transfer factor, P _m (v ₀ ,ω _r ) For wind speed v ₀ Fan mechanical power, P _m (v ₁ ,ω _r ) For wind speed v ₁ Fan mechanical power.

The transfer factor μ is calculated according to the following formula:

wherein omega is _r Is the rotation speed omega of the fan rotor _r,d2 Fan rotor rotation corresponding to scene 2 wind speed change momentSpeed, omega _r,opt,1 For wind speed v ₁ And the optimal rotating speed of the fan rotor.

Calculating wind speed from v according to the following formula ₀ Becomes v ₁ At the time of rotational speed recovery factor gamma (omega) _r )：

Wherein, gamma (v) ₀ ,ω _r,d2 ) For wind speed v ₀ The rotation speed of the rotor is omega _r,d2 The rotational speed recovery factor, omega _r Is the rotation speed omega of the fan rotor _r,d2 The rotation speed omega of the fan rotor corresponding to the change moment of the wind speed of scene 2 _r,opt,1 For wind speed v ₁ And the optimal rotating speed of the fan rotor.

P _rec (ω _r )＝(1-γ(ω _r ))P _sec (ω _r )+γ(ω _r )P _MPPT (ω _r )；

Wherein, gamma (omega) _r ) As a rotation speed recovery factor, P _sec (ω _r ) Output active power reference value for fan foundation, P _MPPT (ω _r ) And outputting the optimal active power for the fan.

Assume that scenario 3 is when the rotor speed is ω _r,d3 When (corresponding to the H point), consider the wind speed from v ₀ Reduced to v ₁ Moving the line extension section HM of the active power reference value output by the fan until the line extension section HM is equal to the wind speed v ₁ The corresponding mechanical power curves of the fans are intersected at the J point, so that the trajectories of the output active power reference values of the fans are defined by D-B-H-J-E.

Wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _rec (v ₀ ,ω _r,d3 ) For wind speed v ₀ Rotational speed omega _r,d3 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,d3 For the fan rotor speed corresponding to scene 3 wind speed change moment, gamma (v ₁ ) For wind speed v ₁ At the time of rotational speed recovery factor, P _m (v ₁ ,ω _r ) For wind speed v ₁ The mechanical power of the fan at the time of the process,is the change rate of the rotating speed of the fan rotor.

At any time, consider the wind speed from v ₀ Increase to v ₂ After the track of the reference value of the active power output by the fan is changed from D-B-H-A, the reference value of the active power output by the fan is continuously adjusted to be in line with the wind speed v along the MPPT curve ₂ And at the intersection point L of the corresponding fan mechanical power and the MPPT curve, the total track of the active power reference value output by the fan is formed by D-B-H-A-L.

In this embodiment, in order to ensure the frequency modulation sequence of the soft dc converter, during the frequency modulation process of the dc side capacitor and the wind field, the soft dc converter is set to a constant power mode, and after the second wind field enters the rotational speed recovery stage, the soft dc converter is set to a droop control mode; after the wind field is subjected to frequency support, the flexible direct current converter increases active power through droop control so as to reduce power shortage caused by the fan rotating speed recovery stage and inhibit secondary frequency drop or tertiary frequency drop caused by unbalanced power. After the frequency of the alternating current system returns to the frequency allowable range (the allowable deviation is +/-0.2 Hz), the frequency control is finished, and the control mode of the soft direct current converter is modified to be a constant power mode.

The increased active power delta P of the soft DC converter is calculated according to the following formula _ref,G ：

Wherein K is _v Is a direct current voltage sagCoefficient, K _f U is the frequency droop coefficient _dc For dc-side voltage of converter station, U _dc,ref For the dc-side voltage reference value of the converter station, Δf _G Is the ac system frequency deviation.

Calculating the frequency deviation delta f of the alternating current system according to the following formula _G ：

Wherein Δf _G,0 For the initial value of the frequency deviation of the alternating current system, deltaf _mar Sign (x) is a sign function for the frequency dead zone.

Therefore, after the alternating current system is disturbed, the synchronous generator of the alternating current system firstly performs frequency control, and when the frequency deviation exceeds an allowable threshold value, the capacitor on the direct current side of the converter station releases energy to perform temporary frequency support; then, the first wind field starts frequency support, and when the first wind field ends frequency modulation, the second wind field starts to increase active power so as to inhibit secondary frequency drop possibly caused by the first wind field exiting frequency modulation; when the second type wind field finishes frequency modulation, the soft direct current converter starts to increase active power to inhibit three frequency drops possibly caused by the fact that the second type wind field exits from frequency modulation. Compared with the traditional control method, the control method provided by the invention effectively inhibits the multiple frequency drops of the alternating current system.

The implementation of the embodiment of the invention has the following effects:

according to the invention, the limitation of the capacity of the back-to-back converter is considered while the characteristic limitation of the fan is considered, so that the real-time frequency modulation capacity of the fan can be more accurately estimated; the wind fields are classified according to the frequency modulation capacity, the first wind field starts to synthesize inertia control frequency support, and in the process, if the wind speed changes, the fan control strategy is correspondingly adjusted along with the wind speeds with different magnitudes. The control method provided by the invention considers the change of the wind speed in the control process, so that the rotor kinetic energy of the fan is utilized more fully and more safely to carry out frequency support;

Example two

Referring to fig. 4, a wind farm control device for multi-terminal flexible-direct system grid connection provided by the embodiment of the invention, where the multi-terminal flexible-direct system includes a plurality of ac systems and a plurality of wind farms; the alternating current systems and the wind fields are respectively integrated into a direct current power grid through respective converter stations; each of the converter stations includes a respective soft dc converter; the device comprises: the system comprises a classification module 201, a parameter adjustment control module 202 and a dynamic adjustment module 203;

the classification module 201 is configured to set the soft dc converters in each converter station to a constant power mode when a frequency disturbance occurs in the first ac system; when the frequency can not be returned to the frequency threshold range by controlling the synchronous generator in the first alternating current system and the direct current side capacitor of the first converter station corresponding to the first alternating current system respectively, stopping the frequency control of the direct current side capacitor of the first converter station, calculating the frequency modulation capacity of a plurality of wind fields, and dividing the wind fields into a first type wind field and a second type wind field according to the frequency modulation capacity; the frequency modulation capacity of the first type wind field is larger than that of the second type wind field;

The parameter adjustment control module 202 is configured to calculate respective first frequency adjustment parameters according to respective frequency adjustment capacities and frequency deviations of the first type wind fields, and perform parameter adjustment control on respective fans, so as to complete frequency control of each first type wind field; controlling each first type wind field to enter a rotational speed recovery operation, and calculating respective second frequency modulation parameters to perform parameter modulation control on respective fans according to respective frequency modulation capacity and frequency deviation of each second type wind field; after the frequency control of each second type wind field is completed, controlling each second type wind field to enter a rotation speed recovery operation, and setting each flexible direct current converter into a sagging control mode;

the dynamic adjustment module 203 is configured to correspondingly adjust a frequency modulation parameter of the fan according to a change of a wind speed and a fan rotation speed during parameter adjustment control and rotation speed recovery operation of each fan in each first type of wind field or each second type of wind field; and when the frequency of the alternating current system returns to the frequency threshold range, completing frequency control of all wind fields, and modifying the control mode of each soft direct current converter into a constant power mode.

The wind farm control device for the multi-terminal flexible direct system grid connection can implement the wind farm control method for the multi-terminal flexible direct system grid connection in the method embodiment. The options in the method embodiments described above are also applicable to this embodiment and will not be described in detail here. The rest of the embodiments of the present application may refer to the content of the above method embodiments, and in this embodiment, no further description is given.

the device classification module considers the limitation of the capacity of the back-to-back converter according to the characteristic limitation of the fan, can more accurately evaluate the real-time frequency modulation capacity of the fan, and classifies wind fields according to the frequency modulation capacity;

Example III

Correspondingly, the invention further provides a computer readable storage medium, which comprises a stored computer program, wherein when the computer program runs, equipment where the computer readable storage medium is located is controlled to execute the wind farm control method for multi-terminal flexible direct system grid connection according to any embodiment.

The computer program may be divided into one or more modules/units, which are stored in the memory and executed by the processor to accomplish the present invention, for example. The one or more modules/units may be a series of computer program instruction segments capable of performing the specified functions, which instruction segments are used for describing the execution of the computer program in the terminal device.

The terminal equipment can be computing equipment such as a desktop computer, a notebook computer, a palm computer, a cloud server and the like. The terminal device may include, but is not limited to, a processor, a memory.

The processor may be a central processing unit (Central Processing Unit, CPU), other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), field programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like, which is a control center of the terminal device, and which connects various parts of the entire terminal device using various interfaces and lines.

The memory may be used to store the computer program and/or the module, and the processor may implement various functions of the terminal device by running or executing the computer program and/or the module stored in the memory and invoking data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function, and the like; the storage data area may store data created according to the use of the mobile terminal, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as a hard disk, memory, plug-in hard disk, smart Media Card (SMC), secure Digital (SD) Card, flash Card (Flash Card), at least one disk storage device, flash memory device, or other volatile solid-state storage device.

Wherein the terminal device integrated modules/units may be stored in a computer readable storage medium if implemented in the form of software functional units and sold or used as stand alone products. Based on such understanding, the present invention may implement all or part of the flow of the method of the above embodiment, or may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the computer program may implement the steps of each of the method embodiments described above. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), an electrical carrier signal, a telecommunications signal, a software distribution medium, and so forth.

The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present invention, and are not to be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without departing from the spirit and principles of the present invention are intended to be included in the scope of the present invention.

Claims

1. The wind power plant control method for the grid connection of the multi-terminal flexible direct system is characterized in that the multi-terminal flexible direct system comprises a plurality of alternating current systems and a plurality of wind power plants; the alternating current systems and the wind fields are respectively integrated into a direct current power grid through respective converter stations; each of the converter stations includes a respective soft dc converter;

the control method comprises the following steps:

2. The method for controlling a wind farm with multi-terminal flexible direct system grid connection according to claim 1, wherein the calculating the frequency modulation capacity of the wind farms divides the wind farms into a first wind farm and a second wind farm according to the frequency modulation capacity comprises:

3. The method for controlling a wind farm with multi-terminal flexible direct system grid connection according to claim 2, wherein the calculating the respective first frequency modulation parameters according to the respective frequency modulation capacity and frequency deviation of the wind farm of the first type performs parameter modulation control on the respective fans to complete the frequency control of the wind farm of the first type comprises the following specific steps:

4. The method for controlling a wind farm with multi-terminal flexible direct system grid connection according to claim 3, wherein the calculating the respective second frequency modulation parameters according to the respective frequency modulation capacity and frequency deviation of each wind farm of the second class, and performing parameter modulation control on the respective fans comprises the following steps:

5. The method for controlling a wind farm with multi-terminal flexible direct system grid connection according to claim 4, wherein in the process of performing parameter adjustment control and rotational speed recovery operation on each fan in each first type wind farm or second type wind farm, the frequency adjustment parameters of the fans are correspondingly adjusted according to the change of wind speed and fan rotational speed, specifically:

6. The method for controlling a wind farm with multi-terminal flexible direct system grid connection according to claim 5, wherein in the process of performing parameter tuning control on each fan and entering rotational speed recovery operation on each wind farm of the first type or the wind farm of the second type, the frequency tuning parameters of the fans are correspondingly adjusted according to the change of the wind speed and the rotational speed of the fans, further comprising:

wherein P is _ref,P Outputting an active power reference value, P, for the first fan _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _ref,P (v ₀ ,ω _r,m1 ) For wind speed v ₀ The rotation speed of the rotor is omega _r,m1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,max Is the upper threshold value of the rotating speed of the fan rotor omega _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,m1 The critical rotation speed of the fan rotor;

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₁ ,ω _r,opt,1 )；

P _set (ω _r )＝εP _MPPT (ω _r,0 )+(1-ε)P _MPPT (v ₂ ,ω _r,opt,2 )；

7. The method for controlling a wind farm with multi-terminal flexible direct system grid connection according to claim 5, wherein in the process of performing parameter tuning control on each fan and entering rotational speed recovery operation on each wind farm of the first type or the wind farm of the second type, the frequency tuning parameters of the fans are correspondingly adjusted according to the change of the wind speed and the rotational speed of the fans, further comprising:

wherein P is _MPPT (ω _r,min ) Is omega _r,min When the fan outputs the optimal active power, P _rec (v ₀ ,ω _r,d1 ) For a first wind speed v ₀ A second preset rotational speed omega _r,d1 The fan outputs active power reference value omega _r Is the rotation speed omega of the fan rotor _r,min Is the lower threshold value of the rotating speed of the fan rotor omega _r,d1 For the first fan rotor speed corresponding to the moment when the wind speed starts to change, gamma (v ₁ ) For the wind speed of the second wind speed v ₁ At the time of rotational speed recovery factor, P _m (v ₁ ,ω _r ) For the wind speed of the second wind speed v ₁ The mechanical power of the fan at the time of the process,the change rate of the rotating speed of the fan rotor is set; gamma (v) ₁ ) For a second wind speed v ₁ The rotational speed recovery factor, omega _r,opt,1 For the wind speed of the second wind speed v ₁ The optimal rotating speed of the fan rotor is achieved;

P _sec (ω _r )＝(1-μ)P _m (v ₀ ,ω _r )+μP _m (v ₁ ,ω _r )

the output active power reference value of the second fan is adjusted to be:

P _rec (ω _r )＝(1-γ(ω _r ))P _sec (ω _r )+γ(ω _r )P _MPPT (ω _r )；

8. The wind power plant control device for the grid connection of the multi-terminal flexible direct system is characterized in that the multi-terminal flexible direct system comprises a plurality of alternating current systems and a plurality of wind power plants; the alternating current systems and the wind fields are respectively integrated into a direct current power grid through respective converter stations; each of the converter stations includes a respective soft dc converter; the device comprises: the system comprises a classification module, a parameter adjusting control module and a dynamic adjustment module;

9. A computer readable storage medium, wherein the computer readable storage medium comprises a stored computer program; wherein the computer program, when running, controls the device in which the computer readable storage medium is located to execute a wind farm control method for multi-terminal flexible direct system grid connection according to any of claims 1 to 7.