CN113809760B - Control method and device for wind power plant to participate in secondary frequency modulation of power grid - Google Patents

Control method and device for wind power plant to participate in secondary frequency modulation of power grid Download PDF

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Publication number
CN113809760B
CN113809760B CN202111124550.0A CN202111124550A CN113809760B CN 113809760 B CN113809760 B CN 113809760B CN 202111124550 A CN202111124550 A CN 202111124550A CN 113809760 B CN113809760 B CN 113809760B
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fan
pitch angle
wind
power
wind farm
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CN113809760A (en
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周前
李文博
张刘冬
朱鑫要
贾勇勇
李强
赵静波
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State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

Abstract

The application discloses a control method and device for wind power plant participation in secondary frequency modulation of a power grid. In the method, a fan mechanical power model is firstly established, and the relation between the fan mechanical power and the pitch angle is determined. And then establishing a fan prediction model, and determining a wind field prediction model on the basis of the fan prediction model. And further determining a total objective function by taking the minimum difference of pitch angles among all fans in the wind power plant and the minimum change of pitch angles of all fans in the wind power plant as targets. And determining a pitch angle reference value according to the wind field prediction model and the total objective function. And finally, correcting and determining a pitch angle target value for the pitch angle reference value, thereby realizing secondary frequency modulation control for the power grid. According to the method and the device, on the basis that the wind power plant realizes power grid frequency adjustment, the electromagnetic power between fans in the wind power plant can be better coordinated, the excessive change of the pitch angle of the fans is avoided, the wind energy loss is reduced to the greatest extent, and the electromagnetic power instruction value of the fans which are delivered from the upper level can be tracked more quickly and stably.

Description

Control method and device for wind power plant to participate in secondary frequency modulation of power grid
Technical Field
The application relates to the technical field of secondary frequency modulation of power grids, in particular to a control method and device for wind power plants to participate in secondary frequency modulation of power grids.
Background
In recent years, as the permeability of wind power in grids of various countries is continuously increased, various countries also put higher and higher requirements on wind power stations to access to the grids and participate in grid service, and the wind power stations are required to participate in grid frequency modulation service on the basis of stably outputting electric energy like conventional power stations.
Under the traditional maximum power tracking control, the doubly-fed wind turbine does not have inertial response capability and frequency modulation capability similar to those of a synchronous generator. Therefore, when the high-permeability wind power is connected into a power system, the problems of low inertial response capability, insufficient frequency modulation capability and the like of the power grid can be brought. Based on the problems, grid connection guidelines of the domestic and foreign power grids clearly indicate that the grid connection fans need to provide frequency modulation auxiliary services. In the actual operation of the power grid, the fan can respond to the system frequency change in time and maintain the frequency stable. At present, the control strategy of the fan participating in frequency modulation mainly comprises three types of additional inertia control, rotor overspeed control and pitch angle control.
The research in the prior art focuses more on primary frequency modulation control strategies of fans, and few researches relate to the participation of fans in secondary frequency modulation control strategies. Therefore, how to reasonably solve the problem of frequency control of the fan, and make the fan have secondary frequency modulation capability similar to that of a synchronous generator on the premise of considering stability, becomes a problem to be solved urgently.
Disclosure of Invention
The application discloses a control method and a device for wind power plant participation in secondary frequency modulation of a power grid, which are used for solving the technical problems that in the prior art, more researches focus on primary frequency modulation control strategies of fans, and the fans are not involved in the researches on the secondary frequency modulation control strategies.
The first aspect of the application discloses a control method for wind power plant participation in secondary frequency modulation of a power grid, comprising the following steps:
acquiring air density, a radius of a fan blade and wind speed, and generating a fan mechanical power model according to the air density, the radius of the fan blade and the wind speed, wherein the fan mechanical power model is used for determining a fan mechanical power model;
acquiring an initial pitch angle, and determining the initial mechanical power of the fan according to the fan mechanical power model and the initial pitch angle;
acquiring a pitch angle variation, a fan initial electromagnetic power and a fan electromagnetic power variation, and determining a pitch angle variation speed according to the fan mechanical power model, the fan initial electromagnetic power, the initial pitch angle, the pitch angle variation and the fan electromagnetic power variation;
acquiring an electromagnetic power instruction value of a fan, and determining an electromagnetic power change rate according to the electromagnetic power instruction value of the fan;
Generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate;
generating a wind power plant continuous state space model according to the fan prediction model;
generating a wind power plant discrete time domain state space model according to the wind power plant continuous state space model;
obtaining the pitch angle of any fan in a wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm and the pitch angle variation of any fan in the wind farm, and determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions;
determining a pitch angle reference value according to the wind farm discrete time domain state space model and the total objective function;
determining a fan mechanical power reference value according to the fan mechanical power model and the pitch angle reference value;
acquiring an actual value of the mechanical power of the fan, and determining a pitch angle correction amount according to the actual value of the mechanical power of the fan and the reference value of the mechanical power of the fan;
And correcting the pitch angle reference value according to the pitch angle correction amount, and determining a pitch angle target value, wherein the pitch angle target value is used for adjusting the electromagnetic power of any fan in the wind power plant to complete the secondary frequency modulation control of the power grid.
Optionally, the determining the total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the number of predictions of any fan in the wind farm, the change amount of the pitch angle of any fan in the wind farm, and a preset constraint condition includes:
determining a pitch angle average value according to the pitch angle of any fan in the wind power plant and the number of fans in the wind power plant;
determining a first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value;
determining a second objective function according to the number of fans in the wind power plant, the predicted times of any fan in the wind power plant and the change amount of the pitch angle of any fan in the wind power plant;
and determining the total objective function according to the first objective function and the second objective function.
Optionally, the constraint condition includes a capacity constraint of a fan, a capacity constraint of a wind power plant, a reserve capacity constraint of the fan, a reserve capacity constraint of the wind power plant, a fan electromagnetic power command value constraint and a tracking electromagnetic power command value constraint.
Optionally, the determining a first objective function according to the number of fans in the wind farm, the number of times of prediction of any fan in the wind farm, the pitch angle of any fan in the wind farm, and the pitch angle average value includes:
and determining the first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value, and taking the minimum difference of the pitch angles among all fans in the wind power plant as the objective.
Optionally, the determining a second objective function according to the number of fans in the wind farm, the predicted times of any fan in the wind farm and the change amount of the pitch angle of any fan in the wind farm includes
And determining the second objective function according to the number of fans in the wind farm, the prediction times of any fan in the wind farm and the change amount of the pitch angle of any fan in the wind farm, and taking the minimum change amount of the pitch angle of each fan in the wind farm as a target.
Optionally, determining a pitch angle correction according to the actual fan mechanical power value and the fan mechanical power reference value, including;
and determining a pitch angle correction amount according to the difference value between the actual fan mechanical power value and the reference fan mechanical power value.
Optionally, the generating a fan mechanical power model according to the air density, the fan blade radius and the wind speed includes:
generating the fan mechanical power model by the following formula:
wherein P is m Representing the mechanical power of the fan, ρ representing the air density, pi representing the circumference ratio, R representing the radius of the fan blade, v representing the wind speed, θ representing the pitch angle, and e representing the natural constant.
Optionally, the generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate includes:
generating the fan prediction model by the following formula:
△x i ＝A i △x i +B i △u i +E i ；
△y i ＝C i △x i ；
△x i ＝[△θ i △P e,i ] T ；
△u i ＝[△P ref,i ]；
△y i ＝[△θ i △P e,i ] T ；
wherein Deltax is i Representing the state variable of the ith fan, A i A first fan coefficient matrix representing an ith fan, B i A second fan coefficient matrix representing the ith fan, deltau i Represents the control variable of the ith fan, delta y i Representing the output variable of the ith fan, C i Represents a third fan coefficient matrix, delta theta i Represents the change quantity of the pitch angle of the ith fan, delta P e,i Shows the electromagnetic power variation quantity of the ith fan, delta P ref,i Representing a fan electromagnetic power instruction value, P, of an ith fan e0,i Represents the initial electromagnetic power of the ith fan, P m,i Represents the mechanical power of the ith fan, H t Represents a preset fan inertia constant, theta 0,t Represents the initial pitch angle of the ith fan, T c Representing the control period, E i Representing a fourth fan coefficient matrix.
Optionally, the determining the total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the number of predictions of any fan in the wind farm, the change amount of the pitch angle of any fan in the wind farm, and a preset constraint condition includes:
the overall objective function is determined by the following formula:
wherein N is W Representing the number of fans in the wind farm, i represents the ith fan and N p Represents the number of predictions of the fan, k represents the kth prediction, θ i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) Represents the pitch angle average value, Q, at the kth prediction 1 Representing a preset first weight coefficient, Q 2 Representing a preset second weight coefficient, the first weight coefficient Q 1 Refers to a weight coefficient aiming at minimizing the pitch angle difference between fans, and the second weight coefficient Q 2 Refers to a weight coefficient that aims to minimize the change in the pitch angle of the fan itself.
The second aspect of the application discloses a wind farm participates in control device of electric wire netting secondary frequency modulation, wind farm participates in control device of electric wire netting secondary frequency modulation is applied to the wind farm of this application first aspect disclosed and participates in control method of electric wire netting secondary frequency modulation, wind farm participates in control device of electric wire netting secondary frequency modulation includes:
the fan mechanical power model generation module is used for acquiring air density, fan blade radius and wind speed, and generating a fan mechanical power model according to the air density, the fan blade radius and the wind speed, wherein the fan mechanical power model is used for determining a fan mechanical power model;
the initial mechanical power determining module is used for acquiring an initial pitch angle and determining the initial mechanical power of the fan according to the fan mechanical power model and the initial pitch angle;
the pitch angle change speed acquisition module is used for acquiring a pitch angle change amount, a fan initial electromagnetic power and a fan electromagnetic power change amount, and determining a pitch angle change speed according to the fan mechanical power model, the fan initial electromagnetic power, the initial pitch angle, the pitch angle change amount and the fan electromagnetic power change amount;
The electromagnetic power change rate acquisition module is used for acquiring an electromagnetic power instruction value of the fan and determining the electromagnetic power change rate according to the electromagnetic power instruction value of the fan;
the fan prediction model generation module is used for generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate;
the wind power plant continuous model generation module is used for generating a wind power plant continuous state space model according to the fan prediction model;
the wind power plant discrete model generation module is used for generating a wind power plant discrete time domain state space model according to the wind power plant continuous state space model;
the total objective function determining module is used for obtaining the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm and the pitch angle variation of any fan in the wind farm, and determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions;
the pitch angle reference value determining module is used for determining a pitch angle reference value according to the wind power plant discrete time domain state space model and the total objective function;
The fan mechanical power reference value determining module is used for determining a fan mechanical power reference value according to the fan mechanical power model and the pitch angle reference value;
the pitch angle correction amount determining module is used for obtaining the actual value of the mechanical power of the fan and determining the pitch angle correction amount according to the actual value of the mechanical power of the fan and the mechanical power reference value of the fan;
and the secondary frequency modulation control module is used for correcting the pitch angle reference value according to the pitch angle correction amount to determine a pitch angle target value, wherein the pitch angle target value is used for adjusting the electromagnetic power of any fan in the wind power plant to complete the secondary frequency modulation control of the power grid.
Optionally, the overall objective function determining module includes:
the pitch angle average value determining unit is used for determining a pitch angle average value according to the pitch angle of any fan in the wind farm and the number of fans in the wind farm;
the first objective function determining unit is used for determining a first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value;
the second objective function determining unit is used for determining a second objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant and the change amount of the pitch angle of any fan in the wind power plant;
And the total objective function acquisition unit is used for determining the total objective function according to the first objective function and the second objective function.
Optionally, the constraint condition includes a capacity constraint of a fan, a capacity constraint of a wind power plant, a reserve capacity constraint of the fan, a reserve capacity constraint of the wind power plant, a fan electromagnetic power command value constraint and a tracking electromagnetic power command value constraint.
Optionally, the first objective function determining unit includes:
and determining the first objective function by taking the minimum difference of the pitch angles among all fans in the wind power plant as a target according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the average value of the pitch angles.
Optionally, the second objective function determining unit includes:
and the second objective function is determined by taking the minimum change of the pitch angle of each fan in the wind farm as a target according to the number of fans in the wind farm, the prediction times of any fan in the wind farm and the change of the pitch angle of any fan in the wind farm.
Optionally, the pitch angle correction amount determining module includes:
And the pitch angle correction amount is determined according to the difference value between the actual fan mechanical power value and the fan mechanical power reference value.
Optionally, the fan mechanical power model generation module is configured to generate the fan mechanical power model by the following formula:
wherein P is m Representing the mechanical power of the fan, ρ representing the air density, pi representing the circumference ratio, R representing the radius of the fan blade, v representing the wind speed, θ representing the pitch angle, and e representing the natural constant.
Optionally, the fan prediction model generating module is configured to generate a fan prediction model according to the following formula:
△x i ＝A i △x i +B i △u i +E i ；
△y i ＝C i △x i ；
△x i ＝[△θ i △P e,i ] T ；
△u i ＝[△P ref,i ]；
△y i ＝[△θ i △P e,i ] T ；
wherein Deltax is i Representing the state variable of the ith fan, A i A first fan coefficient matrix representing an ith fan, B i A second fan coefficient matrix representing the ith fan, deltau i Represents the control variable of the ith fan, delta y i Representing the output variable of the ith fan, C i Represents a third fan coefficient matrix, delta theta i Represents the change quantity of the pitch angle of the ith fan, delta P e,i Shows the electromagnetic power variation quantity of the ith fan, delta P ref,i Representing a fan electromagnetic power instruction value, P, of an ith fan e0,i Represents the initial electromagnetic power of the ith fan, P m,i Represents the mechanical power of the ith fan, H t Represents a preset fan inertia constant, theta 0,t Represents the initial pitch angle of the ith fan, T c Representing the control period, E i Representing a fourth fan coefficient matrix.
Optionally, the total objective function determining module is configured to determine the total objective function by the following formula:
wherein N is W Representing the number of fans in the wind farm, i represents the ith fan and N p Represents the number of predictions of the fan, k represents the kth prediction, θ i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) Represents the pitch angle average value, Q, at the kth prediction 1 Representing a preset first weight coefficient, Q 2 Representing a presetA second weight coefficient, the first weight coefficient Q 1 Refers to a weight coefficient aiming at minimizing the pitch angle difference between fans, and the second weight coefficient Q 2 Refers to a weight coefficient that aims to minimize the change in the pitch angle of the fan itself.
The application relates to the technical field of secondary frequency modulation of power grids, and discloses a control method and device for participation of a wind farm in secondary frequency modulation of the power grids. In the method, a fan mechanical power model is firstly established, and the relation between the fan mechanical power and the pitch angle is determined. And then, a fan prediction model is established according to the fan electromagnetic power instruction value, and a wind field prediction model is determined on the basis of the fan prediction model. And further determining a total objective function by taking the minimum difference of pitch angles among all fans in the wind power plant and the minimum change of pitch angles of all fans in the wind power plant as targets. And determining a pitch angle reference value according to the wind field prediction model and the total objective function. And finally, correcting the pitch angle reference value, and determining a pitch angle target value, thereby realizing secondary frequency modulation control of the power grid. According to the method and the device, on the basis that the wind power plant realizes power grid frequency adjustment, the electromagnetic power between fans in the wind power plant can be better coordinated, the excessive change of the pitch angle of the fans is avoided, the wind energy loss is reduced to the greatest extent, and the electromagnetic power instruction value of the fans which are delivered from the upper level can be tracked more quickly and stably.
Drawings
In order to more clearly illustrate the technical solutions of the present application, the drawings that are needed in the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
Fig. 1 is a schematic workflow diagram of a control method for a wind farm to participate in secondary frequency modulation of a power grid according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a pitch angle optimization allocation strategy based on MPC in a control method for participating in secondary frequency modulation of a power grid in a wind farm disclosed in an embodiment of the present application;
FIG. 3 is a structure diagram of pitch angle control in a control method of wind farm participating in secondary frequency modulation of a power grid according to an embodiment of the present application;
fig. 4 is a diagram of an electromagnetic power adjusting range of a fan in a control method of a wind farm participating in secondary frequency modulation of a power grid according to an embodiment of the present application;
FIG. 5 is a graph of wind energy capture coefficients of a typical wind turbine in a control method for a wind farm to participate in secondary frequency modulation of a power grid according to an embodiment of the present application;
FIG. 6 is a graph of mechanical power of a wind turbine at a constant wind speed in a control method for a wind farm to participate in secondary frequency modulation of a power grid according to an embodiment of the present application;
FIG. 7 is a schematic diagram of a typical wind farm in a control method for participating in secondary frequency modulation of a power grid in a wind farm according to an embodiment of the present disclosure;
fig. 8 is a schematic structural diagram of a control device for participating in secondary frequency modulation of a power grid in a wind farm according to an embodiment of the present application.
Detailed Description
In order to solve the technical problem that the research in the prior art focuses on the primary frequency modulation control strategy of the fan more and lacks of the research related to the secondary frequency modulation control strategy of the fan, the application discloses a control method and device for the wind power plant to participate in the secondary frequency modulation of a power grid through the following two embodiments.
The first embodiment of the application discloses a control method for wind power plant participation in secondary frequency modulation of a power grid, referring to a work flow diagram shown in fig. 1, the control method for wind power plant participation in secondary frequency modulation of the power grid comprises the following steps:
step S101, obtaining air density, fan blade radius and wind speed, and generating a fan mechanical power model according to the air density, the fan blade radius and the wind speed, wherein the fan mechanical power model is used for determining the relation between fan mechanical power and pitch angle.
In some embodiments of the present application, the generating a fan mechanical power model from the air density, the fan blade radius, and the wind speed includes:
Generating the fan mechanical power model by the following formula:
wherein P is m Representing the mechanical power of the fan, ρ representing the air density, pi representing the circumference ratio, R representing the radius of the fan blade, v representing the wind speed, θ representing the pitch angle, and e representing the natural constant.
Specifically, according to the aerodynamic model, the fan mechanical power is determined by the following formula:
wherein C is p (lambda, theta) represents the wind energy capture coefficient, w r Indicating the angular speed of the fan rotor.
When pitch angle control is considered, when the wind speed changes, the rotating speed of the fan also changes, and the tip speed ratio changes in a small range, so that the tip speed ratio is set to be a fixed value, and a mathematical expression that the wind energy capture coefficient is only related to the pitch angle theta can be obtained, as follows:
and determining and generating the expression in the fan mechanical power model according to the mathematical expression and the fan mechanical power formula under the aerodynamic model.
Step S102, obtaining an initial pitch angle, and determining the initial mechanical power of the fan according to the fan mechanical power model and the initial pitch angle.
Specifically, according to the fan mechanical power model, the fan initial mechanical power P can be calculated m0 。
Step S103, obtaining a pitch angle variation, a fan initial electromagnetic power and a fan electromagnetic power variation, and determining a pitch angle variation speed according to the fan mechanical power model, the fan initial electromagnetic power, the initial pitch angle, the pitch angle variation and the fan electromagnetic power variation.
Specifically, the initial electromagnetic power P of the fan can be obtained through measurement e0 Fan mechanical power P m And the electromagnetic power P of the fan e Can be represented by the following formula:
wherein H is t Representing a preset fan inertia constant, in this embodiment fan inertia constant H t In order to realize the load shedding mode, the standby capacity of the wind field/the total capacity of the wind field is flexibly determined according to the actual application scene.
In a control period T c In, the pitch angle θ can be expressed as:
θ＝θ 0 +△θ；
wherein θ 0 Representing the initial pitch angle and Δθ representing the pitch angle change, the following formula can be determined:
and then determining the pitch angle change speed by the following formula:
step S104, obtaining an electromagnetic power instruction value of the fan, and determining the change rate of the electromagnetic power according to the electromagnetic power instruction value of the fan.
Specifically, during pitch angle control, due to the fast tracking capability of the fan, the change of the electromagnetic power of the fan can fast track the command value P of the electromagnetic power of the fan sent by the upper stage ref And during a control period T c During this time, the electromagnetic power change rate may be assumed to be constant, i.e.:
wherein DeltaP ref And the electromagnetic power instruction value of the fan is represented.
Step S105, generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate.
In some embodiments of the present application, the generating a fan prediction model from the fan mechanical power model, the pitch angle change speed, and the electromagnetic power change rate includes:
generating the fan prediction model by the following formula:
△x i ＝A i △x i +B i △u i +E i ；
△y i ＝C i △x i ；
△x i ＝[△θ i △P e,i ] T ；
△u i ＝[△P ref,i ]；
△y i ＝[△θ i △P e,i ] T ；
wherein Deltax is i Representing the state variable of the ith fan, A i A first fan coefficient matrix representing an ith fan, B i A second fan coefficient matrix representing the ith fan, deltau i Represents the control variable of the ith fan, delta y i Representing the output variable of the ith fan, C i Represents a third fan coefficient matrix, delta theta i Represents the change quantity of the pitch angle of the ith fan, delta P e,i Shows the electromagnetic power variation quantity of the ith fan in a control period, delta P ref,i Representing a fan electromagnetic power instruction value, P, of an ith fan e0,i Represents the initial electromagnetic power of the ith fan, P m,i Represents the mechanical power of the ith fan, H t Represents a preset fan inertia constant, theta 0,t Represents the initial pitch angle of the ith fan, T c Representing the control period, E i Representing a fourth fan coefficient matrix.
And S106, generating a continuous state space model of the wind power plant according to the fan prediction model.
Specifically, based on the wind turbine prediction model, the wind farm continuous state space model may be expressed as:
△x＝A△x+B△u+E；
△y＝C△x；
△x＝[△x 1 ,△x 2 ,...,△x NC ] T ；
△u＝[△u 1 ,△u 2 ,...,△u NC ] T ；
△y＝[△y 1 ,△y 2 ,...,△y NC ] T ；
A＝diag[A 1 ,A 2 ,...,A Nc ]；
B＝diag[B 1 ,B 2 ,...,B Nc ]；
E＝diag[E 1 ,E 2 ,...,E Nc ]；
C＝diag[C 1 ,C 2 ,...,C Nc ]；
wherein Δx represents a state variable of the wind field, Δu represents a control variable of the wind field, Δy represents an output variable of the wind field, and A, B, C and E represent a first wind field coefficient matrix, a second wind field coefficient matrix, a third wind field coefficient matrix, and a fourth wind field coefficient matrix, respectively.
Step S107, generating a wind farm discrete time domain state space model according to the wind farm continuous state space model.
Specifically, based on a wind farm continuous state space model, conversion is performed to a sampling time interval delta T p Is a discrete time domain state space model of a wind farm as follows:
△x(k+1)＝G△x(k)+H△u(k)+E；
△y(k+1)＝C△x(k+1)；
wherein Δx (k) represents a state variable of a discrete wind field, Δu (k) represents a control variable of a discrete wind field, Δx (k+1) represents a state variable of a wind field predicted next time Δx (k), Δy (k+1) represents an output variable of a wind field predicted next time, G and H represent a fifth wind field coefficient matrix and a sixth wind field coefficient matrix, respectively, and τ represents a discretized sampling time interval.
Step S108, obtaining the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm and the pitch angle variation of any fan in the wind farm, and determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions.
In some embodiments of the present application, determining the total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the number of predictions of any fan in the wind farm, the pitch angle variation of any fan in the wind farm, and a preset constraint condition includes:
and determining a pitch angle average value according to the pitch angle of any fan in the wind power plant and the number of fans in the wind power plant.
Specifically, the pitch angle average is determined by the following formula:
wherein θ av Representing the pitch angle average value, N W And representing the number of fans in the wind farm.
And determining a first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value.
And determining a second objective function according to the number of fans in the wind power plant, the predicted times of any fan in the wind power plant and the change amount of the pitch angle of any fan in the wind power plant.
And determining the total objective function according to the first objective function and the second objective function.
In some embodiments of the present application, the determining a first objective function according to the number of fans in the wind farm, the number of predictions of any fan in the wind farm, a pitch angle of any fan in the wind farm, and the pitch angle average value includes:
and determining the first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value, and taking the minimum difference of the pitch angles among all fans in the wind power plant as the objective.
Specifically, the first objective function is determined by the following formula:
wherein Obj is the 1 Representing the first objective function, i representing the ith fan, k representing the kth prediction, N p Represents the predicted times of the fan, theta i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) The average value of the pitch angle at the kth prediction is shown.
The first objective function is to minimize the difference in pitch angle between fans to ensure stable operation of each fan in the wind farm. During normal operation, the fan is operated in a load shedding mode of operation, with its output power varying in accordance with the change in pitch angle. During the period of tracking active power of a wind farm, the pitch angle cannot be too low, so that the energy emitted by a fan is too much, and the left active power margin is too small; the pitch angle must not be too high to allow the energy emitted by the fan to be too low, resulting in offline. Therefore, in the absence of other objective functions, the pitch angle difference between fans is minimized, which means that all fans converge to the same pitch angle.
In some embodiments of the present application, the determining the second objective function according to the number of fans in the wind farm, the number of predictions of any fan in the wind farm, and the change in pitch angle of any fan in the wind farm includes
And determining the second objective function according to the number of fans in the wind farm, the prediction times of any fan in the wind farm and the change amount of the pitch angle of any fan in the wind farm, and taking the minimum change amount of the pitch angle of each fan in the wind farm as a target.
Specifically, the second objective function is determined by the following formula:
wherein Obj is the 2 Representing the second objective function, Δθ i (k) And representing the pitch angle variation of any fan in the wind power plant at the kth prediction.
The second objective function is to reduce the amount of change in pitch angle of the wind turbine itself in order to minimize the loss of wind energy.
In some embodiments of the present application, determining the total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the number of predictions of any fan in the wind farm, the pitch angle variation of any fan in the wind farm, and a preset constraint condition includes:
the overall objective function is determined by the following formula:
wherein N is W Representing the number of fans in the wind farm, i represents the ith fan and N p Represents the number of predictions of the fan, k represents the kth prediction, θ i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) Represents the pitch angle average value, Q, at the kth prediction 1 Representing a preset first weight coefficient, Q 2 Representing a preset second weight coefficient, the first weight coefficient Q 1 The second weight coefficient Q is determined in advance according to the actual application scene by taking the pitch angle difference between the fans as a target 2 The method is characterized in that the weight coefficient which aims at minimizing the change of the pitch angle of the fan is determined in advance according to the actual application scene.
Further, the constraint conditions comprise capacity constraint of the wind turbine, capacity constraint of the wind power plant, reserve capacity constraint of the wind power plant, electromagnetic power command value constraint of the wind turbine and electromagnetic power command value tracking constraint.
Specifically, the capacity constraint of a fan can be expressed as:
P min,i ≤P i ≤P max,i ；
wherein P is i Representing the capacity of the ith fan, P min,i And P max,i The minimum mechanical power and the maximum mechanical power of the ith fan are respectively represented.
The capacity constraints of a wind farm can be expressed as:
P min ≤P≤P max ；
wherein P represents the capacity of the wind farm, P min And P max Representing the minimum mechanical power and the maximum mechanical power of the wind farm, respectively.
The fan backup capacity constraint may be expressed as:
P r,min,i ≤P r,i ≤P r,max,i ；
wherein P is r,i Represents the spare capacity of the ith fan, P r,min,i And P r,max,i The minimum and maximum standby capacities of the ith blower are respectively shown.
The reserve capacity constraint of a wind farm can be expressed as:
P r,min ≤P r ≤P r,max ；
wherein P is r Representing reserve capacity of wind farm, P r,min And P r,max Representing minimum and maximum values of reserve capacity of the wind farm, respectively. The fan electromagnetic power command value constraint may be expressed as:
P ref,min ≤P ref ≤P ref,max ；
Wherein P is ref Representing the electromagnetic power instruction value of the fan, P ref,min And P ref,max Respectively representing the minimum value and the maximum value of the electromagnetic power command value of the fan.
For a wind power plant, an active power instruction value delta P of a fan of an ith fan in the wind power plant ref,i And should track the fan mechanical power reference value P given by the upper system ref To achieve a frequency ofThe purpose of the rate adjustment. Tracking electromagnetic power command value constraints may be expressed as:
the above steps of the embodiment deduce the prediction model of the fan and the wind farm in detail by researching the relation between the electromagnetic power and the pitch angle of the fan. In order to achieve the proposed control objective, a relatively accurate electric wind field model is established, and a secondary frequency modulation method based on MPC pitch angle control is provided on the basis of a prediction model. The MPC is a widely applied control method, and at each application moment, according to the obtained current measurement information, a finite time open loop optimization problem is solved on line, and the first element of the obtained control sequence acts on the controlled object. At the next sampling moment, repeating the process, taking the new measured value as an initial condition for predicting the future dynamic state of the system at the moment, refreshing the optimization problem and solving again.
Specifically, the principle of MPC is shown in FIG. 2, u is the control sequence, where t 0 For the initial moment, x (t 0 ) For the state value of the initial time, x (1) and x (2) are the state values of the corresponding time, x is the prediction state, and the sampling time interval is DeltaT p . In order to accurately predict the dynamic change of the wind power plant, a proper control period T is set c And prediction period T p . The control period is smaller than the frequency modulation time and larger than the sampling time, and the prediction period is determined by the dynamic performance of the wind power control system. During one prediction period, only the first control period is active and then remains unchanged.
Step S109, determining a pitch angle reference value according to the wind farm discrete time domain state space model and the total objective function.
And step S110, determining a fan mechanical power reference value according to the fan mechanical power model and the pitch angle reference value.
And S111, acquiring an actual fan mechanical power value, and determining a pitch angle correction amount according to the actual fan mechanical power value and the fan mechanical power reference value.
In some embodiments of the present application, the determining a pitch angle correction based on the actual fan mechanical power value and the fan mechanical power reference value includes.
And determining a pitch angle correction amount according to the difference value between the actual fan mechanical power value and the reference fan mechanical power value.
And step S112, correcting the pitch angle reference value according to the pitch angle correction amount, and determining a pitch angle target value, wherein the pitch angle target value is used for adjusting the electromagnetic power of any fan in the wind power plant, so as to complete the secondary frequency modulation control of the power grid.
Specifically, when the wind farm participates in secondary frequency modulation of the power grid, an active power instruction value P issued by a superior system is received ref According to the method provided by the embodiment, the mechanical power reference value P of each fan in the wind power plant can be obtained ref,i . According to the electromagnetic power instruction value P of the fan issued by the upper system ref Obtaining a pitch angle reference value theta of the fan ref Obtaining the pitch angle command value theta of each fan ref,i . For the wind energy utilization coefficient C p The complex nonlinear relation between (lambda, theta) and the pitch angle theta and the tip speed ratio lambda is introduced into a pitch angle compensation link, the pitch angle correction quantity theta 'is determined, and the pitch angle correction quantity theta' is based on the actual power P_wt of the fan and the electromagnetic power command value P of the fan, which is issued by an upper system ref The difference between them is obtained. The fan can respond to the frequency change and reach the instruction value P issued by the upper system ref See fig. 3. Theta in the figure max Represents the maximum value of the pitch angle, θ min Representing the minimum value of the pitch angle.
The specific process is as follows: firstly, according to the electromagnetic power instruction value P of the fan under the current wind speed ref Determining a pitch angle reference value theta required by the unit to complete the frequency modulation task ref The method comprises the steps of carrying out a first treatment on the surface of the Because of the existence of errors, a pitch angle compensation link is introduced, and then a fan electromagnetic power instruction value P is used according to the current wind speed ref The difference value of the power P_wt actually sent by the fan is used for determining a pitch angle correction quantity theta', and the pitch angle of the fan is adjustedA value θ; and finally, the fan operates according to the corrected pitch angle reference value, and the electromagnetic power of the fan is regulated to realize the requirement of secondary frequency modulation.
The embodiment can better coordinate the electromagnetic power between fans in the wind power plant so as to avoid excessive change of the pitch angle of the fans and achieve the purpose of reducing wind energy loss. In a power grid with high wind power permeability, the pitch angle control of the doubly fed fan can rapidly respond to the frequency change value, so that dynamic frequency deviation is further reduced, the condition of load shedding caused by too low frequency drop is avoided, and the task of secondary frequency modulation is completed.
Typically, fans operate in a maximum power tracking mode, and when a system frequency dip occurs, additional active power support cannot be provided to participate in grid secondary frequency modulation. Therefore, the fan must take load shedding measures to obtain enough active reserve. Fans are typically operated in a de-load state by two control methods: overspeed load shedding control and pitch angle load shedding control. The two methods can realize the load shedding operation of the fan in different wind speed areas, so that the fan can be reserved with a certain active standby, released through a certain control when needed, and used for adjusting the system frequency. In the medium speed region, in order to enable the fan to be available as standby active power when participating in system frequency adjustment, overspeed load shedding enables the fan to operate at a non-optimal power point by controlling the rotating speed of a rotor, active output of a unit is reduced, and active power standby is increased; with increasing wind speed, the rotational speed of the generator rotor increases. When the wind speed is higher than the rated wind speed, the rotating speed of the rotor of the generator set reaches the rated rotating speed, and the load shedding operation of the fan can not be realized through an overspeed load shedding method any more, and can only be realized through pitch angle control. The pitch angle load shedding is realized by increasing or decreasing the output of the unit by adjusting the pitch angle. The pitch angle control has stronger adjusting capability and larger adjusting range, can realize power control at full wind speed, and the variable pitch control system can improve the wind energy utilization rate of a large fan and reduce the influence of wind gusts and load fluctuation on the fan. The invention therefore aims to operate the fan in a de-loaded condition by setting an initial pitch angle for the fan.
In order to enable the fan to obtain enough active reserve, the adjustment capability of the fan to the system frequency is fully exerted, the requirement of secondary frequency modulation of the power grid to a new energy power station is met, and the pitch angle load shedding control mode with stronger adjustment capability and wider adjustment range is selected to realize active reserve to the fan.
In summary, when the fan operates in the maximum power tracking mode and the system frequency falls, additional active power support cannot be provided to participate in the secondary frequency modulation of the power grid. By setting the initial pitch angle, 20% of power reserve is reserved for frequency adjustment of the fan, and when the load of the system suddenly increases, the control link responds to the frequency change, the pitch angle of the fan is reduced, and active power output is further increased. As the pitch angle is adjusted, the method has the advantages of strong adjustment capability, long duration time and the like, and meets the requirement of secondary frequency modulation of the system.
The specific process for determining that the fan adopts the pitch angle control method to realize secondary frequency modulation of the power grid comprises the following steps: analyzing a mechanical power curve of the fan at a constant wind speed, and knowing that different pitch angles have corresponding optimal tip speed ratios so as to maximize a wind energy utilization coefficient; and when the pitch angle is 0 degrees, the corresponding optimal wind energy capture coefficient is maximum, and the optimal wind energy capture coefficient rapidly decreases along with the increase of the pitch angle. Therefore, the pitch angle control of the fan can adjust the mechanical energy captured by the fan, so that the active power injected into the power grid by the fan is adjusted, and the control mode can stably change the output power of the fan, so that the wind power plant can be supported to participate in secondary frequency modulation of the power grid. And setting an initial pitch angle, so that the fan reserves enough power reserve for frequency adjustment, and when the system load suddenly increases, the control link responds to the frequency change, reduces the pitch angle of the fan, and further increases the active power output.
The electromagnetic power adjusting range of the fan is shown in fig. 4, and active adjustment of 20% -100% of rated capacity can be realized in a larger wind speed range through pitch angle adjustment. Referring to fig. 5, which is a wind energy capture coefficient curve of a wind turbine, it can be seen that when the pitch angle is 0 °, the corresponding optimal wind energy capture coefficient is maximum, and the optimal wind energy capture coefficient rapidly decreases as the pitch angle increases. The pitch angle control of the fans can adjust the mechanical energy captured by the fans, namely the mechanical power of the fans, so as to adjust the active power injected into the power grid by the fans. The wind turbine can be operated in a load shedding state by an overspeed load shedding method and a pitch angle load shedding method, and the pitch angle control method is adopted in the embodiment because the adjustment capability of pitch angle control is strong, the adjustment range is also large, the power control under the full wind speed can be realized, the wind energy utilization rate of the large wind turbine can be improved by the variable pitch control system, and the influence of wind gusts and load fluctuation on the wind turbine can be reduced.
The pitch angle control is to control the mechanical power of the fan by adjusting the pitch angle of the fan blade when the tip speed ratio is kept at the optimal value all the time, thereby realizing the active power control of the fan. As shown in FIG. 6, the mechanical power curve of the wind turbine at a constant wind speed is shown, the wind turbine is operated at an operating point A, the corresponding pitch angle is 0 DEG, and the mechanical power of the wind turbine is P m,max . When the active control command of the fan is reduced to P cmd,1 、P cmd,2 And P cmd,3 At this time, the fan should be raised in pitch angle so that its fan mechanical power is reduced, corresponding to an operating point of B, C, D. When the active control instruction of the fan is at P m,max And P cmd,3 In between, the fan should work on the curves A-B-C-D, and all the adjustment processes are reversible.
This embodiment finds application in a typical wind farm configuration as shown in fig. 7: the wind farm is connected to an external 110kv ac grid via a 33kv/110kv transformer, again by 20 km 110kv overhead lines. The wind power plant consists of 10 fans and two feeder lines, wherein each feeder line is connected with 5 fans with rated capacity of 5MW, and the distance between each fan is 2 kilometers.
According to the control method for the wind power plant to participate in the secondary frequency modulation of the power grid, which is disclosed by the embodiment of the application, firstly, a fan mechanical power model is established, and the relation between the fan mechanical power and the pitch angle is determined. And then, a fan prediction model is established according to the fan electromagnetic power instruction value, and a wind field prediction model is determined on the basis of the fan prediction model. And further determining a total objective function by taking the minimum difference of pitch angles among all fans in the wind power plant and the minimum change of pitch angles of all fans in the wind power plant as targets. And determining a pitch angle reference value according to the wind field prediction model and the total objective function. And finally, correcting the pitch angle reference value, and determining a pitch angle target value, thereby realizing secondary frequency modulation control of the power grid. According to the method and the device, on the basis that the wind power plant realizes power grid frequency adjustment, the electromagnetic power between fans in the wind power plant can be better coordinated, the excessive change of the pitch angle of the fans is avoided, the wind energy loss is reduced to the greatest extent, and the electromagnetic power instruction value of the fans which are delivered from the upper level can be tracked more quickly and stably.
The following are device embodiments of the present application, which may be used to perform method embodiments of the present application. For details not disclosed in the device embodiments of the present application, please refer to the method embodiments of the present application.
The second embodiment of the application discloses a wind farm participates in control device of electric wire netting secondary frequency modulation, wind farm participates in control method of electric wire netting secondary frequency modulation that wind farm disclosed in this first embodiment is applied to, see the structure schematic diagram that fig. 8 shows, wind farm participates in control device of electric wire netting secondary frequency modulation includes:
the fan mechanical power model generation module 801 is configured to obtain an air density, a fan blade radius, and a wind speed, and generate a fan mechanical power model according to the air density, the fan blade radius, and the wind speed, where the fan mechanical power model is used to determine a fan mechanical power model.
Further, the fan mechanical power model generating module 801 is configured to generate the fan mechanical power model according to the following formula:
wherein P is m Representing the mechanical power of the fan, ρ representing the air density, pi representing the circumference ratio, R representing the radius of the fan blade, v representing the wind speed, θ representing the pitch angle, and e representing the natural constant.
An initial mechanical power determination module 802 is configured to obtain an initial pitch angle, and determine an initial mechanical power of the fan according to the fan mechanical power model and the initial pitch angle.
The pitch angle change speed obtaining module 803 is configured to obtain a pitch angle change amount, a fan initial electromagnetic power, and a fan electromagnetic power change amount, and determine a pitch angle change speed according to the fan mechanical power model, the fan initial electromagnetic power, the initial pitch angle, the pitch angle change amount, and the fan electromagnetic power change amount.
The electromagnetic power change rate obtaining module 804 is configured to obtain an electromagnetic power command value of the fan, and determine an electromagnetic power change rate according to the electromagnetic power command value of the fan.
And a fan prediction model generating module 805, configured to generate a fan prediction model according to the fan mechanical power model, the pitch angle change speed, and the electromagnetic power change rate.
Further, the fan prediction model generating module 805 is configured to generate a fan prediction model according to the following formula:
△x i ＝A i △x i +B i △u i +E i ；
△y i ＝C i △x i ；
△x i ＝[△θ i △P e,i ] T ；
△u i ＝[△P ref,i ]；
△y i ＝[△θ i △P e,i ] T ；
/>
wherein Deltax is i Representing the state variable of the ith fan, A i A first fan coefficient matrix representing an ith fan, B i A second fan coefficient matrix representing the ith fan, deltau i Represents the control variable of the ith fan, delta y i Representing the output variable of the ith fan, C i Represents a third fan coefficient matrix, delta theta i Represents the change quantity of the pitch angle of the ith fan, delta P e,i Shows the electromagnetic power variation quantity of the ith fan, delta P ref,i Representing a fan electromagnetic power instruction value, P, of an ith fan e0,i Represents the initial electromagnetic power of the ith fan, P m,i Represents the mechanical power of the ith fan, H t Represents a preset fan inertia constant, theta 0,t Represents the initial pitch angle of the ith fan, T c Representing the control period, E i Representing a fourth fan coefficient matrix.
And the wind power plant continuous model generating module 806 is configured to generate a wind power plant continuous state space model according to the fan prediction model.
A wind farm discrete model generating module 807 configured to generate a wind farm discrete time domain state space model according to the wind farm continuous state space model.
The total objective function determining module 808 is configured to obtain a pitch angle of any fan in the wind farm, the number of fans in the wind farm, a predicted number of times of any fan in the wind farm, and a pitch angle variation of any fan in the wind farm, and determine a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm, and a preset constraint condition.
Further, the overall objective function determination module 808 includes:
and the pitch angle average value determining unit is used for determining a pitch angle average value according to the pitch angle of any fan in the wind farm and the number of fans in the wind farm.
The first objective function determining unit is used for determining a first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value.
And the second objective function determining unit is used for determining a second objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant and the change amount of the pitch angle of any fan in the wind power plant.
And the total objective function acquisition unit is used for determining the total objective function according to the first objective function and the second objective function.
Further, the first objective function determining unit includes:
and determining the first objective function by taking the minimum difference of the pitch angles among all fans in the wind power plant as a target according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the average value of the pitch angles.
Further, the second objective function determining unit includes:
and the second objective function is determined by taking the minimum change of the pitch angle of each fan in the wind farm as a target according to the number of fans in the wind farm, the prediction times of any fan in the wind farm and the change of the pitch angle of any fan in the wind farm.
Further, the constraint conditions comprise capacity constraint of the wind turbine, capacity constraint of the wind power plant, reserve capacity constraint of the wind power plant, electromagnetic power command value constraint of the wind turbine and electromagnetic power command value tracking constraint.
Further, the total objective function determining module is configured to determine the total objective function by the following formula:
wherein N is W Representing the number of fans in the wind farm, i represents the ith fan and N p Represents the number of predictions of the fan, k represents the kth prediction, θ i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) Represents the pitch angle average value, Q, at the kth prediction 1 Representing a preset first weight coefficient, Q 2 Representing a preset second weight coefficient, the first weight coefficient Q 1 Refers to a weight coefficient aiming at minimizing the pitch angle difference between fans, and the second weight coefficient Q 2 Refers to a weight coefficient that aims to minimize the change in the pitch angle of the fan itself.
A pitch angle reference value determination module 809 for determining a pitch angle reference value from the wind farm discrete time domain state space model and the total objective function.
The fan mechanical power reference value determining module 810 is configured to determine a fan mechanical power reference value according to the fan mechanical power model and the pitch angle reference value.
The pitch angle correction amount determining module 811 is configured to obtain an actual value of fan mechanical power, and determine a pitch angle correction amount according to the actual value of fan mechanical power and the reference value of fan mechanical power.
Further, the pitch angle correction amount determination module 811 includes:
and the pitch angle correction amount is determined according to the difference value between the actual fan mechanical power value and the fan mechanical power reference value.
And the secondary frequency modulation control module 812 is configured to correct the pitch angle reference value according to the pitch angle correction amount, and determine a pitch angle target value, where the pitch angle target value is used to adjust electromagnetic power of any fan in the wind farm, so as to complete secondary frequency modulation control of the power grid.
The foregoing detailed description has been provided for the purposes of illustration in connection with specific embodiments and exemplary examples, but such description is not to be construed as limiting the application. Those skilled in the art will appreciate that various equivalent substitutions, modifications and improvements may be made to the technical solution of the present application and its embodiments without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The scope of the application is defined by the appended claims.

Claims (6)

1. A control method for wind power plant participation in secondary frequency modulation of a power grid is characterized by comprising the following steps:
acquiring air density, a radius of a fan blade and wind speed, and generating a fan mechanical power model according to the air density, the radius of the fan blade and the wind speed, wherein the fan mechanical power model is used for determining the relation between fan mechanical power and pitch angle;
acquiring an initial pitch angle, and determining the initial mechanical power of the fan according to the fan mechanical power model and the initial pitch angle;
acquiring a pitch angle variation, a fan initial electromagnetic power and a fan electromagnetic power variation, and determining a pitch angle variation speed according to the fan mechanical power model, the fan initial electromagnetic power, the initial pitch angle, the pitch angle variation and the fan electromagnetic power variation;
acquiring an electromagnetic power instruction value of a fan, and determining an electromagnetic power change rate according to the electromagnetic power instruction value of the fan;
generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate;
generating a wind power plant continuous state space model according to the fan prediction model;
Generating a wind power plant discrete time domain state space model according to the wind power plant continuous state space model;
obtaining the pitch angle of any fan in a wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm and the pitch angle variation of any fan in the wind farm, and determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions;
determining a pitch angle reference value according to the wind farm discrete time domain state space model and the total objective function;
determining a fan mechanical power reference value according to the fan mechanical power model and the pitch angle reference value;
acquiring an actual value of the mechanical power of the fan, and determining a pitch angle correction amount according to the actual value of the mechanical power of the fan and the reference value of the mechanical power of the fan;
correcting the pitch angle reference value according to the pitch angle correction amount, and determining a pitch angle target value, wherein the pitch angle target value is used for adjusting the electromagnetic power of any fan in a wind power plant to complete secondary frequency modulation control of a power grid;
Determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions, wherein the total objective function comprises:
determining a pitch angle average value according to the pitch angle of any fan in the wind power plant and the number of fans in the wind power plant;
determining a first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value;
determining a second objective function according to the number of fans in the wind power plant, the predicted times of any fan in the wind power plant and the change amount of the pitch angle of any fan in the wind power plant;
determining the total objective function according to the first objective function and the second objective function;
generating a fan mechanical power model according to the air density, the fan blade radius and the wind speed, wherein the fan mechanical power model comprises the following steps:
generating the fan mechanical power model by the following formula:
wherein P is m Representing the mechanical power of the fan, ρ representing the air density, pi representing the circumference ratio, R representing the radius of the fan blade, v representing the wind speed, θ representing the pitch angle, e representing the natural constant;
Generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate, wherein the fan prediction model comprises the following steps:
generating the fan prediction model by the following formula:
△x i ＝A i △x i +B i △u i +E i ；
△y i ＝C i △x i ；
△x i ＝[△θ i △P e,i ] T ；
△u i ＝[△P ref,i ]；
△y i ＝[△θ i △P e,i ] T ；
wherein Deltax is i Representing the state variable of the ith fan, A i A first fan coefficient matrix representing an ith fan, B i A second fan coefficient matrix representing the ith fan, deltau i Represents the control variable of the ith fan, delta y i Representing the output variable of the ith fan, C i Represents a third fan coefficient matrix, delta theta i Represents the change quantity of the pitch angle of the ith fan, delta P e,i Shows the electromagnetic power variation quantity of the ith fan, delta P ref,i Representing a fan electromagnetic power instruction value, P, of an ith fan e0,i Represents the initial electromagnetic power of the ith fan, P m,i Represents the mechanical power of the ith fan, H t Represents a preset fan inertia constant, theta 0,i Represents the initial pitch angle of the ith fan, T c Representing the control period, E i Representing a fourth fan coefficient matrix;
determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions, wherein the total objective function comprises:
The overall objective function is determined by the following formula:
wherein N is W Representing the number of fans in the wind farm, i represents the ith fan and N p Represents the number of predictions of the fan, k represents the kth prediction, θ i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) Represents the pitch angle average value, Q, at the kth prediction 1 Representing a preset first weight coefficient, Q 2 Representing a preset second weight coefficient, the first weight coefficient Q 1 Refers to a weight coefficient aiming at minimizing the pitch angle difference between fans, and the second weight coefficient Q 2 Is the most inAnd (5) minimizing the change of the pitch angle of the fan to be a weight coefficient of the target.
2. The method for controlling the wind farm to participate in secondary frequency modulation of a power grid according to claim 1, wherein the constraint conditions comprise capacity constraint of a wind turbine, capacity constraint of the wind farm, reserve capacity constraint of the wind farm, electromagnetic power command value constraint of the wind turbine and electromagnetic power command value tracking constraint.
3. The method for controlling a wind farm to participate in secondary frequency modulation of a power grid according to claim 1, wherein determining a first objective function according to the number of fans in the wind farm, the number of predictions of any fan in the wind farm, a pitch angle of any fan in the wind farm, and an average value of the pitch angles comprises:
And determining the first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value, and taking the minimum difference of the pitch angles among all fans in the wind power plant as the objective.
4. The method for controlling a wind farm to participate in secondary frequency modulation of a power grid according to claim 1, wherein the determining a second objective function according to the number of fans in the wind farm, the number of predictions of any fan in the wind farm, and the change of pitch angle of any fan in the wind farm comprises
And determining the second objective function according to the number of fans in the wind farm, the prediction times of any fan in the wind farm and the change amount of the pitch angle of any fan in the wind farm, and taking the minimum change amount of the pitch angle of each fan in the wind farm as a target.
5. The method for controlling a wind farm to participate in secondary frequency modulation of a power grid according to claim 1, wherein determining a pitch angle correction according to the actual value of the fan mechanical power and the reference value of the fan mechanical power comprises;
and determining a pitch angle correction amount according to the difference value between the actual fan mechanical power value and the reference fan mechanical power value.
6. A control device for enabling a wind farm to participate in secondary frequency modulation of a power grid, which is characterized in that the control device for enabling the wind farm to participate in secondary frequency modulation of the power grid is applied to the control method for enabling the wind farm to participate in secondary frequency modulation of the power grid according to any one of claims 1-5, and the control device for enabling the wind farm to participate in secondary frequency modulation of the power grid comprises:
the fan mechanical power model generation module is used for acquiring air density, fan blade radius and wind speed, and generating a fan mechanical power model according to the air density, the fan blade radius and the wind speed, wherein the fan mechanical power model is used for determining a fan mechanical power model;
the initial mechanical power determining module is used for acquiring an initial pitch angle and determining the initial mechanical power of the fan according to the fan mechanical power model and the initial pitch angle;
the pitch angle change speed acquisition module is used for acquiring a pitch angle change amount, a fan initial electromagnetic power and a fan electromagnetic power change amount, and determining a pitch angle change speed according to the fan mechanical power model, the fan initial electromagnetic power, the initial pitch angle, the pitch angle change amount and the fan electromagnetic power change amount;
The electromagnetic power change rate acquisition module is used for acquiring an electromagnetic power instruction value of the fan and determining the electromagnetic power change rate according to the electromagnetic power instruction value of the fan;
the fan prediction model generation module is used for generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate;
the wind power plant continuous model generation module is used for generating a wind power plant continuous state space model according to the fan prediction model;
the wind power plant discrete model generation module is used for generating a wind power plant discrete time domain state space model according to the wind power plant continuous state space model;
the total objective function determining module is used for obtaining the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm and the pitch angle variation of any fan in the wind farm, and determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted number of times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions;
the pitch angle reference value determining module is used for determining a pitch angle reference value according to the wind power plant discrete time domain state space model and the total objective function;
The fan mechanical power reference value determining module is used for determining a fan mechanical power reference value according to the fan mechanical power model and the pitch angle reference value;
the pitch angle correction amount determining module is used for obtaining the actual value of the mechanical power of the fan and determining the pitch angle correction amount according to the actual value of the mechanical power of the fan and the mechanical power reference value of the fan;
the secondary frequency modulation control module is used for correcting the pitch angle reference value according to the pitch angle correction amount, determining a pitch angle target value, wherein the pitch angle target value is used for adjusting the electromagnetic power of any fan in the wind power plant, and finishing secondary frequency modulation control of the power grid;
determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions, wherein the total objective function comprises:
determining a pitch angle average value according to the pitch angle of any fan in the wind power plant and the number of fans in the wind power plant;
determining a first objective function according to the number of fans in the wind power plant, the prediction times of any fan in the wind power plant, the pitch angle of any fan in the wind power plant and the pitch angle average value;
Determining a second objective function according to the number of fans in the wind power plant, the predicted times of any fan in the wind power plant and the change amount of the pitch angle of any fan in the wind power plant;
determining the total objective function according to the first objective function and the second objective function;
generating a fan mechanical power model according to the air density, the fan blade radius and the wind speed, wherein the fan mechanical power model comprises the following steps:
generating the fan mechanical power model by the following formula:
wherein P is m Representing the mechanical power of the fan, ρ representing the air density, pi representing the circumference ratio, R representing the radius of the fan blade, v representing the wind speed, θ representing the pitch angle, e representing the natural constant;
generating a fan prediction model according to the fan mechanical power model, the pitch angle change speed and the electromagnetic power change rate, wherein the fan prediction model comprises the following steps:
generating the fan prediction model by the following formula:
△x i ＝A i △x i +B i △u i +E i ；
△y i ＝C i △x i ；
△x i ＝[△θ i △P e,i ] T ；
△u i ＝[△P ref,i ]；
△y i ＝[△θ i △P e,i ] T ；
wherein Deltax is i Representing the state variable of the ith fan, A i A first fan coefficient matrix representing an ith fan, B i A second fan coefficient matrix representing the ith fan, deltau i Represents the control variable of the ith fan, delta y i Representing the output variable of the ith fan, C i Represents a third fan coefficient matrix, delta theta i Represents the change quantity of the pitch angle of the ith fan, delta P e,i Shows the electromagnetic power variation quantity of the ith fan, delta P ref,i Representing a fan electromagnetic power instruction value, P, of an ith fan e0,i Represents the initial electromagnetic power of the ith fan, P m,i Represents the mechanical power of the ith fan, H t Represents a preset fan inertia constant, theta 0,i Represents the initial pitch angle of the ith fan, T c Representing the control period, E i Representing a fourth fan coefficient matrix;
determining a total objective function according to the pitch angle of any fan in the wind farm, the number of fans in the wind farm, the predicted times of any fan in the wind farm, the pitch angle variation of any fan in the wind farm and preset constraint conditions, wherein the total objective function comprises:
the overall objective function is determined by the following formula:
wherein N is W Representing the number of fans in the wind farm, i represents the ith fan and N p Represents the number of predictions of the fan, k represents the kth prediction, θ i (k) Represents the pitch angle theta of the ith fan in the kth prediction av (k) Represents the pitch angle average value, Q, at the kth prediction 1 Representing a preset first weight coefficient, Q 2 Representing a preset second weight coefficient, the first weight coefficient Q 1 Refers to a weight coefficient aiming at minimizing the pitch angle difference between fans, and the second weight coefficient Q 2 Refers to a weight coefficient that aims to minimize the change in the pitch angle of the fan itself.
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