CN111725847A - Frequency control method considering double-fed fan kinetic energy throughput capacity - Google Patents
Frequency control method considering double-fed fan kinetic energy throughput capacity Download PDFInfo
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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
- H02J3/38—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
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
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Abstract
The invention particularly relates to a frequency control method considering the kinetic energy throughput capacity of a double-fed fan. The invention respectively controls the frequency when the frequency deviation is positive and negative; when the frequency deviation is positive, redundant active power is absorbed from the power grid and stored in the fan, and the system active power redundancy is reduced; when the frequency deviation is negative, the rotating part of the fan effectively releases kinetic energy to the power grid to compensate the active power shortage of the system; therefore, active frequency control of the double-fed wind generating set is realized, frequency stability is improved, and response time is provided for the synchronous generator to participate in system frequency modulation. Different frequency control parameters are adopted to provide the system frequency supporting capability; the proposed frequency control parameters can fully utilize the capacity of the fan for storing and releasing rotational energy to carry out frequency control; when the frequency deviation is negative, the proposed control parameters can prevent the fan from stalling; the frequency deviation is positive, the provided control parameters can avoid excessive starting pitch angle control, and the problem of mechanical fatigue of the fan is reduced.
Description
Technical Field
The invention particularly relates to a frequency control method considering the kinetic energy throughput capacity of a double-fed fan, and belongs to the technical field of wind power generation control.
Background
With the increasing wind power grid-connected capacity, the traditional synchronous generator set is continuously replaced by a wind generator set, and nevertheless, the inherent characteristics of intermittency, randomness and volatility of wind energy bring great challenges to the safe operation of a power system. The doubly-fed wind generator is a fan which is most widely applied in the current market; the unit has the advantages of high efficiency and advanced control technology; however, the maximum power tracking operation of the rotor-side converter is realized at different wind speeds, and the rotor speed is not coupled with the system frequency, so that the system rotational inertia and the system frequency modulation capability are reduced, and the frequency deviation is easy to exceed the safety range during disturbance; in addition, compared with a conventional thermal power unit, the wind power unit has poor high-frequency and low-frequency bearing capacity, and is easily affected by frequency abnormity during disturbance, so that a large-scale fan off-grid phenomenon is caused, serious active power loss is caused, the system frequency is suddenly reduced, and a serious interlocking problem of a power system is caused. Therefore, with the change of the system structure of the power system and the continuous grid connection of wind power, the stability of the grid frequency tends to face a huge challenge.
Under the condition of the same installed capacity, the inertia time constant of the wind driven generator is far larger than that of the synchronous generator, and the wind driven generator has a wider rotation speed safe operation range. Therefore, the doubly-fed wind turbine can be regarded as an effective means for supporting the system frequency. The control method based on frequency deviation is added in a double-fed fan converter controller to enable the rotating speed of a fan to be rigidly coupled with the frequency, the control method determines the working mode of the fan through the positive and negative of the frequency deviation, namely, when the frequency deviation is positive, the active power of system redundancy is stored in a fan rotor; when the frequency deviation is negative, the stored rotational kinetic energy in the fan is released into the power grid, the active shortage of the system is compensated, the frequency stability is improved, and the active standby of the system is reduced, so that the frequency control of the wind generating set becomes one of the current research hotspots. At present, the existing technical method for controlling the system frequency cannot fully utilize the rotational kinetic energy of a fan due to the influence of constant control parameters, so that the capacity of the fan for providing the system frequency control is restricted, or the rotational kinetic energy in the fan is excessively released by the fan, and the problem that the fan participates in the system frequency control excessively is caused; therefore, how to set the frequency control parameter of the fan is an urgent problem to be solved in the future.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a frequency control method considering the kinetic energy throughput capacity of a double-fed fan. When the frequency deviation is positive, the adopted frequency control parameter is in a direct proportional relation with the potential of the fan for storing kinetic energy, and the purpose is to store proper rotational kinetic energy according to different operating conditions of the fan; the redundant active power of the system is reduced, the starting times and time of the pitch angle are reduced, and the frequency stability is improved; when the frequency deviation is negative, the adopted frequency control parameter is in a positive proportional relation with the potential of the fan to release kinetic energy, the purpose is to release proper rotational kinetic energy according to different fan operation conditions, compensate the active power loss of a system, avoid the phenomenon of fan stall, reduce the maximum frequency deviation and realize the controllable frequency control of the wind generating set.
In order to achieve the purpose, the invention adopts the following technical scheme:
a frequency control method for considering the kinetic energy throughput capacity of a doubly-fed wind turbine comprises the following steps: s1: calculating the instantaneous frequency of a system power grid according to the voltage of a public coupling point of the wind power plant and the power grid, and starting the system frequency control of the fan when the instantaneous frequency of the power grid exceeds a set dead zone range; if the current is within the set dead zone range, continuously working in the maximum power tracking control; s2: calculating a system frequency deviation delta f according to the instantaneous frequency of the power grid, and judging the positive and negative of the system frequency deviation delta f; s3: respectively calculating frequency control parameters AG adopted when the frequency deviation delta f of the system is positive according to the rotor rotating speed of the collected fanOF(ωr) Frequency control parameter AG used when sum system frequency deviation Δ f is negativeUF(ωr)；
In the formula (1), AGOF(ωr) The frequency control parameter used for the timing of the frequency deviation Δ f, and K is a frequency control factor, which is used to adjust the frequency control effect, ωrIs the rotational speed of the fan rotor, omegamaxIs the maximum rotor speed;
in the formula (2), AGUF(ωr) Is a frequency control parameter used when the frequency deviation deltaf is negative, and K is a frequency control factor used to adjust the frequency control effect, omegarIs the rotational speed of the fan rotor, omegaminIs the minimum rotor speed;
s4: judging to adopt a frequency control parameter AG according to the positive and negative of the calculated system frequency deviation delta fOF(ωr) Or frequency control parameter AGUF(ωr) Obtaining the active variable quantity of the system frequency control, adding the active increment to the maximum power tracking control to calculate the active power output value P of the fanrefThe specific formula is as follows:
in formula (3), PMPPTTracking output power for maximum power, AGOF(ωr) Frequency control parameter, AG, for use when frequency deviation Δ f is positiveUF(ωr) For the frequency control parameter, ω, used when the frequency deviation Δ f is negativerThe rotational speed of the fan rotor.
As a preferred technical scheme of the invention: the specific steps of step S3 are as follows: s3.1: rotor rotating speed omega of collecting fanrMastering the maximum rotor speed omega of the fanmaxAnd minimum rotor speed ωmin(ii) a S3.2: analyzing the potential of stored energy and released energy of the fan according to the operating characteristics of the fan; s3.3: when the calculated system frequency deviation delta f is larger than zero, the potential of the fan for storing energy is considered, and the adopted frequency control is adoptedSystem parameter AGOF(ωr) The energy storage potential of the wind turbine is in direct proportion, and the expression is as follows:
in the formula (1), AGOF(ωr) The frequency control parameter used for the timing of the frequency deviation Δ f, and K is a frequency control factor, which is used to adjust the frequency control effect, ωrIs the rotational speed of the fan rotor, omegamaxIs the maximum rotor speed;
when the calculated system frequency deviation delta f is less than zero, the potential of the fan for releasing energy is considered, and the adopted frequency control parameter AGUF(ωr) The energy releasing potential of the fan is in direct proportion, and the expression is as follows:
in the formula (2), AGUF(ωr) Is a frequency control parameter used when the frequency deviation deltaf is negative, and K is a frequency control factor used to adjust the frequency control effect, omegarIs the rotational speed of the fan rotor, omegaminIs the minimum rotor speed.
As a preferred technical scheme of the invention: in step S2, after the system frequency deviation Δ f is calculated, filtering processing needs to be performed on the system frequency deviation Δ f, and whether to start frequency control of the fan is determined according to the processed system frequency deviation Δ f.
As a preferred technical scheme of the invention: in the step S4, calculating an active power output value P of the wind turbinerefIn order to prevent overloading of the fan and to reduce mechanical fatigue, the calculated active power output value PrefIt is limited by the maximum active power limit and the rate of change of active power.
Compared with the prior art, the frequency control method considering the kinetic energy throughput capacity of the double-fed fan has the following technical effects:
(1) the control method of the invention realizes the active controllable fan frequency control by adding frequency control in the fan rotor side control and storing kinetic energy into the fan or releasing the kinetic energy into the power grid when the frequency deviation is positive and negative respectively.
(2) The control method of the invention considers the potential of the fan for storing kinetic energy when the frequency deviation is positive, the self-defined frequency control parameter is in direct proportion to the potential of the fan for storing kinetic energy, namely, when the rotating speed of the rotor of the fan is low (with the potential of high stored kinetic energy), the capacity of the fan for storing kinetic energy is fully exerted, and redundant active power in the system is absorbed; at high rotational speeds (with the potential of weakly storing kinetic energy), the wind turbine stores appropriate kinetic energy, thereby avoiding excessive startup pitch angle control and mechanical fatigue problems. When the frequency deviation is negative, the potential of the fan for releasing the effective kinetic energy is considered, the self-defined frequency control parameter and the potential for releasing the effective kinetic energy are in a direct proportion relation, namely, the effective kinetic energy of the fan is fully released to compensate the active power shortage of the system at high rotating speed (with high potential for releasing the kinetic energy); when the rotating speed is low (the potential of weak release of kinetic energy is provided), the fan releases a proper amount of rotational kinetic energy to make up the active power loss of the system, so that the rotating speed instability problem and the serious secondary frequency drop problem of the fan are avoided.
(3) Compared with a constant frequency control parameter method, the frequency control method provided by the invention can effectively improve the frequency stability, improve the grid-connected capability of the fan, provide guarantee for high wind power grid connection, provide response time for the synchronous generator to participate in frequency modulation, and further reduce the capacity of an energy storage device for active standby and frequency modulation of the system.
Drawings
Fig. 1 is a flow chart of a frequency control method proposed by the present invention;
fig. 2 is a schematic diagram of the frequency control parameter curve of the present invention when K is 100;
FIG. 3 is a schematic diagram of a simulation system according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a double-fed wind power generator according to an embodiment of the present invention;
FIG. 5(a) is a graph of instantaneous system frequency deviation as affected by load input in accordance with an embodiment of the present invention;
FIG. 5(b) is a graph illustrating an active power output of a fan affected by a load input according to an embodiment of the present invention;
FIG. 5(c) is a graph of fan rotor speed as affected by load input according to an embodiment of the present invention;
FIG. 5(d) is a graph of the number of control parameters affected by load input for an embodiment of the present invention;
FIG. 6(a) is a graph of instantaneous system frequency deviation affected by load shedding for an embodiment of the present invention;
FIG. 6(b) is a graph illustrating an active output of a wind turbine affected by load shedding according to an embodiment of the present invention;
FIG. 6(c) is a graph of fan rotor speed affected by load shedding for an embodiment of the present invention;
FIG. 6(d) is a graph of the number of control parameters affected by load shedding for an embodiment of the present invention.
Detailed Description
The present invention will be further explained with reference to the drawings so that those skilled in the art can more deeply understand the present invention and can carry out the present invention, but the present invention will be explained below by referring to examples, which are not intended to limit the present invention.
As shown in fig. 1, a frequency control method for considering the throughput capacity of the kinetic energy of the doubly-fed wind turbine includes the following steps: s1: calculating the instantaneous frequency of a system power grid according to the voltage of a public coupling point of the wind power plant and the power grid, and starting the system frequency control of the fan when the instantaneous frequency of the power grid exceeds a set dead zone range; if the current is within the set dead zone range, continuously working in the maximum power tracking control; s2: calculating a system frequency deviation delta f according to the instantaneous frequency of the power grid, and judging the positive and negative of the system frequency deviation delta f; s3: respectively calculating frequency control parameters AG adopted when the frequency deviation delta f of the system is positive according to the rotor rotating speed of the collected fanOF(ωr) Frequency control parameter AG used when sum system frequency deviation Δ f is negativeUF(ωr)；
In the formula (1), AGOF(ωr) The frequency control parameter used for the timing of the frequency deviation Δ f, and K is a frequency control factor, which is used to adjust the frequency control effect, ωrIs the rotational speed of the fan rotor, omegamaxIs the maximum rotor speed; the bracket part in the formula represents the potential of the wind turbine for storing energy;
in the formula (2), AGUF(ωr) Is a frequency control parameter used when the frequency deviation deltaf is negative, and K is a frequency control factor used to adjust the frequency control effect, omegarIs the rotational speed of the fan rotor, omegaminIs the minimum rotor speed; the bracketed section in the formula represents the potential of the wind turbine to release energy;
s4: judging to adopt a frequency control parameter AG according to the positive and negative of the calculated system frequency deviation delta fOF(ωr) Or frequency control parameter AGUF(ωr) Obtaining the active variable quantity of the system frequency control, adding the active increment to the maximum power tracking control to calculate the active power output value P of the fanrefThe specific formula is as follows:
in formula (3), PMPPTTracking output power for maximum power, AGOF(ωr) Frequency control parameter, AG, for use when frequency deviation Δ f is positiveUF(ωr) For the frequency control parameter, ω, used when the frequency deviation Δ f is negativerThe rotational speed of the fan rotor.
The specific steps of step S3 are as follows: s3.1: rotor rotating speed omega of collecting fanrMastering the maximum rotor speed omega of the fanmaxAnd minimum rotor speed ωmin(ii) a S3.2: analyzing the potential of stored energy and released energy of the fan according to the operating characteristics of the fan; s3.3: when calculated system frequency offsetWhen the difference delta f is larger than zero, the potential of the fan for storing energy is considered, and the adopted frequency control parameter AGOF(ωr) The energy storage potential of the wind turbine is in direct proportion, and the expression is as follows:
in the formula (1), AGOF(ωr) The frequency control parameter used for the timing of the frequency deviation Δ f, and K is a frequency control factor, which is used to adjust the frequency control effect, ωrIs the rotational speed of the fan rotor, omegamaxIs the maximum rotor speed; the parenthesis part in the formula represents the capacity of the fan for storing energy;
when the calculated system frequency deviation delta f is less than zero, the potential of the fan for releasing energy is considered, and the adopted frequency control parameter, AGUF(ωr) The energy releasing potential of the fan is in direct proportion, and the expression is as follows:
in the formula (2), AGUF(ωr) Is a frequency control parameter used when the frequency deviation deltaf is negative, and K is a frequency control factor used to adjust the frequency control effect, omegarIs the rotational speed of the fan rotor, omegaminAt minimum rotor speed, the bracketed section indicates the ability of the fan to release energy.
In step S2, after the system frequency deviation Δ f is calculated, the system frequency deviation Δ f needs to be filtered, and whether to start the frequency control of the fan is determined according to the processed system frequency deviation Δ f.
In step S4, an active power output value P of the wind turbine is calculatedrefIn order to prevent overloading of the fan and to reduce mechanical fatigue, the calculated active power output value PrefIt is limited by the maximum active power limit and the rate of change of active power.
As shown in fig. 2, the parameter curve proposed by the present invention is illustrated when K is 100; the system frequency control parameter is changed along with the running state of the fan, namely the rotating speed of the fan, when the frequency deviation is positive, the adopted frequency control parameter is in a direct proportional relation with the potential of the fan for storing kinetic energy, and the aim is to store proper rotational kinetic energy according to different running working conditions of the fan; the redundant active power of the system is reduced, the starting times and time of the pitch angle are reduced, and the frequency stability is improved; when the frequency deviation is negative, the adopted frequency control parameter is in a positive proportional relation with the potential of the fan for releasing effective kinetic energy, the purpose is to release proper rotary kinetic energy according to different fan operation conditions, compensate the active power loss of a system, avoid the occurrence of fan stall phenomenon, reduce the maximum frequency deviation and realize controllable frequency control of the wind generating set.
According to the invention, a frequency control (frequency deviation) control loop is added in the rotor side converter controller, so that the fan can effectively store and release kinetic energy according to the frequency deviation to provide frequency support capability, thereby improving the grid-connected capability of the fan, improving the frequency stability, providing response time for a synchronous generator to participate in system frequency modulation, and reducing the capacity of an active standby energy storage device and an energy storage device for frequency modulation of the system; as shown in fig. 3, a mathematical example system model containing high-proportion wind power integration is built by means of an EMTP-RV simulation platform, and a frequency control technology provided by a fan is compared with an existing control method for analysis.
The application effect of the invention is described in detail in combination with the simulation result;
in order to verify the effectiveness of the system frequency control method considering the throughput capacity of the kinetic energy of the fan, an example system containing large-scale wind power integration is built on the basis of an EMTP-RV simulation platform, and the structure of a double-fed wind driven generator is shown in FIG. 4; the following three control cases were analyzed and compared in the load input and removal scenarios.
(1) The double-fed fan works in a maximum power tracking running state;
(2) the double-fed fan adopts the existing frequency control method;
(3) the double-fed fan adopts the frequency control method provided by the invention;
under the influence of load removal and input, the power system has redundant and insufficient active power, and the frequency of the system deviates; fig. 5 and 6 show the variation of the frequency deviation of the power system, the active power output of the wind turbine generator system, the rotating speed of the fan rotor and the control coefficient when the load is input and cut off under the three conditions respectively.
Under the influence of load input, as can be seen from fig. 5(a) to 5(d), when the fan operates in the maximum power operation mode, the maximum frequency deviation is-0.638 Hz, when the fan adopts the conventional constant parameter frequency control method, the maximum frequency deviation is-0.499 Hz, and when the fan adopts the controllable frequency control method provided by the present invention, the maximum frequency deviation is-0.380 Hz, which is mainly caused by that the control parameters of the frequency control method provided by the present invention are greater than the conventional control parameters, the active power output of the frequency control method provided by the present invention increases to 97.4MW, while the active power output of the conventional method increases to 83.0 MW. Therefore, the active power released by the wind turbine into the grid is greater than in the existing control methods.
As can be seen from fig. 6(a) to 6(d), when the fan operates in the maximum power operation mode, the maximum frequency deviation is 0.660Hz, when the fan adopts the conventional constant parameter frequency control method, the maximum frequency deviation is 0.502Hz, and when the fan adopts the controllable frequency control method provided by the present invention, the maximum frequency deviation is 0.396Hz, which is mainly caused by that the control parameter of the frequency control method provided by the present invention is greater than the conventional control parameter, the active power output of the frequency control method provided by the present invention is reduced to 36.0MW, and the active power output of the conventional method is reduced to 50.2 MW. Thus, the active power stored in the wind turbine is greater than in existing control methods.
Compared with the existing frequency control method, the frequency control method provided by the invention can effectively utilize the rotating part of the fan to release and store kinetic energy when the frequency deviation is positive and negative, reduce the maximum frequency deviation and improve the frequency stability.
When the frequency of the power grid deviates and exceeds the dead zone threshold value, a frequency control module of the wind turbine generator is started to simultaneously judge the positive and negative frequency deviation; when the calculated system frequency deviation is positive, the frequency control is realized by storing redundant active power into the fan, and the method is mainly characterized in that the adopted frequency control parameter is in direct proportion to the capacity of the fan for storing kinetic energy, so that more kinetic energy is stored at low rotating speed (high capacity for storing kinetic energy), and a proper amount of kinetic energy is stored at high rotating speed (low capacity for storing kinetic energy), so that the starting times and time of the pitch angle controller are reduced; when the frequency deviation is negative, the fan realizes frequency control by releasing kinetic energy into the power grid, and the method is mainly characterized in that the used control parameters are in direct proportional relation with the effective kinetic energy of the fan, and more energy is released from the fan at high rotating speed (high energy release capacity) to compensate active power shortage; and proper rotational kinetic energy is released at low rotating speed (low energy release capacity), so that the problem of instability of the rotating speed of the fan is avoided. By the method, the problem of frequency stability caused by high wind power integration can be effectively solved; from the perspective of the fan, the grid-connected performance of the fan is improved, and the stable operation of the fan is ensured; from the aspect of an electric power system, response time is provided for the synchronous generator to participate in frequency modulation, the frequency stability of the system is improved, and the capacity of an energy storage device for active standby and frequency modulation of the system is further reduced.
When the frequency deviation is positive and negative, different user-defined frequency control parameters are adopted to provide the system frequency supporting capability; the proposed frequency control parameters can fully utilize the capacity of the fan for storing and releasing rotational energy to carry out frequency control; when the frequency deviation is negative, the proposed control parameters can prevent the fan from stalling; when the frequency deviation is positive, the proposed control parameters can avoid excessive starting pitch angle control and reduce the mechanical fatigue problem.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention, and are not intended to limit the scope of the present invention, and any person skilled in the art should understand that equivalent changes and modifications made without departing from the concept and principle of the present invention should fall within the protection scope of the present invention.
Claims (4)
1. A frequency control method for considering the kinetic energy throughput capacity of a doubly-fed wind turbine is characterized by comprising the following steps:
s1: calculating the instantaneous frequency of a system power grid according to the voltage of a public coupling point of the wind power plant and the power grid, and starting the system frequency control of the fan when the instantaneous frequency of the power grid exceeds a set dead zone range; if the current is within the set dead zone range, continuously working in the maximum power tracking control;
s2: calculating a system frequency deviation delta f according to the instantaneous frequency of the power grid, and judging the positive and negative of the system frequency deviation delta f;
s3: respectively calculating frequency control parameters AG adopted when the frequency deviation delta f of the system is positive according to the rotor rotating speed of the collected fanOF(ωr) Frequency control parameter AG used when sum system frequency deviation Δ f is negativeUF(ωr)；
In the formula (1), AGOF(ωr) The frequency control parameter used for the timing of the frequency deviation Δ f, and K is a frequency control factor, which is used to adjust the frequency control effect, ωrIs the rotational speed of the fan rotor, omegamaxIs the maximum rotor speed;
in the formula (2), AGUF(ωr) Is a frequency control parameter used when the frequency deviation deltaf is negative, and K is a frequency control factor used to adjust the frequency control effect, omegarIs the rotational speed of the fan rotor, omegaminIs the minimum rotor speed;
s4: judging to adopt a frequency control parameter AG according to the positive and negative of the calculated system frequency deviation delta fOF(ωr) Or frequency control parameter AGUF(ωr) Obtaining the active variable quantity of the system frequency control,adding active increment to maximum power tracking control to calculate active power output value P of fanrefThe specific formula is as follows:
in formula (3), PMPPTControlling output power, AG, for maximum power trackingOF(ωr) Frequency control parameter, AG, for use when frequency deviation Δ f is positiveUF(ωr) For the frequency control parameter, ω, used when the frequency deviation Δ f is negativerThe rotational speed of the fan rotor.
2. The frequency control method considering the kinetic energy throughput capacity of the doubly-fed wind turbine as claimed in claim 1, wherein the specific steps of the step S3 are as follows:
s3.1: rotor rotating speed omega of collecting fanrMastering the maximum rotor speed omega of the fanmaxAnd minimum rotor speed ωmin；
S3.2: analyzing the potential of stored energy and released energy of the fan according to the operating characteristics of the fan;
s3.3: when the calculated system frequency deviation delta f is larger than zero, the potential of the fan for storing energy is considered, and the adopted frequency control parameter AGOF(ωr) The energy is in direct proportion to the stored energy of the fan, and the expression is as follows:
in the formula (1), AGOF(ωr) The frequency control parameter used for the timing of the frequency deviation Δ f, and K is a frequency control factor, which is used to adjust the frequency control effect, ωrIs the rotational speed of the fan rotor, omegamaxIs the maximum rotor speed;
when the calculated system frequency deviation delta f is less than zero, the potential of the fan for releasing energy is considered, and the adopted frequency control parameter AGUF(ωr) With the windThe engine release energy is in a proportional relation, and the expression is as follows:
in the formula (2), AGUF(ωr) Is a frequency control parameter used when the frequency deviation deltaf is negative, and K is a frequency control factor used to adjust the frequency control effect, omegarIs the rotational speed of the fan rotor, omegaminIs the minimum rotor speed.
3. The frequency control method considering the kinetic energy throughput capacity of the doubly-fed wind turbine as claimed in claim 1, wherein in the step S2, after the system frequency deviation Δ f is calculated, the system frequency deviation Δ f needs to be filtered, and whether to start the frequency control of the wind turbine is determined according to the processed system frequency deviation Δ f.
4. The frequency control method considering the kinetic energy throughput capacity of the doubly-fed wind turbine as claimed in claim 1, wherein in the step S4, an active power output value P of the wind turbine is calculatedrefIn order to prevent overloading of the fan and to reduce mechanical fatigue, the calculated active power output value PrefIt is limited by the maximum active power limit and the rate of change of active power.
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