CN111628684A - Optimized de-excitation control method and system for fault ride-through of doubly-fed wind turbine - Google Patents

Optimized de-excitation control method and system for fault ride-through of doubly-fed wind turbine Download PDF

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CN111628684A
CN111628684A CN202010435455.1A CN202010435455A CN111628684A CN 111628684 A CN111628684 A CN 111628684A CN 202010435455 A CN202010435455 A CN 202010435455A CN 111628684 A CN111628684 A CN 111628684A
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transient
rotor
stator
flux linkage
amplitude
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CN111628684B (en
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丁磊
朱国防
高雪松
徐建建
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Shandong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
    • H02P9/12—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for demagnetising; for reducing effects of remanence; for preventing pole reversal
    • H02P9/123—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for demagnetising; for reducing effects of remanence; for preventing pole reversal for demagnetising; for reducing effects of remanence
    • 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
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/22—Current control, e.g. using a current control loop
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2101/00—Special adaptation of control arrangements for generators
    • H02P2101/15—Special adaptation of control arrangements for generators for wind-driven turbines

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  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)
  • Control Of Ac Motors In General (AREA)

Abstract

The invention discloses an optimized de-excitation control method and system for doubly-fed wind turbine fault ride-through, which are used for establishing a DFIG simplified transient component mathematical model; enabling the rotor transient current and the stator transient flux linkage obtained by de-excitation control to be in opposite phase based on the model, wherein the amplitudes of the rotor transient current and the stator transient flux linkage accord with a preset proportional relation; the amplitude and the phase of the rotor transient current are controlled, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, transient power which is rushed into the direct current bus through the RSC in the transient process is reduced, and overvoltage of the direct current bus is restrained. In conclusion, the optimized de-excitation control can accurately control the amplitude and the phase of the transient current of the rotor, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, the optimized de-excitation control also effectively reduces the transient power which is rushed into the direct current bus through the RSC in the transient process, and effectively inhibits the overvoltage of the direct current bus.

Description

Optimized de-excitation control method and system for fault ride-through of doubly-fed wind turbine
Technical Field
The invention belongs to the technical field of control, and particularly relates to an optimized de-excitation control method and system for fault ride-through of a doubly-fed fan.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the rapid development of the wind power generation industry, the installed capacity of the wind driven generator is increased day by day, and the influence on the operation of a power grid is increased more and more, so that the safe operation of a fan is concerned more and more. Among the numerous fan types, doubly-fed wind turbines (DFIGs) are widely used due to their small size and low cost.
The stator side of the DFIG is directly connected to a power grid, and the DFIG is greatly influenced by grid fault disturbance. When the grid fails, the DFIG generates stator transient flux linkages and induces transient electromotive forces in the rotor windings, which can cause over-currents in the rotor circuit and over-voltages on the dc bus, threatening the safe operation of the DFIG.
During fault ride-through, in order to ensure safe operation of the doubly-fed wind turbine, a number of software and hardware strategies are proposed: one of the hardware strategies is to connect a crowbar circuit into the rotor winding, and the crowbar circuit is put into the rotor winding after the current of the rotor winding exceeds a specified value, so that the rotor winding can be effectively protected; at present, a more widely applied hardware strategy is to lock an IGBT (insulated gate bipolar translator) of a Rotor Side Converter (RSC) after a rotor overcurrent, perform uncontrolled rectification through a diode to avoid the IGBT from being damaged by the overcurrent, simultaneously, flow transient power into a direct current bus through the uncontrolled rectification of the diode to cause the rise of the voltage of the direct current bus, and consume redundant energy in a direct current bus capacitor through a direct current chopper (DCchopper) circuit to inhibit the rise of the voltage of the direct current bus. The investment of these hardware protection strategies can make the DFIG uncontrollable and the additional hardware circuitry can increase the cost, but they are indispensable protection means in the face of a severe grid fault.
When light power grid faults or a hardware protection strategy exits from follow-up problems, the field suppression control is a relatively popular software control strategy, the control strategy tries to control the transient current amplitude of the rotor and the transient flux linkage amplitude of the stator to be in a certain proportional relation, and meanwhile, the transient current of the rotor and the transient flux linkage of the stator are reversed to accelerate the attenuation of a transient process. However, the practical effect of the conventional de-excitation control is not ideal, the amplitude and the phase of the transient current of the rotor cannot be effectively controlled, and the expected target cannot be achieved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an optimized de-excitation control method for fault ride-through of a doubly-fed wind turbine, the optimized de-excitation control can accurately control the amplitude and the phase of transient current of a rotor, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, the optimized de-excitation control also effectively reduces the transient power which is rushed into the direct current bus through the RSC in the transient process, and effectively inhibits the overvoltage of the direct current bus.
In order to achieve the above object, one or more embodiments of the present invention provide the following technical solutions:
the optimized de-excitation control method for doubly-fed fan fault ride-through comprises the following steps:
establishing a DFIG simplified transient component mathematical model;
based on the model, the rotor transient current and the stator transient flux linkage obtained by the de-excitation control are reversed, and the amplitudes of the rotor transient current and the stator transient flux linkage accord with a preset proportional relation;
the amplitude and the phase of the transient current of the rotor are controlled, the fastest transient process attenuation speed is considered while the overcurrent of the rotor is limited, meanwhile, the transient power which is rushed into a direct current bus through RSC in the transient process is reduced, and the overvoltage of the direct current bus is restrained.
According to the further technical scheme, when the DFIG simplified transient component mathematical model is built:
establishing a three-order complex state space equation model for the DFIG, and decomposing the model into a state equation (GPT) describing a power frequency component adjustment process and a state equation (ZTS) describing a transient attenuation component caused by voltage disturbance after the voltage of a power grid is disturbed;
only the Main Transient Component (MTC) is considered, the third order equation of state is reduced to the first order equation of state and the main transient component is solved.
According to the further technical scheme, in the DFIG simplified transient component model, a differential equation of the stator transient flux linkage is obtained based on the attenuation change rule of the stator transient flux linkage, the rotor transient current amplitude and the stator transient flux linkage amplitude are controlled to be in a certain proportional relation based on the differential equation, and meanwhile the rotor transient current and the stator transient flux linkage are made to be in opposite phase to accelerate the attenuation of the transient process.
The further technical scheme is that the proportional coefficient of the demagnetization control is converted from real number to complex number Kmag_real+jKmag_imagThe multiple relation between the rotor transient current and the stator transient flux linkage is a negative real number, and the absolute value of the negative real number is equal to the expected demagnetization control gain.
In a further technical scheme, a real part and an imaginary part of the field suppression control coefficient should satisfy the following two formulas:
Figure BDA0002502089160000031
and obtaining a real part and an imaginary part of the demagnetization control coefficient according to the formula.
The optimized de-excitation control system for doubly-fed wind turbine fault ride-through comprises a controller, wherein the controller is configured to:
establishing a DFIG simplified transient component mathematical model;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model and enabling the amplitude of the rotor transient current to be in accordance with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the rotor transient current are controlled, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, transient power which is rushed into the direct current bus through the RSC in the transient process is reduced, and overvoltage of the direct current bus is restrained.
The above one or more technical solutions have the following beneficial effects:
the method is based on a simplified transient component model of the DFIG, improves the traditional demagnetization control, and provides an optimized demagnetization control strategy. The optimized de-excitation control can accurately control the amplitude and the phase of the transient current of the rotor, limits the over-current of the rotor and considers the fastest attenuation speed of the transient process, and simultaneously, the optimized de-excitation control also effectively reduces the transient power of the DC bus which is rushed into the DC bus through RSC in the transient process, and effectively inhibits the overvoltage of the DC bus.
The invention establishes a DFIG simplified transient component mathematical model based on the attenuation characteristic of the stator transient flux linkage, improves the traditional demagnetization control, and provides an optimized demagnetization control strategy, wherein the optimized demagnetization control strategy can accurately control the amplitude and the phase of the transient current of a rotor, and the fastest transient process attenuation speed is considered while the overcurrent of the rotor is limited. Meanwhile, the optimized de-excitation control also effectively reduces the transient power which is rushed into the direct current bus through the RSC in the transient process, and effectively inhibits the overvoltage of the direct current bus. A grid-connected DFIG model adopting an optimized field suppression control technology is built in PowerFactory software, and the effectiveness of an optimized field suppression control strategy is verified through a simulation result.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a block diagram of a conventional de-excitation control;
FIG. 2 is a block diagram of an improved demagnetization control according to an embodiment of the invention;
FIG. 3 is a comparison of current amplitudes of the field suppression control rotor according to the embodiment of the present invention;
FIG. 4 is a graph of transient current and transient flux linkage amplitude of a rotor in a conventional de-excitation control;
FIG. 5 is a graph of transient current and transient flux linkage amplitude of a rotor for improved demagnetization control in accordance with an embodiment of the present invention;
FIG. 6 is a diagram of dq axis rotor transient current and stator transient magnetic flux linkage under conventional de-excitation control;
FIG. 7 is a diagram of dq axis rotor transient current and stator transient flux linkage under improved demagnetization control;
fig. 8 is a comparison graph of the de-excitation control dc bus voltage.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
Example one
As described in the background section: during fault ride-through of a doubly-fed wind generator (DFIG), transient currents are generated in a stator and a rotor under the influence of grid voltage disturbance, and Rotor Side Converter (RSC) overcurrent and overvoltage of a direct-current bus are easily caused. The field suppression control is a method for controlling the transient current of the rotor, and tries to control the transient current amplitude of the rotor to be in a certain proportional relation with the transient flux linkage amplitude of the stator. Meanwhile, the transient current of the rotor and the transient flux linkage of the stator are reversed to accelerate the attenuation of the transient process. However, the traditional de-excitation control is not ideal in effect, and cannot effectively control the amplitude and phase of the transient current of the rotor, so that the expected target cannot be achieved.
Therefore, the embodiment discloses an optimized de-excitation control method for doubly-fed wind turbine fault ride-through, which establishes a DFIG simplified transient component mathematical model, improves the traditional de-excitation control, and provides an optimized de-excitation control strategy, wherein the optimized de-excitation control can accurately control the amplitude and the phase of the transient current of a rotor, the fastest attenuation speed of the transient process is considered while the overcurrent of the rotor is limited, meanwhile, the optimized de-excitation control also effectively reduces the transient power of a DC bus which is inrush through RSC in the transient process, and effectively inhibits the overvoltage of the DC bus.
Firstly, a DFIG simplified transient component mathematical model is introduced, a three-order complex state space equation model is established for the DFIG, and the DFIG is decomposed into a state equation (GPT) describing a power frequency component adjusting process and a state equation (ZTS) describing a transient attenuation component caused by voltage disturbance after the grid voltage disturbance. The transient process in GPT is very short in duration, while the transient process in ZTS is long in duration and large in amplitude, and is a main component of the transient process after the fault. The solutions of the state variables of ZTS have three frequency attenuation components, one frequency component has a slower attenuation and a larger initial value than the other two frequency components, and the grid frequency with the frequency close to negative can approximately represent the complete solution, which is named as the Main Transient Component (MTC). In order to simplify the calculation, only the MTC component is considered, so that the three-order state equation ZTS is reduced, a method for solving RSC natural transient voltage and current of the simplified natural transient state equation only considering the MTC component is provided, the three-order state equation is reduced into a first-order state equation, and the MTC component is solved, wherein the main formula is as follows:
Figure BDA0002502089160000061
wherein:
Figure BDA0002502089160000062
wherein the subscript represents a per unit value,
Figure BDA0002502089160000063
in order to obtain the rotor transient current,
Figure BDA0002502089160000064
in order to provide a transient flux linkage of the stator,
Figure BDA0002502089160000065
outputs a transient voltage for RSC. L iss*、Lr*、Lm*、Rs*、Rr*Are all DFIG parameters, ωr*As the rotor speed, ω1*For the grid frequency, it can be taken as a constant 100 pi, i.e. equal to ωB。KmodThe equivalent proportionality coefficient of the RSC output voltage formed by the current loop output signal through modulation is a constant. Kp，KiIs the proportional gain and the integral gain of the current loop PI regulator.
Attenuation characteristics of stator transient flux linkage: in the DFIG simplified transient component model, the decay change law of the stator transient flux linkage can be represented by the following formula:
Figure BDA0002502089160000071
in the above formula, the first and second carbon atoms are,
Figure BDA0002502089160000072
the transient state current of the stator winding is obtained according to a stator flux linkage equation as follows:
Figure BDA0002502089160000074
the differential equation for the stator transient flux linkage can be found as follows:
Figure BDA0002502089160000073
as can be seen from equation (5), at a certain time, under the same transient rotor current amplitude, if the phase of the transient rotor current is opposite to that of the transient stator flux linkage, the phase relationship will make the transient stator flux linkage decay faster than all other phase relationships at that time. In view of this, the field suppression control attempts to control the amplitude of the rotor transient current and the amplitude of the stator transient flux linkage in a proportional relationship and to invert the phase of the rotor transient current and the phase of the stator transient flux linkage to accelerate the transient process decay.
Conventional de-excitation control analysis, as shown in fig. 1, conventional de-excitation control of DFIG intends to control the rotor transient current to exhibit a specific ratio to the stator transient flux and to make the two phases opposite to each other to accelerate the decay of the transient process by inputting a rotor transient current signal opposite to the stator transient flux to the current control command.
However, the current command is an alternating current quantity close to the frequency of the power grid in a dq coordinate system, the rotor current control adopting the PI regulator cannot accurately make the realized rotor transient current equal to the command value, the realized rotor transient current and the stator flux linkage opposite in phase, and the amplitude of the rotor transient current is not equal to the expected amplitude, so that the expected demagnetization control effect cannot be achieved, the rotor transient current cannot be effectively controlled, and the demagnetization control effect cannot be expected.
The deduced simplified transient component model is popularized to the DFIG under the traditional de-excitation control, and the approximate relation between the rotor transient current and the stator transient flux linkage under the traditional de-excitation control can be obtained as follows:
Figure BDA0002502089160000081
wherein, KmagIs the proportionality coefficient of the field suppression control. According to the formula (6), under the control of the conventional de-excitation
Figure BDA0002502089160000082
And
Figure BDA0002502089160000083
cannot be completely inverted, and
Figure BDA0002502089160000084
is also not equal to
Figure BDA0002502089160000085
The amplitude of (c).
Optimizing a field suppression control strategy: if it is to be KmagConversion from real to complex Kmag_real+jKmag_imagSo that the coefficients on the right side of equation (6) are overall a negative real number, and the absolute value of the negative real number is equal to the desired demagnetization control gain: (Gmag) I.e. it is desirable that the rotor transient current is proportional to the stator transient flux linkage, the rotor transient current and the stator transient flux linkage obtained by the demagnetization control are in anti-phase and have an amplitude that corresponds to a predetermined proportional relationship with the stator transient flux linkage. To achieve this, the real part and the imaginary part of the demagnetization control coefficient should satisfy the following two equations:
Figure BDA0002502089160000086
obtaining by solution:
Figure BDA0002502089160000087
according to the above derivation, the flow chart of optimizing the demagnetization control strategy can be shown in fig. 2, and the specific flow can be expressed as follows:
(1) determining a demagnetization gain G for optimizing the demagnetization control when the rotor-side converter capacity permitsmag。
(2) And (4) calculating the real part and the imaginary part of the demagnetization control proportionality coefficient according to the formula (8), and calculating the transient current instruction value at the moment.
(3) And (3) superposing the instruction value in the step (2) and the positive sequence current instruction value to obtain a total current instruction value, and inputting the total current instruction value into the PI controller to realize optimized demagnetization control.
Simulation verification: in order to test the performance of the optimized field suppression control strategy for doubly-fed fan fault ride-through, a 2MW grid-connected operation doubly-fed fan single machine model is set up in DIgSILENT/Power Factory software, and part of parameters are shown in Table 1.
TABLE 1 DFIG part parameters
Figure BDA0002502089160000091
Determining the demagnetization gain GmagAt 3, it is desirable to control the rotor transient current amplitude to be three times the stator transient flux linkage amplitude and in anti-phase with the stator transient flux linkage. K is obtained by improving the basis of demagnetization controlmag_real+jKmag_imagThe complex coefficient of the rotor generates a de-excitation control transient rotor current instruction, and the traditional de-excitation control directly uses-3
Figure BDA0002502089160000092
As a de-excitation control transient rotor current command. Under the disturbance of 0.3p.u voltage step drop, the rotor current amplitude under the conditions of no field suppression control, traditional field suppression control and improved field suppression control is shown in figure 3.
The amplitudes of the rotor transient current and the stator transient flux linkage under the traditional de-excitation control and the improved de-excitation control are shown in fig. 4 and 5.
As can be seen from the above two graphs, the transient current amplitude of the rotor under the conventional de-excitation control already exceeds 3 times the transient flux linkage amplitude of the stator, and the predetermined transient current amplitude target of the rotor is not achieved, which is also the cause of the transient overcurrent of the rotor. And the rotor transient current amplitude under the improved de-excitation control accurately meets the target of 3 times of stator transient flux linkage amplitude.
In addition, the comparison between the conventional demagnetization control and the improved demagnetization control in controlling the transient current phase of the rotor is shown in fig. 6 and 7.
Therefore, the traditional de-excitation control does not realize the phase reversal of the transient current of the rotor and the transient flux linkage of the stator, and the fastest attenuation under the current amplitude of the current rotor cannot be achieved; and the improved de-excitation control corrects the phase of the transient current of the rotor and the transient flux linkage of the stator into the opposite phase, and achieves the purpose of fastest attenuation under the accurate control of the transient current amplitude.
In addition, transient active power entering the direct current bus through the rotor side converter in the whole transient process is reduced by improving the de-excitation control, and the voltage rise of the direct current bus is restrained.
According to the DFIG simplified transient component model, the traditional demagnetization control is improved, and optimized demagnetization control is provided. The optimized de-excitation control can accurately control the amplitude and the phase of the transient rotor current, so that the rotor transient current amplitude and the stator transient flux linkage amplitude are in a specific proportional relation, the rotor transient current phase and the stator transient flux linkage are accurately reversed, the transient current amplitude is controlled, overcurrent is avoided, and the attenuation speed of the transient process is accelerated. In addition, the problem of direct-current overvoltage in the fault transient process can be effectively reduced by optimizing the de-excitation control. In conclusion, optimizing the field suppression control can significantly improve the fault-ride-through operation of the DFIG.
Example two
The present embodiment aims to provide a computing device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement the following steps, including:
establishing a DFIG simplified transient component mathematical model;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model, and enabling the amplitude of the rotor transient current to accord with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the transient current of the rotor are controlled, the fastest transient process attenuation speed is considered while the overcurrent of the rotor is limited, meanwhile, the transient power which is rushed into a direct current bus through RSC in the transient process is reduced, and the overvoltage of the direct current bus is restrained.
EXAMPLE III
An object of the present embodiment is to provide a computer-readable storage medium.
A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, performs the steps of:
establishing a DFIG simplified transient component mathematical model;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model, and enabling the amplitude of the rotor transient current to accord with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the rotor transient current are controlled, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, transient power which is rushed into the direct current bus through the RSC in the transient process is reduced, and overvoltage of the direct current bus is restrained.
The steps involved in the apparatuses of the second and third embodiments correspond to those of the first embodiment of the method, and the detailed description thereof can be found in the relevant description of the first embodiment. The term "computer-readable storage medium" should be taken to include a single medium or multiple media containing one or more sets of instructions; it should also be understood to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor and that cause the processor to perform any of the methods of the present invention.
Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using general purpose computer means, or alternatively, they can be implemented using program code that is executable by computing means, such that they are stored in memory means for execution by the computing means, or they are separately fabricated into individual integrated circuit modules, or multiple modules or steps of them are fabricated into a single integrated circuit module. The present invention is not limited to any specific combination of hardware and software.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims (10)

1. The optimized de-excitation control method for doubly-fed fan fault ride-through is characterized by comprising the following steps:
establishing a DFIG simplified transient component mathematical model of the doubly-fed wind turbine;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model, and enabling the amplitude of the rotor transient current to accord with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the transient current of the rotor are controlled, the fastest transient process attenuation speed is considered while the rotor overcurrent is limited, meanwhile, the transient power which is rushed into a direct current bus through a rotor side converter RSC in the transient process is reduced, and the direct current bus overvoltage is restrained.
2. The method for controlling the optimized de-excitation of the fault ride-through of the doubly-fed wind turbine as claimed in claim 1, wherein when a DFIG simplified transient component mathematical model of the doubly-fed wind turbine is established:
a three-order complex state space equation model is established for the DFIG, and the model is decomposed into a state equation GPT describing a power frequency component adjusting process and a state equation ZTS describing a transient attenuation component caused by voltage disturbance after the voltage of a power grid is disturbed.
3. The method for controlling the optimal de-excitation of the fault ride-through of the doubly-fed wind turbine as claimed in claim 2, wherein attenuation components of three frequencies exist in the solution of the state variable of ZTS, one frequency component is slower in attenuation and larger in initial value than the other two frequency components, and the grid frequency with the frequency close to negative can approximately represent a complete solution, and is named as a main transient component MTC.
4. The method for controlling the optimal de-excitation of the doubly-fed wind turbine fault ride-through of claim 3, wherein only MTC components are considered, a three-order state equation is reduced to a one-order state equation, and the MTC components are solved.
5. The method for controlling the optimal de-excitation of the fault ride-through of the doubly-fed wind turbine as claimed in claim 1, wherein in the DFIG simplified transient component model, a differential equation of the stator transient flux linkage is obtained based on an attenuation change rule of the stator transient flux linkage. Based on a differential equation, the transient current amplitude of the rotor and the transient flux linkage amplitude of the stator are controlled to be in a certain proportional relation, and meanwhile, the transient current of the rotor and the transient flux linkage of the stator are reversed to accelerate the attenuation of a transient process.
6. The method for optimized de-excitation control of doubly-fed wind turbine fault ride-through of claim 1, wherein the proportionality coefficient of de-excitation control is converted from real number to complex number Kmag_real+jKmag_imagAnd the rotor transient current and the stator transient flux linkage are in a negative real number relation, and the absolute value of the negative real number is equal to the expected demagnetization control gain.
7. The method for controlling the optimal de-excitation of the fault ride-through of the doubly-fed wind turbine as claimed in claim 6, wherein the real part and the imaginary part of the de-excitation control coefficient should satisfy the following two equations:
Figure FDA0002502089150000021
and obtaining the real part and the imaginary part of the demagnetization control coefficient according to the formula.
8. The optimized de-excitation control system for doubly-fed wind turbine fault ride-through comprises a controller, and is characterized in that the controller is configured to:
establishing a DFIG simplified transient component mathematical model;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model, and enabling the amplitude of the rotor transient current to accord with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the rotor transient current are controlled, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, transient power which is rushed into the direct current bus through the RSC in the transient process is reduced, and overvoltage of the direct current bus is restrained.
9. A computing device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to perform steps comprising:
establishing a DFIG simplified transient component mathematical model;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model, and enabling the amplitude of the rotor transient current to accord with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the rotor transient current are controlled, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, transient power which is rushed into the direct current bus through the RSC in the transient process is reduced, and overvoltage of the direct current bus is restrained.
10. A computer-readable storage medium, having a computer program stored thereon, the program, when executed by a processor, performing the steps of:
establishing a DFIG simplified transient component mathematical model;
enabling the rotor transient current obtained by de-excitation control to be opposite to the stator transient flux linkage based on the model, and enabling the amplitude of the rotor transient current to accord with a preset proportional relation with the stator transient flux linkage;
the amplitude and the phase of the rotor transient current are controlled, and the fastest transient process attenuation speed is considered while the rotor overcurrent is limited. Meanwhile, transient power which is rushed into the direct current bus through the RSC in the transient process is reduced, and overvoltage of the direct current bus is restrained.
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