CN112260314A - Phase-locked synchronous stable control method and system during fault ride-through period of wind turbine generator - Google Patents

Phase-locked synchronous stable control method and system during fault ride-through period of wind turbine generator Download PDF

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CN112260314A
CN112260314A CN202011103169.1A CN202011103169A CN112260314A CN 112260314 A CN112260314 A CN 112260314A CN 202011103169 A CN202011103169 A CN 202011103169A CN 112260314 A CN112260314 A CN 112260314A
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fault
active current
wind turbine
turbine generator
phase
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CN112260314B (en
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丁磊
王志浩
朱国防
高雪松
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Shandong University
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Shandong University
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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
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Abstract

The invention provides a phase-locked synchronous stability control method and system during fault ride-through of a wind turbine generator, belonging to the technical field of wind turbines.A Thevenin equivalent impedance of a power grid after a fault is assumed to be the same as an equivalent impedance before the fault, and an equivalent electromotive force amplitude is reduced compared with that before the fault, and a generator-end voltage change curve when the equivalent electromotive force is different is obtained according to the relation between a generator-end voltage amplitude and active current; and carrying out amplitude limiting control on the active current according to the generator-end voltage change curve, so that the active current amplitude limiting control curve and the generator-end voltage change curve always have an intersection point in a stable region, thereby ensuring the phase-locked synchronization stability of the wind turbine generator. The complexity of the control strategy is low, the robustness of the control is improved, the phase-locked synchronization stability of the wind turbine generator in the fault ride-through process is ensured, and the wind turbine generator can output active power as much as possible.

Description

Phase-locked synchronous stable control method and system during fault ride-through period of wind turbine generator
Technical Field
The invention relates to the technical field of wind turbine generators, in particular to a phase-locked synchronous stable control method and system during fault ride-through of a wind turbine generator.
Background
With the continuous development of wind power generation, the permeability of the wind turbine generator is continuously increased, the wind turbine generator becomes a main power source of a power system gradually, and the requirement on the transient active supporting capability of the wind turbine generator is higher and higher. Currently, the requirements for active support of wind turbines during grid faults are concentrated on support for reactive current, while there are no explicit requirements for support of active current during the duration of the fault. Therefore, control strategies adopted by different manufacturers are different, and the current active current control strategy has the modes of no output, output according to the residual capacity of the converter, output according to the active power before the fault and the like. The problem of phase-locked synchronous stability is not considered in the formulation of the existing active current control strategy, and in some scenes, if the active current instruction value set by the wind turbine generator is too large, the active current instruction value may cause the loss of the synchronous stability between the wind turbine generator and a power grid, and the safety and stability of the system are seriously influenced. Therefore, the constraint of the synchronization stability of the power grid needs to be considered, the control strategy of the wind turbine generator is improved, and the problem of the synchronization stability is avoided.
In summary, the active current control during the current wind turbine generator fault duration can be roughly divided into three modes of outputting according to the residual capacity of the converter, comprehensively considering the residual capacity of the converter and the active power before the fault, and outputting and not outputting. The phase-locked synchronous instability may be caused by outputting according to the residual capacity of the converter and comprehensively considering the residual capacity of the converter and the active power before the fault.
Disclosure of Invention
The invention aims to provide a control method and a control system for controlling active current during fault ride-through of a wind turbine generator, simplifying control complexity, improving control robustness and ensuring phase-locked synchronization stability in the fault ride-through process of the wind turbine generator so as to solve at least one technical problem in the background art.
In order to achieve the purpose, the invention adopts the following technical scheme:
on one hand, the invention provides a phase-locked synchronous stable control method during fault ride-through of a wind turbine generator, which comprises the following steps:
determining the relation between terminal voltage amplitude and active current at the moment of fault;
assuming that Thevenin equivalent impedance of the power grid after the fault is the same as the equivalent impedance before the fault, and the equivalent electromotive force amplitude is reduced compared with that before the fault, and obtaining a terminal voltage change curve when the equivalent electromotive force is different by combining the relation between the terminal voltage amplitude and the active current;
and carrying out amplitude limiting control on the active current according to the terminal voltage change curve, so that the active current amplitude limiting control curve and the terminal voltage change curve always have an intersection point in a stable region.
Preferably, the determining the relationship between the terminal voltage amplitude and the active current at the time of the fault includes:
Figure RE-GDA0002777807910000021
wherein, the value of U is the voltage amplitude per unit of the PCC point of the wind turbine generator, and I isQRepresenting a reactive current, IPRepresenting active current, XeqRepresenting Thevenin equivalent reactance, EeqRepresenting thevenin equivalent electromotive force;
and in the low-voltage ride through process, the reactive current is as follows:
IQkx (0.9-U |); wherein k represents a reactive current support coefficient;
then:
Figure RE-GDA0002777807910000022
wherein, IPmax＝|Eeq|/Xeq。
Preferably, when the active current reaches the transmission limit,
Figure RE-GDA0002777807910000023
at this time, the process of the present invention,
Figure RE-GDA0002777807910000024
along with the change of the output active current, the circuit end voltage change curve is ventilated with UminAs a boundary, divided into a stable region and an unstable region。
Preferably, the limiting control of the active current according to the terminal voltage variation curve includes:
Figure RE-GDA0002777807910000031
wherein the content of the first and second substances,
Figure RE-GDA0002777807910000032
Imaxrepresenting the maximum allowable current, k, of the converterpThe slope of an active current amplitude limiting control curve is shown, SCR shows the short-circuit ratio of a wind turbine generator access system, P0And representing the active power output by the wind turbine generator before the fault.
Preferably, the slope k of the active current limiting control curvepThe determination of (1) comprises:
determining a power angle swung between a terminal voltage and Thevenin equivalent electromotive force according to an active current transmission formula, and determining a power angle corresponding to a balance point on a slope corresponding to phase-locked synchronous stable constraint; determining the slope k by setting the maximum allowed swing anglep。
Preferably, the power angle swung open between the terminal voltage and thevenin equivalent electromotive force is:
Figure RE-GDA0002777807910000033
then, the power angle corresponding to the balance point on the oblique line corresponding to the phase-locked synchronization stability constraint is:
Figure RE-GDA0002777807910000034
in a second aspect, the present invention provides a phase-locked synchronous stable control system during wind turbine generator fault ride-through, including: the controller is used for carrying out amplitude limiting control on the active current, so that an intersection point is always formed between an active current amplitude limiting control curve and an engine-end voltage change curve in a stable region;
the controller is configured to: assuming that Thevenin equivalent impedance of the power grid after the fault is the same as the equivalent impedance before the fault, and the equivalent electromotive force amplitude is reduced compared with that before the fault, and obtaining a terminal voltage change curve when the equivalent electromotive force is different by combining the relation between the terminal voltage amplitude and the active current; and carrying out amplitude limiting control on the active current according to the terminal voltage change curve.
In a third aspect, the invention provides a non-transitory computer readable storage medium comprising instructions for performing the method as described above.
In a fourth aspect, the invention provides an electronic device comprising a non-transitory computer readable storage medium as described above; and one or more processors capable of executing the instructions of the non-transitory computer-readable storage medium.
In a fifth aspect, the present invention provides an electronic device comprising means for performing the method as described above.
The invention has the beneficial effects that: the complexity of the control strategy is low, the robustness of control is improved, the phase-locked synchronization stability of the wind turbine generator in the fault ride-through process is ensured, and the wind turbine generator can output active power as much as possible.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic diagram of an active current control mode during a fault duration of an existing wind turbine generator.
Fig. 2 is a structure diagram of the equivalent circuit of thevenin according to the embodiment of the present invention.
Fig. 3 is a schematic diagram of a variation curve of a machine terminal voltage amplitude with an active current according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of terminal voltage variation curves of different equivalent electromotive forces according to an embodiment of the present invention.
Fig. 5 is a schematic diagram illustrating a phase-locked synchronization stability analysis according to an embodiment of the invention.
Fig. 6 is a schematic diagram of an active current clipping control curve for maintaining phase-locked synchronization stability according to an embodiment of the present invention.
Fig. 7 is a diagram of a simulated power grid topology according to an embodiment of the present invention.
Fig. 8 is a schematic diagram of a voltage amplitude simulation result after active current amplitude limiting control is implemented according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by way of the drawings are illustrative only and are not to be construed as limiting the invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including 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 will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
For the purpose of facilitating an understanding of the present invention, the present invention will be further explained by way of specific embodiments with reference to the accompanying drawings, which are not intended to limit the present invention.
It should be understood by those skilled in the art that the drawings are merely schematic representations of embodiments and that the elements shown in the drawings are not necessarily required to practice the invention.
Examples
The active current control during the fault duration of the wind turbine generator can be roughly divided into the following three conditions. As shown in fig. 1, a line indicates a curve for performing active current control according to the output of the remaining capacity of the converter, a curve for performing active current control by comprehensively considering the remaining capacity of the converter and the active power before the fault, and a line indicates an active current control mode without output. Wherein the first and second modes may cause phase lock synchronization instability.
At present, the active support of the wind generating set during the fault duration is prioritized by reactive current, and most reactive current control can be represented as IQK x (0.9-U | where U | is the voltage amplitude per unit value of the PCC point of the wind turbine generator, and k is the reactive current support coefficient. The output of the active current should take into account the capacity limitation of the converter of the wind turbine to avoid the converter overcurrent. Assuming that the maximum allowable current of the converter is ImaxThen the output active currentShould satisfy
Figure RE-GDA0002777807910000061
The larger the reactive current is, the more the capacity occupied by the reactive current is, and the smaller the capacity of the residual active current is. In addition to converter capacity constraints, there are also active power constraints. The active power output by the fan during the duration of the fault should not be greater than the active power before the fault. Namely, it is
Figure RE-GDA0002777807910000062
Wherein P is0The active power before the wind turbine generator fails.
The control curve originally adopted by the wind turbine generator is assumed to be the curve (r) in fig. 1. The new active current control method for the wind turbine generator during fault ride-through provided by the embodiment can ensure the phase-locked synchronization stability of the wind turbine generator during the fault ride-through process and enable the wind turbine generator to output active power as much as possible.
The grid in the event of a fault can be represented using the thevenin equivalent circuit shown in fig. 2. Neglecting the resistance, the relationship between the voltage amplitude of the fan terminal and the output active current and reactive current is as follows:
Figure RE-GDA0002777807910000071
wherein, the value of U is the voltage amplitude per unit of the PCC point of the wind turbine generator, and I isQRepresenting a reactive current, IPRepresenting active current, XeqRepresenting Thevenin equivalent reactance, EeqRepresenting the equivalent electromotive force of thevenin.
Suppose that during the low voltage ride through, the reactive current is according to IQK × (0.9- | U |) output, then:
Figure RE-GDA0002777807910000072
wherein, IPmax＝|Eeq|/Xeq。
When the active current reaches the transmission limit, there is
Figure RE-GDA0002777807910000073
At this time, the process of the present invention,
Figure RE-GDA0002777807910000074
the terminal voltage variation curve can be represented by the curve shown in fig. 3 as the output active current varies. Excited by | UminThe region is divided into a stable region and an unstable region.
Assuming that the Thevenin equivalent impedance of the grid after the fault is the same as the equivalent impedance before the fault, the equivalent electromotive force amplitude is reduced compared to before the fault. Then, when the equivalent electromotive forces are different, the terminal voltage variation curves of different equivalent electromotive forces are obtained as shown in fig. 4.
Combining fig. 4 with the curve (r) in fig. 1, the curve shown in fig. 5 is obtained. In the curve, the solid line (r) represents the active current amplitude control curve of the wind turbine generator, and the arc solid line (V) represents the system voltage variation curve with the active current (V-I)PCurve) is shown. If the solid line (r) and the arc solid line (r) have intersection points in the stable region, it indicates that the phase-locked synchronization is stable, otherwise, the phase-locked synchronization is unstable. As shown in fig. 5, when | E | is decreased to a certain degree, the two curves no longer have an intersection in the stable region, i.e., phase-locked synchronization instability occurs. In order to avoid phase-locked synchronous instability, the wind turbine generator needs additional control measures in the fault ride-through process.
The proposed active current control curve is:
Figure RE-GDA0002777807910000081
wherein the content of the first and second substances,
Figure RE-GDA0002777807910000082
Imaxrepresenting the maximum allowable current, k, of the converterpThe slope of an active current amplitude limiting control curve is shown, SCR shows the short-circuit ratio of a wind turbine generator access system, P0And representing the active power output by the wind turbine generator before the fault.
The final curve is shown in fig. 6, and the proposed active control curve is divided into two sections: the first stage is that terminal voltage goes from 0 to | U-minThe active current is controlled to be zero in the stage (1); the second stage is that the terminal voltage is shunted from | UminIn the stage of 0.9, the active current output in the stage is limited by the phase-locked synchronous stability, and is also limited by the capacity of the converter and the active power before the fault.
Based on the active current amplitude limiting-voltage amplitude control curve shown in fig. 6, the active current is amplitude limited on the curve, so that the phase-locked synchronization stability can be ensured. The proposed control curve is shown as a solid line in fig. 6, and it can be seen that there is always an intersection point with the stable region of the arc solid line,. sup..
In the control mode, the inverse of the short-circuit ratio of the power grid connected with the wind power before the fault is used as thevenin equivalent reactance of the power grid after the system is in fault, and the control mode has certain conservatism.
In the active current control curve, if the slope k of the control curvepIf the active power output by the wind turbine generator is too large, the active power output by the wind turbine generator is relatively large, but the stability margin is small at the moment; if the slope k of the control curvepIf the output power is too small, the stability is guaranteed, but the output active power is greatly limited. Therefore, the slope of the control curve should be chosen appropriately.
According to the active current transmission formula, the phase angle laid out between the terminal voltage and thevenin equivalent electromotive force is
Figure RE-GDA0002777807910000083
Then the power angle corresponding to the balance point on the oblique line corresponding to the lock synchronization stable constraint is
Figure RE-GDA0002777807910000091
Thus by setting the maximum allowed swing angle, k can be setp. If the set power angle is not more than 45 DEG, k isp＝k+SCR。
In order to verify the effectiveness of the proposed control strategy, a simulation model is built in the DIgSILENT PowerFactory for simulation verification. The topology of the power grid is shown in fig. 7, a wind turbine generator is represented by a converter, the voltage of 0.69kV at the outlet of the wind turbine generator is boosted to 110kV through two transformers, and then the wind turbine generator is connected with an external power grid through a longer power transmission line. And when the voltage of the external power grid drops, the synchronous stability between the wind turbine generator and the external power grid is verified in a simulation mode. In the simulation, the dc bus voltage is assumed to be constant.
When the voltage amplitude | E | of the external power grid drops to 0.3p.u., the wind turbine generator set is made to respectively adopt the conventional active current control strategy and the active current control strategy proposed by the embodiment, and the simulation result is shown in fig. 8. It can be seen from the simulation result that when the conventional control strategy is adopted, the rotation speed of the PLL is always in a state greater than 1, as shown by a solid line (c) in fig. 8, which means that the angle difference between the angle of the PLL and the external power grid is greater and greater, resulting in instability of phase-locked synchronization, and causing oscillation of terminal voltage, as shown by a solid line (b) in fig. 8. After the control strategy provided by this embodiment is adopted, since the output of the active current is limited within the synchronous stability constraint range, phase-locked synchronous instability between the wind turbine generator and the external power grid does not occur, and the PLL rotation speed and the terminal voltage can be kept stable, as shown by a solid line ninu in fig. 8, the PLL rotation speed is shown by a solid line r, and as shown by a solid line r in fig. 8, the terminal voltage is shown by a solid line r.
In summary, according to the phase-locked synchronous stability control method for the wind turbine generator during fault ride-through, provided by the embodiment of the invention, when the voltage drop is deep, the active current instruction value of the wind turbine generator is reduced, and synchronous stability between the wind turbine generator and an external power grid can be realized at the fault continuous stage. Finally, simulation verification is carried out in the DIgSILENT Power factory, and a simulation result shows that the proposed active current control strategy can effectively avoid phase-locked synchronization instability.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Although the present disclosure has been described with reference to the specific embodiments shown in the drawings, it is not intended to limit the scope of the present disclosure, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive faculty based on the technical solutions disclosed in the present disclosure.

Claims (10)

1. A phase-locked synchronous stable control method during fault ride-through of a wind turbine generator is characterized by comprising the following steps:
determining the relation between terminal voltage amplitude and active current at the moment of fault;
assuming that Thevenin equivalent impedance of the power grid after the fault is the same as the equivalent impedance before the fault, and the equivalent electromotive force amplitude is reduced compared with that before the fault, and obtaining a terminal voltage change curve when the equivalent electromotive force is different by combining the relation between the terminal voltage amplitude and the active current;
and carrying out amplitude limiting control on the active current according to the terminal voltage change curve, so that the active current amplitude limiting control curve and the terminal voltage change curve always have an intersection point in a stable region.
2. The method of claim 1, wherein determining the relationship between terminal voltage amplitude and active current during fault ride-through comprises:
Figure FDA0002726086330000011
wherein, | U | representsVoltage amplitude per unit value, I, of PCC point of wind turbine generatorQRepresenting a reactive current, IPRepresenting active current, XeqRepresenting Thevenin equivalent reactance, EeqRepresenting thevenin equivalent electromotive force;
and in the low-voltage ride through process, the reactive current is as follows:
IQkx (0.9-U |); wherein k represents a reactive current support coefficient;
then:
Figure FDA0002726086330000012
wherein, IPmax＝|Eeq|/Xeq。
3. The phase-locked synchronous stable control method during the fault ride-through period of the wind turbine generator set according to claim 2, characterized in that:
when the active current reaches the transmission limit,
Figure FDA0002726086330000013
at this time, the process of the present invention,
Figure FDA0002726086330000014
along with the change of the output active current, the circuit end voltage change curve is ventilated with UminThe region is divided into a stable region and an unstable region.
4. The phase-locked synchronous stable control method of the wind turbine generator during the fault ride-through period according to claim 3, wherein the amplitude limiting control of the active current according to the generator-end voltage variation curve comprises:
Figure FDA0002726086330000021
wherein the content of the first and second substances,
Figure FDA0002726086330000022
Imaxrepresenting the maximum allowable current, k, of the converterpThe slope of an active current amplitude limiting control curve is shown, SCR shows the short-circuit ratio of a wind turbine generator access system, P0And representing the active power output by the wind turbine generator before the fault.
5. The phase-locked synchronous stability control method during wind turbine generator fault ride-through according to claim 4, wherein the slope k of the active current limiting control curvepThe determination of (1) comprises:
determining a power angle swung between a terminal voltage and Thevenin equivalent electromotive force according to an active current transmission formula, and determining a power angle corresponding to a balance point on a slope corresponding to phase-locked synchronous stable constraint; determining the slope k by setting the maximum allowed swing anglep。
6. The phase-locked synchronous stable control method during the fault ride-through period of the wind turbine generator set according to claim 5, wherein the power angle swung open between the generator terminal voltage and thevenin equivalent electromotive force is as follows:
Figure FDA0002726086330000023
then, the power angle corresponding to the balance point on the oblique line corresponding to the phase-locked synchronization stability constraint is:
Figure FDA0002726086330000024
7. a phase-locked synchronous stable control system during fault ride-through of a wind turbine generator is characterized by comprising: the controller is used for carrying out amplitude limiting control on the active current, so that an intersection point is always formed between an active current amplitude limiting control curve and an engine-end voltage change curve in a stable region;
the controller is configured to: assuming that Thevenin equivalent impedance of the power grid after the fault is the same as the equivalent impedance before the fault, and the equivalent electromotive force amplitude is reduced compared with that before the fault, and obtaining a terminal voltage change curve when the equivalent electromotive force is different by combining the relation between the terminal voltage amplitude and the active current; and carrying out amplitude limiting control on the active current according to the terminal voltage change curve.
8. A non-transitory computer-readable storage medium characterized in that: the non-transitory computer readable storage medium comprising instructions for performing the method of any of claims 1-6.
9. An electronic device, characterized in that: comprising the non-transitory computer-readable storage medium of claim 8; and one or more processors capable of executing the instructions of the non-transitory computer-readable storage medium.
10. An electronic device, characterized in that: the apparatus comprising means for performing the method of any one of claims 1-6.
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