阅读说明：本技术 双馈风机故障穿越的优化灭磁控制方法及系统 (Optimized de-excitation control method and system for fault ride-through of doubly-fed wind turbine ) 是由 丁磊 朱国防 高雪松 徐建建 于 2020-05-21 设计创作，主要内容包括：本发明公开了双馈风机故障穿越的优化灭磁控制方法及系统,建立DFIG简化暂态分量数学模型；基于上述模型使灭磁控制所得到的转子暂态电流与定子暂态磁链反相,并且两者幅值符合预定比例关系；控制转子暂态电流的幅值和相位,在限制转子过电流的同时兼顾最快的暂态过程衰减速度。同时,降低暂态过程中通过RSC涌入直流母线的暂态功率,抑制直流母线过电压。综上所述,优化灭磁控制能够准确地控制转子暂态电流的幅值和相位,在限制转子过电流的同时兼顾最快的暂态过程衰减速度。同时,优化灭磁控制也有效地降低了暂态过程中通过RSC涌入直流母线的暂态功率,有效抑制了直流母线过电压。(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.)

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 K_{mag_real}+jK_{mag_imag}And 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:

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.

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 K_{mag_real}+jK_{mag_imag}The 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:

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.