Second-order slip form-based method for controlling doubly-fed wind generator (DFIG)

Abstract

The invention discloses a second-order slip form-based method for controlling a doubly-fed wind generator (DFIG). According to the method, due to the adoption of direct torque control, the electromagnetic torque and reactive power of the DFIG can be controlled directly; and the complex steps of extracting positive and negative sequences and harmonic components and calculating a rotor current reference value are eliminated, so that the introduction of decomposition delay is avoided. Due to the adoption of second-order slip form control, the negative sequence and any low-order harmonic components can be regulated and controlled, and negative influence caused by network voltage imbalance and low-order harmonics in the reactive power and the electromagnetic torque can be controlled directly; and the are eliminated to fulfill the aim of stable torque and the output of the reactive power. Compared with the conventional control method, the second-order slip form-based method has the advantages that the occupied software space is reduced, and the dynamic regulation capacity is high, so that resources are saved, and the control effect on the DFIG is enhanced.

Description

technical field [0001] The invention belongs to the technical field of wind power generation control, and in particular relates to a DFIG control method based on a second-order sliding mode. Background technique [0002] Doubly-fed asynchronous wind turbine is the main type of modern large-scale wind turbine due to its own constant-speed variable-frequency operation capability, small required converter capacity and four-quadrant operation capability. However, the stator current of the DFIG (doubly-fed wind generator) unit operating under the condition of unbalanced grid voltage and harmonic distortion will be unbalanced and distorted, and the output active and reactive power and electromagnetic torque will have multiple frequency pulsations . The deterioration of the above performance indicators will cause great harm to the stable and reliable operation of large-scale wind power grid-connected power generation, and even threaten the reliable and stable operation of the grid...

AI Technical Summary

Problems solved by technology

[0004] It can be seen from the above analysis process that the stator voltage and rotor current positive sequence, negative sequence, 5th and 7th harmonic component extraction in the implementation process of the DFIG traditional control method under the weak grid voltage takes up a lot of computing time and software. space code, and introduce a large control delay, which will easily cause unstable operation of the system and reduce the rapidity of system response

In addition, the existing control methods can only control the specified harmonics. When the power grid contains other harmonic distortions (such as 11th and 13th harmonic distortions), the control system will lose the ability to eliminate harmonic effects

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