Improved Operation of DFIG System under Harmonically Distorted Grid Considering Interharmonics

Abstract

This paper proposed an improved control strategy for the operation of doubly fed induction generator (DFIG) system under harmonically distorted grid with the consideration of inter-harmonics. Based on the traditional inner current control loop, an incomplete differential element with a high-pass filter for different alternative control targets, i.e., sinusoidal stator current, sinusoidal rotor current, smooth active and reactive power, or smooth torque, is employed as an additional loop in DFIG system to enhance the operation capability of DFIG system on the generalized harmonic grid. The proposed controller based on incomplete differential controllers is employed both at rotor side converter (RSC) and grid side converter (GSC) independently. With the proposed control strategy, RSC has the capability of achieving different alternative targets under harmonically distorted grid, while GSC is responsible for suppressing harmonic current of GSC which caused by grid harmonics. The theoretical analyses for the performance and stability of DFIG system with the proposed controller are given to illustrate the effectiveness and practicality of the proposed control strategy. Finally, the simulation results validate the theoretical analyses of the proposed control strategy.