Parallel Impedance-Reshaping Control Strategy for Suppressing Wide Range High-Frequency Resonance of Shunt Compensated DFIG System

Abstract

The shunt compensated grid (SCG) connecting with doubly-fed induction generator (DFIG) system easily suffers from high-frequency resonance (HFR). Existing studies reshape the DFIG based on a pre-calculated frequency to suppress the HFR. When facing voltage disturbance, shunt capacitors are added to the grid which greatly changes the resonance frequency, probably resulting functional failure of HFR suppression. In this paper, a parallel impedance-reshaping control (PIRC) strategy for the rotor side converter (RSC) and grid-side converter (GSC) control is proposed to suppress the HFR of the DFIG-SCG system when the shunt capacitor varies in a wide range. A high-order coefficient is combined with the original impedance of the RSC-induction generator (RSC-IG) side, and a damping controller is designed to reshape the impedance of the DFIG system. Based on the parallel structure of the equivalent impedance of the GSC side and the RSC-IG side, the impact of the shunt capacitor to the controller can be eliminated, thus providing effective HFR suppression in a wide frequency range. Case studies demonstrate the advantage of the PIRC in HFR suppression and harmonic suppression.