Damping Method of High Frequency Resonance for Stator Current Controlled DFIG System under Parallel Compensation Grid

High-frequency resonances (HFR) is a subsistent issue in a doubly fed induction generator (DFIG) system when it connects to a parallel compensation grid, due to the insufficient phase margin between the impedance of DFIG and grid. The occurrence mechanism and damping methods for the HFR in the rotor current controlled DFIG have been investigated in the existing literatures, while the appearance and solutions of HFR for the stator current controlled DFIG (SCC-DFIG) have not been studied yet. Based on the impedance of SCC-DFIG, this article analyzes the occurrence mechanism of the HFR in the SCC-DFIG. Thereby, an impedance reshaping method based on stator voltage feedforward controller (SVFC) is proposed. By employing the proposed SVFC, SCC-DFIG can avoid HFR in a wide frequency range, which signifies that HFR with varied resonance frequency caused by the change of compensation degree can be damped well. More importantly, compared to the existing solutions for HFR damping, the impedance reshaping effect of the proposed SVFC for SCC-DFIG is irrelevant to the parameters of DFIG, so that the HFR damping controller can be valid for different DFIG systems without redesigning controller parameters. Theoretical analysis and experiments are given to illustrate the effectiveness and practicability of the proposed method.