Collaborative Control and Allocation Method of RSC and GSC for DFIG System to Suppress High-Frequency Resonance and Harmonics

Abstract

When doubly fed induction generator (DFIG) system connects to the parallel compensation grid with harmonics, high-frequency resonances (HFR) occur due to the insufficient phase margin, meanwhile the output power quality of the DFIG system is degraded due to the grid harmonics. For solving the two problems simultaneously, the collaborative control strategy which allots different targets to rotor side converter (RSC) and grid side converter (GSC) is proposed in this article, in which the HFR damping controller is planted at RSC or GSC, while the other converter will be responsible for improving the power quality of the DFIG system. The core of the collaborative control strategy is how to select RSC or GSC to achieve HFR damping, which is investigated by analyzing the impedance characteristic of the DFIG system after planting the HFR damping controller. With the collaborative control strategy, the excellent performance of HFR damping and harmonics suppression can be guaranteed for the DFIG system under grid harmonics, meanwhile the DFIG system can operate flexibly with different targets, i.e., sinusoidal output current, smooth output power. Finally, theoretical analysis and experimental results for different DFIG systems verify the correctness and availability of the proposed collaborative control strategy.