Research on optimized suppression strategy for high frequency resonance of MMC-HVDC system

Abstract

In recent years, many high-frequency resonance (HFR) accidents have occurred in high-voltage direct current transmission (HVDC) system based on modular multilevel converter (MMC), which seriously threaten the stable operation of the power system. This paper studies the optimized suppression strategy for HFR of MMC-HVDC System. Firstly, the AC-side smallsignal impedance of MMC is modelled by the harmonic linearization method, which has taken into the consideration of current control loop, power control loop and phase-locked loop (PLL), and then the effect of each control loop on the impedance characteristics of MMC is analysed. Then, aiming at the shortcomings of existing high frequency resonance suppression strategies, an optimized suppression strategy based on voltage feedforward optimization and power control loop optimization is proposed, which reduces the resonance risk in lower frequency bands compare to the existing suppression strategies. Finally, the effectiveness of the optimized suppression strategy is verified by time-domain simulation.