Coordinated suppression strategies for passive and active resonances of the MMC‐HVDC AC‐side system on the medium‐ and high‐frequency bands

Abstract

Abstract The medium‐ and high‐frequency resonance between modular multilevel converters (MMCs) and the AC grid has attracted increasing attention due to the frequent occurrence of resonance events in recent years. Therefore, resonance issues are analyzed, and corresponding suppression strategies are proposed in this paper. First, the analytical expression of the MMC AC‐side impedance is established. Then, the mechanism and influencing factors of different types of resonances, including active resonance and passive resonance, are analyzed to provide a more comprehensive perspective. To aid the suppression of these resonances, resonance risk indexes are defined to evaluate the resonance risk, and then the suppression effects of different strategies are compared through analytical calculations. Subsequently, coordinated resonance suppression strategies suitable for different resonance situations are proposed. The key points of the suppression strategies are to suppress the negative damping of MMC impedance at the resonance frequency and improve the integrated impedance of the MMC AC‐side system. Finally, the proposed suppression strategies are verified by simulation results.

Keywords

• coordinated suppression strategy
• impedance
• medium‐ and high‐frequency resonance
• modular multilevel converter
• resonance analysis