Time/frequency domain modelling for grid-connected MMC sub-synchronous/super-synchronous oscillation in PV MVDC power collection and integration system

摘要

This study proposes a comprehensive PWM-based modular multilevel converter (MMC) model in both time and frequency domain at the same time. The time-domain model not only accelerates simulation speed but also describe the characteristics of sub-modules, such as the dynamic voltage-balancing process of sub-module capacitors. The frequency-domain model provides the output impedance of the grid-connected MMC inverter in positive-sequence and negative-sequence coordinates. The proposed model, validated by results of different scenarios listed, at last, predicts and eliminates sub-synchronous/super-synchronous oscillations with impedance shaping method.