Impedance Modeling and Stability Analysis of AC/AC Modular Multilevel Converter for Railway System

The ac/ac modular multilevel converter (MMC) application in the electric railway poses new challenges to stability of system. impedance analysis method is an effective way assess MMC-based systems. Due internal dynamics MMC, there are steady-state harmonic components arm currents and capacitor voltages, these have a significant impact on dynamic characteristics MMCs. To accurately predict systems, this article proposes model MMC with consideration dominant harmonics. Simulation experimental results obtained from prototype presented demonstrate accuracy proposed model. Besides, compared ignoring harmonics, show advantage description example system analyzed using model, validated by simulations. effect control parameters further analyzed, provides guidance for controller design damp instability