Multi‐hierarchy control strategy in abc coordinate for modular multilevel matrix converter in fractional frequency transmission system

Abstract

This paper proposes a multi-hierarchy control strategy in abc coordinate for modular multilevel matrix converter (M3C) in fractional frequency transmission system (FFTS). The proposed control strategy avoids complicated coordinate transformations when the traditional control strategies based on coordinate transformation are adopted. Four hierarchies are designed to balance the capacitor voltages. In different hierarchies, the capacitor voltage ripples have different frequencies. According to this characteristic, different bandwidths of filters are adopted in different hierarchies, resulting in different control speeds among the four hierarchies. This will not only speed up the control but also assure the control accuracy. Simulation results verify the feasibility and effectiveness of the proposed strategy.