A Delta-Channel Modular Multilevel Converter for Zero/Low-Fundamental-Frequency Operation

This paper proposes a delta-channel modular multilevel converter (MMC). It aims to overcome the issues of the conventional MMC during zero/low fundamental frequency operation. The proposed converter is characterized by the cross connection of both the upper and the lower three arms through two sets of delta-channel branches. These delta-channel branches timely redistribute power among three phase legs, leading to the minimized submodule capacitor voltage fluctuations, even at zero/low fundamental frequency operation. The inner power balancing through physical channels makes the converter inject no common-mode voltage. A 4160-V, 1-MW simulation model is performed in MATLAB/SIMULINK, and a 208-V, 5-kW experimental setup is constructed in the laboratory. Both the simulation and experimental results verify the feasibility of the proposal.