Loss Minimization in Modular Multilevel Converter with Bypass Switch for HVDC Application

Modular Multi-level Converter (MMC) is one of the most attractive choices in the field of High Voltage Direct Current (HVDC) transmission over Line Commutated Converter (LCC) technology. However, MMC-HVDC has lesser efficiency than LCC-HVDC. This paper proposes a new bypass switch (BPS) arrangement inside the MMC arm to improve the efficiency of the converter. The BPS provides an alternate path for OFF-state submodules in the arm of the converter thereby reducing the conduction losses. An analytical expression of loss reduction term is presented which estimates the loss reduction that can be achieved with different configurations of switches in BPS-MMC. The operation and performance of BPS-MMC is analyzed and verified by simulation in MATLAB/Simulink, showing a good agreement between theoretical analysis and simulation results.