A Novel MMC Based on Series-Parallel Multiplex and Its Control Strategy for Flexible HVDC Application

Due to flexible power regulation performance of voltage-source converter based high-voltage direct current (VSC-HVDC) system, kinds of control strategy have been proposed to realize its capabilities of voltage control and reactive power support. However, the maximum current of IGBT devices limits these capabilities. This paper proposes a novel modular multilevel converter (MMC) topology, called series-parallel multiplex MMC (SPM-MMC), which can withstand higher current and reduce harmonics. The proposed topology connects the half-bridge sub-module (HB-SM) in parallel through coupled reactor to enhance its maximum current. Corresponding control strategy has been designed, including current control, power control and reactive power support. Comparison between SPM-MMC and traditional HB-MMC has been done in MATLAB/Simulink. Simulation results verify the enhanced performance of SPM-MMC during steady state and faults.