Development of Submodule Test Equipment for MMC-Based VSC-HVDC System

A novel test equipment that can test submodules of modular multilevel converter (MMC) applied to high voltage direct current (HVDC) transmission system with voltage-sourced converter (VSC) in very similar to actual operation is dealt with. The proposed test equipment can implement the second order harmonics, the DC offset of the submodule current and the switching pattern of the submodule employing a simple circuit structure and control without additional power except compensation for losses. The simulation and experimental results of the implemented full-scaled equipment for submodule, which has power ratings of 3 kV and 1000 A, show the validity of the proposed test equipment.