Application of Current-transferring Submodule in Modular Multilevel Converter

In order to solve the problem that the traditional half-bridge module cannot clear the DC fault, a current-transferring submodule based on the parallel thyristor and the reverse-blocking IGBT is proposed. The topology and operating principle of the current-transferring submodule are introduced in detail, and its steady state control strategy is the same as the half-bridge submodule. Then, according to its current limiting principle, the DC fault control protection strategy of MMC based on the current-transferring submodule is proposed. At last, the simulation model is built in PSCAD/EMTDC, and the effectiveness of the proposed submodule topology and the control and protection strategy in DC fault clearing has been verified by the simulation results.