Research on Start and Stop Control Strategies for the CSC-MMC DC Transformer

Direct current transformer (DCT) is the core equipment to realize low-voltage DC collection and high-voltage DC transmission of new energy. The hybrid isolated DC transformer topology (CSC-MMC) with AC coupling between controlled current source converter and modular multilevel converter can realize high power density design and high efficiency power transfer. This paper first analyzes the topology and steady-state control method based on CSC-MMC. Then, based on the equivalent circuit analysis of csc-mmc, the start-up control strategy and stop control strategy for high-voltage side are proposed to realize the smooth transition between energy and electrical quantities. Finally, the effectiveness of the control strategy is verified in PSCAD/EMTDC.