Simulation Research of MMC Based Multi-terminal AC/DC Converter

Modular Multilevel Converter (MMC) is a highly modular and highly centralized power electronic converter topology with an AC port and multiple DC sub-module ports. Through appropriate modification, it can be applied to largescale cluster of DC source and loads (such as electric vehicles, AC and DC microgrids, decommissioned energy storage batteries, etc.) into the network. Direct connection between electric vehicle, AC and DC microgrids, or other DC source/load and MMC will affect the safe operation of MMC, increase control difficulty. For this reason, the Isolated Bidirectional DC/DC (IBDC) is introduced as the isolation link between the sub-module of MMC and the DC source/load to form a MMC-based multi-port AC/DC converter (MMC-IBDC). Basing on analyzing working mechanism, a three-layer control strategy is proposed and corresponding controllers are designed aiming at large-scale cluster of DC source and loads. Considering differences among application scenarios, two cases are simulated in which the results under PSCAD/EMTDC verify the rationality of MMC-IBDC topology and effectiveness of the control strategy.