Design and Simulation of Unified Power Flow Controller Based on Modular Multilevel Converter

To apply unified power flow controllers(UPFC) in power transmission systems it is necessary to solve such problems as the selection,design,modulation and control of high-capacity main circuits operated in high voltage environment.Typical high-capacity multi-level converters that could be utilized for UPFC are compared and commented on.On this basis,to validate the feasibility of applying modular topological structure in UPFC,the parameter design method,structure of control system,modulation strategy and starting modes for UPFC based on modular multi-level converter(MMC) are designed and simulated by PSCAD/EMTDC,and problems to be solved are pointed out.