Fuzzy Adaptive PI Circulating Current Suppressing Control for MMC-HVDC

Recent years, modular multilevel converter (MMC) is one of the most promising topologies applied to high voltage direct current transmission (HVDC). In order to solve the circulating currents caused by structural defects of MMC, a fuzzy adaptive PI circulating current suppressing controller is proposed based on mathematical model of MMC and functioning fuzzy subset inference method: The fuzzy number is calculated according to the error of system state, error variation, membership function and fuzzy control rules; The center of gravity method is used for defuzzification, and finally the PI parameters are modified. Finally, the PSCAD/EMTDC simulation model with fuzzy adaptive PI controller is established. The results show that the fuzzy adaptive PI circulating current suppressing controller is effective for MMC-HVDC.