Dynamic characteristic analysis of distributed generation system based on modular multilevel converters

According to the working principle and topological structure of modular multilevel converter (MMC) and condering the operational feature of distributed generation (DG) system, an equivalent inversion-type of DG system based on MMC and the mathematical model of its AC current controller are built. The dynamic characteristic of inversion-type of DG system is analyzed by PSCAD and it is found that under DC voltage fluctuation over wide range the AC current of inversion-type of DG system based on MMC and its output power fluctuate over wide range as well. To solve this problem, an improved AC current controller is proposed and whose effectiveness are verified by simulation results.