Comparison of Grounding Modes of MMC-Based Flexible DC Distribution System

DC distribution system has a high power quality and power reliability. It is conducive to the access of renewable energy and battery-based storage system. There are many fault types in DC distribution system. The fault characteristics are complex and closely related to the grounding mode. The investigation on the grounding mode is of great significance. Firstly, the basic structure, the operating principle and the control strategy of Modular Multilevel Converter (MMC) are briefly introduced. Secondly, the topology of DC distribution network is presented. The fault characteristics of single-phase-to-ground fault both in AC side and DC side are analyzed. The advantages and disadvantages of these grounding modes are discussed. The results provide references for flexible DC distribution system (FDDS) design.