单桥臂复用型MMC单极接地故障穿越及能量均衡策略研究OA

With the rapid development of high-voltage and high-capacity flexible DC systems,the lightweight design of modular multilevel converters(MMCs)has become increasingly critical.Although the application of arm multiplexing can efficiently achieve the lightweight performance,it still faces the problems of fault ride-through and energy balance,which are even more complex.To address these challenges,the pole-to-ground fault ride-through,which is the most common DC-side fault for a single-arm multiplexing MMC(SMMC),is studied in this paper,followed by the corre-sponding energy balance control strategy.First,based on the topological structure and operation principle,a transient equivalent model is established to analyze the fault characteristics.Then,combined with the single-arm multiplexing feature,a half-wave shift non-blocking fault ride-through strategy is proposed to eliminate the system overvoltage and fault current.Furthermore,aimed at the problem of energy imbalance caused by asymmetric operation during the non-blocking fault ride-through,a dual-modulation energy balance control strategy based on third harmonic injection and commutation angle adjustment is put forward,so as to ensure the capacitor voltage balance under faults while maintain-ing transmission at 50%of the rated power.Simulation results based on a MATLAB/Simulink platform demonstrate that under the proposed strategy,SMMC can realize non-blocking pole-to-ground fault ride-through with a satisfying energy balance effect,effectively enhancing the reliability of power supply.