A Hardware and Software Combined PTG Fault Traversal Control Strategy of MMC

Modular Multilevel Converters are well adopted to the needs of future applications in power transmission owing to its modularity and expansibility. DC faults of the MMC can severely disrupt system operation. Demanding fast dynamic control strategy under DC faults., it is significant to propose a strategy which can achieve fault elimination and provide continuous and stable power to the loads at the same time. This paper presents a positive-to-ground (PTG) fault traversal strategy based on hardware and software control. Hardware hysteresis loop control is introduced in order to limit the fault current during the control delay period inherent in the real system. After that., by controlling the MMC bridge arm voltage., the elimination of fault currents and reliable supply of loads on the DC side are realized. Compared with the existing strategies., this strategy has the advantages of fast current-limiting response speed and simple control structure.