The circuiting current existing among three legs of modular multilevel converter based high voltage direct current (MMC-HVDC) directly influences system performance and increases loss. According to arm-current containing second harmonic frequency

a modular multilevel converter (MMC) circulation mathematical model under static two-phase coordinate is developed. In order to realize zero-error tracking of sinusoidal input

the quasi proportional-resonance (PR) controller realizing block diagram is designed

and a circulating current restraining control strategy based on quasi PR is designed. Relative to the circulating current restraining controller in the rotating reference frame

this strategy is able to realize decoupling control without applying feed forward

thus reducing parameters adjustment workload. And without coordinate transform

delay is decreased and response speed is improved. Finally

a simulation model of MMC is built with PSCAD/EMTDC simulation platform

the results verifying the effectiveness of the circulating current restraining control strategy based on quasi PR. This work is supported by National High Technology Research and Development Program of China (863 Program) (No. 2011AA05A102).