The distortion of bridge arm current is caused by the interphase loop current between MMC and HVDC

causing increase of peak of bridge arm current and of power loss and threating seriously balance of capacitive of sub-model and life of capacitor. Therefore

in this paper

the operating principle and mathematical model of MMC-HVDC is analyzed and the generation mechanism of inter-phase loop current of MMC is analyzed further. It is shown b y the analysis that in the loop current there is no odd number harmonics but even number harmonics

in which the harmonic contents of 2nd

4th and 6th loop current are the largest proportion. On this basis

a new type loop current control strategy based on quasiPR controller is proposed. This control strategy not only overcomes such disadvantage of tradi-tional PR controller as weak shift ability in resisting grid frequency and narrow wideband

but also reduces the application quantity of quasi-PR control and reduces the complexity of system design. Both the correctness and superiority of the proposed control strategy is verified by the simulation and experimental results.