A strategy of circulation current suppressing for modular multilevel converter based on model predictive control method

In order to suppress the interphase circulating current existing in the modular multilevel converter (MMC), a circulating current suppressed model in predictive control (MPC) is presented. It is built on basis of the traditional control system. Combined with the approximation modulation of the nearest level, through testing the circulating current direction, the second harmonic circulating current can be suppressed quantitatively by updating the input module in the real-time Compared with the traditional method, there is no need for the proposed method to consider the frequency characteristics of the circulating current, the complex parameters design is eliminated, and the realization is simple. Meanwhile, the proposed method is more suitable for the practical engineering which has a large number of submodules. The simulation has been carried out in the PSCAD. The results show that the proposed strategy can suppress circulating current effectively so that the arm current distortion and the module voltage fluctuation can be greatly reduced.