Modular Multilevel Converter With Improved Indirect Predictive Controller

The modular multilevel converter (MMC) now is considered as the most promising converter in the high-voltage direct current system. An improved indirect predictive control applied in the MMC is proposed in this paper. With the proposed predictive control, the burden of communication can be reduced. The predictive precision can be improved with the proposed controller. Furthermore, the control accuracy for the system can be improved. In this paper, the mathematical model of the MMC is presented at first. Based on the model, the stability analysis of current control loop is obtained and the gain boundaries of the controllers are deduced. Afterward, the indirect predictive control is applied in the control loop. The predictive errors caused by the circuit parameters uncertainties are further deduced. Moreover, in order to eliminate the predictive error and improve the predictive precision, the repetitive controller is introduced in the submodule voltage balance controller. At last, the validity and advantages of the proposed method are verified by a bunch of simulating and experimental results.