Sliding Mode Control of the MMC-based Power System

The modular multilevel converter has become a popular topology for many applications in medium and high-power conversion systems such as multi-terminal direct current power systems. In this paper, Modular multilevel converter structure and related equations are presented. Then, control methods for circulating current, output current, and energy balance among legs and upper and lower arms of each phase for conventional proportional-integral control and sliding mode control are described. Notably, this study concentrates on the multi-terminal direct current configuration link with masterslave control by presenting a π model for the high voltage direct current transmission line. Moreover, dq-frame is used in the control strategy with a modified first-order sliding mode control and a second-order sliding mode control for preventing chattering. The results show that applying the proposed method in a hybrid power system can provide fast transient responses, zero overshoot, and better stability. Finally, the results are verified by simulations in MATLAB/Simulink.