Generalized Single-objective FCS-MPC with Hierarchical Structure to Reduce Computational Burden in Flying Capacitor Converter

This paper proposes a generalized control method to reduce computational burden based on finite control set-model predictive control(FCS-MPC) in a single-phase flying capacitor multilevel converter(FCMC). The proposed method consists of FCS-MPC with a hierarchical structure, which controls the grid current and flying capacitor voltage step-by-step using their respective cost functions. The proposed method reduces the number of calculations by segmenting power devices into groups and sequentially finding the optimal state using a round-robin priority. In addition, the optimal state is found simply through calculation without comparison due to the single-objective cost function. Therefore, the amount of calculation is significantly reduced compared with the conventional method and leads to a shortened execution time. By reducing execution time, the sampling period can be shortened, thereby increasing the switching frequency. Furthermore, by using a smaller inductor, the total harmonic distortion(THD) of the grid current can be reduced. The effectiveness of the proposed method is verified through simulation and experiment using a single-phase 6-level FCMC at the laboratory scale.