An Improved FCS-MPC Based on Virtual Vector Expansion and Sector Optimization for 2L-VSCs

Conventional finite control set model predictive control (FCS-MPC) outputs one voltage vector per period by vector traversal algorithm, which leads to low control accuracy, unnecessary high computational burden and unfixed switching frequency. In this paper, an improved FCS-MPC based on virtual vector expansion and sector optimization is proposed to improve system performance and reduce computational burden for 2L-VSCs. Three aspects are improved as follows. First, a sector optimization method based on effective vector radiation range is proposed to directly determine the optimal vector without vector traversal. Second, a virtual vector expansion method based on vector synthesis algorithm with fixed 1/4 & 1/2 & 3/4 duty cycle is proposed to expand optional vectors from 8 to 44, and improve vector accuracy and system performance. Third, a modulated vector output mode is adopted per period to fix switching frequency and decrease current harmonics. Finally, the advantages of proposed MPC are verified by simulation and experiment.