Vector Shifted Model Predictive Power Control of Three-Level Neutral-Point-Clamped Rectifiers

Abstract

Model predictive power control (MPPC) has been emerging as one of the most promising control schemes for three-level neutral-point-clamped (NPC) rectifiers. However, conventional MPPC (C-MPPC), which only selects one switching state during the entire sampling period, leads to high active and reactive power ripples. Moreover, the heavy computational burden and variable switching frequency limit the applications of MPPC. In this article, vector shifted MPPC (VS-MPPC) methods are investigated. With the shifted vectors, the constant-switching-frequency MPPC of three-level NPC rectifiers can be simplified as that of a two-level rectifier, and the balanced neutral capacitor voltage can be easily achieved by adjusting the duty cycle of the redundant switches without any weighting factor employed. Only eight voltage vectors are calculated and shifted based on the small hexagon selection. Consequently, the computational burden is significantly reduced, even 35% less than that of C-MPPC. Furthermore, the proposed VS-MPPC presents a constant switching frequency and better steady-state control performance without evaluating all the switching states. Simulation and experimental evaluations of the proposed VS-MPPC methods with C-MPPC have been conducted to validate the superiority of the proposed VS-MPPC methods.