Model Predictive Control of a Nine-Level Internal Parallel Multilevel Converter With Phase-Shifted Pulsewidth Modulation

Abstract

Among various multilevel converter topologies, the nine-level internal parallel multilevel converter (9L-IPMC) stands out due to its capability to incorporate the advantages of both parallel modularity and active neutral point clamped converter. However, suppressing the circulating current and balancing the neutral-point voltage and six flying capacitor voltages while providing fast output current control is always a challenging task in 9L-IPMC. This is particularly true when the flying capacitor is small. This article proposes a model predictive control (MPC) scheme for the 9L-IPMC with phase-shifted pulsewidth-modulation (PS-PWM) to achieve these goals. By considering the high-frequency cell in 9L-IPMC as a whole, PS-PWM can be integrated into MPC scheme, and no parameter tuning process is required for the output current control. The internal circulating current suppression and flying capacitor voltage balancing are achieved by the flexibility of the inherent redundancy in 9L-IPMC. A thorough experimental evaluation of the proposed method has been conducted to validate the effectiveness of the proposed MPC scheme.