Hybrid Model Predictive Control of Active-Neutral-Point-Clamped Multilevel Converters

Abstract

To reduce the power losses, the high-voltage switches in active-neutral-point-clamped (ANPC) multilevel converters always operates at the fundamental frequency. Moreover, DC-link capacitor and flying capacitor voltage balance control is mandatory in addition to output current control in the ANPC converters. Model predictive control (MPC) can provide this flexibility and feature high dynamics for transient operations. However, conventional MPC experiences variable switching frequency, high total harmonic distortion. Moreover, as there is no modulator in the conventional MPC, it is very hard to guarantee the fundamental-frequency operation of the high-voltage switches. Given the issues above, a hybrid MPC is proposed to control the ANPC converter in this paper, where finite-control-set MPC is utilized for high-voltage switch control, and duty-cycle-optimized MPC is utilized for the low-voltage switch control. The proposed MPC features a fixed switching frequency and improves the steady-state performance with simplified implementation. The validation of the proposed hybrid MPC strategy is conducted on a five-level ANPC converter.