Fixed-Frequency 3V-MPCC Strategy for Single-Phase NPC Inverters with Multi-Objective Optimization

Traditional finite control set model predictive control for single-phase three-level neutral-point-clamped inverters suffers from three main issues: non-constant switching frequency, high harmonic distortion, and neutral-point voltage fluctuations. In order to overcome these traditional problems, this paper explores the predictive control strategy of a three-vector model with fixed switching frequency. Taking the output voltage vector as the finite set, the objective function is reasonably constructed by optimizing the region division and vector synthesis, and finally the constant switching frequency and efficient harmonic suppression are realized under the condition of fast neutral point potential equilibrium. In view of the delay effect in predictive control, this paper proposes a two-step prediction delay compensation, which can effectively hedge the calculation delay and improve the control accuracy and dynamic response. Experimental results demonstrated that, compared to conventional finite control set model predictive control under a 10 kHz sampling frequency, the proposed method reduces the total harmonic distortion of the output current from 7.5% to 1.8%, stabilizes the switching frequency at 1.2 kHz, achieves neutral-point voltage balance, and realizes simultaneous optimization of steady-state accuracy and dynamic performance. This approach resolves the trade-off between dynamic performance and steady-state accuracy, offering a robust solution for energy integration applications under complex operating conditions.