Model predictive control with adjustable switching frequency for induction motor drives based on three-dimensional satisfaction space optimisation

This paper proposes a model predictive control strategy for induction motors driven by three-level inverters, enabling effective switching frequency adjustment. First, a three-dimensional satisfaction space optimisation strategy is proposed, eliminating the need for weight coefficient adjustments through self-constraints and mutual constraints of the optimisation variables. The optimal switching state is selected by comparing the maximum average dwell time within the satisfaction space, thus reducing the inverter switching frequency. Second, switching frequency is treated as an auxiliary optimisation variable, and a dynamic sliding window method is designed to efficiently track switching frequency in variable-speed systems. The boundaries of the three-dimensional satisfaction space are adjusted to regulate the switching frequency. Finally, experimental results demonstrate that the proposed strategy maintains the switching frequency of 300 Hz across the entire speed range, achieving excellent dynamic and steady-state performance at this low switching frequency.