Research on the Switching Frequency Variation of Predictive Control Based on Circular Boundary-Limited Form

Model predictive control (MPC), as a new motor control scheme emerging in recent years, has the advantages of simple principle, fast response time, flexible design, easy implementation of multi-objective and non-linearity. Therefore, MPC gradually becomes a research hotspot in the field of power electronics and motor drive. However, since modulators are not used in the MPC, the switching frequency of inverter is not directly determined by the sampling period, but is influenced by various factors such as the motor speed and the weight coefficient in the cost function. For this phenomenon, this research focused on how the inverter switching frequency varies when the motor speed changes and proposed a theoretical analysis to explain the physical mechanism of the switching frequency variation, which caused by motor speed changing. A simplified physical model of the induction motor based on the counter-electromotive force and a simulation of predictive control based on circular boundary-limited form were built. Theoretical justification and simulation studies demonstrate that, under the MPC, the effect of the fundamental frequency on the switching frequency is positively correlated while the effect of the counter-electromotive force is negative correlated, which causes the switching frequency shows a trend of first rising, then falling, and finally stabilizing as the motor speed rises.