Realization of Smooth Transition in Hybrid PWM Scheme for Induction Motor Control

Hybrid pulse width modulation schemes are widely used in high-power traction converters with a limited switching frequency. During the transition between modulation modes, sudden changes in the voltage harmonics cause the induction motor to enter a transient process, and ultimately lead to torque impacts, current shocks and other adverse effects. To improve the existing solution for such effects, theoretical support is provided in this paper by using an equivalent circuit model and a dynamic model of an induction motor, and a specific implementation scheme for a smooth transition is given considering the third-harmonic frequency component that appears in the phase voltage during the transition. The feasibility and correctness of the scheme are proven by a simulation and an experiment.