Stator Flux Trajectory Control with Optimized Pulse Patterns Based on Voltage Command Feed-Forward

For medium-voltage high-power drives, switching frequency is usually expected to be restricted to several hundred hertz to restrain the switching losses. In order to maintain small current distortions and torque ripples, synchronous symmetrical optimal PWM is an attractive option. Based on the closed-loop control method for induction motor using SHEPWM, a method that combines the optimal steady-state performance of SHEPWM with the fast dynamics of trajectory tracking control is proposed in this paper. The system uses feed-forward control to obtain the voltage reference, and applies stator flux trajectory tracking control when the stator flux error exceeds the limit to reduce the current impact in the transition. The proposed closed-loop control system satisfies both the steady-state as well as the dynamic performance requirements with a simplified structure. Reasonable current total harmonic distortion is maintained in steady-state operation while small current impact and fast dynamic response are achieved at low switching frequency. The effectiveness of the proposed method is validated by the simulation results obtained from NPC inverter-based induction motor drive system.