Abstract
This paper proposes a novel non-constant asynchronous modulation frequency algorithm for SVPWM over-modulation. Traditional asynchronous space-vector PWM (SVPWM), asynchronous modulation frequency remains unchanged form linear region to over-modulation region. In high power permanent magnet synchronous motor (PMSM) drive system, low switching frequency limits asynchronous modulation frequency of asynchronous SVPWM. When the modulation ratio is high, inverter output voltage positive and negative half-cycle asymmetry is obvious, especially in square wave mode. This will result in a large current distortion. Multi-mode pulse-width modulation is employed as a traditional solution, where asynchronous SVPWM is used only in low speed region. But the scheme has modulation mode switching and dynamic performance problems. The non-constant asynchronous modulation frequency SVPWM over-modulation algorithms uses in drive system in full speed region. The system can transit automatically from over-modulation mode to square wave mode with low switching frequency. The algorithm can limit the output pulse voltage asymmetry and reduce the current distortion. The over-modulation algorithm combines with negative direct axis current compensation weakening control method. PMSM drive system can be controlled with great performance in full speed region. The proposed method has been verified by simulation and experiment.
