A study on stable torque control in overmodulation region for high speed PMSM systems

This paper presents a study on a stable torque current control near the overmodulation region. In order to increase dynamic response and extend speed limit, overmodulation method is generally used. Overmodulation helps to increase inverter output voltage, but generate 6-th harmonic. Because of torque ripple, it is hard to apply to the low speed region. In case of high speed region has two problems in this approach. The first is windup and bump transfer phenomenon near limited DC voltage. The second is high order harmonic component by overmodulation. An anti-windup and bumpless transfer is applied to the torque control to solve these problems, and ripple estimator is used for reducing 6-th harmonic in overmodulation region. It is shown that application of this method leads to stable torque control in overmodulation region for high speed PMSM systems under limited DC voltage.