Field-oriented asynchronous pulse-width modulation for high-performance AC machine drives operating at low switching frequency

A novel pulse-width modulation (PWM) technique is based on the prediction of the trajectory patterns that the stator current vector describes in a field-oriented coordinate system. The method of field-oriented PWM control minimizes the switching frequency at given torque ripple. The harmonics of the field producing current are left to develop freely, permitting operation at values of switching frequency that are lower than those of the optimal schemes known so far. The optimal switching times are computed off line and are called from a memory during operation. Signal processing is performed in a simple hardware structure