Effect of sampling space vector modulation in speed control loops of ultrahigh speed drives

In recent years increasing attention has been paid to high speed drives, where the frequency ratio is low owing to the necessarily high fundamental and limited switching frequencies. Thus, the selection of the applied PWM technique in the power electronic converters becomes crucial. The widely applied Space Vector Modulation (SVM) technique implemented in ultra high speed induction machine (USIM) drive is studied, where the speed of the USIM is controlled mainly by Field Oriented Control (FOC) and less frequently by a closed loop V/f control. Two sampling methods of SVM technique, the Regular Sampled (RS) and the Naturally Sampled (NS) are compared in the above control methods both for synchronous and asynchronous PWM. Our finding is that RS-SVM can result in instabilities in FOC, while the NS-SVM can generate subharmonic and DC current components with considerable amplitudes.