Simplified Active Zero State PWM Algorithms for Vector Controlled Induction Motor Drives for Reduced Common Mode Voltage

A simplified space vector approach based active zero state pulsewidth modulation (AZSPWM) algorithms are presented for vector controlled induction motor drive to reduce the common mode voltage variations. The space vector PWM (SVPWM) algorithms divides the zero state time equally between the two zero states. Because of the usage of zero states, the SVPWM algorithm gives large variations of common mode voltage. Moreover, as the classical space vector approach requires the angle information, the complexity involved is more. Hence, to reduce the complexity, the proposed approach calculates the switching times from the instantaneous phase voltages only. Also, in order to reduce the common mode voltage (CMV) variations, the proposed algorithms did not use the zero states. In the proposed AZSPWM algorithms, the effective zero state is created by using the two opposite active voltage vectors with equal time durations. To evaluate the proposed PWM algorithms, several numerical simulation studies have been carried out and results are presented. From the results, it can be observed that the SVPWM algorithm gives the CMV takes a value of +/- V-dc/2 where as the proposed PWM algorithms takes a value of +/- V-dc/6. Moreover, it can be observed that the proposed AZSPWM algorithms give reduced CMV with slightly increased harmonic distortion when compared with the SVPWM algorithm.