Carrier Based Hybrid PWM Algorithm With Reduced Common Mode Voltage For Three Phase Voltage Source Inverter Fed Vector Controlled Induction Motor Drives

This paper proposes a simple carrier based Hybrid active zero state pulse width modulation (HAZSPWM) Algorithm (HPWM) which is capable of reducing the common mode voltage produced by the Pulsewidth Modulation (PWM) Inverter fed vector controlled induction motor drive. The classical vector controlled algorithm gives variable switching frequency operation and increased harmonic distortion due to the presence of hysteresis controllers. Even though the conventional SVPWM gives superior waveform quality, there exist large common mode voltage variations and the complexity involved is also more. To overcome the above problems, this paper presents a carrier comparison approach in a simple form. The addition of zero sequence signals with the instantaneous reference phase voltages gives the modulating signals for AZSPWM algorithm. The pulses to the inverter switching devices are generated by comparing the modulating signals with two triangular carrier waves. However, due to the exclusion of the zero voltage vectors, the common mode voltage variations can be minimized from 2 dc V ± to 6 dc V ± when compared with the SVPWM algorithm. Furthermore, the rms flux ripple which is a measure of current ripple characteristics are plotted for all the sequences of AZSPWM algorithm. Then, in each sampling time period, the suitable sequence, which gives reduced common mode voltage, is applied to obtain the HAZSPWM algorithm. To evaluate the proposed algorithm simulation studies have been carried on vector controlled induction motor drive and the results are presented. The results show good agreement with the proposed work. Keywords—AZSPWM, common mode voltage, SVPWM,DPWM,CMV,VSI, vector control.