A family of scalar based reduced common mode voltage PWM algorithms for induction motor drives with reduced complexity

This paper presents simplified scalar based pulsewidth modulation (PWM) algorithms for the reduction of common mode voltage. Though, the space vector PWM (SVPWM) algorithm gives superior waveform quality, it results in large common mode voltage variations due to the usage of zero voltage vectors. Moreover, the complexity involved in the classical space vector approach is more due to the calculations of angle and sector information. Hence, to reduce the complexity and common mode voltage (CMV) variations, the proposed approach calculates the gating times by using the instantaneous phase voltages only. In the proposed approach, by adding an unique zero sequence signal to the phase voltages, the modulating signals are derived. Then, by comparing the modulating signals with triangular signals, the gating pulses for the various PWM algorithms are derived. As, the proposed PWM algorithms did not use the zero states, these results in reduced common mode voltage variations. To verify the proposed PWM algorithms, numerical simulation studies have been carried out on scalar controlled induction motor drive. From the simulation results, it can be concluded that the SVPWM algorithm exhibits the CMV variations between ±V_dc/2 where as the proposed PWM algorithms exhibit between ±V_dc/6. Moreover, it can be observed that the proposed PWM algorithms result in slightly increased harmonic distortion.