Modified PWM schemes for Cyclo-inverters

Modulation techniques namely sinusoidal PWM and space vector PWM, usually applied for inverters and matrix converters have been modified in this paper for applying them in cyclo-inverter. It has been found that for Sine PWM, for modulation index, m, around 0.5 to 1, the minimum total harmonic distortion factor (THD) obtained is 10%. The harmonic contents in the cyclo-inverter output gradually increase when m is less than 0.5. Cyclo-inverter output improves for space vector PWM where THD has been found to as low as 5% only. Thus, space vector modulation is recommended in cyclo- inverters as compared to sinusoidal PWM technique both in terms of switching losses as well as harmonic reduction, though at a high computational cost.