Harmonic analysis of two PWM waveforms in asynchronous modulation

In this paper two PWM waveforms are compared by theoretical analysis and by measurements. The two PWM waveforms are space vector modulation and third harmonic injection which are both used in the asynchronous modulation mode of an inverter. The theoretical analysis is based upon a decomposition technique of the generated waveform to obtain its spectrum. The experimental analysis is performed on a simple and reliable microcontroller-based 5 kVA inverter. It is concluded that the third harmonic injected modulation has a cleaner spectra than the space vector modulation both by theory and by measurements. The decomposition technique shows also a close agreement to FFT measurements