On-line improved inverter waveform by variable step delta modulation

This paper presents a new technique using delta modulation for inverter operation. Delta modulation (DM) schemes have the ability to optimize pulse width modulated (PWM) inverter waveforms online. The tuned and the multi-integrator DM are the two schemes proposed for PWM waveform synthesis so far. The methods were found useful for variable speed PWM inverter-fed AC drives. However it was observed that during tuning and filtering process, fundamental output voltage of the inverters reduced. With an aim to overcome this effect, a new technique called the variable step rectangular wave delta modulation (RWDM) is proposed. The method has the capability to maintain a near constant fundamental voltage of the output waveform of the inverters. Both analytical and experimental verifications are carried out for tuned and variable step RWDM