Novel delta-sigma modulator for dc-ac converter applications-an experimental evaluation

This paper presents a comparative study between two current control techniques, namely, a basic delta modulator and novel delta-sigma modulator. The delta modulator is used widely in induction motor drives as a known method for converting analog signal in to digital form; to optimize (harmonic minimization) pulse width modulated (PWM) inverter waveforms on-line without conventional optimization processes, like selective harmonic elimination or harmonic weighting techniques. The quantization noise arises from the A/D conversion is distributed uniformly to the frequency axis. But in the delta-sigma modulator the noise varies. It provides several advantageous over Delta modulation. It can be successfully applied to over-sampling digital-to-analog and analog-to-digital data converters switch mode power supplies and switch mode inverters. The spread spectrum nature of delta-sigma modulator, noise level within unnecessary band is much reduced. It is relatively easy to implement, smooth inverter operation and provides low harmonics at the inverter output. The comparative study between delta and delta-sigma current controllers has been verified by the simulation undertaken by the MATLAB/SIMULINK environment in terms of the high switching frequency power spectra density, average switching frequency, rms current error and total harmonic distortion of load current waveforms. The obtained theoretical results are validated with experimental platform based on TMS320F2812 digital signal processor for effectiveness of the study.