Modeling and implementation of sigma-delta modulation controller for DC/AC inverter

A sigma-delta modulation controlled DC/AC inverter is proposed. Modeling and analysis of sigma-delta modulation (SDM) controller are explored. The pulse width of the SDM formed by cycle-by-cycle integration loop is clearly described. System stability is studied by root-locus and Bode plot techniques. An approach to reducing the THD is conducted by Fourier analysis. A prototype of 1 kVA SDM controlled DC/AC inverter is designed and examined. Simulation and experiment are close to the theoretical predictions. The proposed inverter can provide high efficiency up to 90% under the rated power and still keep the total harmonic distortion (THD) without EMI filter within 2%.