Stepped Voltage Dc/Ac Inverter --Part I: Analysis

A DC/AC inverter whose voltage is constructed from discrete low level DC sources to form a stepped sine-wave-like output is introduced. The criterion of optimal approximation of the stepped waveform to a sinewave was the minimum mean square error. The internal resistance of the generated source voltage is time varying since the total series resistance changes with the wave shape. When a constant resistive load is connected to such a load, the load voltage shape does not follow the source voltage and the optimal approximation to a sinewave of the two voltages will depend on two different switching policies: one adaptive to the source voltage and the other adaptive to the load voltage'. The inverter operation for both cases is analysed, and the main harmonic voltage and power, harmonic spectrum and distortion are obtained. The proposed inverter has superior properties characterized by its low distortion and high efficiency.