A three-level push-pull inverter: analysis, design and experimentation

This paper introduces a new single-phase inverter circuit referred to as three-level push-pull inverter. The main property of this new topology, in comparison with the conventional push-pull inverter, is that it generates a three-level output voltage. Therefore, it is suitable for three-level modulation strategies that have many advantages over two-level ones. Another advantage of this power converter is that the power semiconductors are subjected to the half of the voltage in comparison with the two-level push-pull inverter. Because of the three-level output voltage, its RMS value becomes independent of the load in single-pulse modulation. Besides, by properly choosing the width of the single pulse, the third harmonic can be eliminated. As a consequence, the efficiency of a ferroresonant based UPS that usually employs push-pull inverters can be improved. Circuit operation, simulation and design, along with experimental results taken from a laboratory prototype rated at 1 kVA are presented