The True Unity Power Factor converter — A practical filterless solution for sinusoidal currents

High power conversion entails the necessity of converters interfacing with the grid which have both low losses and low harmonic content. For this purpose several topologies have been proposed, but, due to the restriction imposed on the switching frequency, these topologies often make use of complex multi winding transformers or large sinusoidal filters. These features increase cost, losses and reduce reliability of the converters. This paper proposes a new solution called True Unity Power Factor (TUPF) converter, which makes use of a well selected PWM pattern, a simple three winding transformer and two or three level active rectifier topologies. As the name implies, this converter is capable of delivering a true unity power factor conversion and accomplish these task keeping a low enough switching frequency without using any capacitive filter element. This paper shows the mains elements of the TUPF concept, some applicable regenerative or non-regenerative topologies, simulation and experimental results.