Unity power factor rectifier-inverter structure operating under unbalanced supply and variable dc bus voltage

A recently introduced method of improving converter input current waveforms as well as power factor are re-evaluated under non-ideal operating conditions, that is, variable DC bus and unbalanced supply. The proposed method makes use of a novel controlled front-end diode rectifier of a rectifier-inverter structure. The technique involves the use of bi-directional bi-pass switches across the front-end rectifier, with a dSPACE-based intelligent control algorithm. The operation of the converter is fully analysed as possible DC/AC drives and a complete design example is provided. The main feature of the topology is low cost, small size, high power factor and simplicity. It is found to be a universal retrofit for DC drives, and in the front-end rectifier of existing three-phase AC drives, UPS etc. for power factor correction without any passive or active filtering.