A passive three-phase rectifier enhanced by a DC-side high switching frequency add-on SiC-converter stage for unity power factor applications

Recent developments showed that existing passive three-phase rectifier circuits with DC-side located smoothing inductor can be extended to a low harmonic input stage by adding an additional converter stage on the DC-side of the passive rectifier system. In this paper an implementation of this converter stage using reduced number of semiconductors (only two half-bridges) is proposed. The system shows input current distortions which can be reduced considerably to values below 1% if switching frequencies of 72kHz or above are used. A proper design of the injection chokes is thereto required and several operating modes and optimization possibilities are discussed. Design guidelines are verified by simulation results and a laboratory prototype based on a 10kW/72kHz rectifier system using SiC-MOSFETs.