PSCAD validation of delta-wye transformer as a harmonic filter for THD mitigation of line currents in three-phase bridge rectifier

The 3-phase diode bridge rectifier has the least line current distortion among 6-pulse rectifiers; however, its total harmonic distortion (THD) of 31.08% violates power quality standards. This paper reports distortion reduction by lowering magnitudes of harmonics in the line currents using a delta-wye transformer between the 3-phase utility and the diode bridge rectifier. The leakage inductances of the transformer windings provide a filtering effect on the line current harmonics thus providing THD mitigation of utility line currents. The efficacy of the technique is proved by Power Systems Computer Aided Design (PSCAD) simulations considering the bridge rectifier with and without the delta-wye transformer of vector group Dyl. Experimental results without and with the Dyl transformer feeding the diode bridge rectifier are presented.