A novel 72-pulse ac-dc converter based on a tapped delta autotransformer based 36-pulse converter is designed and implemented in this paper. Its main specification is its reduced kilovolt-ampere (kVA) rating. The tapped inter-phase transformer takes the role of a pulse doubling circuit to facilitate achieving a 72-pulse circuit. The circuit has been designed for retrofit applications, a tapped delta-connected autotransformer platform is also included to the converter. In this paper, the proposed scheme is simulated by MATLAB/SIMULINK considering different loading scenarios. The results show significant improvement in power quality indices (according to the IEEE-519) at the point of connection to the utility. The results show that the input current total harmonic distortion (THD) is less than 3% and satisfying power factor (almost unity) for the proposed topology. This fact indicates a significant improvement in the total cost and space of the proposed configuration in comparison with similar configurations.

Keywords: Ac-dc converter, Tapped delta autotransformer, Power quality, 72-pulse rectifier, Pulse doubling, Direct torque controlled induction motor drive (DTCIMD)