Passive auxiliary injection circuits for pulse tripling in three parallel-connected rectifiers

This paper proposes two types of passive auxiliary injection circuits (PAICs) that enable pulse tripling in three parallel-connected rectifiers, addressing the limitation of pulse multiplication to a factor of 2. The proposed design combined three rectifier units with two PAICs consisting of a delta/star transformer and nine auxiliary diodes. By further integrating the PAICs with conventional topologies such as 3-pulse star, 6-pulse star, 6-pulse bridge, 18-pulse star, and 18-pulse bridge rectifiers, we constructed 9-pulse star, 18-pulse star, 18-pulse bridge, 54-pulse star, and 54-pulse bridge configurations, respectively. The validation in MATLAB/Simulink demonstrated that these configurations achieved a threefold increase in both output-voltage pulses and input-current steps without the need for complex phase-shifting transformers. Moreover, the total harmonic distortion of the input current was significantly reduced, with values of 12.63%, 3.66%, 3.43%, 2.24%, and 1.90% for the respective designed rectifiers. To the best of our knowledge, this is the first demonstration of a passive pulse-tripling circuit for three parallel-connected rectifiers, offering a simple solution for high-current industrial applications.