Large current rectifier and its active harmonic reduction

An active method using the active inter-phase reactor (AIPR) is proposed to reduce the harmonics in a star-connected autotransformer based large current rectifier. When not using the AIPR, the input current, load voltage and the kVA rating of the autotransformer were calculated. The auxiliary circuit connected with the secondary winding of the AIPR was proposed and its control block was also presented. When the harmonics of the input line currents were reduced to the most degree, the input current of the auxiliary circuit was confirmed, and effect of the AIPR on the load voltage and kVA rating of the autotransformer was also analyzed. The experimental results show the total harmonic distortion (THD) of the input line current is about 3.7% after using the AIPR, and the kVA rating of the AIPR is about 5.1% of load power, which mean that the cost of the harmonic reduction is low; the load ripple has six pulses per power supply cycle, which is not affected by the active harmonic reduction method; the active harmonic reduction method changes the current across the winding of the star-connected auto transformer, which results in that the kVA rating of the autotransformer increases from 95% to 105%. © 2020, Harbin University of Science and Technology Publication. All right reserved.