A Series-Connected 40-Pulse Rectifier With DC Link Passive Harmonic Reduction Circuit

Abstract

This article is focused on power quality improvement of the series-connected multipulse rectifiers (MPRs). For the dc side passive harmonic reduction method, the optimum design of the harmonic injection transformer is the key point to achieve the optimal harmonic elimination effect. First, a novel method for determining the optimum turns ratio of the harmonic injection transformer is proposed. Then, in combination with a five-phase bridge-rectifier-based MPR, the correctness of the general calculation formula is verified. In the verification processes, the operation principle and harmonic reduction mechanism are clearly analyzed before and after using the harmonic reduction circuit (HRC). The optimum turns ratio of the harmonic injection transformer obtained from the view point of minimizing the input voltage total harmonic distortion (THD) value is consistent with that calculated from general formula. Under the optimum design, the kVA rating of the HRC is only 0.87% of the load power. In experimental, the THD values of the input voltages in the 20-pulse rectifier and 40-pulse rectifier are 3.32% and 2.07%, respectively. The proposed method greatly reduces the complexity of the design processes and helpful for the development of the super-MPR. The proposed 40-pulse rectifier has high reliability, easy realization, considerable harmonic reduction ability, and quite a low load voltage ripple coefficient.