Development of quasi 24-step voltage source hybrid diode rectifier by injection harmonics

A new method for reducing harmonics involved in input voltages of a three-phase voltage source diode rectifier is proposed. It is applied to the conventional 6-step diode rectifier with a three-phase autotransformer. By injecting harmonics to the neutral point of the autotransformer from an auxiliary circuit, input voltages of the proposed diode rectifier can be almost the same as a conventional 24-step diode rectifier. In this paper, circuit performances and input voltage waveforms are discussed, and the optimum parameters are determined by taking effect of harmonic reductions. Then, characteristics of the proposed rectifier can be clarified by simulation results.