Influence of zero width period on the AC-side line current harmonics of 5-level MLCR CSC

The multi-level current reinjection (MLCR) concept produces high quality line current waveforms in current source converters (CSC) by injecting an reinjection current. Two rein-jected waveforms: Symmetrical waveform and Linear waveform are known. In this paper the influence of varying the zero width period (ZWP) of symmetrical waveform on line current harmonics of self-commutated MLCR CSC is studied. Different ZWPs are used and optimum ZWP is identified. The effect of different ZWP of the linear waveform on the thyristor based MLCR CSC is presented. This paper also investigates the effects of negative firing angle on the THD levels of the line currents drawn by both CSCs using PSCAD/EMTDC.