Novel Overlapping Technique to Realize Half Period Symmetry in the Modulation of Current Source Inverter

摘要

Overlap time periods are necessary in the modulation signal of current source inverter (CSI) to prevent the voltage spikes generated by the input inductor current. A certain algorithm is used to locate the overlap instants between the switching states. Unfortunately these periods result in low frequency harmonics and waveform distortions at the output of CSI. For example, one problem of applying overlap time is the loss of half period symmetry (HPS). Although some studies have introduced compensation methods to cancel the effects resulted by those instants, the overlap algorithm itself was not investigated and the problem of HPS couldn't be solved by only modifying the modulation signal through the compensation methods. This study presents a novel design for the overlap algorithm, in order to locate the overlap instants within the switching states such that HPS could be realized. The proposed algorithm reduces the harmonic distortion of the inverter output waveform without sacrificing the safe overlap instants.