Inter-phase interleaving for balance operation of three phase voltage source converter with low non-triple carrier ratio

This paper presents the use of inter-phase interleaving for three-phase voltage source converter (VSC). With the proposed inter-phase interleaving, the output three-phase voltages can be balanced even though low non-triple carrier ratios, such as 5 or 7, are used for the VSC. First, the impacts of sideband harmonic components on the fundamental component are analyzed in detail. The validity of analysis is demonstrated by the explanation of beat phenomenon related to non-integer carrier ratio. Based on the analysis, the unbalance issue of output voltages due to non-triple carrier ratio is explained. After that, the inter-phase interleaving control method is proposed to correct such unbalance. With this control method, the output voltages are balanced even with non-triple carrier ratios. The corresponding penalty of potential higher current THD is also discussed in detail. The analysis and control method can be applied to both two-level and multi-level converters. Experimental results verify the analysis and the feasibility of the proposed control method.