Analysis of Scalar PWM Approach with Optimal Common-Mode Voltage Reduction Technique for Five-Phase Inverters

Research on common-mode-voltage (CMV) reduction in multiphase drive systems has recently met an intensified interest in the available literature. This paper first explores two existing space-vector-based CMV reduction (CMVR) schemes for five-phase voltage source inverters, represented as CMVR1 and CMVR2, which reduce the CMV by 40% and 80%, respectively. Moreover, a new space-vector-based CMVR scheme, termed as CMVR3, is proposed that not only minimizes the CMV but also reduces the overall switching losses when compared with the other schemes. The optimal duty cycles and the switching sequence of all schemes are introduced. Since the implementation of space-vector-based schemes using look-up tables is a relatively complex and time-consuming process, this paper proposes a simpler scalar PWM approach. This approach can easily be implemented using embedded PWM modules of most commercial digital signal processors. To evaluate the performance of the presented CMVR schemes, a detailed evaluation study is presented. The optimal CMVR scheme over the full modulation index range is also highlighted. The theoretical findings are verified using a prototype five-phase induction machine through simulations and experimentally.