Analysis of Third-Harmonic Modulation Capability of Five-Phase Motor Drive and Near-Six-Vector SVPWM Algorithm

For decades, although plenty of work has been done on modulation of the fundamental voltage component for five-phase systems, the research on modulation algorithm and modulation capability of the third-harmonic component in five-phase systems is very less. In this article, the third-harmonic component modulation capability of five-phase motor drive systems is first analyzed. It is found that the third-harmonic modulation capability of the existing modulation algorithm is very limited, which may affect the suppression or utilization of the third-harmonic voltage/current in five-phase systems. To improve the third-harmonic modulation capability, a novel near-six-vector space vector pulsewidth modulation (NSV-SVPWM) method is proposed. It is proved that the widely applied four-vector space vector pulsewidth modulation (NFV-SVPWM) is a special instance of the proposed NSV-SVPWM, and the proposed NSV-SVPWM has more candidate voltage vector combinations than those of the conventional NFV-SVPWM. Thus, a better modulation capability can be achieved by the proposed NSV-SVPWM. The analysis and the effectiveness of the proposed algorithm are proved by experiments. The purpose of this article is to clarify the issues suffered by the existing modulation algorithm and do some improvements.