Four-Degree-of-Freedom Overmodulation Strategy for Five-Phase Space Vector Pulsewidth Modulation

This article proposes a four-degree-of-freedom overmodulation strategy for five-phase space vector pulsewidth modulation (SVPWM) in order to reduce the low-order harmonics of the output voltage during overmodulation. Based on the nearest-four-vector SVPWM algorithm, this overmodulation strategy calculates the corresponding third harmonic injection rate according to the modulation ratio in the overmodulation region. What is more, this strategy optimizes and controls the third harmonic so that basic voltage vectors of the fundamental wave subspace and the third harmonic subspace can be controlled simultaneously, thus effectively decreasing the low-order harmonic contents without reducing control degrees of freedom. The whole overmodulation region is divided into three subregions with linearized approximation to reduce the complexity of computation. Simulation and experimental results demonstrate that under the same modulation ratio during overmodulation, the proposed overmodulation strategy can improve the dc bus voltage utilization of a five-phase inverter, make the third harmonic controllable with four control degrees of freedom, and also reduce the low-order harmonic contents of the output voltage.

Automated summary

This article introduces a four-degree-of-freedom overmodulation strategy for five-phase space vector pulsewidth modulation (SVPWM) to reduce low-order harmonics in the output voltage. By controlling the third harmonic, the strategy aims to simultaneously control basic voltage vectors of the fundamental wave and the third harmonic subspace, effectively decreasing low-order harmonic content without sacrificing control degrees of freedom. Simulation and experimental results show that this strategy improves dc bus voltage utilization, allows for four control degrees of freedom in managing the third harmonic, and reduces low-order harmonics in the output voltage.