Space-Vector Overmodulation Strategy for Ultrasparse Matrix Converter Based on the Maximum Output Voltage Vector

In this paper, a space-vector overmodulation strategy for an ultrasparse matrix converter (USMC) is proposed. The maximum output voltage vector, which has the same phase as reference voltage, is derived accurately in space-vector modulation. According to the maximum output voltage vector, the overmodulation mode I and mode II are re-divided, the boundary voltage transfer ratio (VTR) of which is extended to 0.954, whereas the maximum VTR of USMC remains 1, and the low-order harmonic components are reduced effectively. The overmodulation strategies in both modes are realized, respectively, by the linear superimposed principle. In addition, the harmonic characteristics of output voltage in overmodulation mode are analyzed by the double Fourier integral transform method. It is shown that the output voltage contains not only (6z₁ ± 1)f_out harmonics, butalso |f_out ± 6z₂ f_in | and |(6z1 ± 1)f_out ± 6z₂f_in | harmonics. The effectiveness of the proposed overmodulation strategy and the correctness of harmonic analysis method are verified by experiments.