Quasi-Symmetrical SVPWM Scheme Based on General Volt-Second Balance Model for a Three-Phase Isolated AC–DC Matrix Converter

Since all of the three-phase isolated ac–dc matrix converters (3P-IMC) must be strictly limited to the symmetrical operation modes to maintain volt-second balance, there could be a lot of symmetrical but redundant switching actions to increase the switching loss. Hence, a generalized volt-second balance model is summarized for 3P-IMC in this article, and a quasi-symmetrical space vector pulsewidth modulation (QSVPWM) scheme is then proposed. The QSVPWM scheme has fewer current vectors to synthesize the reference current vector and, therefore, features a quasi-symmetrical switching pattern to achieve 1/6 reduction in the switching actions. Moreover, the current root-mean-square value could also be decreased with the proposed QSVPWM scheme owing to the special operation modes. Compared with the conventional symmetrical SVPWM scheme, the system loss is reduced and the efficiency is improved. The other characteristics of the proposed scheme, including operation range, duty-cycle loss, narrow pulse, flux density, and volt/ampere-second balance model, are also analyzed and compared in detail. Finally, a 600-W 3P-IMC prototype is built up to verify the performance of the proposed scheme.