The Unified PWM Implementation Method for Three-Phase Inverters

The three-phase inverter with the conventional space-vector pulse width modulation (SVPWM) algorithm has fast dynamic response, but the complex coordinate transformations, trigonometric function calculations, and sector number identification should be performed. In this paper, the relationship between SVPWM and three-phase carrier-based PWM is comprehensively analyzed. A zero-vector distribution variable k₁, which changes from zero to one, is introduced, and the influence of k₁ on characteristics of the PWM is investigated. The continuous SVPWM is generated when 0<k₁<1, and several typical kinds of discontinuous SVPWM are generated when k₁=1 or 0. The sinusoidal PWM (SPWM) and all kinds of SVPWM are unified in a modulation function expression, and it is proved that SVPWM is a zero-sequence voltage signal injection carrier-based PWM in effect. Moreover, a unified PWM fast algorithm is proposed, and it has only normal arithmetic operations and needn´t identify the sector to which the voltage reference signal belongs. The SPWM and all SVPWM methods can easily be implemented using the developed algorithm. The algorithm has the advantage of the conventional SVPWM algorithm with fast dynamic response and needs less computation time. The simulation and experiment results show that the proposed method is valid and feasible.