Optimal Pulse-Width Modulation with Three Bridges on Criterion of Power Losses at Load

The authors consider an analytical approach towards the optimization of the quality of pulse-width modulation with three half-bridges. The current modulation error is a difference between the current induced by a modulated voltage function and the current, induced by a modulating voltage function. The measure of the modulation quality is interpreted as a numerical characteristic of a quadratic modulation error (dispersion) at some time slot. The three-phase modulation is understood as modulation with three half-bridges. To evaluate the modulation quality, the authors use an average value of the quadratic current modulation error at the modulation period (local dispersion) and at the modulating function period (integral dispersion). Free variables, on which one can conduct the optimization of a three-phase pulse-width modulation, are the parameters of pulse displacement in relation to the center of the modulation interval and the pre-modulation function. In addition, the commutation functions of an optimal pulse-width modulation on the current dispersion criterion at load. The minimization of current dispersion leads to the reduction in modulating power losses at load. The approach to the three-phase optimal pulse-width modulation, considered in the paper, is universal and can be generalized for a multi-phase pulse-width modulation.