Harmonic-Spectrum Spreading Effects of Two-Phase Random Centered Distribution PWM (DZRCD) Scheme With Dual Zero Vectors

In this paper, a two-phase dual-zero-vector random centered distribution (DZRCD) scheme is proposed to solve the problems of a two-phase RCD pulsewidth modulation with V(000) as the zero vector in which the discrete spectra in the case of a high modulation index (M) are not considerably reduced. In the proposed DZRCD scheme, the zero vector is selected as V(111) when M ges 0.8 and as V(000) when M < 0.8. A 16-b microcontroller SAB-C167 was used for the implementation of the proposed method. The experiments were performed on a 1.5-kW induction motor under a 2-A load condition, and for a load test, an induction motor was used as an eddy current brake. Simulation and experimental results show that the voltage and current harmonics are spread over a wideband area and that the audible switching noise is reduced by the proposed method.