Three-Phase Two-Level VSIs With Significant PWM Harmonics Dispersion and Improved Performance Using Generalized N-State Random Pulse Position SVPWM With Constant Sampling Frequency

Constant sampling frequency, excellent pulsewidth modulation (PWM) harmonics dispersion performance, and avoidance or reduction of extra switching counts (ESCs) are three important factors in evaluating the performance of different random PWM (RPWM) strategies in closed-loop control systems. However, existing strategies cannot achieve all these three important factors at the same time. Therefore, this article proposes generalized N-state random pulse position space vector pulsewidth modulation (GNSRPP-SVPWM) to achieve these three important factors at the same time. GNSRPP-SVPWM randomly selects one of the well-designed carrier patterns for each carrier period. Compared with random carrier frequency PWM whose sampling frequency varies with the carrier frequency, GNSRPP-SVPWM maintains constant sampling frequency, thereby achieving applicability in closed-loop control systems. Compared with fixed carrier frequency RPWM (FCF-RPWM) without ESCs, GNSRPP-SVPWM has much better PWM harmonics dispersion performance. Compared with the traditional FCF-RPWM with ESCs, GNSRPP-SVPWM has the same excellent PWM harmonic dispersion performance while significantly reducing single-phase ESCs and completely avoiding simultaneous two- or three-phase switching operations, thereby improving the inverter performance. By mathematical analysis, the PWM harmonic dispersion principle and avoidance or reduction of ESCs for different GNSRPP-SVPWM strategies are discussed in detail. Both simulations and experiments verify the effectiveness of GNSRPP-SVPWM at last.