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In previous studies, generalized N-state random pulse position space vector pulsewidth modulation (GNSRPP-SVPWM) has been verified to significantly disperse dominant high-frequency PWM harmonics with constant sampling frequency. However, due to the short durations of zero-voltage vectors at high modulation ratios, SVPWM with two equally distributed zero-voltage vectors is inferior than discontinuous PWM (DPWM) with one zero-voltage vector in reducing harmonic distortion and switching power losses. Therefore, to significantly disperse dominant high-frequency PWM harmonics, reduce harmonic distortion and improve inverter performance, this article proposed GNSRPP-DPWM, which is more advantageous than other random PWM (RPWM) strategies at high modulation ratios. In addition, by avoiding the switching operations of the phase with higher phase current magnitude, GNSRPP-DPWM further reduces switching power losses. At the same time, GNSRPP-DPWM maintains constant sampling frequency, thus not affecting the closed-loop control system. Mathematical analysis, simulations and experiments all verify the effectiveness and advantages of the proposed GNSRPP-DPWM.

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.

By injecting a high-frequency square-wave voltage (HFSV) signal into the d-axis in the estimated rotor reference frame of an interior permanent magnet synchronous motor (IPMSM), the rotor position can be accurately extracted at the zero-low speed domain. However, since the voltage expected to be applied to IPMSM must be modulated by the pulsewidth modulation (PWM) technology, two types of HF harmonics, i.e., HFSV injection (HFSVI) harmonics and PWM harmonics will generate HF audible noise in low-switching-frequency applications. Therefore, this article proposes a novel dual random scheme in the HFSVI sensorless control of IPMSM drives to significantly reduce HFSVI harmonics and PWM harmonics. The proposed dual random scheme performs random phase signal injection (RPSI) and N-state random zero-vector distribution (NSRZVD) at the same time. By applying 2-D Fourier analysis, it is found that RPSI significantly reduces HFSVI harmonics, and NSRZVD reduces both PWM and HFSVI harmonics, respectively. When performing RPSI and NSRZVD at the same time, almost all HF harmonics are significantly reduced, thereby reducing HF vibration and audible noise. Experiments conducted on an IPMSM sensorless control system verify the effectiveness of the proposed dual random scheme at last.