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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.

To accurately estimate the rotor position of an interior permanent magnet synchronous motor (IPMSM), high-frequency square-wave voltage injection (HFSVI) method has been widely used in position sensorless IPMSM drives at zero-low speed domain. However, dominant HFSVI harmonics and PWM harmonics will generate audible HF noises, which limits the practical application of the HFSVI method. Therefore, a dual random scheme proposed in this article simultaneously performs random phase signal injection (RPSI) and random N-state space vector modulation with nine segments (RNSVM9) to significantly disperse HFSVI harmonics and PWM harmonics. Since the HFSVI signal and PWM scheme are ultimately reflected on the three-phase output pulses, this article applies two-dimensional Fourier analysis to the output pulses. The principle of HF harmonics cancellation is intuitively explained by extracting the harmonic dispersion coefficient from the derivation results. Mathematical analysis shows that the proposed RPSI-RNSVM9 scheme can significantly disperse HFSVI harmonics and PWM harmonics at the same time. Finally, experimental results verify that RPSI-RNSVM9 significantly disperses all HF harmonics and has a smooth spectrum.

In the rotating armature permanent magnet motor (RAPMM), the movement of the rotor slot in relation to the stator results in variations in the electromagnetic excitation force and slot-frequency vibration. To diminish the slot-frequency vibration of RAPMM, a novel slotless rotating armature permanent magnet motor (SRAPMM) is proposed and prototype-tested. The finite element method is used to simulate the magnetic field, torque, and torque ripple, revealing that the air gap flux density and radial force remain relatively constant. Vibration experiments were conducted on two SRAPMMs having different magnetic pole widths. The results indicate that the main vibration frequency is an even multiple of the current frequency when the motor is unloaded. After loading the motor, the amplitude of the electromagnetic vibration is significantly smaller than that caused by mechanical factors, suggesting that the SRAPMM is a reliable option when strict vibration requirements are applied.

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.