The elimination of periodic torque disturbance in permanent magnet synchronous machine (PMSM) drives is a multifrequency control task, and adding resonant parts to the controller has an impact on the robustness of the system. This article aims to address the torque-ripple reduction in PMSM drives for smooth speed control, where an extended harmonic state observer (EHSO) is designed for estimation and attenuation of the selective periodic disturbance. The defects of applying the conventional bandwidth-parameterization method to the harmonic disturbance observer are explored. To improve the disturbance-rejection capability and the relative stability, a pole-placement strategy is proposed and analyzed through sensitivity function, which can preserve the comparable dynamic performance as the conventional extended state observer at the low-frequency range. The proposed EHSO also features easy parameter tuning and a modular structure for multiple harmonic disturbance rejection. Finally, the proposed method is evaluated on a laboratory PMSM platform.

Rotor eccentricity commonly exists in permanent magnet synchronous machines (PMSMs) due to improper assembly, excessive vibration, and continuous operation. Consequently, the unbalanced magnetic pull, introduced by rotor eccentricity, may lead to unfavorable noise, vibration, and even bear damage, which makes the detection of eccentricity meaningful. Although motor current signal analysis is the most popular method to diagnose eccentricity based on the amplitudes of sideband component, it is a big challenge to classify different types of eccentricities and quantify the eccentric ratio due to the spatiotemporal coupling effect. In this article, by installing a set of Hall sensors at stator slots of PMSMs to measure the magnetic flux density in time domain, the static eccentricity and dynamic eccentricity can be easily separated. This article provides a novel complex-analytical model to reveal the single side band modulation effect in air-gap filed due to dynamic eccentricity. Moreover, a diagnosis algorithm based on frequency-adaptive notch filter is designed to identify the eccentricity type and the corresponding degree. The effectiveness of the novel diagnosis method is validated by both simulations and experiments.

Parameter identification is becoming an essential technology in machine driven industrial drives due to the requirements of high-performance control and online monitoring. However, for high-speed permanent magnet synchronous machines (HSPMSMs), due to the complexity and couplings between discrete-time model and low-value resistance, multiparameter estimation faces challenges. In this article, we propose a noniterative method to simultaneously obtain resistance and inductance of HSPMSM based on multifrequency disturbance injection. By injecting disturbances with different frequencies, the identification accuracy can be guaranteed not affected from the estimated rotor position error of sensorless control and flux-linkage error. Furthermore, it is revealed that the voltage distortion caused by the deadtime effect (DTE) could affect as a resistance, which is modeled as an equivalent DTE resistance in this article, and consequently, the brought errors for resistance identification are suppressed. In addition, the least square method is employed to solve the result fluctuation problem. At last, a noninvasive temperature estimation of stator windings is accomplished with a precision within ±10 °C. Finally, experiments are carried out on a 60 000 r/min HSPMSM to verify the proposed identification method.

The disturbance observer (DOB) can be employed in electric drives to improve disturbance rejection. The Q -filter of classical frequency-domain DOBs to attenuate multiple harmonic disturbances is high order and faces issues, including discretization, numerical precision, and frequency adaption; thus, its realization in variable-speed drives would be challengeable. This article proposes a discrete-time multifrequency DOB (MFDOB) to address these issues. The Q -filter of the proposed design is constructed with an integrator and several parallel resonators in a closed-loop structure. It uses a single parameter per harmonic to control the disturbance rejection bandwidth and the performance is guaranteed under various fundamental frequencies. The impact of the computation delay on the MFDOB-based current control is studied, and the system with less computation delay exhibits a higher stability margin and a wider range of low sensitivity. To eliminate the computation delay, a real-time pulsewidth-modulation update scheme is also developed for the DOB-based two-degree-of-freedom controller. The proposed method is evaluated on a laboratory permanent magnet synchronous machine platform.

Rotor position is essential in control of permanent magnet synchronous motors (PMSMs). In terms of resolution, structural complexity, occupied volume, anti-interference ability, environmental adaptability, and cost, embedded magnetic encoder based on linear Halls owns strong competitiveness. When linear Hall sensors are selectively installed at stator slot openings in extremely compact scenario, signal phase-shift asymmetry between two or three Hall sensors is inevitable. Conventionally, prefilter synchronous reference frame-phase-locked loops exhibit excellent phase-lock ability at fixed frequency (50/60Hz), but become ill when frequency changes especially at zero frequency. In this article, a novel transformation matrix is derived to map the asymmetric phase-shift signals onto two-phase stationary coordinate system. Then, an arbitrary phase shift-phase-locked loop is formed by replacing Clark transformation with the proposed transformation matrix, which can accurately extract rotor position and speed information in a simple and effective way, avoiding the utilization of complex notch filter. Simulations in continuous domain based on MATLAB and experiments in discrete domain based on an 18-slot/20-pole prototyped PMSM both confirm the effectiveness of the proposed method.

The Type-II synchronous-reference-frame (SRF) phase locked loop (PLL) fails to precisely keep tracking on phase of input signals when the frequency of input signals is under ramp state, whereas the type-III SRF-PLL addresses the above issue but stability problem arises. In this letter, a forward compensation (FC) module is introduced to the Type-II SRF-PLL to minimize the dc phase error due to the ramp frequency of input signals, named as FCSRF-PLL, which features low computational burden, simple structure, noise immunity, and high robustness. More importantly, the parameter tuning in the proposed method will not cause stability problem. The effectiveness of the proposed FCSRF-PLL is verified through experiments based on dSPACE.