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In this paper, the zero sequence circulating current in open winding permanent magnet synchronous machine (OW-PMSM) drives with common dc bus is systematically analyzed for the first time. It is revealed that the zero sequence circulating current is affected by zero sequence back-electromotive force, cross coupling voltages in zero sequence from the machine side, pulse-width modulation induced zero sequence voltage, and inverter nonlinearity from the inverter side. Particularly, the influences from the cross coupling voltages in zero sequence and parasitic effect of inverter nonlinearity are investigated for the first time in this paper. Then, the synthetic model of the equivalent zero sequence circuit is proposed as well. Each cause is studied independently via analytical modeling, finite element analysis, and experiments. Meanwhile, to tackle this issue, the relevant suppression strategy using frequency adaptive proportional resonant controller is presented and tested on the 3 kW OW-PMSM platform. [ABSTRACT FROM AUTHOR]

This paper proposes a novel sensorless method for open-winding (OW)-permanent magnet synchronous machine (PMSM) (OW-PMSM) with circulating current suppression. First, a zero-sequence steerable space vector pulse width modulation together with zero-sequence controller (ZSC) is implemented to suppress the circulating current existing in the OW-PMSM drive system with common dc bus. Afterward, the zero-sequence back EMF reconstructed from the output signal of the ZSC is utilized to extract the position information via synchronous phase-locked loop-based position observer. Hence, the voltage transducer and resistance network used in the conventional zero-sequence back-electromotive force-based sensorless methods can be consequently eliminated. Moreover, the proposed method requires no machine parameters, such as winding resistance, d- and q-axis inductances which are indispensable for the conventional fundamental back-EMF-based methods. The voltage disturbance components due to the resistance, inductance, and rotating cross coupling voltage drops can be avoid. Therefore, stronger robustness against the variation of machine parameters due to load or temperature variation can also be obtained. Finally, the proposed method is validated via experiments on a 3-kW OW-PMSM drive system. [ABSTRACT FROM AUTHOR]

This paper proposes a zero-sequence model-based sensorless control strategy for open-winding permanent-magnet synchronous machine (OW-PMSM) with common dc bus. The third harmonic back electromotive force (EMF) in zero-sequence is utilized to estimate the rotor position information. The novelty is that the third harmonic back EMF is reconstructed based on the zero-sequence model together with zero-sequence current, instead of using voltage transducer and three phase resistance network which can be eliminated from the control system. Due to the essence of back EMF, the developed method is appropriate for the applications including wind power generation and motor drives operating above certain speed. Meanwhile, the phase shift-based space vector pulse width modulation method for OW-PMSM is also presented for easier implementation to form zero voltage disturbance in zero-sequence from the inverter side and hence the corresponding influence can be consequently minimized. The torque ripple, loss, and parameter sensitivity analysis are also carried out, as confirmed by predictions of two-dimensional finite element analysis. Due to the essence of decouple, the estimation can be more robust than the conventional fundamental model-based sensorless methods. Finally, the effectiveness of the proposed method is validated experimentally on a 3-kW OW-PMSM drive system with 2.5 kg·m2 total inertia. [ABSTRACT FROM AUTHOR]

This article investigates the nonlinear behavior of the conventional voltage feedback flux-weakening control, i.e., the voltage magnitude feedback control on the nonsalient permanent magnet synchronous machine, and proposes an adaptive control parameter tuning method for the voltage feedback controller. Due to less voltage margin in the flux-weakening region, the current dynamic performance is degraded. This issue is more serious when the system operates in the overmodulation region and could affect the system's stability. Based on the designed voltage feedback controller, the system performance in the flux-weakening and overmodulation regions is further improved by utilizing the current and voltage reference modifiers. Consequently, the system can operate well in both linear and overmodulation regions with the specified scaling factor, which is beneficial to general-purpose applications. The viability of the proposed method is demonstrated by the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the partitioned stator flux reversal permanent magnet (PM) (PS-FRPM) machine and the conventional magnetically geared (MG) machine operating in both stator-PM (SPM) and rotor-PM (RPM) modes are comparatively analyzed in terms of electromagnetic performance to provide design guides for an MG machine regarding an SPM- or RPM-type machine and a higher or lower gear ratio machine. It is found that an SPM-type machine is recommended since both PS-FRPM and MG machines operating in SPM modes have a higher phase back-EMF and hence torque than their RPM counterparts, respectively, as a result of a similar phase flux linkage but a higher electric frequency since the iron piece number is larger than the PM pole-pair number. Moreover, a smaller gear ratio machine is preferred from the perspective of a higher power factor and hence a lower inverter power rating, as the conventional MG machines with higher gear ratios suffer from larger flux-leakage, higher synchronous reactance and hence lower power factors, as well as higher iron losses, than the PS-FRPM machines. However, higher gear ratio machines feature lower cogging torques and torque ripples due to the smaller difference between the PM pole-pair number and iron piece number. Both prototypes of PS-FRPM machine operating in SPM mode and MG machine operating in RPM mode are built and tested to verify the finite element predicted results. [ABSTRACT FROM PUBLISHER]

A partitioned stator hybrid excited machine is proposed, in which the permanent magnets and field windings are alternately placed on an inner stator separated from the outer stator having armature windings. This machine inherits the features of brushless machines and benefits from better space utilization. The operating principle and the effects of slot/pole combinations are investigated in detail. Further, based on 2-D finite-element analysis, the electromagnetic performances of the proposed machines, including back-electromotive force, cogging torque, flux regulation range, torque capability, power factor and torque–speed curve, are evaluated. The results reveal that the proposed machines can exhibit wide flux regulation range as well as good torque density. The prototype is manufactured and tested to validate the predictions. [ABSTRACT FROM PUBLISHER]

In this paper, a novel winding switching (WS) strategy is proposed for the speed range extension of a dual-stator permanent magnet machine (DS-PMM), which can achieve simple and effective dynamic mode conversion over an entire operating region. Two types of WS circuits with an inverter and two switch groups were first designed to enable the winding reconfiguration of the machine, which could operate in three modes. The WS principle was then elucidated by introducing simplified equivalent circuits. Besides, the torque–speed curves of the machine under different operating modes were analyzed, based on the mathematical model. A speed-based WS controller was, subsequently, designed to generate the WS control signal and realize the multi-mode operation according to real-time operating conditions. The feasibility of the proposed WS strategy for extending the speed range of the DS-PMM was, finally, verified by experiments. [ABSTRACT FROM AUTHOR]

This paper mainly focuses on the investigation and analysis of a novel consequent-pole flux-intensifying memory machine (CP-FIMM). The proposed CP-FIMM exhibits the advantages of a satisfactory flux-regulation range, reduction of the required magnetizing current magnitude, as well as similar torque with much less PM utilization compared to its conventional counterpart. By designing the q-axis flux barriers, the flux-intensifying structure can be realized to enhance the demagnetization withstand capability of the CP-FIMM. The machine topology and operating principle are described. Moreover, the equivalent magnetic circuit model is developed to highlight the performance improvement of the proposed CP-FIMM. Finally, the electromagnetic performance of the proposed CP-FIMM is compared with that of a benchmark conventional FIMM by 2-D and 3-D finite element analysis. [ABSTRACT FROM AUTHOR]

This paper develops a design methodology for switched flux (SF) hybrid permanent magnet memory machines (HPMMMs). The memorable flux is achieved due to the variable magnetization level of low coercive force (LCF) permanent magnets (PMs) Thus, the associated excitation loss is negligible, resulting in high efficiency operation over a wide speed range. A general hybrid PM magnetic circuit is modeled, which is characterized by spoke-array NdFeB PMs and LCF PMs sandwiched between an outer stator ring and an inner stator pole. Based on the magnetic circuit, the design conflicts within the stationary side are unveiled. Thereafter, the machine configuration is introduced, followed by a description of the design procedure. First, the optimal stator pole number is determined based on one-phase machine models. In addition, a simplified permeance function is utilized to analytically optimize the rotor number, accounting for different ratios of the slot opening to NdFeB PM thickness. The electromagnetic performance of the machines with alternate stator/rotor pole combinations are compared. The design guidelines for LCF PMs are presented. Finally, the theoretical analysis is verified experimentally on the prototype machine. [ABSTRACT FROM AUTHOR]

Permanent-magnet vernier machine (PMVM) is a relatively new type of PM machines. An analytical subdomain model accounting for tooth-tips and flux modulation poles is developed to accurately predict on-load field distributions in PMVMs. Based on two-dimensional (2-D) polar coordinate and magnetic vector potential, this method solves the Maxwell’s equations in slot, air-gap, flux modulation pole slot (FMPS), and PM regions. Consequently, the electromagnetic performance such as cogging torque, back-electromotive force (EMF), electromagnetic torque, power factor, and magnet loss are calculated. In addition, the model can also be used for the evaluation of demagnetization withstand capability. The finite-element analysis (FEA) and experimental results validate the accuracy of the developed analytical model. [ABSTRACT FROM PUBLISHER]

Alternating-current motor drive systems consume the majority of global electricity, but most of them are still not efficient enough. This paper proposes a complete solution to the efficiency enhancement of general induction motor (IM) drive systems with the least cost and a high reliability. On the motor side, the squirrel-cage rotors of IMs are replaced with optimally designed interior permanent-magnet (PM) rotors without damping windings; meanwhile, other assemblies remained unchanged. Stators with both wye- and delta-connected windings are investigated, and super premium efficiency (IE4) is achieved on all the remanufactured motors in this paper. On the drive side, the maximum efficiency per ampere algorithm is realized based on the position-sensorless control to better exert the motor efficiency and reduce the system cost. For applications where an original IM is used under a grid drive, this paper safely switches the remanufactured interior PM synchronous motors from an inverter to the grid drive. A total of seven prototypes with different rated powers and velocities are remanufactured, and various experiments are provided as the verifications of the effectiveness and practicability of the proposed solution. [ABSTRACT FROM PUBLISHER]

To improve the starting performance of a permanent-magnet traction machine without a weight transducer in a gearless elevator, an adaptive starting torque compensation strategy is proposed in this paper. The dynamic model of the direct-drive elevator traction system considering the rope elasticity, the brake releasing, and the friction torque is established. Based on the dynamic model, the characteristics of the synthetic load torque exerted on the traction machine during elevator start-up are obtained. In order to balance the unknown load torque for the gearless elevator, a fuzzy self-tuning strategy is adopted to generate a suitable starting torque for compensation by tuning the change rate of electromagnetic torque according to the encoder signal. The torque compensator is designed with the aim of getting a minimized sliding distance and avoiding traction sheave reversal. Both simulation and experimental results are provided to verify that the proposed weight-transducerless adaptive starting torque compensation strategy can achieve superior riding comfort of shorter sliding distance, faster dynamic response, and smaller sliding speed. [ABSTRACT FROM PUBLISHER]

For the purpose of improving the performance of sensorless interior permanent magnet synchronous motor (IPMSM) drives, an enhanced electromotive-force (EMF)-based position observer adopting second-order generalized integrator (SOGI) to eliminate the harmonic error is proposed. The inverter nonlinearities and flux spatial harmonics that give rise to the harmonic error of position estimation are analyzed. A harmonic decoupling network consisting of multiple SOGIs based adaptive filters is adopted to achieve the multiple selective EMF harmonic elimination (MSEHE). The application of the frequency-locked loop ensures the SOGI resonance frequency adaptive, which is critical for the variable-speed operation in IPMSM drive applications. Using the SOGI-MSEHE in the position tracking estimator, the low-order harmonics in the estimated EMF can be effectively eliminated, contributing to cancelling the position estimation harmonic error. The effectiveness of the proposed enhanced position observer is verified by the experimental results at a 2.2-kW IPMSM sensorless drive. [ABSTRACT FROM PUBLISHER]