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This paper analyzes and evaluates various topologies of yokeless rotary-linear (RL) machine with permanent-magnet (PM) mover targeting for the achieving high dynamic performance. For the conventional yokeless RL machines, the single-stator topology features limited slot area for armature winding excited for both motions, and the coupled magnetic fields of both motions requires complex control strategy. In order to mitigate these issues, a double-stator RL machine with hybrid PMs array, which adopts the PMs with six magnetization directions, is proposed in this paper. An improved PMs array is introduced for the double-stator topology to achieve decoupled control for both motions. In addition, an analytical model of the radial flux density is derived to reveal the characteristics of the magnetic fields in different topologies. The parametric studies towards key dimensions are conducted to provide design guidelines and obtain the optimal design. Finally, the electromagnetic performances of the proposed design are compared systematically with the conventional single-stator counterparts. It is revealed that the proposed topology can enhance the performances in both motions, namely rotary and linear motions.

Abstract With ever‐increasing concerns on energy crisis and environmental protection, there is a fast‐growing interest in wind power generation systems. As electric machines and drives are core components in wind turbines, it is a pressing need for researchers and engineers to develop advanced electric machines and drives for wind power generation. This paper provides a thorough review of modern electric machines and drives for wind power generation, with emphasis on machine topologies, operation principles, performance characteristics, as well as control strategies. The key features of electric machines and drives including their merits and demerits, e.g. torque/power density, efficiency, and cost, are compared and summarised. Trade‐offs involved in various presented methods and strategies are highlighted. The major challenges and difficulties, which electric machines and drives for wind power generation are facing, are discussed. Moreover, the developing trends and opportunities are revealed, while the latest development is also discussed.

Torque ripple is one of the most critical problems in PMSM system. In this paper, a neural network (NN) torque compensator is combined with a conventional extended state observer (ESO)-based active disturbance rejection controller (ADRC) system to suppress the torque ripple at wide machine operation speed range by generating the optimal current reference. The ESO is able to estimate and reject the low-frequency component in the torque ripple, while the remaining disturbances can be learned and compensated by the neural network. Compared with commonly used schemes, the proposed method does not need to analyze the influence of various sources of the torque ripple, such as the cogging torque, non-sinusoidal back-EMF, parameter variations, and unmodeled disturbances. In addition, the simple structure of the neural network helps reduce the computation time and save computer memory. The effectiveness of the proposed neural network compensator with both the rotor position and mechanical angular velocity as inputs is verified in the experiment under different operation speeds.

This paper reveals the fundamental reason for the asymmetrical issue in magnetic-geared machines (MGMs) based on flux modulation theory. The analysis indicates that the magnetic circuits of three-phase windings in MGMs are inherently asymmetrical. This asymmetrical issue is even more severe in conventional consequent-pole MGMs (CP-MGMs) because of the more distorted magnetic field. Hence, to address the asymmetrical issue, a novel structure featuring enhanced harmonic elimination capability is proposed in this paper. Consequently, torque density can also be improved. In particular, the proposed CP-MGM employs modular structure and axially embedded permanent magnets (PMs) to achieve symmetrical back electromotive force (EMF) waveforms and improved torque capability, respectively. To further improve the electromagnetic performance of the proposed CP-MGM, the PM arc ratio and flux modulator width ratio are analytically designed, which provides a general design guideline for CP-MGMs. To illustrate the merits of the proposed CP-MGM, a few other MGMs are included for a fair comparison based on finite element analysis (FEA). Results show the proposed CP-MGM can achieve more symmetrical back EMF waveforms and lower torque ripple, as well as lower PM consumption and higher torque density, as compared with its MGM counterparts.

Emerging topics such asenvironmental protection and energy utilization have pushed research and development of electric vehicles and hybrid electricvehicles (EVs/HEVs). In the last few decades, numerous technologies have been developed for EV/HEVimportance. In this article, key research topics in the area of EVs/HEVs, namely electric machines, electrochemical energy sources, wireless charging infrastructure, and latest EV/HEV models are covered. This paper aims to consolidate the key emerging technologies in this field and provide the readers a blueprint to begin their own journeys.

Due to their excellent efficiency, power density and constant power speed region, interior permanent-magnet (IPM) machines are very suitable for electric vehicles (EVs). This paper proposed a new IPM rotor topology, which can offer high reluctance torque, wide constant power speed range and excellent overload capability. Besides, five rotor topologies with integral-slot distributed-windings IPM machines, including four existing IPM topologies and the proposed IPM topology, are designed optimally. Their characteristics, which include d-q axis inductances, saliency ratios, electromagnetic torques, corresponding torque ripples, back-electromotive forces (EMFs), overload capabilities and flux weakening performances are evaluated quantitatively. Finally, a three phase 48s8p hybrid rotor PM machine is built to verify the performances of the proposed IPM machine. This work provides some general concepts for machine developers who are willing to build IPM machines for high-performance EV applications.

Due to the advantages of high torque density, high efficiency, and wide constant power speed range (CPSR), interior permanent magnet synchronous motors (IPMSMs) are gaining more and more attention in electric vehicle (EV) applications. There are many geometrical parameters in IPMSMs, and some of them have significant impact on the performance of such machines. This paper presents a parametric sensitivity study of the rotor geometrical parameters for a V-shaped magnet IPMSM. In which, both the individual sensitivity and the combined sensitivity with considering the interaction effects of these parameters are performed by finite-element analysis (FEA). The electromagnetic characteristics in the low-speed range, including average torque, torque ripple, cogging torque, power density, power factor, efficiency, etc. and the flux-weakening capability in the high-speed range are investigated in detail. Based on the parametric study, the V-shaped magnet IPMSM is optimized. The results show that the performance of the optimal design is significantly improved. In addition, the validity of the FEA simulation results is verified by experiment with a prototype.

To conserve rare earth resources, consequent-pole permanent-magnet (CPPM) machine has been studied, which employs iron-pole to replace half PM poles. Meanwhile, to increase flux-weakening ability, hybrid excitation CPPM machine with three-dimensional (3-D) flux flow has been proposed. Considering finite element method (FEM) is time-consuming, for the analysis of the CPPM machine, this paper presents a nonlinear varying-network magnetic circuit (NVNMC), which can analytically calculate the corresponding electromagnetic performances. The key is to separate the model of CPPM machine into different elements reasonably; thus, the reluctances and magnetomotive force (MMF) sources in each element can be deduced. While taking into account magnetic saturation in the iron region, the proposed NVNMC method can accurately predict the 3-D magnetic field distribution, hence determining the corresponding back-electromotive force and electromagnetic power. Apart from providing fast calculation, this analytical method can provide physical insight on how to optimize the design parameters of this CPPM machine. Finally, the accuracy of the proposed model is verified by comparing the analytical results with the results obtained by using FEM. As a result, with so many desired attributes, this method can be employed for machine initial optimization to achieve higher power density.

A new magnetless axial-flux doubly-salient DC-field (AF-DSDC) machine is proposed and implemented into the application of a range-extended electric vehicle (RE-EV). By employing the radial active part for the torque production, the proposed machine can produce satisfactory torque density to fulfill the requirements of the RE-EV system. With the support of the 3D finite element method (3D-FEM), the performances of the proposed machine are calculated and compared with the requirements of the typical passenger RE-EV applications. To offer a more comprehensive illustration, the common radial-flux (RF) machines are included for comparison.

In this paper, three Vernier permanent-magnet (VPM) motor, namely the inner-rotor VPM (IR-VPM) motor, the outer-rotor VPM (OR-VPM) motor and the OR consequent-pole VPM (OR-CP-VPM) motor are proposed for the hybrid electric vehicle (HEV) applications. Owing to employment of toroidal-winding arrangement, the OR-VPM and the OR-CP-VPM motors can enjoy better material utilization and easier manufacturing process than its IR-VPM counterpart. Meanwhile the OR-CP-VPM motor can utilize the consequent-pole topology to minimize flux leakage that exists in conventional design. With the support of finite element method (FEM), the motor performances among the VPM motors and the profound interior permanent-magnet (IPM) motor can be compared quantitatively.

With ever-increasing concerns for the safety and convenience of the power supply, there is a fast growing interest in wireless power transfer (WPT) for industrial devices, consumer electronics, and electric vehicles (EVs). As the resonant circuit is one of the cores of both the near-field and far-field WPT systems, it is a pressing need for researchers to develop a high-efficiency high-frequency resonant circuit, especially for the mid-range near-field WPT system. In this paper, an overview of resonant circuits for the near-field WPT system is presented, with emphasis on the non-resonant converters with a resonant tank and resonant inverters with a resonant tank as well as compensation networks and selective resonant circuits. Moreover, some key issues including the zero-voltage switching, zero-voltage derivative switching and total harmonic distortion are addressed. With the increasing usage of wireless charging for EVs, bidirectional resonant inverters for WPT based vehicle-to-grid systems are elaborated.