In this article, a simple and accurate 3-D analytical model is presented to compute the magnetic-field distribution and the torque of eddy current coupling with Halbach magnets. By employing a group of H-formulations in the conductor region and Laplacian equations with magnetic scalar potential in other regions, the analytical magnetic distribution and electromagnetic torque of the coupling are predicted in the Cartesian coordinate system. The calculated results for a 300 kW coupling are compared with the numerical simulation results by using 3-D finite-element models and experimental results. The comparison verifies the low computational time and good accuracy of the proposed 3-D analytical analysis model.

This article presents the topology optimization of ferromagnetic components in electrical machines by using the density method. Explicit expressions of machine performance based on the principle of electromechanical energy conversion are derived and incorporated in the finite element model. Because the gradient-based algorithm is employed for efficient optimization, the performance sensitivities with respect to the design variables are derived subsequently. An optimization framework is then proposed to optimize effectively the electrical machine parameters and performance, such as the flux linkage, back electromotive force, and torque profile including the torque density and torque ripples. Two design examples are reported to confirm the feasibility and effectiveness of the presented topology optimization approach. The accuracy of optimal solutions is verified by using ANSYS MAXWELL, a commercial field analysis software.

This article proposes a novel variable frequency isolated bidirectional CLLC resonant converter with voltage-controlled variable capacitors (VCVCs) and auxiliary clamp circuits (ACCs). By employing the class II ceramic capacitors as VCVCs, the converter's modes in one switching cycle and the transient process to set up the dc voltage bias on VCVCs are analyzed in detail to explain the fundamental principles and lossless characteristics of ACCs in the steady state. Suitable ranges of capacitor voltage stress and current stress and gain characteristics of the converter are also given to design the resonant parameters. The converter's soft-switching characteristics, fast transient process, and high efficiency are well demonstrated by the experimental results obtained on a 500 W prototype. The high-efficiency range of the proposed converter with the VCVCs is 20%–100%, which is at least 10% wider than the others without VCVCs.

High-frequency link matrix converter (HFLMC) can directly realize dc/ac conversion without intermediate energy storage components, reduce the power conversion stage, and improve efficiency and power density. With the conventional space vector modulation strategy, the secondary-side voltage of the high-frequency transformer presents an asymmetric trapezoidal wave, which leads to the dc magnetic bias phenomenon and increases the current stress in secondary-side switches. This article proposes a novel space vector modulation strategy for HFLMC. It optimizes the space vector distribution, makes secondary-side voltage periodic and symmetric, and reduces the switching actions. The current stress is reduced, and the converter's efficiency is improved. Simulation and experiment results verify the advantages of the proposed modulation strategy.

This paper examines the maximum cogging torque (MCT) distribution characteristic of surface-mounted permanent-magnet (SMPM) machines. The MCT distributions of SMPM machines with different pole-arc coefficients and different ratios of slot opening to slot pitch are studied using: 1) the Fourier series analysis together with the Maxwell stress tensor and 2) the finite-element method. Right triangle distribution regions of the optimal MCT are determined by comparing the MCT distribution contour maps obtained by the afore-mentioned two methods. Finally, a combined MCT optimization method for an SMPM with substantial savings in the optimization time, when compared with conventional methods, is proposed.

High-frequency link matrix converters (HFLMCs) can transfer dc to ac with only one power conversion stage and without intermediate energy storage components. However, the space vector modulation (SVM) strategies and control methods in conventional HFLMCs produce excessive harmonics in the three-phase output currents and high current stress in the primary side of the isolated high-frequency transformers (HFTs). This article proposes a new optimal vector distribution SVM strategy, which maintains low switching action and reduces output current harmonic. The HFLMC's transmission power and the HFT's current stress with the proposed SVM strategy are analyzed, and a coordinated control method coupled with the modulation index and phase shift angle is determined. The proposed SVM strategy and the coordinated control can realize smaller total harmonic distortion (THD) of three-phase currents and lower HFT's current stress than the conventional SVM strategy. The simulation and experiment results confirm a low THD of 3.71% in the output current and a remarkable decrease of the current stress (2.5 to 3 A) in the HFT.