Wireless power transfer using strongly coupled electromagnetic resonators is a recently explored technology. Although this technology is able to transmit electrical energy over a much longer distance than traditional near field methods, in some applications, its effective distance is still insufficient. In this paper, we investigate a relay effect to extend the energy transfer distance. Theoretical analysis is performed based on a set of coupled-mode equations. Experiments are conducted to confirm the theoretical results and demonstrate the effectiveness of the relay approach. Our results show that the efficiency of power transfer can be improved significantly using one or more relay resonators. This approach significantly improves the performance of the present two-resonator system and allows a curved path in space to be defined for wireless power transfer using smaller resonators.

This paper proposes a novel model predictive control for a three-phase permanent magnet synchronous motor (PMSM) with enhanced robustness against parameter variation and higher current control precision. First, the extended set of voltage vectors are adopted to increase the current control precision. Then the parameter sensitivity problem is avoided in the first stage using an indirect reference vector strategy for the sake of computation time reduction. Subsequently, the inductance disturbance observer is adopted in the current prediction process to enhance the robustness against machine parameter mismatch. The intrinsic connection between the discrete control sets precision and disturbance is analyzed. The proposed method improves the robustness against parameter mismatch and current control precision simultaneously. Experimentations are conducted to verify the effectiveness of the proposed method.

A novel parallel-hybrid dual-PM machine topology with both enhanced torque density and improved flux weakening capability, is proposed for electric vehicle propulsion in this paper. The key is to artificially construct the harmonics diversity with a single-layer concentrated armature winding in the stator and thus simultaneously couple the armature field with the excitation field produced by slot PM, rotor PM and stator DC source, respectively. Enhanced torque density is obtained in this new topology due to the symmetrical flux modulation effect between dual PM sources. Moreover, benefiting from a parallel excitation characteristic of hybrid magnetic circuit, the demagnetization risk is significantly mitigated for slot PM source and thus an extended flux weakening range is obtained. In this paper, the proposed new topology and its design mechanism are investigated, along with its electromagnetic performance evaluated based on finite element analysis. Further, some leading design parameters are analyzed and determined to provide a design guideline for the proposed new topology. Finally, a prototype is built and fully tested. Relevant experimental results agree well with the finite element predication.

Benefiting from flexible flux control and short-circuit withstand ability, hybrid excitation machine is an emerging starter generator solution for hybrid electric vehicle propulsion. However, to realize a brushless hybrid design in conventional PM machines, a three-dimensional magnetic circuit is usually adopted, leading to complicated mechanical structure and torque density sacrifice. To address this issue, a new relieving-DC-saturation hybrid excitation Vernier machine is proposed in this paper, which integrates good torque density and bidirectional flux control within a simple and brushless structure. The key is to artificially construct reluctance effect in a consequent-pole Vernier PM machine (CP-VPMM) by introducing extra DC field excitation equipped with relieving-DC-saturation ability. In this way, the advantages of bidirectional flux control in stator-DC-excited reluctance machine and good torque density in CP-VPMM are well combined in this topology, making it especially suitable for multi-mode starter generator application. In this paper, the machine structure and its design mechanism are introduced, with its electromagnetic performance evaluated by the finite element simulation. A prototype is manufactured and tested. Experiment results verify the feasibility of this new topology.

The performances of three types of magnetic gears (MGs), which are radial-flux MGs, transverse-flux MGs, and axial-flux MGs, are quantitatively analyzed and compared using 3-D finite-element method of magnetic field and mechanical motion coupled computation. To fairly compare the torque capability of different topologies of MGs, all the MGs under study have the same gear ratio, the same outer diameter, and the same axial stack length. To maximize the torque density, several important structure parameters are optimized. Scenarios using different iron core materials and different magnetization directions of permanent magnets are also studied. Based on the comparative analysis, appropriate topologies of MGs that can achieve a torque density as high as 198 kNm/m³ are suggested. The results in this paper give a good review of the torque density levels of different MGs, and hence they can be used as application guidelines.

This paper proposes a novel direct-drive dual-PM motor for electric automatic guided vehicles (AGV). The proposed motor has split teeth on stator and dual PMs in stator and rotor sides, which contributes to reduced torque ripple, and enhanced torque. The airgap field of the proposed motor is analyzed theoretically, and the slot/pole selection guideline is concluded. The simulation results of the airgap flux density are shown and Fourier Transformation (FFT) analysis results agree well with the theoretically analyses results. Besides, the effects of design parameters of the proposed motor to the performances of the proposed motor are investigated. And it is found that reduced slot open could produce improved efficiency and decreased torque ripple. The efficiency of the proposed motor is relatively high within the operation range. A corresponding prototype is fabricated and the experiment validates the design.