The yokeless and segmented armature axial flux machine is considered an excellent topology for electric vehicles application. However, its performance is severely limited by the stator cooling system. The heat pipe, as the small size, lightweight, but highly efficient passive phase-change cooling element, has been attracting more and more attention in the thermal management methods of electric motors. Therefore, the relationship between the thermal performance of the heat pipe with temperature is measured in detail through an experimental test platform in this paper. Further, a novel stator cooling structure that combines the heat pipe with the housing water-cooling method is introduced to improve the temperature distribution of the stator. Computational fluid dynamics (CFD) simulation verifies that the proposed cooling structure can accelerate the release of heat from the stator and reduce the temperature of the stator significantly.

In this paper, the dual-stator axial-field flux-switching permanent magnet (DSAFFSPM) motors with E- and U-core stator modular segments, as well as different stator/rotor-pole combinations are compared. The operation performance of the DSAFFSPM machines are explored by using the MMF-permeance model method. A more comprehensive theoretical analysis, no more limited to numerical calculation, is presented. This reveals directly the relations between the operation performance and design parameters of the machine. The performance comparisons between the E-shaped and U-shaped teeth DSAFFSPM machines are given, including the effects of the structural parameters on the electromagnetic torque, different stator/rotor-pole combinations on the winding factor and gear ratio, the differences of the average torque and the torque density and the efficiency in the 12/10 U-core and 6/10 E-core topology. These are the basis of the DSAFFSPM machine design and optimization. Finally, the experiments on the two prototype, 6/10 E-core and 12/10 U-core DSAFFSPM machines are carried out. The results show that the average torque of the 12/10 U-core prototype is higher than that of the 6/10 E-core prototype, while the torque density and the efficiency of 6/10 E-core DSAFFSPM machines are much higher.

It is essential to estimate stator inductance and rotor flux linkage online for fault diagnosis and high-performance control of surface-mounted permanent magnet synchronous machine (SPMSM). The current injection method is a popular way to estimate the two parameters. However, the dead-time influence of voltage-source-inverter (VSI) and the stator inductance variation caused by injected current could not guarantee the converge of the estimation. To solve the above two problems, a method of injecting square-wave angle for online parameter estimation is proposed in this article. First, the theory of eliminating dead-time influence with and without square-wave angle injection is analyzed. Next, the least square algorithm is adopted to estimate stator inductance without injection. Then, the rotor flux linkage is estimated by injecting a square-wave angle. The saturation effect of estimation is also analyzed, and both parameters are estimated without acquiring any nominal values. At last, the appropriate amplitude and frequency of square-wave angle are determined by the parameter error and convergence analysis. The proposed method is evaluated with simulation and extensive experiments under various speed and load conditions. It is noteworthy that not less than two parameters are estimated without the dead-time influence and the injection will not cause inductance variation, which is different from the previous work.

Interlinking dc-dc converters are essential in urban-area dc distribution grids to interconnect the medium-voltage (MV) and low-voltage (LV) buses. The increasing installation of renewable energy sources at the LV side will result in backward power flow through these converters, which is usually less than the forward power. This article presents an asymmetrical-bidirectional input-series output-parallel (AB-ISOP) dc-dc converter with a partial-scale backward power rating to satisfy the above realistic requirement. Single-active bridge (SAB) and dual-active bridge (DAB) converter modules are combined in the proposed structure: the unidirectional SABs process most of the forward power, while the bidirectional DABs provide passage for the backward power flow. A string of embedded nonisolated resonant dual active bridge (NRDAB) converters is constructed at the input stage to realize natural power coupling and voltage sharing. Compared with the all-DAB ISOP scheme, the proposed one requires fewer devices and presents higher conversion efficiency as active switches are omitted at the secondary side of SABs. Experiments conducted on the downscale prototype verify the operating principles and performance of the proposed converter.

This paper proposes a novel position identification algorithm for permanent magnet synchronous motors (PMSMs) operating at zero and low speed. Traditional high-frequency signal injection methods struggle with phase lag and poor interference rejection, limiting their effectiveness in steady and dynamic conditions. To overcome these challenges, an improved nonlinear tracking differentiator method for precise and rapid estimation of motor position and speed is presented. The proposed method reduces tracking delay by 35% and improves noise immunity by 30% compared to traditional methods. Advanced mathematical analysis and frequency sweep tests validate its effectiveness. Simulation and experimental results confirm enhanced performance in both steady and dynamic states, with the method effectively suppressing 6 ^th -order harmonic interference from inverter nonlinearity, achieving an attenuation of -43 dB/decade.

This article proposes an axial-field permanent magnet (AFPM) machine topology, in which two stators with splitting teeth and a rotor with N-iron PM arrangement are included. Specifically designed for direct-drive electric vehicle (EV) applications, this machine boasts a compact structure and high torque density. This paper comprehensively outlines the topology and operation principles governing the AFFMPM machine, with a focused exploration of its evolution process from the axial-field magnetic gear. Utilizing the three-dimensional finite element method (3D FEM), the proposed AFPM machine's electromagnetic characteristics are demonstrated. The results reveal a remarkable enhancement compared to the baseline AFPM model, achieving a 108% increase in torque and a 166% improvement in torque/PM volume. The AFPM prototype is constructed and experimented to confirm the analysis.