Transportation electrification has attracted much attention in modern society. Among all electrified transportation tools, electric vehicle (EV) is absolutely the one that has great potential to compete with and further take the place of traditional fossil fuel vehicles. This article is to outline and investigate advanced electric machines and their control strategies for EV applications. The key is not only to reveal new design ideas, topologies, structures, methodologies, control strategies, pros and cons, and foresight for advanced electric machines but also to fully integrate these ideas into practical EV applications. This critical review will clarify the development trends of electric machines and their controls.

Unmanned Aerial Vehicle (UAV) propulsion technology is significantly related to the flight performance of UAVs, which has become one of the most important development directions of aviation. It should be noted that UAVs have three types of propulsion systems, namely the fuel, hybrid fuel-electric, and pure electric, respectively. This paper presents and discusses the classification, working principles, characteristics, and critical technologies of these three types of propulsion systems. It is helpful to establish the development framework of the UAV propulsion system and provide the essential information on electric propulsion UAVs. Additionally, future technologies and development, including the high-power density motors, converters, power supplies, are discussed for the electric propulsion UAVs. In the near future, the electric propulsion system would be widely used in UAVs. The high-power density system would become the development trend of electric UAVs. Thus, this review article provides comprehensive views and multiple comparisons of propulsion systems for UAVs.

With the increasing requirements and demands for electric machines in various applications, axial-flux machines (AFMs) attract more and more attention in recent years because of their unique merits of high power density, compact structure, and high material utilization. This article mainly investigates the topologies of AFMs and corresponding modeling methods. In general, AFMs can be classified according to different criteria. One classification is based on the machine configuration, and another one is based on their operational principles. The first classification discusses the characteristics of single-side AFMs, double-side AFMs, and multidisk AFMs. The second classification discusses the characteristics of conventional AFMs and emerging AFMs. As for the modeling methods, this article summarizes finite-element methods (FEMs) and analytical methods in detail. Based on these investigations, the article can provide the guidance and foresights for the design and analysis of AFMs.

High-performance propulsion motors for more electric aircrafts (MEAs) are highly appreciated in transportation electrification. For the widely adopted permanent magnet synchronous machines (PMSMs) for MEA propulsion, the segmented Halbach magnetization has distinct merit that it contributes to sinusoidal air-gap magnetic fields for smooth operation. However, it is hard to fast predict the field distribution and machine performance due to the model complexity. Based on the subdomain method, this paper first proposes an exact analytical model for slotless PMSM with segmented Halbach PMs. Then, the model is applied in the fast computation of magnetic field and performance prediction. Subsequently, the analytical results are compared with the finite element method (FEM), including the flux density, flux linkage, induced voltage, and steady-state torque at different loads. Also, the computation burden and prediction error are included to validate the model rapidity and accuracy. Finally, by prototype fabrication and unique field measurement methods, the flux density distribution is originally validated.

Through the zero-sequence current (ZSC) hysteresis controller, the existing ZSC hysteresis control-based space vector modulation (SVM) strategy can provide a satisfactory ZSC suppression effect and greatly reduce the complexity for the open-end winding permanent magnet synchronous machine (OW-PMSM) drive with common dc bus. However, the corresponding linear modulation range is reduced by 12.7% compared with the middle hexagon space vector modulation (MH-SVM) for the OW-PMSM drive. To this end, this letter improves the linear modulation range of the existing strategy. The candidate voltage vectors for each sector are re-selected, and three active voltage vectors will be employed in the extended feasible region. While ensuring the ZSC hysteresis control, the linear modulation range of the proposed strategy is the same as the MH-SVM. At last, experimental results verify the feasibility and effectiveness of the proposed strategy. The proposed strategy can suppress the ZSC effectively, and the corresponding maximum speed is the same as the counterpart of the MH-SVM.

Harmonic currents always exist in a dual three-phase permanent magnet synchronous machine due to the inverter nonlinearity, nonsinusoidal back-electromotive force, and external disturbances. This article proposes a deadbeat predictive harmonic current control (DPHCC) method to suppress the harmonic currents. The DPHCC method can directly calculate the harmonic control voltage based on the sampled harmonic currents and the machine model. Thus, the steady-state and transient-state performance of harmonic current control can be improved. Further, a disturbance observer is designed to avoid the influence of inaccurate machine parameters and other unmodeled disturbances. The observer is designed based on discrete-time sliding mode theory and an improved sliding mode reaching law. The stability of the observer has been analyzed, and the value range of the observer parameters has been determined theoretically. Finally, experimental results have been presented to verify the effectiveness of harmonic current suppression for the proposed control system.