Series-end winding motor drives (SWMDs) are more well known for the characteristics of high dc-link voltage utilization and controllable zero-sequence loop. Besides, SWMDs also have the potential ability to reduce the leg-current stress (LCS) by rearranging the winding-connection sequence (WCS), especially in multiphase SWMDs (MP-SWMDs). Yet, this characteristic is not widely noticed in the existing works. To this end, this article presents the analysis of WCS in MP-SWMDs for LCS reduction, which provides the possibility to improve the load capability and reliability compared with the existing WCS. Based on the phasor diagrams of the leg- and phase-currents, the principle of the WCS in MP-SWMDs for LCS reduction is revealed, which is discussed separately for the symmetrical and asymmetrical (multiple three-phase) phase-windings. By rearranging the WCS and reversing part of windings in MP-SWMDs, optimal WCSs for LCS reduction are derived accordingly. Subsequently, the corresponding modulation schemes based on the relative potential are developed. Moreover, the linear modulation ranges of different WCSs in MP-SWMDs are also investigated. With the verification of the experimental results, the current amplitude of middle legs in MP-SWMDs under the optimal WCS for LCS reduction can be reduced significantly compared with the star-connected winding counterparts. Simultaneously, the linear modulation range is also reduced, which indicates that MP-SWMDs under the optimal WCS for LCS reduction are ideal for low- or medium-speed motor drives with heavy load.

Series Elastic Actuator-based exoskeleton can offer precise torque control and transparency when interacting with human wearers. Accurate control of SEA-produced torques ensures the wearer’s voluntary motion and supports the implementation of multiple assistive paradigms. In this paper, a novel variable transmission series elastic actuator (VTSEA) is developed to meet torque-speed requirements in different exoskeleton-assisted locomotion modes, such as running, walking, sit-to-stand, and stand-to-sit. The VTSEA features a SEA-coupled variable transmission ratio adjusting mechanism and works between three discrete levels of transmission ratio depending on the user’s initiative. The proposed prototype can also improve transparency in human-robot interaction. Also, an accurate torque controller with inertial compensation is developed for the VTSEA via the singular perturbation theory, and its stability is proved. The feasibility of the proposed VTSEA prototype and the precise output torque performance of VTSEA are verified by experiments.

Power factor correction (PFC) converters with a diode bridge are extensively used in different AC-DC applications. However, the diode bridge has to employ four diodes to complete the AC to DC at the expense of high conduction losses. Thus, many bridgeless PFC converters have been proposed with dual converter cells to minimize the number of conducted diodes for better efficiency. Unfortunately, these dual-converter cell-based bridgeless converters need almost double components. To solve this issue, this paper proposes a true bridgeless buck-type PFC converter, which annihilates the diode bridge completely with only fewer component counts. The proposed converter uses buck and buck-boost cells to obtain the novel bridgeless topology, which features a simple structure and control to achieve high PF and low total harmonics of input current (THDi). Simulations are given to validate the feasibility of the proposed topology and the control method. Comparisons with the conventional buck PFC converter are also given to confirm the better performances of the proposed topology.

Electric vehicles (EVs) can act as virtual energy routers (VERs) in the grid, giving them the flexibility to change the direction of energy flow. Therefore, a day-ahead scheduling for radial microgrids deploying EV-based VERs is proposed. In the day-ahead scheduling, the charging/discharging operation, state of charge (SOC), and available time of EV-based VERs are involved in the social utility maximization problem. With the laxity model of EV-based VERs and the forecasted reference demand, the supply and demand in the microgrid are optimized to minimize generation costs and maximize consumer utility in a whole day. Binary variables, which indicate the charging and discharging choices of the EV-based VERs, exist in the day-ahead scheduling. Therefore, mixed integer nonlinear programming (MINLP) is adopted to solve the optimization problem. The simulation cases are then provided to verify the effectiveness of the suggested day-ahead scheduling approach.

Axial-flux permanent magnet (AFPM) machines are welcomed widely in many applications thanks to the high torque density and compactness. In the AFPM machine, the concentrated winding and distributed winding have different characteristics. In order to increase the winding factor and reduce the winding ends, a novel concentric winding AFPM machine is proposed in the paper. The stator of the proposed machine is divided into three circles from the inner side to the outer side. Then, the three-phase windings are arranged on the three circles, respectively. The phase angle difference is achieved through the mechanical offset between the teeth of three circles. Thus, the winding factor can be kept as 1 with a few winding ends by adjusting the pole-slot combination. In addition, the staggered teeth between the three circles can also reduce the cogging torque. In the optimization, the back EMFs of the three phases are nearly balanced. 3D finite element analysis also shows that the machine has a strong overload capability.

In recent years, transverse flux permanent magnet motors (TFPMMs) have had a promising application in electric propulsion systems due to their modularity, simple winding distribution, and high reliability. However, the low motor space utilization, low average output torque, and complex manufacturing and assembly constraints have limited the further development of TFPMMs. Therefore, this paper proposes a novel double-stator transverse flux reversal permanent magnet machine (DS-TFRPMM). This new motor has no permanent magnets on the rotor and can achieve higher operating speeds. In addition, the permanent magnets are on the outer stator to improve motor space utilization. Firstly, this paper describes the structure and operating principle of the DS-TFRPMM. A 3D model of the DS-TFRPMM is then constructed, and a 3D-finite element analysis (FEA) is carried out to obtain the magnetic field distribution and the critical performance data. The simulation results show that the proposed motor has the average output torque of 11.70Nm, the torque density of 10.9Nm/L, and the 1.19Nm peak-peak value of cogging torque. Finally, the paper optimizes some critical parameters of the DS-TFRPMM and provides the dimensions of the vital motor components for optimum output performance.

Dual-motor synchronization driving system is widely applied in electrified transportation tools and other industrial fields. This paper proposes a novel dual-motor synchronization drive method combining classical cross-coupled and electronic virtual line shafting (EVLS) control. The improved cross-coupled structure adopting adaptive gain feeds back speed synchronization error to modify speed reference. A virtual shaft is designed to resist disturbance and enhance the robustness of system. Besides, model predictive torque control (MPTC) is employed to further improve the dynamic response. Finally, a simulation model is established to verify the effectiveness of proposed dual-motor control strategy. The test results indicate that the system has fast dynamic response and good synchronization precision.

This paper provides a preliminary study of promoting the direct torque control (DTC) to series-end winding permanent magnet synchronous motor (SW-PMSM) drives. The DTC schemes of the conventional PMSM drives cannot be directly applied to the SW-PMSM drives since they have different drive topologies. With one more leg added to the inverter, the SW-PMSM drive has a different voltage vector distribution, which leads to a different switching table for the hysteresis controllers of the flux and the torque. In addition, the zero-sequence subspace also exists in the SW-PMSM drive, and it might generate the undesired zero-sequence current. Based on the above issues, the voltage vector distribution of the SW-PMSM drive is studied in this paper, and the voltage vectors without zero-sequence components are selected as the candidates to prevent generating zero-sequence current. Next, the switching table for the hysteresis controllers is re-derived according to the candidate voltage vectors, and the DTC for the SW-PMSM drive is obtained. Subsequently, the DTC of the multi-phase SW-PMSM drive is also investigated in the same manner. Finally, the effectiveness of the proposed DTC schemes for the SW-PMSM drives is verified.