Aiming at the problems of limited semiconductor performance and positioning difficulties in the wireless power transfer (WPT) system of electric vehicles, the paper proposes a many-to-one high-voltage wireless charging anti-offset system. In order to be adapted to high-voltage applications, the system is designed with a series input inverter. At the same time, a multi-winding transformer is used to realize the equivalent parallel output of inverters and the function of transmitting power to primary loops. The many-to-one topology aims to expand the positioning range of electric vehicles to realize the anti-offset of wireless charging. In order to analyze the working mechanism of the multi-winding transformer and study the power transmission characteristics of the many-to-one topology, the equivalent circuit analysis and Matlab simulation are carried out, and a laboratory prototype for experimental verification is made. Based on the experimental and simulation results, the paper proposes a hybrid operating mode based on many-to-one WPT topology, which can effectively expand the positioning range of electric vehicles during wireless charging. Both the analytical and experimental results show that the topology proposed in the paper can effectively increase the input voltage of the system for high-voltage scenarios, and effectively expand the positioning range of the WPT system.

To shorten the cooling time of the superconducting rotor, reduce the thermal leakage of the cold mass, enhance the working stability of high-temperature superconducting (HTS) magnets, and reduce the amount of HTS wires, a novel warm rotor for a 200 kW HTS generator (HTSG) with radial support rods, tangential racetrack rings, and modular HTS magnets was successfully developed. There are 12 HTS magnets in 6 poles of the HTSG, all of which can work stably without quench, and the performance of the magnets meets the expectation. The vacuum, thermal insulation, and cryogenic systems of the generator run stably, which meet the needs of continuous operation at full load. The manufactured warm rotor and the original iron-core stator of the existing 200 kW HTSG were assembled into a new 200 kW HTSG, the assembly process was completed at Wuhan, and then finished the performance test. The test results show that the output power of the HTSG reaches 203.4 kW and the torque reaches 3885 N.m when the field current reaches 24 A and the speed is 500 r/min, which achieved the target power.

With the continuous advancement of science and technology, the application of high-temperature superconductivity has developed rapidly. The high-temperature superconducting (HTS) motor replacing the copper coil in the traditional motor with HTS winding is increasingly used in power equipment, and the effective thermal management of HTS winding is vital in ensuring the life and effective operation of the HTS motor. In this study, five enhancement structures of indirect oil cooling channels were designed to improve the heat dissipation capacity of the HTS motor winding, and the enhancement effects of the different structures were comprehensively evaluated through numerical simulation using Fluent software 2022R1. The best enhancement structure was selected through structural optimization. The results showed that the Nusselt number of the gap-type enhanced structure was higher than that of the V- and staggered-type structures at the same flow velocity and 68% higher than that of the bare pipe. At the same inlet flow velocity and with a pressure drop limit of 30 kPa, the performance evaluation criterion value of the gap-type structure was 39% and 63% higher than that of the staggered- and V-type structures, respectively. The gap type is the optimal enhancement structure and can effectively improve the heat dissipation of the HTS winding coil.

Temperature rise determines the lifetime of the motor. Wuhan Institute of Marine Electric Propulsion has conceptualized and designed a 20 MW high-temperature superconducting motor (HTSM) with an oil-cooling air-core stator and a superconducting rotor. This paper describes the design and analysis process of the cooling system of this stator: Firstly, We simplified the full structure of the HTSM and established the model of the oil-cooling air-core stator for thermal analysis. Second, We analyzed and compared the cooling effect of different oil inlet forms under different thermal loads and coolant flow, and sequentially determined the optimized inlet form. The analysis results show that the average and maximum temperature of the oil and coil increase with a higher thermal load, or a smaller oil flow. Underrated operating conditions (240 kW@60 m3/h), the maximum temperature of the coil is 72 °C, and the maximum temperature of the cooling oil is 65 °C, meeting the temperature rise requirement. Finally, we present a structural solution for a compact oil-cooled air-core stator that can increase the torque density of the HTSM.

In this paper, a parallel modular multi-inverter (PMMI) topology is proposed to supply high power for wireless charging electric vehicles (EVs). A major challenge in the implementation of PMMI topology is zero-voltage switching (ZVS) for all inverters to avoid high-frequency switching losses. Therefore, a centralized-ZVS control and master–slave frequency following (MSFF) strategy are presented to realize ZVS for all PMMIs by a single controller structure without extra controllers needed on the slave inverters. Meanwhile, a modeling method directly related to the ZVS angle and operating frequency for an arbitrary number of PMMIs is proposed and linearized to analyze the system dynamic characteristics at the operating point. Additionally, to obtain the desired dynamic performance, an optimal controller coefficient (OCC) configuration method is proposed for the design of controller parameters. Finally, a laboratory wireless power transfer (WPT) prototype supplied by three PMMIs is designed, built, and tested to verify the correctness of the theoretical analysis. Experimental results show that the ZVS angle of all PMMIs can maintain at the preset value with the desired settling time under designed the PI controller parameters. The measured whole system power transmission efficiency is $94.1\%$ at a 10 $\mathsf{\Omega }$ load.