This paper proposes and implements a full-range soft-switching pulse frequency modulated (PFM) wireless power transfer (WPT) system, which not only offers high efficiency but also high controllability, selectivity and security. Although the phase-shift control (PSC) has been widely used in various WPT applications, the high-frequency hard-switching operation will inevitably degrade the system performances in terms of power losses and hence efficiency during power regulation. Thus, a soft-switching PFM is newly conceived to suppress the switching frequency and power losses while maintaining full-range soft-switching for effective power control, hence improving the system efficiency. In addition to realizing the controllability, the full-range soft-switching PFM can be further derived to implement the selectivity and security. The system efficiency of a multi-objective PFM-WPT system prototype can reach 86.27% at 220-W output power and 135-mm transfer distance. During wireless power control, it can effectively be improved by up to 5.68% as compared with its counterpart using the PSC. Theoretical analysis, computer simulation and hardware experimentation are given to verify the feasibility of proposed full-range soft-switching PFM-WPT system.

Traditionally, domestic induction heating (IH) is designed to heat the ferromagnetic (FM) pan. However, it is incompetent to heat the non-FM (NFM) pan since the small equivalent resistance of the pan will easily result in overcurrent on the inverter. Inspired by the compensation network in the wireless power transfer (WPT), the series–parallel resonance (SPR) network with a relay switch is newly integrated into the IH technology to develop a dual-resonant topology-reconfigurable inverter for all-metal IH. The proposed system can be purposely configured to a half-bridge series resonant inverter with the pulse width modulation (PWM) to heat the FM pan, or a full-bridge SPR-based inverter with the phase shift control (PSC) to heat the NFM pan, respectively. Moreover, the output–input current gain of the SPR network equals the heating-coil quality factor, thereby readily eliminating the overcurrent issue of the inverter. For exemplification, a 1-kW prototype has been built with system efficiencies of 94.32% and 91.05% for heating FM and NFM pans, respectively. Finally, the proposed system can be evolved to achieve automatic load detection and impedance matching to ensure uninterrupted resonance. Both the calculated and measured results are given to validate the flexibility and feasibility of the proposed system.

This article proposes and implements a hybrid frequency pacing (HFP) technique for resonating a high-order transformed wireless power transfer (WPT) system with robust zero-voltage switching (ZVS). As a hybrid frequency modulation, the proposed HFP can efficiently tune the innate constant-frequency resonances of WPT. It can facilitate the pulsewidth modulated inverters to totally get rid of the high-frequency hard-switching while reducing the switching frequency and improving the system efficiency. For typical low-order boost WPT-based scenarios, the rectification effect may cause waveform distortions and involve a very low virtual capacitance, thus leading to great degradations on the ZVS and zero-phase-angle operation. In addition to achieve a load-independent constant voltage/current output, a high-order LCC network is deeply investigated to act as two-stage impedance transformations. By flexibly utilizing the rectification-caused virtual derivatives with the high-order transformations, it reliably contributes to a robust ZVS-HFP. The experimental system efficiency can be more than 91.5% with the full-range ZVS operation. Theoretical analysis and experimental results are both provided to verify the feasibility of the proposed ZVS-HFP for tuning the high-order LCC-transformed WPT system.

In this article, a wireless resolver is proposed and implemented for wireless switched reluctance (SR) motors, which can detect the rotor position and transfer the information to the primary side without involving any battery storage or active components at the secondary side. The key is to integrate wireless power transfer (WPT) into a variable reluctance resolver to detect and transmit the rotor position. Compared with previous wireless SR motors adopting the Hall effect position encoder and Bluetooth communication, the robustness is highly improved, and the communication delay caused by the connection interval can be solved. Therefore, the proposed system takes the definite advantages of better dynamic performance and sealability. Besides, there is no need to specially design the SR motor, as all existing SR motors and other similar kinds of motors can readily employ this wireless resolver. An experimental prototype has been built for verification, which works well from 100 to 900 rpm with 20 mm WPT distance, and the additional power for position detection can be limited to 1.05 W while the motor consumes 54 W.

This article proposes and implements an optimized omnidirectional wireless power transfer (WPT) system using distributed transmitter coils. Under the consideration of practical WPT applications which involve human safety concerns, such as daily home apparatus or wireless rechargeable medical implants, the proposed system can achieve the shortest charging time within the safe limits of human exposure to radiofrequency electromagnetic energy. Based on the calculation of the magnetic intensity generated by multicoupling WPT systems, a more processable magnetic threshold model is presented and analyzed based on the common standard. A newly developed optimization model of the transmitter currents and accordant control strategy is designed and presented to realize both maximum power tracking and flux suppression at target positions. The double-resonant circuit topology with LCC compensation is adopted to reach the stable and synchronized transmitter currents. The cross-coupling problem in multiinput WPT systems will be solved as well. Full-range magnitude control is realized with a single controller and direct current (dc) power supply. The hybrid frequency pacing technique is adopted for lower switching frequency and higher system efficiency under weak coupling operations. Taking practical wireless rechargeable medical implant as the research object, both simulation and experimental results validate the feasibility and the prospect of the proposed system.