Electric vehicles (EVs) are becoming increasingly popular as a means of future transport for sustainable living. However, wireless charging of EVs poses a number of challenges related to interoperability, safety, pad misalignment, etc. In particular, pad misalignments invariably cause changes in system parameters which in turn lead to increase in losses as well as reduction in power throughput, making the charging process long and inefficient. Consequently, wireless charging systems that are less sensitive to pad misalignments have become preferable. This paper, therefore, presents a hybrid wireless power transfer (WPT) system that charges EVs at constant rate despite large misalignments between charging pads. The proposed charging system uses a combination of two different resonant networks to realize a constant and efficient charging process. A mathematical model is also developed, showing as to how the two resonant networks can be combined to compensate for pad misalignments. To demonstrate the validity of the proposed concept as well as the accuracy of the mathematical model, theoretical performance is compared with both simulations and experimental results of a prototype 3.3 kW hybrid bidirectional WPT system. Results clearly indicate that the proposed hybrid WPT system is efficient and offers a constant charging profile over a wide range of spatial (three-dimensional) pad misalignments.

Electric vehicles (EVs) are becoming increasingly popular as a mean of mitigating issues associated with fossil fuel consumption in transportation systems. A wireless inductive power transfer (IPT) interface between EV and the utility grid has several key advantages, such as safety, convenience, and isolation. However, physical misalignments between the pads of IPT charging systems used in EVs are unavoidable and cause variations in key system parameters, significantly increasing losses and affecting power throughput. This paper presents a novel series-hybrid topology in which the series inductors of the primary and pick-up LCL networks are integrated into polarized magnetic couplers to improve the system performance under pad misalignment. A mathematical model is developed to investigate the behavior of the proposed system under misalignment. To demonstrate the viability of the proposed method, the results of a 3.3 kW prototype series-hybrid IPT system are presented, benched marked against a conventional IPT system. Experimental results clearly indicate that the proposed system maintains the output power within μ5% of its rated power despite the pad misalignment. The proposed system is efficient, reliable and cost-effective in comparison to conventional LCL and CL compensated IPT systems.systems.

This letter proposes a dual-frequency tuning method for improved coupling tolerance of an inductively coupled wireless power transfer (WPT) system by exploiting the fundamental and 3rd order harmonic components of a square-wave voltage out of a full-bridge inverter. A dual-frequency hybrid compensation topology is designed to simultaneously utilize the characteristics of series-series (SS) and LCL-S networks under the two different frequencies. Consequently, the output power of the proposed system under a fixed load is maintained approximately constant against coupling variations. A practical hybrid WPT system with a 100 kHz square-wave excitation and a 10.5 $\Omega$ resistive load is built to verify the theoretical modelling and analysis. Experimental results show that the system achieves an approximately constant output voltage and power of around 39 V and 150 W against a coupling coefficient variation from 0.52 to 0.72, with maximum fluctuations less than 5% and 10%, respectively.

Inductive power transfer and capacitive power transfer (CPT) are two of the most commonly used near-field wireless power transfer technologies, and these two systems share similarities and symmetries. This article proposes a hybrid wireless power transfer (HWPT) system to achieve load-independent characteristic and anti-misalignment capability. The HWPT system utilizes the compensation inductors of the CPT system to create an additional inductive channel in which the capacitive and inductive channels are compensated for each other. Based on the modeling of the HWPT system, the load-independent and enhanced constant current output is derived. In HWPT system, the inductive coupler is employed with the capacitive coupler, which forms a compact hybrid coupler. As the coupler becomes misaligned, the loss of power transferred through the inductive channel can be compensated by the increase of power transferred through the capacitive channel. A 200 W experimental prototype is built to validate the performance of the HWPT system. Experimental results show that as the load resistance ranges from 20 to 40 $\Omega$ and the coupling misalignment ranges from 0 to 100 mm, the output current remains nearly constant and the input current stays in phase with the input voltage. According to the experimental findings, the output current of the HWPT system is approximately twice as high as that of the CPT system when using the same capacitive coupler.

In magnetic coupling wireless power transfer systems, air gap and load changes are very common. Due to the presence of ferrite cores, changes in the air gap can lead to variations in coil parameters (mutual inductance and self-inductances), particularly in small air gap applications. This article proposes a constant current (CC) output method for LCC-LCC compensated WPT system with variable parameters. The proposed method utilizes an integrated magnetic coupler to provide a variable compensation inductance to offset output fluctuations caused by mutual inductance changes. In addition, compensation parameters for maintaining a CC output versus air gap and load changes are obtained through a particle swarm optimization (PSO) algorithm. An 800 W experimental setup is constructed to validate the effectiveness of the proposed method. The experimental results show that, when the output power varies from 400 to 800 W, within the air gap range of 15 to 50 mm, with a maximum self-inductance variation range of 23% and a maximum coupling coefficient variation range of 0.71 to 0.32, the system has a CC output characteristic with a maximum current fluctuation of only 4% and a maximum efficiency of 90.8%. A video demonstrating the variations in system key waveforms during air gap changes is attached to this article.

This letter proposes a dual-frequency-detuning method for wireless power transfer systems to gain a smooth power profile in large coupling variation ranges. The application of the detuning method in the dual-frequency resonant network is explored to adjust the equivalent impedance of each frequency channel at different coupling conditions. Accordingly, the proposed method can freely regulate the voltage gain and output power curves even under a square-wave voltage excitation with high-order harmonic components. By designing the system properly, both the fundamental and 3 ^rd frequency channels alternately serve as the main power transfer channel under strong and weak coupling conditions, so less power fluctuation over a large coupling variation is realized. A 130W prototype is developed, and the experimental results show that the maximum power fluctuation is less than 6.8% against coupling coefficient variations from 0.35 to 0.74.