Resonant Coupling Wireless Power Transmission Research Articles

Wireless power transfer system based on frequency and impedance matching hybrid adjustment against system detuning

System detuning caused by a variation in the distance between the transmitting and receiving terminals can greatly reduce the transmission power and efficiency of a magnetic resonance-coupled wireless power transmission (WPT) system, which limits the WPT application scope. This paper proposes a magnetic resonance coupling wireless power transmission system, which is based on jointly and continuously adjustable frequency compensation (CAFC) and two-transistor-controlled variable capacitor circuits (TCVCs). Therefore, this system can reach the resonant state by using CAFC and two-TCVCs when the transmission distance is changed. The proposed system can adaptively adjust combinations of the operating frequency and equivalent compensation capacitor’s capacitance to achieve impedance matching avoiding the phase difference caused by the imaginary part of the impedance, thus maintaining stable transmission efficiency under the condition of transmission distance variation. Compared to the traditional magnetic coupled resonant circuit based on impedance matching or variable resonant frequency, the proposed system achieves higher efficiency and stability and dynamic distance adaptation.

Design and Experiment of a Reconfigurable Magnetic Resonance Coupling Wireless Power Transmission System

Magnetic resonance coupling wireless power transmission (WPT) provides a safe and efficient power supply for small household appliances and implanted devices, but the tolerance of the transmission distance is poor. To improve the robustness of the transmission distance of the magnetic resonance WPT system, a method of using a reconfigurable helical coil array is proposed. Compared with the traditional four-coil structure of the same volume, different source and load coils are selected under distinct distance conditions. The coupling coefficient between the coils is changed to increase the stability of transmission efficiency and distance. To avoid the mechanical movement, all source and load coils have been adjusted at fixed position. Moreover, a control method is introduced to achieve coil switching. The experimental results show that the transmission distance of the proposed system is increased to 1.75 times of the coil diameter, while the efficiency remains above 70%.

Numerical and Experimental Study on Design Optimization of Hybrid Metamaterial Slab for Wireless Power Transmission

Wireless power transmission (WPT) technique has advanced rapidly in the past two decades. For wireless power transmission distances from 40 to 200 mm, the resonance coupling WPT (R-WPT) technique has surpassed its original inductive coupling counterpart in terms of transmission efficiency. Nevertheless, the power transfer efficiency of a R-WPT system is still lower than that of a wired power transfer system. To increase the power transfer efficiency of a R-WPT system, metamaterial (MM) slabs are inserted between the transmitter and receiver. Moreover, it has recently been validated that a hybrid MM (HMM) slab with different resonance frequency unit cells behaves better than a homogeneous MM slab with identical resonance frequency unit cells in a R-WPT application. However, in the existing HMM slab designs for WPT applications, a trial and error approach, is commonly used to decide the physical and circuit parameters of the HMM slab due to the overwhelmingly high computational cost of numerical simulations using three-dimensional (3-D) finite element method. To overcome the deficiencies of the existing designing methodology and to fully automate the design process, a design-of-experiment (DOE) assisted sequential refinement methodology is proposed by introducing an adaptive surrogate model with tabu search method, for design optimizations of HMM slabs in R-WPT applications. Compared with the existing refinement searching procedures, the salient feature of the proposed one is its bi-directional characteristics, which can refine the searches in the promising sub spaces by intensifying sampling points; and use coarse searches or even discarding the exploitations in the worst sub spaces using some adaptive upper and lower limits of the decision parameters. To validate the feasibility and show the advantages of the proposed methodology, detailed numerical and experimental studies on a case study of a four-coil WPT system working at 13.88 MHz are conducted, and the results have shown that the HMM slab optimized by using the proposed methodology does have better performance in WPT applications when compared to its homogenous counterparts.

Compensating Resonant Frequency via Adjusting Adjustable Coil Automatically

Background: Detuning is the main problem that affects the efficiency and transmission distance of the resonant coupling Wireless Power Transmission (WPT). The distance of load and the offset of the load position could cause serious detuning. Methods: This paper presents an adjustable coil in which inductance can be adjusted. Then a model of WPT was established that could compensate resonant frequency automatically using the adjustable coil. Next, the relationship between the primary resonant frequency and the transmission efficiency is analyzed from the circuit. The analysis proved that the design of the adjustable coil could improve the transmission efficiency of the WPT system. Finally, a prototype of WPT system was built. Results: The experimental results showed that WPT system with adjustable coil can improve the transmission efficiency which proves the theoretical research. At the same time, it has essential reference value for the future research of WPT. Conclusion: In this paper, aiming at the system detuning caused by some other factors, such as the position shift of the load during the wireless power transmission, an adjustable coil is proposed.

Research on impedance matching method for magnetic resonant coupling wireless power transmission system

Research on impedance matching method for magnetic resonant coupling wireless power transmission system

Research on the wireless power transmission technology based on maximum energy efficiency tracking under dynamic distance

Focusing on the maximum efficiency of magnetic resonant coupling wireless power transmission, this paper analyzes circuits by use of lumped parameter models, deduces the relationship between the maximum energy efficiency and the duty cycle of the inverter at the transmitting terminal, and proposes a self-adaptive control technique to ensure that the wireless power transmission system maintains the maximum energy efficiency when the transmission distance changes; the effectiveness and feasibility of this method is verified with a hardware platform.

Parameters optimization for magnetic resonance coupling wireless power transmission.

Taking maximum power transmission and power stable transmission as research objectives, optimal design for the wireless power transmission system based on magnetic resonance coupling is carried out in this paper. Firstly, based on the mutual coupling model, mathematical expressions of optimal coupling coefficients for the maximum power transmission target are deduced. Whereafter, methods of enhancing power transmission stability based on parameters optimal design are investigated. It is found that the sensitivity of the load power to the transmission parameters can be reduced and the power transmission stability can be enhanced by improving the system resonance frequency or coupling coefficient between the driving/pick-up coil and the transmission/receiving coil. Experiment results are well conformed to the theoretical analysis conclusions.

Numerical Analysis on Transmission Efficiency of Evanescent Resonant Coupling Wireless Power Transfer System

A practical wireless power transmission system consisting of a large rectangular wire loop and a small square wire loop with a parasitic square helical coil is proposed for use as an efficient evanescent resonant coupling wireless power transmission system in an indoor environment. In addition, a full wave-based numerical analysis on the resonant frequency of and the power transmission efficiency of wireless power transmission system are performed in this paper. The effects of the following on power transmission efficiency and the resonant frequency are numerically investigated: The load of the receiving element and the presence of non-resonant objects such as a conducting box or human body. The numerical results show that a power transmission efficiency of nearly 50% can be achieved when the proposed system is used to charge only one user with the optimized load. The results also show that power transmission efficiency is reduced significantly when a human body is in very close proximity to the receiving element. This reduction in efficiency can be alleviated significantly, however, if the relative distance between the receiving element and the human body is greater than 0.5 m or 0.03? at a resonant frequency of 19.22 MHz.