Model Of Wireless Power Transfer System Research Articles

Wireless Power Transfer System Model Reduction with Split Frequency Matching

Reduced-order dynamic models of wireless power transfer (WPT) systems are desired to simplify the analysis and design of power control, phase synchronization, and maximum efficiency tracking. The reduced-order dynamic phasor model is a good choice because of its straightforward physical meaning and concise mathematical formula. However, the model relies on the assumption of loose coupling and loses accuracy when the coupling becomes stronger. In this paper, a model reduction method with split frequency matching is proposed to improve model accuracy under relatively strong coupling conditions, which is suitable for most short-distance WPT applications, such as wireless electrical vehicle charging. Split frequency matching is achieved through a pair of conjugate equivalent mutual inductances, which are derived from the asymmetry characteristics of the full-order dynamic phasor model in the positive and negative frequency domains. The proposed model retains the advantages of the existing model while significantly improving the accuracy under strong coupling conditions. Its characteristics are verified by comparing the experimental results and model predictions under both large step changes and small-signal perturbations.

Research on Wireless Power Transfer Method for Intelligent Sensing Device of Non-Directly Buried Distribution Cables

This paper presents a study on the impact of circuit parameters on the transmission of electrical energy in wireless power transfer systems designed for intelligent sensing devices within the urban electric power Internet of Things (IoT). Relying on the essential principles of resonant mutual inductance models, the paper conducts an analytical investigation into the phenomena of power-frequency splitting characteristics, efficiency-frequency splitting characteristics, and efficacy synchronization characteristics within wireless energy transmission technologies. The investigation includes a detailed analysis of a wireless power transfer system model operating at 100 kHz, delineating how varying circuit parameters influence the system’s efficiency. Via the utilization of graphical software and computational programming for simulation modeling, this research delved into the dynamics between key parameters such as equivalent load and coupling coefficient and their influence on distinct splitting phenomena. This rigorous approach substantiated the validity of the proposed power-frequency and efficiency-frequency splitting characteristics outlined in the study. Based on the analytical results, it is shown that selecting an appropriate equivalent load or utilizing impedance matching networks to adjust the equivalent load to a suitable size is crucial in consideration of the system’s output power, voltage withstand level, and transmission efficiency. The research findings provide a theoretical basis for the design of wireless power supply systems for non-directly buried cable front-end sensing devices.

C2DD—An omnidirectional receiver based on single‐coil transmitter

AbstractIn this paper, the omnidirectional receiver (Rx) of wireless power transfer (WPT) system is proposed, making any transmitter (Tx) into omnidirectional Tx. The omnidirectional Rx is composed of the quadrature double‐D (DD) coils and circular coil in series (C2DD). The C2DD Rx can utilize the toroidal magnetic field (TMF) and the linear magnetic field (LMF). The paper presents the circuit diagram model of WPT system. Based on the analysis of circuit model, the smooth mutual inductance of system is responsible for stable transmission performance during C2DD Rx movement. The result of numerical calculation and magnetic field simulation verifies the omnidirectional capability of the C2DD Rx with circular Tx as an example. Experiment shows that the C2DD Rx receives power in any direction. The C2DD Rx can receive maximum transmission power of 7.1 W with maximum transmission efficiency of 59%.

Analysis of the Influence of the Skin Effect on the Efficiency and Power of the Receiver in the Periodic WPT System

The article shows an analysis of the influence of the skin effect on the maximum efficiency and maximum power of a receiver in a wireless power transfer system (WPT). For this purpose, the original solution of the WPT system was used, which contained periodically arranged planar coils. The results concern the multi-variant analysis of the WPT system. The geometry of the coils was taken into account, i.e., the size of coils, the number of turns, as well as the distance between the transmitting and receiving coils. The calculations were carried out over the frequency range of 0.1–1 MHz. In order to analyse the influence of the skin effect on the proposed WPT system, two approaches were used: analytical and numerical. The article analyses the appropriate selection of load impedance in order to obtain maximum efficiency or maximum power of the receiver. In this analysis, the influence of the skin effect on each of the two operating procedures was examined. The obtained analytical and numerical results differed by no more than 0.45%, which confirmed the correctness of the proposed WPT model. Based on the results, it was determined that the greatest influence of the skin effect occurred at 1 MHz. Then, the efficiency decreased by no more than 9%, while in the case of the receiver power decreased by an average of 25%. Detailed analysis shows the influence of the skin effect on the system parameters, and can also be an important element in the design of WPT systems.

Feasibility Analysis of a Reduced Capacitive Wireless Power Transfer System Model for Transportation Electrification Applications

A practical approach in modeling a capacitive wireless power transfer (CPT) system that utilizes an electrostatic field for the power transfer is presented in this article. The reduced capacitance model (RCM) is derived from the conventional six capacitance model (SCM) for the CPT system in view of the large charging area applications, such as electric vehicle charging. The effect of the same side and cross-coupling capacitances diminishes when the separation distance between the same side plate pair is large enough, and the reduced capacitance model (RCM) is obtained. A bipolar capacitive-link dispersion distance proposed in this article acts as an indicator to decide the use of RCM or SCM depending on the application. Furthermore, RCM attains unity voltage gain and load-independent operation at the designed single resonant frequency, unlike the SCM, where the influence of multiple resonant frequencies is predominant. An experimental validation is performed to determine the effectiveness of the RCM.

COIL OPTIMIZATION DESIGN OF THE HORN SHAPE FOR UNDERWATER WIRELESS POWER TRANSFER

In the application scenarios of underwater wireless power transfer (WPT), a horn shape coil is proposed in this paper. Aiming to obtain the uniform magnetic field in a specific area, the horn shape coil is optimized by reasonably setting the tilt angle and the spacing of the turns. Moreover, the horn coil with optimal tilt angle and the horn coil with uneven spacing are designed. Considering the eddy current loss in seawater, the model of WPT system in seawater is established using the 3D electromagnetic simulator. Through simulation and analysis of eddy current loss under different conditions, the influence of eddy current loss on efficiency is illustrated. Finally, the transfer efficiency and output power are obtained by simulation and calculation. Also, the performance of the designed system is evaluated. It is found that the proposed system can effectively enhance the stability and anti-offset capability of WPT system, and then obtain the stable and efficient output.

Robust Control of Wireless Power Transfer Despite Load and Data Communications Uncertainties

This article focuses on the robust control of wireless power transfer (WPT) systems, to work satisfactorily around the desired resonant frequency in the presence of load and data communications uncertainties. The proposed robust control system is based on the quantitative feedback theory (QFT), consisting of a feedback compensator and a prefilter, which are designed by shaping the system's frequency responses, to satisfy the design constraints defined in terms of stability, tracking, and other desired requirements. A feature of QFT is to provide the designer with interactive graphical tools for the design and tuning of the feedback compensator and prefilter. Without loss of generality, this article elaborates the design of the QFT-based robust control for a WPT system with a full-bridge inverter and series-series capacitor-based compensation circuits and uncertain direct-current (dc) load. The data communications uncertainties are also addressed in the design. The effectiveness of the proposed QFT-based robust control methodology is evaluated through simulations and practical experiments and compared with H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> and Skogestad internal model control (SIMC) design methods. Since QFT is a model-based approach, this article also elaborates on small-signal transfer function modeling of WPT systems.

Research on the Characteristics of Wireless Power Transfer in Non-ferromagnetic Metal Pipe

With the development of various electronics, the way of transmitting energy by wire has brought increasingly negative effects on the operability and convenience of products. As wireless power transfer (WPT) technology requires no transmission lines, it has received increasingly wide attention. Most of the previous research on the technology of magnetic resonant coupling WPT mainly focused on the transmission of energy in the air. This paper establishes the wireless power transfer system model under non-ferromagnetic metallic environment and studies the effect of non-ferromagnetic metallic environment on coil self-inductance L, mutual inductance M and coil resistance R of WPT system. On this basis, the study on the relationship between coil diameter and mutual inductance is carried out for aluminium pipe, and the relationship between coil diameter and diameter of metal pipe at the maximum mutual inductance is fitted. Besides, experimental verification is conducted for the change of mutual inductance between the coils of WPT system in the aluminium pipe, presenting that the actual measurement results of mutual inductance in the aluminium pipe are consistent with the theory.

The capacitor regulator for maximizing wireless power transfer efficiency in retuned resonant state

In the field of wireless power transfer (WPT), it is of significance to maintain the high transmission efficiency between the transmitting and receiving circuits. However, due to the temperature and other uncertain factors, the deviation of the receiver's intrinsic frequency will lead to the decrease of the transmission efficiency, which is an urgent problem to be resolved. In view of the detuning problem, a new method of tuning using the capacitor regulator is proposed. The structure of the capacitor regulator tuning circuit is introduced first in this paper. Then, combined with the two-coil model of WPT system, the maximum system transmission efficiency under the tuning effect of the capacitor regulator is analyzed and discussed. MATLAB is utilized to analyze the system transmission efficiency in different resonant states, while the magnetic simulation model is established by Maxwell. Furthermore, the experimental verification platform is designed simultaneously. The simulation and experimental results demonstrate that the design method can improve the coupling state between the resonant coils and improve the transmission efficiency from 54.3 to 73.4% in the detuned state. This method has an important reference and guidance significance for the future research of WPT system.

Core Structure and Electromagnetic Field Evaluation in WPT Systems for Charging Electric Vehicles

The electromagnetic field (EMF) in a wireless power transfer (WPT) system needs to couple inductively between the primary and the secondary coils through a large air gap, thus giving the system a loosely coupled characteristic. Therefore, magnetically permeable material must be employed to improve the coupling and reduce leakage magnetic flux. However, adding an iron core increases the weight and introduces core loss as a new factor. In this paper, a WPT system model using a lumped circuit model is introduced. Moreover, the relationship between the relative permeability and the coupling coefficient in addition to the core amount (core thickness) and core loss are discussed. Three cores structure named: pot, slotted, and shaped bars cores are investigated using finite element method (FEM) software. Inspired by the investigation results, a new core structure using optimum shaped bars is proposed, the EMF level for reducing core loss in high-power transfer systems and in order to mitigate the EMF exposure to humans is intensively evaluated. The proposed core succeeded in reducing EMF and core loss by about 44% and 30%, respectively. The FEM software and physical prototype were used to validate the proposed optimum core structure. Results showed that 3.5 kW power transferred through a 20 cm air gap with 96% system efficiency(coil–coil).

A Cost-Effective Adaptive Rectifier for Low Power Loosely Coupled Wireless Power Transfer Systems

This paper introduces an integrated receiver circuit based on a full-wave adaptive rectifier (AR). It achieves complex impedance matching and enables complexity and cost reduction in resonant wireless power transfer (WPT) systems. The conversion and system efficiency based on this AR receiver are theoretically compared with other receiver architectures by using a WPT system model including all conduction and switching losses. Fabricated in a 0.18- $\mu \text{m}$ BCD process, the AR receiver chip operates at 6.78 MHz, occupies 3-mm2 active die area and includes control and supporting circuitry for independent control of the reactive and resistive parts of the load impedance. The chip was tested in a 2.5-W WPT system, purposely built with extremely low coupling coefficient to enable spatial freedom. Experimental data show that the proposed AR chip achieves up to 96% efficiency. In addition, when used in a WPT system, it delivers 2.15 W with 50.3% system efficiency and 1.96 W with 29% system efficiency for coupling coefficients $k=0.085$ and $k=0.03$ , respectively.

A multi‐objective optimization algorithm based on self‐organizing maps applied to wireless power transfer systems

SummaryIn this work, a new multi‐objective population‐based optimization algorithm is presented and tested. In this contribution, the concepts of fast non‐dominating sorting and density estimation using the crowding distance are used to create a multi‐objective optimization algorithm based on previous work, which is a single objective evolutionary optimization algorithm based on self‐organizing maps (SOMs). The SOMs paradigm introduces a strong collaboration between neighbors solutions that improves exploitation. Furthermore, the representative power of the SOMs enhances the exploration and diversification. A state of the art benchmark approach is used to evaluate the performance of the proposed algorithm, obtaining positive results. The test problem uses an analytical model of an inductively coupled wireless power transfer system (WPT). The objective is to optimize the WPT model characteristics in order to allow simultaneous data and power transfer between the coils. The WPT design approach uses more degrees of freedom than existing techniques leading to a number of solutions where both the power signals and the data signal can coexist on the same physical channel achieving good figures of merit. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Efficiency analysis of magnetic resonance wireless power transfer with three-dimensional transmitters

Generally, the transfer power of wireless power transfer (WPT) system reduces significantly with the increase of distance and angle between transmitting and receiving coils in traditional WPT system. Experiments with two transmitters in the magnetic resonance coupling WPT system have been shown that it can enlarge transfer power and create a stable region in power transfer efficiency in a certain space. However, two transmitters have a limited transfer power comparing to the three-dimensional WPT. In this paper, a model of WPT system with three-dimensional transmitters (3DT-WPT), which are perpendicular to each other and so cover three dimensional spaces, is proposed to overcome the drawbacks mentioned above and the 3DT-WPT system via magnetic resonance coupling is designed to verify the proposed model. The diversity of the characteristics of the transfer power is observed through changing the distance and normal angle between transmitting and receiving coils. Analysis and experiment results show that the proposed method has better performance than the two transmitters.