Academic literature on the topic 'High Efficiency Wireless Power Transfer Systemns (WPTS)'

Wireless power transmission has become a remarkable research topic due to its enormous application potential. Recent advances in machine learning have been shown to be the most promising approach that offers significant capabilities in the wireless power transfer system (WPTS) for selecting the optimal frequency tuning to achieve high efficiency performance. However, developing an automated frequency-tuned system remains a challenge. In this study, a novel frequency-tuned method is presented that utilises machine learning-based models such as neural networks (NN), support vector regression (SVR), and linear regression (LR) to estimate the best efficiency provided by the frequency level at the most optimal frequency tuning level from the experimental dataset, which is capable of aiding in the selection of the most efficient WPTS design. The results show that the SVR has the highest degree of accuracy, making it a promising option for optimising the tuning of power transfer systems while enhancing their performance efficiency. Keywords—Efficiency, frequency tuning, machine learning, neural network, power transfer

The paper deals with an evolutionary method for solving many-objective optimization problems exhibiting a high-dimensionality objective space, which is a challenging problem. An application in the optimal synthesis of Compensation Networks (CNs) of wireless power transfer systems for charging the batteries of electric vehicles is developed. This design problem is characterized by a set of multiple objectives in mutual conflict, which should be simultaneously considered. The optimization aims to the maximization of both the efficiency and the transferred power; a further criterion selects the networks with a suitable profile of impedance vs. frequency. Moreover, the minimization of current and voltage values relevant to inductors and capacitors in the networks, respectively, is pursued. These five design criteria are optimized exploiting the concept of the degree of conflict, which is the core of the proposed method, named “EStra-many”. The method is applied by considering two approaches: the single-objective one, based on the degree of conflict function only, and the bi-objective approach in which the tradeoff between the degree of conflict function itself and another objective function (in turn, the efficiency, the transferred power, the distance of the resonance frequency from the supply frequency, the maximum value of the inductance current, the maximum value of the capacitor voltage, the distance from the Utopia point, and the number of inductors in the CN), is searched for. This way, all in one, seven different optimization problems are solved. The main element of novelty of the paper is a method to solve an optimization problem characterized by a high number of objective functions. In view of this, instead of considering a weighted sum of the objectives, a preference function inspired by the concept of least-conflict solution is formulated accordingly, the preference function is minimized by a cost-effective evolutionary algorithm of lowest order.

The paper presents a simplified analysis of harmonically terminated rectifier circuit and experimental results of a Schottky diode rectifier with even and odd harmonic terminations. The analysis is based on the Fourier series expansion of the voltage and current across the diode circuit. Harmonic terminations similar to the techniques used for power amplifiers are studied. A maximum efficiency of 84% at 30 dBm is obtained with second- and third-order harmonics terminated. The optimum value of dc load to maximize efficiency is obtained by sweeping the load. An optimal operating range of 28–35 dBm is obtained. The applications of the rectifier in wireless charging and power transfer systems are discussed.

The paper is focused on the optimization of the compensation network of a wireless power transfer system (WPTS) intended to operate in dynamic conditions. A laboratory prototype of a WPTS has been taken as a reference in this work, allowing for the experimental data and all the numerical models here presented to reproduce the configuration of the existing device. The numerical model has been used to perform FEM analysis with variable relative positions of the emitting and receiving coil to simulate the movement in a ‘recharge while driving’ condition. Inductive lumped parameters, i.e., self and mutual inductances computed from FEM results, have been used for the optimal design of the compensation network necessary for the WPTS operation. The optimal design of the resonance circuits has been developed by defining objective functions, aiming to achieve these goals: transmitted power must be as constant as possible when the vehicle is in movement and the electrical efficiency must be satisfactory high in most of the coupling conditions. The performances of the optimized network are finally compared and discussed.

AbstractIn this paper, we use convex optimization to maximize power efficiency through cascaded multi-coil wireless power transfer systems and investigate the resulting characteristic spacing. We show that although the efficiency is generally a non-convex function of the coil spacing, it can be approximated by a convex function when the effects of higher-order couplings are small. We present a method to optimize the spacing of cascaded coils for maximum efficiency by perturbing the solution of the convex approximation to account for higher-order interactions. The method relies on two consecutive applications of a local optimization algorithm in order to enable fast convergence to the global optimum. We present the optimal configurations of coil systems containing up to 20 identical coils that transfer power over distances up to 4.0 m. We show that when spacing alone is optimized, there exist an optimal number of coils that maximize transfer efficiency across a given distance. We also demonstrate the use of this method in optimizing the placement of a select number of high-Q coils within a system of low-Q relay coils, with the highest efficiencies occurring when the high-Q coils are placed on either side of the largest gaps within the relay coil chain.

The following paper presents a highly efficient wireless power transfer (WPT) system for unmanned aerial vehicle (UAV) applications. The proposed system is designed as a deployable landing pad, where UAVs can be efficiently charged at distances up to 20 cm, while the UAV is landing. The operation frequency is 50 kHz. The current work presents two major contributions that help improve this aspect: a novel RX charging pad geometry and an unconventional design of a low-voltage, high-power DC–AC inverter using discrete MOSFET transistors. Both the pad’s geometry and the inverter are designed specifically for UAV applications. The input DC to output AC system efficiency peaks at approximately 95%. The peak efficiency is obtained at power transfers of 625 W. A major difference between the present design and traditionally used state-of-the-art systems is the low DC supply voltage requirement of just 24 V, compared with typical values that range from 50 up to 300 V at similar output power.

A preliminary numerical analysis of the power transfer efficiency (PTE) for the forward link of near-field (NF) ultra high frequency (UHF)-radio frequency identification (RFID) systems is addressed in this paper, by resorting to an impedance matrix approach where the matrix entries are determined through full-wave simulations. The paper is aimed to quantify the NF-coupling effects on the PTE, as a function of the distance between the reader and tag antennas. To allow for a PTE comparison between different reader and tag antenna pairs, a benchmarking tag-loading condition has been assumed, where the tag antenna is loaded with the impedance that maximizes the PTE. In a more realistic loading condition, the load impedance is assumed as equal to the conjugate of the tag antenna input impedance. Full-wave simulations use accurate antenna models of commercial UHF-RFID passive tags and reader antennas. Finally, a “shape-matched antenna” configuration has been selected, where the reader antenna is assumed as identical to the tag antenna. It is shown that the above configuration could be a valuable compact solution, at least for those systems where the relative orientation/position between the tag and reader antennas can be controlled, and their separation is of the order of a few centimeters or less.

Wireless power transfer (WPT) systems for charging Electric Vehicles (EVs) have gained extensive attention due to their many advantages. However, human exposure to electromagnetic fields (EMFs) has become a serious concern in high-power cases. In this paper, shielding techniques, including magnetic, metallic, and resonant reactive current shields, are investigated. Finite element method software is used to evaluate and compare the shielding effectiveness, charger weight, and system performance. The results show that the resonant reactive current shielding has a low EMF level with reasonable system efficiency and acceptable charger weight. In addition, 5 kW with 15 cm air gap WPT chargers were built to validate the simulation results.

Wireless power transfer (WPT) systems have attracted considerable attention in relation to providing a reliable and convenient power supply. Among the challenges in this area are maintaining the performance of the WPT system with the presence of a human body and minimizing the induced physical quantities in the human body. This study proposes a magnetic resonant coupling WPT (MRC-WPT) system that utilizes a resonator with a grounded loop to mitigate its interaction with a human body and achieve a high-efficiency power transfer at a short range. Our proposed system is based on a grounded loop to reduce the leakage of the electric field, resulting in less interaction with the human body. As a result, a transmission efficiency higher than 70% is achieved at a transmission distance of approximately 25 cm. Under the maximum-efficiency conditions of the WPT system, the use of a resonator with a grounded loop reduces the induced electric field, the peak spatial-average specific absorption rate (psSAR), and the whole-body averaged SAR by 43.6%, 69.7%, and 65.6%, respectively. The maximum permissible input power values for the proposed WPT systems are 40 and 33.5 kW, as prescribed in the International Commission of Non-Ionizing Radiation Protection (ICNIRP) guidelines to comply with the limits for local and whole-body average SAR.

The optimization, manufacturing, and performance characterization of a miniaturized 3D receiver (RX)-based wireless power transfer (WPT) system fed by a multi-transmitter (multi-TX) array is presented in this study for applications in capsule endoscopy (CE). The 200 mm outer diameter, 35 μm thick printed spiral TX coils of 2.8 g weight, is manufactured on a flexible substrate to enable bendability and portability of the transmitters by the patients. The 8.9 mm diameter—4.8 mm long, miniaturized 3D RX—includes a 4 mm diameter ferrite road to increase power transfer efficiency (PTE) and is dimensionally compatible for insertion into current endoscopic capsules. The multi-TX is activated using a custom-made high-efficiency dual class-E power amplifier operated in subnominal condition. A resulting link and system PTE of 1% and 0.7%, respectively, inside a phantom tissue is demonstrated for the proposed 3D WPT system. The specific absorption rate (SAR) is simulated using the HFSSTM software (15.0) at 0.66 W/kg at 1 MHz operation frequency, which is below the IEEE guidelines for tissue safety. The maximum variation in temperature was also measured as 1.9 °C for the typical duration of the capsule’s travel in the gastrointestinal tract to demonstrate the patients’ tissues safety.

Over the last decade, fossil fuel prices have significantly increased due to the dependency on hydrocarbon energy sources for transportation and electricity generation. In order to solve power generation issues, most governments in the world have heavily promoted the installation of roof top solar photovoltaic (PV) in domestic low voltage and commercial high voltage distribution networks. In addition, Electric Vehicles (EVs) have been introduced to substitute the hydrocarbon fuelled transportation which is required to provide high mileage and affordable prices. Currently, EVs have been charged with the utilisation of plug-in AC and DC chargers to charge their battery bank. To expand their range, EVs are required to have larger energy storage batteries, which leads to higher costs and limits their adoption in society. Furthermore, plug-in chargers require manual operation to connect to EVs, which may create health and safety issues such as electric shock and fire. Wireless Charging Systems (WCS) have the potential to minimise both these major concerns by offering frequent charge while the EV is in stationary or dynamic modes. Frequent charge to the EVs at the car park, traffic signal and on the roads brings indefinite charging options which can dramatically reduce the battery bank size. However, improvements in some of the challenging factors such as health and safety, power levels and power efficiency requires further investigation to create a user-friendliness of the WCS for EVs. This thesis deals with the investigation of concerning issues which are limiting the development of Wireless Electric Vehicle Charging Systems (WEVCS) from becoming a part of the electrified transportation system. Currently available wireless power transfer technology for the EVs has been studied including wireless transformer structures with a variety of ferrite shapes. WEVCS are associated with many health and safety issues, which have been discussed with the current developments in international standards. Two major applications; static and dynamic WEVCS, have been explained with up-to-date progress from research laboratories, universities and industries. A variety of laboratory prototypes have been developed with the help of calculation and simulation methods, and verified with experimental techniques. Firstly, High Frequency Wireless Planar Transformers (HFWPT) are used to investigate the flux leakages and other electromagnetic compatibility (EMC) problems which are associated with the wireless charging system’s efficiency. The HFWPT was designed using the bifilar winding concept on a PCB. An LLC resonant converter has been designed to improve the conversion efficiency with a maximized air gap. Assisted by a near-field scanner, the magnetic field has been analysed with and without a magnetic ferrite core at resonant frequency. The magnetic ferrite core in this arrangement is used to minimize flux leakages and to increase the magnetizing impedance. In addition, EMC computer modeling and simulation techniques are employed to investigate the magnetic flux distribution and associated EMC problems such as stray fluxes and hot spots. A finite element method (FEM) has been used to calculate the magnetic field. The effect of the planar magnetic ferrite cores on magnetic flux distribution has been investigated by using three designs. The first design has the ferrite core only at the primary side, the second draft has a planar core on the primary and secondary side, and the third design has a U-shape magnetic core for the primary and secondary side. A new proposed design is introduced to minimize flux leakages and reduce hot spots, in order to improve the flux distribution and to increase the magnetizing impedance. Poor considerations of leakage flux between the primary and secondary coils may cause complications for persons with a pacemaker or any other life supporting electronic devices. Two scenarios are investigated via computational simulation. Firstly, a simulation of a person with an electronic biomedical implant device standing beside a car during the charging process through the WCS is investigated. Secondly, a person is walking or standing over the primary coil area of the WCS when the system is not in charging mode. Both of these scenarios include an investigation of four different versions of magnetic core configurations, to examine the outer magnetic flux distribution as well as the power distribution of the WCS by using a FEM simulation. Another concerning issue is the lower power transfer efficiency of WCS for EVs in comparison to the plug-in due to the poor coupling between the transmitter and receiver charging pads. In order to solve the problem, in-wheel WCS for EVs have been introduced with a concept proven laboratory prototype, which can operate in static and dynamic applications. The coupling coefficient is dependent on the thickness of the tire rubber and the transmitter installation height underneath the road surface. A variety of scenarios have been applied to study the in-build steel belt (IBSB) tire effect on the wireless power transfer for the static and dynamic cases. FEM simulation has been performed to investigate the magnetic flux distribution and leakage fluxes due to IBSB in the vehicle’s tire. Finally, the Wireless Vehicle to Grid (W-V2G) concept has been presented to solve future instability issues on the distribution networks created by unscheduled feedback power from renewable energy sources (RES). In addition, W-V2G can provide a platform to transfer power wirelessly in both directions: grid to vehicle and vehicle to grid where the EV’s battery can be a back-up of additional energy storage to reduce the peak demand energy requirements. A 3.7 kW wireless transformer for a single phase W-V2G prototype, and a high efficiency compact filter inductor for a D-StatCom inverter in the three phase 30 kVA W-V2G have been built with the utilisation of calculation and simulation methods. Both prototypes have been constructed and validated with experimental methods. Currently, a 3.7 kW W-V2G prototype is under development, and will be finished in future with complete systems analysis and results.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Eng & Built Env<br>Science, Environment, Engineering and Technology<br>Full Text

Many studies on EVs have been performed in recent years, and various EVs have been developed, like pure battery EVs, hybrid EVs, battery replace EVs, or plug-in hybrid EVs, that use lithium (or polymeric) batteries that can be recharged at home or at a charging station. The biggest challenge to the commercialization of the EV is the battery. The battery problems on electric vehicles can be solved by using roadway-powered electric vehicles (RPEVs). RPEVs do not require heavy and large batteries because they directly get power while moving on a road. These vehicles can take power either in a wired or wireless way. Thus, various wireless power transfer systems (WPTSs) have been developed for RPEVs, and as consequence, new types of RPEV have been developed. WPTS for RPEVs should be able to deliver high power efficiently through a small air gap for avoiding collision between the road and the vehicle.

In this paper, the proposed work conveys an efficient way to the desired extent while maintaining stable power generation and efficiency over long distances which has been difficult for past decades. These inductive or microwave plus coupling varieties are typically regarded key characteristics in a regularly used system. In a broad sense, capacitive coupling (CC), magnetic resonance coupling (MRC), microwave radiation (MR), &amp; inductive coupling are the 4 kinds of coupling. Since its evaluation in the mid-1930s, when it was utilized as element of both the Synchronization of the level and lateral outputs of television, it has progressed to a Progressed representation of coordinated circuit (IC). Technological advances have been identified inside a long range of applications nowadays. The very first PLL ICs started available about 1965. Furthermore, its quality factor allows for maximum coupling efficiency at longer wavelengths and voltages. Past decades proved that obtaining a wide range of components leads to optimizing the wireless power transfer system. The suggested control approaches and frequent usage of PLL are described in this research, and they will enhance the effectiveness of the transmission frequency to acquire as much distance as possible while maintaining the required efficiency. Furthermore, the proposed technique for the inverter, which is dependent on the saturation principle, necessitates the monitoring of potential within transmitter and reception coils. The high-frequency transformer, on the other hand, fulfilled the specified distance at Megahertz by stepping up the regulated voltage and frequency using coil parameters. With the aid of optimization in coil settings, this suggested work approaches a novel high efficiency experiment and control upon coupled magnetic resonance across a large range of load power also with PLL that can raise the voltage at a rather high value to get the wide range. In a WPT system, this simple way can obtain optimal distance. The MATLAB-2019b environment was used to evaluate the simulation.