Power Transfer Mechanism Research Articles

Optimization of magnetic coupling mechanism of dynamic wireless power transfer based on NSGA-II algorithm

Optimization of magnetic coupling mechanism is an important way to improve the performance of a dynamic wireless power transfer system. Inspired by the common radial magnetic core for circular coils, a new radial magnetic core for rectangular coils is adopt. Through simulation and experimental results comparison, which has higher coupling coefficient with the same core area. Combined with the magnetic circuit analysis, the magnetic flux leakage and conduction regions are divided into magnetic fluxes with different shapes, which magnetic resistances are calculated respectively. Based on the simulation results, parameter distributions of fluxes under different conditions are obtained. Therefore, the expressions of the coupling coefficient k of the adopt magnetic cores and coils and the design parameters of coils and cores are obtained. Taking the maximum k and the minimum rate of change of coupling coefficient with 100 mm displacement as the optimization objectives, a multi-objective optimization solution is carried out by using NSGA-II algorithm. The coil optimization scheme is obtained and verified by experiments. k and Δk are 0.442 and 6.8% respectively, and the errors are less than 5%. In the optimization process, there is no simulation model constructed. The optimization modeling combined of magnetic field segmentation method and parameter fitting has lower complexity and calculation time of optimization.

Laser-Powered Vibrotactile Rendering

We investigate the feasibility of a vibrotactile device that is both battery-free and electronic-free. Our approach leverages lasers as a wireless power transfer and haptic control mechanism, which can drive small actuators commonly used in AR/VR and mobile applications with DC or AC signals. To validate the feasibility of our method, we developed a proof-of-concept prototype that includes low-cost eccentric rotating mass (ERM) motors and linear resonant actuators (LRAs) connected to photovoltaic (PV) cells. This prototype enabled us to capture laser energy from any distance across a room and analyze the impact of critical parameters on the effectiveness of our approach. Through a user study, testing 16 different vibration patterns rendered using either a single motor or two motors, we demonstrate the effectiveness of our approach in generating vibration patterns of comparable quality to a baseline, which rendered the patterns using a signal generator.

A Review of Capacitive Power Transfer Technology for Electric Vehicle Applications

Electric Vehicle (EV) wireless power transfer technology is an excellent solution to propel EVs forward. The existing wireless power transfer technology for EVs based on Inductive Power Transfer (IPT) technology has the drawbacks of large size, high weight, and high eddy current loss, limiting the further application of this technology. Capacitive Power Transfer (CPT) technology, with its advantages of low cost and light weight, has attracted widespread focus in recent years and has great potential in the field of EV wireless power transfer. This paper begins with the principle of CPT, introduces the potential and development history of CPT technology in the field of EV wireless power transfer, and then reviews the coupling mechanism and resonance compensation network of the CPT system to satisfy the requirements of EV wireless power transfer, including the coupling mechanism of EV static power transfer and dynamic power transfer, and the high-performance resonance compensation network to the requirements of EV wireless power transfer. Finally, this paper reviews the existing problems of CPT technology in the field of EV wireless power transfer and summarizes its future development directions.

Remaining Opportunities in Capacitive Power Transfer Based on Duality With Inductive Power Transfer

Wireless power transfer (WPT) has proven to be an effective solution for electric vehicle charging. As two mainstream near-field WPT technologies, inductive and capacitive power transfer (IPT and CPT) have many similarities. This paper aims to explore the remaining opportunities in CPT systems, not yet reported in existing literature, based on duality with the mature IPT technology. First, a generic modeling method based on two-port network theory is proposed, which contributes to unified modeling and analysis for both inductive and capacitive couplings. Then, power transfer mechanism of IPT and CPT couplers is compared, and unified transfer efficiency is derived, promoting CPT theory developments. Last, the duality between existing IPT and CPT circuits is demonstrated in two aspects: compensation circuit configuration and resonant relationship. 14 CPT topologies are derived based on duality with the existing 7 mainstream IPT circuits, of which 11 circuits do not exist in literature, offering future opportunities in CPT. Detailed comparison and evaluation of the derived 14 CPT circuits are conducted, and high-performance circuits are recommended. As a demonstration, a case study of a 2.1kW 3MHz CPT system is implemented in hardware based on the newly proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> - <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SS</i> topology. This example system achieves a peak efficiency of 93.19% with the predicted circuit properties of load-independent constant-voltage (CV) output and zero-phase-angle (ZPA) property.

Higher-order topological corner state in a reconfigurable breathing kagome lattice consisting of magnetically coupled LC resonators

Higher-order topological insulators are attracting attention from fundamental interest to fascinating applications, owing to the topological properties with higher-order topological corner states. Breathing kagome lattice is a prospective platform which can support higher-order topological corner states. Here, we experimentally demonstrate that higher-order topological corner states are supported in a breathing kagome lattice consisting of magnetically coupled resonant coils. The winding direction of each coil is determined to hold C3 symmetry for each triangle unit cell, enabling to emerge higher-order topological corner states. In addition, topological and trivial phases can be switched by changing the distances between the coils. The emergence of corner states in the topological phase is experimentally observed through admittance measurements. As an illustration, wireless power transfer is performed between the corner states, and between the bulk and corner states. The proposed configuration is a promising platform for not only investigating topological properties of the breathing kagome lattice but also an alternative mechanism of selective wireless power transfer.

Research on Transfer Mechanism and Power Improvement Technology of the SCC-WPT System

Single capacitive coupled wireless power transfer (SCC-WPT) technology only needs one pair of metal plates for energy transmission. This provides a unique advantage in two-dimensional plane dynamic wireless power transfer. However, in practical application, this technology has a clear challenge in improving the transmission power ratings and efficiency. This article studies the power transfer mechanism of the SCC-WPT system based on stray capacitance and self-capacitance. A universal system model has been investigated, where the equivalent circuit model of the system is proposed. The two-port network of the coupler critical factors that limit the transmission power of the system has been analyzed. A new <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC–CL</i> compensation topology is proposed to achieve a phase difference of voltage between the primary side and secondary side to 90°, which improves the transmission power of the SCC-WPT system. In addition, the resonant operating condition of the system together with the efficiency is analyzed. Finally, an experimental prototype is built under the guidance of the analysis. Both simulation and experimental results verify the validity of the proposed model and the topology. The experimental results show that the prototype achieves 266 W output power with 62% dc–dc efficiency.

Information Harvesting for Far-Field Wireless Power Transfer

In today's smart world, the Internet of Things (IoT) offers a very large scale of technologies and use cases. An IoT system comprises a huge amount of low-power IoT network elements, sensors, and smart devices connected to each other. For these devices, it is important to have a sufficient level of energy resource for communication and to receive software/firmware updates periodically. In this aspect, wireless power transfer is a popular paradigm to tackle energy limitations. Therein, the battery of IoT devices can be remotely replenished by means of radio-frequency-radiated signaling, referred to as far-field wireless power transfer. Furthermore, harvesting energy from ambient communication signals available in the environment introduces simultaneous wireless information and power transfer technology. These systems face the trade-off between information capacity and energy harvesting efficiency. Accordingly, various signaling design frameworks have been proposed to comply with different system preferences between power and information. In this work, aside from existing trends, we propose a novel concept, information harvesting (IH), which introduces a novel protocol that lies in transmitting information on top of the existing wireless power transfer mechanism. Considering the diversity of IoT networks and the availability of wireless power transfer infrastructure, the proposed IH principle may turn out to be a pivotal methodology that combines physical layer security with wireless power transfer, particularly for cases where a large number of IoT devices require software/firmware updates along with periodical battery recharging needs.

UAV–Assisted Joint Wireless Power Transfer and Data Collection Mechanism for Sustainable Precision Agriculture in 5G

The limited battery capacity of sensor nodes is one of the challenges for achieving sustainable precision agriculture in 5G. When the sensor nodes run out of energy, the data center will not be able to grasp the information of the environment, and the corresponding decisions and actions will not be performed. To solve this problem, this study presents a framework for charging sensor nodes and collecting sensing data using Unmanned Aerial Vehicle (UAV). The problems of cluster head election and path planning are considered at the same time to maximize charging efficiency in a way that the lifetime of sensor nodes can be prolonged. Moreover, K-means based Cluster Head and Charging Position Selection algorithm (KCHCPS) and ACO-based Charging Path Planning Algorithm (ACOCPP) are proposed to optimize charging planning of the 3D environment. Simulation results clearly show the advantages of the proposed mechanism as compared to the state-of-the-art works.

Three Phase Coil based Optimized Wireless Charging System for Electric Vehicles

With modernization and technology enhancements on a global scale, environmental consciousness has also been increasing in recent days. Various technologies and automobile industries are vandalized with sustainable solutions and green technologies. Transportation via roadways is mostly preferred for distant travel as well, despite the advancements in airways and railways, due to less capital outlay, door to door service possibility in rural areas etc. The conventional fuel vehicles are a huge contributor to environmental pollution. Electric vehicles are an optimal solution to this issue. The lives of the common masses are not impacted largely by the electric vehicles despite their market commercialization since a few decades. It is due to certain challenges associated with the electrical vehicles. A 100% efficient perpetual machine does not exist yet. Predominantly, challenges related to charging, hinders the success of e-vehicles. Frequent charging is required in case of long-distance travel and other scenarios in the existing vehicles. Based on the respective governments, extensive changes are made in the infrastructure to overcome the issues at the charging stations. In this paper, an enhanced wireless charging module for electric vehicles is presented. The use of multiple coils is emphasized for building up energy and transmitting it. The inductive power transfer mechanism and efficiency of the system are improved with the design of a three-phase coil. The mechanism for assessment of the energy consumed in e-vehicles is also discussed.

Wireless power transfer in attenuating media

Dissipative media (underground/underwater, biological materials and tissues, etc.) pose a challenge to inductive wireless power transfer systems as they generally attenuate the near fields that enable mutual coupling. Apart from this, the impact of the environment on electromagnetic fields can also be seen in the self-impedance of coils, resulting in significant eddy current losses and detuning effects. In this article, we study, theoretically, the mechanism of wireless power transfer via a pair of magnetic resonators inside an infinite homogeneous medium with a comprehensive circuit model that takes into account all the electromagnetic effects of the background medium. This analytical approach can offer deep insights into the design and operation of wireless charging systems in non-ideal environments.

Investigation of reactive power distribution between two coils of inductive power transfer system by Poynting vector analysis

It is well known that real power can be transferred through the air gap between two coupled coils in an Inductive Power Transfer (IPT) system, but little is known about how the reactive power spatially circulates in the airgap between the coils. This paper investigates the reactive power distribution in an IPT system from the field point of view. The Magnetic field, electric field and resultant Poynting vector at an arbitrary point between two coupled coils are analysed by fundamental electromagnetic equations. In particular, the reactive power distribution is investigated under both open-circuit and loaded conditions. The measured results at the input and output of the two coupled coils show a good agreement with the Poynting vector and lumped circuit analysis. Furthermore, the Poynting vector analysis shows that the two mutual components of the Poynting vector contribute to reactive power circulation between the two coupled coils, while the self-components only affect the generation of reactive power around the individual coil. These results cannot be obtained by numerical or traditional lumped circuit analysis, and they are very useful for understanding the deep-level physical power transfer mechanism of an IPT system.

Study of power flow mechanism of capacitive power transfer system based on Poynting vector analysis

In this paper, the power flow mechanism of a typical Capacitive Power Transfer (CPT) system is studied by analysing the electric field, magnetic field, and Poynting vector, to determine the power distribution as well as the average power flow to the load. It is found that the average power from the source flows along the wires on the transmitting side and passes the external areas of the coupling plates mainly along the channel between the two coupling pairs (instead of going through the air gaps in between), then converges along the wires before reaching the load. The average power calculated by integrating the real part of the Poynting vector across a defined power flow plane at the receiving end is consistent with CST (Computer Simulation Technology) simulation, circuit analysis, and practical measurements of the CPT system. Although the power density described by Poynting vector changes with the separation distance between the two coupling pairs, the total average power keeps approximately constant because the power flow area changes accordingly. Compared to the traditional lumped circuit analysis, the Poynting vector analysis shows the power distribution around the coupling plates in relation to their physical configuration. This research reveals the power flow mechanism and distribution in a CPT system from field point of view, which is useful to gain deeper understanding of the CPT system beyond the traditional circuit theory and would also be helpful to improve practical system design in the future.

Feasibility assessment of next-generation drones powering by laser-based wireless power transfer

Utilizing drones in many applications such as video and photography, farms, search and rescue operations, construction industry for mapping and site monitoring has increased. However, their operating time is limited according to the capacity of their batteries. Therefore, many researchers attempt to enhance the operating time of drones. In this study, to the best of the authors' knowledge for the first time, the feasibility assessment of a laser-based wireless power transfer (WPT) mechanism is theoretically investigated on drone applications to increase their operating time. In this method, drones can be charged during operation wirelessly at a considerable distance with acceptable efficiency. The Analytical code is developed in Engineering Equation Solver (EES) software. The acquired results for the main components of the system have a good agreement with published papers of other researchers. In this study, three commercial photovoltaic (PV) materials were evaluated. The results show that an equipped drone with laser-based WPT system is able to approximately receive net power of 73.5, 62.6, and 33.2 W at a 500 m distance by GaAs, CdTe, and c-Si PV materials, respectively, while the laser module consumes around 600 W electrical power. Moreover, since the optical power of the laser is concentrated on PV panel, a two-phase cooling system is suggested for PV panel to reduce the temperature of the under radiate area. Results demonstrate that the temperature of GaAs PV material without a two-phase cooling system is approximately three times more than the temperature of PV panels with a two-phase cooling system at high power transfer rates.

Design and experimental verification of self-powered electromagnetic vibration suppression and absorption system for in-wheel motor electric vehicles

A self-powered electromagnetic vibration suppression and absorption system integrated with a magnetorheological damper and a linear motor is designed to attenuate the negative effect of vertical vibration caused by the increased unsprung mass for in-wheel motor electric vehicles in this article. The magnetorheological damper is used as a suspension damper to suppress body vibration, and linear motor is used as a dynamic vibration absorber, namely, linear electromagnetic dynamic vibration absorber, to absorb tire vibration, and regenerates the vibration power to drive the magnetorheological damper, realizing self-power. Based on power flow theory, the power transfer mechanism of the vertical vibration for in-wheel motor electric vehicles and the regeneration potential are analyzed. The negative effect on the dynamic performance of in-wheel motor electric vehicles is analyzed through the root mean square of dynamic responses. Moreover, the specific structure scheme of the self-powered electromagnetic vibration suppression and absorption system is provided. The influence of system mass, stiffness, and damping of the linear electromagnetic dynamic vibration absorber on the dynamic performance is analyzed, and these parameters are optimized by particle swarm optimization. Simulation results show that in comparison with a passive damper, the self-powered electromagnetic vibration suppression and absorption system can reduce the body acceleration by 17.05%, which is better than the magnetorheological damper (10.08%). The self-powered electromagnetic vibration suppression and absorption system increases the tire dynamic load by 5.62%, but it is 8.68% less than the magnetorheological damper. Additionally, the regenerated power can offset the consumed power adequately to realize self-power. Finally, a bench test is conducted to verify the effectiveness and feasibility of the self-powered electromagnetic vibration suppression and absorption system.

Modeling Single-Wire Capacitive Power Transfer System With Strong Coupling to Ground

This article presents the modeling of a single-wire capacitive power transfer (CPT) system to reveal its power transfer mechanism with strong coupling to ground. An equivalent circuit is proposed by treating the ground as a quasi-conductive medium. The parameters of the equivalent circuit model are determined, including the capacitance between the coupling plates of the CPT system, the single-wire inductance and capacitance between the wire and the ground, and the ground equivalent impedance. The maximum power transfer capacity corresponding to the system's resonant frequency is analyzed by using the proposed model to guide the system tuning design. A prototype single-wire CPT system is built, and a computer simulation technology (CST) model is undertaken to show the electric and magnetic field distributions, and the Poynting vector indicating the direction and magnitude of the power flow in the system. It is shown that the output voltage and the power predicted by the theoretical model are in good agreement with the simulation and practical results under the frequency and load variations. Different lengths of the dangling single wire at the secondary side of the CPT system are also investigated to validate the model with different levels of ground effects.

Data Collection in MI-Assisted Wireless Powered Underground Sensor Networks: Directions, Recent Advances, and Challenges

Wireless underground sensor networks (WUSNs) facilitate remote monitoring and control of various underground environments, which are suffering from a significant reliability problem. To address this problem and relieve the ongoing networking challenges, we propose a new concept, called the magnetic induction (MI)-assisted wireless powered underground sensor network (MI-WPUSN), which integrates the advantages of MI communication techniques with those of wireless power transfer mechanisms. MI-WPUSN offers a unique platform consisting of seven envisioned devices and four distinct communication modes to provide significant reliability potential, which is constrained by its complex and challenging data collection. To unlock the potential of MI-WPUSN, we provide a systematic research roadmap for MI-WPUSN data collection, spreading from sensor deployment to multiple channel access control and to frequency-selective routing establishment. Specifically, we first summarize the state-of-the-art research advances on sensor deployment, based on which we propose a bidirectional projection-based deployment topology that achieves high network reliability and discuss the sensor numerical determination problem resorting to weighted Voronoi diagrams. We then introduce the principles for multiple channel access control and review the existing research. Finally, after introducing kernel regression methods that can easily handle the frequency-selective property of MI-WPUSN, we develop a modified Q-learning-based routing protocol. In particular, we list and analyze the underlying challenges and related future issues in each direction.

The impact of wrist joint movement on stroke effect during topspin forehand in table tennis

ABSTRACT The main purpose of this study was to explore the impact of the wrist joint movement on the stroke effect, especially that of the angular velocity and linear velocity on the ball speed and spin speed. Thirty-two young table tennis players were randomly selected from China Table Tennis College. The high-speed infrared motion capture system was used to collect the real-time data of the wrist joint movement during the stroke, and the high-speed camera was used to measure the spin speed. The influence of the wrist joint movement on the stroke effect was analysed. The results of this study showed that the linear velocity of the right wrist joint was positively correlated with ball speed (r = 0.283, p < 0.01) and spin speed (r = 0.162, p = 0.032). The angular velocity of the right wrist joint had a significant positive correlation with the ball speed (r = 0.251, p = 0.015) and spin speed (r = 0.391, p < 0.01). The results of this study further explained the mechanism of power transfer by the kinetic segment-chain, which provided a valuable reference for formulating targeted training plans for young table tennis players.

Dynamic Inertia Evaluation for type-3 Wind Turbines Based on Inertia Function

Inertia constant is widely used to evaluate the inertia capability for wind turbines (WTs). However, the method fails to reflect the dynamic characteristics of the inertia and neglects the impacts of controllers. For this issue, this article establishes an inertia function to analyze the dynamic inertia for type-3 WTs. Firstly, the consistency of the power transfer mechanisms between the type-3 WT and synchronous generator (SG) is discussed. Then, a new approach to construct the inertia function is offered according to the phase motion model of SG. On this basis, the impacts of the controllers and operating points on the inertia are explored, and the critical factors are revealed. The analysis results help to understand and optimize the inertia capability of the type-3 WT. Moreover, compared with the conventional inertia constant, the presented inertia function can better reveal the dynamic nature and the influence rule of inertia. Finally, the analysis is validated by IEEE 3-bus test system simulation.

Dynamic Phasor Modeling and Analysis of Three-Phase DC/DC/AC MMCs for Hybrid AC/DC Grids

The first comprehensive three-phase state-space dynamic phasor model (DPM) for the emerging class of dc/dc/ac modular multilevel converters (MMCs) is presented that accounts for both dc/dc and dc/ac power transfer mechanisms. The phasor model is derived in the α β 0-frame and includes frequency components from dc to third harmonic, which is shown to yield a high degree of matching for both steady-state and transients when compared against switched and time-averaged models, the latter of which is also derived in this work. An analytical solution procedure is then proposed that takes advantage of the phasor model time-invariance to find the full state solution at any operating point including the requisite open-loop modulating signals. Several analyses are carried out for two different dc/dc/ac MMC case study designs to explore the utility and versatility of the proposed DPM and solution procedure. Results show the patterns of internal current stresses and capacitor voltage ripples for the arms can vary significantly and in a nonsymmetrical manner, which is in stark contrast to the traditional dc/ac MMC.

Multiport Converter With Enhanced Port Utilization Using Multitasking Dual Inverters

With the development of renewable energy and electric vehicle technologies, a need for multiport DC/DC/AC converters with high power density and reliability has arisen. A dual inverter based bidirectional multiport converter with two dissimilar voltage DC ports and an AC port is presented. The converter is capable of processing up to 1.67, 1.41, and 1 p.u. of power through its main DC, auxiliary DC and AC ports respectively, while only using the semiconductor and magnetics effort of a DC/AC converter rated for 1 p.u. Analysis reveals that this is more than thrice and twice the power limits of the main and auxiliary DC ports respectively, compared to using two independent inverters with a three-winding transformer. Furthermore, the proposed converter is more efficient than the latter option. These benefits are due to the multitasking of inverters and the existence of single stage DC/DC and DC/AC power transfer mechanisms enabled by the use of a center tapped transformer. A control strategy using these two mechanisms, capable of independently controlling the power flows between ports is also presented. Independent inverter control is also possible, allowing power flow between the main DC and AC ports during the failure of a single inverter. These claims are verified through thorough analysis, extensive simulation and experimental results using a 3 kW prototype.