Contactless Power Transfer System Research Articles

Easy-to-install battery storage based residential power supply with contactless power transfer

Solar energy with battery storage has enormous potential for residential power supply applications. However, the installation is often complicated with lots of wiring. The wireless power transfer (WPT) interface can greatly reduce the complicated wiring part, facilitating easier installation, with additional benefits like electrical isolation, lower maintenance cost, better reliability. However, rigorous proof-of-concept of WPT for LV household power supply still remains to be largely unexplored. This work fills the research gap by presenting application of contactless power transfer system with battery storage for the solar-powered low-voltage (LV) power supply. Various resonant topologies for inductive power transfer (IPT) are studied, and a complete theoretical model of an LCL compensated IPT system integrated with a battery energy storage system is presented. The voltage and current characteristics are investigated to understand the operation of the proposed integrated IPT system at LVDC level. The setup is first realized and analysed in details in simulation using MATLAB/Simulink. Hardware experiments proves the feasibility of the contactless power transfer capability at the high efficiency of the integrated IPT battery system. The results show that the proposed system can maintain a constant load voltage of 48 V for a load variation of around 25%, with an efficiency of 92% at 85 kHz switching frequency.

A New Scheme for Parallel Transmission of Power and Full-Duplex Mode Information Sharing with LCC Topology Based on IPT System

In this study, a full-duplex data communication module is designed and developed for sharing information in a contactless power transfer system. It is realized through LC tank circuits with an inductive power transfer (IPT) system. On both the transmitter and receiver sides, one LCC compensation topology is used. Since Phase Shift Keying (PSK) is less susceptible to error and power-efficient digital modulation techniques, this paper proposes to implement PSK digital modulation technique to data signal modulation for full-duplex communication in a wireless EV charger. The proposed scheme ensures stability, transfers load status, charging level, and emergency messages between the source and load sides of the system, and vice versa. The results are compared with the Amplitude Shift Keying (ASK) digital modulation technique. Further, the impedance-based model is developed to analyze the interference between the power and high-frequency information signals. The inductive power and data transfer (IPDT) prototype is developed in the laboratory and results show that the data rate reaches 288 kbps when 46.6 W of power is transferred from source to load.

Modeling the optimal compensation capacitance of a giant magnetostrictive ultrasonic transducer with a loosely-coupled contactless power transfer system

Modeling the optimal compensation capacitance of a giant magnetostrictive ultrasonic transducer with a loosely-coupled contactless power transfer system

Multi-focal transmission acoustic phase holograms in contactless ultrasonic power transfer systems

Using a pre-designed, simple, and cost-effective acoustic hologram alongside a single ultrasonic transducer, as an acoustic source/transmitter, enables new capabilities in multi-focal focusing, acoustic patterning, and contactless ultrasonic power transfer (UPT), to selectively charge sensors/receivers. In this work, different multi-focal holograms are designed that cover single- to four-focus acoustic patterning for UPT purposes. The holograms are numerically designed to create multi-focal pressure patterns in a target plane where an array of receivers are placed. The incident sound wave from a transmitter, after passing through the hologram, is manipulated, hence, the output field is the desired pressure field, which excites the receivers located at the pre-determined focal points more significantly. Proof-of-concept experiments are also performed for a five-element receiver setup, using a two-focus hologram, to selectively power two specific receivers. The experiments indicate a significant electrical average power output enhancement ratio of 23.4 from the targeted receivers, compared to untargeted ones, which proves the functionality of the designed multi-focal holograms in arbitrarily patterning the contactless transfer of ultrasonic power.

Design and Analysis of a Multi-Input Multi-Output System for High Power Based on Improved Magnetic Coupling Structure

Conventional inductive contactless power transfer (ICPT) systems have only one energy transmission path, which makes it challenging to meet the power transmission requirements of high-power and reliability. This study proposes a novel multiple-input multiple-output (MIMO) ICPT system. The three-dimensional finite element analysis tool COMSOL is utilised to study various magnetic coupling structures, analyse the influence of cross-coupling between coils on the same side, design the circuit based on this, propose a parameter configuration method for resonance compensation, and, finally, build an experimental platform with small magnetic coupling structures for single-input single-output systems (SISO) and MIMO systems. The results indicate that the co-directional connection of the coils of the E-shaped and UE-shaped magnetic coupling structures has a strengthening effect on the secondary side coupling. The magnetic coupling structure of the E-shaped iron core exhibits the best transmission performance. The transmission power of the MIMO system with the E-shaped magnetic coupling structure as the core device is significantly improved. In addition, the output power is unchanged after a secondary side fault, which verifies the accuracy of the proposed method.

Transferring power and data simultaneously of different direction in ultrasonic contactless power transfer system

Ultrasonic contactless power transfer (UCPT) technology is a new kind of contactless power transfer (CPT) technology, which can be used to transfer power to loads in enclosed metal containers. In this paper, an UCPT system of transferring power and data simultaneously of different direction using only one pair of transducer is proposed. In the proposed system, power is transferred from the transmitting side to receiving side, and data is transferred in reverse direction simultaneously, from receiving side to transmitting side. The proposed system consists of power transfer channel and data backward transfer channel. The power transfer channel is modeled and the data backward transfer channel is analyzed in detail. 2ASK technology is used in data transfer channel. To show the effectiveness of the proposed system, an experimental setup is built. For power transfer channel, the output power is up to 40 W, and for data transfer channel, the data transfer rate is up to 1.6 kbps in ideal situation. When transferring a picture, the data transfer rate is 1.43 kbps and the output voltage is 5V which are realized at the same time.

Design, Manufacture, and Test of a Rotary Transformer for Contactless Power Transfer System

In traditional applications such as machine field excitation, where power transfer from stationary to rotary side is needed, contact slip rings are often adopted. However, this kind of slip ring is easy to wear and needs frequent maintenance. In a contactless power transfer system, mechanical slip rings can be removed which will largely increase the system reliability. In this article, a contactless power transfer device using wireless power transfer (WPT) is designed. Its performances are simulated by finite-element method. To increase the system power rate and efficiency, the device is operated under high frequency. Thus, high-frequency ferromagnetic materials and Litz wires are used. Moreover, compensation circuits are added to improve the coupling between the primary and secondary sides. At last, a prototype is built and tested. From the experimental results, the functions and performances of the device are well verified.

Electrochemiluminescence of Tris(2,2'-bipyridine)ruthenium(II)/Tri-n-propylamine with an Electric Contactless Power Transfer System.

An electrochemiluminescence (ECL) analytical device was developed using an electric contactless power transfer system. A mutually induced electromotive voltage was generated by wrapping an enameled wire around a commercial contactless charger. There was no electrical contact between the power supply and the electrochemical cell. For the tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+)/tri-n-propylamine system, a weak ECL signal was observed. When an inexpensive rectifier diode was introduced between the coil and the working electrode, the ECL intensity detection sensitivity increased by more than 100 times. The relationship between the waveform of the applied voltage and the ECL response was clarified, and the optimum conditions were determined. The intensity of the induced electromotive voltage was easily controlled by changing the number of turns in the coil. The proposed method is a safe, simple, and inexpensive technique without electrical contact.

A Multilevel Inverter for Contactless Power Transfer System

In contactless power transfer (CPT) system, voltage-source inverters are widely used with a resonant tank. However, because of the influence of the working environment, aging, and other factors, the resonant frequency of the primary varies. Moreover, the reflected equivalent impedance of the secondary coil may affect the design of a resonant tank with a constant switching frequency. In this brief, a multilevel inverter (MLI) without the resonant circuit tuning is proposed for the CPT system. The proposed inverter can produce a high-frequency ac voltage with an approximated sinusoidal envelope for the primary coil. According to the equation developed for the inverter, low-order harmonics can be eliminated by selecting an appropriate input voltage ratio and switching angles for the switches. Furthermore, the cancelation of multiple harmonics can be achieved by designing multilevel circuits. The advantages of the proposed MLI include the reduction in low-order harmonics, low voltage stress, and high reliability. Hardware experimental results were obtained for a CPT system prototype to verify the performance of the proposed MLI.

Investigations with Various Inner Shielding Distance Tests for a Novel Coupler-based CPT System Applied for Electric Vehicles Using Electromagnetic Resonant Coupling and Aluminium Shielding Material

Contactless power transfer (CPT) technology development has been driven rapidly over the past decade by the world-wide trends towards new energy explorations, and numerous reports have been presented in this area. This paper focuses on passive magnetic shielding, which acts as one of the major factors mainly determining the overall CPT system performance when discussing electromagnetic field flux distribution and its real-time effects on magnetic resonant coupling. As a well performance conductive metallic material, aluminium has been adopted to be a passive shielding material in the designed novel H-shape coupler CPT system in this paper, in order to evaluate and find out the optimal inner shielding distance in between the coil and the inner shielding shell. Three inner shielding distances are applied and analyzed across a critical range of system operating frequency, by which the actual CPT system performance differences from perspectives of electromagnetics and power electronics have been illustrated and compared. As a result, it can be noticed that the 15-mm inner shielding gap CPT model is able to yield an optimal system performance with a maximum system efficiency, peak system output RMS power of over 36% and 22 kW, respectively, which also shows an optimal capability to address major concerns over electric vehicle contactless charging. Besides, along with the electromagnetic field parameters generated in the model, such as actual real-time values of flux linkage, magnetic flux density and field strength, it can be found that the 15-mm inner shielding gap prototype is able to achieve better overall magnetic field performance than 5-mm and 25-mm inner shielding distance CPT models.

Dynamics of acoustic impedance matching layers in contactless ultrasonic power transfer systems

The acoustic impedance mismatch between transducer materials and medium in ultrasonic power transfer systems narrows the transduction bandwidth and causes losses through the back reflection of progressive pressure waves at the boundary between the transducers and medium. Capturing both resonances and losses due to impedance mismatch of interwoven elements is essential for advancing the development of these systems. We present a unified approach, based on the multiplication of a sequence of transfer matrices, to determine an equivalent acoustic impedance. The analytical model couples the properties of the transmitter and receiver with multiple matching layers and a single classical quarter-wave layer in controlled setups with the objective of minimizing reflections through acoustic impedance mismatch alleviation. Losses due to ultrasonic attenuation in the material layers and medium are also considered. The acoustic field at the receiver location constitutes the input to the coupled electro-elastic equations of the fluid-loaded and electrically-loaded piezoelectric receiver. Experiments are performed to identify the input acoustic pressure from a cylindrical transmitter to a receiver disk operating in the 33-mode of piezoelectricity. The results show significant enhancements in terms of the receiver’s electrical power output when implementing a two-layer matching structure. We present the results showing non-dimensional wave number variations versus characteristic impedance, which can be used to calculate the materials’ thicknesses for acoustically matching ultrasonic power transfer systems to an acoustic medium of interest at any desired resonant frequency while considering any type of glue or epoxy as the bonding layer. The derived physical models facilitate the development of high-fidelity matched systems with enhanced contactless power transmission.

A Novel Coupler Design and Analysis with Shielding Material Tests for a CPT System of Electric Vehicles Based on Electromagnetic Resonant Coupling

In this paper, a contactless power transfer (CPT) system using a novel geometrically enhanced energy transfer coupler with three different shielding materials has been built and analysed, along with the evaluations from aspects of electromagnetics and RMS power transmitting based on electromagnetic resonant coupling. A CPT system design improvement with the proposed H-shape ferromagnetic cores and the combined semi-enclosed passive electromagnetic shielding methods have been investigated in terms of generated electromagnetic field characteristics, system power transfer ratings, system efficiency optimization and performances of shielding materials. The results have shown that, across the range of operating frequency of the CPT system, aluminium shielding as a metallic material method could deliver better overall CPT system performance than other two ferromagnetic materials, steel 1010 and ferrite. In addition, the coupler prototype design limitations, misalignment tolerance and the passive shielding design considerations including distance between windings and inner surfaces of shielding shells have been discussed.

Design and Analysis of a Novel CPT System with Soft Ferromagnetic Material Cores and Electromagnetic Resonant Coupling for Evs

This paper describes a novel contactless power transfer (CPT) system with geometrically improved H-shape ferromagnetic cores and electromagnetically prospective modelling analysis methods for wireless power transmitting (WPT) applications of electric vehicles (EVs). A CPT prototype, using optimized H-shaped magnetic couplers and series-to-series (SS) compensation, is proposed to address and ensure the maximization of system efficiency, power transfer ratings, and air gaps of coupling coils. By focusing on the main factors such as various system operating frequencies, different geometric designs of coils, changeable inductive coupling distances, electromagnetic field performances and actual phase angle deviations when the inductive coupling system tends to be stable with its waveforms, this small-sized H-shape CPT system has been analytically considered and modelled in a finite-element method (FEM) environment, resulting in a maximum system efficiency of 59.5%, a coil transmitting efficiency of 83.8% and a maximum power output of 42.81 kW on the load end when the resonant coupling of CPT system tends to occur within a range of calculated resonant frequencies, with an air gap of 10 mm. Moreover, the system efficiency and coil transmitting efficiency can reach 47.75% and 77.22%, respectively, and the highest RMS real power to load can achieve 31.95 kW with an air gap of 20 mm. Besides, with an air gap of 30mm, this H-shape CPT system is measured to output 20.39-kW RMS power, along with the maximum system efficiency and coil efficiency of 41.78% and 63.23%, respectively. Furthermore, the improvements of flux linkage, magnetic flux density regarding the actual electromagnetic performance produced and the issues on the calculated natural resonant frequencies have been studied by result analysis and comparison of electromagnetic field parameters generated. In addition, the current limitations and further design considerations have been discussed in this paper.

Analysis of a three-coil contactless power transfer system for high-power applications

ABSTRACTRecently, contactless power transfer (CPT) has become very popular in various fields of applications such as electronic appliances, medical implant devices, electrical vehicles, etc. When air gap distance between the transmitting and receiving coils of a CPT system increases, coupling coefficient between the coils decreases. In a large-air-gap CPT system, by incorporating an additional coil between the transmitting and receiving coils, coupling coefficient can be enhanced. Consequently, efficiency of a large-air-gap CPT system is improved. In this study, a three-coil system has been compared with a two-coil system using basic circuit models. Thereafter, the basic circuit models of two-coil and three-coil systems have been studied to confirm energy efficiency differences between the two systems for high-power applications. Using simplified circuit models, conditions for higher energy efficiency of a three-coil system than a two-coil system have been derived and it has been established that power transfer efficiency of a three-coil system has improved significantly in comparison with a traditional two-coil system. To confirm the theory, a two-coil and a three-coil systems with an air gap distance of 18 cm and a lateral misalignment of 3.5 cm have been verified using Ansys simulation tool for an output power of 2 kW.

Acoustic holograms in contactless ultrasonic power transfer systems: Modeling and experiment

Contactless ultrasonic acoustic energy transfer (UAET) is a new technology that eliminates risks or impracticalities associated with wired electrical connections or batteries that need to be replaced on a regular basis. This technology, which is based on the reception of acoustic waves at ultrasonic frequencies by piezoelectric receivers, can be used to wirelessly charge low-power electronics. The execution and efficiency of this technology can be significantly enhanced through patterning and focusing of the transmitted acoustic energy in space to simultaneously power distributed sensors or devices. This work investigates the use of an acoustic hologram to create a multifocal pressure pattern in a plane where target receivers are located at specific focal points or regions. First, a phase-shifting hologram is designed using an iterative angular spectrum approach. Then, a multi-physics acoustic-electro-elastic model is presented for an axially vibrating cylindrical transmitter used to power multiple piezoelectric receivers, in conjunction with the hologram. Experiments are also performed to show the capability of an acoustic hologram to selectively power an array of the receivers. Both analytical and experimental results show a dramatic enhancement of power transfer to receivers exposed to a multi-focal pressure pattern created by the hologram. As a case study, a bi-focal receiver setup is investigated where one receiver is targeted. The UAET simulation predicts a doubling of the power transfer to the targeted receiver, which is verified by the proof-of-concept experiment. The effects of system parameters such as input frequency and hologram aperture size are also reported.

Finite element analysis of multi‐turn magnetoplated coils using homogenization method

AbstractMagnetoplated wires (MPW) are effective to reduce eddy current losses in power devices such as converters and contactless power transfer systems. In the conventional finite element analysis (FEA) of MPW, elements must be sufficiently smaller than the skin depth. This results in large number of unknowns. This article proposes a homogenization method using complex permeability for FEA of magnetoplated coils so as to circumvent this problem. The coil impedances obtained by the proposed method with coarse elements are shown to agree well with those computed in the conventional FEA with fine elements.

Circuit Analysis and Characterization of Contactless Power Transfer System with Variable Impedance

SUMMARYA contactless power transfer system using a repeater coil (repeater Coil topology) has been proposed as a method of suppressing overcurrent without power control during misalignment or no‐load. By installing a repeater coil between the primary and secondary coils, it is possible to increase the input impedance in the case of misalignment of the secondary coil or no‐load condition. In addition, another contactless power transfer system using primary parallel and secondary series resonance capacitors (PS capacitor topology) has been proposed. In the PS capacitor topology, the input impedance can be increased during misalignment of the secondary coil or no‐load condition similar to the repeater coil topology. In this paper, we evaluated the characteristics of both these topologies. First, we conducted a circuit analysis of the repeater coil topology and proposed a design method. In addition, we theoretically clarified the characteristic difference of the two topologies and experimentally evaluated the characteristics.

Contactless Power Transfer System for AGVs

This paper presents a contactless power transfer system for automatic-guided vehicles (AGVs). The system can replace batteries and, therefore, can improve the operation ratio and load capacity of an AGV. The contactless power transformer in this system was designed to enhance the mutual inductance between the primary and secondary. The secondary involving a diode rectifier was modeled to an equivalent circuit, which takes voltage drops across the diodes into account. Based on the model, an optimal primary current control technique maximizing the transfer efficiency was derived. Contactless power transfer tests to the AGV using a prototype of the contactless power transformer were conducted. It is confirmed that the power transfer over 100 W with transfer efficiencies of 80% can be achieved. Furthermore, it is confirmed that the proposed control technique can improve the system efficiency during AGV drive operation.

A new circuit topology using Z-source resonant inverter for high power contactless power transfer applications

Abstract In this study, a new circuit topology using a Z-source resonant inverter (ZSRI) for high power applications in large-air-gap contactless power transfer (CPT) systems, has been investigated. The main shortcoming of a large-air-gap CPT system is the poor power transfer efficiency due to low magnetic coupling. In order to minimize this shortcoming and to improve the overall performance of the system by boosting the power transfer capability, in this paper a CPT system with the newly developed circuit topology using high frequency Z-source resonant inverter has been proposed. Using the newly developed circuit topology for the CPT system, it has been observed that the overall performance of the system has been improved to a reasonable level with a purely sinusoidal resonant current flowing through the primary side. Therefore, no harmonics will be injected into the source. The proposed CPT system with an air gap of 16 cm and a misalignment of 3 cm has been simulated using the Maxwell finite element tool and Simplorer circuit simulation software for an output power of 2 kW.

Contactless power transfer system for low power medical devices

Currently, contactless power transfer system is being implemented to power up the medical devices. Those medical devices can either power by transcutaneous cable or batteries. However, the power driven for medical devices via transcutaneous cable might lead to infection due to breach on the skin. The battery replacement surgery for cardiovascular patients also can lead to infection. Therefore, a contactless power transfer system is effectively solving the problem by transmitting power in a safe and non-invasive manner and has mitigate effect to patient health, yet efficient in the power transmission process. Magnetic coupled resonant is being designed since magnetic field cannot be shielded by biological tissues. Resonant power transfer technique can minimize the power scattering on the non-resonant objects such as human body. Impedance matching technique is utilized to improve the overall power transmission efficiency. The system consists a pair of transmitter and receiver coil, transmitter and receiver circuit, and a pair of transformer as impedance matching purpose. The system is capable to achieved a transfer efficiency of over 60%. Contactless power transfer technology does offer the advantages of safety, non-invasive and no significant effect on patient health. Eventually, bacterial infection on the skin breach is prevented.