Contactless Power Transfer Research Articles

Switched Compensator for Contactless Power Transfer Systems

Contactless power transfer systems require compensators to improve power factor degradation caused by significant leakage inductance in the contactless power transformer. The most commonly used compensators are LC series- and parallel-resonant compensators. In this paper, we present a comparison between the characteristics of the compensators with a focus on transfer efficiency. Based on these characteristics, a compensator capable of switching between the LC parallel- and series-resonant topologies is proposed, and its changeover algorithm is explained. The proposed compensator was experimentally examined and was found to perform efficiently over a wider range of output power than conventional LC resonant compensators.

Selection of semiconductor switches in high frequency inverter fitted contactless power transfer system for reducing input current distortion

This paper investigates the selection of semiconductor switches used in contactless power transfer (CPT) system. In the present paper a single phase high frequency full bridge inverter using different semiconductor switches like IGBT, MPOSFET and GTO has been considered. Harmonic injection in input current of the inverter for different semiconductor switches has been analyzed using PSIM software. The THD of input current of the inverter for the particular switching device has been determined by using Fourier Transforms. It has been observed that THD in case of the IGBT is minimised.

Wide-Air-Gap Transformer Model for the Design-Oriented Analysis of Contactless Power Converters

A wireless power converter topology with a small size and a high conversion efficiency has an increasing demand on small-power applications. Some design techniques to transmit power by customized cores have been already developed. However, when transferring energy by wide-gap transformers employing small-sized commercialized cores, the power losses on the winding greatly increase as the frequency increases. Then, the efficiency of the contactless power system decreases significantly due to the conduction loss and reactive components in the resonant circuit. Even though series-parallel resonant converters are largely employed, which can provide an infinite shunt impedance regardless of the coupling coefficient, when a commercialized core is employed for loosely coupled contactless power transfer applications, the large leakage inductance of the transformer significantly influences the additional power dissipation on the transformer windings. In this paper, an operating principle on how the contactless transformer with commercialized core contributes to the low efficiency is discussed. Also, a new frequency-dependent R- L ladder circuit model is introduced for the design-oriented analysis of wide-air-gap contactless power converters including the frequency-dependent losses of the transformer. A new design procedure with the proposed model is suitable for the contactless transformers employing commercialized cores. The proposed design approach is validated by 98.8-W hardware experiments. Finally, the simulation waveforms and the hardware results are compared to verify the accuracy of the frequency-dependent transformer model.

Parameter identification of BIPT system using chaotic-enhanced fruit fly optimization algorithm

Bidirectional inductive power transfer (BIPT) system facilitates contactless power transfer between two sides and across an air-gap, through weak magnetic coupling. Typically, this system is nonlinear high order system which includes nonlinear switch components and resonant networks, developing of accurate model is a challenging task. In this paper, a novel technique for parameter identification of a BIPT system is presented by using chaotic-enhanced fruit fly optimization algorithm (CFOA). The fruit fly optimization algorithm (FOA) is a new meta-heuristic technique based on the swarm behavior of the fruit fly. This paper proposes a novel CFOA, which employs chaotic sequence to enhance the global optimization capacity of original FOA. The parameter identification of the BIPT system is formalized as a multi-dimensional optimization problem, and an objective function is established minimizing the errors between the estimated and measured values. All the 11 parameters of this system (Lpi, LT, Lsi, Lso, CT, Cs, M, Rpi, RT, Rsi and Rso) can be identified simultaneously using measured input–output data. Simulations show that the proposed parameter identification technique is robust to measurements noise and variation of operation condition and thus it is suitable for practical application.

Contactless DC Connector Based on GaN LLC Converter for Next-Generation Data Centers

An inductively coupled contactless dc connector has been proposed for the next-generation 380-V dc distribution system in data centers. A LLC resonant dc–dc converter topology with gallium nitride (GaN) power transistors has been applied to realize the short-distance highly efficient contactless power transfer. A prototype of a 1.2-kW 384- to 192-V connector has been fabricated and the conversion efficiency of over 95% with the power density of $8.1 \hbox{W}/\hbox{cm}^{3} $ has been confirmed experimentally under 1000-kHz operation. The design consideration has been carried out and the potential to achieve $10.0 \hbox{W}/\hbox{cm}^{3} $ has been also shown taking the feature of the GaN power device and the characteristics of the magnetic core material for the transformer into account. The contactless dc connector integrates the functioning of an isolated dc–dc converter into a connector for space saving, and the dc current can be cut off without arc because of the inductive coupling. The proposed connector contributes to realizing a highly efficient, space saving, and reliable future 380-V dc distribution system.

Neural Networks Based PID Control of Bidirectional Inductive Power Transfer System

Inductive power transfer (IPT) systems facilitate contactless power transfer between two sides and across an air-gap, through weak magnetic coupling. However, IPT systems constitute a high order resonant circuit and, as such, are difficult to design and control. Aiming at the control problems for bidirectional IPT system, a neural networks based proportional-integral-derivative (PID) control strategy is proposed in this paper. In the proposed neural PID method, the PID gains, $$K_{P}$$KP, $$K_{I}$$KI and $$K_{D}$$KD are treated as Gaussian potential function networks (GPFN) weights and they are adjusted using online learning algorithm. In this manner, the neural PID controller has more flexibility and capability than conventional PID controller with fixed gains. The convergence of the GPFN weights learning is guaranteed using Lyapunov method. Simulations are used to test the effective performance of the proposed controller.

Design Consideration and Efficiency Comparison of Wireless Power Transfer With HTS and Cooled Copper Antennas for Electric Vehicle

The wireless power transfer (WPT) technology based on strongly resonance coupled method realizes large power charg- ing without any wires through the air. Recently, the WPT systems have started to be applied to the wireless charging for electri- cal vehicles (EVs) because of their advantages compared with the wired counterparts, such as convenience, safety, and fearless transmission of power. However, it has obstacles to commercialize such as delivery distance and efficiency. To solve the problems, we proposed the technical fusion using a high-temperature super- conducting (HTS) antenna in the WPT system, which is called superconducting WPT for electric vehicle (SUWPT4EV) system. Since the superconducting wire has the merits of a larger current density and higher Q value than a normal conducting wire, the HTS antenna enables to deliver a mass amount of electric energy in spite of a small-scale antenna. To apply copper-stabilizer HTS (GdBCO) coil for EV charging system practically, the transfer efficiency characteristics for the HTS wires should be investi- gated. In this study, we examined transfer characteristics with copper-stabilizer HTS antenna at 77 K and copper antenna at 77 K, respectively. The transfer distance is at 30 cm, and RF power of 370 kHz below 500 W is adopted. Moreover, in order to improve the transfer efficiency, the design considerations for the SUWPT system were described. Index Terms—Cooled copper antenna coil, electric vehicle, electromagnetic resonance coupling, high-temperature supercon- ducting (HTS) antenna coil, superconducting contactless power transfer.

A Method for Designing a High‐Power Contactless Power Transformer Considering Reactive Power

SUMMARYProblems in high‐power contactless power transmission systems using series and parallel resonance capacitors arise from the maximum voltage limit of the series capacitor due to high reactive power. In this study, the characteristics of the reactive power are analyzed using an equivalent circuit and a contactless power transfer system is designed with the reactive power characteristics taken into consideration. The self‐inductance and the frequency can be used to determine the distribution of reactive power on the primary side and the secondary side. In addition, the optimal winding number, size of the coil, and the appropriate frequency are investigated through electromagnetic field analysis.

An Embedded Control System for CPT Based on ARM9

Hardware design and programming of an embedded control system for CPT (Contactless Power Transfer) is proposed in this paper. Embedded control system for CPT is realized based on ARM9 chip, Linux operating system and MiniGUI graphic technology.

Analysis and Control of Series/Series-Parallel Compensated Resonant Converter for Contactless Power Transfer

Series/series (S/S) and series/parallel (S/P) compensations are widely used in contactless power transfer systems. However, the inductive input impedance of the S/S compensated converter operating at an output voltage gain intersection point impairs the system’s efficiency, and the output voltage of the S/P compensated converter operating at resonant frequency is quite sensitive to variation of transformer’s parameters caused by air gap change or misalignment. This paper proposes a novel series/series–parallel (S/SP) compensation topology to achieve both high efficiency and good output controllability. The frequency-domain and time-domain analyses of the proposed resonant converter are performed in this paper. Similar to the conventional resonant converters, both phase-locked-loop (PLL) control and fixed-frequency control can be employed. A 60-W prototype with PLL control and a 1.5-kW prototype with fixed-frequency control are built to verify the theoretical analysis. To perform the input-to-output voltage gain comparison, an S/P compensated converter is also fabricated. Experimental results verify the effectiveness of the proposed compensation method. The efficiency of the fabricated S/SP prototype reaches 95.2% at an output power of 1.5 kW with a 10-cm air gap between windings.

High-Efficiency Contactless Power Transfer System for Electric Vehicle Battery Charging Application

In this paper, a contactless charging system for an electric vehicle (EV) battery is proposed. The system consists of three parts: 1) a high-frequency power supply from a full-bridge inverter with frequency modulation; 2) a loosely coupled transformer that utilizes series resonant capacitors for both the primary and secondary windings; and 3) a rectification output circuit that uses a full-bridge diode rectifier. With carefully selected compensation network parameters, zero-voltage switching can be ensured for all the primary switches within the full range of an EV battery charging procedure, which allows the use of low ON-state resistance power MOSFETs to achieve high-frequency operation and system efficiency. The design of loosely coupled transformer is simulated and verified by finite element analysis software. For a 4-kW hardware prototype, the peak dc–dc efficiency reaches 98% and 96.6% under 4- and 8-cm air gap conditions, respectively. The prototype was tested with an electronic load and a home-modified EV to verify the performance of constant current and constant voltage control and their transitions.

A Review of Contactless Electrical Power Transfer: Applications, Challenges and Future Trends

Methods of contactless electrical power transfer technologies have been surveyed and results are presented here. In this among, the inductive based contactless electrical power transfer systems are investigated in more detail. The principles, structures and operations of the systems as well as their methods presented in the literature are reviewed and their applications are explored. Also, current challenges and opportunities and future trends are noted. An effective index is proposed to compare different contactless power transfer systems describing their present statuses and the future trends. Finally, some remarks and recommendations regarding future studies are proposed.

同軸円筒形空芯トランスを用いた電磁誘導方式非接触コンセント・プラグの特性評価

A contactless outlet for dc distribution systems was proposed. It uses an inductive contactless power transfer circuit with a Series/Parallel (S/P) compensation circuit to prevent voltage fluctuation. However, the output voltage of the circuit rises in light load conditions. In this paper, the main circuit and control method for reducing the rise in output voltage and a method to estimate the output voltage are presented. The proposed circuit and methods were verified and evaluated experimentally using feedback control.

無人搬送装置への非接触給電技術の導入

無人搬送装置への非接触給電技術の導入

A magneto-inductive wave wireless power transfer device

Magneto-inductive waves are a form of propagation which only exists in certain types of magnetic metamaterials formed from inductively coupled resonant circuits. We present an investigation of their potential as contactless power transfer devices capable of carrying power along a surface between suitably prepared terminals while simultaneously offering a broadband data channel. Input impedances and their matching conditions are explored with a view to offering a simple power system design. A device with 75% peak and 40% minimum efficiency is demonstrated and designs with potential for better than 70% mean and 90% peak are reported. The product of planar magnetic coupling and metamaterial cell Q factor is determined to be a key optimization parameter for high efficiency.

Design of an Improved Type Rotary Inductive Coupling Structure for Rotatable Contactless Power Transfer System

This paper is aimed at analyzing the rotary inductive coupling structure of contactless rotary transformer. The main feature of the proposed rotatable contactless power transfer system is which winding is coaxial-interlayered for improving the magnetic coupling capability. There is no ferrite core used in the secondary-side of the rotary inductive coupling structure, this helps to ease the exerted force that is stress by the secondary-side on spindle. In order to verify the feasibility of the proposed contactless power transfer system for rotary applications, an inductive powered rotary machinery and the control system have been integrated. The experimental results show that the maximum power transfer efficiency of the proposed rotary inductive coupling structure is about 94.8%. The maximum output power received in the load end is 1030 W with transmission efficiency of 88%.

Proposal of a New Disk-Repeater System for Contactless Power Transfer

The authors propose “Disk-repeater” as a new structure alternative to the conventional resonator repeater. Disk-repeater has a simple structure comprised of just copper plates and wire, non-resonant structure. First, coupling coefficients are measured as functions of disk diameter and wire length to characterize the basic performance of Disk-repeater. It is explained by several experimental evidences that Disk-repeater and resonator are not magnetically coupled but electrically coupled. It is also shown that the transmission distance extends dramatically longer than that of conventional resonator repeater. Further, two-dimensional arrangement, where multiple disks are connected, shows very high efficiency and uniform transmission characteristic regardless of positions of receiving resonator. Disk-repeater gives possibility of unprecedented versatile application with the simple structure.

Modelling of Traversal of Airgaps Using Resonant Inductive Coupling

A contactless power transfer system at high frequency incorporating strong coupling between primary and secondary coils is very widely in mobile phones to replace the plug and socket charging. The primary and secondary coils coupled using resonant inductive coupling is modelled using compensation capacitors in the primary and secondary coupled circuits. Theoretical analysis of the system is presented and operating power transfer efficiency under varying conditions of source and load is derived. The model presents the variations in the contactless system for all possible variations in the parameters. Simulated results performed using Matlab at 600 kHz are presented.

Multi-Resonant Compensation Analysis of Contactless Electrial Power Transfer System

The loose coupling structure of Contactless Electrical Power Transfer System (CEPTS) is the main cause of transmission inefficiency. Compensation capacitors were calculated and mounted on both sides of primary and secondary coils which forming the following four compensation topologies: primary secondary series (SS compensation), primary series-secondary parallel (SP compensation), primary parallel-secondary series (PS compensation) and primary secondary parallel (PP compensation). Experiment results show that the transmission efficiency differs according to different compensation topologies. SP structure is the most efficient among these four topologies and the transmission efficiency of SP structure is about 40% higher than that of basic structure without compensation.

Design and characteristic investigations of superconducting wireless power transfer for electric vehicle charging system via resonance coupling method

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.