High-power Wireless Power Transfer System Research Articles

Evaluation of Electromagnetic Exposure in Wireless Power Transfer Systems for Electric Vehicles

In wireless power transfer (WPT) systems, the electromagnetic fields generated by a charging module may exceed the limits set by international safety guidelines. This is a matter of concern for the safety of users of high-power WPT systems, such as electric vehicles (EVs). To address this issue, this study designed a stationary WPT system for EV charging. Furthermore, the dosimetry of the system was evaluated for two exposure scenarios. Electromagnetic field data obtained using the electromagnetic field analysis tool were employed to derive the induced quantities in the human body using the impedance method. In addition, the obtained results were compared to the values recommended by international guidelines (International Commission on Non-Ionizing Radiation Protection).

Thermal analysis for foreign objects in high-power wireless power transfer systems

PurposeThis paper aims to present a fast and modular framework implementation for the thermal analyses of foreign metal objects in the context of wireless power transfer (WPT) to evaluate whether they pose a hazard to the system. This framework serves as a decision-making tool for determining the necessity of foreign object detection in certain applications and at certain transmitted power levels.Design/methodology/approachTo assess the necessity of implementing foreign object detection, the considered WPT system is modeled, and Arnoldi-Krylov-based model order reduction is applied to generate separate reduced models of the ground and vehicle modules of the WPT system. This enables interoperable evaluations to be conducted. Further discussion on the implementation details of the system-level simulations used to evaluate the electrical and thermal characteristics is provided. The resulting modular implementation allows for efficient evaluation of the thermal behavior of the wireless charging system at various transferred power levels and under various boundary conditions.FindingsBased on the transferred power level, the WPT model, the relative positioning between the vehicle and the charging pad and the charging time, it may be necessary to divide the area of the charging pad into multiple regions for the purpose of implementing foreign object detection.Originality/valueWhile the tools and fundamentals of thermal analysis are widely known and used, their application to high-power WPT systems for electric vehicles has not yet been thoroughly discussed in this form in the literature. The approach presented in this paper is not limited to the specific WPT model discussed but rather is directly applicable to other WPT models as well.

A Multi-Inverter Multi-Rectifier Wireless Power Transfer System for Charging Stations With Power Loss Optimized Control

Electric vehicles (EVs) with different output power levels can use wireless power transfer (WPT) systems. Different vehicle assemblies (VAs) may be charged by different ground assemblies (GAs) in charging stations. However, the overall efficiency of the WPT system may drop significantly when the power class difference between GA and VA is large. To address this issue this paper proposes a DC-link parallel AC-link series (DPAS) multi-inverter multi-rectifier (MIMR) architecture for high-power WPT systems. Modulation, power transfer capability, and power sharing from the design aspects are investigated. A detailed power loss analysis and an easy-to-implemented power loss optimized control method based on mutual inductance identification are presented in this paper. Finally, experimental results are obtained from a 20-kW LCC-LCC WPT system to validate the analysis and proposed system operation.

A Multi-Inverter High-Power Wireless Power Transfer System With Wide ZVS Operation Range

Conventional high-power wireless power transfer (WPT) systems that are required to deliver power over a wide operating range suffer from issues like hard switching, poor current sharing, and unwanted cross-coupling issues. This article proposes a new resonant inductor integrated-transformer-based multi-inverter to improve the WPT power rating without compromising performance. Viable modulation schemes of the proposed system are analyzed, and a hybrid modulation scheme is proposed for wide-range power regulation. To further investigate the feasibility of the proposed system, the power transfer capacity, current sharing among multiple inverters, and the soft switching regions are studied. A 14-kW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> WPT experimental system with three parallel inverters is built, which achieves 93.5% efficiency, demonstrating the high performance of the proposed system. This article is accompanied by a video demonstrating these experiments.

On-Road Efficient Wireless Charging System for Electric Vehicle

With the growing popularity of Electric Vehicles (EVs), the need for a simple and robust charging scheme has become necessary. Consumers are dissatisfied with the typical recharging method at home or in station parks because it takes a long time to recharge. On a highway, waiting for a place to recharge the vehicle is not always a good idea. The super-fast recharge station has received positive feedback from drivers in terms of charging time; nevertheless, this is not always recommended, particularly in terms of battery security and durability. WPT (Wireless Power Transfer) technology has many inherent advantages over traditional means of power transfer. It has been proposed for use in a wide range of applications, ranging from low power biomedical implants (several watts) to electrical vehicle chargers (several kilowatts) to railway vehicles (several megawatts), with efficiency up to 95% or higher in some prototype systems. Capacitive coupling, magnetic coupling, frequency resonance matching, microwaves, lasers, and ultrasound waves are all methods for transferring electric power across a specified distance through air. However, resonant magnetic coupling appeared to be the most practical and promising method to date, with resonant magnetic coupling being used in the majority of medium to high power WPT systems constructed to date. In this project, a wireless charging system for lightweight electric vehicle is designed, built and tested. The problem with electrical vehicles is that it requires too much time to recharge the battery. Dynamic Charging could be the much anticipated concept that replaces the conventional method of charging of battery and reduces the time taken to change the battery. A solution to directly charge EVs as they travel along the highway will eliminate the two biggest barriers, travelling range anxiety and cost. This project is carried out using MATLAB Simulink software for simulation of the circuit. This project based on future infrastructure of EV’s technology.

Design of High-Power Static Wireless Power Transfer via Magnetic Induction: An Overview

Recent years have witnessed the booming development of wireless power transfer (WPT) via magnetic induction, which has the advantages of convenience, safety, and feasibility to special occasions. WPT can be applied to electric vehicles and ships, where high-power WPT technology is required to shorten the charging time with the increasing battery capacity. This paper reviews the state-of-the-art development of high-power static WPT systems via magnetic induction. Selected prototypes and demos of high-power WPT systems are demonstrated with key transfer characteristics and solutions. Theoretical foundation of magnetically coupled WPT systems is analyzed and the maximum power capability of coils is derived. Compensation topologies suitable for high-power applications are discussed. Four basic planar coils, namely the bipolar coil, the square coil, the circular coil, and the rectangular coil, are simulated and compared. The state-of-the-art silicon carbide MOSFET development is introduced. The power electronics converters with power elevation techniques, including cascading, paralleling and inductive elevation, are investigated. Future development of high-power WPT systems is discussed.

Simulation-Assisted Design Process of a 22 kW Wireless Power Transfer System Using Three-Phase Coil Coupling for EVs

The objective of this paper is to study a 22 kW high-power wireless power transfer (WPT) system for battery charging in electric vehicles (EVs). The proposed WPT system consists of a three-phase half-bridge LC–LC (i.e., primary LC/secondary LC) resonant power converter and a three-phase sandwich wound coil set (transmitter, Tx; receiver, Rx). To transfer power effectively with a 250 mm air gap, the WPT system uses three-phase, sandwich-wound Tx/Rx coils to minimize the magnetic flux leakage effect and increase the power transfer efficiency (PTE). Furthermore, the relationship of the coupling coefficient between the Tx/Rx coils is complicated, as the coupling coefficient is not only dominated by the coupling strength of the primary and secondary sides but also relates to the primary or secondary three-phase magnetic coupling effects. In order to analyze the proposed three-phase WPT system, a detailed equivalent circuit model is derived for a better understanding. To give a design reference, a novel coil design method that can achieve high conversion efficiency for a high-power WPT system was developed based on a simulation-assisted design procedure. A pair of magnetically coupled Tx and Rx coils and the circuit parameters of the three-phase half-bridge LC–LC resonant converter for a 22 kW WPT system are adjusted through PSIM and CST STUDIO SUITE™ simulation to execute the derivation of the design formulas. Finally, the system achieved a PTE of 93.47% at an 85 kHz operating frequency with a 170 mm air gap between the coils. The results verify the feasibility of a simulation-assisted design in which the developed coils can comply with a high-power and high-efficiency WPT system in addition to a size reduction.

Modeling and Phase Synchronization Control of High-Power Wireless Power Transfer System Supplied By Modular Parallel Multi-Inverters

Modular parallel multi-inverters (MPMIs) with master-slave phase synchronization control is proposed for high-power wireless power transfer (WPT) where the MPMI output voltage phase is synchronized to suppress current circulation by compensating for the time delay of the slave inverters caused by signal propagation delay. Different power levels can be conveniently satisfied by flexibly adjusting the number of MPMIs. A modeling method based on the energy-amplitude and phase is developed and linearized to get the slowly changing phase variable and to analyze the system dynamic characteristics at its operating point. To achieve the required dynamic performance of the proposed model, the parameters of a PI controller are obtained by calculating the required settling time and overshoot of the closed-loop dominant poles. A 20.07 kW WPT prototype supplied by three MPMIs with an efficiency of 92.17% was designed and tested. Experimental results show that the proposed modeling method and controller design achieved both good performances of circulating current suppression and MPMIs output voltage phase synchronization.

Analysis and Design of kHz-Metamaterial for Wireless Power Transfer

This article proposes an optimal design of the kilohertz (kHz)-metamaterial for wireless power transfer (WPT) systems with comprehensive consideration of parameters of the metamaterial. Taking advantage of the left-handed characteristics, the transmission performance can be extensively enhanced when the resonance frequency of the WPT system coincides with the metamaterial. However, the frequency of the existing metamaterial is normally at the range of megahertz, which is not applicable to the high-power WPT system due to the frequency limitation of power switching devices. In view of this, this article carries out the quantitative analysis of the impact of key structure parameters on the frequency where the left-handed characteristic exists. In addition, a general design procedure is proposed to realize the negative permeability at the range of kHz. Finally, the simulated and experimental results are both given to verify the feasibility of the proposed design scheme and show significant meanings for the utilization of metamaterials in relatively high power-level applications, such as the in-flight wireless charging for drones.

Generalized Design Approach on Industrial Wireless Chargers

The paper briefly discusses the most important standards and regulations established for high-power wireless power transfer systems and introduces the main issues concerned with the conceptual design process. It analyses the electromagnetic design of the inductive magnetic coupler and proposes key formulas to optimize its electrical parameters for a particular load. The method applies to both the resistive load and the battery charging. It also suggests basic topologies for conceptual design of power electronics and discusses its proper connection to the grid. The proposed design strategy is verified by experimental laboratory measurement including analyses of the leakage magnetic field.

Analysis and Demonstration of a Dynamic ZVS Angle Control Using a Tuning Capacitor in a Wireless Power Transfer System

In this article, a dynamic zero-voltage switching (ZVS) angle control scheme on the wireless power transfer (WPT) system inverter is proposed by implementing a tuning capacitor. High-frequency (HF) and high-power WPT systems are desired in battery charging applications to reduce the battery charging time. Consequently, the power semiconductor devices are subjected to increased voltage, current, and thermal stresses. In this article, the switching losses in the primary-side inverter of a WPT system are suppressed by realizing the ZVS operation during the battery charging process. A dual-loop control strategy is proposed, which involves traditional phase shift control between the inverter phase legs to maintain constant-current (CC)/constant-voltage (CV) at the output and a tuning capacitor to dynamically tune the ZVS angle. The dynamic tuning of the ZVS angle ensures a minimum reactive power requirement from the input source and, therefore, helps to improve the overall efficiency of the system. Closed-loop simulations of the proposed control strategy are carried out using the piecewise linear electrical circuit simulation (PLECS) simulation software. The proposed control strategy is verified on a 10-W WPT prototype by performing the open-loop experimental validations. The maximum efficiency of the proposed control strategy is found to be ~ 87 % during the CC/CV charging modes. The improvement of ~ 10 % in the dc-dc efficiency is achieved with the proposed ZVS control strategy.

An FDM-Based Simultaneous Wireless Power and Data Transfer System Functioning With High-Rate Full-Duplex Communication

This article proposed a novel scheme integrating full-duplex communication into high-power wireless power transfer systems. The power and data are transferred through the same inductive link. A pair of coupling coils with taps are employed to omit the trap inductors that are widely employed in former simultaneous wireless power and data transfer (SWPDT) systems. The proposed scheme can reduce the system cost and size and improve the power transfer efficiency. The power and bidirectional data are transmitted using carriers of different frequencies. Frequency division multiplexing technique is utilized for full-duplex communication. The duplexer is carefully designed to separate the transmitted and received data signals. The circuit model of the system is built to analyze the power and data transfer performance. The crosstalk between the power and data transfer is also discussed. To improve the performance of data transfer, the method to determine the optimal coil tap position is proposed. A 300-W SWPDT prototype with a full-duplex data rate of 500 kb/s was built to demonstrate the feasibility of the proposed system.

A Three-Phase Single-Stage AC–DC Wireless-Power-Transfer Converter With Power Factor Correction and Bus Voltage Control

Wireless power transfer (WPT) technology has been a research and industrial hotspot with applications in many areas, such as wireless electric vehicle charging system that requires high power, high efficiency, and high power factor (PF). Usually, the power is drawn from a 50/60 Hz single-phase or three-phase ac power source. For a high power application, a three-phase ac source is commonly used. In this paper, a three-phase single-stage WPT resonant converter with PF correction (PFC) and bus voltage control is proposed to improve efficiency and power quality of three-phase input and reduce production cost and complexity for a high power WPT system. A T-type topology is applied as the common part to perform both the PFC and dc–dc WPT functionalities simultaneously. The proposed converter is much more advantageous than a conventional three-phase two-stage WPT converter with individual PF corrector. In addition, three-phase single-stage topologies have better power quality than single-phase single-stage topologies because zero-sequence components can be naturally eliminated.

Characteristic Analysis of Electromagnetic Force in a High-Power Wireless Power Transfer System

In order to explore the influence of the electromagnetic force (EMF) on the coupling mechanism in a high-power wireless power transfer (WPT) system, the characteristics of the EMF are investigated by theoretical calculation and simulation. The expressions of the EMF on the WPT structure with magnetic shielding are derived in time domain and frequency domain, respectively. The EMF is divided into Lorentz force and Kelvin force. The distribution and changing regularity of the EMF on the coil and the magnetic shield under different exciting currents are solved by the finite element model, and the harmonic of the EMF is analyzed in detail. The results show that the coil is subjected to the EMF in both radial and axial directions. The EMF on the magnetic shield is opposite to the EMF on the coil, and the force between the transmitting coil and the receiving coil is repulsive. The frequency of the EMF is twice that of the system resonant frequency. An experimental prototype is built to prove the correctness of the predicted characteristics. It is shown that the EMF should be carefully considered in the application of high-power WPT systems.

Single-Stage Wireless-Power-Transfer Resonant Converter With Boost Bridgeless Power-Factor-Correction Rectifier

Wireless power transfer (WPT) has drawn more and more attention and has many applications, such as wireless electric vehicle charging systems, which require high power, high efficiency, and high power factor. In this paper, a single-stage WPT resonant converter with bridgeless boost power-factor-correction (PFC) rectifier is proposed to improve efficiency and power quality of line input, and reduce production cost and complexity for high-power WPT system. The bridgeless single-stage topology is creatively proposed to apply in WPT system, which is much more advantageous than conventional two-stage WPT converter with individual boost PFC stage.

Compensation Topologies of High-Power Wireless Power Transfer Systems

Wireless power transfer (WPT) is an emerging technology that can realize electric power transmission over certain distances without physical contact, offering significant benefits to modern automation systems, medical applications, consumer electronics, etc. This paper provides a comprehensive review of existing compensation topologies for the loosely coupled transformer. Compensation topologies are reviewed and evaluated based on their basic and advanced functions. Individual passive resonant networks used to achieve constant (load-independent) voltage or current output are analyzed and summarized. Popular WPT compensation topologies are given as application examples, which can be regarded as the combination of multiple blocks of resonant networks. Analyses of the input zero phase angle and soft switching are conducted as well. This paper also discusses the compensation requirements for achieving the maximum efficiency according to different WPT application areas.

Wireless Power and Data Transfer via a Common Inductive Link Using Frequency Division Multiplexing

For wireless power transfer (WPT) systems, communication between the primary side and the pickup side is a challenge because of the large air gap and magnetic interferences. A novel method, which integrates bidirectional data communication into a high-power WPT system, is proposed in this paper. The power and data transfer share the same inductive link between coreless coils. Power/data frequency division multiplexing technique is applied, and the power and data are transmitted by employing different frequency carriers and controlled independently. The circuit model of the multiband system is provided to analyze the transmission gain of the communication channel, as well as the power delivery performance. The crosstalk interference between two carriers is discussed. In addition, the signal-to-noise ratios of the channels are also estimated, which gives a guideline for the design of mod/demod circuits. Finally, a 500-W WPT prototype has been built to demonstrate the effectiveness of the proposed WPT system.