Wireless Charging Of Electric Vehicles Research Articles

Evolution of Hybrid Inductive and Capacitive AC Links for Wireless EV Charging—A Comparative Overview

The inductive link in a wireless power transfer (WPT) system, fed by various high-frequency power converters with appropriate control strategies is widely accepted for medium power ( 95%) in static wireless charging scenarios. However, considering the dynamic wireless charging, the inductive link implementation for millions of kilometers is quite expensive due to the need for sophisticated resources. Therefore, relatively low-cost capacitive link, which initially focused on low power ( 90%) and significant misalignment tolerance. This paper aims to find the significant roles played by inductive and capacitive ac link designs in static and dynamic expansion of wireless electric vehicle (EV) charging. Through a relative analysis, this paper emphasizes the need for mutual promotion of these ac links as a hybrid system in order to boost wireless EV charging technology.

Design and Interoperability Analysis of Quadruple Pad Structure for Electric Vehicle Wireless Charging Application

The power pad coil design is one of the most significant traits for wireless charging of electric vehicle charging applications. The proper design of the power pad is the most critical phase of developing an efficient and reliable wireless power transfer system. Each available coil design has its advantages suitable for specific applications. In this paper, the two objective problems of optimization are discussed involving optimized design, shape, size, and optimized current directions in subsquare structures of quadruple power pad structures. The dimensional design optimized to least area with maximum coupling coefficient, and current directions with least interference between corresponding coils were verified through finite-element analysis (FEA) using ANSYS Maxwell. The results were thoroughly compared among all the cases discussed. The other aspect of this paper is the compatibility analysis of quadruple coil structure with the rectangular, double D (DD), and double D quadrature (DDQ) coil structures. Results have been compared, and the quadruple coil structure is verified as compatible with all other coil structures.

A Coil Detection System for Dynamic Wireless Charging of Electric Vehicle

Application of wireless power transfer while an electric vehicle (EV) is in motion can significantly reduce the battery storage capacity. A major challenge in implementation of dynamic wireless power transfer (DWPT) is an automatic detection of EV to avoid loss in efficiency and alleviate any safety concerns. This paper proposes a novel coil detection method for segmented DWPT. Detection of the EV ahead of its arrival will initiate energizing of the transmitter buried inside the road to enable just-in-time transfer of power. At low speeds, communication can be a reliable method to power up the transmitter coil. However, at high speeds on highways, the communication latency time for the detection of an EV is long and hence impractical. This paper proposes a low-cost and low-power EV detection system based on a novel orthogonal coil arrangement to detect EVs traveling at high speeds. The proposed detection system was tested on a laboratory scale prototype for verification purpose. For high-speed verification, simulation in PLECS was conducted to test the functionality of the proposed system.

CLL/S Detuned compensation network for electric vehicles wireless charging application

<span lang="EN-GB">An electric vehicle (EV) can be charged wirelessly through an inductively coupled power transfer system where the system resonates the inductive coupling coil at the operating frequency by means of a compensation network. However, the resonant behaviour implies overcurrent in the inverter MOSFETs during uncoupled and high load resistor conditions, which affect to the inverter MOSFETs failure whenever the current exceeds their maximum current rating. Therefore, this paper presents a CLL/S detuned compensation network for EV wireless charging application to limit the inverter current during the uncoupled state and open circuit load conditions. The proposed compensation consists of a series capacitor and parallel inductor at the primary side and series capacitor at the secondary side. By using Kirchhoff Voltage Law (KVL) analysis, the primary side is detuned to inductive behaviour to ensure zero voltage switching (ZVS), and the secondary side remains at natural resonant tuning. From the simulation analysis, the slight increase of the parallel inductor value at the primary side can limit of the inverter current at uncoupled and high load resistor conditions. The proposed system also offers higher efficiency than the series-series detuned compensation and slightly lower than the double-sided LCC compensation network at different coupling factor.</span>

A New Wireless EV Charging System With Integrated DC–DC Magnetic Element

A dc–dc conversion stage is commonly used for a wireless electric vehicle (EV) battery charging system. The dc–dc stage requires a bulky inductor to charge the battery either in constant voltage (CV) or constant current (CC) modes. In this article, a new magnetic structure for the wireless EV charging system is proposed to integrate the dc–dc inductor with the receiver coil on the vehicle side. The proposed structure utilizes the existing core material in the wireless power circuit pads and provides a more compact design and an efficient wireless charger system for EV applications. The proposed magnetic structure is modeled in 3-D, and the finite-element analysis (FEA) results are presented and compared with measurements. Moreover, the effect of the proposed integration method on the wireless charging system performance is investigated, and the results are presented. A 3.3-kW/85-kHz wireless charger is optimally designed and built to evaluate the proposed configuration. Furthermore, the efficiency and the output voltage of the wireless charging system are also measured and compared with the simulation results. The simulation and experimental results show the performance of the proposed structure.

Design and Performance Analysis of Pads for Dynamic Wireless Charging of EVs using the Finite Element Method

Increasing problems of air pollution caused by petrol-fueled vehicles had a positive impact on the expanded use and acceptance of the electric vehicles (EVs). Currently, both academic and institutional researchers are conducting studies to explore alternative methods of charging vehicles in a fast, reliable, and safe way that would compensate for the drawbacks of the otherwise beneficial and sustainable EVs. The wireless power transfer (WPT) systems are now offered as a possible option. Another option is the dynamic wireless charging (DWC) system, which is considered the best application of a WPT system by many practitioners and researchers because it enables vehicles to increase their driving ranges and decrease their battery sizes, which are the main problems of the EVs. A DWC system is composed of many sub-systems that require different approaches for their design and optimization. The aim of this work is to find the most functional and optimal configuration of magnetic couplers for a DWC system. This was done by performing an investigation of the main magnetic couplers adopted by the system using Ansys® Maxwell as a finite element method software. The results were analyzed in detail to identify the best option. The values of the coupling coefficients have been obtained for every configuration examined. The results disclosed that the best trade-off between performance and economic feasibility is the DD–DDQ pad, which is characterized by the best values of coupling coefficient and misalignment tolerance, without the need for two power converters for each side, as in the DDQ–DDQ configuration.

Review of inductively coupled power transfer for electric vehicle charging

Inductively coupled power transfer (ICPT) is a technology that is implemented to charge electric vehicles (EVs) wirelessly. Some developments from the past years indicate that this promising charging method has the potential to replace wired charging methods. Thus, some aspects of designing ICPT need to be discussed and considered to develop an optimal system. However, most reviews from the previous articles focused on the developments of ICPT systems in the scope of EV charging. This study not only reviews current developments and topical issues and challenges in high-power ICPT systems, but also presents several techniques for analysing the system as well as further developments for wireless EV charging adapted from the other electromagnetic field applications. This study will assist readers to analyse any proposed ICPT systems using current methods of analysis and to tackle highlighted topical issues presented from the previous technical papers.

Full-Duplex High-Speed Simultaneous Communication Technology for Wireless EV Charging

This letter presents a novel simultaneous wireless power and data transmission (SWPDT) system for wireless electric vehicle (EV) charging. The data carrier is injected and extracted by a plug-and-play toroidal-core inductor. Two data carriers of 5 and 6.25 MHz are adopted to achieve bidirectional and full-duplex communication using frequency-division multiplexing. Differential quadrature phase-shift keying modulation is achieved by a Class-E amplifier in the data transmitter. An analog switch circuit is designed to demodulate the data carrier in the data receiver. The proposed method is verified by a prototype that achieves up to 64 kbps full-duplex data transmission under 3.3 kW power transfer. The bit rate and interference immunity of data transmission are greatly improved compared to the reported SWPDT systems, which makes it possible to realize high-speed simultaneous communication in the kilowatt-level wireless EV charging.

A Phase Synchronization Technique Based on Perturbation and Observation for Bidirectional Wireless Power Transfer System

For the bidirectional wireless electric vehicle charging system, when both the primary and secondary converters are active, the phase synchronization between the two converters are necessary to control the power flow direction. This article proposes a new phase synchronization method by tracking the maximum (or minimum, depending on the power flow direction) value of the output current, without auxiliary hardware or the real-time communication between the primary and secondary sides. First, the relationship between the output current and the phase difference of the control signals is derived. It is found that the maximum output current is determined by the relative phase-shift angle (time interval between the middle points of the primary and secondary voltages) and the internal phase-shift angles of the two converters (time interval when the output voltage equals to the dc-link voltage). Second, a new scheme for generating the control signals is proposed to ensure that the relative phase-shift angle is not influenced by the internal phase-shift angles. Third, based on the perturbation and observation method, a procedure is proposed to track the extreme value of the output current and obtain the target relative phase-shift angle for the phase synchronization state. Moreover, the relationship between the internal phase-shift angle and the transfer power is derived to regulate the magnitude of the transfer power, with the dead-time effect taken into consideration. Finally, experimental results verify the validity of the proposed method with different air gaps and power levels. The method is easy to be implemented, helpful for the optimal operation of the static and quasi-static wireless charging system and suitable for the bidirectional power flow.

Survey on magnetic resonant coupling wireless power transfer technology for electric vehicle charging

Wireless power transfer (WPT) technology makes it possible to supply power through an air-gap, without the need for current-carrying wires. One important technique of WPT technology is magnetic resonant coupling (MRC) WPT. Based on the advantages of MRC WPT, such as safety and high power transfer efficiency over a long transmit distance, there are many possible applications of MRC WPT. This study provides a comprehensive, state-of-the-art review of the MRC WPT technology and wireless charging for electric vehicle (EV). A comparative overview of MRC WPT system design which includes a detailed description of the prototypes, schematics, compensation circuit topologies (impedance matching), and international charging standards. In addition, this study provides an overview of wireless EV charging including the static wireless EV charging and the dynamic wireless EV charging, which focuses on the coil design, power transfer efficiency, and current research achievement in the literature.

A New Method for an Electric Vehicle Wireless Charging System Using LCC

A New Method for an Electric Vehicle Wireless Charging System Using LCC

Performance Estimation of Wireless Electric Vehicle Charging System Based On Magnetic Coupling

In order to achieve an efficient wireless Electric Vehicle (EV) charging system in non-ideal practical scenarios, a proper design guideline has been delineated through the simulation, theoretical calculation as well as experimental investigation. It is examined that the wireless power transfer efficiency (WPTE) is invariably affected by the configuration of the charging coils (coil radius & number of turns), coupling to loss ratio, ohmic loss, radiation resistance, operating frequency, magnetic coupling as well as physical air gap between the coils. It is found that there is a certain operating regime at which maximum WPTE can be uphold. The acquired results provide a comprehensive strategic plan that can be used in EV charging system.

Symmetric Sensing Coil Design for the Blind-Zone Free Metal Object Detection of a Stationary Wireless Electric Vehicles Charger

In this article, a simple and cost-effective symmetric sensing coil set to be used for the metal object detection (MOD) in a stationary wireless electric vehicle charger is newly proposed. Compared to the conventional nonoverlapping sensing coil using the magnetic field change detection method, the proposed symmetric sensing coil set design offers the considerable advantage of eliminating all blind zones, i.e., regions where metal is undetectable in the conventional method. Moreover, by reducing the number of layers to one, the fabrication of the proposed sensing coil is easier and more cost effective. The design of the proposed sensing coil is optimized for highly sensitive MOD based on a sensitivity equation and on the finite element method simulations. An experiment conducted with a metal object 40 × 40 mm2 in size and a 20 A transmitting (Tx) coil current verifies the reliability and the blind-zone elimination feature of the proposed sensing coil.

Interoperability study of fast wireless charging and normal wireless charging of electric vehicles with a shared receiver

Fast charging of electric vehicles (EVs) has been the trend recently. For conductive charging, normal charging can be realised by an on-board charger, while fast charging can be realised by a DC charger which is usually off-board the vehicle. However, for wireless charging, there is a need of a transmitter on the ground and a receiver on the EV side. Therefore, there will be a high-power receiver and a low-power receiver in one EV to achieve dual charging capabilities. To reduce the EV-side cost, weight, and volume, this paper proposes a wireless charging system with a shared receiver compatible of fast wireless charging (FWC) at a small air gap and normal wireless charging (NWC) at a large air gap. The relationship between the coil size and the power level is investigated and a suitable receiver coil size is selected for FWC. The LCC-LCC topology is selected due to its characteristic of output power proportional to the coupling coefficient. Design procedures of the receiver and transmitters are investigated. The simulations and the experimental results obtained from the downscaled prototype verified the effectiveness of the compatibility design.

Dynamic WPT system for EV charging with integrated energy storage

Wireless power transfer (WPT) can be used to charge electric vehicles (EVs) safely and efficiently. Dynamic wireless EV charging systems to charge EVs while moving has been developed but this technology is not yet widespread. One of the key challenges of dynamic charging is the pulsed nature of the transferred power, which may negatively impact battery life and the utility grid. Hybrid energy storage systems have been demonstrated as a potential solution, at the expense of a dedicated converter to interface with the energy storage element. This study presents a possible solution to the problem of adsorption and conditioning of high-power pulses, in the form of a novel converter topology that combines inductive WPT and super capacitor energy storage without the need for an additional converter stage. A suitable switching pattern is presented along with a steady-state mathematical model based on inductive power transfer, providing insight into the operation of the system. Experimental results of a prototype bi-directional WPT system are shown to validate the model and demonstrate the applicability of the proposed converter topology.

Three‐phase bi‐directional wireless EV charging system with high tolerance to pad misalignment

Electric vehicles (EVs), which are becoming increasingly popular, can be charged by either wired or wireless means. The latter, based on wireless power transfer (WPT) technology, is convenient and safe, but pad misalignment is one of the major concerns as it causes a reduction in charging power level, prolonging the charging process. Therefore, wireless charging systems with high tolerance to pad misalignment are necessary. This study proposes a three-phase bi-directional wireless power transfer (BD-WPT) system with a control scheme that offers high tolerance to pad misalignment in EV charging applications. The system uses simple coil designs for pads and utilises the magnetic coupling among pads to compensate for the power variation. A comprehensive mathematical model, incorporating all magnetic cross-coupling effects, is presented to investigate the charging performance of the system under pad misalignment and different pad spacings. To demonstrate the validity of the proposed system, theoretical and simulated results are presented, benchmarking against a single phase WPT system, and in comparison to a prototype 1.3 kW three-phase BD-WPT system. Results are convincing and indicate that the proposed three-phase BD-WPT system with small pad spacing is more tolerant to wide pad misalignment in EV charging applications.

TMR-Sensor-Array-Based Misalignment-Tolerant Wireless Charging Technique for Roadway Electric Vehicles

The wirelessly transferred power as well as charging efficiency will significantly drop due to the large misalignment between the transmitting coil and receiving coil for roadway electric vehicles (EVs). A low-cost and reliable misalignment-tolerant wireless charging technique is indispensable for the rapid commercialization of wireless EV charging. This paper presents a technique to achieve the misalignment-tolerant wireless charging for the dynamic wireless charging (DWC) system by means of a tunneling magnetoresistive (TMR) sensor array as well as the easy-to-fabricate receiving coils. The TMR sensor array provides the coil-misalignment position by measuring the magnetic field component generated from the transmitting coil. The corresponding receiving coils are selected to be in resonance according to the measured coil-misalignment positions. In this paper, a sensor array composed of 29 uniaxial TMR sensors was utilized to measure the magnetic field component. This effectiveness of the proposed technique has been validated by both the finite-element method (FEM) simulations and laboratory experiments. The experimental results demonstrated that the proposed misalignment-tolerant wireless charging system can operate in a relatively wide misalignment range of ±120 mm with charging efficiency higher than 76.2%.

Autotuning Control System by Variation of Self-Inductance for Dynamic Wireless EV Charging With Small Air Gap

In this paper, an autotuning control system (ACS), which utilizes the variation of self-inductance of a transmitter (Tx) coil caused by a ferrite core of a receiver (Rx), is newly proposed for the dynamic wireless electric vehicle (EV) charging. A Tx module consists of only passive elements that include a Tx coil, a partially compensated capacitor in series with the Tx coil, and a parallel compensation capacitor. All Tx modules share an ac bus line that passes the output filter of an inverter in parallel without any active switches. The current of the coupled Tx coil increases automatically without any manipulations such as controlling the power switches, sensing, or communication when the Rx module is approaching. Not only the system efficiency is increased by the reduction of the conduction losses from the uncoupled Tx modules, but control also becomes simpler because sensors are not required for detecting EVs, and the constant output voltage characteristics can be obtained. Through experiments, it was found that the proposed ACS is suitable for applications such as a tram that runs along an orbit with a small air gap, such as a train. The results showed that the current of a coupled Tx coil increased 11.6 times larger than that of an uncoupled Tx coil, at which time the dc–dc efficiency achieved was 88.4% for an output power of 766 W (10 Ω of load resistance) at the laboratory scale.

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.

Power Stabilization With Double Transmitting Coils and T-Type Compensation Network for Dynamic Wireless Charging of EV

Power fluctuation caused by the movement of the receiver has always been a difficult problem for the development of dynamic wireless charging of electric vehicles (EVs). A segmented dynamic wireless charging system (DWCS) based on double transmitting coils and T-type compensation network is presented in this paper to restrain the power fluctuation. Cross-coupling effects are removed by adding switches in series with the transmitting coils. A genetic algorithm based multiobject optimization for the power fluctuation factor (PFF) and the reactive component is used to design the parameters of the T-type network. Simulations show that the optimization of the T-type network is not limited to a certain structure of the transmitter and receiver coils but can minimize the PFF for different values of the gap between the transmitting coils. Experiments for separated and overlapped transmitting coils show that the proposed double-transmitting-coil power supply scheme T-type network can maintain the power fluctuation less than 6% of the average output power with the dc–dc efficiency above 85%.