Wireless Charging Of Electric Vehicles Research Articles

Compensation Parameters Optimization of Wireless Power Transfer for Electric Vehicles

For wireless charging of electric vehicles (EVs), increasing the output power level is particularly important. In this paper, the purpose of improving the output power while maintaining optimal transmission efficiency is achieved by optimizing the parameters of the compensation topology under the premise that the coupled coils of the system does not need to be redesigned. The series-series (SS) and hybrid-series-parallel (LCC, composed by an inductor and two capacitors) compensation topology are studied. The influence factors of load resistance to achieve optimal efficiency, the influence of LCC compensation parameters on the power output level, and the influence of parameter changes on system safety are analyzed. Theorical results show that by rationally designing the LCC compensation parameters, larger output power and optimal transfer efficiency can be achieved under different load resistance by adjusting the inductances of the primary and secondary compensation circuits. The output power of the optimized system with adjusted LCC compensation topology is increased by 64.2% with 89.8% transfer efficiency under 50 ohms load in experiments. The correctness and feasibility of this parameter design method are verified by both theorical and experimental results.

Foreign Object Debris Detection and Automatic Elimination for Autonomous Electric Vehicles Wireless Charging Application

<div>Power pad designing, misalignment reduction, safety, automation, living object detection (LOD), and foreign object debris (FOD) detection are the key challenges in the commercialization of the high voltage wireless charging of Electric Vehicles (EV). The interruption from unwanted and sensitive foreign objects such as metal objects and living objects over the charging pads is an immense challenge for the static wireless charging of EV. In this manuscript, the problem of interference due to foreign objects and living objects has been analyzed, and an innovative laser- and sensor-based FOD detection method is proposed and verified by developing a prototype setup. Modeling and analysis of the effects of foreign objects have been performed using Finite Element Analysis (FEA) in Ansys Maxwell® environment. The analysis compares the consequence of the presence of foreign objects on the wireless charging power pad. The proposed method utilizes laser light and sensor for the detection and two-dimensional signal processing for the elimination of FOD. The proposed method is compatible with all types of static wireless charging systems without interrupting the power transfer and power circuit. The proposed system has been analyzed and compared with the various available FOD detection techniques. The feasibility of the proposed system has been assessed with the help of an on the bench hardware prototype implementation in the lab environment.</div>

Realizing Constant Current and Constant Voltage Outputs and Input Zero Phase Angle of Wireless Power Transfer Systems With Minimum Component Counts

In both normal and fast wireless electric vehicle charging systems, constant current/constant voltage (CC/CV) charging profile, regardless of the variation of the battery state of charge, is one of the most essential characteristics to ensure the battery performance and reliability. The input zero phase angle (ZPA) is able to minimize the system volt-ampere rating, enhance the power transfer capability, and make it easy to achieve soft-switching operation over the full range of battery charging profile. Therefore, the load-independent CC and CV output characteristics with ZPA conditions are necessary for wireless charging systems. However, the existing methods that can achieve these functions either add power switches or need a large number of compensation components, which make the system inefficient, uneconomical, and bulky. In this paper, a unified resonant tuning configuration with minimum passive component counts is proposed to achieve CC and CV outputs at two ZPA operating frequencies. According to the proposed configuration, all the possible inductive power transfer (IPT) and capacitive power transfer (CPT) topologies are analogized. With these topologies, both CC and CV outputs with ZPA are achieved using a minimum number of compensation components and no additional power switches. Among all the simplest IPT topologies, a primary Series-secondary Series and Parallel (S-SP) compensation topology is illustrated to demonstrate the analysis.

Coil Positioning Based on DC Pre-excitation and Magnetic Sensing for Wireless Electric Vehicle Charging

This article proposes an accurate coil positioning method for the wireless charging system by sharing the primary coil to generate a dc magnetic field. Based on the research of the magnetic field and the discussion of the arrangement of magnetic sensors, the position equations containing core-placement coefficient G , which represents the effect of magnetic core on the field, are presented. An automatic identification of G is then proposed by judging the zero point of magnetic field, which can adapt to different charging pads. Furthermore, this article gives the flowchart of the positioning algorithm, comprising partitioning and noise suppression to improve the positioning accuracy. A large amount of samples distributed throughout the range of 20 × 16 cm are tested. The experimental results demonstrate that >97% of those samples have positioning errors of <2 cm. Besides, the proposed positioning system has been used in a 1-kW prototype for automatic changing of the compensation capacitance resulting in an improved misalignment tolerance.

A Double Helix Flux Pipe-Based Inductive Link for Wireless Charging of Electric Vehicles

This paper presents a novel inductive link for wireless power transfer (WPT) system of electric vehicles (EVs). The WPT technology uses an alternating magnetic field to transfer electric power through space. The use of the WPT technology for charging electric vehicle provides an excellent alternative to the existing plug-in charging technology. It has been reported that the inductive link using planar coils such as the circular and rectangular coil are capable of transferring a high power with high efficiency. However, they have a poor tolerance for lateral misalignment, thus their power transfer efficiency decreases significantly with the misalignment. Due to the poor misalignment performance of the planar coil topology, extensive studies have been carried out on the flux pipe topology due to their excellent misalignment tolerance. To address this, in this paper, a novel inductive link using double helix flux pipe topology is proposed. The performances of the inductive link using the proposed double helix flux pipe are analyzed and compared with inductive links using conventional flux pipe. The proposed model has excellent characteristics in terms of the power transfer efficiency and tolerance against misalignments. The proposed model is capable of transferring over 1.6 kW of power with a coil-to-coil efficiency of over 98.5% at a load resistance of 20 Ω.

Magnetic Positioning Technique Integrated with Near-Field Communication for Wireless EV Charging

For wireless electric vehicle charging, the relative position of the primary and secondary coils has significant impacts on the transferred power, efficiency and leakage magnetic flux. In this paper, a magnetic positioning method using simultaneous power and data transmission (SWPDT) is proposed for power coil alignment. Four signal coils are installed on the primary coil to detect the secondary coil position. By measuring the positioning signal amplitudes from the four signal coils, the power coil relative position can be obtained. Moreover, all the communication needed in the positioning process can be satisfied well by SWPDT technology, and no extra radio frequency (RF) communication hardware is needed. The proposed positioning method can work properly both in power transfer online condition and in power transfer offline condition. Thus, a highly integrated wireless charging system is achieved, which features simultaneous power transfer, data transmission and position detection. A positioning experimental setup is built to verify the proposed method. The experimental results demonstrate that the positioning resolution can be maintained no lower than 1 cm in a 1060 mm × 900 mm elliptical region for a pair of 510 mm × 410 mm rectangular power coils. The three-dimensional positioning accuracy achieves up to 1 cm.

Designing and demonstration of misalignment reduction for wireless charging of autonomous electric vehicle

Abstract One of the key challenges in the adoption of wireless charging for Electric Vehicles (EVs) is the misalignment between the power pads. This manuscript presents an intelligent alignment of the receiving coil to reduce the magnetic leakage between the coupling power pads. The proposed solution implicates sensors to detect the flux strength at the corners and the middle of the receiver coil. A two-dimensional control technique is used for positioning of the receiver coil controlled through the stepper motor driver and a controller circuit. An array of the Hall effect sensor is installed on the receiver to sense the flux, where sensor receiving the smallest flux will generate the least voltage. Further, the controller sends the command to shift the receiver coil to the direction of the sensor receiving highest flux. This manuscript evaluates and verifies the magnetic flux pattern at the maximum alignment position between the transmitter and the receiver using Finite Element Analysis (FEA) on Ansys Maxwell®. The proposed solution mitigates the flux leakage and improves the efficiency of the wireless power transfer. Theoretical analysis is performed and all the elements of the systems are briefly discussed and explained to develop the proposed system. The modeling and simulation results verify the advantage of proposed intelligent alignment.

Design of DD Coil With High Misalignment Tolerance and Low EMF Emissions for Wireless Electric Vehicle Charging Systems

In this article, a design method of the double-D (DD) coil aiming at high misalignment tolerance is proposed, and the electromagnetic field (EMF) shielding of the system is considered. Inspired by the DD coil recommended in the standard J2954 published by the Society of Automotive Engineers, the novel structures of the transmitting (Tx) coil and the receiving (Rx) coil are designed, respectively. First, the standard DD coil is introduced as a reference. Second, for the Tx coil, the parameters, such as length, width, and coverage, are investigated in detail. For the Rx coil, the coil structure overlapped in the edge is optimized. The purpose is to obtain a higher coupling coefficient at the maximum offset. Third, considering EMF emissions exceeding the limit, the structure of the central-depressed coil with E-shaped cores is proposed in the Tx coil. The EMF emissions can be reduced to less than 27 μ T at the rated output power. Finally, a 6.6–kW experimental system of which the maximum transmission efficiency is higher than 94% is set up. The experimental results prove that the proposed structure is beneficial to maintain a higher coupling coefficient against misalignment and suppress EMF emissions.

Evaluation and selection of shielding methods for wireless charging of e-rickshaw

High leakage magnetic fields are inevitable for wireless charging (WC) of electric vehicles (EVs), due to their large air gap. This high leakage magnetic field may cause adverse effects on human beings in the vicinity. So the design of coil system of WC system to satisfy the safety limits as well as performance is quite important. The electromagnetic fields exposure to human beings should be less than the safety regulations set by International Commission on Non-Ionizing Radiation Protection. Moreover, EVs’ chassis creates unwanted electrical load on the WC affecting the performance and can be improved through shielding of leakage magnetic fields as per the standards. The main focus of this paper is to first investigate the effectiveness of passive, active and resonant current loop shielding methods through finite element method approach considering asymmetrical circular spiral coils. Based on the outcomes, a passive shielding on the receiving side and inductive coil connected in series opposing configuration with transmitting coil have been proposed for the case of e-rickshaw. Accordingly, coil system is fabricated for the air gap of 12 cm and experimental evaluation is carried out.

«Умные» дороги с беспроводной зарядкой для электромобилей

«Умные» дороги с беспроводной зарядкой для электромобилей

Compact pulse position control‐based inverter for high efficiency inductive power transfer to electric vehicle

A compact high efficient inductive power transfer (IPT) topology based on pulse position control is proposed for wireless charging of electric vehicle. Near-field wireless charging is efficiently achieved by the resonance-enhanced IPT technique. The system sustains high power transfer efficiency under contingency in misalignment of pickup coil and load variations. The performance evaluation of the proposed system under the occurrence of anticipated perturbation in load and mutual inductance is studied numerically. Experimental results from the developed prototype corroborate the theoretical and simulated results discussed in the proposed study.

Equivalent-Circuit-Based Design of Symmetric Sensing Coil for Self-Inductance-Based Metal Object Detection

A symmetric sensing coil design is proposed and adapted for the self-inductance-based metal object detection (MOD) of wireless electric vehicle (WEV) charging. Compared to conventional non-symmetric sensing coils, the proposed sensing coil provides symmetric detection sensitivity and ease of manufacturing, pertaining blind-zone-free characteristics. Moreover, it is found that the design of the proposed symmetric sensing coil is very different from that of the symmetric sensing coil for conventional induced voltage sensing (IVS) based MOD method due to different principles of MOD methods. Therefore, an analysis based on a newly proposed equivalent circuit, is used to design a high sensitivity symmetric sensing coils, considering many aspects such as metal object covering, metal object size, and mutual inductance between sensing coils. Based on the analysis, an optimized sensing coil design created through a finite element method simulation is proposed to achieve highest sensitivity with the lowest number of sensing coils. It can be readily applied to a cost-effective MOD system that can be used for high-power WEV charging. Experiments on a metal object 20 mm $\times20$ mm in size with a 20Arms Tx current verified high detection sensitivity of 38% without any blind zones.

Design and Performance Evaluation for a New Power Pad in Electric Vehicles Wireless Charging Systems

The introduction of wireless charging systems for electric vehicles (EVs) is a revolutionary step in the field of electrified transportation. Misalignments between transmitting and receiving power pads significantly affect the overall power transfer efficiency of an EV wireless charging system. In this article, a new power pad named “double D circular” (DDC) is designed. To evaluate the proposed DDC power pad design, its performance is compared with that of the existing circular and double D (DD) power pads by analyzing the power transfer efficiency in the wireless charging system considering different vertical and horizontal misalignments between the transmitting and receiving power pads. We use physical dimensions published in the Society of Automotive Engineers (SAE) J2954 recommended practice for existing circular and DD power pads in the simulation software, ANSYS Maxwell 3D. The influence of ferrite plates on the performance of power pads is also evaluated in the article.

Transmitter Side Control of a Wireless EV Charger Employing IoT

This paper presents a transmitter side control scheme for a series-series compensated wireless power transfer (SS-WPT) system for electric vehicle (EV) charging applications. The proposed control scheme matches the reflected load impedance, by controlling accordingly the front-end dc-dc converter (FEC) of the SS-WPT system. The proposed control scheme drives the FEC, through an optimizer which takes into account the misalignment but also the operational conditions of the system to achieve high efficiency throughout the entire charging process – regardless the EV type, the misalignment conditions or the on-board charger. The novelty of the proposed optimizer lies upon its universal characteristic, which makes it compatible to various SS-WPT topologies. As such, the proposed charging concept is a universal solution, which optimizes the system efficiency regardless the receiver side on-board charger topology (single-stage or double-stage), technical characteristics or control scheme that implements the charging profile. Finally, for the necessary communication between the transmitter and the receiver sides, the Internet of Things (IoT) is employed, offering a low-cost and flexible solution that overcomes compatibility problems between wireless antennas. Simulation and experimental results validate the feasibility of the proposed control scheme, highlighting the efficacy of the proposed wireless charging process.

Metal Object Detection in a Wireless Power Transfer System Based on Double-Layer Symmetric Sensing Coils

The intrusion of a metal object into a wireless charging system could cause safety issues, such as temperature rise and even combustion. This paper proposes a double-layer symmetric sensing coil design for metal object detection (MOD) of wireless electric vehicle charging to prevent the detection blind area. First, the magnetic effect and the eddy current effect of a metal object in high-frequency magnetic fields are analyzed. Second, the principle of the proposed double-layer symmetric sensing coils is detailed. Finally, the finite element simulation is implemented in order to test the performance of the proposed sensing coil design. The simulation results show that the proposed double-layer symmetric sensing coils can effectively detect the presence and position of the metal object simultaneously.

Modeling and Analysis of Thermal Characteristics of Magnetic Coupler for Wireless Electric Vehicle Charging System

The operating temperature of the magnetic coupler in wireless power transfer (WPT) systems for electric vehicles (EVs) determines the system reliability and service life. This paper studies the modeling and analysis of temperature characteristics of a general magnetic coupler. Firstly, a thermal circuit model is established to show the heat transfer of the magnetic coupler in the air. Secondly, the heating mechanism of the coil, core and aluminum (Al) shield plate is studied. The thermal power of each component is calculated, and the temperature distribution is qualitatively given based on the proposed thermal circuit model. Then, the temperature distribution of each component is simulated, and the results are consistent with the theoretical analysis. Finally, a 6.6 kW WPT prototype is set up, and the temperature of each component is measured after 30 minutes of operation. The temperature of the coil, 34.6 °C, is the highest among that of the coil, core, Al plate and coil base. The agreement between experimental results and the theoretical simulation results shows that the thermal field simulation can accurately predict the temperature of the magnetic coupler by reasonably setting the thermal power addition method.

Experimental Investigation and Optimal Air Gap Selection for Electric Vehicles Wireless Charging System

The interest for Electricals Vehicles (EV) wireless charging system has been increasing due to its simplicity of operation, robustness, and safety. The focus of this paper is on the presentation of an equivalent electrical circuit of the inductively coupled power transfer (ICPT) system. This paper proposes a new method to obtain an easier calculation of the ICPT system output power. The present method is based on the Thevenin equivalent circuit. For improving the performance of ICPT system, a relationship between the mutual inductance, the resonance frequency and the equivalent load resistance has been demonstrated in detail. This formula has been used to select the optimal air gap among transmitter and receiver coils. A prototype of a wireless charging system has been built using two rectangular coils. The resonant frequency of the designed system with a 50×20 cm transmitter coil and a 20×10 cm receiver coil is 10 kHz, and the maximum efficiency of the system is 86% at optimal air gap. Finally, the experimental results of the proposed system are presented and analyzed.

Analysis and Introduction of Effective Permeability with Additional Air-Gaps on Wireless Power Transfer Coils for Electric Vehicle Based on SAE J2954 Recommended Practice

The wireless power transfer (WPT) method for electric vehicles (EVs) is becoming more popular, and to ensure the interoperability of WPT systems, the Society of Automotive Engineers (SAE) established the J2954 recommended practice (RP). It includes powering frequency, electrical parameters, specifications, testing procedures, and other contents for EV WPT. Specifically, it describes the ranges of self-inductances of the transmitting coil, the receiving coil, and coupling coefficient (k), as well as the impedance matching values of the WPT system. Following the electrical parameters listed in SAE J2954 RP is crucial to ensure the EV wireless charging system is interoperable. This paper introduces a method for adjusting the effective permeability of the ferrite blocks in the standard model, to tune the self-inductance of the coils as well as the coupling coefficient. To guarantee the given values of the self-inductance of the coil and coupling coefficient matched those in the standard, we slightly modified the air-gap between the ferrite tiles in a specific region. Based on this method, it was possible to successfully tune the self-inductance of the transmitting coil and receiving coil as well as the coupling coefficient. The proposed method was verified by simulation and experimental measurements.

En route of electric vehicles with the vehicle to grid technique in distribution networks: Status and technological review

SummaryThe presence of electric vehicles (EVs) directly affects the low voltage electric distribution networks. This article depicts the anticipated problems that occurred when it draws power from grid to vehicle in the charging scenario and critically analyze EV as dynamic storage while feeding the power grid in the discharging status (vehicle to grid). The merits and demerits by deploying the mass integration of EVs into the distribution network are comprehensively investigated. Moreover, the challenges of integrating renewable energy resources and deployment of EVs, for the efficient, reliable, and uninterruptible power flow are covered. The future scopes of electric mobility industry including wireless EV charging, vehicle to home, cloud to home charging are also highlighted. This comprehensive review is highly beneficial for the research community and design engineers working in this area.

A family of compensation topologies for capacitive power transfer converters for wireless electric vehicle charger

A large scale of electric vehicles can ideally maintain the stability of renewable power supply by acting as storage buffers for alleviating the intermittence in the integration of renewable energy sources for constructing a low-carbon energy system. However, the inconvenient conductive charging becomes a barrier in the popularization of electric vehicles. Wireless power transfer technology is in the spotlight because of the flexibility and convenience in powering electric vehicles. Recently, the Capacitive Power Transfer has received extensive attention due to simple coupler structure, rotatable coupler, and negligible heating of the metal foreign object. In the capacitive-based wireless charging system, the higher-order compensation topology is essential to enhance power transfer capability limited by the small coupling capacitance. However, with the increase of the resonant elements, the form of the resonant network becomes diverse. Currently, the researches focus on the characteristics of specific symmetrical compensation topologies. This paper presents a family of compensation topologies for the Capacitive Power Transfer system to achieve constant-voltage or constant-current output. A design procedure is summarized to construct the resonant networks, so as to design the compensation parameters. Considering the coupling capacitor variations caused by parking position deviation, a parameter tuning method is proposed to realize primary zero-voltage switching by adjusting the parameter of the double-sided inductor-capacitor-inductor-capacitor compensation topology. Experiments show that the prototype achieves constant-current output and zero-voltage switching when the coupling capacitance varies. The system efficiency reaches 93.57% at 1.5 kW input power with the input and output voltage around 250 V.