Wireless Charging Of Electric Vehicles Research Articles

Electrical Interoperability Evaluating of Wireless Electric Vehicle Charging Systems Based on Impedance Space

In the commercialization process of wireless electric vehicle charging (WEVC), it is essential to ensure the interoperability between diverse WEVC systems due to the wide application of various coil configurations and compensation topologies. This paper proposes a novel electrical interoperability evaluation method based on impedance indices and corresponding feasible space in the complex plane. Firstly, the electromagnetic description of the coil system is introduced to reveal the energy flow process of WEVC system. Further, two key impedance indices and their feasible space are derived and verified. Interoperability evaluation results show that the reference devices in Chinese WEVC standard GB/T 38775.6 and GB/T 38775.7 are able to achieve the requirements of power capability. Moreover, it is necessary to reduce the duty cycle of rectifier when the battery voltage rises so as to narrow down the variation of load resistance and avoid dangerous working conditions. The proposed method can effectively evaluate the electrical interoperability of WEVC systems from different manufacturers under different power or distance levels before conducting experiments.

Wireless Charging Efficiency Optimization Method Based on Adaptive Robust Control

This paper designs, analyzes and optimizes the electric vehicle wireless charging system and its control method. Compared with the traditional plug-in conduction charging, wireless charging is more convenient, safe, reliable and has better environmental adaptability. Inductive power transmission technology (IPT) is the main technology for wireless charging of electric vehicles and plug-in hybrid vehicles. Based on the fundamental approximation method, the critical self inductance of the primary or secondary coil is derived in this paper. This critical value reflects the power transmission capacity and control performance of the two chargers when they are interoperable. Compared with the non integrated structure, the magnetically integrated LCC compensated wireless charging system can transmit the same power with smaller compensation inductance. Based on the voltage dependent dynamic state space model, four working modes of magnetically integrated LCC compensated wireless charging system are studied in this paper. Simulation and experimental results show that the voltage dependent equivalent circuit model can be effectively applied to the basic characteristic analysis of wireless charging system. The voltage dependent dynamic state space model is more accurate and realistic. In addition to reflecting the basic characteristics of the wireless charging system, it can also reflect the working mode of the wireless charging system.

On the Asymptotic Behavior and Parameter Estimation of a Double-Sided LCC-Compensated Wireless Power Transfer System

This study investigates the statistic behavior and parameter estimation problems of a double-sided, LCC-compensated, wireless power transfer system. Based on the commonly used wireless charging circuit model, this study proposes a five-step parameter estimation method, which is applicable to automotive static wireless charging systems. The eight parameters in the circuit model of this study are the most important key components of the wireless charging system. The study also found that, under certain conditions, the statistic mode of wireless charging systems has a specific distribution. However, the current status of these eight components for wireless charging of electric vehicles will have complex parameter drift problems. These drift problems will deteriorate the performance of the vehicle power systems. This study probes these factors and proposes some related mathematical theories. The noted factors can be applied to the analysis of the wireless charging system and provide alternative solutions to explain the deteriorations from coil misalignments. Both simulations and experiments are given to show the evaluated issues of the proposed study.

Event-Driven Approach With Time-Scale Hierarchical Automaton for Switching Transient Simulation of SiC-Based High-Frequency Converter

On the emerging development of SiC MOSFET, the switching frequency of power converters has been pushed to the order of hundreds of kilohertz or even megahertz to improve power density. However, the state-of-the-art simulations for such high-frequency power electronics circuits are usually time-consuming, blocking the studies of long dynamics such as several seconds. What’s worse, adopting physical models to simulate the turn-on and turn-off transients leads to high stiffness and therefore convergence problems. In this paper, an event-driven approach is proposed to improve the solving speed and simulation stability of SiC based high-frequency converters. A time-scale hierarchical automaton is proposed to model the system, where piecewise analytical transient model for SiC MOSFET is established as the second layer in the automaton to simulate the switching transients with improved numerical stability. Simulation of the system is driven by discrete events in the automaton. A 3.3 kW 79.1 kHz wireless power transfer system for the wireless charging of electric vehicle is studied. Compared with ideal switch model in Simulink and physical switch model in LTspice, 60-fold and 400-fold increases in terms of simulation speed with same level of accuracy are achieved respectively. The simulated results are also attested to by experimental verifications.

An Optimized Design of an Electric Vehicle Wireless Charging Coupling Coil

With the development of electric vehicle wireless charging technology, the transmission power and transmission efficiency of electric vehicle wireless charging system have become the focus of current research. The transmission power and efficiency of wireless charging system largely depend on the energy loss of two resonant coupling coils. The energy loss is mainly related to the structural parameters of the coupling coil and the coupling coefficient of the two coils. On this basis, the structure of the coupling coil is designed and optimized by using the finite element analysis software Maxwell, and a new combined transmitting coil structure is designed. Experiments and verification show that the coil design meets the requirements of transmission efficiency, which can provide a reference for the design of wireless charging coil of electric vehicle in the future.

Research on Metal Foreign Object Detection of Electric Vehicle Wireless Charging System Based on Detection Coil

Due to the open structure of wireless charging systems, foreign objects are inevitably involved. In the process of energy transfer, the intervention of metal foreign objects will cause the system to deviate from the normal operating point and even cause safety accidents. Therefore, metal foreign objects detection (MOD) technology is of considerable importance. In this paper, a metal foreign object detection system of a wireless power transfer (WPT) system based on the symmetrical detection coil was designed, and a MOD method based on frequency scanning is proposed. The coil size of the WPT system was designed based on SAE-J2954 standard. In addition, the suitable detection coil was installed at the transmitting coil. The system model was established in ANSYS simulation software, and 5 cm × 5 cm copper sheet and iron sheet were used as the metal to be detected. The result shows that the self-induction of the detection coil at the position of the foreign object can achieve a fluctuation of 52.46% and −34.72%, and the resonant frequency of the detection system is offset by 24.7% and −18.82%, respectively. Finally, the experimental platform of MOD system was built, and the effectiveness of the system was verified.

Authentication and Billing for Dynamic Wireless EV Charging in an Internet of Electric Vehicles

Dynamic wireless charging (DWC) is a promising technology to charge Electric Vehicles (EV) using on-road charging segments (CS), also known as DWC pads. In order to ensure effective utilization of this on-the-road charging service, communication and coordination need to be established between the EVs and the different network entities, thereby forming an Internet of Electric Vehicles (IoEV). In an IoEV, EVs can utilize different V2X communication modes to enable charging scheduling, load management, and reliable authentication and billing services. Yet, designing an authentication scheme for dynamic EV charging presents significant challenges given the mobility of the EVs and the short contact time between the EVs and the charging segments. Accordingly, this work proposes a fast, secure and lightweight authentication scheme that allows only authentic EVs with valid credentials to charge their batteries while ensuring secure and fair payments. The presented scheme starts with a key pre-distribution phase between the charging service company (CSC) and the charging pad owner (PO), followed by a hash chain and digital signature-based registration and authentication phase between the EV and the CSC, before the EV reaches the beginning of the charging lane. These preliminary authentication phases allow the authentication between the EVs and the charging segments to be performed using simple hash key verification operations prior to charging activation, which reduces the computational cost of the EVs and the CS. Symmetric and asymmetric key cryptography are utilized to secure the communication between the different network entities. Analysis of the computational and transmission time requirements of the proposed authentication scheme shows that, for an EV traveling at 60 km/h to start charging at the beginning of the charging lane, the authentication process must be initiated at least 1.35 m ahead of the starting point of the lane as it requires ≃81 ms to be completed.

Multipurpose Flexible Positioning Device Based on Electromagnetic Balance for EVs Wireless Charging

The electric vehicles (EVs) have played an important role in people's traveling due to the clean energy and friendly environment. Considering the endurance issue of EVs, wireless charging is regarded as a convenient and effective solution. However, the charging power and the efficiency would be greatly affected when the transmitting coil (TC) and the receiving coils are nonaligned. In this article, we present a flexible and high-accuracy positioning device based on electromagnetic balance, which could automatically achieve wireless charging and two-level positioning without communication between TC and EVs during the location. Besides, a six-coil cross-coupled circuit model has been built to optimize the key parameters that affect the positioning accuracy. The theoretical analysis and experimental results show that the proposed structures and location method have certain advantages in positioning accuracy, operation complexity, and practicability. Within the range of first-level positioning, the accuracy could achieve 1 cm. There is a high fitting performance between the simulation and experimental results, which verify the correctness of the theoretical analysis and the validity of the structures. Moreover, an additional comparative experiment has been designed to verify the correctness of the proposed method used in the wireless charging positioning system with ferrite cores and a magnetic shielding layer.

An Si MOSFET-Based High-Power Wireless EV Charger With a Wide ZVS Operating Range

This article proposes a new digitized modulation scheme suitable for a high-power wireless electric vehicle charger employing an integrated boost multilevel converter (IBMC) as its primary-side converter. Using the proposed modulation scheme, an IBMC can generate a boosted square-wave-shaped ac voltage with a controllable amplitude, enabling it to regulate the power efficiently over a wide load and/or coupling range while achieving zero voltage switching for all switches. This article focuses on the steady-state operating principles of the proposed digitized modulation scheme. Key practical considerations, such as capacitor voltage balancing and semiconductor device selection, are highlighted. To verify the benefits of the proposed modulation scheme, an SAE J2954 WPT2/Z2 compliant wireless EV charger prototype that uses an IBMC as the primary converter is designed and built. 200 V Si MOSFETs are employed in the 12 submodules (SMs) that compose the IBMC. The secondary side employs a passive rectifier, and the power flow is controlled using only the IBMC. This system maintains an efficiency between 90% and 93% when regulating power transfer at 7.7 kW under a 220% variation in coupling factor (i.e., 0.14–0.31) and a 150% variation in battery voltage (i.e., 280–420 V).

Optimal Installation of the Power Transmitters in the Dynamic Wireless Charging for Electric Vehicles in a Multipath Network with the Round-Trip Case

Optimal Installation of the Power Transmitters in the Dynamic Wireless Charging for Electric Vehicles in a Multipath Network with the Round-Trip Case

Analysis of Dual Input Buck-Boost Converter for Solar PV Integration with Wireless Electric Vehicle Charger

Investigation of on-board renewable solar PV and wireless EV chargingstation integration is studied in this paper. Integration of on-board solar PVpower with EV charger power will reduce the stress on the grid without theneed for extra ground for solar plant installation. A dual-input buck-boostconverter (DIBBC) is used to integrate the two power sources and chargethe EV battery. A small-signal model of the converter is used to design thecontroller for three switches of the DIBBC. The simulation model of the inte-grated solar PV system and wireless power transfer (WPT) system is designedfor charging a battery of 120V/165Ah at 130V. The hardware prototype ofthe proposed EV battery charging system is designed for 1.5kW to verify thesimulation results. WPT system is developed for circular spiral-shaped coils,which are series-series compensated for 85kHz resonance frequency. SolarPV is replaced by a solar simulator programmed to operate with the samespecifications used in the simulation. Results and analysis of the DIBBCbased charger with charging voltage 130V showed higher efficiency up to 92% when both the sources are supplying power to DIBBC. The proposedcharging system gives better efficiency with higher source voltages and whenthe difference in power supplied by the two sources is less. Thus, highervoltage sources are beneficial for improving the efficiency of the integratedcharging system. Further, loss analysis in major components of the converteris discussed.

Design and Performance Analysis of Misalignment Tolerant Charging Coils for Wireless Electric Vehicle Charging Systems

In order to design a high efficiency Wireless Electric Vehicle Charging (WEVC) system, the design of the different system components needs to be optimized, particularly the design of a high-coupling, misalignment-tolerant inductive link (IL), comprising primary and secondary charging coils. Different coil geometries can be utilized for the primary and the secondary sides, each with a set of advantages and drawbacks in terms of weight, cost, coupling at perfect alignment and coupling at lateral misalignments. In this work, a Finite Element Method (FEM)-based systematic approach for the design of double-D (DD) charging coils is presented in detail. In particular, this paper studies the effect of different coil parameters, namely the number of turns and the turn-to-turn spacing, on the coupling performance of the IL at perfect alignment and at ±200 mm lateral misalignment, given a set of space constraints. The proposed design is verified by an experimental prototype to validate the accuracy of the FEM model and the simulation results. Accordingly, FEM simulations are utilized to compare the performance of rectangular, DD and DDQ coils. The FEM results prove the importance of utilizing an additional quadrature coil on the secondary side, despite the added weight and cost, to further improve the misalignment tolerance of the proposed inductive link design.

Ultrawideband (UWB)-based precise short-range localization for wireless power transfer to electric vehicles in parking environments.

As the necessity of wireless charging to support the popularization of electric vehicles (EVs) emerges, the development of a wireless power transfer (WPT) system for EV wireless charging is rapidly progressing. The WPT system requires alignment between the transmitter coils installed on the parking lot floor and the receiver coils in the vehicle. To automatically align the two sets of coils, the WPT system needs a localization technology that can precisely estimate the vehicle’s pose in real time. This paper proposes a novel short-range precise localization method based on ultrawideband (UWB) modules for application to WPT systems. The UWB module is widely used as a localization sensor because it has a high accuracy while using low power. In this paper, the minimum number of UWB modules consisting of two UWB anchors and two UWB tags that can determine the vehicle’s pose is derived through mathematical analysis. The proposed localization algorithm determines the vehicle’s initial pose by globally optimizing the collected UWB distance measurements and estimates the vehicle’s pose by fusing the vehicle’s wheel odometry data and the UWB distance measurements. To verify the performance of the proposed UWB-based localization method, we perform various simulations and real vehicle-based experiments.

Novel Output Regulation Method for Three-Phase Three-Level Wireless EV Charging System

Three-phase wireless power transfer (WPT) systems have compact coil structures, canceled triplen harmonics, and less dc -link current ripple, which are suitable for wireless electric vehicle (EV) charging systems. Most three-phase WPT systems are based on two-level inverters. Alternately, three-level (TL) inverters have the potential to further promote the performance of EV chargers by reducing the electromagnetic interference (EMI) and the voltage stress of power switches. However, the unbalance of the neutral point (NP) voltage is a problem for traditional TL inverters. This article proposes a TL three-phase WPT system for EV wireless charging, which is based on a T-type neutral point clamp (TNPC) inverter. The modeling, coil structure, and switching pattern of the proposed system are analyzed in detail. Furthermore, a novel output regulation method based on vector control is proposed for the WPT system. Also, a NP voltage balance strategy is proposed to enhance the reliability of the TL inverter. Both simulations and an experimental prototype based on SIC- MOSFET are given to verify the effectiveness of the proposed three-phase WPT system and control method.

Investigation of power transfer efficiency: utilizing different coil designs in wireless charging of electric vehicles

EV battery can be wirelessly charged by inductive coupling method between two electromagnetic couplers. In this study, the transmitter and receiver coils are designed. The effect of the number of turns for transmitter and receiver coils are studied. The results show that efficiency is decreased with the reduction of turns for both coils. Next, the spacing between each turn of coils is analyzed by 1mm of increasing for each simulation and the increased efficiency is only 2.6% for every 1mm spacing. Then, the power transfer efficiency is investigated for different coil designs. The efficiency can be improved with the proper consideration of air gap length, operation frequency, suitable coil designs and coil properties. Five coil designs such as circular, rectangular, double-D, double-D quadrature (DDQ) and bipolar designs are selected. The best design for maximum power transfer efficiency is DDQ design but the structure is complex since more wires are used in this design. The air-gap length between two coils is selected as 120mm and frequency is 85 kHz in this study.

Exciter–Quadrature–Repeater Transmitter for Wireless Electric Vehicle Charging With High Lateral Misalignment Tolerance and Low EMF Emission

In this article, an exciter–quadrature–repeater transmitter pad is proposed in order to achieve high lateral misalignment tolerance and low leakage flux emission in electric vehicle wireless charging applications. In the proposed WPT system, a single half-bridge inverter unit is needed to energize the exciter coil, which is magnetically coupled to two larger quadrature repeater coils. The currents in the two repeater coils naturally adjust based on the lateral misalignment of the receiver pad to reduce the leakage flux density around the charging zone. The system can maintain zero phase shift between excitation voltage and current and achieve constant current charging conditions with fixed compensation capacitors in the ±150-mm lateral misalignment range. In order to verify the attributes of the proposed wireless power transfer (WPT) system, a 3-kW experiment setup with a 200-mm vertical gap was built and compared to a three-coil WPT system, which consists of a small transmitter coil, a single large repeater coil, and a receiver coil. According to the experiment results, even under extreme 150-mm lateral misalignment, the proposed WPT system has 90.7% coil-to-coil transmission efficiency. Furthermore, it achieves a 30% reduction of leakage flux density compared to the three-coil system in the 150-mm lateral misalignment case.

An overview on Wireless Power transfer for Electric vehicles: Technology and its Status

Electric Vehicles (Evs) Will Be One Of The Possible Solution Future Transports,Which Is More Essential Due To The Environmental Concerns And Depletion Of OilResources. Conversely, The Technology And Facilities For Charging Is Lacking, And AlsoPossibility For The Owners Of The Cars To Forget To Plug In. Wireless Charging (WC) OfElectric Vehicles Using The Inductive Resonance Principle, Can Provide Automatic,Secured, And Effortless Charging Solution For Evs. WC Systems Paved A Path For On TheMove Charging Called As Dynamic Charging, Which Helps To Increase TheMileage/Charge, Reduce The Battery Size And Hence Vehicle Weight And Cost. In ThisPaper, Techniques Available For WC, Inductive Coupled Charging And Issues,Organizations & Institutes Involved In The WC Research And Their Status Are Reviewed.

An Inductive Coupler Array for In-Motion Wireless Charging of Electric Vehicles

An inductive power transfer (IPT) system is envisaged as the best solution to conveniently charge electric vehicles (EVs). While stationary IPT systems are becoming commercialized, significant research is being conducted to address the challenges related to dynamic IPT systems. Dynamic or in-motion IPT systems require a fully electrified roadway with embedded inductive couplers with accompanying circuitry. The large number of electronic components required, however, increases the system complexity, reducing the reliability and economic viability of dynamic IPT systems proposed to-date. This article proposes a simple yet robust push-pull driven coupler array (PPCA), aiming to decrease the number of switches required to drive the in-road couplers. This article is the first to report a configuration where only N+1 switches are required to independently energize N primary IPT couplers. Any number of couplers can be activated simultaneously in the array without proportionally increasing the current stress on the switches. A state-space model is developed and implemented in PLECS to investigate the efficiency and power transferred to an EV traveling over the proposed PPCA while considering the variation in the coupling and the self-inductances of the couplers. A 3.3-kW scaled prototype PPCA consisting of three primary couplers and two secondary couplers has been implemented to validate the performance of the proposed configuration.

Review and Comparative Analysis of Topologies and Control Methods in Dynamic Wireless Charging of Electric Vehicles

Dynamic wireless power transfer (DWPT) systems are developed as a solution to electric vehicle (EV) range limitations and battery size requirements. DWPT systems require careful consideration relative to dynamic variations in coupling for power flow control. With continued advances in development of different types of couplers, compensation, and converter topologies, the stability of control systems and lack of interoperability among different configurations remain significant challenges in the path toward commercialization of DWPT. This work provides a review of the existing coupler, compensation topologies, and control schemes to determine their effectiveness in achieving the desired control objectives. In addition, it introduces practical metrics for a system designer to consider when developing the magnetics and power electronics for a DWPT system to ensure good controllability. It also shows how the delay in communication can affect the control performance and impact recommendations for high-speed vehicle charging. The comparisons are performed and through simulations for the design of a 50-kW system using different topologies. The simulation results corroborate the guidelines developed for future designs of DWPT systems.

Coupled electromagnetic-thermal analysis of roadway inductive power transfer pads within a model pavement

Inductive Power Transfer (IPT) technology is a promising solution for wireless charging of Electric Vehicles (EVs). Given the expected uptake of IPT technology for both stationary and in motion in-road charging, many technical challenges regarding the electromagnetic field and thermal aspects need to be overcome to generate cost-effective and reliable solutions. One particular design constraint of in-road IPT systems is the occurrence of local increases in temperature during operation due to power losses in the wireless charging pads. In this paper, safe operating conditions of an enclosed wireless power transfer pad within a pavement model were identified. This aspect has been studied less rigorously compared with the electromagnetic design. This paper presents a numerical thermal analysis of a double-D (DD) prototype IPT primary pad based on two possible configurations; flush-mounted or buried, within a model pavement. A coupled electromagnetic-thermal simulation has been developed to aid in the development of thermally robust in-road IPT systems. In order to validate the proposed two-way coupled electromagnetic-thermal Finite Element (FE) simulations, experiments were performed to capture the evolving thermal field within an IPT primary pad under continuous and periodic duty cycles. This method made possible analysis of the heating patterns and so the identification of internal hotspots within an IPT pad in a roading structure. A thermal camera was used to provide detailed surface temperature distributions, while suitable application of non-metallic Fiber Bragg Grating (FBG) sensing technology enabled a robust technique to measure temperatures within the intense magnetic fields of a high frequency wireless power transfer system to be developed. Comparisons at steady state of the pavement surface temperature distribution, as well as point measurements with the pad and sand, demonstrate good accuracy. The maximum steady state surface temperature occurs at the centre of the sand surface where the IPT pad is placed and is approximately 87 °C and 100 °C for buried and flush-mounted pads, respectively. Moreover, for a 2/3 duty cycle loading, the maximum temperature of the pad tended to an average of approximately 76 °C, while at constant operation the average temperature is 105 °C. Therefore, a 5 min cooling period significantly reduced operating temperatures within the studied model IPT system. In the future, the methodologies proposed in this paper can also be used to improve the design of higher power IPT pads by identifying hotspots and maximum thermal stresses and determination of optimal charging patterns for heat dissipation.