Wireless Charging Of Electric Vehicles Research Articles

Single-Transmitter Multiple-Pickup Wireless Power Transfer: Advantages, Challenges, and Corresponding Technical Solutions

As an emerging research topic, wireless power transfer (WPT) with a single transmitter for multiple pickups (STMP) shows salient advantages of reducing the number of power inverters, increasing the power density, and so on, which has profound implications for various applications, such as wireless charging for electric vehicles (EVs) and smart homes. First, this article introduces the concept of STMP-WPT and three critical issues, namely, misaligned transmission, resonance shifting, and energy security. Then, the corresponding solutions are elaborated from the perspectives of the magnetic and electric fields, respectively. Finally, the technical challenges for STMP-WPT systems are discussed.

Crossed flat solenoid coupler for stationary electric vehicle wireless charging featuring high misalignment tolerance

This study proposes a crossed flat solenoid coupler (CFSC) for electric vehicle wireless charging. The impact of four size parameters of CFSCs on coupling coefficient and misalignment tolerance is studied using finite-element analysis. The optimisation methodology of CFSCs considering size constraints is given. The CFSC is compared with the planar square coupler (PSC) and double D coupler (DDC) from three aspects: coupling coefficient, misalignment tolerance, and copper usage. The CFSC performs the best in the three aspects, and the DDC performs the worst. Two wireless power transfer prototypes, one employing CFSCs and the other utilising PSCs, were built to demonstrate the superiority of the proposed coupler. Primary inductor-capacitor-capacitor secondary series compensation topologies were employed in the two prototypes. Experiments agree well with theoretical analysis and simulations. The power transfer efficiency of the CFSC-based prototype was 1.6% higher than the PSC-based prototype when the Z-axis displacement is 45 mm.

Multiobjective Optimization of Inductive Power Transfer Double-D Pads for Electric Vehicles

This article proposes a multiobjective optimization method of a primary double-D pad for inductive power transfer systems. First, a parametric sweep analysis is conducted to choose the crucial design parameters. Then, using the nondominated sorting genetic algorithm II, the structure of the double-D pad can be optimized based on two key objectives; ensuring a good coupling coefficient while minimizing the worst-case stray leakage magnetic fields. Several useful design guidelines are found from the optimization results, including how the dimensions of both the coil and layers affect the coupling coefficient and stray leakage magnetic fields around the pad. A practical coil suitable for wireless charging of electric vehicles at level 2, similar to that recommended in SAE J2954, is used as the reference and also as the starting point for the optimization. Two of the coil structures resulting from the optimization are chosen and investigated further to assess their performance with different secondary pad misalignments using finite element methods. Finally, an experimental setup is built to validate the optimal pad structures.

Protection Strategy for Wireless Charging Electrical Vehicles

Wireless charging has become increasingly popular for electric vehicles (EVs) in recent years. However, possible device damage may happen because of the sharp variations of inverter output current and the ZVS angle due to the alignment variation between resonant coils especially while charging. To design a protection strategy, the characters of the inverter output current and phase angle are analyzed when the wireless charging EV leaves. The protection strategy is composed of the insufficient angle protection, overcurrent protection, and the excessive angle protection. A detection circuit is designed to measure the variation of inverter output current and phase angle. A wireless charging EV prototype is established to validate the proposed methods. The experimental results show that the designed detection circuit and protection strategy can catch the abnormal working state of the system when the wireless charged EV leaves and take measures immediately to protect the main circuit of the system from device damages.

Push–Pull Class $\Phi _{\text{2}}$ RF Power Amplifier

The Class $\Phi _\text{2}$ /EF $_{\text{2}}$ amplifier is an attractive topology for high-voltage and high-frequency power conversion because of the high efficiency, reduced device voltage stress, simplicity of gate driving, and load-independent ZVS operation. Due to many degrees of freedom for tuning, previous studies can only solve the single-ended $\Phi _\text{2}$ circuit using numerical methods. This work focuses on improving the design and operating characteristics of a push–pull $\Phi _\text{2}$ amplifier with a $T$ network connected between the switch nodes, or a PPT $\Phi _\text{2}$ amplifier. The PPT $\Phi _\text{2}$ amplifier has less circulating energy and achieves higher cutoff frequency $f_{T}$ than other $\Phi _\text{2}$ /EF $_{2}$ circuits. We, then, present a series-stacked input configuration to reduce the switch voltage stress and improve the efficiency and power density. A compact 6.78-MHz, 100-V, 300-W prototype converter is demonstrated that uses low-cost Si devices and achieves 96% peak total efficiency and maintains above 94.5% drain efficiency across a wide range of voltage and power. Together with the advances in wide-bandgap semiconductors and magnetic materials, the PPT $\Phi _\text{2}$ circuit opens more possibilities for the state-of-the-art performance of solid-state RF amplifiers in high-frequency, high-power applications, including wireless charging for electric vehicles, plasma RF drives, and nuclear magnetic resonance spectroscopy.

Design and Optimization of an Electric Vehicle Wireless Charging System Using Interleaved Boost Converter and Flat Solenoid Coupler

Simple but effective output voltage/current control schemes are essential for electric vehicle wireless charging systems (EVWCSs). This article proposes an EVWCS using interleaved boost converter (IBC) and flat solenoid coupler (FSC). The closed-loop control between the primary and secondary is realized by adjusting the duty cycle of the IBC. The currents and losses in the primary are reduced in the proposed system because the dc bus voltage in the primary is increased by using the IBC. The input current ripple is diminished owing to the interleaved structure. This article also proposes a parameter optimization method to obtain the optimal FSC. Without loss of generality, the total area of the transmitter (Tx) and receiver (Rx) is assumed to be constant, and the Tx is assumed to be larger than the Rx. A scale-down prototype whose output power is 500 W was built in the laboratory to verify the theoretical analysis. The output voltage of the prototype kept constant when the misalignment was 200 mm in the winding direction or 100 mm in the magnetic direction. A highest system efficiency, from dc input to dc output, of 90.1% was achieved when the power transfer distance was 170 mm.

A Design Method to Implement ZVS for Electric Vehicle Wireless Charging System With Double-Side LCC Compensation

In this article, the zero voltage switching (ZVS) of the inverter in the electric vehicle wireless charging system is realized through the parameter optimization design of compensation components, which is conducive to the high efficient operation of the system. The effects of the parameter adjustment of each compensation component on the input impedance angle and output current of the double-side LCC compensation topology were analyzed under the conditions of different output voltages and coupling coefficients, which provides a basis for the component optimization design of the inverter ZVS realization. The quantitative relationship between the optimized component parameter and the soft switching implementation conditions was analyzed. Then, a specific parameter design method was proposed, according to the results analyzed earlier. At last, the effectiveness of the proposed method was verified by a 3.3-kW wireless charging system prototype. Experimental results show that the optimized system is always able to achieve soft switching, the system efficiency is up to 95.2% at the rated power, and it is higher than 93% even under the condition where the coupling coefficient and output voltage are both reduced by half.

Position detection and route correction of electric vehicles by dynamic wireless charging

During the dynamic wireless charging of electric vehicles, the offset from the vehicle Rx coil will reduce the mutual inductance of the coupling mechanism, which results in a significant reduction on the transmission efficiency of the system. Now a real-time detection method of electric vehicle position based on double coils is proposed. By analyzing the change trend of the pickup voltage in the detection coil, the correspondence among the lateral deviation distance, the offset angle and the pickup voltage is obtained by difference ratio sum method, the position information of electric vehicle will be worked out. Then the PID with variable structure was deployed algorithm to realize the self-correction of the electric vehicle driving route. The construction of experimental platform verifies the feasibility of the positioning method. The results revealed that when a lateral deviation takes place, this method can guarantee the automatic correction to the path of an electric vehicle during the dynamic wireless charging process. The advantages of this method are high sensitivity, fast correction speed, a simple structure, etc.

Mesh-Based Accurate Positioning Strategy of EV Wireless Charging Coil With Detection Coils

Wireless charging technology greatly improves the flexibility and convenience of electric vehicles (EVs) charging. The alignment of coils directly affects the performance of the wireless charging system. The shift of the secondary coil leads to the decrease in transmission power and efficiency. Aiming to solve the abovementioned problems, in this article a mesh-based accurate positioning strategy for the EV wireless charging coils has been proposed. The strategy takes the center of the primary coil as the origin and divides the meshed reference points in the plane of the secondary coil. It is based on the voltage principle induced by the detection coils installed on the secondary coil. The coordinate calculation formula is derived by fitting the curve of the induction voltage with distance. The centimeter-level positioning of the secondary coil is realized in the X and Y directions of the horizontal plane. The proposed strategy is verified by simulations and experiments. The effectiveness and stability of the proposed method are verified by many simulations and experiments. Without considering the rotation of the coil, the maximum error is within 3 cm in a 5 cm mesh width. The positioning strategy helps to align the coils and improves the electrical transmission performance. It is also helpful for automatic parking, unmanned vehicle, and other industrial applications.

Application and Development Prospect of Wireless Charging For Electric Vehicles

Wireless charging technology for electric vehicles (WCT) is a new non-contact charging technology applied to new energy electric vehicles. Compared with traditional contact wire charging, WCT has the advantages of high safety factor, less weather factor, more intelligent charging and convenient configuration. Firstly, this paper discusses the background of wireless charging technology for electric vehicles, the development history of wireless charging and the research status at home and abroad. Then, it summarizes the basic composition, principle, category and performance characteristics of electric vehicle wireless charging, describes the main application status and development prospects of wireless charging technology in electric vehicle, and finally analyses the 3-60 kW high-power wireless charging case of ZTEV electric vehicle which has been applied in many places in China and Qualcomm case, put forward the future prospects of wireless charging technology for automobiles.

전기차 무선 충전을 위한 주차위치 탐색에 관한 연구

전기차 무선 충전을 위한 주차위치 탐색에 관한 연구

A Single-Stage Bidirectional Inductive Power Transfer System With Closed-Loop Current Control Strategy

A conventional two-stage topology that consists of a dc/ac converter, a dc-link, and two ac/dc converter is being used as wireless charging of electric vehicles (EVs). However, the conventional topology contains more conversion stages with a bulky dc-link capacitor, and implementation of control strategies is not easy to transfer power from the primary coil to pickup coil or vice versa. A single-stage, inductive power transfer (IPT) system with a simple control strategy is needed to reduce the conversion stages and to increase the reliability of the system. This article proposes a control strategy for a single-stage conversion topology that is easy to implement and more importantly can achieve unity power factor (UPF) using a single controller. The experimental validation of single-stage conversion topology and steady-state analysis with series–series (SS) compensation scheme is presented in this article. A fixed angle of ±90° in between the output phase of the converters is achieved without estimating any power or current parameters. A hardware prototype working at a lower watt rating is analyzed, and the validation of the proposed system for 3.7-kVA rating as per the international standard is simulated. Furthermore, transient response is also observed to verify the closed-loop control scheme of battery current.

A Novel Converter Topology for a Primary-Side Controlled Wireless EV Charger With a Wide Operation Range

The full-bridge commonly employed in the primary of an SAE J2954 compliant inductive power transfer (IPT) based wireless electric vehicle (EV) charger possesses many challenges. To alleviate these issues, expensive switches, and extra components are employed together with secondary-side regulation. As an alternative, this article proposes a new topology, termed integrated boost multilevel converter (IBMC). An IBMC consists of series-connected half-bridge submodules (SMs) in each arm, and the dc supply is connected to each arm through a dc inductor. When an IBMC is used as the primary converter, its ability to generate a boosted multilevel output voltage, enables it to regulate the power flow efficiently over a wide load/coupling range without requiring a secondary-side regulator. This article focuses on the operating principles of this new IBMC under steady-state conditions and discusses a modulation scheme that can be used to regulate the power flow while balancing the SM voltages. The benefits of the IBMC is experimentally validated using an SAE J2954 WPT2/Z2 compliant prototype. This prototype used an IBMC built with low-cost switching devices on the primary-side to regulate the power flow to 7.7 kW as the coupling factor changed between 0.11 and 0.25 while maintaining the system efficiency between 90.4% and 91.9%.

Power loss analysis and thermal assessment on wireless electric vehicle charging technology: The over-temperature risk of ground assembly needs attention

To support e-mobility, wireless electric vehicle charging (WEVC) emerges as a promising technology by virtue of convenience characteristics and the mitigation of range anxiety. Recently, the safety issues on WEVC systems have drawn considerable attention. In light of thermal safety, the most critical part of WEVC systems is the surface of ground assembly (GA). During the charging process, its temperature increases due to the power losses, possibly resulting in cutaneous injury to living bodies and the ignition of foreign objects. Especially when there are evitable misalignments between the GA and vehicle assembly, its temperature rise will be higher as a penalty of efficiency deterioration of WEVC systems. Unfortunately, it has rarely been deemed as a safety hazard yet. Taking a commercialized WEVC system rated at 6.6 kW as an example, this paper focuses on the safety assessment of GA surface. The overtemperature-related losses, including core loss, ohm loss and eddy-current loss, are calculated. The thermal analysis is conducted based on the heat transfer theory. The temperature distribution of GA surface is obtained using transient-state FEM simulations. Based on IEC standards, four hazard levels are proposed as evaluation criteria. Finally, the calculated accuracy is validated experimentally. The results reveal direct influence of misalignments on the temperature rise. The sensitivity of different misalignments to the temperature rise is also analyzed. When the horizontal displacement exceeds 98.86 mm or the angular offset (type II) exceeds 9.91 deg., the highest hazard level could be reached, which highlights severe over-temperature risks of GA surface.

A Metal Object Detection System with Multilayer Detection Coil Layouts for Electric Vehicle Wireless Charging

Non-radiative inductive power transfer is one of the most studied and commercially applied wireless charging technologies, where the magnetic field is employed as the medium for power transfer. In the wireless charging of electric vehicles, the strong magnetic field will heat up any metal items falling in the charging area due to eddy current induced in the metal objects, causing hazards like fire. Metal object detection (MOD) is necessary for the market penetration of inductive power transfer technology. This paper aims to improve the performance of systems that detect metal objects based on inductance variations. Two novel multi-layer detection coil layouts are proposed, which can not only cover the entire charging area without blind spots but can also be decoupled from the transmitter and receiver to minimize the influence of the magnetic field that is used for power transfer. Two mixed resonant circuits are proposed and proven to have better performance than parallel and series resonance. The impacts of the detection coil layer, trace width, and turn-number are investigated. The test results indicate that the MOD system can detect one-cent coins at various positions of the detection coil printed circuit board, and can also detect various inductance variations without blind spots in the processing circuit.

RETRACTED: Modeling and analysis of dynamic wireless charging for electric vehicles under different working scenarios

Dynamic wireless charging technology can solve the charging problem of electric vehicle. There is little research on the influence of dynamic wireless charging on electric vehicle. This paper establishes the energy model of the vehicle system by using Advisor and MATLAB. An energy control strategy for dynamic wireless charging of electric vehicles is designed. The influence of dynamic wireless power transfer on energy storage system loss and electric vehicle range under different operating scenarios and different minimum battery charge states is studied. The variation of state of charge, energy usage and the overall system efficiency are compared and analyzed. This paper analyzes the influence of SOC by vehicle parameters and external parameters in dynamic wireless charging, and the influence on electric vehicle driving range further.

Loss characteristics of superconducting pancake, solenoid and spiral coils for wireless power transfer

Wireless power transfer (WPT) is an emerging technology with widespread applications, such as wireless charging for electric vehicles (EVs), which has become a major point of interest. Conventionally, it is used for stationary charging, but also dynamic systems emerge. Key drawbacks of standard WPT systems are the limited transfer distance between the copper coils and the transfer efficiency. By employing high-temperature superconductors (HTS) as coil material these limitations can be alleviated. However, HTS coils have highly nonlinear ac loss characteristics, which will be studied. This paper investigates the transport current loss and the magnetisation loss of HTS coils individually and when combined in the high frequency range relevant to WPT for EVs. A multilayer 2D axisymmetric coil model based on H-formulation is proposed and validated by experimental results as the HTS film layer is inapplicable at such frequencies. Three of the most commonly employed coil configurations, namely: double pancake, solenoid and circular spiral are examined. While spiral coils experience the highest transport current loss, solenoid coils are subject to the highest magnetisation loss due to the overall distribution of the turns. Furthermore, a transition frequency is defined for each coil when losses in the copper layer exceed the HTS losses. It is much lower for coils due to the interactions between the different turns compared to single HTS tapes. At higher frequencies, the range of magnetic field densities, causing a shift where the highest losses occur, decreases until losses in the copper stabilisers always dominate. In addition, case studies investigating the suitability of HTS-WPT are proposed.

Loss analysis of superconducting wireless charging for electric vehicles

Wireless power transfer (WPT) is an emerging technology with widespread applications. It can be used for charging in multiple applications, such as wireless charging for electric vehicles (EVs), which has become a major point of interest. Conventionally, it is used for stationary charging, but also dynamic systems emerge. Key drawbacks of standard WPT systems are the limited transfer distance between the copper coils and the transfer efficiency. By employing high-temperature superconductors (HTS) as coil material these limitations can be alleviated. However, HTS coils have an interesting ac loss characteristic which will be studied. This study investigates the transport current and magnetisation loss of HTS coils in the frequency relevant to WPT for EVs. In addition, a comparison between the full anisotropic dependency of the critical current and only considering perpendicular field components is conducted. A homogenous 2D axisymmetric coil model is used to examine three of the most employed coil configurations and their loss characteristics depending on turn numbers.

Research on Optimal Design and Practical Application of Electric Vehicle Wireless Charging Technology

Electric vehicles are a further development of wireless charging technology and a promising application area. This method can take into account the user’s charging satisfaction and the load pressure of the charging road, while meeting the requirements of power supply cost and power supply stability. This article introduces the research progress and application of wireless charging technology at home and abroad, then introduces the classification of wireless power transmission technology in detail, and then introduces the structure of the wireless power transmission system of electric vehicles in detail. Simulation results of the wireless charging technology of the car show that the advancement of charging technology will lead to the further development of new energy electric vehicles in the future. This article describes the development of new energy electric vehicle charging technology in recent years, and puts forward the development direction and development suggestions of new energy electric vehicle charging technology.

Foreign Object Detection for Electric Vehicle Wireless Charging

Wireless power transfer technology is being widely used in electric vehicle wireless-charging applications, and foreign object detection (FOD) is an important module that is needed to satisfy the transmission and safety requirements. FOD mostly includes two key parts: metal object detection (MOD) and living object detection (LOD), which should be implemented during the charging process. In this paper, equivalent circuit models of a metal object and a living object are proposed, and the FOD methods are reviewed and analyzed within a unified framework based on the proposed FOD models. A comparison of these detection methods and future challenges is also discussed. Based on these analyses, detection methods that employ an additional circuit for detection are recommended for FOD in electric vehicle wireless-charging applications.