Wireless Electric Vehicle Charging System Research Articles

Mitigation Conducted Emission Strategy Based on Transfer Function from a DC-Fed Wireless Charging System for Electric Vehicles

The large dv/dt and di/dt outputs of power devices in wireless charging system (WCS) in electric vehicles (EVs) always introduce conducted electromagnetic interference (EMI) emissions. This paper proposes a mitigation conducted emission strategy based on transfer function from a direct current fed (DC-fed) WCS for EVs. A complete test for the DC-fed WCS is set up to measure the conducted emission of DC power cables in a frequency range of 150 kHz–108 MHz. An equivalent circuit with high-frequency parasitic parameters for WCS for EV is built based on measurement results to obtain the characteristics of conducted emission from WCS. The transfer functions of differential mode (DM) interference and common mode (CM) interference were established. A judgment method of using transfer functions to determine the dominated interference mode responsible for EMI is proposed. From the comparison of simulation results between CM or DM and CM+DM interference, it can be seen that the CM interference is the dominated interference mode which causes the conducted EMI in WCS in EVs. A strategy of giving priority to the dominated interference mode is proposed for designing the CM interference filter. Finally, the conducted voltage experiment is performed to verify the mitigation conducted emission strategy. The conducted voltage of simulation and experiment is decreased respectively by 21.17 and 21.4 dBμV at resonance frequency 30 MHz. The conduced voltage at frequency range of 150 kHz–108 MHz can be mitigated to below the limit level-3 of CISPR25 standard (GB/T 18655-2010) by adding the CM interference filters.

An Integrated Characterization Model and Multiobjective Optimization for the Design of an EV Charger’s Circular Wireless Power Transfer Pads

A good magnetic design of a wireless electric vehicle (EV) charging system requires accurate characterization of the equivalent circuit parameters. This is while considering the effect of the magnetic core and the conductive shielding layers. In the literature, such an analysis is done using 3-D finite element analysis, which makes the design and optimization process time-consuming and computationally expensive. In this paper, an integrated analytical model for the characterization of a circular wireless power transfer EV pads is utilized. This analytical model provides a valuable tool to optimize the design process. This model is utilized when evaluating the objective function for each individual in the multiobjective Pareto Optimality optimization algorithm. The objective is optimizing the pads with three decision variables and four constraints.

A New Integration Method for an Electric Vehicle Wireless Charging System Using LCC Compensation Topology: Analysis and Design

There is a need for charging electric vehicles (EVs) wirelessly since it provides a more convenient, reliable, and safer charging option for EV customers. A wireless charging system using a double-sided LCC compensation topology is proven to be highly efficient; however, the large volume induced by the compensation coils is a drawback. In order to make the system more compact, this paper proposes a new method to integrate the compensated coil into the main coil structure. With the proposed method, not only is the system more compact, but also the extra coupling effects resulting from the integration are either eliminated or minimized to a negligible level. Three-dimensional finite-element analysis tool ANSYS MAXWELL is employed to optimize the integrated coils, and detailed design procedures on improving system efficiency are also given in this paper. The wireless charging system with the proposed integration method is able to transfer 3.0 kW with 95.5% efficiency (overall dc to dc) at an air gap of 150 mm.

Power Stabilization Strategy of Random Access Loads in Electric Vehicles Wireless Charging System at Traffic Lights

An opportunity wireless charging system for electric vehicles when they stop and wait at traffic lights is proposed in this paper. In order to solve the serious power fluctuation caused by random access loads, this study presents a power stabilization strategy based on counting the number of electric vehicles in a designated area, including counting method, power source voltage adjustment strategy and choice of counting points. Firstly, the circuit model of a wireless power system with multi-loads is built and the equation of each load is obtained. Secondly, after the counting method of electric vehicles is stated, the voltage adjustment strategy, based on the number of electric vehicles when the system is at a steady state, is set out. Then, the counting points are chosen according to power curves when the voltage adjustment strategy is adopted. Finally, an experimental prototype is implemented to verify the power stabilization strategy. The experimental results show that, with the application of this strategy, the charging power is stabilized with the fluctuation of no more than 5% when loads access randomly.

Design of a wireless charging system with a phase‐controlled inverter under varying parameters

Class-D full bridge is the most common inverter topology at the primary side for wireless electric vehicles (EVs) charging systems. This study takes a novel topology of a phase-controlled inverter as the power amplifier and puts it in a context of the whole charging system. The proposed inverter topology regulates the charging power through adjusting the phase-shift angle among phases with a constant operating frequency, which alleviates the EMI filter design. For various wireless EVs chargers, the gaps between the primary side and the secondary side are changing, which results in various coupling factors k . The equivalent resistance of the EVs battery R battery is also changing during the charging process. Even resonant frequencies at two sides are variable because of the components tolerances and operating environments. This study presents design considerations of a wireless EVs charging system with the proposed technology under variable k , R battery , and resonant frequencies. Circuit parameters are designed and the system efficiency is derived. Industrial prototype of an EV charging system is manufactured with the proposed topology at 3.0 kW. Experiments show that these design considerations can reflect the system characteristics, and the proposed system is a good candidate to be used in wireless EV battery chargers.

Study on High Efficient Electric Vehicle Wireless Charging System

Electric and unmanned is a new trend in the development of automobile, cable charging pile can not meet the demand of unmanned electric vehicle. Wireless charging system for electric vehicle has a high level of automation, which can be realized by unmanned operation, and the wireless charging technology has been paid more and more attention. This paper first analyses the differences in S-S (series-series) and S-P (series-parallel) type resonant wireless power supply system, combined with the load characteristics of electric vehicle, S-S type resonant structure was used in this system. This paper analyses the coupling coefficient of several common coil structure changes with the moving distance of Maxwell Ansys software, the performance of disc type coil structure is better. Then the simulation model is established by Simulink toolbox in Matlab, to analyse the power and efficiency characteristics of the whole system. Finally, the experiment platform is set up to verify the feasibility of the whole system and optimize the system. Based on the theoretical and simulation analysis, the higher charging efficiency is obtained by optimizing the magnetic coupling mechanism.

Magnetic Leakage Field Study of a 7 kW Wireless Electric Vehicle Charging System

This paper presents a study of the magnetic leakage field of a 7 kW wireless electric vehicle charging (WEVC) system. The leakage field was measured in different test configurations and environments. Typical system parameters, such as coil offset and air gap were evaluated in order to determine their influence on the leakage field distribution. All measured results were then validated by magnetic field simulations. Based on the results of this study, a magnetic leakage field assessment method based on simulation is proposed.

Coil Design and Measurements of Automotive Magnetic Resonant Wireless Charging System for High-Efficiency and Low Magnetic Field Leakage

For wireless charging of electric vehicle (EV) batteries, high-frequency magnetic fields are generated from magnetically coupled coils. The large air-gap between two coils may cause high leakage of magnetic fields and it may also lower the power transfer efficiency (PTE). For the first time, in this paper, we propose a new set of coil design formulas for high-efficiency and low harmonic currents and a new design procedure for low leakage of magnetic fields for high-power wireless power transfer (WPT) system. Based on the proposed design procedure, a pair of magnetically coupled coils with magnetic field shielding for a 1-kW-class golf-cart WPT system is optimized via finite-element simulation and the proposed design formulas. We built a 1-kW-class wireless EV charging system for practical measurements of the PTE, the magnetic field strength around the golf cart, and voltage/current spectrums. The fabricated system has achieved a PTE of 96% at the operating frequency of 20.15 kHz with a 156-mm air gap between the coils. At the same time, the highest magnetic field strength measured around the golf cart is 19.8 mG, which is far below the relevant electromagnetic field safety guidelines (ICNIRP 1998/2010). In addition, the third harmonic component of the measured magnetic field is 39 dB lower than the fundamental component. These practical measurement results prove the effectiveness of the proposed coil design formulas and procedure of a WPT system for high-efficiency and low magnetic field leakage.

A Novel Type of Wireless V2H System with a Bidirectional Single-Ended Inverter Drive Resonant IPT

Electric vehicles (EV) offer promise as an effective solution to environmental problems. One of the keys to their successful diffusion is the provision of adequate battery charging infrastructure. In order to create a charging infrastructure by installing equipment in such as locations as carports in private homes, the wireless battery charging system is very suitable. EVs can be used in smart house systems to supplement the energy storage. This vehicle to home (V2H) system essentially requires a bidirectional power transfer feature between the EV and home. This paper presents a new bidirectional inductive power transfer (IPT) system for wireless V2H with simplest components and low cost aiming at wide diffusion for home use. Proposed is a novel type of bidirectional wireless EV charging system with an efficient and compact type single-ended quasi-resonant high-frequency inverter for V2H.

A Comparative Study of Power Supply Architectures in Wireless EV Charging Systems

This paper examines two of the primary power supply architectures being predominantly used for wireless electric vehicle (EV) charging, namely the series LC (SLC) resonant and the hybrid series-parallel (LCL) resonant full-bridge inverter topologies. The study of both of these topologies is presented in the context of designing a 3-kW primary-side controlled stationary wireless EV charger with nominal operating parameters of 30-kHz center frequency, a range of coupling in the neighborhood of 0.18-0.26, and a parallel secondary pick-up with partial series coil compensation. A comparison of both architectures is made in terms of their design methodology, physical size, cost, complexity, and efficiency. It is found that the SLC architecture is 2.45% less costly than the LCL topology. On the other hand, it is observed that the LCL architecture achieves almost 10% higher peak efficiency at rated load and minimum coupling. The study also showed that the SLC topology suffers from poor light load efficiency, while the LCL topology maintains very high efficiency over its full range of coupling and loading. The study also revealed that the capacitor voltage stress is significantly higher in the SLC topology. Finally, it is also shown that the control complexity of the SLC architecture is higher than that of the LCL architecture because of its sensitivity to changes in the reflected secondary impedance, which result in loss of constant current source and ZVS operation unless a suitable combination of parameters are modulated by the closed-loop controller.

Analysis and Design of Bi-Directional PowerRegulator with wireless Power TransferTechnology for Electric Vehicles

Wireless charging has the power to greatly increase the convenience and accessibility of electric vehicles for charging. Wireless charging involves transferring power from the electric grid to a battery without the use of wires, cords or plugs. Electric vehicles not only draw power from the grid but also can supply surplus energy to grid or home when power consumption peaks or power outage. This is done with the help of bi-directional wireless power transfer technology. A wireless electric vehicle charging system based on inductively coupled power transfer (ICPT) technology is presented in this project. A simulation system is built in the Simulink, and the feasibility of the system is proved by simulation results.

STUDY OF RESONANCE-BASED WIRELESS ELECTRIC VEHICLE CHARGING SYSTEM IN CLOSE PROXIMITY TO METALLIC OBJECTS

A typical magnetic resonance coupling based wireless Electric Vehicle (EV) charging system consists of a transmitting coil at the charging station and a receiving coil in the vehicle. In order to maintain good energy transfer e-ciency of the wireless charging system, the efiect of the proximal metallic object in the vicinity of the receiving coil has been investigated. Both from the simulation and experimental measurement, it has been observed that the resonance based wireless energy transfer system is very sensitive to the nearby metallic objects, leading to signiflcant deterioration in energy transfer e-ciency. This efiect on the energy transfer e-ciency is also seen to be difierent for difierent physical spacing between the transmitting and receiving coils. It is also found that the operating resonant frequency for optimum energy transfer e-ciency changes with the metallic object in close proximity to the receiving coil. The simulated results well agree with the experimental results. The analysis will provide future guidelines for designing an e-cient resonance coupling based wireless charging system for EVs even in the presence of metallic objects.