Primary-Side Power Flow Control of Wireless Power Transfer for Electric Vehicle Charging

Wireless Power Transfer (WPT) technology can transfer electrical energy from a transmitter to a receiver wirelessly. Due to its many advantages, WPT technology is a more adequate and suitable solution for many industrial applications compared to the power transfer by wires. Using WPT technology will reduce the annoyance of wires, improve the power transfer mechanisms. Recently, the WPT gain enormous attention to charging the on-board batteries of the Electric Vehicle (EV). Several well-known car manufacturing companies start efforts to adopt WPT technology and enhance its features. Therefore, WPT can be achieved through the affordable inductive coupling between two coils named a transmitter and a receiver coil. In EV charging applications, transmitter coils are located underneath the road, and receiver coils are installed in the EV. The inductive WPT of resonant type is generally applied to medium-high power transfer applications like EV charging because it achieves better energy efficiency. In this chapter, various WPT technologies are discussed and tested in EV wireless charging applications. Furthermore, extensive information is given to developing an advanced WPT technology that can transfer maximum power by achieving maximum efficiency.

Wireless power transfer (WPT) offers a viable solution for facilitating efficient and sustainable communication networks serving energy-limited communication devices. WPT technology enables simultaneous wireless information and power transfer (WIPT). The existing WPT technologies can be categorized into three classes: inductive coupling, magnetic resonant coupling, and RF-based WPT. RF-based energy harvesting technology enables the possibility of simultaneous WIPT (SWIPT), wireless-powered communication (WPC), and wireless-powered backscatter communication (WPBC).This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book addresses the challenges incurred by the nature of WPT and provides a comprehensive reference for various solutions for realizing efficient WIPT in practice. It also provides some background information on WPT and discusses exciting research directions. The book helps to study the fundamental problems in WIPT networks, including communication security in WIPT systems, energy transfer efficiency, and interference management in WIPT systems.

This paper reports our laboratory's latest wireless-driven LED lighting system, which adopted wireless electrical energy transmission technology. Wireless power transfer technology is the transmission of electrical energy from a power source to an electrical load without man-made conductors. Traditional LED lighting system sensitive to rigid environment such as humidity, corrosive and flammable. Combining the advantages of wireless electrical power transfer and LED semiconductor lighting technology, the wireless-driven LED (WD-LED) lighting system has advantages of electrical shock protection, convenient, reliable, portable and environmentally sound. The wireless-driven LED lighting source will gain increasing attention in the civilian consumer electronics market, military area and special lighting areas. To achieve wireless electric power transfer in LED lighting system, the wireless-driven LED lighting system should contain LED lighting module, wireless electrical power transfer system, LED driving circuit and electrical energy storage system. The LED lighting module was driven by the electrical power, which was transferred from a contact free system. Either inductive coupling or magnetic resonance coupling is responsible for transferred the electrical power. Wireless-driven LED lighting system has a good market prospects, this new technology will make these innovative LED lighting products more available, convenient and reliable. In this paper, we mainly research in wireless electrical energy transmission tech, LED integrated package tech, LED driver circuit tech. Finally, we introduce several wireless-driven LED lighting products in different application areas.

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

In the past years, extensive research has been carried out on wireless power transfer (WPT), since it offers customers a convenient charging technique compared to wires which can be inconvenient and allows charging of portable devices in a wide power range. WPT technology has been observed to have some remarkable technological advantages due to its spatial freedom. Owing to modern power electronics technology and high-power semiconductors, WPT technology is highly integrated, and many smart WPT devices have been developed for different applications such as biomedical devices, electric vehicles (EV), and portable consumer electronic devices. A burst in the WPT market for consumer electronics is expected in the coming five years, due to the ubiquitous usage of 3G/4G wireless networks and continually evolving technologies for media and entertainment. WPT systems for consumer devices can be classified into two main types: inductive power transfer (IPT) and magnetic resonant coupling (MRC). The former works at 100-200 kHz, whereas the latter works at 6.78 or 13.56 MHz. The bottleneck of the IPT technology is to design a low cost but high performance WPT system since the IPT mainly targets on the application with less requirement of distance freedom like home appliance or some industrial applications with short charging distance. The main targets of MRC technology is to provide consumers a flexible WPT solution with higher distance freedom. The main concern of this technology is that 1) it is challenging to design high efficiency circuits for MHz application, especially for rectifier; 2) the control of the MRC is challenging since the output power would be effected remarkably by distance, which is known as splitting frequency phenomenon. This research develops circuits and control algorithms for both types of WPT systems. Firstly, a single-stage AC-DC voltage regulator is developed. A noncharging configuration is introduced to regulate the output voltage at a desired level with a pulse width modulation (PWM) control algorithm. In this way, there is no need for the DC-DC stage after the rectifier and additional wireless communication circuit blocks. In addition, a full-active cross-coupled structure is utilized to reduce the power loss of the regulator. Experimental results of the proposed regulator based on a 0.35 µm technology and PCB circuit demonstrate a maximum output power of 15 W and peak efficiency of 92 %. Another contribution of this dissertation is a design of a full active rectifier working at 6.78 MHz. An adaptive time delay (ATD) circuit is used to maximize the conduction interval of the gallium nitride (GaN) switch in order to minimize the power loss due to the forward voltage drop of the diode. The proposed control algorithm also eliminates the reverse leakage current of the rectifier. Except the power devices, all the other circuits have been taped out with a 0.18 µ m CMOS process. The experimental results of the proposed rectifier shows that it can output a maximum output current of 3 A at 5 V with a 6.78-MHz AC input voltage with a peak power efficiency over 90%. The last contribution is a novel control method for a 6.78-MHz MRC system. In this part, detailed analysis of MRC, especially on the relationship between operating frequency, transfer efficiency, output power, and coupling coefficient are presented. Contrary to the traditional research, this research proves that the MRC system is able to work with sufficient output power and efficiency within a wide coupling coefficient range, relaxing the system from the bound of the key coupling coefficient limitation. A hybrid control method with frequency/phaseshift tuning with zero voltage switching (ZVS) Class-D amplifier is proposed to provide the load with a constant output voltage. The testing results shows that it is able to transfer 10 W over a 5 cm with an overall efficiency (end to end) of 71.8 %, and over a 1 cm with an overall efficiency of 73.1%.

Wireless charging for moving electric vehicles could extend their cruising distance. Wireless power transfer via magnetic resonant coupling is suitable for this application. The transmitting efficiency can be maximized by using a DC-DC converter on the secondary side. The control system, however, must be designed properly to satisfy the response requirements depending on motion of the vehicle. Previous controllers were designed without considering the dynamics of the DC-DC converter for wireless power transfer via magnetic resonant coupling. This paper proposes the design method of secondary voltage control with a feedback controller using a novel DC-DC converter model based on the analysis of wireless power transfer system. Experiments show that the proposed model is effective and that the secondary voltage control improves not only the transmitting efficiency but also the charging power at any transmitting distance.

Since 2007, resonant coupling wireless power transfer (WPT) technology has been attracting attention and has been widely researched for practical use. Moreover, dosimetric evaluation has also been discussed to evaluate the potential health risks of the electromagnetic field from this WPT technology based on the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. However, there has not been much experimental evaluation of the potential health risks of this WPT technology. In this study, to evaluate whether magnetic resonant coupling WPT induces cellular stress, we focused on heat shock proteins (Hsps) and determined the expression level of Hsps 27, 70 and 90 in WI38VA13 subcloned 2RA human fibroblast cells using a western blotting method. The expression level of Hsps under conditions of magnetic resonant coupling WPT for 24 h was not significantly different compared with control cells, although the expression level of Hsps for cells exposed to heat stress conditions was significantly increased. These results suggested that exposure to magnetic resonant coupling WPT did not cause detectable cell stress.

Wireless power transfer (WPT) technology has revolutionized the charging processes of electric vehicle (EV), presenting a viable alternative to traditional wired charging methods. This paper provides a fundamental exploration of WPT, emphasizing its application in EV charging. The paper examines various WPT technologies, design considerations, and the associated international standards. A critical analysis of the current WPT technological challenges, such as misalignment, is discussed, highlighting effective strategies like multi-coil configurations and dynamic control systems that adapt to variations in alignment, enhancing efficiency and robustness. These methods significantly mitigate the common misalignment issues in deploying WPT systems, ensuring higher operational effectiveness and reliability. This analysis shows that WPT systems achieve power Transfer efficiencies of over 90% at distances up to $$\:20\:\text{c}\text{m}$$ , with misalignment tolerances improving by $$\:30\text{\%}$$ through these advanced designs. The deployment of these systems in urban settings shows a potential reduction in charging infrastructure costs by up to $$\:25\text{\%}$$ , underscoring the economic viability of WPT. Future directions explored include enhancing system compatibility across different EV models and expanding the applicability of WPT in heavy-duty vehicles. This review aims to provide insights for engineers, researchers, and policymakers aiming to optimize WPT technologies for sustainable transportation electrification.

This study evaluates five prominent Wireless Power Transfer (WPT) technologies Inductive Coupling, Resonant Inductive Coupling, Radio Frequency (RF) Transfer, Magnetic Resonance Coupling, and Laser Power Transfer based on multiple performance criteria using the Grey Relational Analysis (GRA) method. The technologies were assessed on four key parameters: efficiency, range, safety, and cost-effectiveness. Through normalization, deviation sequence, and the calculation of Grey Relational Coefficients (GRC), we established a Grey Relational Grade (GRG) for each technology, ranking them based on their overall performance. The results show that Laser Power Transfer ranks highest among the WPT methods, achieving the best balance of range, safety, and cost-effectiveness, with a GRG of 0.8571. This technology is optimal for applications requiring long-range power transfer, although it has moderate efficiency. Inductive Coupling, with the second-highest GRG (0.5238), excels in efficiency but is limited by its short range, making it ideal for close-contact applications, such as charging pads. RF Transfer ranks third, offering a moderate balance of range and cost-effectiveness, suited for remote, low-power applications where efficiency is less critical. Magnetic Resonance and Resonant Inductive Coupling rank fourth and fifth, respectively, showing moderate performance across all criteria without excelling in any specific aspect. The use of GRA enables a structured and quantitative assessment of each technology’s suitability for various applications, highlighting their strengths and limitations relative to an ideal performance profile. This research provides valuable insights for selecting WPT technologies based on specific operational requirements, supporting decision-making in fields such as consumer electronics, medical devices, and industrial automation. Future work may involve exploring other criteria, such as environmental impact and scalability, to further refine the selection process.

Wireless power transfer (WPT) technology has been widely used in industrial and household fields. This technology is of great significance in the field of motor drives. However, if the WPT technology is applied to the motor drive and control system, power and control signals need to be transmitted at the same time, which will cause the problem of mutual interference between signals of different frequencies, and will also increase the difficulty of frequency decomposition on the secondary side. To solve the above problems, a dual-frequency simultaneous wireless information and power transfer (SWIPT) system using a tapped coil structure scheme is proposed and the design principle of the tapped coil is given. Based on this scheme, a multi-frequency pulse width modulation (MFPWM) method is used to generate two components of different frequencies by the same inverter, which are automatically decoupled by the tapped coil, and finally transmitted to drive and control the motor. A closed-loop control strategy is used to solve the problem of precise motor speed control when the driving voltage of the wireless motor fluctuates. In the experiment, the motor speed increased from 1965 rpm to 2265 rpm, and the DC voltage corresponding to the set reference speed increased from 1.26 V to 2.30 V. The experimental results show that the scheme can control the BLDC motor speed stably and accurately.

Wireless power transfer (WPT) is a paradigm shift in electric-vehicle (EV) charging that offers the consumer an autonomous, safe, and convenient option to conductive charging and its attendant need for cables. With WPT, charging process can be fully automated due to the vehicle and grid side radio communication systems, and is non-contacting; therefore issues with leakage currents, ground faults, and touch potentials do not exist. It also eliminates the need for touching the heavy, bulky, dirty cables and plugs. It eliminates the fear of forgetting to plug-in and running out of charge the following day and eliminates the tripping hazards in public parking lots and in highly populated areas such as shopping malls, recreational areas, parking buildings, etc. Furthermore, the high-frequency magnetic fields employed in power transfer across a large air gap are focused and shielded, so that fringe fields (i.e., magnetic leakage/stray fields) attenuate rapidly over a transition region to levels well below limits set by international standards for the public zone (which starts at the perimeter of the vehicle and includes the passenger cabin). Oak Ridge National Laboratory s approach to WPT charging places strong emphasis on radio communications in the power regulation feedback channel augmented with software control algorithms. The over-arching goal for WPT is minimization of vehicle on-board complexity by keeping the secondary side content confined to coil tuning, rectification, filtering, and interfacing to the regenerative energy-storage system (RESS). This report summarizes the CRADA work between the Oak Ridge National Laboratory and the Toyota Research Institute of North America, Toyota Motor Engineering and Manufacturing North America (TEMA) on the wireless charging of electric vehicles which was funded by Department of Energy under DE-FOA-000667. In this project, ORNL is the lead agency and Toyota TEMA is one of the major partners. Over the course of the project, ORNL and Toyota TEMA worked closely on the vehicle integration plans, compatibility, and the interoperability of the wireless charging technology developed by ORNL for the vehicles manufactured by Toyota. These vehicles include a Toyota Prius Plug-in Hybrid electric vehicle, a Scion iQ electric vehicle, and two Toyota RAV4 electric vehicles. The research include not only the hardware integration but also the controls and communication systems development to control and automate the charging process for these vehicles by utilizing a feedback channel from vehicle to the stationary unit for power regulation.

Wireless powering by magnetic resonant coupling: Recent trends in wireless power transfer system and its applications

The closed-loop control of wireless power transfer (WPT) systems requires a communication link between the power transmitter and the power receiver for dual-side cooperation. Near-field communication techniques that utilize the power link are preferred for this purpose due to high reliability and security. In this letter, we propose a frequency-modulated phase shift keying (FMPSK) communication technique for the closed-loop maximum efficiency point tracking (MEPT) control of WPT. The technique uses very shallow phase modulation depth to minimize the disturbance on power flow and reduce the efficiency drop caused by the PSK. Meanwhile, it ensures the signal accuracy and precision by multiple methods and precise frequency modulation and demodulation. In experiment, we obtained 82%-85% system efficiency with a 25-125 W load over a distance equal to the coil diameter, and 93% efficiency over a distance equal to the coil radius. The efficiency drop caused by FMPSK was less than 1%. The dynamic processes of voltage regulation and MEPT took only about 1 ms and 10 ms, respectively.

Although wireless power transfer (WPT) technology has many advantages, this wireless feature also brings issues. To regulate the output or to achieve synchronous rectification, the rectifier on the secondary side needs to be controlled. Also, for bidirectional power control, the phase difference between the ac voltages on the primary and secondary sides should also be regulated. The control of the rectifier on the secondary side requires phase synchronization with the primary side. Current solutions use the secondary current for frequency locking and phase synchronization. However, this method is dependent on the secondary current waveform, which can be discontinuous or distorted. Such waveforms can lead to issues. This paper proposes a dual-side phase-shift control using driving windings to transfer driving pulses without a secondary-side controller. The driving windings are decoupled from the power windings. By controlling the phase difference between the power and driving windings on the primary side, the phase difference between the power windings on both sides can be regulated, independent from power transfer. Circuit simulations in LTspice validate the effectiveness of the proposed method.

This paper considers the potential of replacing step-down power transformers of the entire power grid as well as part of their transmission line branches with wireless power transfer (WPT) technology components. Exploiting the state-of-the-art evolutions in the fields of WPT technology, coupled resonators in domino arrangements—domino coupled resonator (DCR) configurations—are proposed as suitable technological substitute for step-down power transformers and are investigated in terms of performance metrics such as power transfer efficiency (PTE) and transformation ratio (TR). The contribution of this paper is fivefold. First, an analytical theoretical analysis appropriate to the study of practical DCR configurations is demonstrated. In order to support the DCR configuration replacement venture, a detailed set of assumptions regarding efficient mid- and long-range high-power WPTs as well as related technical issues is first presented. The validity of the theoretical analysis is verified through experimental measurements. Second, applying the proposed theoretical analysis, a wealth of system parameters that mainly influences the PTE and TR of DCR configurations is identified. Their quantitative effect as well as corresponding DCR configuration adjustments are first presented. Third, an approximate method, denoted as approximate chain scattering matrix (CSM) method, is first introduced. Based on the scattering matrix theory formalism, the approximate CSM method is suitable for mid- and long-range DCR configurations when the theoretical analysis becomes computationally slow. The numerical results of approximate CSM method are compared with the respective ones of theoretical analysis validating the extent and the accuracy of approximate CSM method. Fourth, the potential of power transformer replacement with practical DCR configurations is thoroughly investigated in terms of their TRs. A plethora of high-voltage/medium-voltage (HV/MV), MV/low-voltage (MV/LV), and HV/LV power transformers used across the world is investigated verifying their replacement potential with practical DCR configurations in all the cases examined. Fifth, based on a detailed collection of dimensions concerning power transformers and transmission line branches, it is first verified that practical DCR configurations cannot only substitute all step-down power transformers of the today's power grid but also replace entire transmission line branches too. Finally, it is obvious that there is a long journey ahead for WPT technology and its ultramodern DCR configurations to be affordably, widely, reliably, sustainably, and safely adopted in the human society. During these first steps of WPT development for power transmission and distribution, theoretical analyses and visions are necessary. The last cable problem, that is, the seamless power delivery as easily as information is now transmitted through the air, is one of the major technological challenges of the 21st century, and, thus, WPT technology will certainly play key role.