This paper reviews the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrids. Charger systems are categorized into off-board and on-board types with unidirectional or bidirectional power flow. Unidirectional charging limits hardware requirements and simplifies interconnection issues. Bidirectional charging supports battery energy injection back to the grid. Typical on-board chargers restrict power because of weight, space, and cost constraints. They can be integrated with the electric drive to avoid these problems. The availability of charging infrastructure reduces on-board energy storage requirements and costs. On-board charger systems can be conductive or inductive. An off-board charger can be designed for high charging rates and is less constrained by size and weight. Level 1 (convenience), Level 2 (primary), and Level 3 (fast) power levels are discussed. Future aspects such as roadbed charging are presented. Various power level chargers and infrastructure configurations are presented, compared, and evaluated based on amount of power, charging time and location, cost, equipment, and other factors.

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Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles

Wireless power transfer (WPT) using magnetic resonance is the technology which could set human free from the annoying wires. In fact, the WPT adopts the same basic theory which has already been developed for at least 30 years with the term inductive power transfer. WPT technology is developing rapidly in recent years. At kilowatts power level, the transfer distance increases from several millimeters to several hundred millimeters with a grid to load efficiency above 90%. The advances make the WPT very attractive to the electric vehicle (EV) charging applications in both stationary and dynamic charging scenarios. This paper reviewed the technologies in the WPT area applicable to EV wireless charging. By introducing WPT in EVs, the obstacles of charging time, range, and cost can be easily mitigated. Battery technology is no longer relevant in the mass market penetration of EVs. It is hoped that researchers could be encouraged by the state-of-the-art achievements, and push forward the further development of WPT as well as the expansion of EV.

Wireless Power Transfer for Electric Vehicle Applications

Inductive power transfer (IPT) has progressed to be a power distribution system offering significant benefits in modern automation systems and particularly so in stringent environments. Here, the same technology may be used in very dirty environments and in a clean room manufacture. This paper reviews the development of simple factory automation (FA) IPT systems for both today's complex applications and onward to a much more challenging application-IPT roadway. The underpinning of all IPT technology is two strongly coupled coils operating at resonance to transfer power efficiently. Over time the air-gap, efficiency, coupling factor, and power transfer capability have significantly improved. New magnetic concepts are introduced to allow misalignment, enabling IPT systems to migrate from overhead monorails to the floor. However, the demands of IPT roadway bring about significant challenges. Here, compared with the best FA practice, air-gaps need to be 100 times larger, power levels greater than ten times, system losses ten times lower to meet efficiency requirements, and systems from different manufacturers must be interoperable over the full range of operation. This paper describes how roadway challenges are being met and outlines the problems that still exist and the solutions designers are finding to them.

Modern Trends in Inductive Power Transfer for Transportation Applications

A detection method for use in a primary unit of an inductive power transfer system, the primary unit being operable to transmit power wirelessly by electromagnetic induction to at least one secondary unit of the system located in proximity to the primary unit and/or to a foreign object located in said proximity, the method comprising: driving the primary unit so that in a driven state the magnitude of an electrical drive signal supplied to one or more primary coils of the primary unit changes from a first value to a second value; assessing the effect of such driving on an electrical characteristic of the primary unit; and detecting in dependence upon the assessed effect the presence of a said secondary unit and/or a foreign object located in proximity to said primary unit.

Inductive power transfer

Inductive power transfer (IPT) was an engineering curiosity less than 30 years ago, but, at that time, it has grown to be an important technology in a variety of applications. The paper looks at the background to IPT and how its development was based on sound engineering principles leading on to factory automation and growing to a $1 billion industry in the process. Since then applications for the technology have diversified and at the same time become more technically challenging, especially for the static and dynamic charging of electric vehicles (EVs), where IPT offers possibilities that no other technology can match. Here, systems that are ten times more powerful, more tolerant of misalignment, safer, and more efficient may be achievable, and if they are, IPT can transform our society. The challenges are significant but the technology is promising.

Inductive Power Transfer

Although the use of inductively coupled power transfer (ICPT) systems for electric vehicle battery charge presents numerous advantages, a detailed design method cannot be found in the literature. This paper shows the steps to follow in the optimized design of an ICPT system and the results obtained in their application to the four most common compensation topologies, pointing out the best one in terms of minimum copper mass and proper stability conditions. A new design factor K D is proposed to select the optimum configuration for each topology. Finally, the theoretical results are validated on a 2-kW prototype with a 15-cm air gap between coils.

Optimal Design of ICPT Systems Applied to Electric Vehicle Battery Charge

Inductively coupled power transfer systems (ICPT) are an interesting alternative to conductive solutions for vehicle battery charge, particularly in electric public transport applications if operator-free fast charge is required along the route. To perform this task using ICPT systems, current solutions require an almost perfect alignment between coils in order to have optimal power transfer. This condition makes necessary a precise positioning maneuver from the driver or an electromechanic alignment system for the secondary winding, causing the process to be slow. This paper shows that it is possible to transfer rated power even with high misalignment if a suitable compensation topology is selected. The performance of the four basic compensation topologies is analyzed, and a series-parallel-series (SPS) topology is proposed, showing a suitable behavior for both the load and the power source. The theoretical results are validated in two series-series and SPS 2-kW prototypes with a 15-cm air gap between coils.

High-Misalignment Tolerant Compensation Topology For ICPT Systems

The selection of a vessel by an induction-hob user has a significant impact on the performance of the appliance. Due to the induction heating physical phenomena, there exist many factors that modify the equivalent impedance of induction hobs and, consequently, the operational conditions of the inverter. In particular, the type of vessel, which is a sole decision of the user, strongly affects these parameters. Besides, the ferromagnetic properties of the different materials the vessels are made with, vary differently with the excitation level, and given that most of the domestic induction hobs are based on an ac-bus voltage arrangement, the excitation level continuously varies. The algorithm proposed in this work takes advantage of this fact to identify the equivalent impedance of the load and recognize the pot. This is accomplished through a phase-sensitive detector that was already proposed in the literature and the application of deep learning. Different convolutional neural networks are tested on an augmented experimental-based dataset and the proposed algorithm is implemented in an experimental prototype with a system-on-chip. The proposed implementation is presented as an effective and accurate method to characterize and discriminate between different pots that could enable further functionalities in new generations of induction hobs.

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Vessel Recognition in Induction Heating Appliances—A Deep-Learning Approach

The equivalent load of an induction hob is strongly dependent on many parameters such as the switching frequency, the excitation level and the size, type, and material of the vessel. However, real-time methods with the ability to capture the variation of the load with the excitation level have not been proposed in the literature. This is an essential issue as most of the commercial induction hobs are based on an ac-bus voltage arrangement. This article proposes a method based on a phase-sensitive detector that offers an online tracking of the equivalent impedance for this type of arrangements. This algorithm enables advanced control functionalities such as clustering of vessels, material recognition, and premature detection of ferromagnetic saturation, among others. After simulation and experimental validation, the method is implemented into a prototype with a system-on-chip to verify its real-time behavior. The proposed approach is applied to different real-life situations that prove its great performance and applicability.

SoC-Based In-Cycle Load Identification of Induction Heating Appliances

In domestic induction heating applications, the modulation technique applied to the inverter has a high influence on the acoustic noise emissions. These noise emissions must be avoided, since they may be audible and annoying to the final user. This paper analyzes the acoustic noise emissions that appear when a series half-bridge resonant inverter is operated with a phase-accumulator-based modulator. This modulation technique has the advantage of operating in the frequency domain, and it is compared with the classical pulsewidth modulator regarding the audible noise generated. The frequencies of the tones in the acoustic noise spectrum are theoretically calculated from the parameters of the phase-accumulator-based modulator. The spectral flatness measure is used to quantify the number of cases in which tones are generated by the modulation. Two techniques are applied to the phase-accumulator-based modulator, and their effect is tested. Theoretical results are experimentally verified.

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Jorge Villa

Papers

Optimal Design of ICPT Systems Applied to Electric Vehicle Battery Charge

High-Misalignment Tolerant Compensation Topology For ICPT Systems

Vessel Recognition in Induction Heating Appliances—A Deep-Learning Approach

SoC-Based In-Cycle Load Identification of Induction Heating Appliances

Analysis of the Acoustic Noise Spectrum of Domestic Induction Heating Systems Controlled by Phase-Accumulator Modulators