Wireless Power Transfer for Electric Vehicles and Mobile Devices

Chun T. Rim, Chris Mi

• Publisher: Wiley-IEEE Press
• Year: 2017
• ISBN:
  9781119329022
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Ressources d'alimentation

From mobile, cable-free re-charging of electric vehicles, smart phones and laptops to collecting solar electricity from orbiting solar farms, wireless power transfer (WPT) technologies offer consumers and society enormous benefits. Written by innovators in the field, this comprehensive resource explains the fundamental principles and latest advances in WPT and illustrates key applications of this emergent technology.

Key features and coverage include:

• The fundamental principles of WPT to practical applications on dynamic charging and static charging of EVs and smartphones.
• Theories for inductive power transfer (IPT) such as the coupled inductor model, gyrator circuit model, and magnetic mirror model.
• IPTs for road powered EVs, including controller, compensation circuit, electro-magnetic field cancel, large tolerance, power rail segmentation, and foreign object detection.
• IPTs for static charging for EVs and large tolerance and capacitive charging issues, as well as IPT mobile applications such as free space omnidirectional IPT by dipole coils and 2D IPT for robots.
• Principle and applications of capacitive power transfer.
• Synthesized magnetic field focusing, wireless nuclear instrumentation, and future WPT.

A technical asset for engineers in the power electronics, internet of things and automotive sectors, Wireless Power Transfer for Electric Vehicles and Mobile Devices is an essential design and analysis guide and an important reference for graduate and higher undergraduate students preparing for careers in these industries.

Part I
Introduction

This part introduces the concept of mobile power electronics and the very basic knowledge related to wireless power transfer. The most fundamental principles and philosophy of mobile power electronics and wireless power transfer will be explained.

1
Introduction to Mobile Power Electronics

1.1 General Overview of Mobile Power Electronics

The methods of power transfer for various sources and loads have evolved since the advent of electricity in the nineteenth century. As shown in Figure 1.1, more and more loads are movable now and it has become important to provide seamless power to moving things such as electric transportation, robots, and electric airplanes. Currently, we mainly rely on electric cords and batteries to provide power to movables. As we notice daily, smartphones, tablets, and desktop computers should operate continuously even in the event of disconnection of utility power. The electric cord, however, has a limited range of powering and the battery has a limited time of powering; hence, they inevitably accompany anxiety of range and time. It is important to overcome this range and time limitation for movable things. This was the motivation for “mobile power electronics,” a term the author (Dr Rim) coined in 2010. In this light, the motto of mobile power electronics can be said to be “to supply electric energy to all movable things freely.”

Figure 1.1 Examples of modern movable things that need seamless electric power.

In general, power transfer (PT) can be classified as stationary and mobile depending on the movement of power receiving (Rx) loads, as shown in Figure 1.2. Stationary PT (SPT) traditionally has been used in the major form of electricity use, which includes fixed SPT of a firmly unchanged configuration of power systems and detachable SPT of a variable configuration of power systems. A majority of power use is still fixed STP such as high-voltage power lines, street lights, and home appliances. Nowadays, detachable STP is more widely used to charge movable things such as cable-type electric vehicles (EVs) and electric shavers, where an electric cord with a naked contact is used. These types of plugged-in chargers have an inconvenient user interface and bring exposure to potential danger of electric shock and fire.

Figure 1.2 A general classification of power transfer in terms of mobility, distance, and means of powering.

To cope with the strong demand for mobility of Rx loads, various mobile PT (MPT) technologies have been studied; they can be further classified as close MPT and remote MPT depending on the range between the power transmitting (Tx) source and the Rx loads. For the closed MPT, the WPT range is usually from a few cm to a few m. It is remarkable that the inductive, capacitive, and conductive PT correspond to L, C, and R circuit components, respectively. Each close PT uses inductive coupling, capacitive coupling, and conductive coupling between the Tx and Rx. Among the close MPTs, inductive PT (IPT) has been used widely due to its high power transfer capability at relatively low frequency, whereas capacitive PT (CPT) is not as commonly used due to its high operating frequency and small power transfer distance [1, 2]. Note that conductive PT was widely used for a century as a practical means for mobile PT until the advent of IPT.

Among remote MPT strategies, radio frequency (RF) PT and optical PT have been researched to extend the range limit of other PT techniques [3, 4]. RF PT uses electromagnetic waves of frequency ranging from MHz to GHz in practice and is quite different from IPT. For example, the Rx power density of RF PT is usually proportional to the inverse of the square of distance, but that of IPT is typically proportional to the inverse of the sixth power of distance because the Rx magnetic flux density of IPT is typically proportional to the third power of distance. Furthermore, there is no magnetic coupling between the Tx and Rx devices of the RF PT. On the other hand, the tethered PT can provide power over a flexibly long distance if properly designed [5, 6]. As depicted in Figure 1.2, wireless PT (WPT) is not only limited to close MPT such as IPT and CPT but also remote MPT such as RF PT and optical PT. Furthermore, WPT is not only electrical but also optical or even acoustic.

In the era of the ubiquitous, IPT is the most widely used [8, 58]. More mobile devices, home appliances, industry sensors, and EV chargers are becoming wireless due to their convenience, safety against electric shock, cleanness, and competitive power efficiency and price. Eventually, most devices including wearable devices, ubiquitous sensors, and smart cars will merge to the Internet of Things (IoT) and WPT will play a significantly important role in the realization of IoT, which includes compact communication devices, sensors, and power sources.

Question 1 (1) How can you classify electric shavers and vacuum cleaners that have a stretchable cable? (2) Are the items of (1) SPT or MPT? (3) What are the benefits of the classification of SPT and MPT? (4) Is there any fundamental distinction between SPT and MPT as well as IPT, CPT, RF PT, and Optical PT?

1.2 Brief History of Mobile Power Electronics

We cannot discuss mobile power or wireless power without talking about Nikola Tesla, who had carried out many experiments on WPT, as shown in Figure 1.3, and invented a “world system” for “the transmission of...