Development Trends of Inductive Power Transfer Systems

IEEJ Journal of Industry ApplicationsVol.6 No.5 pp.328–339 DOI: 10.1541/ieejjia.6.328Translated from IEEJ Transactions on Industry Applications, Vol.137 No.5 pp.445–457

Paper(Translation ofIEEJ Trans. IA)

Development Trends of Inductive Power Transfer Systems UtilizingElectromagnetic Induction with Focus on Transmission Frequency

and Transmission Power

Keisuke Kusaka∗ Member, Jun-ichi Itoh∗a)Senior Member

In recent years, inductive power transfer (IPT) systems have been actively studied. This paper describes the develop-ment trend of inductive power transfer systems since the 1970s, focusing on the transmission frequency, transmissionpower, and the coupling coefficient, on the basis of a survey of papers published by IEEJ and IEEE. The transmissionpower shows close correlation with the transmission frequency. By contrast, the coupling coefficient does not showcorrelation with either the transmission frequency or the transmission power.

Keywords: inductive power transfer, wireless power transfer, electromagnetic induction, coupling coefficient

1. Introduction

In recent years inductive power transfer (IPT) systems,which utilize the phenomenon of electromagnetic induc-tion (1)–(4), has been actively studied. IPT systems that useelectromagnetic induction convert electric energy into mag-netic energy in a primary coil, transmitting that energy to asecondary coil where it is converted back to electric energy.In order to generate an alternating magnetic field, AC cur-rent must pass through the coil, and a converter is required toconvert DC to high-frequency AC on the primary side. Sim-ilarly, a converter is required at the secondary side, where itconverts high-frequency AC to DC or commercial AC.

IPT systems are expected to be used for many applicationsin mobile devices, electric automobiles, plug-in hybrid vehi-cles, automatic guided vehicles, etc. Depending on the appli-cation, the demand may vary, but IPT systems are required tobe high-efficiency in order to clarify superiority over wiredcharging system. Examples of parameters that greatly affectthe efficiency of IPT systems include transmission power andtransmission frequency. Transmission power is determinedby the power requirements of the application. Meanwhile,the procedure of determining transmission frequency has notbeen clearly shown. Power and transmission frequency af-fect not only transmission coil loss, but also loss occurring inconverters connected to the previous and subsequent stages.However, there is a large degree of freedom such as circuit in-put/output voltage, load conditions, and the circuit topologyof the converter, in addition to the transmission power andtransmission frequency. Therefore, it is not easy to quicklydetermine the optimal parameters and circuit topology for therequired transmission power. As a result, excluding the casewhere transmission frequency is limited by standardization,

a) Correspondence to: Jun-ichi Itoh. E-mail: [email protected]∗ Nagaoka University of Technology

1603-1, Kamitomioka, Nagaoka, Niigata 940-2188, Japan

laws, etc., the transmission frequency and the circuit topol-ogy are currently decided on the basis of the experience ofthe designer when a new IPT system is designed. Makingthat determination is a tall hurdle for researchers/engineersengaged in researching and developing new IPT systems andcan thus be said to hinder research and development of newIPT systems.

In this paper, a cross-sectional survey of IPT systems pre-viously developed at any transmission power or transmissionfrequency is performed, in order to uncover the relationshipbetween these parameters in IPT systems developed thus far.Also, a clear description of the configurations of widely-usedconverters at various transmission powers and transmissionfrequencies is provided.

The relationship between transmitted power, transmissionfrequency, and circuit topology are compiled as the collec-tive knowledge to obtain guidelines when researching newIPT systems for determining the appropriate transmission fre-quency and circuit topology if transmission power is given asa required specification. It is believed that these guidelineswill promote research and development of IPT systems andbe useful for development in the field of IPT.

2. Development Trends

In this paper, some of the transactions and conference pa-pers published by IEEJ and IEEE, etc. between 1978 andSeptember 2015 whose title or main body included the termsshown in Table 1 are surveyed. Note that this paper does notmake a distinction between the magnetic resonance couplingand the electromagnetic induction because it is recognizedthat the magnetic resonance coupling is as part of the electro-magnetic induction in a recent study (5).2.1 Transmission Frequency Over Time Figure 1

shows the change over time (years) in transmission frequencyin IPT systems utilizing electromagnetic induction (6)–(197).Here, Fig. 1(a) shows the entire frequency range and (b)is an enlarged view of only the low-frequency range. In

c© 2017 The Institute of Electrical Engineers of Japan. 328

Development Trends of Inductive Power Transfer Systems（Keisuke Kusaka et al.）

Table 1. Terms for survey

(a) 100 Hz to 100 MHz

(b) Up to 200 kHz

Fig. 1. Trend for transmission frequency of inductivepower transfer

Fig. 1, the x-axis shows the year that the paper was pub-lished. The transmission frequency used in IPT systems isintimately related to the development of electrical power con-version technology. In 1978, J.G. Bolger, et al. were thefirst to demonstrate IPT systems that used electromagneticinduction in U.S. (197). In this paper, an electric generator me-chanically coupled to an electric motor was used as a high-frequency power source (150 to 210 Hz) in order to achievehigh-frequency output. One reason that this structure neededto be used was that, at the time, semiconductor power con-version technology was in the process of being developed,and a method for continuously and efficiently generating thefrequency output required for IPT had not yet been estab-lished. Later, during the stage when the power transistor

was developed and MOSFET, IGBT, etc. were being applied,these began to be used in IPT systems as well. For example,in 1991, A. Esser, et al. performed IPT at 25 kHz by usingan IGBT capable of withstanding 650 V as a rotary trans-former for multiaxis robots (188). Also, in 1992, IPT was re-ported with 200 kHz transmission power with a class C am-plifier that used MOSFET (189).

IPT systems that were first achieved in this way at thelow frequency of several hundred Hz gradually advanced tohigher frequencies as switching devices were developed. Inrecent years, the systems are classified into the two categoriesof frequency in particular, a low frequency between several10 s of kHz to several 100 s of kHz and high frequency atthe level of MHz and greater. Because semiconductor elec-tric power conversion circuits have been widely used in thelow-frequency bandwidth since then, the advantage to usinglow frequencies is that the electrical conversion technologyhas already been established. That fact also prompted thefrequency of IPT systems for automobiles to be standardizedaround 85 kHz (198). Meanwhile, a 2007 paper by A. Kurs,et al. of the Massachusetts Institute of Technology on IPTsystem around 10 MHz greatly affected the IPT systems inthe MHz or greater frequency range (170). In (170), because theprinciple of inductive power transmission had been explainedaccording to the coupled mode theory, the phenomenon hadbeen recognized that it was the different phenomenon to theelectromagnetic induction. Thus, it was initially called “mag-netic resonance”, “magnetic resonance coupling”, etc. There-fore, many engineers and researchers worked to develop anIPT system using the MHz range. As a result, there was asudden increase in reports on IPT systems using the MHzrange at the boundary announced by MIT. However, cur-rently, because the technology reported MIT has begun tobe recognized as a part of the electromagnetic induction phe-nomenon (5), the MHz range is only used primarily in researchaiming to miniaturize transmission systems.2.2 Relationship between Transmission Frequency

and Transmission Power Figure 2 shows the relation-ship between transmission frequency and transmission powerin the IPT systems reported to the present. The figure is di-vided according to the configuration of the converter, withFig. 2(a) showing the configuration of a primary converterand Fig. 2(b) showing the configuration of a secondary con-verter. Research and development are being conducted onIPT systems in a wide electrical power range, from a lowcapacity of less than 1 W to a high capacity of 52 kW. Oneexample of a high-power IPT system is the 52 kW, 20 kHzIPT system that is applied in large electric automobiles, suchas buses (139). Research is also being conducted on IPT sys-tems for railway vehicles. A transmission of several hun-dred kW or greater is required for railway vehicles (23), andalthough studies aimed at increasing the capacity of IPT sys-tems are ongoing, such systems are presently in the studyphase using scale models. Conversely, induction transfer be-low 10 W is also frequently observed (10) (106) (110). The existenceof reports on this type of low power transmission are one rea-son why the maximum supplied power in the Qi Standardsestablished by WPC was 5 W. However, as of 2015, new stan-dards with the maximum supplied power at 15 W continueto be established, and a gradual increase in the transmission

329 IEEJ Journal IA, Vol.6, No.5, 2017


(a) Classification by topology of primary converters

(b) Classification by topology of secondary converters

Fig. 2. Relation between transmission frequency andtransmission power

power of systems compatible with Qi standards is predictedin the future. Meanwhile, in IPT systems from several MHzto more than several tens of MHz, the transmission power isfrequently several mW to several hundreds of mW. This is be-cause research efforts aimed at increasing frequency includea theoretical validation that uses a vector network analyzer(VNA).

Turning to the transmission frequency, there have beenmany reports on IPT systems that use frequencies of around20 kHz. Because approximately 20 kHz is typically the car-rier frequency that is widely used in power electronic circuits,introducing these IPT systems into converters is easy. Thereis also the advantage that 20 kHz is outside the audible fre-quency range. The next most commonly seen frequency isaround 100 kHz. This has contributed to the fact that IPT sys-tems for automobiles have been standardized in the 85 kHzrange (79 kHz to 90 kHz) in recent years (198).

Turning now to the relationship between transmissionpower and transmission frequency, Fig. 2 shows an intimaterelationship between these two parameters. In order to in-crease the capacity of IPT systems, the transmission fre-quency must be lowered. Meanwhile, although it is pos-sible to miniaturize the coil by increasing the transmissionfrequency, doing so limits the amount of power that can besupplied. Therefore, the product of the transmission fre-quency f [Hz] and the transmission power P [W] is intro-duced as the new index kp f = Pf [W/s]. In Fig. 2, the IPTsystems reported thus far have been plotted within the range

of kpf < 3.3 × 109 [W/s]. Note that this only shows the factthat the systems reported thus far simply exist in that rangeand does not mean that the ability to increase the frequencyand capacity of an IPT system is physically limited thereto.However, it means that there is a record of IPT system devel-opment in this range. Therefore, researchers and engineerswho will attempt to begin research on IPT systems in the fu-ture are recommended to select transmission power and trans-mission frequency within or near this range. For example,when the transmitted power is 100 kW, an IPT system witha transmission frequency of approximately less than 33 kHzis likely to be achieved. Conversely, if the transmission fre-quency is limited to 85 kHz because of standardization, etc.,the transmission power that would be easy to achieve wouldbe approximately 39 kW.

Next, the configuration of primary converters is examined.In Fig. 2(a), the difference in the symbols shows the configu-ration of a primary converter used to drive an IPT unit. Fig-ure 3 shows the converters used in these IPT systems. Thefigure shows a circuit using MOSFET, but there are cases inwhich IGBT is used as well. The most commonly used con-verter is the full bridge inverter, followed by the half-bridgeinverter. There are also reports of the use of E-class invert-ers (71) (97) (106) (128) (129), and converters derived from half-bridge in-verters (31), the matrix converters as the primary converters in-cluding a function of front end converters (125) (159). This pa-per defines full-bridge inverters as “inverters composed of 2legs, with 2 switches per legs that are capable of self-turn-onand self-turn-off (hereinafter, “active switches”). Also, half-bridge inverters are considered to be “composed of 1 leg, with2 active switches per leg”.

Examples of full-bridge inverters, the transmission poweris used in the wide range of several hundred Watts to 50 kWin a frequency range between 10 kHz and 100 kHz.

Full-bridge inverters have always been the most commonlyused topologies in the field of power electronics and thus havea long performance record in these frequency ranges, whichis believed to be why full-bridge inverters are easy to apply.Also, even if the capacity is increased, the heat generated byeach switching device is shared over four switching devices,so the full-bridge inverter can be cooled easily even duringhigh power transmission. However, considering that fourswitching devices are required and that an insulated powersupply for driving the gate of the upper switch must be pre-pared, full-bridge inverters are disadvantageous in low-powerIPT systems that require reduced cost. Because of these rea-sons, the full-bridge system is appropriate for large-capacitysystems. This circuit itself has had applications for manyyears, and it is already an established technology. However,there has not been enough discussion as to control meth-ods. If this circuit performs square-wave driving, controlof DC voltage will be required to control the output power,and a chopper circuit will need to be inserted in the previousstage (161). Meanwhile, if the output voltage is made to be a 3-level waveform by controlling the phase shift for this circuit,electric power can be controlled without a chopper circuit inthe previous stage of the full bridge inverter. However, therewill be increased switching loss in the inverter and copperloss in the coil caused by the high frequency (199). There hasnot yet been a discussion of the advantages and disadvantages



(a) Full-bridge inverter (b) Half-bridge inverter

(c) E-class inverter (71) (97) (106) (128) (129)

(d) Modified half-bridge inverter (31)

(e) Three-phase to single phase matrix converter for inductive power transfer (125)

(f) Single-phase to single phase matrix converter for inductive power transfer (159)

Fig. 3. Primary converters

of a system that accounts for all of these losses, the loss inthe converters and transmission coil. Future study of this isawaited.

Half-bridge inverters are particularly frequently used inIPT systems around 1 MHz and 1 kW (28) (56) (163) (176). Also, theoverall applied number does not reach that of the full-bridgeinverter. Also, the maximum transmission power of systemsthat use half-bridge inverters are 3 kW according to the lit-erature (176), and there are many cases in which they are used

at relatively small power in comparison with the full-bridgeinverter. Half-bridge inverters have the advantage that theyonly need two active switches. However, the output voltageof the half-bridge inverter is one-half that of the full-bridgeinverter, so the voltage transfer ratio is low. Therefore, at thesame DC voltage, they must allow a flow of current twicethat of the full-bridge inverter in order to achieve the samepower and thus have increased copper loss in the transmis-sion coil and conduction loss the converter. Therefore, therated current of the switching device cannot be decreased,and the half-bridge inverter cannot contribute to cost reduc-tion. However, because there is only one switching device,which has a floating source, the driving circuit cost can bereduced. For these reasons, the applicable range of the half-bridge inverter is limited in comparison with the full-bridgeinverter, and it is used in devices with moderate capacity.

IPT systems that use linear amplification circuits at highfrequencies of 5 MHz or greater have been frequently re-ported (91) (101) (112) (165) (169)–(171). That is because low-cost powersupplies are uncommon at ranges of several MHz and higher.However, the efficiency of linear amplification circuits is low:the theoretical efficiency of an A-class converter is 50%, andeven if a B-class converter is used, the maximum theoreticalefficiency is 78.5%. As a result, high efficiency is not desiredwhen these power supplies are used.

The E-class inverter shown in Fig. 3(c) is frequently usedin high-frequency IPT systems. The E-class inverter achievesthe zero-voltage switching (ZVS) and zero-derivative switch-ing (ZDS) (128).

However, due to the load, the E-class switching conditionscannot always be satisfied, and the electric power conver-sion efficiency suddenly drops. This circuit is composed of 1switching device, and the source terminal has the same poten-tial as the ground potential of the primary circuit, so isolatedgate drive circuit is not necessary for the operation. Becauseof these reasons, the E-class inverters are primarily used inlow-power applications where there is a stronger demand forreduced cost. Note that the voltage printed on the devicevaries depending on the load, so a voltage greater than theinput DC voltage might be printed there. Because voltagestress on the switching device is large, it has not believed tobe suitable for capacity increases. However, with the applica-tion of high-voltage tolerant Silicon Carbide (SiC) MOSFET,which is currently being actively developed, E-class inverterscan be expected to have more favorable properties in largeelectrical power systems than was true previously.

Figure 3(d) shows the configuration of a circuit that inte-grates a power factor correction (PFC) circuit and a high-frequency inverter. Compared with a diode bridge rectifierand half-bridge inverter, this circuit is capable of PFC opera-tions and boost voltage operations without additional switchdevices, so it is beneficial for reducing costs. However, be-cause the power is controlled by the switching frequency,it is not suited for mainstream IPT, which uses resonance.There are also issues with conversion efficiency, because ofthe increased number of switching devices where the currentpasses through during the inductor charging period.

Figure 3(e) shows a circuit in which a front end converterand a frequency inductor have been integrated by using a ma-trix converter. It uses less switching devices than systems that



combine the PWM rectifier and full-bridge inverter, and it canachieve high power density because there are no DC links.However, the switching frequency and the transmission fre-quency of the front end converter must be equal, owing torestrictions on circuit operations. Therefore, if transmissionfrequency is decided by standardization, etc. that decides theswitching frequency of the front end converter. The powerloss of the part of the matrix converter as the front end con-verter will be increased because the operating frequency ofthe matrix converter have to be operated under the differentfrequency from the optimum frequency in which the matrixconverter will obtain maximum efficiency. Also, in the mod-ulation method proposed in (125), soft switching was unable tobe achieved. In the future, the circuit configuration must beimproved and a control method established so that switchingloss can be realized.

Similar to Fig. 3(e), Fig. 3(f) shows a circuit that integratesa front end converter and a high-frequency inverter by us-ing a matrix converter, but this circuit is different in that ituses a single-phase/single-phase matrix converter. In this cir-cuit, the switches of the grid-side converter switch at polaritychange of the grid voltage, so less switching loss occurs in thegrid-side switches. However, in this circuit, the single-phasepower ripple cannot be absorbed on the primary side of theIPT system, so it must be absorbed in the on the secondaryside. As a result, it can only be applied to systems that canallow a high-capacity energy buffer to be on the secondaryside. By combining this circuit with a circuit capable of ab-sorbing the power ripple with a small capacity buffer, suchas an active power decoupling circuit, an application of thistopology will be wide.

Next, the configurations of a secondary converter are paidattention. In Fig. 2(b), the differences in the symbols showthe configuration of a secondary converter. The points in thefigure represented by white circles are where the rectifier isdepicted as a black box in the experimental instrument con-figuration, and they can be used to infer from the text, tables,and figures that a diode bridge rectifier has been used. Also,the plots shown in a rhombic shape in the figure do not use asecondary converter, and they represent references in whichsystems were validated with a resistance load. These corre-spond to reports that focused on primary converters or reportsthat focused on the characteristics of transmission coils them-selves.

Figure 4 shows an example of a converter used in a sec-ondary side of an IPT system. Note that although the ac-tive switches in the diagram are shown as MOSFET, thereare cases in which IGBT is applicable. The most fre-quently used secondary converter is a full-bridge rectifier,followed by a full bridge rectifier that uses active switchessuch as MOSFET, followed by a bridgeless rectifier. Also,the use of a half-bridge rectifier (voltage doubler recti-fier) (16) (43) (131), a single-phase, full-wave rectifier (7), a bridge-less rectifier (11) (81) (103) (126), a current double rectifier (67), a D-class rectifier (129), an E-class rectifier (106) (126), etc. have beenreported.

The diode bridge rectifier in Fig. 4(a) can be used in a widerange, at any transmission frequency. This is because thediode rectifier has many applications, so in addition to beingable to be applied in large power systems, it is easy to apply

(a) Full-bridge rectifier (b) Full-bridge rectifier withactive switches

(c) Half-bridge rectifier (16) (43) (131) (d) Single-phase full-waverectifier (7)

(e) Bridge-less rectifier (81) (103) (111) (126) (f) Current doubler rectifier (67)

(g) Class-D rectifier (129) (h) Class-E rectifier (106) (126)

Fig. 4. Secondary converters

in high-frequency ranges, because control is not required.While this circuit has the simplest configuration, because thecircuit itself has no control function, a chopper circuit, etc. istypically connected to the subsequent stage in order to pro-vide control (161). However, the optimization method on thedesign of these circuits for the system overall has not beenshown and is expected to be studied in the future.

The full-bridge rectifier in Fig. 4(b) that uses activeswitches is the next most frequently used rectifier after thediode rectifier. There are many reports in which the diodeis exchanged into the active, in order to provide improvedefficiency through synchronous rectification and to add func-tions, such as bidirectional IPT operations and output volt-age control functions. However, IPT systems are driven byhigher frequency than commercially-used frequency. There-fore, PWM is infrequently used, and square wave operation isgenerally performed in the secondary converter as well, sim-ilar to the primary converter. Consequently, secondary con-verters using active switches are primarily used in the trans-mission frequency range from 10 to 50 kHz. Because theswitching device is switched in synchronization with the zerocross of the rectifier input current, the increase of switchingloss can be limited.



If the active switches perform synchronous rectifications,the conduction loss can be reduced in comparison with thediode bridge rectifier. The circuit topology has alreadybeen established, but general questions have not yet beenanswered; for example, whether a system where an activeswitch is used to provide a control function or a system wherean additional circuit such as a chopper circuit is attached tothe full-bridge rectifier would be more efficient or more su-perior from a power density standpoint.

Meanwhile, there are few reports in which the half-bridgerectifier of Fig. 4(c) is used—there were only three re-ports (16) (43) (131). This circuit is also called a voltage doublerrectifier, and it can output a voltage twice as large as the full-bridge rectifier with two diodes. However, it has problems,such as the diode requiring double the voltage tolerance andthe output voltage ripple increasing, so there is not a great ad-vantage to using the half-bridge rectifier. Figure 4(d) showsa single-phase full-wave rectifier provided with a center tapin the secondary coil. This circuit achieves a rectifying op-eration with two diodes, but only one-half of the DC voltageinduced by a secondary coil. Although this circuit must beadditionally provided with a center tap in the secondary coil,it is easily possible in IPT. Meanwhile, the current passesthrough only two diodes, half that of the full-bridge recti-fier, so reduced conduction loss can be expected. Therefore,an IPT system with high efficiency can be achieved througha design that integrates this circuit with a transmission coil.

Figure 4(e) is a circuit in which only the lower switch ofthe diode bridge rectifier is used as the active switch. Thistopology is also called a bridgeless rectifier. The lower switchinduces phase shift control between the legs, and the outputvoltage can be controlled by the short-circuit period of thesecondary coil produced by providing the lower switch witha simultaneous on time (103) (111) (199). This affords the advantagethat the output voltage can be controlled without additionaldevices. When switching devices turn-on or turn-off at zerocross of the input current by detecting the zero cross point ofthe input current, the increase in switching loss is minimized,but control methods are limited (199). If switching is performedout of sync with the zero cross point of the current, switchingloss cannot be prevented (103) (111). In this circuit, it is not stillclear which is more advantageous from an efficiency stand-point: a chopper circuit is connected in a subsequent stage ofa full-bridge rectifier or voltage is controlled by a bridgelessrectifier.

Figure 4(f) shows a current doubler rectifier. The charac-teristic feature of this circuit is that the output current doubleswith respect to the input current. However, a large inductoris required to suppress the current ripple, so the system isdifficult to miniaturize. Also, because the current continuesto flow into these inductors, the loss that occurs in the in-ductor cannot be disregarded, and this circuit also shows noparticular superiority over others in terms of efficiency. Inaddition, an inductor and a smoothing capacitor are insertedin the pathway of the load current, so in an IPT system thatuses resonance, a resonance circuit must be designed to ac-count for the impendence of the inductor and the smoothingcapacitor.

Figures 4(g) and 4(h) show a D-class rectifier and an E-class rectifier, respectively. The D-class rectifier does not use

(a) Transmission power and coupling coefficient

(b) Transmission frequency and coupling coefficient

Fig. 5. Relation among coupling coefficient, transmis-sion frequency and transmission power

an active switch to perform rectifier operations, and the E-class rectifier uses one active switch. This is advantageousfor operations at high frequencies. However, while there arefew switches where the current passes through, a device withpoor characteristics must be used because high-voltage willbe applied to the switching device. It causes the efficiencyproblems. Therefore, these rectifiers are mainly used in high-frequency and low-power applications. The development ofa high-voltage-tolerant SiC device in the future is expected togreatly improve the efficiency.2.3 Coupling Coefficient Figure 5 shows the rela-

tionship between transmission power and transmission fre-quency and the coupling coefficient. Figure 5(a) shows therelationship between the transmission power and the cou-pling coefficient. Figure 5(b) shows the relationship betweenthe transmission frequency and the coupling coefficient. Asignificant correlation between the coupling coefficient andtransmission power is not observed, and the coupling doesnot affect the transmission power. Similarly, no significantcorrelation was observed between the coupling coefficientand transmission frequency.

However, it is noted that IPT systems with a coupling coef-ficient greater than 0.1 have not been reported at frequenciesover 10 MHz. That is because no effective magnetic materi-als exist at frequencies in excess of 10 MHz, and an air corecoil must be used, which ultimately decreases the couplingcoefficient.2.4 Classification by Application Figure 6 shows

the relationship between transmission power/transmissionfrequency and applications of IPT systems that have beenreported in (6)–(197). Note that a paper that does not clearlydescribe applications of IPT systems were excluded in thispaper. Also, if a paper described three or more types of ap-plications, it was considered not to constitute research and



Fig. 6. Classification by applications of inductive powertransfer systems

development aimed at specific applications, and it was ex-cluded from this study.

When examining the data according to the application, IPTsystems for automobiles were the most frequently reported.A transmission power in the range of 1 kW to 50 kW and atransmission frequency in the range of 10 to 100 kHz wereprimarily used. Standardization of IPT systems for automo-biles has been ongoing (198), and reports of IPT systems thatuse this frequency range are expected to increase in the fu-ture.

Meanwhile, many IPT systems applied in industrial de-vices, such elevators or automated guided vehicles (AGV),have been reported. There is a long history of IPT systemsfor these machines, which have been developed since the lat-ter half of the 1990s. Frequently reported systems use a fre-quency of 10 kHz, which is the current realistic switching fre-quency of an active switch.

Some IPT systems have also been reported for railway ap-plications, although the number of reports was small. As pre-viously described, power ranging from several kW to severalhundred kW is required for railway applications, so most IPTsystems use a frequency of 10 kHz or less.

As for IPT systems for household appliances, there werefew plotted points in the figure, because there are few reportsof applications in household appliances themselves. How-ever, in many reports, they are listed as an example of whereapplications of IPT systems can be useful. Presently, IPTsystems for household appliances do not show any trends inrelation to specific transmission frequency or power, whichare decided according to the individual application. How-ever, the standardization of IPT systems related to householdappliances may be published (198), resulting in future limita-tions of transmission frequency and transmission power forthese applications.

3. Conclusion

In this report, the survey of IPT systems from the stand-point of transmission power, transmission frequency, cou-pling coefficient, and converter topology is reported. Thetransmission frequency of IPT systems that essentially be-gan to be studied in the 1980s has been increasing, owing tofactors such as the development of semiconductor switches.In particular, Ref. (170) in 2007 prompted a rapid increase intransmission frequency, and IPT systems using frequencies

in MHz began to be reported. However, it became difficultto find any advantage that outweighed the greater loss associ-ated with increasingly higher frequencies, and the flurry ofresearch on IPT systems using these frequency ranges be-gan to dwindle over the past few years. Although researchaimed at miniaturizing and reducing the weight of transmis-sion coils by increasing frequency has also been reported,the effect on miniaturizing the transmission coil through in-creased frequency is limited, considering a coil misalign-ment. Against this backdrop, there has been a spike in reportson IPT systems with frequencies of several tens of kHz toseveral hundreds of kHz, which can achieve high efficiency,including converters.

In IPT systems, there is a high degree of freedom in thesystem with respect to the required transmission power, in-cluding the transmission frequency, the input/output voltageand load conditions of the current, the current topology, etc.,so it is difficult to select the optimal configuration for effi-ciency and power density. However, the results of cross-sectional studies of IPT systems reported thus far have showna relationship between transmission power, transmission fre-quency, and circuit topology. These parameters can be deter-mined based on these relationships to derive general guide-lines for IPT systems. For example, a converter with a bridgeconfiguration that can handle increased capacity and that hasa record of performance is effective in systems that use a fre-quency of several kW to several tens of kW. In the future, weanticipate progress on discussions about efficiency and powerdensity that take into account input/output voltage (current)and the combination of a converter connected to the previousand subsequent stage of this converter.

Meanwhile, in systems at several tens of Watts to sev-eral hundreds of Watts with applications in household appli-ances, etc., a transmission frequency in the several hundredsof kHz is often used. Resonance-type converters that can ef-fectively decrease switching loss in this frequency range willbegin to have applications, in addition to converters with abridge structure. In order to expand the applicable rangeof resonance-type converters, transmission power must beincreased and switching device stress reduction technologymust be established.

Furthermore, in applications at low power and high fre-quency (MHz), an E-class inverter with one switching deviceis used in order to realize a simple circuit configuration capa-ble of decreasing switching loss and conduction loss. Voltagestress reduction technology for switching devices and robust-ness against resonance parameter variation are highly antici-pated in these converters. Owing to the development of SiCdevices with high voltage tolerance in these circuits, applica-tions can be expected for high-power IPT systems for whichapplications were previously difficult to find.

Additionally, the relationship between the coupling coeffi-cient, transmission power, and the transmission frequency isshown. Any correlation among these parameters is not ob-served. In other words, it is possible the IPT system trans-mits desired power regardless the magnetic coupling with anarbitrary frequency. However, this result does not necessarilyensure an efficient power transmission.

After discussing the trends of IPT systems, standardizationmust be mentioned. IPT systems such as those in electric



vehicles and household appliances are being standardized,which is expected to limit the usable transmission frequencyrange. From the perspective of standardization, the maxi-mum transmission power of IPT systems for passenger vehi-cles is currently 7.7 kW, and the IPT systems reported thusfar are frequently below 7.7 kW. However, considering thehistory of power conversion technology, the consumed powerof devices tends to increase over that envisioned at the startof development. For example, the initial normal charging forwired electric automobile chargers was 3.3 kW, but 50 kWrated chargers to support rapid charging, and 120 kW ratedchargers for ultra-fast charging were developed and began tobe used. Because capacity increases in this manner, the IPTsystem can never be expected to become widely utilized if itmaintains its current 7.7 kW transmission power. Therefore,we hope there will be much research on IPT systems for elec-tric automobiles, particularly with respect to increased capac-ity for transmission power, countermeasures for handling theconduction and radiation noise caused by that increased ca-pacity, as well as heat dissipation strategies, and technologyfor protecting the human body.

References

( 1 ) Japan patent office: “Japan patent office report of patent application trends inthe field of wireless power transfer on FY2014” (2015) (in Japanese)

( 2 ) J. Dai and D.C. Ludois: “A Survey of Wireless Power Transfer and a Criti-cal Comparison of Inductive and Capacitive Coupling for Small Gap Appli-cations”, IEEE Trans. On Power Electronics, Vol.30, No.11, pp.6017–6029(2015)

( 3 ) M.P. Kazmierkowski and A.J. Moradewicz: “Contactless Energy Transfer(CET) Systems - A Review”, 15th International Power Electronics and Mo-tion Control Conference, pp.4–6 (2012)

( 4 ) G.A. Covic and J.T. Boys: “Modern Trends in Inductive Power Transfer forTransportation Applications”, IEEE Journal of Emerging and Selected Topicsin Power Electronics, Vol.1, No.1, pp.28–41 (2013)

( 5 ) T. Imura and Y. Hori: “Unified Theory of Electromagnetic Induction andMagnetic Resonant Coupling”, IEEJ Trans. IA, Vol.135, No.6, pp.697–710(2015)

( 6 ) H. Ayano, H. Nagase, and H. Inaba: “Highly Efficient Contactless ElectricalEnergy Transmission System”, IEEJ Trans. IA, Vol.123, No.3, pp.263–270(2003)

( 7 ) H. Abe, H. Sakamoto, and K. Harada: “A Nobel Method of Output Volt-age Stabilization with Respect to Load Current Variation in the Non-ContactEnergy Transfer”, IEEJ Trans. IA, Vol.123, No.11, pp.1285–1294 (2003)

( 8 ) Y. Kaneko, S. Matsushita, Y. Oikawa, and S. Abe: “Moving Pick-Up TypeContactless Power Transfer Systems and their Efficiency Using Series andParallel Resonant Capacitors”, IEEJ Trans. IA, Vol.128, No.7, pp.919–925(2008)

( 9 ) H. Irie, N. Minami, H. Minami, and H. Kitayoshi: “Non-Contact EnergyTransfer System Using Immittance Converter”, IEEJ Trans. IA, Vol.120,No.6, pp.789–794 (2000)

(10) H. Abe, H. Sakamoto, and K. Harada: “Load matching for Non-ContactCharging System”, IEEJ Trans. IA, Vol.119, No.4, pp.536–543 (1999)

(11) H. Irie, H. Taike, H. Minami, and H. Kitayoshi: “Equivalent Circuit of Pick-Up-Coil in Non-Contact Energy Transfer System”, IEEJ Trans. IA (letter),Vol.118, No.10, pp.1228–1229 (1998)

(12) H. Irie and Y. Tahatra: “Cascade Configuration of T-LCL-Type and T-CLC-Type Immittance Converters in Non-Contact Energy Transfer Systems”, IEEJTrans. IA, Vol.129, No.5, pp.511–518 (2009)

(13) Y. Kaneko, N. Ehara, T. Iawata, S. Abe, T. Yasuda, and K. Ida: “Comparisonof Transformer Winding Methods for Contactless Power Transfer Systems ofElectric vehicle”, IEEJ Trans. IA, Vol.130, No.6, pp.734–741 (2010)

(14) H. Matsumoto, Y. Neba, K. Ishizaka, and R. Itoh: “3-phase ContactlessPower Transfer System Tacking Account of Mutual Inductance”, IEEJ Trans.IA (letter), Vol.130, No.8, pp.1039–1040 (2010)

(15) S. Shindo, Y. Terae, I. Ando, K. Ohishi, M. Ogawa, and H. Takano: “AMethod of Single Phase High Frequency Inverter Based on Tracking Control

to Load Resonant Frequnecy”, IEEJ Trans. IA, Vol.131, No.8, pp.1078–1086(2011)

(16) M. Chigira, Y. Nagatsuk, Y. Kaneko, S. Abe, T. Yasuda, and A. Suzuki:“Novel Core Structure and Iron-loss Modeling for Contactless Power Trans-fer System of Electric Vehicle”, IEEJ Trans. IA, Vol.132, No.1, pp.9–16(2012)

(17) T. Tohi, Y. Kaneko, and S. Abe: “Maximum Efficiency of Contactless PowerTransfer Systems using k and Q”, IEEJ Trans. IA (letter), Vol.132, No.1,pp.123–124 (2012)

(18) K. Takuzaki and N. Hoshi: “Consideration of Operating Condition ofSecondary-side Converter of Inductive Power transfer System for ObtainingHigh Resonant Circuit Efficiency”, IEEJ Trans. IA, Vol.132, No.10, pp.966–975 (2012)

(19) H. Matsumoto, Y. Neba, K. Ishizaka, and R. Itoh: “Power Factor Compen-sator for Contactless Power transfer System Connecting to Full-Bridge DiodeRectifier”, IEEJ Trans. IA, Vol.133, No.6, pp.618–626 (2013)

(20) S. Kawano, E. Hiraki, T. Tanaka, and M. Okamoto: “A High-Frequency LinkAC-AC Converter for Contactless Power Supply System in Parking Tower”,IEEJ Trans. IA, Vol.134, No.2, pp.139–146 (2014)

(21) H. Matsumoto, R. Nakashima, Y. Neba, and H. Asahara: “Proposal and Ver-ification of Two-Layer Three-Phase Contactless Power transformer”, IEEJTrans. IA, Vol.135, No.5, pp.539–547 (2015)

(22) T. Kai and K. Throngnumchai: “A Study on Receiver Circuit Topology ofnon-contact Charger for Electric Vehicle”, IEEJ Trans. IA, Vol.132, No.11,pp.1048–1054 (2012)

(23) K. Yamamoto, T. Maruyama, K. Kondo, and T. Kashiwagi: “A Method forDesigning a High-Power Contactless Power Transformer Considering Reac-tive Power”, IEEJ Trans. IA, Vol.133, No.3, pp.378–385 (2013)

(24) S. Kitazawa, K. Kondo, and T. Kashiwagi: “An Evaluation of Power FlowControl of the Power Conversion Circuit for Contactless Power TransformerSystem at the Coil Misalignment”, IEEJ Trans. IA, Vol.133, No.5, pp.518–525 (2013)

(25) S. Mochizuki, S. Nakadachi, H. Watanabe, S. Sakaino, Y. Kaneko, S. Abe,and T. Yasuda: “Bidirectional Contactless Power Transfer System expand-able from Unidirectional Systems”, IEEJ Trans. IA, Vol.133, No.7, pp.707–713 (2013)

(26) Y. Nakata and J. Itoh: “PDM Control Method for a Matrix Converter Con-verting Several-Hundred-kHz Single-Phase Input to Commercial FrequencyThree-Phase Output”, IEEJ Trans. IA, Vol.134, No.1, pp.41–48 (2014)

(27) T. Yamanaka, I. Fujita, Y. Kaneko, S. Abe, and T. Yasuda: “Cooling Struc-ture for Large Capacity H-shaped Core Contactless Power Transformers forElectric Vehicles”, IEEJ Trans. IA, Vol.134, No.3, pp.370–375 (2014)

(28) S. Ojika, Y. Miura, and T. Ise: “Evaluation of Inductive ContactlesssPower Transfer Outlet with Coaxial Coreless Transformer”, IEEJ Trans. IA,Vol.135, No.1, pp.49–57 (2015)

(29) H. Abe, T. Akiyama, M. Ozaki, and H. Kohara: “Simple Equivalent Circuitfor a Wireless Power Transfer System Using a Repeating Coil and EffectsConfirming the Simplification in the Output Voltage Estimation”, IEEJ Trans.IA, Vol.135, No.6, pp.679–688 (2015)

(30) H. Matsuoka, S. Watanabe, and T. Koseki: “Research on the CharacteristicChange in an Inductive-coupling-type Contactless Power Transformer for aRailway According to the Core Shapes and Misalignment Utilizing a T-typeEquivalent Circuit”, IEEJ Trans. IA, Vol.135, No.7, pp.746–754 (2015)

(31) K. Sugimori, H. Sakamoto, and K. harada: “One Converter Type Contact-lessCharger for Electric Vehicles”, IEEJ Trans. IA, Vol.118, No.11, pp.1253–1259 (1998)

(32) F. Anan, K. Yamasaki, K. Harada, H. Sakamoto, K. Sugimori, and M. Inoh:“A Charger with a Magneto-Inductive Connector”, IEEJ Trans. IA, Vol.116,No.3, pp.245–250 (1995)

(33) T. Nishimura, T. Eguchi, T. Inoue, M. Saito, Y. Maejima, M. Majima, andK. Hirachi: “A Transcutaneous Power Supply System for a RechargeableCardiac Pacemaker Battery”, IEEJ Trans. IA, Vol.117, No.9, pp.1085–1091(1997)

(34) D. Gunji, T. Imura, and H. Fujimoto: “Fundamental Research on ControlMethod for Power Conversion Circuit of Wireless In-Wheel Motor usingMagnetic Resonance Coupling”, IEEJ Trans. IA, Vol.135, No.3, pp.182–191(2015)

(35) K. Shimamura, M. Koizumi, Y. Mizuno, and K. Komurasaki: “Effect of Ax-ial Slit on metallic Tube for Wireless Power Transfer Via Magnetic Reso-nance Coupling—Application of Magnetic-Resonance Coupling Techniquesfor Infrastructure Diagnostics—”, IEEJ Trans. IA, Vol.135, No.7, pp.787–793(2015)

(36) J. Shibata, K. Kaneko, K. Ohishi, I. Ando, M. Ogawa, and H. Takano: “FineOutput Voltage Control Method considering Time-Delay of Digital InverterSystem for X-ray Computed Tomography”, IEEJ Trans. IA, Vol.131, No.11,pp.1331–1337 (2011)



(37 ) T. Mizuno, T. Ueda, S. Yachi, R. Ohtomo, and Y. Goto: “Dependence ofEfficiency on Wire Type and Number of Strands of Litz Wire for WirelessPower Transfer of Magnetic Resonant Coupling”, IEEJ Journal of IndustryApplication, Vol.3, No.1, pp.35–40 (2014)

(38) T. Hiramatsu, H. Xiaoliang, M. Kato, T. Imura, and Y. Hori: “ExperimentalVerification of Feedforward Controller for Wireless Charging Power Controlthrough Receiver Side Voltage Control”, IEEJ JIASC2014, No.2-13 (2014)

(39) T. Matsumura, Y. Kaneko, and S. Abe: “An Operating Method of Inverterwith Capacitive Load in Wireless Charger for Electric Vehicles”, IEEJ JI-ASC2013, No.4-6 (2013)

(40) M. Jo, Y. Sato, Y. Kaneko, and S. Abe: “Reduction of Harmonic CurrentFlowing Transformer of Wireless Charging System for Electric vehicles”,IEEJ JIASC2013, No.4-7 (2013)

(41) I. Fujita, T. Yamanaka, Y. Kaneko, S. Abe, T. Yasuda, and A. Suzuki: “LargeCapacity Contactless Power Transformer for Electric Vehicle Using MultipleModule Configuration”, IEEJ JIASC2012, No.4-9 (2012)

(42) K. Okada, N. Hoshi, and J. Haruna: “Frequency Characteristic for InductivePower Transfer System”, IEEJ JIASC2012, No.Y-54 (2012)

(43) H. Takanashi, T. Yamanaka, M. Chigira, Y. Kaneko, S. Abe, T. Yasuda, andA. Suzuki: “Compact Contactless Power Transformer for Electric Vehicle3 kW Charger”, IEEJ JIASC2011, No.2-12 (2011)

(44) K. Iimura, N. Hoshi, and J. Haruna: “Loss Evaluation of Moving Type Induc-tive Power Transfer System with LCL Circuit”, IEEJ JIASC2011, No.Y-48(2011)

(45) Y. Moriwaki, T. Imura, and Y. Hori: “A Study on Reduction of ReflectedPower Using DC/DC Converter in Wireless Power Transfer System via Mag-netic Resonant Coupling”, IEEJ JIASC2011, No.2-10 (2011)

(46) K. Wakasugi, T. Isobe, and R. Shimada: “Highly Efficient Non-Contact En-ergy Transfer Systems Using a Magnetic Energy Recovery Switch”, IEEJJIASC2010, No.1-42 (2010)

(47) Y. Tahara and H. Irie: “Cascade Configuration of T-LCL Type and T-CLCType Immittance Converter in Non-Contact energy Transfer System”, IEEJJIASC2007, No.1-84 (2007)

(48) A. Asami and H. Irie: “Comparison of characteristics for connections ofpick-up in non-contact energy transfer system”, IEEJ JIASC2006, No.1-118(2006)

(49) A. Asami and H. Irie: “Series Resonance and Parallel Resonance of ReceiptDevice for Non-Contact Energy Transfer System”, IEEJ JIASC2005, No.Y-100 (2005)

(50) H. Abe: “A Simple Method of Output Voltage Stabilization Suited to the Out-put Rectifier Circuit in the Non-Contact Energy Transfer”, IEEJ JIASC2003,No.1-18 (2003)

(51) Y. Yamane and H. Irie: “Characteristics of Non-Contact Energy Transfer Sys-tem for Changing the Shape of the Core”, IEEJ JIASC2003, No.2-26 (2003)

(52) M. Nishimura and A. Kawamura: “Fundamental Study on Contact-less powertransmission for a high speed railway”, IEEJ JIASC2003, No.Y-43 (2003)

(53) T. Yabuuchi and H. Irie: “High Frequency Constant-Current Power Sup-ply for Non-Contact Energy Transfer System”, IEEJ JIASC2003, No.Y-42(2003)

(54) D. Gunji, T. Imura, and H. Fujimoto: “Study of Power Conversion Cir-cuit Structure Appropriate for Control Purpose on Wireless Power Transfer”,IEEJ SPC, No.SPC-15-17 (2015)

(55) R. Ota, N. Hoshi, and J. Haruna: “Design of Compensation Capacitor in S/PTopology of Inductive Power Transfer System with Buck or Boost Converteron Secondary Side”, IEEJ Journal of Industry Application, Vol.4, No.4,pp.476–485 (2015)

(56) Y. Hayashi, H. Toyoda, and T. Ise: “Contactless DC Connector Concept forHigh-Power-Density 380-V DC Distribution System”, IEEJ Journal of In-dustry Application, Vol.4, No.1, pp.49–58 (2015)

(57) K. Konishi, T. Mishima, and M. Nakaoka: “A Time-Sharing Principle-basedFrequency Doubler ZCS High Frequency-Resonant Inverter for InductivePower Transfer—The First Report on the Experimental Evaluation—”, IE-ICE Technical Report, No.EE2015-8 (2015)

(58) K. Ukita, T. Kashiwagi, Y. Sakamoto, Y. Kato, H. Yoda, and T. Sasakawa:“Verification of Non-contact Power Supply System for Railways Using a TestVehicle”, IEEJ Annual meeting 2015, No.5-128 (2015)

(59) A. Matsushita, N. Tada, and H. Ishihara: “Verification test of 7 kW ClassContactless Power Transfer system”, IEEJ Annual meeting 2015, No.4-156(2014)

(60) H. Toita, T. Takizawa, T. Kobari, J. Sagawa, N. Ariyoshi, T. Kaneko, et al.:“The Development of 50 kW Inductive Power Supply System for the dailyRoot Bus”, IEEJ Annual meeting 2014, No.4-083 (2014)

(61) K. Iimura, N. Hoshi, and J. Haruna: “Constant Voltage Output Control Meth-ods of Parallel-Parallel Compensated Inductive Power Transfer”, IEEJ An-nual meeting 2013, No.4-005 (2013)

(62) K. Okada, K. Iimura, and N. Hoshi: “Comparison of Primary Compensa-

tion Topologies for Inductive Power Transfer System”, IEEJ Annual meeting2012, No.4-103 (2012)

(63) H. Iura, H. Matsumoto, Y. Neba, K. Ishizaka, and R. Itoh: “PFC Topologywith Suppression of Input Harmonics in Contactless Power Transfer System”,IEEJ Annual meeting 2012, No.4-106 (2012)

(64) S. Kawano, M. Okamoto, E. Hiraki, and T. Tanaka: “Experimental verifica-tion of High-Frequnecy-link AC-AC Converter for Non-contact Power Sup-ply System in Parking Tower”, IEEJ Annual meeting 2012, No.4-107 (2012)

(65) S. Abe, K. Kanai, Y. Kaneko, and S. Abe: “Three-phase Moving Pick-Up Type Contactless Power Transfer Systems”, IEEJ Annual meeting 2012,No.4-155 (2010)

(66) N Ehara, T. Iwata, T. Tsuji, Y. Kaneko, S. Abe, and T. Yasuda: “Character-istics of Contactless Power Transfer System Equipped with Aluminum-plateLeakage Flux Shield”, IEEJ Annual meeting 2008, No.4-196 (2008)

(67) T. Yamaji, F. Jin, K. Fujiwara, Y. Ishihara, T. Todaka, K. Sakaguchi, et al.:“Contact-less power transfer system based on the parallel resonance and cur-rent doubler”, IEEJ Annual meeting 2007, No.4-035 (2007)

(68) A. Asami and H. Irie: “Non-Contact Power Transfer With a Pick-Up WitchHas immittance Converter Characteristics”, IEEJ Annual meeting 2006,No.4-221 (2006)

(69) H. Sakamoto, K. Harada, S. Washimiya, K. Takehara, Y. Matsuo, and F.Nakao: “Large Air-Gap Coupler for Inductive Charger”, IEEE Trans. onMagnetics, Vol.35, No.5, pp.3526–3528 (1999)

(70) B.L. Cannon, J.F. Hoburg, D.D. Stancil, and S.C. Goldstein: “Magnetic Res-onant Coupling As a Potential Means for Wireless Power Transfer to MultipleSmall Receivers”, IEEE Trans. on Power Electronics, Vol.24, No.7, pp.1819–1825 (2009)

(71) Z.N. Low, R.A. Chinga, R. Tseng, and J. Lin: “Design and Test of a High-Power High-Efficiency Loosely Coupled Planar Wireless Power TransferSystem”, IEEE Trans. on Industrial Electronics, Vol.56, No.5, pp.1801–1812(2009)

(72) J.W. Hsu, A.P. Hu, and A. Swain: “A Wireless Power Pickup Based on Di-rectional Tuning Control of Magnetic Amplifier”, IEEE Trans. on IndustrialElectronics, Vol.56, No.7, pp.2771–1781 (2009)

(73) S. Lee and R.D. Lorenz: “Development and Validation of Model for 95%-Efficiency 220-W Wireless Power Transfer Over a 30-cm Air Gap”, IEEETran. on Industry Applications, Vol.47, No.6, pp.2495–2504 (2011)

(74) J. Park, Y. Tak, Y. Kim, Y. Kim, and S. Nam: “Investigation of AdaptiveMatching Methods for Near-Field Wireless Power Transfer”, IEEE Trans. onAntennas and Propagation, Vol.59, No.5, pp.1769–1773 (2011)

(75) J. Huh, S.W. lee, W.Y. Lee, G.H. Cho, and C.T. Rim: “Narrow-Width Induc-tive Power Transfer System for Online Electrical Vehicles”, IEEE Trans. onPower Electronics, Vol.26, No.12, pp.3666–3679 (2011)

(76) T. Imura and Y. Hori: “Maximizing Air Gap and Efficiency of Magnetic Res-onant Coupling for Wireless Power Transfer Using equivalent Circuit andNeumann Formula”, IEEE Trans. on Industrial Electronics, Vol.58, No.10,pp.4746–4752 (2011)

(77) J. Wang, J. Li, S.L. Ho, W.Y. Chau, W.K. Lee, W.N. Fu, et al.: “Study andExperimental Verification of a Rectangular Printed-Circuit-Board WirelessTransfer System for Low Power Devices”, IEEE Trans. on Magnetics, Vol.48,No.11, pp.3013–3016 (2012)

(78) H. Zeng, S. Yang, and F. Peng: “Wireless power transfer via harmonic currentfor Electric Vehicles Application”, IEEE Applied Power Electronics Confer-ence and Exposition 13th, pp.592–596 (2015)

(79) F. Lu, H. Hofmann, J. Deng, and C. Mi: “Output Power and Efficiency Sen-sitivity to Circuit Parameter Variations in Double-Sided LCC-CompensatedWireless Power Transfer System”, IEEE Applied Power Electronics Confer-ence and Exposition 13th, pp.597–601 (2015)

(80) B. Wunsch, J. Bradshaw, I. Stevanovic, F. Canales, and W. Van-der-Merwe:“Inductive power transfer for auxiliary power of medium voltage converters”,IEEE Applied Power Electronics Conference and Exposition 13th, pp.2551–2556 (2015)

(81) E. Asa, K. Colak, M. Bojarski, and D. Czarkowski: “A Novel Phase Con-trol of Semi Bridgeless Active Rectifier for Wireless Power Transfer Appli-cations”, IEEE Applied Power Electronics Conference and Exposition 13th,pp.3225–3231 (2015)

(82) K. Hata, T. Imura, and Y. Hori: “Maximum Efficiency Control of WirelessPower Transfer via Magnetic Resonant Coupling Considering Dynamics ofDC-DC Converter for Moving Electric Vehicles”, IEEE Applied Power Elec-tronics Conference and Exposition 13th, pp.3301–3306 (2015)

(83) J. Hou, Q. Chen, S. Wong, X. Ren, and X. Ruan: “Output Current Char-acterization of Parallel-Series/Series Compensated \resonant Converter forContactless Power Transfer”, IEEE Applied Power Electronics Conferenceand Exposition 13th, pp.1625–1629 (2015)

(84) H. Ishihara, F. Moritsuka, A. Matsushita, and S. Otake: “A Voltage Ratio-based Efficiency Control Method for 3 kW Wireless Power Transmission”,



IEEE Applied Power Electronics Conference and Exposition 12th, pp.1312–1316 (2014)

(85) K. Orikawa, Y. Fujita, and J. Itoh: “Investigation for High Output of 2.5 MHzPower Supply Constructed from Multi-Core Transformers and a Multi-PhaseInverter and Application for Wireless Power Transfer”, IEEE Applied PowerElectronics Conference and Exposition 12th, pp.1329–1335 (2014)

(86) C. Zhao, Z. Wang, J. Du, J. Wu, S. Zong, and X. He: “Active ResonanceWireless Power Transfser System Using Phase Shift Control Strategy”, IEEEApplied Power Electronics Conference and Exposition 12th, pp.1336–1341(2014)

(87) N. Liu and B. Wang: “An LLC-Based Planar Wireless Power Transfer Sys-tem for Multiple Devices”, IEEE Applied Power Electronics Conference andExposition 12th, pp.3411–3417 (2014)

(88) R. Bosshard, J.W. Kolar, and B. Wunsch: “Accurate Finite-Element Model-ing and Experimental Verification of Inductive Power Transfer Coil Design”,IEEE Applied Power Electronics Conference and Exposition 12th, pp.1648–1653 (2014)

(89) R. Chen, C. Zheng, Z.U. Zahid, E. Faraci, M. Senesky, D. Anderson, and G.lisi: “Analysis and Parameters Optimization of a Contactless IPT System forEV Charger”, IEEE Applied Power Electronics Conference and Exposition12th, pp.1654–1661 (2014)

(90) J. Huh, W. Lee, G. Cho, B. Lee, and C. Rim: “Characterization of Non-vel Inductive Power Transfer Systems for On-Line Electric Vehicles”, IEEEApplied Power Electronics Conference and Exposition 11th, pp.1975–1979(2013)

(91) A.P. Sample, D.A. Meyer, and J.R. Smith: “Analysis, Experimental Results,and Range Adaption of Magnetically Coupled Resonators for Wireless PowerTransfer”, IEEE Trans. on Industrial Electronics, Vol.58, No.2, pp.544–554(2011)

(92) W. Zhong, C.K. Lee, and S.Y.R. Hui: “General Analysis on the Use of Tesla’sResonators in Domino Forms for Wireless Power Transfer”, IEEE Trans. onIndustrial Electronics, Vol.60, No.1, pp.261–170 (2013)

(93) D. Ahn and S. Hong: “Effect of Coupling Between Multiple Transmitters orMultiple Recievers on Wireless Power Transfer”, IEEE Trans. on IndustrialElectronics, Vol.60, No.7, pp.2602–2613 (2013)

(94) D. Ahn and S. Hong: “A Study on Magnetic Field Repeater in Wireless PowerTransfer”, IEEE Trans. on Industrial Electronics, Vol.60, No.1, pp.360–371(2013)

(95) T.C. Beh, M. Kato, T. Imura, S. Oh, and Y. Hori: “Automated ImpedanceMatching System for Robust Wireless Power Transfer via Magnetic Res-onance Coupling”, IEEE Trans. on Industrial Electronics, Vol.60, No.9,pp.3689–3698 (2013)

(96) M.J. Neath, A.K. Swain, U.K. Madawala, and D.J. Thrimawithana: “An Op-timal PID Controller for a Bidirectional Inductive Power Transfer SystemUsing Multiobjective Genetic Algorithm”, IEEE Trans. on Power Electron-ics, Vol.29, No.3, pp.1523–1531 (2014)

(97) S. Aldhaher, P.C. Luk, A. Bati, and J.F. Whidborne: “Wireless Power Trans-fer Using Class E Inverter With Saturable DC-Feed Inductor”, IEEE Trans.on Industry Applications, Vol.50, No.4, pp.2710–2718 (2014)

(98) K.E. Koh, T.C. Beh, T. Imura, and Y. Hori: “Impedance Matching and PowerDivision Using Impedance Inverter for Wireless Power Transfer via MagneticResonant Coupling”, IEEE Trans. on Industry Applications, Vol.50, No.3,pp.2061–2070 (2014)

(99) Q. Zhu, L. Wang, and C. Liao: “Compensate Capacitor Optimization forKilowatt-Level Magnetically Resonant Wireless Charging System”, IEEETrans. on Industrial Electronics, Vol.61, No.12, pp.6758–6768 (2014)

(100) S.Y. Choi, B.W. Gu, S.W. Lee, W.Y. Lee, J. Huh, and C.T. Rim: “GeneralizedActive EMF Cancel Methods for Wireless Electric Vehicles”, IEEE Trans. onPower Electronics, Vol.29, No.11, pp.5770–5783 (2014)

(101) M. Fu, C. Ma, and X. Zhu: “A Cascaded Boost-Buck Converter for High-Efficiency Wireless Power Transfer Systems”, IEEE Trans. on Industrial In-formatics, Vol.10, No.3, pp.1972–1980 (2014)

(102) W. Li, H. Zhao, S. Li, J. Deng, T. Kan, and C.C. Mi: “Integrated LCC com-pensation topology for Wireless Charger in Electric and Plug-in Electric Ve-hicles”, IEEE Trans. on Industrial Electronics, Vol.62, No.7, pp.4215–4225(2015)

(103) T. Diekhans and R.W.D. Doncker: “A Dual-Side Controlled Inductive PowerTransfer System Optimized for Large Coupling Factor Variations and Par-tial Load”, IEEE Trans. on Power Electronics, Vo(103)(111)l. 30, No.11,pp.6320–6328 (2015)

(104) S. Li, W. Li, J. Deng, T.D. Nguyen, and C.C. Mi: “A Double-Sided LCCCompensation Network and Its Tuning Method for Wireless Power Transfer”,IEEE Trans. on Vehicular Technology, Vol.64, No.6, pp.2261–2273 (2015)

(105) S. Li and C.C. Mi: “Wireless Power Transfer for Electric Vehicle Applica-tions”, IEEE Journal of Emerging and Selected Topics in Power Electronics,Vol.3, No.1, pp.4–17 (2015)

(106) S. Aldhaher, P.C. luk, K.E.K. Drissi, and J.F. Whidborne: “High-Input-Voltage High-Frequnecy Class E Rectifiers for Resonant Inductive Links”,IEEE Trans. on Power Electronics, Vol.30, No.3, pp.1328–1335 (2015)

(107) J. Dai and D.C. Ludois: “A Survey of Wireless Power Transfer and a Criti-cal Comparison of Inductive and Capacitive Coupling for Small Gap Appli-cations”, IEEE Trans. on Power Electronics, Vol.30, No.11, pp.6017–6029(2015)

(108) W.X. Zhong and S.Y.R. Hui: “Maximum Energy Efficiency Tracking forWireless Power Transfer Systems”, IEEE Trans. on Power Electronics,Vol.30, No.7, pp.4025–4034 (2015)

(109) H. Li, J. Li, K. Wang, W. Chen, and X. Yang: “A Maximum Efficiency PointTracking Control Scheme for Wireless Power Transfer Systems Using Mag-netic Resonant Coupling”, Vol.30, No.7, pp.3998–4008 (2015)

(110) Z. Pantic, K. Lee, and S.M. Lukic: “Receivers for Multifrequency Wire-less Power Transfer: Design for Minimum Interference”, IEEE Journal ofEmerging and Selected Topics in Power Electronics, Vol.3, No.1, pp.234–241 (2015)

(111) K. Colak, E. Asa, M. Bojarski, D. Czarkowski, and O.C. Onar: “A NovelPhase-Shift Control of Semibridgeless Active Rectiber for Wireless PowerTransfer”, IEEE Trans. on Power Electronics, Vol.30, No.11, pp.6288–6297(2015)

(112) M. Fu, H. Yin, X. Zhu, and C. Ma: “Analysis and Tracking of Optimal Loadin Wireless Power Transfer Systems”, IEEE Trans. on Power Electronics,Vol.30, No.7, pp.3952–3963 (2015)

(113) J. Lee and B. Han: “A Bidirectional Wireless Power Transfer EV ChargerUsing Self-Resonant PWM”, IEEE Trans. on Power Electronics (Letter),Vol.30, No.4, pp.1784–1791 (2015)

(114) A. Berger, M. Agostinelli, S. Vesti, J.A. Oliver, J.A. Cobos, and M. Huemer:“A Wireless Charging System Applying Phase-Shift and Amplitude Controlto Maximize Efficiency and Extractable Power”, IEEE Trans. on Power Elec-tronics, Vol.30, No.11, pp.6338–6348 (2015)

(115) J.T. Boys, G.A. Covic, and Y. Xu: “DC Analysis Technique for InductivePower Transfer Pick-Ups”, IEEE Trans. on Power Electronics, Vol.1, No.2,pp.51–53 (2003)

(116) C. Wang, G.A. Covic, and O.H. Stielau: “Investigating an LCL Load Res-onant Inverter for Inductive Power Transfer Application”, IEEE Trans. onPower Electronics, Vol.19, No.4, pp.995–1002 (2004)

(117) C. Wang, G.A. Covic, and O.H. Stielau: “Power Transfer Capability andBifurcation Phenomena of Loosely Coupled Inductive Power Transfer Sys-tems”, IEEE Trans. on Industrial Electronics, Vol.51, No.1, pp.148–157(2004)

(118) G.A. Covic, J.T. Boys, M.L.G. Kissin, and H.G. Lu: “A Three-Phase Induc-tive Power Transfer System for Roadway-Powered Vehicles”, IEEE Trans.on Industrial Electronics, Vol.54, No.6, pp.3370–3378 (2007)

(119) N.A. Keeling, G.A. Covic, and J.T. Boys: “A Unity-Power-Factor IPT Pickupfor High-Power Application”, IEEE Trans. on Industrial Electronics, Vol.57,No.2, pp.744–751 (2010)

(120) H.H. Wu, A. Gilchrist, K.D. Sealy, and D. Bronson: “A High Efficiency5 kW Inductive Charger for EVs Using Dual Side Control”, IEEE Trans. onIndustrial Informatics, Vol.8, No.3, pp.585–595 (2012)

(121) U.K. Madawala, M. Neath, and D.J. Thrimawithana: “A Power-FrequencyController for Bidirectional Inductive Power Transfer Systems”, IEEE Trans.on Industrial Electronics, Vol.60, No.1, pp.310–317 (2013)

(122) M. Budhia, J.T. Boys, G.A. Covic, and C. Huang: “Development of a Single-Sided Flux Magnetic Coupler for Electric Vehicle IPT Charging Systems”,IEEE Trans. on Industrial Electronics, Vol.60, No.1, pp.318–328 (2013)

(123) D.J. Thrimawithana, U.K. Madawala, and M. Neath: “A SynchronizationTechnique for Bidirectional IPT Systems”, IEEE Trans. on Industrial Elec-tronics, Vol.60, No.1, pp.301–309 (2013)

(124) D.J. Thrimawithana and U.K. Madawala: “A Generalized Steady-StateModel for Bidirectional IPT Systems”, IEEE Trans. on Power Electronics,Vol.28, No.10, pp.4681–4689 (2013)

(125) N.X. Bac, D.M. Vilathgamuwa, and U.K. Madawala: “A SiC-Based MatrixConverter Topology for Inductive Power Transfser System”, IEEE Trans. onPower Electronics, Vol.29, No.8, pp.4029–4038 (2014)

(126) G.R. Nagendra, G.A. Covic, and J.T. Boys: “Determining the Physical Sizeof Inductive Couplers for IPT EV Systems”, IEEE Journal of Emerging andSelected Topics in Power Electronics, Vol.2, No.3, pp.571–583 (2014)

(127) R. Haldi and K. Schenk: “A 3.5 kW Wireless Charger for Electric Vehi-cles with Ultra High Efficiency”, IEEE Energy Conversion Congress & Expo2014, pp.668–674 (2014)

(128) H. Sekiya, T. Suetsugu, and K. Shirota: “Loosely Coupled Inductive WirelessPower Transfer Systems with Class-E Transmitter and Multiple Receivers”,IEEE Energy Conversion Congress & Expo 2014, pp.675–680 (2014)

(129) P.C.K. Luk and S. Aldhaher: “Analysis and Design of a Class D Rectifier fora Class E Driven Wireless Power Transfer System”, IEEE Energy Conversion



Congress & Expo 2014, pp.851–857 (2014)(130) M. Jo, Y. Sato, Y. Kaneko, and S. Abe: “Methods for Reducing Leakage

Electric Field of a Wireless Power Transfer System for Electric Vehicles”,IEEE Energy Conversion Congress & Expo 2014, pp.1762–1769 (2014)

(131) H. Takanashi, Y. Sato, Y. Kaneko, S. Abe, and T. Yasuda: “A Large Air Gap3 kW Wireless Power Transfer System for Electric Vehicles”, IEEE EnergyConversion Congress & Expo 2012, pp.269–274 (2012)

(132) H.H. Wu, A. Gilchrist, K. Sealy, and D. Bronson: “A 90 Percent Efficient5 kW Inductive Charger for Evs”, IEEE Energy Conversion Congress & Expo2012, pp.275–282 (2012)

(133) A. Zaheer, D. Kacprzak, and G.A. Covic: “A Bipolar Receiver Pad in aLumped IPT System for Electric Vehicle Charging Applications”, IEEE En-ergy Conversion Congress & Expo 2012, pp.283–290 (2012)

(134) F. Musavi, M. Edington, and W. Eberle: “Wireless Power Transfer: A Surveyof EV Battery Charging Technologies”, IEEE Energy Conversion Congress& Expo 2012, pp.1804–1810 (2012)

(135) I. Nam, R. Dougal, and En Santi: “Novel Control Approach to AchievingEfficient Wireless Battery Charging for Portable Electronic Devices”, IEEEEnergy Conversion Congress & Expo 2012, pp.2482–2891 (2012)

(136) E. Waffenschmidt: “Free positioning for inductive wireless power system”,IEEE Energy Conversion Congress & Expo 2011, pp.3480–3487 (2011)

(137) J.O. Mur-Miranda, G. Fanti, Y. Feng, K. Omanakuttan, R. Ongie, A.Setjoadi, and W. Franklin: “Wireless Power Transfer Using Weakly Cou-pled Magnetostatic Resonators”, IEEE Energy Conversion Congress & Expo2010, pp.4179–4186 (2011)

(138) J. Huh, S. Lee, C. Park, G. Cho, and C. Rim: “High Performance InductivePower Transfer System with Narrow Rail Width for On-Line Electric Vehi-cles”, IEEE Energy Conversion Congress & Expo 2010, pp.647–651 (2010)

(139) S. Lee, J. Huh, C. Park, N. Choi, G. Cho, and C. Rim: “On-Line ElectricVehicle using Inductive Power Transfer System”, IEEE Energy ConversionCongress & Expo 2010, pp.1598–1601 (2010)

(140) G.A. Covic, J.T. Boys, A.M.W. Tam, and J.C.H. Peng: “Self Tuning Pick-upsfor Inductive Power Transfer”, IEEE 39th Annual Power Electronics Special-ist Conference, pp.3489–3494 (2008)

(141) J.T. Boys, C.Y. Huang, and G.A. Covic: “Single-Phase Unity Power-FactorInductive Power Transfer System”, IEEE 39th Annual Power ElectronicsSpecialist Conference, pp.3701–3706 (2008)

(142) S. Raabe, J.T. Boys, and G.A. Covic: “A High Power Coaxial InductivePower Transfer Pickup”, IEEE 39th Annual Power Electronics SpecialistConference, pp.4320–4325 (2008)

(143) S. Kitazawa, K. Kondo, and T. Kashiwagi: “Study on a Control Method ofthe Power Converter for Constant Power Transmission by Single-pulse PWMmode”, 15th European Conference on Power Electronics and Applications,pp.1–9 (2013)

(144) H. Omori, Y. Iga, T. Morizane, N. Kimura, K. Nakagawa, and M. Nakaoka:“A Novel Wireless EV Charger using SiC Single-Ended Quasi-Resonant In-verter for Home Use”, 15th International Power Electronics and Motion Con-trol Conference, No.LS8b.2, pp.1–9 (2012)

(145) H. Hao, G.A. Covic, and J.T. Boys: “An Approximate Dynamic Model ofLCL-T-Based Inductive Power Transfer power Supplies”, IEEE Trans. onPower Electronics, Vol.29, No.10, pp.5554–5567 (2014)

(146) H. Hao, G.A. Covic, and J.T. Boys: “A Parallel Topology for Inductive PowerTransfer Power Supplies”, IEEE Trans. on Power Electronics, Vol.29, No.3,pp.1140–1151 (2014)

(147) A. Zaheer, G.A. Covic, and D. Kacprzak: “A Bipolar Pad in a 10-kHz 300-W Distributed IPT System for AGV Applications”, IEEE Trans. on IndustrialElectronics, Vol.61, No.7, pp.3288–3301 (2014)

(148) W. Zhang, S. Wong, C.K. Tse, and Q. Chen: “Design for Efficiency Opti-mization and Voltage Controllability of Series-Series Compensated InductivePower Trasnfer Systems”, IEEE Trans. on Power Electronics, Vol.29, No.1,pp.191–200 (2014)

(149) J.E. James, D.J. Robertson, and G.A. Covic: “Improved AC Pickups for IPTSystems”, IEEE Trans. on Power Electronics, Vol.29, No.12, pp.6361–6374(2014)

(150) Z. Pantic and K. Lee: “Multifrequency Inductive Power Transfer”, IEEETrans. on Power Electronics, Vol.29, No.11, pp.5995–6005 (2014)

(151) Z. Cheng, Y. Lei, K. Song, and C. Zhu: “Design and Loss Analysisof Loosely Coupled Transformer for an Underwater High-Power InductivePower Transfer System”, IEEE Trans. on Magnetics, Vol.51, No.7, pp.1–10(2015)

(152) J.T. Boys and G.A. Covic: “The Inductive Power Transfer Story at the Uni-versity of Auckland”, IEEE Circuits and Systems Magazine, pp.6–27 (2015)

(153) X. Qu, H. Han, S. Wong, C.K. Tse, and W. Chen: “Hybrid IPT TopologiesWith Constant Current or Constant Voltage Output for Battery Charging Ap-plications”, IEEE Trans. on Power Electronics, Vol.30, No.11, pp.6329–6337(2015)

(154) S.Y. Choi, S.Y. Jeong, B.W. Gu, G.C. Lim, and C.T. Rim: “Ultraslim S-TypePower Supply Rails for Roadway-Powered Electric Vehicles”, IEEE Trans.on Power Electronics, Vol.30, No.11, pp.6456–6468 (2015)

(155) Y.H. Sohn, B.H. Choi, E.S. Lee, G.C. Lim, G. Cho, and C.T. Rim: “Gen-eral Unified Analyses of Two-Capacitor Inductive Power Transfer Systems:Equivalence of Current-Source SS and SP Compensations”, IEEE Trans. onPower Electronics, Vol.30, No.11, pp.6030–6045 (2015)

(156) C. Zheng, H. Matsumoto, J. Lai, and L. Zhang: “Design Considera-tions to Reduce Gap Variation and Misalignment Effects for the InductivePower Transfer System”, IEEE Trans. on Power Electronics, Vol.30, No.11,pp.6108–6119 (2015)

(157) B.X. Nguyen, D. Mahinda, G.H.B. Foo, P. Wang, A. Ong, U.K. Madawala,and T. Duy Nguyen: “An Efficiency Optimization Scheme for BidirectionalInductive Power Transfer Systems”, IEEE Trans. on Power Electornics,Vol.30, No.11, pp.6310–6319 (2015)

(158) L.J. Chen, J.T. Boys, and G.A. Covic: “Power Management for Multiple-Pickup IPT Systems in Materials Handling Applications”, IEEE Journal ofEmerging and Selected Topics in Power Electronics, Vol.3, No.1, pp.163–176(2015)

(159) S. Weearsinghe, D.J. Thrimawithana, and U.K. Madawala: “Modeling Bidi-rectional Contactless Grid Interfaces With a Soft DC-Link”, IEEE Trans. onPower Electronics, Vol.30, No.7, pp.3528–3541 (2015)

(160) Z.U. Zahid, Z.M. Dalala, C. Zheng, R. Chen, W.E. Faraci, J. Lai, and G.lisi: “Modeling and Control of Series-Series Compensated Inductive PowerTransfer System”, IEEE Journal of Emerging and Selected Topics in PowerElectronics, Vol.30, No.1, pp.111–123 (2015)

(161) R. Bosshard, J.W. Kolar, J. Muhlethaler, I. Stevanovic, B. Wunsch, and F.Canales: “Modeling and eta-alpha-Pareto Optimization of Inductive PowerTransfer Coils for Electric Vehicles”, IEEE Journal of Emerging and SelectedTopics in Power Electronics, Vol.3, No.1, pp.50–64 (2015)

(162) H. Miura, S. Arai, F. Sato, H. Matsuki, and T. Sato: “A Synchronous Rec-tification Using a Digital PLL Technique for Contactless Power Supplies”,IEEE Trans. on Magnetics, Vol.41, No.10, pp.3997–3999 (2015)

(163) Y. Hayashi, H. Toyoda, T. Ise, and A. Matsumoto: “Contactless DC Connec-tor Based on GaN LLC Converter for Next-Generation Data Centers”, IEEETrans. on Industry Applications, Vol.51, No.4, pp.3244–3253 (2015)

(164) J. Hirai, T. Kim, and A. Kawamura: “Practical Study on Wireless Transmis-sion of Power and Information for Autonomous Decentralized ManufacturingSystem”, IEEE Trans. on Industrial Electronics, Vol.46, No.2, pp.349–359(1999)

(165) M. Pinuela, D.C. Yates, S. Lucyszyn, and P.D. Mitcheson: “MaximizingDC-to-Load Efficiency for Inductive Power Transfer”, IEEE Trans. on PowerElectronics, Vol.28, No.5, pp.2437–2447 (2013)

(166) A. Shimamoto, H. Sakamoto, and K. Harada: “Soft switching in ContactlessPower Supply Equipments”, Technical Report of IEICE, No.PE96-9, pp.61–68 (1996)

(167) H. Abe, H. Sakamoto, and K. Harada: “Constant-current Charge of the Non-contact Load Dispatching”, Technical Report of IEICE, No.EE99-41, pp.37–44 (1999)

(168) B. Schumuelling, S.G. Cimen, T. Vosshagen, and F. Turki: “Layout and Op-eration of a Non-Contact Charging System for Electric Vehicles”, 15th In-ternational Power Electronics and Motion Control Conference, No.LS4d.4,pp.1–7 (2012)

(169) T. Imura, H. Okabe, and Y. Hori: “Basic Experimental Study on HelicalAntennas of Wireless Power Transfer for Electric Vehicles by using Mag-netic Resonant Coupling”, Vehicle Power and Propulsion Conference 2009(VPPC), pp.936–940 (2009)

(170) A. Kurs, A. Karalis, R. Moffatt, J.D. Joannopoulos, P. Fisher, and M.Soljacic: “Wireless Power Transfer via Strongly Coupled Magnetic Reso-nances”, Science, Vol.317, pp.83–86 (2007)

(171) N.Y. Kim, K.Y. Kim, Y. Ryu, J. Choi, D. Kim, C. Yoon, et al.: “Auto-mated Adaptive Frequency Tracking System for Efficient Mid-range Wire-less Power Transfer via Magnetic Resonance Coupling”, 43nd European Mi-crowave Conference 2012, pp.221–224 (2012)

(172) M. Eghtesadi: “Inductive power transfer to an electric vehicle-analyticalmodel”, 40th IEEE Conference in Vehicular Technology, pp.100–104 (1990)

(173) H. Sakamoto and K. Harada: “A Novel Converter for Non-Contact Chargingwith Electromagnetic Coupling”, IEEE Trans. on Magnetics, Vol.29, No.6,pp.3228–3231 (1993)

(174) H. Sakamoto and K. Harada: “A Novel High Power Converter for Non-contact Charging with Magnetic Coupling”, IEEE Trans. on Magnetics,Vol.30, No.6, pp.4755–4757 (1994)

(175) A.W. Green and J.T. Boys: “10 kHz inductively coupled power transfer-concept and control”, International Conference on Power Electronics andVariable-Speed Drives, pp.694–699 (1994)

(176) H. Sakamoto, K. Harada, and K. Yamasaki: “A Novel High Power Converter



for Non-contact Charging with Magnetic Coupling”, International Confer-ence on Power Electronics and Variable-Speed Drives, pp.461–464 (1995)

(177) G.A.J. Elliott, J.T. Boys, and A.W. Green: “Magnetically coupled systemsfor power transfer to electric vehicles”, International Conference on PowerElectronics and Variable-Speed Drives, Vol.2, pp.797–801 (1995)

(178) J.G. Bolger, F.A. Kirsten, and L.S. Ng: “Inductive Power Coupling for anElectric Highway System”, IEEE 28th Conference in Vehicular TechnologyConference, Vol.28, pp.137–144 (1978)

(179) J.G. Bolger, L.S. Ng, D.B. Turner, and R.I. Wallace: “Testing a Prototype In-ductive Power Coupling For an Electric Highway System”, IEEE 29th Con-ference in Vehicular Technology Conference, Vol.29, pp.48–56 (1979)

(180) A.P. Hu and H.L. Li: “A new high frequency current generation method forinductive power transfer applications”, 37th IEEE Power Electronics Special-ists Conference 2006, pp.18–22 (2006)

(181) Y. Su, C. Tang, S. Wu, and U. Sun: “Research of LCL Resonant Inverter inWireless Power Transfer System”, International Conference on Power Sys-tem Technology 2006, pp.1–6 (2006)

(182) U.K. Madawala and D.J. Thrimawithana: “Current sourced bi-directional in-ductive power transfer system”, Power Electronics IET, Vol.4, No.4, pp.471–480 (2013)

(183) S. Ahn, H.H. Park, C. Choi, J. Kim, E. Song, H.B. Park, et al.: “Reductionof Electromagnetic Field (EMF) of Wireless Power Transfer System usingQuadruple Coil for Laptop Applications”, IEEE MTT-S International Mi-crowave Workshop Series on Innovative Wireless Power Transmission: Tech-nologies, Systems, and Applications, No.THU-C-4, pp.65–68 (2012)

(184) J. Kim, J. Kim, S. Kong, H. Kim, I. Suh, N.P. Suh, et al.: “Coil Design andShielding Methods for a Magnetic Resonant Wireless Power Transfer Sys-tem”, Proceedings of the IEEE, Vol.101, No.6, pp.1332–1342 (2013)

(185) I. Mayordomo, T. Drager, P. Spies, J. Bernhard, and A. Pflaum: “AnOverview of Technical Challenges and Advances of Inductive WirelessPower Transmission”, Proceedings of the IEEE, Vol.101, No.6, pp.1302–1311 (2013)

(186) F. Musavi and W. Eberle: “Overview of wireless power transfer technologiesfor electric vehicle battery charging”, Power Electronics IET, Vol.7, No.1,pp.60–66 (2014)

(187) J.M. Miller and A. Daga: “Elements of Wireless Power Transfer Essential toHigh Power Charging of Heavy Duty Vehicles”, IEEE Trans. on Transporta-tion Electrification, Vol.1, No.1, pp.26–39 (2015)

(188) A. Esser and H. Skudelny: “A New Approach to Power Supplies for Robots”,IEEE Trans. on Industry Applications, Vol.27, No.5, pp.872–876 (1991)

(189) H. Sakamoto and K. Harada: “A Novel Circuit For Non-contact ChargingThrough Electro-magnetic Coupling”, 23rd IEEE Power Electronics Special-ists Conference, pp.168–174 (1992)

(190) K.W. Klontz, D.M. Divan, D.W. Novotny, and R.D. Lorenz: “ContactlessPower Delivery System for Mining Applications”, IEEE Trans. on IndustryApplications, Vol.31, No.1, pp.27–35 (1995)

(191) A. Esser: “Contactless charging and communication for electric vehicles”,IEEE Industry Applications Magazine, Vol.1, No.6, pp.4–11 (1995)

(192) A. Kawamura, K. Ishioka, and J. Hirai: “Wireless Transmission of Powerand Information Through One High-Frequency Resonannt AC Link Inverterfor Robot Manipulator Applications”, IEEE Trans. on Industry Applications,Vol.32, No.3, pp.503–508 (1996)

(193) J.M. Barnard, J.A. Ferreira, and J.D. Wyk: “Sliding Transformers for LinearContactless Power Delivery”, IEEE Trans. on Industrial Electronics, Vol.44,No.6, pp.774–779 (1997)

(194) D.A.G. Pedder, A.D. Brown, and J.A. Skinner: “A Contactless Electrical En-ergy Transmission System”, IEEE Trans. on Industrial Electronics, Vol.46,No.1, pp.23–30 (1999)

(195) S. Adachi, F. Sato, S. Kikuchi, and H. Matsuki: “Consideraiton of Contact-less Power Station with Selective Excitation to Moving Robot”, IEEE Trans.on Magnetics, Vol.35, No.5, pp.3583–3585 (1999)

(196) F. Lu, H. Zhang, H. Hofmann, and C. Mi: “A High Efficiency 3.3 kW

Loosely-Coupled Wireless Power Transfer System Without Magnetic Mate-rial”, IEEE Energy Conversion Congress & Expo 2015, pp.2282–2287 (2015)

(197) C.E. Zell and J.G. Bolger: “Development of an engineering prototype of aroadway powered electric transit vehicle system: A public/private sector pro-gram”, 32nd IEEE Vehicular Technology Conference 1982, Vol.32, pp.435–438 (1982)

(198) Ministry of Internal Affairs and Communications, Japan, “Inquiry of tech-nical requirements for wireless power transfer system for EVs in techni-cal requirements for wireless power transfer system in standards of Interna-tional Special Committee on Radio Interference (CISPR)”, No.3 (2015) (inJapanese)

(199) M. Sato, G. Giuseppe, T. Imura, and H. Fujimoto: “Study on High Effi-ciency and High Response of Regeneration for Wireless In-wheel Motor”,IEEJ Trans. IA, Vol.137, No.1, pp.36–43 (2016)

(200) D. Gunji, T. Imura, and H. Fujimoto: “Novel Transmitting Power Con-trol Method without Signal Communication for Wireless Power Transfer viaMagnetic Resonance Coupling”, IEEJ Trans. IA, Vol.136, No.3, pp.222–231(2016)

Keisuke Kusaka (Member) was born in Miyagi, Japan, in 1989. Hereceived the B.S. and M.S. degrees in electrical, elec-tronics and information from Nagaoka University ofTechnology, Niigata, Japan in 2011, 2013, respec-tively. From 2015 to 2016, he was with Swiss FederalInstitute of Technology in Lausanne (EPFL), Switzer-land as a trainee. In 2016, he received the Ph.D.degree in energy and environment science from Na-gaoka University of Technology. Since 2016, he hasbeen with Nagaoka University of Technology, Ni-

igata, Japan as a researcher. His current research interests include the areasof IPT systems and high-frequency converters. He is a member of Instituteof Electrical Engineers of Japan, Society of Automotive Engineers of Japanand IEEE.

Jun-ichi Itoh (Senior Member) was born in Tokyo, Japan, in 1972.He received M.S. and Ph.D. degrees in electrical andelectronic systems engineering from Nagaoka Uni-versity of Technology, Nagaoka, Japan in 1996, 2000,respectively. From 1996 to 2004, he was with FujiElectric Corporate Research and Development Ltd.,Tokyo, Japan. He was with Nagaoka University ofTechnology, Niigata, Japan as an associate professor.Since 2017, he has been a professor. His research in-terests are matrix converters, dc/dc converters, power

factor correction techniques, energy storage system and adjustable speeddrive systems. He received IEEJ Academic Promotion Award (IEEJ Techni-cal Development Award) in 2007. In addition, he also received Isao Taka-hashi Power Electronics Award in IPEC-Sapporo 2010 from IEEJ, 58thOHM Technology Award from The Foundation for Electrical Science andEngineering, November, 2011, Intelligent Cosmos Award from IntelligentCosmos Foundation for the Promotion of Science, May, 2012, and Thirdprize award from Energy Conversion Congress and Exposition-Asia, June,2013. Prizes for Science and Technology (Development Category) from theCommendation for Science and Technology by the Minister of Education,Culture, Sports, Science and Technology, April 2017. He is a senior mem-ber of the Institute of Electrical Engineers of Japan, Society of AutomotiveEngineers of Japan and IEEE.


Documents

Development Trends of Inductive Power Transfer Systems