An Overview of Electrical Vehicle and Hybrid Electrical Vehicle Drives

An Overview of Electrical Vehicle andHybrid Electrical Vehicle DrivesAnton RassõlkinTallinn University of Technology (Estonia)Anton.Rassolkin@ttu.eeAbstract— An overview of electrical vehicles and hybridelectrical vehicles is presented. Main features of traction systemare presented with their benefits and drawbacks. The tractionsystem architectures, propulsion systems and used powerelectronic converters areas are covered. The main areas offuture researches are squared.I. INTRODUCTIONWorld population reached seven billion people in 2011 andthe number of vehicles in operation surpassed the 1 billionunits already in 2010. According to OICA (InternationalOrganization of Motor Vehicle Manufacturers) statistic about80 million vehicles were produced in 2011 and the number isincreasing each year. With further urbanization,industrialization and globalization, the trend of rapid increasein the number vehicles worldwide is inevitable. The mainissues due to increasing of vehicle number are limited volumeof oil and the emissions from burning oil products. The worldconsumes approximately 85 million barrels of oil every daybut there are only 1300 billion barrels of proven reserves ofoil. At the current rate of consumption, the world will run outof oil in 42 years [1]. The emissions from burning fossil fuelsincrease the carbon dioxide (CO 2 ) in the Earth’satmosphere [1]. Increasing of CO 2 is a cause of greenhouseeffect and climate change. As result in long-termconsequences it will lead to rising sea levels and instability ofecosystems. Cutting fossil fuel usage and reducing carbonemissions are the main goals of humanity. Using of HybridElectrical Vehicles (HEV) instead of Internal CombustingEngine Vehicle (ICEV) could notably decrease theatmosphere pollution. Effect of using of Electrical Vehicle(EV) could be even better.Well-to-wheel studies show that, even if the electricity isgenerated from petroleum, the equivalent kilometres that canbe driven by 1 litre of petrol is 46 km in an electric car,compared to 14 km in an ICEV [1]. Moreover, a size ofpetrol-to-electrical transmission is more compact, while witha pure mechanical transmission from engine to wheels a largenumber of gears are required and with a generator-motortraction system wide range of operating speeds are available.Sure, the producing of electricity is complicating process andnot always friendly to environment and often connected withburning of fossil fuels as well. In the same way, currentlyused electrical grids have a list of disadvantages. But on theother hand, today is available quite big range of renewableenergy sources and energy storage systems that are combinedinto the smart electrical grids. EV’s have many advantagesand challenges. Nowadays, EV is widely used as publicelectrical transport. It’s difficult to imagine the modernmegalopolis without underground railways or land electricaltransport like tramway car or trolley bus. In that case researchin the field of HEVs and EVs seems to be very interesting andnecessary.II. HEV AND EV TOPOLOGIESThere are many different ways to combine internalcombusting engine (ICE) with an electrical machine. Theelectrical machine is designed to handle transient powervariations and helps the engine to operate more constantly sothat higher efficiency and lower tailpipe emissions can beachieved [6]. The variety of electrical machine / combustionengine designs can be differentiated by how the electric andcombustion portions of the power train connect, at what timeseach portion is operation and what percent of the power isprovided by each hybrid component [7].Nowadays used topologies are presented in this paper.Available nowadays energy storage systems that could beused in HEV and EV were presented in previous studies [3]and needed to be taken into account during the vehicletopologies analyse.A. Assist HEVThe electric motor is essentially a very large motor whichoperates not only when the engine needs to be turned over,but also when the driver presses the throttle pedal andrequires extra power [7]. Because of the small range of theelectric drive assist hybrid could not operate in pure electricalmode, but it can be used as assist motor in wide range ofcontrolled torques and speeds. As well the part of kineticenergy could be converted into electrical energy duringregenerative braking while vehicle decelerates. The size ofelectrical battery used in assist hybrids is reduced that reducethe total weight of the vehicle.B. Mild HEVThe mild hybrid has a small electric motor that mostly usedas starter and generator sometimes it does operate as tractionmotor as well. Usually, the power rating of the electric motormay be in the range of about 10% of the engine powerrating [8]. Mild hybrid could operate as pure electrical vehicle(the combustion engine is switched off in that mode) only insmall speed range, up to 10 km/h. The design of the tractionpart of mild hybrid is similar to combustion engine vehicletraction system, because booths are very close.C. Full HEVFull hybrids are type of the vehicles that can use pureelectrical traction mode, that notably reduce CO 2 emission.The hybrid-drive concept appears in many forms dependingon the mix of energy sources and propulsion systems used onthe vehicle [9]. The traction energy could be taken from two76

separate energy sources there are several combination ofthese available.D. Parallel HEVParallel HEV is only hybrid vehicle that can switchbetween two types of drives and could be used separately orsimultaneously, depends on traction mode. The electric drivealso can be used as a generator to recharge the batteries whenthe engine produces more power than is needed to propel thevehicle [10]. Combustion engine and electric drive arecoupled mechanically by special gear construction and couldbe unplugged by reswitching of a clutch. Parallel hybrid usemostly electrical drive in urban areas, because of urbandriving particular qualities, fast acceleration/deceleration andshort-time duty cycles. In highway traction mode, when thevehicle runs with a high constant speed and ICE is used.Combustion engine shows its better performance only in asmall working range with high speed and torque that meansthe speed variation is unwished. Parallel hybrid couldrecharge its batteries not only during regenerative braking,but also during ICE traction mode. However, ICE is used noton its better performance mode and that is one of parallelhybrid drawbacks. Double traction system increases the priceof the vehicle as well.E. Series HEVSeries HEV use only electrical drive for traction. ICE isdecoupled from mechanical transmission and used to producekinetic energy for the generator that converts it into electrical.That means traction system requires double energyconversion: mechanical-electrical-mechanical. A weakness ofa series hybrid system is that series hybrids require separatemotor and generator portions which can be combined in someparallel hybrid engines; the combined efficiency of the motorand generator will be lower than that of a conventionaltransmission thereby offsetting the efficiency gains that mightotherwise be realized [7]. Because of the high controllabilityperformance of electrical motor that topology reduces the sizeof gearbox and mechanical transmission. That’s why serieshybrid widely used in heavy industrial vehicles likeexcavators and diesel-electrical locomotives also for urbanvehicles that required often stop duties like buses and deliverycars.F. In-Wheel Motor HEVSome variation of series hybrids have separate smallelectric in-wheel motors (sometimes called hub motors)installed independently at each wheel. That allows separatelycontrol of the power delivery to each wheel, and thereforesimplifies traction control of the vehicle [7]. Such systemallows regulating the acceleration/deceleration torque valuesindependently for each wheel. Тhe mechanical part could bereduced even more than in series hybrids. It means additionalbatteries can be installed on the free space that has beenoccupied by the transmission, which helps to increase thedriving range per charge [20]. Most conventional electricalmachines (such as ac excited or brushed dc motors) are notsuitable for application in in-wheel motor drive because oftheir poor torque density and overload capability [11]. Forthat reason in-wheel hybrids required special designed motorslike axial-flux ironless permanent magnet motors orsynchronous permanent magnet outer rotor motors.G. Series–Parallel HEVSeries–parallel HEV has two couplings mechanical andelectrical. That allows overcoming of the drawbacks of boothtechnologies and using their benefits with best performance.The main aim of such system is the reduction of the fuelconsumption [12]. As well, drivability can be optimizedbased on the vehicle’s operating condition [2]. The maindrawback of series-parallel hybrid is increased vehicle pricein compare with other hybrids.H. Plug-In Hybrid Electric Vehicles (PHEV)The only difference of plug-in hybrid from the hybridvehicle is presence of the cable that allows connecting vehicleto electrical grid. Depends from the energy flow directionplug-in systems divides could be divided on two parts:vehicle-to-grid (V2G), if the energy flow goes to the gridfrom the vehicle; grid-to-vehicle (G2V) if the batteries arecharged from the grid. G2V allows recharging the batterieswithout using ICE that makes daily used light PHEV moreenvironmentally friendly. The basic concept of V2G power isused in electric drive vehicles to provide electric power to thegrid while the vehicle is parked [13]. It means that thebatteries on parked and plugged-in vehicle could be rechargedduring the lean hours and discharged during the peak hours ifit’s necessary. To allow such bi-directional energy flow (G2Vand V2G) the charging systems should be specificallydesigned and optimized. In that case the vehicle is used as asmart consumer, so-called prosumer (combined producer andconsumer) and can be used as a part of smart electrical grid.Connected to the smart grid PHEV could bring new featuresinto the grid like STATCOM, active filter or even portablepower plant [2].I. Fuel Cell Electric Vehicle (FCEV)A fuel cell (FC) is a galvanic cell in which the chemicalenergy of a fuel is converted directly into electrical energy bymeans of electrochemical processes [14]. There are sometanks required to store the fuel, usually hydrogen. It makesthe FCEV more similar to series hybrid but with a less energyconversion stages. The main benefits of FC are – zeroemission, as the sole product of reaction is water; highelectric efficiency of single device up to 60 %; very simpleconstruction. The mainly drawback of a fuel cell for today isits high price and limited technologies [3]. Vehicles poweredsolely by fuel cells have some other drawbacks, such as aheavy and bulky power unit caused by the low power densityof the fuel cell system, long start-up time, and slow powerresponse [14]. To overcome this drawbacks some hybridsolution are presented, where the FCEV are combined withsome other vehicle technologies [15]-[17].J. All Electrical Vehicles (EV)EV use chemical battery as a primary energy storage andonly electric motor for traction. It means that they have zerotailpipe emission and more friendly to environment than othervehicles.The EV has many advantages over the conventional ICEV,such as zero emissions, high efficiency, independence from77

fossil fuels, and quiet and smooth operation [8]. Usually EVsimplified mechanical motor to wheel transmission that issimilar to series hybrid and in-wheel series hybrid vehicles.The design and parameters of the traction system of EVdepends mostly on speed-torque and speed-powercharacteristics.All of the major automotive manufacturers have productionEVs, many of which are available for sale or lease to thegeneral public [5]. While EV is novel technology a lot ofchallenges on its development and research areas exist. Newstandards and requirements should be prepared. Moreover,public recharging infrastructure is required and usednowadays, electrical grids need to be renewed or rebuilt towithstand the increasing load. Due to European Unionderictives the governments support the idea of HEV and EVwith taxes braking and other benefits for HEV/EV owners.Though, it seems that the main problem is the driver habits onvehicle use and refuelling.III. ELECTRIC MOTORS FOR HEV AND EV PROPULSIONElectric motor has relative benefits and drawbacks incompare with traditional ICE. Sure electrical motor is moreefficient and has a zero emission. A major advantage ofelectric motor is that torque generation is very quick andaccurate [4]. That makes EV and HEV more controllable andmanoeuvrable in urban areas. The main drawbacks areelectrical energy sources that are usually short-term storages.There are several types of direct current (DC) andalternating current (AC) electric motors that can be used astraction motors in HEVs and EVs drives.A. DC MotorsThe DC motors were used in last century in electricaltransportation due to their developed status and suppleness ofspeed control. Speed-torque diagram of the series excite DCmotor is very close to load speed-torque diagram of thevehicle that’s why it was widely used in public transport area:tramway cars, trolleybuses, electric trains and diesel-electricallocomotives. A number of prototype EVs in the 1980s andprior were built based on DC series motors as well. However,the size and maintenance requirements of DC motors aremaking their use obsolete, not just in the automotive industry,but in all motor drive applications [5].The main drawbacks of DC motor is a collector brushedthat are required to change the direction of the current insidethe rotating part of the motor (armature). A result of highfriction between brush-contacts and collector: high frictionlosses, increasing of the temperature of the machine, lowreliability, decreasing of the lifecycle and low efficiency.B. Permanent Magnet Motors (PM Motor)PM DC motor is a brushed DC motor with an independentexcited magnet. Because of the limited technologies of PMtheir power range is small and the speed-torque diagram isclose to parallel excited DC motor. All these drawbacks makePM DC motor not suitable for high power tractionapplications.PM AC motor also known as brushless direct current motor(BLDC), is a three phase windings and permanent magnetexcite rotor. For EV and HEV applications, motor size isrelatively large compared to the other smaller powerapplications of PM motors, which amplifies the costproblem [5]. However, the PM AC motors could be used inassist and mild hybrids. The benefit of this motor is thatcurrents do not need to be induced in the rotor (like ininduction motor), making them somewhat more efficient andgiving slightly greater specific power in the same time thedrawback is that it is costlier due to the presence of PM [7].C. Switched Reluctance Motors (SRM)SRM is also known as doubly salient machine, has a simpleconstruction and excellent fault tolerance characteristics. Thestator and the rotor of the SRM are made of irons which aremagnetized by the current through the stator winding. Thesemotors have no windings, magnets, or cages on the rotor,which helps to increase the torque and inertia rating. Themotor speed-torque characteristics are an excellent matchwith the road load characteristics, and performance ofswitched reluctance motors for EV/HEV applications havebeen found to be excellent [5].The main drawback of SRM is that the timing of theturning on and off of the stator currents must be much morecarefully controlled [7], the more complex control device isrequired. The main challenges of switched reluctance motorsare acoustic noise and torque ripple.D. Induction MotorsQuite mature technology of AC induction motor got a harddevelopment push in last 30 years together with powerelectronics progress. Field-oriented control (FOC) ofinduction motor can decouple its torque control from filedcontrol. This allows the motor to behave in the same manneras a separately excited DC motor [18].Because of low stability and overheating on low speed,induction motors mostly found an application in high speedvehicles, otherwise some additional mechanical transmissionrequired for speed reduction. Moreover, the efficiency of theinduction motor in no-load or light-load operation modes isvery small ca 20..30%, but it increases gradually with therated load and reaches ca 75..92% [19]. The main benefits ofinduction motor are high reliability and low manufacturingcost.E. Synchronous Permanent Magnet Outer Rotor (In-Wheel)MotorsUsually as in-wheel motor the permanent magnetsynchronous machine (PMSM) is used, it has high torquedensity, excellent efficiency and overload capability [21].However, there may be risks of demagnetization andmechanical damage of the rotor’s magnets in extreme drivingconditions [22]. The assembly configuration of in-wheelmotor system consists usually not only of the motor itself, butalso from reduction gear, mechanical brake and wheel.IV. POWER ELECTRONICS USED IN HEV AND EVPower electronics are required to provide the electricalenergy conversion between electrical parts of the HEV andEV drive. The inverters required to provide connectionbetween AC traction motors and the batteries. Rectifiers areused in case of applying AC generators as a kinetic-toelectricalenergy converter. DC/DC converters equal the DClink voltage from all energy sources, if more than one is used.78

Special attention should be pointed on the charging systems,while they have a specific requirements and standards.A. InvertersWhile the most of energy storage devices are voltagesources, the voltage source inverter (VSI) got the mostcommon in HEV and EV applications, but it presentsdifficulty hurdles for the automakers to address the importantissues on system cost, weight, volume, and reliability [23].VSI is used to control the speed of induction motors and PMAC motors. The switches are usually IGBTs for high voltage,high-power hybrid configurations or MOSFETs for lowvoltage designs [2]. Voltage surges caused by rapid voltagetransitions, made by pulse-width modulation (PWM) controltechnique, can cause motor insulation degradation, bearingfailure due to the resulted shaft leakage current, andunacceptable electromagnetic interference effects upon thecontrol circuits, as well as acoustic noises in the motor [23].The current source inverter (CSI) uses an inductor forenergy boosting in distinction from VSI that uses capacitor. Ithas several inherent advantages that includes its voltageboosting capabilities, its natural shoot-through and shortcircuitprotection capability, and a sinusoidal output voltagedue to the effect of the output ac filter capacitors, which aremuch smaller than the VSI’s dc capacitor [23].B. RectifiersIn series HEV and series-parallel HEV a synchronousgenerator is frequently used to convert mechanical energyproduced by ICE into electrical one. Rectifiers are required toconvert output AC of synchronous generator into DC forbattery. There are four common rectifier circuits in seriesHEV: uncontrolled full-bridge diode rectifier, controlled fullbridgethyristor rectifier, uncontrolled full-bridge dioderectifier with dc/dc boost converter and PWM voltage-sourcecurrent controlled rectifier [24]. Uncontrolled rectifiers do notallow the bidirectional energy flow that means samegenerators could not be used as starter machine to soft ICEstart.In regenerative braking mode the motor is controlled toachieve stored in the rotating part of traction motor kineticenergy, in that case the VSI, that controls the speed of the ACmotor, is operated as a PWM rectifier.C. DC/DC ConvertersThe typical application of a buck converter in a HEV andEV is to step down the high voltage (HV) battery voltage(typically 200 – 400 V) to charge the auxiliary battery(14 V) [2]. With such high step-down voltage rate the dutycycle of the buck converter is small as well that affects thedesign of the inductor, capacitor, current ripple and voltageripple. Moreover, control and regulation of the buck converteroutput voltage becomes more difficult.Boost converter or non-isolated bidirectional DC/DCconverter is used to step up the HV battery up to HV DC bus.The best operating voltage for VSI that controls tractionmotor is around 600 V. As well that converter allows thebackward energy flow, from the DC link back to batteryduring the regenerative braking.Some application are required: a non-galvanic isolationbetween battery and DC link. In that case the best solution isisolated bidirectional DC–DC converter with a highfrequency AC link.D. Charging Systems for PHEV and EVThe charging system of the PHEVs and EVs is one of themost important parts of the whole system. Charging current,speed and efficiency are the main topics that need to bediscussed and standardized. Available today charging systemswith a charging time and energy needs are presented in Table1. There is couple of charging system topologies usednowadays.Typical on-board chargers limit the power because ofweight, space, and cost constraints and are dedicated tocharge the battery for a long period of time; an off-boardbattery charger is less constrained by size and weight [25].Uncontrollable charging systems are based on diodes andmostly bridges schemes cascade with DC/DC converters areused. Diode rectifier bridges have the following drawbacks:the input current harmonic content is high and absorbsreactive power from the grid [27]. The power factor could beimproved by using the controllable PWM rectifiers. Moreover,PWM rectifier has sinusoidal grid current, low THD andallows bidirectional energy flow (booth G2V and V2Gworking modes are possible).CharginglevelChargingtimeTABLE 1EV AND HEV CHARGING SYSTEMSChargerlocationPowersupplyVoltageMaxcurrentFast1-2 h0,3-0,5 h0,3-0,5 h3phLow 6-8 h 3,3 kW 230 V 16 A1ph3-4 h Onboard10 kW 400 V 167 kW 230 V 32 APrimary 2-3 h AOffboardDC 50 kW24 kW 400 V 32 A43 kW 400 V 63 A400 -500 V100 -125 AThere are several drawbacks of plug-in charging systems:the cable and connector typically delivers 2-3 times morepower than standard plugs at home and this increases risk ofelectrical shock especially in wet environments; the long wireposes a trip hazard and gives to poor aesthetics for suchsystems; in harsh climates that commonly have snow and ice,the plug-in charge point may become frozen onto thevehicle [27]. To overcome this drawbacks and inexistence ofphysical contact between the source and the load wirelessinductive charging systems could be used. The main benefitsof wireless charging systems are: the galvanic isolationrequires less maintenance, high output power and possibleusage in harsh environments (that is important for northregions as Estonia). The main drawbacks that can be pointedout are: resonant circuits hard to tune, electromagneticinterference, magnetic field does not penetrate metals (if thereis any metallic object in the middle of the magneticconnection the losses increase and the system may not work),magnetic radiation [28].V. CONCLUSIONSThe HEV and EV technology, including system, electricpropulsion, power electronics, and charging systems, has79

een reviewed. Together with previous studies [3] there aresome drawbacks of today’s HEV and EV drives what couldbe detected. The capacity of energy storage systems needs tobe extended in that case improving of total drive efficiency isvery important. One of the possible solutions is to jointogether different energy storage systems and advancedpower electronic schemes are required. Similarly some newpower electronic solutions are required for improving thecharging systems of future vehicles, to make charging of EVmore costumers friendly. There is no exactly solution forpropulsion system for HEV and EV that means electricalmotors and their control methods need to be studied morecarefully.There are a quantity of HEVs and EVs already available onthe market. However, an on-road test there is not alwayspossible to test each subsystem separately. In that case the testbenches of some standard parts of the vehicles seem as a goodsolution to concentrate on improving of the whole system.ACKNOWLEDGMENTPublication of this paper has been supported by EuropeanSocial Fund (project “Doctoral School of Energy andGeotechnology II”).REFERENCES[1] Nick A. Owen, Oliver R. Inderwildi, David A. King, "The status ofconventional world oil reserves – hype or cause for concern?" EnergyPolicy, vol. 38, no. 8, pp. 4743–4749, August 2010.[2] Chris Mi, M. Abul Masrur, David Wenzhong Gao, “Hybrid ElectricVehicles: Principles and Applications with Practical Perspectives” , 1sted., Publication A John Wiley & Sons, Ed. United Kingdom: A JohnWiley & Sons, Ltd., 2011[3] Anton Rassõlkin and Hardi Hõimoja, “Switching Locomotive as a Partof Smart Electrical Grid”, 8th Power Plant and Power System ControlConference, Toulouse, France, 2-5 September 2012[4] Hori, Y.; , "Future vehicle driven by electricity and control-research onfour wheel motored "UOT Electric March II"," Advanced MotionControl, 2002. 7th International Workshop on , vol., no., pp. 1- 14,2002[5] Iqbal Husain, “Electric and Hybrid Vehicle: Design Fundamentals”,CRC PRESS Boca Raton London New York Washington, D.C, 2005[6] F. Magnussen, “On design and analysis of synchronous permanentmagnet for field – weakening operation,” Ph.D. thesis, Royal Instituteof Tech., Sweden, 2004.[7] Momoh, O.D.; Omoigui, M.O.; , "An overview of hybrid electricvehicle technology," Vehicle Power and Propulsion Conference, 2009.VPPC '09. IEEE , vol., no., pp.1286-1292, 7-10 Sept. 2009[8] Mehrdad Ehsani, Yimin Gao, Ali Emadi, „Modern Electric, HybridElectric and Fuel Cell Vehicles: Fundamentals, Theory and Design“ -Taylor & Francis, 2009 - 656 pages[9] Ron Hodkinson and John Fenton “Lightweight Electric/Hybrid VehicleDesign” Butterworth-Heinemann Linacre House, Jordan Hill, OxfordOX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2,ISBN 0 7506 5092 3, 2001[10] A.F. Burke, “Hybrid/electric vehicle design operation and evaluation,”Society of Automotive Engineering paper 920447, 1992.[11] Caricchi, F.; Crescimbini, F.; Mezzetti, F.; Santini, E.; , "Multistageaxial-flux PM machine for wheel direct drive," Industry Applications,IEEE Transactions on , vol.32, no.4, pp.882-888, Jul/Aug 1996[12] Grammatico, S.; Balluchi, A.; Cosoli, E.; , "A series-parallel hybridelectric powertrain for industrial vehicles," Vehicle Power andPropulsion Conference (VPPC), 2010 IEEE , vol., no., pp.1-6, 1-3 Sept.2010[13] Verma, A.K.; Singh, B.; Shahani, D.T.; , "Grid to vehicle and vehicle togrid energy transfer using single-phase bidirectional AC-DC converterand bidirectional DC-DC converter," Energy, Automation, and Signal(ICEAS), 2011 International Conference on , vol., no., pp.1-5, 28-30Dec. 2011[14] Mehrdad Ehsani; Yimin Gao; Sebastien E. Gay; Ali Emadi; , “ModernElectric, Hybrid Electric, and Fuel Cell Vehicles : Fundamentals,Theory, and Design, Second Edition (Power Electronics andApplications Series)”, CRC Press; 1 edition, December 20, 2004[15] Gao, Y.; Ehsani, M.; , "Systematic design of fuel cell powered hybridvehicle drive train ," Electric Machines and Drives Conference, 2001.IEMDC 2001. IEEE International , vol., no., pp.604-611, 2001[16] Schaltz, E.; Khaligh, A.; Rasmussen, P.O.; , "Influence ofBattery/Ultracapacitor Energy-Storage Sizing on Battery Lifetime in aFuel Cell Hybrid Electric Vehicle," Vehicular Technology, IEEETransactions on , vol.58, no.8, pp.3882-3891, Oct. 2009[17] Bernard, J.; Delprat, S.; Buchi, F.N.; Guerra, T.M.; , "Fuel-Cell HybridPowertrain: Toward Minimization of Hydrogen Consumption,"Vehicular Technology, IEEE Transactions on , vol.58, no.7, pp.3168-3176, Sept. 2009[18] Ehsani, M.; Yimin Gao; Gay, S.; , "Characterization of electric motordrives for traction applications," Industrial Electronics Society, 2003.IECON '03. The 29th Annual Conference of the IEEE , vol.1, no., pp.891- 896 vol.1, 2-6 Nov. 2003[19] Wang Wei; Wang Qingnian; Yu Yuanbin; Zeng Xiaohua; Zou Naiwei; ,"Study on the Operation Region of Induction Traction Motor forElectric Vehicle," Measuring Technology and MechatronicsAutomation, 2009. ICMTMA '09. International Conference on , vol.2,no., pp.699-703, 11-12 April 2009[20] Byeong-Hwa Lee; Sung-Il Kim; Jeong-Jong Lee; Jung-Pyo Hong;Chang-Soo Park; , "Design of an interior permanent magnetsynchronous in-wheel for electric vehicles," Electrical Machines andSystems (ICEMS), 2010 International Conference on , vol., no.,pp.1226-1229, 10-13 Oct. 2010[21] Fei, W.; Luk, P.; Jinupun, K.; , "A new axial flux permanent magnetSegmented-Armature-Torus machine for in-wheel direct driveapplications," Power Electronics Specialists Conference, 2008. PESC2008. IEEE , vol., no., pp.2197-2202, 15-19 June 2008[22] Fei, W.; Luk, P.C.K.; Shen, J.; Wang, Y.; , "A novel outer-rotorpermanent-magnet flux-switching machine for urban electric vehiclepropulsion," Power Electronics Systems and Applications, 2009. PESA2009. 3rd International Conference on , vol., no., pp.1-6, 20-22 May2009[23] Zhiqiao Wu; Gui-Jia Su; , "High-performance permanent magnetmachine drive for electric vehicle applications using a current sourceinverter," Industrial Electronics, 2008. IECON 2008. 34th AnnualConference of IEEE , vol., no., pp.2812-2817, 10-13 Nov. 2008[24] Al-Busaidi, A.; Pickert, V.; , "Comparative Study of Rectifier Circuitsfor Series Hybrid Electric Vehicles," Hybrid and Eco-Friendly VehicleConference, 2008. IET HEVC 2008 , vol., no., pp.1-6, 8-9 Dec. 2008[25] Yilmaz, M.; Krein, P.T.; , "Review of charging power levels andinfrastructure for plug-in electric and hybrid vehicles," Electric VehicleConference (IEVC), 2012 IEEE International , vol., no., pp.1-8, 4-8March 2012[26] Lei Shi; Haiping Xu; Dongxu Li; Zengquan Yuan; , "A novel highpower factor PWM rectifier inverter for electric vehicle chargingstation," Electrical Machines and Systems (ICEMS), 2011 InternationalConference on , vol., no., pp.1-6, 20-23 Aug. 2011[27] Wu, H.H.; Gilchrist, A.; Sealy, K.; Israelsen, P.; Muhs, J.; , "A reviewon inductive charging for electric vehicles," Electric Machines &Drives Conference (IEMDC), 2011 IEEE International , vol., no.,pp.143-147, 15-18 May 2011[28] Neves, A.; Sousa, D.M.; Roque, A.; Terras, J.M.; , "Analysis of aninductive charging system for a commercial electric vehicle," PowerElectronics and Applications (EPE 2011), Proceedings of the 2011-14thEuropean Conference on , vol., no., pp.1-10, Aug. 30 2011-Sept. 1 201180