Page - 307 - in Emerging Technologies for Electric and Hybrid Vehicles

Article DesignandControlofa3kWWirelessPower TransferSystemforElectricVehicles ZhenshiWang1,2,XuezheWei2,*andHaifengDai1,2 1 CleanEnergyAutomotiveEngineeringCenter,TongjiUniversity,No. 4800,CaoanRoad,Shanghai201804, China;1022wangzhenshi@tongji.edu.cn 2 SchoolofAutomotiveStudies,TongjiUniversity,No. 4800,CaoanRoad,Shanghai201804,China; tongjidai@tongji.edu.cn * Correspondence:weixzh@tongji.edu.cn;Tel.:+86-135-0184-8129 AcademicEditor:K.T.Chau Received: 13November2015;Accepted: 17December2015;Published: 24December2015 Abstract: This paper aims to study a 3 kWwireless power transfer system for electric vehicles. First, theLCL-LCLtopologyandLC-LCseries topologyareanalyzed,andtheir transferefficiencies under thesametransferpowerarecompared. TheLC-LCseries topology isvalidated tobemore efficient thantheLCL-LCLtopologyandthus ismoresuitable for thesystemdesign. Thenanovel q-Zsource-basedonlinepowerregulationmethodwhichemploysaunique impedancenetwork(two pairsof inductorsandcapacitors) tocouple thecascadedHBridgeto thepowersource isproposed. Bycontrolling the shoot-throughstateof theHBridge, thechargingcurrent canbeadjusted, and hence, transferpower. Finally,aprototype is implemented,whichcantransfer3kWwirelesslywith ~95%efficiencyovera20cmtransferdistance. Keywords:wirelesspower transfer (WPT); topologyanalysis;powerregulation;electricvehicle 1. Introduction Researchonwirelesspower transferbegansoonthereafter the famousTeslacoilswere invented byNikolaTesla in1889 [1,2], andmanygoodresultshavebeenachieved[3–6]. In2007, researchersat MITproposedstronglycoupledmagnetic resonances (SCMR),bywhich theywereable to transfer 60wattswirelesslywith~40%efficiencyoverdistances in excess of 2m [7]. Various researchhot spots, includingsystemarchitectures,optimizationdesign, frequencysplitting, impedancematching and special applications, have been investigated [8–14]. Wireless power transfer is very suitable for charging electric vehicles [15–17], as it can avoid the troublesomeplug-inprocess, provide an inherentelectrical isolationandadapt toharshenvironments.However,SCMRisnotappropriate for automotiveapplications, as itsoperating frequency isveryhigh,whichgoesbeyondthe limitation ofSAEJ2954 (work inprogress). Asanotherkindofwirelesspower transfer techniques, inductive power transfer (IPT) has developed formore than twenty years [5], and itmainly focuses on the highpower levelapplications,where the issuesofconcernnormally includepowerconversionand control [18,19],magnetic structuredesign[20], controlalgorithmandstrategy[21,22]aswellascircuit topology [23]. Basically, bothSCMRand IPTconforms toFaraday’s andAmpere’s laws, and their differencesprimarily includethedesignapproaches, systemarchitectures,parameterselectionand transfercharacteristics [6,24]. This paper aims to studya3kWvehicle-mountedwirelesspower transfer system, onwhich twokeyparts, theresonant topologyanalysisandcomparison,andtheonlinepowerregulation,are elaborated.Manyresonant topologiesareavailable forwirelesspower transfersystem,but themost basiconesareonlyseries-series, series-parallel,parallel-seriesandparallel-parallel [23], andtheothers are all derived from these ones. Awireless power transfer system for electric vehicles requires a Energies 2016,9, 10;doi:10.3390/en9010010 www.mdpi.com/journal/energies307