Page - 308 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 10 resonant topologythatshouldhaveaunity-power-factorandacurrentsourcecharacteristic [18],no matterwhether thedistanceoranglebetweenthechassisandthegroundchangesornot. In thispaper thecharacteristicsof theLC-LCseriesandLCL-LCLtopologiesareanalyzedfirst, andweprovethat theybothhavetherequiredunity-power-factorandcurrentsourcecharacteristics. Thenthe transfer efficienciesof theLC-LCseriesandLCL-LCLtopologiesarecomparedunder thesametransferpower conditions,andthecomparisonresultsvalidate that theLC-LCseries topology ismoresuitable for the systemdesigndue to its higher transfer efficiency. In practice, thedistance or angle between vehiclechassisandgroundoftenchanges [25],asdriverscannotparktheircarsat thesamelocation every time,andnaturally,onlinepowerregulation is indispensable in thebatterychargingprocess. Traditionalpower regulationmethods include cascadeDC/DC,dead timemodulationandphase shiftingcontrol [26].However, thecascadeDC/DCmayincrease thenumberofdevices,decrease the powerdensityandlower the transferefficiency,whiledeadtimemodulationmaydistort theoutput wavesproducedbytheHBridge,andthephaseshiftingcontrol cannotboost the transferpower, soa novelq-Zsource-basedpowerregulationmethodisproposed in thispaper,whichemploys twopairs of inductorsandcapacitorsasauniqueboostnetwork. Thepowerregulation is realizedbycontrolling theshoot-throughstateof theHBridge,andtherearenoextrapowerswitchdevices. Bycombining thephaseshiftingcontrolandshoot-throughstatecontrol, thesquare-wavevoltageproducedbytheH Bridgecanbeadjustedarbitrarily,andhence, the transferpower. 2.ComparativeAnalysisofResonantTopologies 2.1. LC-LCSeriesTopology Wireless power transfer systemsnormally consist of a power source, aHBridge, a resonant topology, a rectifier aswell as a load. With the classical frequency-domainanalysis,we caneasily get theamplitude-frequencycharacteristicsof resonant topologies,whicharesteepspikes, andthe maximalpoint justemergesat theresonant frequency. Forexample, theLC-LCseries topologyhasa fourorder transfer function,andtheLCL-LCLtopologyhasasixorder transfer function. These two resonant topologiesonlyallowthefundamentalcomponentsof thesquare-wavevoltagesproduced bytheHBridge topass through, thus theresonant topology inputcanbesubstitutedbyaquasi-sine voltage source. As thepowerbatterieshave strongvoltage source characteristics, the rectifier and batterypackcanbealsosimplifiedintoaquasi-sinevoltagesource, theamplitudeofwhichdepends on thebatterypackvoltagemultipliedby4/π. ThesimplifiedLC-LCtopology [27,28] is shownin Figure1. ȱ Figure1.LC-LCseries topology. 308