Seite - 313 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 10 ȱ Figure5.TopologiesofZ-source (a) andq-Zsource (b). Thispaper introduces theq-Zsource,not forstabilizingtheoutput,but toproduceachangeable outputvoltage,whichcanadjust thechargingcurrent, andhence, thechargingpower. Theoverall systemschematic isdepicted inFigure6. Figure6.Overall schematicof thewirelesspower transfersystem. It clearlyshowsthat thewholesystemconsistsof thepowersource, theq-Zsource, theHBridge, theprimaryandsecondaryresonators, therectifier, thefilterandthebatterypack.Unlikeothersystem structures, the q-Zsource between the power source andHBridge is first employed to boost the wirelesschargingpower. Bycontrolling theshoot-throughstateof theHBridge, the inputvoltage to theHBridgecanbeboostedthroughtheq-Zsource, so the transmittercurrentcanbeadjusted,and hence, thechargingcurrentandpower for thebatterypack.Comparedwithsometypicalprimaryunit currentcontrolmethods[35], theproposedmethodhastwomajormerits: first, thedigitalcontrolof the q-Zsourcecanbeintegratedintotheprimarymicroprocessor,andtherearenoactivepowerswitches in theproposedmethod,whichcan lower thesystemcost. Secondly,all thecurrentorpowerregulation devicesare includedintheprimaryunit,andthisdesignisbeneficial tothevehicleminiaturizationand lightness,as thesecondaryunit canbesmallandlight. There isanadditionalMOSFET,S5, connected inparallelwithD1 inFigure6,andit isusedtoavoiddiscontinuousoperationconditionswhenthe loadis light. Tofurtherdemonstrate it,assumethat there isa light loadandtheq-Zsourceonlyconsists ofD1. ThediodeD1 will turnoffwhen the currentflowing through it decreases to zero, thus the connectionbetweentheq-Zsourceandpowersource isdisconnected,andtherelationshipbetween themwillnotbe tenable. Thisabnormalstatemakes theoutputvoltageofq-Zsourcechangefreely, andfurther inducesadeclineof thesystemtransfercharacteristics. Thisunwantedphenomenonwill disappear ifS5 is turnedonoroffactively.S5 canbealsoremovedif thesystemalwaysworksat the ratedstate. Theq-Zsourcehas twotypicaloperatingstates, andtheequivalentcircuitsaredepicted in Figure7. 313