Page - 223 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 410 2.1.2.Mode2[t1<tď t2] For thisoperationmode, the interval time is (0.5´Dd)Tsw, switchesQ3,Q4 are turnedonand switchesQ1,Q2 are all off. Bothvoltages across inductorsL1 andL2 are thenegativemiddle-link voltageVM, hence iL1 and iL2 decrease linearly. Thevoltages across inductancesL1 andL2 canbe representedas: L1 diL1 dt “L2diL2dt “´VM “´2VL (3) 2.1.3.Mode3[t2<tď t3] For thisoperationmode, the interval timeisDdTsw, switchesQ2,Q4 are turnedonandswitches Q1 andQ3 arealloff. ThevoltageacrossL1 is thedifferencebetweenthecharge-pumpvoltageVCB with themiddle-linkvoltageVM, andL2 is keeping thenegativemiddle-linkvoltage, thevoltages across inductancesL1 andL2 canberepresentedas follows: L1 diL1 dt “VCB´VM (4) L2 diL2 dt “´VM (5) 2.1.4.Mode4[t3<tď t4] Fromthisoperationmode, the interval time is (0.5´Dd)Tsw. SwitchesQ3,Q4 are turnedonand switchesQ1,Q2 arealloff, anditsoperation is thesamewith thatofMode2. 2.2.DischargeStateOperation Figures8and9showthecircuit configurationandcharacteristicwaveformsof thestudiedBDC indischargestate, respectively.Ascanbeseenthesefigures, switchesQ3,Q4 aredrivenwith thephase shiftangleof180˝;Q1,Q2 areusedfor thesynchronousrectifier. Indischargestate,whenS1,S3 are turnedonandS2,S4 are turnedoff; or elseS2,S4 are turnedonandS1,S3 are turnedoff. The low voltageVLwill charge theCM1 andCM2 tomakeVM1 andVM2 equal toVL, themiddle-linkvoltage VM is thentwice the low-sidevoltageVL, i.e.,VM=2VL. Referring to theequivalent circuits shown inFigure10, theoperatingprincipleof the studied BDCcanbeexplainedbrieflyas follows: 2.2.1.Mode1[t0<tď t1] The interval time is (Db´0.5)Tsw, switchesQ3 andQ4 are turnedon; switchesQ1 andQ2 areall off. For thehigh-sidestage, themiddle-linkvoltageVM staysbetweeninductanceL1 andL2,making the inductancecurrent increase linearly, andbegins todeposit energy. Thevoltagesacross inductances L1 andL2 canberepresentedas: L1 diL1 dt “L2diL2dt “VM “2VL (6) 2.2.2.Mode2[t1<tď t2] In thisoperationmode, the interval timeis (1´Db)Tsw. SwitchQ1,Q3 remainsconductingand Q2,Q4 are turnedoff. Thevoltagesacross inductancesL1 andL2 canberepresentedas: L1 diL1 dt “VM “2VL (7) L2 diL2 dt “VM´VH`VCB “2VL´VH`VCB (8) 223