Seite - 222 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 410 Referring to theequivalentcircuits showninFigure7, theoperatingprincipleof thestudiedBDC canbeexplainedbrieflyas follows. Charge State + VL - CH + VH - CM1 CM2 S1 S2 CL S3 S4 La Lb L1 L2 Q4 Q3 Q2 Q1 CB - vL1 + - vL2 + + vQ4 - + vQ3 - - vCB + - vQ2+ - vQ1 + + vM1 - + vM2 - SR Operation iLt iL1 iL2 iQ2 iCB iQ1 iCH iQ3iQ4 iLa iCL iCM1 iCM2 iL (a) Charge State + VL - CH + VH - CM1 CM2 S1 S2 CL S3 S4 La Lb L1 L2 Q4 Q3 Q2 Q1 CB - vL1 + - vL2 + + vQ4 - + vQ3 - - vCB + - vQ2+ - vQ1 + + vM1 - + vM2 - SR Operation iLt iL1 iL2 iQ2 iCB iQ1 iCH iQ3iQ4 iLa iCL iCM1 iCM2 iL (b) Charge State + VL - CH + VH - CM1 CM2 S1 S2 CL S3 S4 La Lb L1 L2 Q4 Q3 Q2 Q1 CB - vL1 + - vL2 + + vQ4 - + vQ3 - - vCB + - vQ2+ - vQ1 + + vM1 - + vM2 - SR Operation iLt iL1 iL2 iQ2 iCB iQ1 iCH iQ3iQ4 iLa iCL iCM1 iCM2 iL (c) Figure 7. Equivalent circuits of themodes during different intervals in charge state: (a)Mode 1; (b)Mode2,Mode4; (c)Mode3. 2.1.1.Mode1[t0<tď t1] The interval timeisDdTsw, in thismode,switchesQ1,Q3 turnedonandswitchesQ2,Q4 areall off. ThevoltageacrossL1 is thenegativemiddle-linkvoltage,andhence iL1decreases linearly fromthe initialvalue.Also, thevoltageacrossL2 is thedifferenceof thehigh-sidevoltageVH, thecharge-pump voltageVCB, andthemiddle-linkvoltageVM, and its level ispositive. Thevoltagesacross inductances L1 andL2 canberepresentedas: L1 diL1 dt “´VM “´2VL (1) L2 diL2 dt “VH´VCB´VM (2) 222