ELECTRIC DRIVES CONVERTERS IN ELECTRIC DRIVE SYSTEMS MODULE 2 Dr. Nik Rumzi Nik Idris Dept. of Energy Conversion, UTM 2013

CONVERTERS - Module 2 AC-DC controlled rectifier approximate model SIMULINK examples open-loop closed-loop Switch Mode DC-DC converter 2-Q and 4-Q converters Small signal modeling unipolar bipolar SIMULINK example Current-controlled for SM converters Bridge converter hysteresis fixed frequency 3-phase VSI SVM-based

Switch mode DC-DC converter Two-quadrant converter Va T1 + Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2 T1 conducts  va = Vdc

Switch mode DC-DC converter Two-quadrant converter Va T1 + Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2 D2 conducts  va = 0 T1 conducts  va = Vdc Va Eb Quadrant 1 The average voltage is made larger than the back emf

Switch mode DC-DC converter Two-quadrant converter Va T1 + Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2 D1 conducts  va = Vdc

Switch mode DC-DC converter Two-quadrant converter Va T1 + Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2 D1 conducts  va = Vdc T2 conducts  va = 0 Eb Va Quadrant 2 The average voltage is made smallerr than the back emf, thus forcing the current to flow in the reverse direction

? Switch mode DC-DC converter Va(s) vc(s) DC motor Two-quadrant converter Switching signals obtained by comparing control signal with triangular wave Vdc + Va − vtri q vc We want to establish a relation between vc and Va AVERAGE voltage Va(s) vc(s) DC motor ?

Switch mode DC-DC converter Two-quadrant converter Ttri ton 1 Vc > Vtri Vc < Vtri vc Vdc

Switch mode DC-DC converter Two-quadrant converter d 0.5 vc -Vtri Vtri -Vtri vc For vc = -Vtri  d = 0

Switch mode DC-DC converter Two-quadrant converter d Vtri 0.5 vc -Vtri Vtri vc For vc = -Vtri  d = 0 For vc = 0  d = 0.5 For vc = Vtri  d = 1

Switch mode DC-DC converter Two-quadrant converter d Vtri 0.5 vc -Vtri Vtri vc For vc = -Vtri  d = 0 For vc = 0  d = 0.5 For vc = Vtri  d = 1

Switch mode DC-DC converter Two-quadrant converter Thus relation between vc and Va is obtained as: Introducing perturbation in vc and Va and separating DC and AC components: DC: AC:

Switch mode DC-DC converter Two-quadrant converter Taking Laplace Transform on the AC, the transfer function is obtained as: va(s) vc(s) DC motor

Switch mode DC-DC converter Four-quadrant converter leg A leg B + Vdc  D1 D3 Q1 Q3 + Va  D4 Q4 D2 Q2 Positive current va = Vdc when Q1 and Q2 are ON

Switch mode DC-DC converter Four-quadrant converter leg A leg B + Vdc  D1 D3 Q1 Q3 + Va  D4 Q4 D2 Q2 Positive current va = Vdc when Q1 and Q2 are ON va = -Vdc when D3 and D4 are ON va = 0 when current freewheels through Q and D

Switch mode DC-DC converter Four-quadrant converter leg A leg B + Vdc  D1 D3 Q1 Q3 + Va  D4 Q4 D2 Q2 Positive current Negative current va = Vdc when Q1 and Q2 are ON va = Vdc when D1 and D2 are ON va = -Vdc when D3 and D4 are ON va = 0 when current freewheels through Q and D

Switch mode DC-DC converter Four-quadrant converter leg A leg B + Vdc  D1 D3 Q1 Q3 + Va  D4 Q4 D2 Q2 Positive current Negative current va = Vdc when Q1 and Q2 are ON va = Vdc when D1 and D2 are ON va = -Vdc when D3 and D4 are ON va = -Vdc when Q3 and Q4 are ON va = 0 when current freewheels through Q and D va = 0 when current freewheels through Q and D

Switch mode DC-DC converter Four-quadrant converter Bipolar switching scheme vc vtri + Vdc − q -Vdc + VAB  2vtri vc vA Vdc vB Vdc vAB Vdc -Vdc

Switch mode DC-DC converter Four-quadrant converter Bipolar switching scheme va(s) vc(s) DC motor

Switch mode DC-DC converter Four-quadrant converter + Vdc − vc vtri qa -vc qb Leg a Leg b Unipolar switching scheme Vtri vc -vc vA vB vAB The same average value we’ve seen for bipolar !

Switch mode DC-DC converter Four-quadrant converter Unipolar switching scheme vc(s) va(s) DC motor

Switch mode DC-DC converter SIMULINK EXAMPLES MATLAB v6.5, SIMULINK v5 2-quadrant converter Open-loop control Closed-loop control (current control)

Switch mode DC-DC converter SIMULATION EXAMPLES Id 2-quadrant converter + Vdc  vtri q vc rl_2q_average.mdl

Switch mode DC-DC converter SIMULATION EXAMPLES 2-quadrant converter Average model

Switch mode DC-DC converter SIMULATION EXAMPLES 4-quadrant converter + Vdc − vc vtri qa -vc qb Leg a Leg b

Switch mode DC-DC converter SIMULATION EXAMPLES 4-quadrant converter Average model unipolar_4q_with_id.mdl

Switch mode DC-DC converter SIMULATION EXAMPLES Closed-loop current control H-bridge converter  iref + + PI  Small signal model vc(s) Va(s) Ia(s) Iref(s)

Switch mode DC-DC converter SIMULATION EXAMPLES Closed-loop current control closed_loop_unipolar_4q_with_id.mdl

Switch mode DC-DC converter SIMULATION EXAMPLES Closed-loop current control ftri = 10 000 Hz 4-quadrant Unipolar 3-phase, 50Hz 2-quadrant DC-DC Switch mode Controlled rectifier For both DC-DC and Contr. Rectifier: Current controlled, Iref = 5 A Load: 250m , 20 Disturbance in DC source: ±70V, at 5Hz

Switch mode DC-DC converter SIMULATION EXAMPLES Closed-loop current control ftri = 10 000 Hz 4-quadrant Unipolar 3-phase, 50Hz 2-quadrant DC-DC Switch mode Controlled rectifier For both DC-DC and Contr. Rectifier: Current controlled, Iref = 5 ± 3 A, freq 5Hz Load: 250m , 20