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Control of hvdc system

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This presentation was presented to Dr. Chongru Liu in North China Electric Power University,Beijing,China by Mr. Aazim Rasool. This presentation will help to understand the control of HVDC system. Animations are not working like ppt. so I apologize on this.

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Control of hvdc system

1. 1. Presented by: Aazim Rasool 1134200011 Presented to: Dr. Chongru Liu 1 North China Electric Power University, Beijing , China
2. 2. AC DC 2 North China Electric Power University, Beijing
3. 3.  3 North China Electric Power University, Beijing
4. 4. Cost of HVDC is less One cable required instead of three 4 North China Electric Power University, Beijing
5. 5. Same poles can be use. Moreover, slim and smart poles are used for DC transmission 5 North China Electric Power University, Beijing
6. 6. AC Transmission Line Corridor 6 North China Electric Power University, Beijing
7. 7. DC Transmission Line Corridor 7 North China Electric Power University, Beijing
8. 8. DC Transmission Line Corridor 8 North China Electric Power University, Beijing
9. 9.  DC transmission system 9 North China Electric Power University, Beijing
10. 10.  In 6-phase;each transistor operate for 120o . Eac -- T1&T2 Ebc -- T3&T2 Ebc -- T3&T4 Eba - T5&T4 Eca - T5&T6 Ecb - T1&T6 10 North China Electric Power University, Beijing
11. 11.  Graph representation of operation. 11 North China Electric Power University, Beijing
12. 12.  Figure representing, when firing delay angle ‘α’ changes  To make eac(α=0) ; switch ON transistors 1 & 2  at ‘-60o ‘  for ‘60o ‘.  To make eac(α≠0) ; switch ON transistors 1 & 2  at ‘-60o + α’  For ‘60o + α‘. 12 North China Electric Power University, Beijing
13. 13.  V 1 V 3 V 5 V 2V 6V 4 Phase A Ud Phase B Phase C Id Power FlowAC System DC System V 1 V 3 V 5 V 2V 6V 4 Phase A Ud Phase B Phase C Id AC System DC SystemPower Flow 30 60 90 120 150 180 0 +Ud -Ud 160 5 Rectifier Operation Inverter Operation a Rectifier Operation Inverter Operation 13 North China Electric Power University, Beijing
14. 14. 30 60 90 120 150 180 0 a +Ud -Ud 160 Limita Inv 5 Limita Rect. Rectifier Operation Inverter Operation tw o 60=a Ud o 30=ao 0=a o 90=a o 120=a o 150=a -Ud tw Ud Ud 14 North China Electric Power University, Beijing
15. 15.  Direct current from the rectifier to the inverter  Power at the rectifier terminal  Power at the inverter terminal cilcr doidor d RRR VV I   = a coscos ddrdr IVP = 2 dLdrddidi IRPIVP == 15 North China Electric Power University, Beijing
16. 16. α:  Ignition delay angle for rectifier  α min = 5 o (Required to charge thyristor)  α op. = 15-20 o (Room for VR )  α ≤ 900 γ:  Extinction advance angle  γmin = 15o (50Hz)/ 18o (60Hz) – avoid comm. failure ** 1800 ≥ α ≥ 900 (For inverter mode) 16 North China Electric Power University, Beijing
17. 17. * µ= overlap angle 17 North China Electric Power University, Beijing
18. 18. B A 2 C 1 a u u Vd u 3 a a α= firing Angle μ= Commutation Interval 18 North China Electric Power University, Beijing
19. 19.  Internal voltages, Vdorcosa and Vdoicos are used to control the voltages at any point on the line and the current flow (power)  This can be accomplished by:  Controlling firing angles of the rectifier and inverter (for fast action)  Changing taps on the transformers on the AC side (slow response)  Power reversal is obtained by reversal of polarity of direct voltages at both ends 19 North China Electric Power University, Beijing
20. 20. Ideal Characteristic:  Under normal Condition;  Rectifier maintains CC (Constant Current)- α  Inverter maintains CEA (Constant Extinction Angle) γ min dciLdoid IRRVV )(cos =  20 North China Electric Power University, Beijing
21. 21. Actual Characteristic Abnormal Condition FA represents min. ignition angle (CIA mode) AB represents Constant Current (CC mode) Rectifier *CIA shows maximum rectifier voltage 21 North China Electric Power University, Beijing
22. 22. Actual Characteristic Abnormal Condition GD represents min. extinction angle (CEA mode) GH represents Constant Current (CC mode) Inverter *CEA shows maximum inverter voltage Operating Point Operating Point at abnormal 22 North China Electric Power University, Beijing
23. 23.  Each converter can work as a rectifier as well as inverter.  O.P 1  C1=rectifier(CC)  C2=inverter(CEA)  O.P 2  C2=rectifier(CC)  C1=inverter(CEA) Operating Point 2 Operating Point 1 Current is same 23 North China Electric Power University, Beijing
24. 24. Decrease voltage at station B or increase voltage at station A. power flows from A B Normal direction Decrease voltage at station B or increase voltage at station A. power flows from A B Normal direction 24 North China Electric Power University, Beijing
25. 25. 25 North China Electric Power University, Beijing
26. 26. Power reversal is obtained by reversal of polarity of direct voltages at both ends. 26 North China Electric Power University, Beijing
27. 27. CONSTANT VOLTAGE MODE CONSTANT B MODE  V-I characteristic is flat  Higher value of γ  Back-up type  γ is comparatively less γ is set at higher; maintain low constant voltage γ is se at medium; make greater voltage then CVM 27 North China Electric Power University, Beijing
28. 28.  Small change in AC-Voltage cause large change in DC-Current.  There is a Mode Ambiguity. 28 North China Electric Power University, Beijing
29. 29.  Fig a, represents constant β mode.  Fig b , represents constant Voltage mode. 29 North China Electric Power University, Beijing
30. 30.  Voltage-Dependent Current-Order Limit.  Under low voltage(drop >30%);current also decreases to low level 30 North China Electric Power University, Beijing
31. 31. Graph shows the function of VDCOL in control graph of rectifier and inverter characteristic 31 North China Electric Power University, Beijing
32. 32.  “Power system stability and control”, parabha qundar  Course Lectures “HVDC” , A.M Gole.  “Presentation of HVDC Transmission”,Zunaib Ali 32 North China Electric Power University, Beijing
33. 33. 33 North China Electric Power University, Beijing