Control of hvdc system
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The document presents a detailed analysis of High Voltage Direct Current (HVDC) systems, highlighting their cost efficiency and advantages over AC systems, such as requiring fewer cables and using adaptable pole designs. It explains the operational characteristics of converters which can function as rectifiers or inverters, focusing on key parameters like firing angles and voltage control. Additionally, it discusses the implications of various operational modes and adjustments to voltage for power flow management in HVDC systems.
Control of hvdc system
- 1. Presented by: Aazim Rasool 1134200011 Presented to: Dr. Chongru Liu 1 North China Electric Power University, Beijing , China
- 2. AC DC 2 North China Electric Power University, Beijing
- 3. 3 North China Electric Power University, Beijing
- 4. Cost of HVDC is less One cable required instead of three 4 North China Electric Power University, Beijing
- 5. Same poles can be use. Moreover, slim and smart poles are used for DC transmission 5 North China Electric Power University, Beijing
- 6. AC Transmission Line Corridor 6 North China Electric Power University, Beijing
- 7. DC Transmission Line Corridor 7 North China Electric Power University, Beijing
- 8. DC Transmission Line Corridor 8 North China Electric Power University, Beijing
- 9. DC transmission system 9 North China Electric Power University, Beijing
- 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. Graph representation of operation. 11 North China Electric Power University, Beijing
- 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. 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. 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. 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. 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. * µ= overlap angle 17 North China Electric Power University, Beijing
- 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. 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. 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. 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. 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. 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. 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 North China Electric Power University, Beijing
- 26. Power reversal is obtained by reversal of polarity of direct voltages at both ends. 26 North China Electric Power University, Beijing
- 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. Small change in AC-Voltage cause large change in DC-Current. There is a Mode Ambiguity. 28 North China Electric Power University, Beijing
- 29. Fig a, represents constant β mode. Fig b , represents constant Voltage mode. 29 North China Electric Power University, Beijing
- 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. Graph shows the function of VDCOL in control graph of rectifier and inverter characteristic 31 North China Electric Power University, Beijing
- 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 North China Electric Power University, Beijing