HVDC Transimmison Systems
- 1. 1 HVDC SYSTEMS Prepared By: INDUBHUSHAN KUMAR Phd* (NITKKR) , M.Tech (IITR), B.Tech (WBUT)
- 3. 3 • Both Electrical Sciences and practical applications of electricity began with direct current. •.Electric lighting and power - using DC generators (run by steam engines). •First electric station (1882) – By Edison in New York. - 110V, U/G upto 1 mi. • With initial supremacy, why ac replaced dc? • Why again dc is being used for long HV transmission? •In 1880s & 1890s, Transformers, Induction motors, poly-phase circuits, steam turbines etc. • Controversy over supremacy of ac v/s dc arises. • But due to advantages of ac systems, ac systems became universal. Gen. Trans. Dist. & Utilization – all ac If dc needed – by rectification. • Victory of ac over dc was almost complete.
- 4. 4 • Despite it, some engineers never forgot the advantages of dc transmission • They supplemented ac with dc. - parallel DC link with ac - interconnected two ac systems with dc line. requires converters: one at sending end & other at receiving end. converters of high voltage & power needed. • Converters – an assembly of controlled switches • Valves – Devices having inherent un-directional conduction. Mercury Arc Convertors (1903) – Thyratrons Silicon Controlled Rectifiers (1960) – Thyristors • First commercial application – Between Swedish mainland & Gotland island (1954) - 20 MW, 90 km underwater link. • First HVDC system using thyristors - Eel river scheme (1972) - Between New Brunswick & Quebec (Canada) - 320 MW back-to-back.
- 5. • Mercury Arc Valves – First 25 years (1950- 1975) • Line Commutated Devices (Thyristor) – Second 25 years(1975-2000) • Self Commutated Converters (IGBT, GTO) – Next 25 years (from 2000) Developments of HVDC
- 6. 6 Main Applications of HVDC Systems 1. Bulk power transmission over long distances - AC systems not feasible (> 600 km)due to stability - Series & Shunt compensation requirements. - Beyond 600 km, HVDC is the better option. 2. Underwater cables longer than 30 km. - AC systems impractical (due to high charging currents) 3. Asynchronous link between two ac systems - AC link may not be feasible due to (i) stability problem (ii) two different operating frequencies.
- 7. 7 (a) AC Transmission System (b) DC Transmission System 1. Single circuit - 3 conductors 2. Double circuit – for higher reliability 3. Series & Shunt compensation - Two conductors - Sometimes only one. Ground as return path. Two conductor DC line = Double circuit 3φ ac line
- 8. 8 Point-to-Point (with DC line) Back-to-Back (Without DC line) Two terminal • Mono-polar • Bipolar • Homo-polar Multi-terminal Two-terminal links
- 9. 9
- 10. Mono-polar CSC-HVDC system with 12-pulse converters Bipolar CSC-HVDC system with one 12-pulse converter per pole Back-to-back CSC-HVDC system with 12-pulse converters
- 11. 11 Back-to-back Link (a) Line with parallel tap Multi-terminal links (b) HVDC Ring System (c) Series connected system Constant voltage scheme Constant current scheme
- 12. 12
- 13. HVDC Components 13 Converter Transformer Converter DC Smoothing Reactor AC Filter DC Filter
- 15. 15 REFERENCES : 1. E. W. Kimbark, “Direct Current Transmission”, Wiley Interscience, New York, 1971. 2. E. Uhlmann, “Power Transmission by Direct Current”, Springer-Verlag, Berlin, 1975. 3. K. R. Padiyar, “HVDC Power Transmission Systems, New Age International (P) Ltd., New Delhi, 1990 & 2nd Ed., 2010. 4. J. Arrillaga, “High Voltage Direct Current Transmission”, II Ed., IEE Power Engineering series, London, 1998. 5. P. Kundur, “Power System Stability and Control”, Tata-McGraw Hill, (Chapter 10), New Delhi, 2006. 6. X-Fan Wang, Y. Song and Malcolm Irving, “Modern Power Systems Analysis, (Chapter 5), Springer, 2008. 7. S. Kamakshaiah & V Kamaraju, “HVDC Transmission”, McGraw Hill, 2011 8. V. K. Sood, “HVDC and FACTS Controllers: Applications of Static Converters in Power Systems ”, Kluwer Academic Publishers, New York, 2004. 9. J. Arrillaga, Y. H. Liu and N. R. Watson, “Flexible Power Transmission: The HVDC Options”, John Wiley and Sons, 2007. 10. Chan-Ki Kim, V. K. Sood, Gil-Soo Jang, Seong-Joe Lim and Seok-Jin Lee, “HVDC Transmission: Power Conversion Application in Power Systems”, Wiley, 2009.