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Electrical Power Engineering 3 Power Electronics

Electrical Power Engineering 3 Power Electronics. Dr Ewen Macpherson Dr Sasa Djokic Dr Markus Mueller. Electrical Power Engineering 3. Power Systems 14 lectures Power Electronics 10 lectures Powerway lab exercise, 2 mornings Castaway power system design exercise, weeks 6-11.

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Electrical Power Engineering 3 Power Electronics

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  1. Electrical Power Engineering 3Power Electronics Dr Ewen Macpherson Dr Sasa Djokic Dr Markus Mueller

  2. Electrical Power Engineering 3 • Power Systems • 14 lectures • Power Electronics • 10 lectures • Powerway • lab exercise, 2 mornings • Castaway • power system design exercise, weeks 6-11

  3. Electrical Power Engineering 3 Assessment: • 60% Exam (Power Systems, Power Electronics) • 15% Powerway • 25% Castaway

  4. Electrical Power Engineering 3 Powerway: • Starts week 2 • 2 mornings total • Groups of 8-12 • Work in pairs Check when you are due to attend! Prepare Beforehand

  5. Electrical Power Engineering 3 Castaway: • Design power system expansion in Sri Lanka • Starts week 6 • Groups of 5 (approx.) • Power System simulation (“Powerworld”) • Costings required • Presentation week 11

  6. Power ElectronicsDr Ewen Macpherson • Lectures • Monday 2-3 (every week) • Examples Class • Friday 2-3 (every 3rd week) • Tutorials • Wednesday 12-1 (weeks 4/5 and 9/10)

  7. Power Electronics Recommended Text: Power Electronics: Converters, Applications & Design Mohan, Undeland & Robbins (Wiley) (also used for Power Electronics 4)

  8. Power Electronics uses Semiconductor Devices to process power (1W to 10,000MW)

  9. Devices

  10. Circuits • Rectifier converts ac → dc • Inverter converts dc → ac • (dc) chopper converts dc → dc • ac controller converts ac → ac General term for all: Converter

  11. Applications Motor Speed Control: Speed controlled by varying Vdc

  12. Applications Uninterruptible Power Supplies (UPS): For critical loads where a mains failure is unacceptable • Computers • Safety systems (oil rigs) • Emergency lighting (hospitals, cinemas)

  13. Applications Uninterruptible Power Supplies:

  14. High Voltage DC Power Transmission (HVDC): AC normally used, except: bulk power transmission, long distances submarine cables 2000 MW cross-channel link, France-UK 500 MW Scotland-Ireland link Applications

  15. Applications High Voltage DC Power Transmission (HVDC):

  16. Applications Electronic Power Supplies: All electronic equipment needs a power supply Worldwide market: $20 billion?

  17. ThyristorSCR – Silicon Controlled Rectifier • 4 layer (p-n-p-n) device • Switched on by applying gate pulse • Stays on when gate signal removed, if current flowing through it • Like a diode, current only flows in one direction

  18. Thyristor • Reverse bias • blocking • reverse breakdown voltage exceeded - dies!

  19. Thyristor • Forward bias • blocking • forward breakover voltage exceeded – turns on

  20. Thyristor • Forward bias – gate pulse applied • turns on • stays on

  21. Thyristor – Example Circuit • Short gate pulse (3V, 20us, 50mA to 1A) • turns on • Gate pulse removed • stays on if current > holding current

  22. Thyristor Serious problem: • Not easily switched off • Only switches off when current through it goes to zero (or drops below holding current)

  23. Power MOSFET • Voltage controlled device • Remove gate drive to turn off • Very low gate current • Very high speed (up to 10MHz) • Up to 100A, 1,200V

  24. Gate Turn Off Thyristor (GTO) • Current controlled device • Turned off by negative gate pulse • Very high gain at turn-on • Low gain at turn-off (typically 4) • Low frequency (up to 3 kHz) • Up to 6.5kV, 4kA

  25. Insulated Gate Bipolar Transistor (IGBT) • Combines high gate impedance of MOSFET with high current capability of BJT • Medium frequency (up to 100 kHz) • Up to 2.4 kA, 6.5 kV

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