- Q3 A A Variable Speed Full Power Converter Fpc Based Wind Turbine Has The Characteristic Of Figure Q3 The Generator 1 (92.19 KiB) Viewed 23 times
- Q3 A A Variable Speed Full Power Converter Fpc Based Wind Turbine Has The Characteristic Of Figure Q3 The Generator 2 (110.44 KiB) Viewed 23 times
Q3. a) A variable-speed full power converter (FPC) based wind turbine has the characteristic of Figure Q3. The generator used is a synchronous generator. The turbine operates at its rated speed (1800 rev/min) in a wind speed of 12 m/s. At rated speed the frequency modulation index of the wind turbine side voltage source converter is 30. 1.4 13 m/s 1.2 Pitch angle control 1 12 m/s 20.8 11 m/s Power (pu) : 0.6 Electronic control for maximum power extraction 10 m/s 9 m/s 0.4 8 m/s 7 m/s 6 m/s 0.2 5 m/s 0 0 0.2 0.6 0.8 1 1.2 0.4 Generator rotational speed (pu) Figure Q3. Variable-speed wind turbine characteristic What should be the modulation index at a wind speed of 10 m/s to extract maximum power? [9 marks]
c) Figure Q4 shows an offshore wind farm consisting of 35 wind turbines connected to the array strings. The generated power is transmitted to the shore via one 220 kV cable. Shunt reactors are used at onshore and offshore to compensate the cable reactive power. At offshore, 66 kV is stepped up to 220 kV. At onshore, 220 kV is stepped up to 400 kV to connect to the transmission network. At the onshore substation, a dynamic reactive power compensation plant (static VAr compensator, SVC) is used to meet the Grid Code reactive power requirement. Offshore substation Onshore substation Offshore transformeri Onshore transformer To transmission Network Arraytring 1 Баку 220V 400V Export Cable Array string 2 Interface Point 123 for complaince Array string Offshore mactar SVC compensation plant Onshore reactor Figure Q4. Electrical schematic of a simple wind farm connection to shore The following data for the wind farm is provided: Each wind turbine generator rating 10 MW Export cable length 65.5 km Cable resistance 0.035 2/km Cable reactance 0.115 12/km Cable capacitance 0.213 F/km Supply frequency 50 Hz Question 4 continues overleaf Please turn over - 5 - Question 4 continued 0 Transformer sizes of 355 MVA and 360 MVA have been proposed for the offshore substation transformer, which will be the most suitable transformer size assuming a power factor of 0.98? Show calculations to support the selected transformer. [2 marks] (1) What is the total capacitive reactive power generated by the 220 kV export cable? [2 marks] (ii) The reactive power generated by the export cable is to be 60% compensated by the 220 kV onshore and offshore shunt reactors. Due to the current rating available on the export cable, 55% of the total compensation is achieved by the onshore shunt reactor. Calculate the sizes for the onshore and offshore shunt reactors. Give your answer to the nearest whole number in MVAr. [3 marks] (iv) At 50% of the generation, the 220 kV export cable current is 459 A. What is the total reactive power loss due to the inductance of the export cable when carrying 459 A? [2 marks] V) At 50% generation, the offshore transformer consumes 10 MVAr and onshore transformer consumes 12 MVAr. Considering the reactive power consumption by the transformers and cable at 50% generation, what will be the minimum size of the SVC compensation plant needed to meet the UK Grid Code reactive power injection (capacitive) requirement at 50% generation? [NOTE: the Grid Code requires 0.95 power factor reactive power injection at 50% generation.] [6 marks)