AY 2020 21 Test 3 Numerical part with solutions

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ELECTRIC CONVERSION FROM GREEN SOURCES OF ENERGY Prof. Alberto Dolara Numerical exercise 1 < 06 September 2021 > The numerical data of this problem depend on your ID number, as follows: Example: ID number = 10123456 → U = 1, V = 2; W = 3; X = 4; Y = 5; Z = 6. Numerical data that depend on your ID number are highlighted by the symbol “←” along the text. A large offshore wind farm consists of 150 wind turbines whose rated power is 4 MW each. Subsea cables (array cables), including both electric conductors for power transmission and optical fiber for communications, interconnects the wind turbines to the offshore converter station, where the power is collected and converted from three-phase AC to DC. Then, from the offshore converter station , two HVDC cables (export cables) transport the power to the mainland converter station, where the power is converted back into three -phase AC power and fed into the electricity transmission system. The output of each wind generators is AC three-phase, with the following ratings: ► Wind generators grid voltage, VW,n 33 kV ► Wind generators grid frequency, fW,n 50 Hz The mainland electricity transmission system is AC three-phase, with the following ratings: ► Electricity transmission system voltage, Vgrid,n 380 kV ► Electricity transmission system frequency, fgrid,n 50 Hz The ratings and the data of each HVDC cable are the following: ► DC voltage, VHVDC,n 300 kV ► DC current, IDC,max 1000 A ► Electrical resistance, RHVDC 12 Ω The RMS of the voltages of both offshore and mainland AC grids are compliant with the following criteria: ► The RMS of the voltage at the input of the offshore converter station is kept constant at its rated value, thanks to the control of the converters of each wind turbine. ► The RMS of the electricity…