AY 2019 20 Test 3 Numerical part with solutions

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ELECTRIC CONVERSION FROM GREEN SOURCES OF ENERGY Prof. Alberto Dolara Numerical exercise 1 < 07 September 2020 > 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 power processor for photovoltaic (PV) generator is composed by the cascade connection of a DC/DC converter , a three-phase PWM inverter and a line -frequency step -up three -phase transformer. Power processor ratings and technical data are the following: ► PV generator voltage range, VPV from 500 V to 800 V ► Rated power, Pn 400 kW ► Rated power factor, cosϕn 1 ► Rated frequency, fn 50 Hz ► Transformer rated voltage, high-voltage side, VHVn 25 kV (RMS, line to line) ► Transformer rated voltage, low-voltage side, VLVn 400 V (RMS, line to line) ► Transformer rated power, An 400 kVA ► Transformer short circuit voltage, vcc% 4 % ► Inverter LC output filter, inductance, L 100 μH ► Inverter LV output filter, capacitor, C 250 μF Calculations: 1. Calculate the DC bus voltage that allow the inverter to operate in the linear region when the grid voltage is (100 + Z) % ← the rated grid voltage (that is VHVn), for any output power. Consider the following assumptions:  Transformer windings resistance negligible.  Transformer no-load current negligible.  Current in the capacitor of the LC filter negligible. 2. Choose the type of DC/DC converter suitable for interfacing the photovoltaic generator to the inverter, and calculate the duty cycle range ( minimum and maximum value ). Consider the DC bus voltage previously calculated. 3. Calculate the minimum frequency modul ation ratio m f that allows to attenuate the amplitude of the…