AY 2019 20 Test 1 Numerical part with solutions

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ELECTRIC CONVERSION FROM GREEN SOURCES OF ENERGY Prof. Alberto Dolara Numerical exercise 1 < 30 June 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 are the following: ► Rated power, P 250 kW ► Rated power factor, cosϕ 1 ► Rated frequency, f 50 Hz ► Transformer rated voltage, high-voltage side, VAC,HV 20 kV (RMS, line to line) ► Transformer rated voltage, low-voltage side, VAC,LV 300 V (RMS, line to line) ► PV generator voltage range, VPV from 700 V to 1000 V Calculations: 1. Calculate the DC bus voltage that allow the inverter to operate in the linear region up to a grid voltage that is (5 + X) % ← higher than the grid voltage. The maximum voltage drop (in amplitude) across the inverter low - pass output filter and the transformer is 8% of the low-voltage side rated voltage. Assume ideal switches. 2. Choose the type of DC/DC converter suitable for interfacing the photovoltaic generator to the inverter, and calculate the minimum and maximum value of the duty cycle. Consider the DC bus voltage previously calculated. 3. Calculate the minimum inductance that allows the DC-DC converter to operate in Continuous Conduction Mode (CCM) in the power range from 5% to 100% of the rated power and for any input voltages within the allowable PV generator voltage range. Consider the DC bus voltage previously calculated. The DC/DC converter switching frequency is 4 kHz. 4.…