AY 2021 22 Test 5 Numerical part with solutions

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ELECTRIC CONVERSION FROM GREEN SOURCES OF ENERGY Prof. Alberto Dolara 1 ©Prof. Alberto Dolara – All rights reserverd Numerical exercise 1 < 14 February 2023 > A power processor for standalone Photovoltaic (PV) generator with Battery Energy Storage System (BESS) is composed two DC/DC converters for PV arrays (DC/DC A), a DC/DC converter for battery storage (DC/DC B) and a single -phase full bridge PWM inverter sharing the same DC bus, as shown in the picture on the right. Ratings are reported in the follow: DC/DC A converter ratings (PV): ► Maximum current, IPV,max 13.5 A ► Input voltage range, VPV,n from 140 V to 980 V DC/DC B converter ratings (PV): ► Maximum power, PBESS,max 6 kW ► Input voltage range, VBESS,n from 350 V to 560 V Inverter: ► Rated power, PAC,n 6 kW ► Minimum power factor, cosϕmin 0.8 ► Rated frequency, f 50 Hz ► Rated AC side voltage, VAC,n 230 V DC Bus: ► Voltage, VDC,bus kept constant at 600 V Grid: ► Grid voltage range, Vgrid,n 230 V ± 5% PV modules: ► Open circuit Voltage, V0C 44.5 V ► Short circuit Current, ISC 10.8 A ► Maximum Power in STC, PMPP 390 W ► MPP Voltage, VMPP 37.9 V ► MPP Current, IMPP 10.3 A PV string 1: ► Number of PV modules in series 7 PV string 2: ► Number of PV modules in series 8 Preliminary Definitions and Calculations 1. Calculate the minimum DC bus voltage that allow the inverter to operate in the linear region for any value of the grid voltage. The maximum voltage drop (in amplitude) across the inverter low-pass output filter is 7 % of the rated grid voltage. Assume ideal switches. 2. Choose the most suitable DC/DC converter for interfacing the PV strings to the DC link and calculate the minimum and maximum value of the duty cycle. Consider the rated DC bus voltage and assume ideal switches. 3. Choose the most suitable…