AY 2021 22 Test 2 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 < 25 July 2022 > An Electric Vehicle (EV) charging station consists of: ► 1 PhotoVoltaic (PV) generator; ► 10 charging points; ► connection to AC three-phase Medium Voltage (MV) grid by means of a transformer and AC/DC static converter; as sketched in the figure on the right. PV generato r and charging points are connected by means of a DC microgrid whose voltage is kept constant at the value of 600 V. Each charging point implements Vehicle to Grid (V2G) technology, that enables energy both to charge EVs batteries and to supply the grid from the EVs batteries. Ratings are reported in the follow: PV generator: ► Maximum power, P PV 800 kW PV generator converter (DC/DC A): ► Rated power, PDCDC-A 1000 kW ► Maximum power point voltage range, VMPP from 400 V to 950 V Charging point: ► Rated power, PChargingPoint 200 kW ► Battery side voltage, VBatterySide from 250 V to 350 V EVs batteries: ► Open circuit voltage, VOC (SOC) V OC (SOC) = 280 + SOC · 50 V (SOC = State Of Charge; 0 ≤ SOC ≤ 1) ► Equivalent internal resistance, Rbatt 25 mΩ Transformer nameplate: Rated frequency fn 50 Hz Vector group Dy11 Nominal apparent power SMVn 1600 kVA Voltage ratings Nominal voltage MV (line-to-line) VMVn 23 kV Nominal voltage LV (line-to-line) VLVn 300 V Short circuit tests Short circuit voltage vcc 6 % Short circuit power factor cos(ϕcc ) 0.25 Open circuit test Open circuit active power P0 2800 W Open circuit current I0 0.8 % (continued on next page) 2 ©Prof. Alberto Dolara – All rights reserverd Preliminary Definitions and Calculations 1. Choose the type of DC/DC converter suitable for interfacing the PV generator to the DC grid and calculate the…