Cal Poly SuPER System Photovoltaic Array Universal DC-DC Step Down Converter

Cal Poly SuPER System Photovoltaic Array Universal DC-DC Step Down Converter Joseph Witts Standard converter topologies are usually presented with a voltage source as the input supply to the converters. However, a photovoltaic (PV) array has the I-V characteristics of a current source not a voltage source. This thesis details the design process of modifying the standard Buck and synchronous Buck converter topologies to function with either a voltage or current source input, making them universal DC-DC step down converters. This is accomplished by placing a capacitor at the converter's input to supply the pulsating current required for the Buck topologies to function properly. The equations for determining the capacitor's size and RMS current rating are derived, and a prototype of each topology was constructed and analyzed. Also, the issues that arose during the integration of the converter's into the SuPER system are discussed. The Cal Poly Sustainable Power for Electrical Resources (SuPER) project seeks to build a stand alone photovoltaic (PV) unit that can supply the energy needs of a single family home. Before the start of this thesis the SuPER project was using an off-the-shelf DC-DC converter to step down the PV array's voltage, perform maximum power point tracking, and act as a charge controller for the battery. One goal ofthe project is to have a Cal Poly built DC-DC converter that can perform all the functions of the off-the-shelf DC-DC converter currentlybeing used.