Design and implementation of a multi-port power converter topology for DC nano-grid

Abstract

This thesis presents a novel multi-port power converter topology for DC nanogrid applications. The proposed topology integrates energy sources, loads and energy storing elements using DC-link and magnetic coupling using a single converter. As a result, it has fewer component counts and conversion stages than the individual converters for each element in the nano-grid, which paves the way for a more e cient system. The rst part of this thesis presents a PV converter topology designed and developed in the laboratory. This circuit topology integrates two PV modules and boosts the input voltage into a 120V DC voltage level. However, switching loss of the converter is signi cant due to the hard-switching operation. Therefore, switching control strategy of the converter has been modi ed to minimize switching losses with the assistance of the existing parasitic elements. The operation of the power converter with the proposed switching control strategy is mathematically analyzed and veri ed using simulation results. The design is further validated using the experimental results obtained using a 250 W hardware prototype. Moreover, a bi-directional high step-up/down converter is designed and developed to integrate an energy storing element into the system. The bi-directional converter step downs 120 V DC link voltage to an extremely low voltage (10-16 V DC) to charge a Li-ion battery pack. When the solar power is not available, the proposed converter discharges the Li-ion battery to regulate the 120 V DC link. The operation of the battery interfacing converter is validated and veri ed using both simulation and experimental results. The conclusions and suggestions for the further development have been presented at the end of this thesis.