Module Integrated DC-DC Converter for Integration of Photovoltaic Source with DC Micro-grid

A ac distribution system is very common in various commercial installations. Most of the loads require front end ac-dc converter to interact with the ac system. Also, various storage systems and renewable sources connect to the ac system through dc-ac converters. These multistage conversions in the power flow path from renewable sources and storage systems to the loads reduce system efficiency. In view of this, an ac distribution system can be replaced by a dc distribution system within a commercial facility to improve overall system efficiency. This paper proposes a module integrated dc-dc converter for integration of a photovoltaic (PV) source with a dc distribution system. Current-fed topology is suggested to avoid limitations associated with large energy storage capacitor. The converter injects very low ripple, continuous current into the dc micro-grid. Effect of converter switching ripple at low insolation levels is analyzed. Use of L-C filter at the converter front end is proposed, to improve power extraction at low insolation levels. This modification also enables utilization of non-dissipative snubber circuits. The converter allows large voltage step-up ratio, suitable for integration of low voltage PV module with high voltage dc micro-grid. It has compact size and high reliability. The steady state and dynamic performance of the converter are studied through computer simulations and experimental tests.