Control strategy of bi-directional DC/DC converter for a novel stand-alone photovoltaic power system

Abstract

In this paper a novel solar cell stand-alone photovoltaic power system is proposed, which is mainly composed of a uni-directional DC/DC converter and a bi-directional DC/DC converter. Compared to the traditional stand-alone photovoltaic power system, this system exhibits the advantages of better protection and more efficient control on charge/discharge of the battery. Furthermore, it can make better use of solar energy and realize energy management of the system. The key point of energy management for the system is to control the bi-directional converter efficiently, where bi-directional voltage and current must be controlled. In this paper, the bi-directional control strategy of bi-directional converter is proposed, which operates at three operation modes: buck (charge battery), boost (discharge battery), and shut-down (SD). Considering traditional soft start would produce some problems to damage the device in double sources application of bi-directional converter, a new soft start control strategy, delay synchronous rectification control strategy is proposed for the bi-directional converter. Finally, a 500W prototype converter is built to verify the theoretical analysis and the control strategies.