Decoupled state estimator design for stand-alone photovoltaic system

This paper describes decoupled state estimator design technique for stand-atone photovoltaic system. The main components of the systems are solar array, power converter and battery. The lithium batteries are widely used in the mobile and hybrid power traction system. The converter requires solar cell voltage and current, battery voltage and current for controlling solar cell and battery status. Due to the unstable hazardous behavior of the lithium battery, it is required to have double protection function in the solar battery charger. In this paper, the method to estimate the battery internal status such as SOC, terminal voltage and charging current using decoupled state estimator will be presented. These estimated states can be used as second protection methods. The merits of the proposed methods are simple structure with reduced sensors and it can guarantee the safe operation of the lithium battery with reinforced control functions.