State estimator design for solar battery charger

This paper describes state estimation technique for solar battery charger based on lithium battery. The lithium battery is used for storing solar generated power. The solar battery charger 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 will be presented. These estimated states can be used as second protection methods. The solar cell and battery modeling methods are presented in the first chapter and the state estimator design method will be presented in step by step sequence in the latter chapter, and the simulation and experimental result verifies the performance of the proposed system. 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.