A fast battery charging algorithm for an intelligent PV system with capability of on-line temperature compensation

Abstract

This study presents a battery fast-charging mechanism for an intelligent generic photovoltaic (PV) system and also a pulse-charging method for the on-line temperature compensation. The fuzzy logic control (FLC) is adopted for fast maximum power point tracking (MPPT) of the PV system. Along with proposed battery charging algorithms, the controller presented in this study is named a fuzzy battery-managing controller (FBMC). The fast battery charging by this controller does not only prolong battery lifetime by restoring the maximum battery state of charge (SOC) in the shortest time but also with the temperature compensation. The designed charging algorithm consists of three different stages, namely constant current (CC), pulse charging and trickle charging. In the CC mode, the current at maximum power of the PV array is used for fast charging. The pulse charging mode is next adopted to contain temperature rise while maintaining relatively fast charging speed. To prevent battery damage by charging as battery capacity is close to its full status, 100 % SOC, the float charging mode is finally activated by further decreasing charging currents. Simulations are conducted via Powersim to validate the FBMC performance and the PV system model. The FBMC is next implemented by a DSP module (TMS320F2812) in order to adjust the switching duty cycle during operations of the buck converter. Finally, experimental results were compared with a general constant current and/or voltage method. The results show favorable performance of the propose charging method.