Maximum power point tracking and optimal Li-ion battery charging control for photovoltaic charging system

Due to the severity of the global energy crisis and environmental pollution, the photovoltaic (PV) system has become one kind of important renewable energy source. Solar energy has the advantages of maximum reserve, inexhaustibleness, and is free from geographical restrictions, thus making PV technology a popular research topic. This study is aimed at developing a PV charging system for Li-ion batteries by integrating Maximum Power Point Tracking (MPPT) and charging control for the battery. In order to enable the solar cell to use the sunlight effectively, a DC/DC boost converter for solar power generation was first designed, which used the MPPT Algorithm of Variable Step Size Incremental Conductance Method (INC) to enable the solar cell to track the MPPT at any time. The output from the DC/DC boost converter then entered the DC/DC buck converter to reduce the voltage for charging purposes. The charging system uses a constant voltage method to charge the Liion battery. The PI controller design Constant Voltage (CV) charging method uses a genetic algorithm to determine the optimal gain value. The numerical simulation showed that the PV charging system proposed by this study is easily realized, and can resist the disturbance of external environmental changes, and achieve fast charging. © 2012 Elsevier Ltd. All rights reserved.