An improved adaptable step-size P&O MPPT approach for standalone photovoltaic systems with battery station

Abstract

This study proposes and discusses a single-stage off-grid photovoltaic system to supply power to DC loads. A single-buck converter interfaces a solar photovoltaic array and DC load and ensures good operation of the maximum power point tracking (MPPT) and battery charge control, simultaneously. On the MPPT side, an improved adaptable step size perturb and observe (P&O) approach is suggested to reach the real maximum power point (MPP) of the solar photovoltaic array under varying weather conditions with reduced steady-state oscillation and less power loss. Furthermore, a three-stage charging controller (TSCC) is used on the battery charge control side to charge a lead-acid battery station. The MATLAB/Simulink environment tool is used for the implementation of the overall photovoltaic system. The simulation results under different scenarios of weather conditions prove the highest tracking performances of the improved approach over the conventional P&O method. In this respect, under abrupt weather conditions, the developed P&O approach can capture the MPP in a time of fewer than 2 ms, which is 10 times faster than the conventional P&O method. In addition, it can mitigate power losses and reduce oscillations around the MPP to half compared to the basic P&O method. Furthermore, the improved P&O approach with TSCC can significantly enhance the charging operation with good stability in the output power, voltage, and current of the battery station (BS).