Flexible Power Extraction in Photovoltaic Energy Systems Using Voltage Window Search Algorithm Under Partial Shading Conditions

Abstract

Flexible power point tracking (FPPT) is emerging alongside maximum power point tracking (MPPT) to adjust power output based on grid demand rather than solely maximizing it. This article presents an FPPT algorithm that operates effectively under partial shading conditions. By modifying the voltage window search MPPT algorithm and incorporating additional functionalities, the proposed approach operates on the left side of the power–voltage curve, offering improved robustness. A DC–DC buck–boost converter and a proportional–integral controller are implemented to achieve optimal performance. To ensure steady operation near the target power point, an oscillation detection mechanism is integrated, which stabilizes the power output once the flexible power point is reached and prevents unnecessary fluctuations. The proposed approach is validated on four irradiance patterns, one uniform and three partially shaded, under three distinct FPPT power criteria. The effectiveness of the algorithm is confirmed by experimental results, achieving the desired power output with an average tracking time of 1.54 s, an average power tracking variance of 0.224%, and validated across twelve experimental scenarios (four patterns under three FPPT power criteria), together with a loss analysis of the converter stage and an assessment of the computational cost of the algorithm, demonstrating its potential for grid-integrated photovoltaic applications.