An improved discrete equivalent circuit model for power assessment of bifacial half-cell photovoltaic module under front shading

Abstract

Bifacial photovoltaic modules may operate under partial shading conditions, making the electrical characteristics assessment modeling particularly important. This study aimed to develop and validate an improved discrete equivalent circuit model for bifacial half-cell photovoltaic modules that explicitly accounts for non-uniform irradiance and temperature at half-cell element level. The detailed topological circuit of bifacial half-cell photovoltaic module was implemented in MATLAB/Simulink and bidirectionally coupled with the thermal field of each half-cell element obtained from finite-volume model, enabling dynamic thermal-electrical coupling simulation under front shading conditions. The model validation was conducted through outdoor experiments under different front shading ratios and patterns, and comparisons with conventional discrete equivalent circuit and average temperature models. The results show that average temperature and conventional discrete equivalent circuit models are more suitable for predicting electrical power under non-shading conditions and cannot accurately reflect the circuit reconstruction and nonlinear current-voltage features caused by partial shading. However, improved discrete equivalent circuit model accurately restores non-uniform irradiance and temperature distributions, captures the activation of bypass diodes and the associated multi-knees current-voltage behavior. The average relative error of power and root mean square error of current are less than 6.5% and 0.56 A, respectively, for different operating conditions. This study provides a half-cell element-based modeling approach for evaluating the electrical performance of bifacial half-cell photovoltaic module, offering guidance for module layout design, shaded operation, and accurate power output prediction of bifacial photovoltaic systems.