Improved modelling of bypass diodes for photovoltaic applications

Abstract

Photovoltaic (PV) systems require bypass diodes to protect PV modules from operating at negative voltages, thus avoiding the degradation of a PV array under partial-shading conditions. However, the presence of bypass diodes produces changes in the power production of the PV array; thus, an accurate bypass diode model is essential to estimate the power production of the PV array, which is required to analyze the viability of a PV installation. Therefore, this paper proposes a modified model for the bypass diodes present in commercial PV arrays; such a proposed model is based on the Schottky equation, including a series resistance. This paper also proposes a non-invasive and non-destructive method for estimating the model parameters, which avoids the requirement of opening the module junction box; thus, it applies to commercial PV arrays. Simulation and experimental results confirm the improved accuracy of the proposed solution over the classical bypass diode model usually adopted for estimating the power production of PV arrays.

Keywords

• Bypass diode model
• Parameter estimation
• I-V curve