Comprehensive Approach of Estimating Power-Peaks of Partially Shaded PV Strings with Overlapping Bypass Diodes

A Photovoltaic (PV) modules with overlapping bypass diodes have different electrical characteristics under partial shading than in PV modules with non-overlapping bypass diodes. The performance analysis of PV modules with overlapping bypass diodes is complicated due to the existence of mutual PV cells that are connected with two bypass diodes. Under partial shading, the power-voltage (P-V) curve of the PV string has multiple power-peaks due to the exploitation of the bypass diodes. The locations of shaded parts have significant impacts on the maximum power that can be extracted from PV modules with overlapping bypass diodes, whereas the output power of a PV string with non-overlapping bypass didoes has not been affected by the location of shaded part. This paper develops a fast modeling approach of power peaks for partially shaded PV modules with overlapping by using LAMBERT function. Mathematical expressions for estimating power-peaks of PV string under various environmental conditions without the need to scan the entire P-V curve of the system are derived. The proposed power peaks estimation approach was verified using Matlab Simulink.