Investigation of damage caused by partial shading of CuInxGa_(1-x)Se₂photovoltaic modules with bypass diodes

Abstract

This study evaluated the impact of partial shading on CuInxGa (1-x) Se 2 (CIGS) photovoltaic (PV) modules equipped with bypass diodes. When the CIGS PV modules were partially shaded, they were subjected to partial reverse bias, leading to the formation of hotspots and a possible occurrence of junction damage. In a module with a cadmium sulfide buffer layer, hotspots and wormlike defects were formed. The hotspots were formed as soon as the modules were shaded; the hotspots caused permanent damage (wormlike defects) in the CIGS module. Specifically, the wormlike defects were caused by the window layer, leading to increased recombination and decay of the solar cell properties. However, a CIGS module with a zinc sulfide buffer layer did not exhibit the formation of hotspots or any visual damage. The reverse bias breakdown voltage of the CIGS PV module with the cadmium sulfide buffer layer was higher than that of the CIGS PV module with the zinc sulfide buffer layer.

Performance Evaluation of Maximum Power Point Tracking Approaches and Photovoltaic Systems

“…A bypass diode starts functioning if 20% of the panel is shaded. When the shaded portion of a module exceeds 20%, the power loss is alleviated due to a huge current flowing through the bypass diode [92].…”

“…A bypass diode starts functioning if 20% of the panel is shaded. When the shaded portion of a module exceeds 20%, the power loss is alleviated due to a huge current flowing through the bypass diode [92]. When one cell is shaded, its bypass diode behaves as a load and allows current to flow through it from the rest of the cells, which maximizes the performance of the system [90].…”

“…By contrast, a shaded cell can be excluded by using a bypass diode to avoid impediment in power collection from the remaining cells, which results in energy loss from the shaded cell [69,93]. In thin-film CIGS, the bypass diode cannot protect the modules from damage [92]. The bypass diode in the panel produces multiple power peaks on the P-V curve.…”

An Emulated PV Source Based on an Unilluminated Solar Panel and DC Power Supply

“…The equivalent circuit of the constructed emulated PV source is shown in Figure 12, where I cs represents the current source current generated by the external dc power supply, D bp represents the bypass diode installed in the PV panel. The role the bypass diode is to avoid avalanche breakdown and hot spots during partial shading [4,31,32]. As partial shading was not investigated in the paper so the effect of the diode on the PV source was not considered.…”

“…To emulate a PV panel/array it is essential to have the measured electrical characteristics from the datasheet (such as their I-V curves and temperature effects), which can be prestored in look-up table of the control system of the PV simulator system with reference to [5,[30][31][32] or calculated in real time by using the I-V Equation (1) as discussed in [23,[33][34][35]. The circuit connection for the PV simulator can be seen in Figure 8.…”