PV modules with increased shading tolerance due to modified interconnection designs

abstract

The shading tolerance of photovoltaic (PV) modules is an important issue when it comes to extending the areas for PV application. In this paper, we present three modified string interconnection designs (each with three parallel connections) without bypass diodes for the application with micro-inverters and compare them to a standard PV module with butterfly interconnection in terms of their shading tolerance. We expose the PV modules to four different exemplary shading scenarios (chimney, tree, another house, street lamp) both experimentally and in electrical circuit simulations to determine the power at the maximum power point (MPP). We validate the simulations based on the 2-diode model with experimental measurements under standard test conditions in a flash tester. The results show that the relative deviations between simulation and experiment lie between 1.3% and 5.7%. In all four shading scenarios, our Design C – with two times three parallel strings in series distributed over the module – performs best compared to the other two examined designs and the conventional butterfly PV module. The power at MPP of Design C is between 12.9% and 59% higher than that of the butterfly PV module under the four various shading scenarios. This demonstrates the high potential of modified interconnection designs in combination with micro-inverters for application of PV modules in areas prone to partial shading.