Determination of the Effect of Partial Shading on the PV Module Performance by Its Volt-Ampere Characteristic

An important objective pursued in the operation of photovoltaic modules is to reduce the influence of shading on the energy conversion efficiency. The majority of modern approaches used to solve the problem are based on the use of shunt diodes built in the module design. With such solution, it becomes possible to provide an alternative path of current flow between unshaded solar cells, thereby preventing their overheating. The article presents classification of the main faults of shunt diodes that are encountered. The article addresses an analysis of the volt-ampere characteristic type for different cases of 95 % shading of cells. The novelty of the study lies in the method for a comparative analysis of values corresponding to the points of maximum power and short-circuit current with the values of the control volt-ampere characteristic built without taking into account the shading in normal operation mode with applying the IV Swinger 2 software system. The response of a PV module to partial shading of its cells in the urban environment of the city of Chelyabinsk is considered. By using the obtained volt-ampere characteristics, the extent to which the generated power is reduced under different conditions can be traced. The shading of even one cell may reduce the efficiency by as much as 31 %. The study presented contributes to the discussion of matters concerned with optimizing the performance of PV modules and highlights the importance of using volt-ampere characteristics as the main tool to analyze the module operation efficiency. The study results help to get a better insight in how the shading affects the module performance and develop new solutions to ensure normal operation under different environmental conditions.