Field and Simulation-Based Assessment of Inverter Loading, MPPT Operation, Clipping Losses, and Internal Air Temperature in Two Grid-Connected Photovoltaic Plants

Abstract

This work presents a critical, technical and scientific analysis of two operational photovoltaic systems (PV) using field monitoring data, project-document analysis, manufacturer specifications, and PVsyst simulations. One of the objectives was to determine whether the analysed plants may require corrective actions or future retrofitting. The study identified scaleless dimensions and direction, diagrams that do not match the installed equipment and design decisions aimed solely to reduce the cost of electrical cables. A simulation with the projection of losses and energy generation was necessary to define an action plan for preventive or corrective maintenance. The main scientific contribution is the combined assessment of measured operating variables and simulation results for two plants with different inverter technologies and DC/AC sizing ratios. Since free online PV system simulators are available, all projects should be accompanied by estimated values of all their state variables. The design engineer must be aware of the limitations of the simulator, such as the inability to accurately simulate strings with different numbers of modules according to the complexity of the PV installation. For the 325 kWp plant, the simulated inverter loss above nominal power was 6.7%, while the measured MPPT voltage differences exceeded the manufacturer-recommended value for some operating groups. The results highlight the practical importance of detailed system simulation, accurate project documentation, manufacturer-compliant string configuration, and access to operational monitoring data for maintenance planning and performance assessment.