Modelling Renewable Energy Sources for Harmonic Assessments in DIgSILENT PowerFactory: Comparison of Different Approaches

With the increasing number of Renewable Energy Sources connected to the power grid, the impact on system operation is becoming more evident. To assess this impact, accurate computer models are required for both the power system and the devices connected to it. Various types of system integration studies need to be performed in order to study both steady-state and abnormal operation. Among the steady-state analyses, power quality studies assess the impact of Renewable Energy Sources on parameters such as voltage levels and harmonic content. Harmonic studies are gaining more attention because of the nature of renewable energy sources which are mainly connected to the power grid through electronic power converters, thus producing undesirable harmonics. This paper analyses various settings, solvers and harmonic source models in a commercial software – DIgSILENT PowerFactory – to ensure accurate calculation and correct interpretation of harmonic assessment. A simple model comprising seven harmonic devices is used for the analysis of various case studies. Their results are then compared with the standard IEC model and recommendations are proposed on how to appropriately model the RESs depending on the specific application considered