Analytical vs. Numerical Analysis to Assess PV Distributed Generation Penetration Limits in LV Distribution Networks

摘要

Great interest is posed on the connection of micro photovoltaic (PV) distributed generation (DG) units to LV distribution networks. Since the presence of grid-connected PV DG units is expected to grow in the future, thanks to promotion measures recently introduced in the European Countries, it is necessary to investigate the various technical constraints that limit the maximum amount of power that DG units can inject into distribution feeders. In this perspective, the present work deals with the problem of assessing PV DG penetration limits related to voltage quality issues. Different network models have been developed by the Authors in previous works to accomplish this task. Then, in this paper, the aim is to compare analytical and numerical network models applied to estimate the penetration limits of PV DG given by voltage constraints on realistic LV distribution feeders. The numerical models have been developed on Simulink (Dynamic System Simulation for MATLAB) platform. Both analytical calculation and simulations have been applied to study typical LV three-phase distribution networks with different feeder sections and cable typology. The results, provided by the comparison between analytical and simulation method, are given in terms of per cent error between the PV DG penetration calculated by means of analytical expressions and the one calculated by means of numerical simulations. This comparison proved that the used analytical expressions very often imply acceptable errors, fully counterbalanced by the advantages of this approach in terms of clearness and simplicity of use in predicting DG penetration limits.