Assessment of the Distributed Generation Hosting Capacity Incorporating Harmonic Distortion Limits

The amount of distributed generation (DG) the network can host depends on a number of parameters such as the characteristics of the generation units and their daily generation profiles, the characteristics of the network and its configuration, the hourly load profiles as well as national and regional grid code requirements. The high penetration of renewable energy sources (RES) in the distribution networks (DN), namely in medium voltage (MV) grids, may lead to reverse active power flows, to voltage rises and to an increase in voltage distortion due to the large use of power-electronic converters as generation interfaces with the grid, which may limit the hosting capacity (HC) of RES. This paper is intended to describe a new approach for identifying the HC for the integration of RES in electrical distribution systems. This is a planning tool based on the multi-period optimal power flow (MP-OPF) which aims to maximize the HC for DG under thermal and voltage constraints, involving also the verification of the harmonic voltage distortion via a set of current harmonic flow calculations, following a known current harmonic injection profile for each DG unit to be connected on grid. The case study shows that harmonic distortion limits may have substantial impacts on the allowable penetration of DG, for instance, due of the characteristics of DN and its configuration, the hourly load and generation profiles.