Future response of distributed generation connected to low voltage networks during transmission network faults

摘要

The power system is traditionally composed of large centralized synchronous generators (SG) serving loads connected directly to the network. In recent years, the share of converter- coupled, small-scale distributed generation (DG) and new types of loads that are connected to the electrical network by power electronics increased significantly. While wind power used to be the dominant DG technology in Germany, the installed capacity of photovoltaic (PV) systems has reached the same magnitude as installed wind power capacity, i.e. around 32 GW at the end of 2012. About 80% of the PV capacity in Germany is connected to low voltage networks. Consequently, the response of low voltage networks with high penetration of PV systems to transmission network faults could influence the overall power system performance. While DG was required to disconnect in the past, when their share in total generation was still negligible, nowadays DG is to a large extent required to ride-through low voltages (LVRT capability). That does not hold for small-scale DG, and especially PV, connected to low voltage networks. Given the strong development of such PV, LVRT requirements for the LV network level become of increasing interest. However, specifications of such future requirements depend on the outcome of an in-depth analysis that considers both the power system needs and the technological implications for the DG. This article describes the scope and methodology of a new research project that aims at investigating the future robustness of current network fault requirements for LV connected DG and proposing (where necessary) revisions.