Dynamic Behavior of Active Distribution Networks

Abstract

Due to the increasing penetration of renewable energy sources, which are mainly connected to the distribution grid level, the active and reactive power flows in the distribution grids become more volatile. To avoid costly grid expansions Distribution System Operator uses voltage controlling components, such as on-load tap changing transformers or reactive power controls of grid users connected via inverters to the distribution network, to maintain the given voltage limits. These developments change the dynamic behavior of distribution networks, which affects also the voltage stability in the overlying transmission grid. Therefore, this paper investigates how different reactive power controls of renewable energy sources and sector-coupling consumers as well as different delay times of on-load tap changing transformers affect the dynamic reactive and active power demand and the dynamic voltage response of active distribution networks. For this purpose, dynamic simulations of a representative medium and low voltage network are carried out, which take into account volatile feed-in/demand-profiles for RES and consumers. The resulting vertical reactive and active power flows are discussed within this paper.