Active Distribution Networks Implications on Transmission System Stability

Renewable power generation sources are imposing new operational challenges for power systems around the world. The traditional passive operating conditions may change since the power flow can reverse its direction under certain conditions. When the penetration of distributed generation is low, the effects comprise only distribution system. On the other hand, high distributed generation penetration may harm the whole system. In this sense, the connection of these sources can cause a considerable impact on operation and planning of transmission and distribution systems. This paper focuses on the implications on transmission systems when active distribution networks are considered. Dynamic studies are performed to assess the effects in transmission systems of renewable power generation connected to the distribution systems, considering different models and several operating scenarios. The consequences of applying complete and equivalent models are also investigated. The analysis and approaches presented here demonstrate the active distribution networks may influence transmission system behavior and also support that choosing the adequate model to represent the system is essential according to the kind of investigation someone is performing.