Hybrid Cascaded Operation of Distribution Grids

Abstract:
Fighting the climate change is the main challenge of all parts of the energy supply sector in this age. In the recent decade the electrical energy sector was transformed by integrating a large number of renewable power plants which reduced the consumption of fossil resources in the generation of electrical energy substantially. Since these power plants are mostly decentralized and furthermore increasing numbers of electrical consumers (like EVs an heat pumps) connected to the grid, especially the lower voltage levels are temporarily reaching their transfer limits. Especially in urban areas grid reinforcement involves high expenditures. Therefore, power system experts agree that smart distribution systems are the way to handle these challenges in order to avoid expensive grid expansion. To realize smart distribution grids there are two principle solutions: The integration of the lower voltage levels into existing centralized grid control solutions or the installation of decentralized autonomous controllers. Since both mentioned solutions have different advantages and disadvantages, it is reasonable to combine them to a semi-autonomous controller with control system connection. The paper describes such a system, which one the one hand is able to control the grid without connection to the centralized control system, but on the other hand uses a communication connection in order to parameterize and update the grid data and for emergency control. This redundant structure guarantees a maximum availability and supply reliability.