Development of methods and models for assessing voltage stability in power systems with a high penetration of power generation from renewable sources

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Because of the politically decided revolution to change generation of electric power from fossil to renewable sources requirements for the secure operation of the power system will get intensified. Particularly, in Germany peaks of installed wind and photovoltaic capacities are reached. In prognoses of the German Federal Ministry for the Environment (BMU) around 50 GW of installed capacity each for wind and photovoltaics are expected. Thus, this installed capacity exeeds even the peak load, which is located in Germany in the range of around 80 GW. In addition, wind and photovoltaic power plants concentrate in areas with high-wind and high solar radiation. The result is that in the future centers of large power generation will emerge, if the weather is suitable. At the same time conventional fossil power plants, which are usually placed near load centers, will be replaced by renewable power generation. This results in a dramatic increase of power to be transported as well as distances between power generation and load and therefore in an increased system stress.Originally, the transmission system was built in order to transport reserve power between autonomous areas. With the expected future transport power and distances, voltage stability limits will be reached. Therefore, in addition to the thermal capacity limits of network components voltage stability limits may become the critical operating variable of power systems.The currently existing models and methods for assessing voltage stability are not suitable to represent and to evaluate the changing system with high penetration of renewable energies.The aim of the project is therefore to develop models and methods for assessing voltage stability in transmission system and distribution systems taking into account the evolving renewable generation structure.As renewable energies are mostly installed in distribution systems, one focus of this project is to develop a model of distribution systems with consideration of distributed power generation from renewable energy sources. At the Institute of Power Systems and Power Economics at RWTH Aachen University a model for the European transmission network and a market simulation to determine the optimal power plant dispatch has been developed. This will be used to get realistic network situations for future periods.The new models and methods of this project allow detailed analyses of the possible integration of renewable energies into the power system with consideration of different load and dispatch situations as well as different network structures including critical contingency situations of any network equipments.