1. Department of Energy Management and Operation of Electrical Networks, University of Kassel, Wilhelmshöher Allee 71-73, 34121 Kassel, Germany
2. SMA Solar Technology AG, Sonnenallee 1, 34266 Niestetal, Germany
3. Fraunhofer Institute for Energy Economics and Energy System Technology, Joseph-Beuys-Straße 8, 34117 Kassel, Germany