1. Department of Energy Management and Power System Operation, University of Kassel, Kassel, Germany
2. Department of Project Engineering, SMA Solar Technology AG, Niestetal, Germany
3. Department of Power System Control and Dynamics, Fraunhofer Institute for Energy Economics and Energy System Technology, Kassel, Germany
4. Department of Grid Operations and Planning, Modeling and Simulation, Electric Power Research Institute, Palo Alto, USA
5. Fund for Scientific Research, Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium