1. Department of Electrical Energy Systems, Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany
2. Advanced Electrical Systems Research Group, Institute of Energy and Environment, University of Strathclyde, Glasgow, U.K.
3. Department of Electric Power Engineering, Norwegian University of Science and Technology, Trondheim, Norway
4. School of the Built Environment, Heriot-Watt University, Edinburgh, U.K.