[1] Natl & Tech Univ Athens, Sch Elect & Comp Engn, Athens 15780, Greece
[2] Tech Univ Denmark DTU, Dept Wind & Energy Syst, DK-2800 Lyngby, Denmark
[3] Natl Kapodistrian Univ Athens NKUA, Dept Informat & Telecommun, Athens 15784, Greece
[4] Hellenic Minist Environm & Energy, Athens 11526, Greece
[5] Swiss Fed Inst Technol, ETH Power Syst Lab, CH-8092 Zurich, Switzerland