[1] Univ Aalborg, Inst Energy Technol, DK-9220 Aalborg, Denmark
[2] Univ Catania, Dept Elect Elect & Syst Engn, I-95125 Catania, Italy
[3] Delft Univ Technol, EWI Fac, Elect Power Proc Unit, NL-2628 CD Delft, Netherlands
[4] Virginia Polytech Inst & State Univ, Bradley Dept Elect & Comp Engn, Ctr Power Elect Syst, Blacksburg, VA 24061 USA