[1] Aalborg Univ, Dept Energy Technol, DK-9220 Aalborg, Denmark
[2] KTH Royal Inst Technol, Dept Elect Power & Energy Syst, Stockholm, Sweden
[3] Atlas Copco, Stockholm, Sweden
[4] KTH Royal Inst Technol, Dept Elect Energy Convers E2C, SE-10044 Stockholm, Sweden