[1] UNSW, Sch Elect Engn & Telecommun, Sydney, NSW 2052, Australia
[2] Tech Univ Denmark DTU, Dept Engn Technol, Energy Technol & Comp Sci Sect, DK-2750 Ballerup, Denmark
[3] Aalborg Univ, Dept AAU Energy, DK-9220 Aalborg, Denmark
[4] Cardiff Univ, Sch Engn, Cardiff CF24 3AA, Wales