[1] Univ Strathclyde, Inst Energy & Environm, Dept Elect & Elect Engn, Glasgow G1 1RD, Lanark, Scotland
[2] Northumbria Univ, Fac Engn & Environm, Dept Phys & Elect Engn, Newcastle Upon Tyne NE1 8ST, Tyne & Wear, England
[3] Siemens Plc, Renewable Energy Div, Keele ST5 5NP, Staffs, England
[4] Aston Univ, Sch Engn & Appl Sci, Birmingham B4 7ET, W Midlands, England