[1] North China Elect Power Univ, Sch Elect & Elect Engn, State Key Lab Alternate Elect Power Syst Renewabl, Beijing 102206, Peoples R China
[2] Univ Oslo, Dept Informat, Oslo, Norway
[3] Simula Res Lab, Oslo, Norway
[4] Inst Telecomunicacoes, P-1049001 Aveiro, Portugal
[5] Univ South Wales, Pontypridd CF37 1DL, M Glam, Wales