1. Energy Research Institute, Nanyang Technological University, Singapore
2. Departament d’Enginyeria Electràonica, Elàectrica i Automaàtica, Universitat Rovira i Virgili, Tarragona, Spain
3. Department of Electrical, Electronic and Computer Engineering, University of Western Australia, Crawley, WA, Australia
4. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore