With a deep sense of gratitude, I wish to express my sincere thanks to my supervisor, Associate Professor So Ping Lam, for his continuous insight, enthusiasm and encouragement. His deep passion for various scientific problems has taught me a lot. His guidance during the development of my research has been invaluable. I would also like to thank Associate Professor Erry Gunawan, Associate Professor Guan Yong Liang and Associate Professor Chen Shun. Their professional attitudes, continuous support and management skills deserve special acknowledgment. I also wish to thank Professor Choi San Shing and Professor Lalit Goel for their care for me which gives a lot of help to reach my goal at Power Engineering Division. I am grateful to Nanyang Technological University for providing me an opportunity to pursue my graduate study with research scholarship. I sincerely thank and highly value the support given by the