As a five-year journey comes to an end, I would like to thank the people who made it easier to cope with.Firstly, my advisor Javier Uceda for his invaluable help and patience guiding me through this path until the end which without him this thesis would not be possible. "Ευ ζην"A special thanks is given to Airan Frances for his priceless help whenever was needed through all this time.Also, I would like to thank the people in DC systems, Energy conversion & Storage department at Delft University for the amazing time I had during my internship.The time through PhD would not be the same without its people, especially to Branislav, Diego, Guillermo, LiXin, Yann, Hesam, David, Vladan, LiCheng. Thank you for the memories and I hope we keep in touch.Finally, a tremendous gratitude to my family for supporting me in these 5 years path. I would like to thank my uncle Χάρης for his support in my weak moments and remind me why I started it in the first place. My parents Γιώργος, Αγάθη and my brother Πέτρος for being there and be understanding and giving me courage to continue. This thesis is dedicated to my mother who taught me that nothing is unreachable once we do the first step. "Ζην"