Grahame Holmes

RMIT University



Power Electronic Converters and the Emerging Smart Grid



For most of the 20th century, electrical energy has been generated by high power rotating generators that supply customers through a network of high voltage transmission lines and lower voltage distribution feeders. However, as the world moves inexorably towards Distributed Generation of renewable electrical energy, present day power system technologies are finding it harder and harder to meet the requirements of this new paradigm. Their fundamental limitations are clear - conventional generation assumes the availability of large scale stored energy for a small number of large generators, and energy is always assumed to flow unidirectionally from generators to consumers. Neither construct matches well with Smart Grid concepts, and alternative operating approaches are clearly required!

One foundational technology of Distributed Generation is the Power Electronic Converter, which can rapidly and flexibly control electrical energy almost instantaneously on a moment by moment basis. Since the 1950's, PE converters have become mainstream technology for industry, accurately controlling rotating machines, precisely processing energy with minimum energy wastage, and supporting a myriad of other applications. More recently, as their power handling capacity continues to increase, they are becoming very attractive for distributed generation systems where they can manipulate electrical energy in ways that simply cannot be done using rotating machines. The challenge at present is to decide exactly what we want to do with this capability.

This presentation will explore why power electronic converters are so flexible and attractive for Distributed Generation systems. It will firstly reflect on how the fundamental properties of these systems make them so versatile, and then will proceed to show how these properties particularly suit Distributed Generation needs and requirements. Finally, the current challenges of large scale usage of power electronic converters in electrical grid systems will be considered, looking at both technical challenges that are still to be overcome, and the operational control challenges that are still in the early stages of development.



Professor Holmes graduated from the University of Melbourne with a B. Eng. in 1974. He has a Masters degree from the same university in power systems engineering, and a PhD from Monash University in power converter modulation theory. He was a faculty member at Monash University for 26 years, where he established the Power Electronics Research Group in 1996 to support graduate students and research engineers working together on both pure and applied R&D projects. The interests of the group include fundamental modulation theory, VSI current regulators, active filter systems, resonant converters, current source inverters, and multilevel converters. In 2002 he formed a commercial R&D company from this group, specialising in the development of tailored power electronic conversion systems for unusual applications. In 2010, Professor Holmes was appointed as Innovation Professor - Smart Energy Systems at RMIT University, where he is currently extending his research interests to work with industry and government in the area of Smart Grids and Smart Energy technologies.

Professor Holmes has been a major contributor to the field of power electronics research for nearly 30 years. His primary research focus has been to investigate fundamental questions concerning the principles of modulation and closed loop control of switching power converters. He has published a major theoretical reference book on this subject, together with over 250 refereed journal and conference articles (11000+ citations). He is a Fellow of the IEEE, reviews papers for all major IEEE transactions in his area, and has been an active member of the Industrial Applications, Power Electronics Societies of the IEEE for over 25 years.