Your Course Instructor

Dr. Jian Sun
Professor, Department of ECSE
Rensselaer Polytechnic Institute
Troy, NY, USA

The course is taught by Dr. Jian Sun, Professor at Rensselaer Polytechnic Institute (RPI), USA. A pioneer and an international authority on the subject matter, Dr. Sun started his research in this area in 2002 when he was supported by Boeing to work on Boeing 787 electric power system. The use of variable-frequency power generation and distribution on this new more-electric aircraft necessitated the installation of many motor drives and other types of converters. While the generation is still by synchronous generators, the dominance of converter-based loads created concerns about new system stability problems. It was during that time when Dr. Sun developed the basic forms of his small-signal sequence immittance theory and harmonic linearization method.

In 2006, inspired by the development of solar and wind energy in Europe, Dr. Sun initiated a research program to extend the application of his theory to renewable energy and utility power systems. To test the theory, he also built a physical test-bed consisting of a grid simulator with programmable immittances and a number of what are now called converter-interfaced resources. These efforts led to the landmark paper published in 2011 that laid the foundation for immittance-based stability analysis of grid-connected converters. Subsequently, he led his research group to develop small-signal sequence immittance models for PV inverters, different types of wind turbines, and HVDC converters using modular multilevel converters (MMC) as well as classical line commutated converters (LCC). By hardware test and simulation, he also demonstrated the behavior of typical stability problems in different practical systems and the application of his methods to predict and solve those problems.

The new instability challenges that his methods were developed to address caught wide attention in 2014 when BorWin1, the world’s first offshore wind system with HVDC transmission, was shut down by a high-frequency resonance that caused fire in the offshore converter station. Dr. Sun served as a consultant to TenneT to guide the root cause analysis and solution development by applying his immittance modeling and analysis methods. Since then, he has also worked in a similar capacity with a number of other companies to solve real-world power system instability problems, including a) with China State Grid on onshore wind and HVDC system stability (2015-2016), and b) with Facebook on data center power system stability (2017-2020). Working directly on complex real-world problems provided unique opportunities to test the theory and created invaluable practical experiences that Dr. Sun will share throughout this course.

Since 2019, Dr. Sun’s research has focused on expanding the immittance-based frequency-domain methods to large power systems, including future converter-based ac and hybrid ac-dc grids. The papers he published on this subject in 2021-2022 expanded the theory he presented in the 2011 paper and laid a foundation for this more general application. He is currently working with two TSOs on applying these methods to large converter-based power systems. These new developments are covered towards the end of Part I in this course.

The materials presented in this course are developed mostly based on Dr. Sun own research and other professional activities, including first-hand experience of working with practical stability problems in renewable energy, HVDC transmission and critical power systems. He has presented parts of the materials in an early course as well as ~200 invited talks, seminars and tutorials in different countries and regions. The presentation in this course is most comprehensive and up-to-date.

Dr. Sun received his Dr. –Ing. Degree from University of Paderborn in Germany. He is a Fellow of IEEE and currently serves as the Vice President of Conferences of the IEEE Power Electronics Society. He received a number of awards for his research contributions, including the IEEE PELS Modeling and Control Technical Achievement Award (2013) as well as the R. David Middlebrook Achievement Award (2017).