This paper competition is held by the CIGRÉ-U.S. National Committee to encourage students and early professionals to share their experience and knowledge with others in the industry. The competition has four stages, and Sun's paper made to the final stage. The top five technical papers will be presented in 10-minute windows at the Grid of the Future Symposium on Monday, October 29, 2018 to a panel of judges, and then one grand prize winner will be announced.

The title of Sun’s paper is “Sequential Tripping of Hybrid DC Circuit Breakers to Enhance the Fault Interruption Capability in Multi-Terminal DC Grids." The hybrid solid-state DC circuit breakers (DC CBs) have become one of the most promising technologies to address the protection challenges within multi-terminal DC (MTDC) grids. Those breakers are designed in such a way that a large number of identical modules are connected in series to enable extinguishing the fault current with the arresters embedded in them. Conventionally, these modules are commanded to trip simultaneously, creating significant overvoltage and overcurrent stresses for the rest of the system. 

To attenuate these stresses, in this paper, a sequential tripping method is proposed to improve the performance of hybrid DC CBs through commanding the main breakers to trip in a sequential manner. It has been verified that by the proposed method, fault clearance is expedited while the maximum overcurrent is reduced. To address the unbalanced energy absorptions among the different modules of the CB, a modified sequential tripping scheme is also proposed. By rescheduling the sequential tripping sequence, this method enables an equal redistribution of energy, which greatly reduces the risk of thermal overloading.

Sun joined ECE as a Ph.D. student in Fall 2015. His research interests include Multi-Terminal Direct Current (MTDC) system protection, modeling, and high-performance numerical simulation. In addition to Saeedifard, Sun’s coauthors on the paper are Ying Song, a visiting Ph.D. student from Xi’an Jiaotong University, and ECE Georgia Power Distinguished Professor A.P. Sakis Meliopoulos.