Impact of Transient Stability with Increasing Penetration of Distributed Energy Resources in HVDC Paralleled with 765kV AC Transmission Line

In this study, we analyze the impact of transient stability owing to a lack of voltage support when the penetration of distributed energy resources increases in a high voltage direct current paralleled with an ultra-high voltage transmission line. As penetration of the distributed energy resources increases, the load on the AC transmission line increases. When the 765kV AC transmission line trips, the AC bus voltage near the HVDC rectifier drops. The firing angle of the HVDC rectifier is less than the minimum value and is out of range. If firing angle control is no longer available, the active power flow of the HVDC is reduced, adversely affecting angle stability. Therefore, this study analyzes the impact on angle stability when the active power of the distributed energy resources increases, and demonstrates the effect of flexible AC transmission systems to solve this problem.