Subsynchronous oscillation damping characteristic analysis for hybrid HVDC based on VSC and CSC

VSC-HVDC is a noveltechnology based on voltage source converter, which is closely related with the rapid development of power electronics technology. Currently the studies about VSC-HVDC are mostly focused on the control strategy. There are few studies about the subsynchronous damping characteristic, especially about the impact analysis to the generator damping characteristic when CSC and VSC are connected on the same sending end. Firstly, this paper studies about the subsynchronous damping characteristic of VSC-HVDC under different control strategies and different power transmission level has been done base on complex torque coefficient method. Then a VSC-HVDC has been added to Gui-Guang II HVDC system in order to do the research about the subsynchronous damping characteristics of hybrid HVDC. The simulation results show that the hybrid HVDC has different influence about subsynchronous damping characteristic under different control strategies and different power transmission level and can significantly improve the traditional HVDC generator damping.