A Small-signal Sub-synchronous Oscillation Analysis Caused by SVC in Weak-link Power Grid

In several substations of the Central Tibet Linking Project, SVC is used to improve the voltage control features in weak-link power grid. According to electromagnetic transient simulation, improper control parameters of SVC may lead to a novel sub-synchronous oscillation in weak-link power grid. In this work, firstly, a linearized electromagnetic transient model of SVC and power grid is proposed. Secondly, using eigenvalue analysis, this novel sub-synchronous oscillation is proved to be caused by the resonance between SVC and power grids with long transmission lines. Improper control parameter of SVC will decrease damping of the grids’ leading mode. Thirdly, system with 2 SVCs is analyzed by proposed method, showing that multiple SVCs can make the system to be more unstable. Finally, several suggestions are given to suppress the oscillation caused by SVC.