With the rapid development of the national inter-connected power grid

fast automatic excitation regulators and fast turbine governors are being widely used. In the current systems

some power plants adjust their responses for turbine governor systems to a very sensitive level to meet the primary frequency regulation assessment index

which actively brings about negative damping. Under these circumstances

the ultra-low frequency oscillation (ULFO) phenomenon emerged in hydro-dominant power systems. In order to solve the problem of ULFO

the hydro-turbine governor additional damper (GAD) based on phase compensation

which adapts to ULFO

is developed. The design of the control system is relatively simple. As a phase compensation based on the field testing and modeling of the turbine governor

GAD can provide the power system with positive damping

which contributes to the stability and security of the system. According to the impact of the mechanism of the turbine governor on the dynamic stability of the power system and the research of modeling and parametric testing

the proposed method not only supports positive damping

but also eliminates the negative damping of the speed governing system

which can significantly suppress the ultralow frequency oscillation and make it feasible to configure the GAD parameters according to field testing.