LAUSR

In a few of the isolated DC power-transmission systems with hydropower units (and the associated water hammer effect), inappropriate governor control parameters may weaken the system damping and stability. It has the potential to result in ultra-low-frequency oscillations (ULFO) which is below 0.1 Hz. To carry out this issue, a linearized state-space model of a multi-machine system that includes hydropower and steam turbine governor control systems is presented in this paper. The oscillation mode of ULFO about the damping characteristics of the governor control system is analyzed by the damping torque analysis method. A governor power system stabilizer (GPSS) design model predicated on phase compensation principle to heighten the damping of the governor control system to subdue ULFO is planned. To verify its effectiveness, the designed GPSS is applied to a single-machine system, a 4-machine 2-area system as well as the Yunnan power grid system of China. The simulation results demonstrate that GPSS effectively suppresses ULFO with heightened ULFO damping by the optimized settings of governor control parameters.