An underfrequency load shedding scheme with minimal knowledge of system parameters

Underfrequency load shedding (UFLS) is a common practice to protect a power system during large generation deficit. The adaptive UFLS schemes proposed in the literature have the drawbacks such as requirement of transmission of local frequency measurements to a central location and knowledge of system parameters, such as inertia constant H and load damping constant D. In this paper, a UFLS scheme that uses only the local frequency measurements is proposed. The proposed method does not require prior knowledge of H and D. The scheme is developed for power systems with and without spinning reserve. The proposed scheme requires frequency measurements free from the oscillations at the swing mode frequencies. Use of an elliptic low pass filter to remove these oscillations is proposed. The scheme is tested on a 2 generator system and the 10 generator New England system. Performance of the scheme with power system stabilizer is also studied.