Hierarchical fuzzy controller applied to multi-input power system stabilizer

This paper proposes the application of a hierarchical fuzzy system (HFS) based on multi-input power system stabilizer (MPSS) in multi-machine environment. The number of rules increases exponentially with the number of variables in a standard fuzzy system. This problem is solved in the proposed HFS method. In this method, the total number of rules increases only linearly with the number of input variables. HFS consists of a number of low-dimensional fuzzy systems in a hierarchical form. In the MPSS, the deviation of reactive power ΔQ is added to a ΔP +Δω input type Power System Stabilizer (PSS) to have better performance. The performances of MPSS and the proposed method in damping inter-area mode of oscillation are observed in response to disturbances. It is found that the proposed PSS is performing satisfactorily within the whole range of disturbances. This comparative study is demonstrated through digital simulations.