Improving dynamic and transient stability of power system using Natural Logic controller; a modified Mamdani's fuzzy Controller

Abstract

This paper proposes the Natural Logic Controller, which is a simplified Mamdani's fuzzy controller. The special feature of NLC is applied to improve the stability of power system by improving its excitation and governing control feature. Usually fuzzy controllers are built with two classical signals of process i.e. error and its rate of change. In this proposed work we use a moderate number of fuzzy subsets and fuzzy rules. The main features of the NLC approach is that use the minimal fuzzy partition i.e. only two fuzzy subsets per variable and it use the minimal fuzzy rule base i.e. only two rules. The nonlinear resulting fuzzy controller is the simplest with an analytically well defined, input out put mapping and accepting a linear approximation at origin. The application of simplified characteristics of NLC in reducing the oscillation in internal angle 'δ' of generator is proposed. The stability of single machine to infinite bus system is studied for the faults in the beginning, middle and end of the transmission line. The performance of NLC for λ=0, λ=1 and PID controller in improving the stability of power system are compared. The performance of NLC is found much improved for the proposed control of power system stability.