Comparative Analysis of Controllers for Power System Dynamic Stability Improvement

A modern power system network is an interconnection of generating stations, long transmission lines, and distribution network loads. Interconnected power system networks face various challenges of instability. The presence of a dynamic disturbance in the power system network causes the problem of power system dynamic instability. Changes in the load, the use of high gain exciters, the use of high voltage direct current converters with negative damping, and the connection of poorly tuned generator excitations are examples of small-signal disturbances that disrupt a power system. The presence of a small-signal perturbation causes a constant increase or decrease in the alternator rotor speed, as well as an increase in the amplitude of the rotor oscillation. In this paper, these challenges were addressed by using suitable controllers to improve the synchronizing and damping torque of the system. The dynamic instability of the power system using a fuzzy logic controller (FLC) and STATCOM was investigated through simulation, individually and in comparison. The required data for simulation purposes was obtained from the IEEE 9 bus test system. The application of FLC is studied through simulation using the systems model with its linear simplified equations using MATLAB Simulink. The input parameters of the FLC used to enhance the power system dynamic instability are speed deviation and rate of change of speed of the synchronous alternator. The change of speed, rotor angle, and electrical torque deviation response versus time of full and 25% input mechanical power change was obtained. The simulation results show that the oscillation of the rotor angle and amplitude response of the system with the FLC is damped at 0.2s with an amplitude of 0.5 p.u, but the oscillation of the rotor angle and amplitude response of the proposed system with STATCOM is damped at 3.5s with an amplitude of 0.8 p.u. As a result, the proposed power system with FLC provides good damping of local mode oscillation, low overshoot and settling time response as compared to STATCOM.