Small-Signal Stability Assessment of the Cameroonian Southern Interconnected Grid

Abstract— This article investigates the performance of the generator excitation loop equipped with a PID controlled AVR system, and of the dam automaton consisting of a PID controlled water flow regulation system in the southern interconnected grid (SIG) of the Cameroonian power system, when subjected to small perturbations, using linearized state-space models of the power plant. A fifth order model of the synchronous generator with a high gain excitation system and AVR is considered. A detailed formulation of equations comprising the mechanical and electrical swing dynamics of the turbine-generator unit and the load is realized; a multivariable state-space non linear model of the one area single machine system model is obtained. For small-signal performance analysis, the model is linearized around an operating point. The article also presents a state-space model of the water flow system. The effects of PID controlled AVR and water flow regulation systems are examined through performing of extensive MATLAB simulations to analyze the behavior of the proposed models following small disturbances. The simulation results presented in this paper are obtained using a MATLAB computer program developped by the authors; they provide useful insight into the dynamic behavior of the Cameroonian SIG, including stability, speed of response and steady-state accuracy. The paper establishes that the classical control systems do not have very good performance: long settling time, high overshoot, relativly slow response, and many damped oscillations.