A STUDY ON ELECTROMECHANICAL MODE ESTIMATION OF POWER SYSTEM BY SUBSPACE IDENTIFICATION METHOD

Abstract

The thesis is focused around the study of electromechanical oscillations in the power system which are primarily responsible for instability in the power system. The analysis is carried out on two platforms – DigSILENT’s Power Factory and Matlab. In this thesis, popular Kundur’s two area system is considered for evaluation of system parameters, considering a three phase fault on the tie lines. Modal analysis of a system is gaining popularity in the analysis of system’s eigen values, that are interpolated to obtain modes present in the system. The two platforms involved are communicated via comma separated values (.csv) files. Power factory is used in this analysis of two area system. A two area model is implemented consisting of four generators and eleven bus system. Phasor simulation is executed on the model for the three phase fault, thus obtaining graphs of the simulation for tie-line power, rotors speed, and rotor angle with respect to time. Moreover the simulation is extended by taking modal analysis of the current system in operation. Modal properties of the system depicts the behaviour of the system oscillations, the system properties thus obtained shows the system under consideration is stable. Matlab utilizes the fact that the system under consideration is a linear discrete time system. It explores the concepts of linear algebra for the evaluation of system modal properties by subspace identification method. Matlab is used for study of the two area system undergoing a transient by Subspace identification (SSI) and Recursive adaptive subspace identification (RASSI) method. RASSI method is recursive method that is applied for the continuous monitoring of the system modal properties with the synchrophasor data. A comparison of these methods has been carried out in this work.