A N4SID-Based Strategy to Estimate the Parameters of Disturbances in Power Systems

Abstract

A blind identification method based on Subspace State Space System IDentification (N4SID) is proposed to identify the parameters of disturbances, such as electromechanical modes and harmonics, in a power system. The challenge, however, is how to identify the disturbances without the knowledge of systems' inputs. The disturbances are only measured by Phasor Measurement Units (PMUs) in the power system as signals representing the system's outputs; the system's parameters and inputs have to be estimated only from the measured outputs. This leads to a blind identification problem; therefore, N4SID, categorized as blind identification, is employed to address the problem. To solve the problem, the output data is formulated in the N4SID terminology, system matrices are calculated in 6 steps, and finally, the forward stochastic model of the system is derived. The proposed method has some advantages such as robustness and no need to know the parameters of the power system for design. To evaluate the performance of the proposed method, simulation studies are carried out on two practical power systems. The simulations show that the proposed method has a desirable performance.