An Online Load Modeling Approach for Small Signal Stability Analysis

Abstract

Due to inaccuracyof load modeling caused by time variation, the result of on-line small signal stability analysis is inaccurate. In order to solve above problem, a load modeling method based on subspace method suitable for on-line small signal stability is proposed in this paper. Firstly, always existing ambient signal is selected as identification signal and state space model of load is identified with subspace method. On-line load modeling is accomplished to solve the inaccuracy problem caused by load timevariation. Since the state space model is not unique, an unknown linear transformation exists between state space load model identified with subspace method and real state space model of load. It is proved that the unknown linear transformation has no influence on the result of small signal stability evaluation. Simulation result demonstrates correctness of the proposed method.