Determination of reduced order model for torsional interaction investigations using selective modal analysis – Part I: Initial approach

► The application of selective modal analysis (SMA) for torsional interaction investigations is proposed. ► Preserving the significant dynamics the SMA gives a reduced order model. ► SMA algorithm is verified based on linearised model of the IEEE first benchmark model. ► In companion paper, the enhancements on the truncation approach and its application is presented. This paper presents a new methodology for the determination of reduced order model in torsional interaction investigations. The conventional methods, even though give fast results for the model reduction, the physical meaning of the system is generally lost in the process. The proposed method, based on selective modal analysis (SMA), overcomes the drawbacks of the conventional methods for the determination of reduced order model (ROM). The selective modal analysis gives a reduced order model for subsynchronous resonance analysis preserving the significant dynamics. The formulation is illustrated on linearised model of IEEE first benchmark model (FBM). The companion paper explores the enhancements on the proposed algorithm and its applications to large practical power system.