A minimal realization approach to reduced-order modelling and modal analysis for power system response signals

The authors report on a numerical scheme for compressing in parametric form small signal electromechanical responses of multimachine power systems, originating from transient stability programs (TSPs) or actual field testing. The result is achieved by using a multi-input multi-output (MIMO) minimal realization algorithm based on singular value decomposition (SVD), which can explicitly take into account the critical impact of the input interactions. The resulting parametric model is a reduced order representation of the underlying complex system, yet it is optimal (in the least-squares sense). Besides compact storage of damping information, the balanced state-space realization as such retains the principal components of the response signals, and could thus be useful for the tuning of static volt-ampere reactive (VAr) systems (SVSs) and power system stabilizers (PSSs). When it is transformed in the modal space, the model also provides insight into modal interaction mechanisms. Several examples are included for illustration purposes and other applications and improvements are also discussed