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Model reduction is a popular trend in large-scale system simulations. It is also an effective way to improve the efficiency of distribution system simulations. In this paper, the realization of state-space-based model reduction methods in EMTP-type programs is presented. The state-space model of linear time-invariant distribution network is reduced and simulated with the detailed nodal model in EMTP-type programs. The combined state-space nodal analysis algorithm is adopted as the interface between the state-space models and the nodal models. Simulations are performed to show the feasibility and validity of the proposed method, and the improvement in efficiency with the application of model reduction.

The ever-increasing scale of system interconnection and diverse dynamic time constants of power equipment pose challenges to power system electromagnetic transients simulation algorithm. In this paper, an advanced numerical integration method based on matrix exponential operator is proposed. Krylov subspace approximation is utilized to effectively reduce the problem dimension, and an accurate dense output formula is established to enable the method adopting larger simulation step size and revealing higher frequency dynamic details simultaneously. Accuracy, numerical stability and computation efficiency is demonstrated through numerical case studies.