Fast solution method for evaluation of long-term dynamic processes in power systems with provision for island operation

Abstract A fast, simple and efficient solution method for evaluation of long-term dynamic processes in power systems with provision for island operation is proposed. The original systems of nonlinear differential equations that describe the dynamics of hydro and steam power plants, for a relatively large time step (1–2 s), are transformed into very simple decoupled difference (algebraic) equations, using linearization, decomposition, diagonalization and Cauchy's formula. This secures a fast, efficient and stable numerical integration process with low memory requirements. The differential equation, used for the evaluation of the dynamics of the uniform frequency change, is also transformed in an appropriate manner, while the resultant difference equation is further incorporated into the model of the electrical network. The full model formed in this way is simultaneously solved iteratively, using a specially developed fast decoupled procedure, which has very good and reliable convergence characteristics. The validity of the procedure developed is tested on analyses of the dynamic behavior of the Yugoslav power system, for the case of large multiple disturbances which lead to the interruption of the parallel operation with UCPTE.