Second order hydraulic turbine models for multimachine stability studies

An approximation of the exact hydraulic turbine transfer function which is particularly suitable for stability calculations in a multimachine power system is presented. This approximation is made with a second-order transfer function, the coefficients of which are estimated so that it resembles as closely as possible the dynamics of the actual hydraulic turbine in the frequency range of the electromechanical oscillations between the synchronous machines of the system. The method is applied to a realistic multimachine model of the Hellenic Interconnected System and the improvement in accuracy over the traditional first-order hydro turbine model is found to be significant