Simulation accuracy of the built-in PSCAD and an owner-defined synchronous machine model

Artikel i vetenskaplig tidskrift, 2010

Purpose - The purpose of this paper is to investigate the influence of time steps, integration methods, and saturation modeling on the accuracy of the synchronous machine model. This model is compared with the PSCAD built-in synchronous machine model in order to compare the accuracy of one of the most used synchronous machine models in a commercially available software versus a well-documented and widely accepted state-space synchronous machine model. Design/methodology/approach - In the paper, a synchronous condenser with the saturation phenomenon is modeled using state-space equations in the rotating dq-reference frame and is implemented both in Matlab/Simulink and PSCAD. Integration methods of up to the fifth order are implemented for increased accuracy. The saturation modeling includes modeling of the saturation in both d- and q-axis. A steady-state and dynamic performance comparison towards the built-in PSCAD synchronous machine model is performed. The saturation modeling does not include the saturation of the leakage fluxes. Findings - When the forward Euler method is used, in order to obtain less than 5 percent error, the time step should not exceed 5 its. The third-order Runge-Kutta method is the preferred choice and it provides desired accuracy when the time step is equal or smaller than 1,000 its. The built-in PSCAD model satisfies the error criteria for time steps smaller than 300 its. A small discrepancy of 2 percent is found during the steady-state test. Originality/value - The paper presents the performance of the higher order integration methods in an EMTP-type software environment where the trapezoidal integration method is most often used. It provides a good guide for building an owner-defined model. A comparison of a dynamic performance between the publicly documented state-space and a synchronous machine models commonly used for power system transient studies is presented.