Sensitivity Analysis of an Excitation System in Order to Simplify and Validate Dynamic Model Utilizing Plant Test Data

Electrical system dynamic modeling of associated components such as generators, turbines and other drivers, excitation systems, governors, and rotating loads requires countless engineering man-hours to determine the models´ necessary parameters. Therefore, any reduction or simplification of the component dynamic models that can be performed, while assuring statistically equivalent analyses results, will reduce man-hours and modeling process duration. This paper addresses generator excitation system models, which include complex Laplace transfer functions typically provided in IEEE Std 421.5-2005, along with their simplification and parameter reduction by utilizing a novel sensitivity analysis method; the method yields a simplified IEEE model. It further addresses the process for digitizing hard copy trace recorder plots of power plant field test data. This paper then addresses the tuning process for obtaining optimized exciter model parameters. Finally, the original and simplified exciter models are used to perform system dynamic analysis on a stand-alone 6.9-kV microgrid with five large sequentially started induction motors powered from a 7-MW diesel generator with an IEEE type AC5A excitation system. The results of the two dynamic analyses validate the entire process by comparison with the sequential motor start test results.