Underexcitation limiter models for power system stability studies

Underexcitation limiters are included in most modern voltage regulators applied on large synchronous generators. An underexcitation limiter (UEL) acts to boost excitation whenever it senses a condition in which generator excitation level is determined to be too low. New UEL models for inclusion in the next standard revision are provided and described. Methods of interfacing UEL models with standard excitation system models is also described.