UnderexcLimIEEE1: Type UEL1 model which has a circular limit boundary when plotted in terms of machine reactive power vs.
UnderexcLimIEEE2: Type UEL2 underexcitation limiter which has either a straight-line or multi-segment characteristic when plotted in terms of machine reactive power output vs.
UnderexcitationLimiterDynamics: Underexcitation limiter function block whose behaviour is described by reference to a standard model or by definition of a user-defined model.