UEL1

IEEE UEL1 model

Context

This underexcitation limiter model first appeared in the IEEE Std 421.5-2016 [1].

Model use, assumptions, validity domain and limitations

This model is associated to one of the voltage regulators (types AC, DC, ST) defined by the IEEE Std 421.5-2016 [1].

The model provides an underexcitation limiter signal for the purpose of takeover : the underexcitation limiter signal acts as a lower limit on the voltage regulator main signal which then becomes the excitation voltage.

Model inputs and output

The input signals are :

Variable	Description	Unit
\(itPu\)	Complex stator current	\(pu\) (base \(SnRef\), \(UNom\))
\(utPu\)	Complex stator voltage	\(pu\) (base \(UNom\))
\(VfPu\)	Excitation system stabilizer signal	\(pu\)

The output signal is \(UUelPu\), the underexcitation limiter voltage in \(pu\) (base \(UNom\)).

Model parameters

Parameter	Description	Unit	Value
\(Kuc\)	UEL center setting	\(pu\)	\(1.38\)
\(Kuf\)	UEL excitation system stabilizer gain	\(pu\)	\(3.3\)
\(Kui\)	UEL integral gain	\(pu\)	\(0\)
\(Kul\)	UEL proportional gain	\(pu\)	\(100\)
\(Kur\)	UEL radius setting	\(pu\)	\(1.95\)
\(tU1\)	UEL first lead time constant	\(s\)	\(0\)
\(tU2\)	UEL first lag time constant	\(s\)	\(0.05\)
\(tU3\)	UEL second lead time constant	\(s\)	\(0\)
\(tU4\)	UEL second lag time constant	\(s\)	\(0\)
\(VUcMaxPu\)	UEL maximum voltage magnitude	\(pu\) (base \(UNom\))	\(5.8\)
\(VUiMaxPu\)	UEL maximum output	\(pu\) (base \(UNom\))	\(18\)
\(VUiMinPu\)	UEL minimum output	\(pu\) (base \(UNom\))	\(18\)
\(VUrMaxPu\)	UEL maximum radius	\(pu\) (base \(UNom\))	\(5.8\)

Model diagram

Figure 1: UEL1 model diagram

Open source implementations

This model has been successfully implemented in :

Software	URL	Language	Open-Source License	Last consulted date	Comments
Dynawo	Link	Modelica	MPL v2.0	09/10/2024

References

1.

Electrical TI of, Engineers E (2016) IEEE recommended practice for excitation system models for power system stability studies. IEEE Std 4215-2016