UEL2C

Authors: Erwan Guichard (DPS for RTE)

Reviewers: Lampros Papangelis (CRESYM)

IEEE UEL2C model

Context

This underexcitation limiter model first appeared in the IEEE Std 421.5-2016 (of Electrical & Engineers, 2016).

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 (of Electrical & Engineers, 2016).

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
PGenPu Active power generated by the synchronous machine pu (base SnRef)
QGenPu Reactive power generated by the synchronous machine pu (base SnRef)
utPu Complex stator voltage pu (base UNom)
VFbPu Reference voltage from ST7C pu (base UNom)
VfPu Excitation system stabilizer signal pu

Both PGenPu and QGenPu follow the generator convention.

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

Model parameters

Parameter Description Unit Value
K1 Voltage exponent for active power input to UEL table - 2
K2 Voltage exponent for reactive power output of UEL table - 2
KFb UEL gain of reference voltage from ST7C pu -
KFix UEL fixed gain reduction factor pu 1
Kuf UEL excitation system stabilizer gain pu 0
Kui UEL integral gain pu 0.5
Kul UEL proportional gain pu 0.8
Sw1 UEL logic switch for adjustable gain reduction - true
tAdj UEL adjustable gain reduction time constant s 3
tQRef UEL reactive power reference time constant s 0
tU1 UEL first lead time constant s 0
tU2 UEL first lag time constant s 0
tU3 UEL second lead time constant s 0
tU4 UEL second lag time constant s 0
tUl UEL time constant of filter for reference voltage from ST7C s 0
tUP UEL active power filter time constant s 5
tUQ UEL reactive power filter time constant s 0
tUV UEL voltage filter time constant s 5
VBiasPu UEL voltage bias pu (base UNom) 1
VUel1MaxPu UEL maximum output pu (base UNom) 0.25
VUel1MinPu UEL minimum output pu (base UNom) 0
VUel2MaxPu UEL maximum output pu (base UNom) 99
VUel2MinPu UEL minimum output pu (base UNom) -99
VUiMaxPu UEL PI control maximum output pu (base UNom) 0.25
VUiMinPu UEL PI control minimum output pu (base UNom) 0
XqPu UEL characteristic reactance pu (base SnRef, UNom) -

The UEL lookup table is defined by 5 pairs (active power, reactive power) in pu, typically with the following values :

P Q
0 -0.31
0.3 -0.31
0.6 -0.28
0.9 -0.21
1.02 0

Model diagram

UEL2C

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. of Electrical, T. I., & Engineers, E. (2016). IEEE recommended practice for excitation system models for power system stability studies . IEEE Std 421.5-2016. https://home.engineering.iastate.edu/ jdm/ee554/IEEEstd421.5-2016RecPracExSysModsPwrSysStabStudies.pdf
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