SCL2C
Reviewers: Lampros Papangelis (CRESYM)
IEEE SCL2C model
Context
This stator current 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 two stator current limiter signals (one for overexcitation, the other for under excitation) for the purposes of :
- takeover : the stator current limiter signals act as upper and lower limits (respectively) on the voltage regulator main signal which then becomes the excitation voltage ;
- summation : the stator current limiter signals are added to the stator voltage deviation from the reference, thus being taken into account in the calculation of the excitation voltage.
Model inputs and outputs
The input signals are :
Variable | Description | Unit |
---|---|---|
itPu | Complex stator current | pu (base SnRef, UNom) |
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) |
Both PGenPu and QGenPu follow the generator convention.
The output signals are :
Variable | Description | Unit |
---|---|---|
USclOelPu | Stator current overexcitation limitation output voltage | pu (base UNom) |
USclUelPu | Stator current underexcitation limitation output voltage | pu (base UNom) |
Model parameters
Parameter | Description | Unit | Value (set 1) | Value (set 2) | Value (set 3) |
---|---|---|---|---|---|
C1 | SCL exponent for calculation of first error | - | 0 | 0 | 0 |
C2 | SCL exponent for calculation of second error | - | 2 | 2 | 2 |
FixedRd | SCL fixed cooling-down time output | pu | -0.001 | -0.001 | -0.001 |
FixedRu | SCL fixed delay time output | pu | 0 | 0 | 0 |
IInstPu | SCL instantaneous stator current limit | pu (base SnRef, UNom) | 5 | 5 | 5 |
IInstUelPu | Underexcited region instantaneous stator current limit | pu (base SnRef, UNom) | 1.1 | 1.1 | 1.1 |
ILimPu | SCL thermal stator current limit | pu (base SnRef, UNom) | 1.1 | 1.1 | 1.1 |
IqOelMinPu | SCL OEL minimum reactive current reference value | pu (base SnRef, UNom) | 0.02 | 0.02 | 0.02 |
IqUelMaxPu | SCL UEL maximum reactive current reference value | pu (base SnRef, UNom) | -0.02 | -0.02 | -0.02 |
IResetPu | SCL reset-reference, if inactive | pu (base SnRef, UNom) | 100 | 100 | 100 |
ITfPu | SCL thermal reference for inverse time calculations | pu (base SnRef, UNom) | 1.1 | 1.1 | 1.1 |
IThOffPu | SCL reset threshold value | pu (base SnRef, UNom) | 0.05 | 0.05 | 0.05 |
K1 | SCL gain for calculation of first error | pu | 0 | 0 | 0 |
K2 | SCL gain for calculation of second error | pu | 0.0333 | 0.0333 | 0.0333 |
KdOel | Overexcited PID regulator differential gain | pu | 0 | 0 | 0 |
KdUel | Underexcited PID regulator differential gain | pu | 0 | 0 | 0 |
KFb | SCL timer feedback gain | pu | 0 | 0 | 0 |
KiOel | Overexcited PID regulator integral gain | pu | 0 | 0 | 1 |
KiUel | Underexcited PID regulator integral gain | pu | 0 | 0 | 1 |
KpOel | Overexcited PID regulator proportional gain | pu | 0.5 | 250 | 0.3 |
KPRef | SCL reference scaling factor based on active current | pu | 0 | 0 | 0 |
KpUel | Underexcited PID regulator proportional gain | pu | 0.5 | 250 | 0.3 |
KIpOel | Overexcited active current scaling factor | pu | 1 | 1 | 1 |
KIpUel | Underexcited active current scaling factor | pu | 1 | 1 | 1 |
KIqOel | Overexcited reactive current scaling factor | pu | 1 | 1 | 1 |
KIqUel | Underexcited reactive current scaling factor | pu | 1 | 1 | 1 |
Krd | SCL reference ramp-down rate | pu/s (base SnRef, UNom) | -1000 | -1000 | -1000 |
Kru | SCL reference ramp-up rate | pu/s (base SnRef, UNom) | 1000 | 1000 | 1000 |
Kzru | SCL thermal reference release threshold | pu | 0.99 | 0.99 | 0.99 |
Sw1 | OEL reference ramp logic selection | - | false | false | false |
tAScl | SCL reference filter time constant | s | 0.04 | 0.04 | 0.04 |
tB1Oel | Overexcited regulator lag time constant 1 | s | 0.1 | 12.5 | 0.1 |
tB1Uel | Underexcited regulator lag time constant 1 | s | 0.1 | 12.5 | 0.1 |
tB2Oel | Overexcited regulator lag time constant 2 | s | 0.1 | 0.1 | 0.1 |
tB2Uel | Underexcited regulator lag time constant 2 | s | 0.1 | 0.1 | 0.1 |
tC1Oel | Overexcited regulator lead time constant 1 | s | 0.1 | 1.5 | 0.1 |
tC1Uel | Underexcited regulator lead time constant 1 | s | 0.1 | 1.5 | 0.1 |
tC2Oel | Overexcited regulator lead time constant 2 | s | 0.1 | 0.1 | 0.1 |
tC2Uel | Underexcited regulator lead time constant 2 | s | 0.1 | 0.1 | 0.1 |
tDOel | Overexcited PID regulator differential time constant | s | 0.1 | 0.1 | 0.1 |
tDUel | Underexcited PID regulator differential time constant | s | 0.1 | 0.1 | 0.1 |
tEnOel | Overexcited activation delay time | s | 0.01 | 0.01 | 0.01 |
tEnUel | Underexcited activation delay time | s | 0 | 0 | 0 |
tIpOel | Overexcited active current time constant | s | 0.01 | 0.01 | 0.01 |
tIpUel | Underexcited active current time constant | s | 0.01 | 0.01 | 0.01 |
tIqOel | Overexcited reactive current time constant | s | 0.01 | 0.01 | 0.01 |
tIqUel | Underexcited reactive current time constant | s | 0.01 | 0.01 | 0.01 |
tItScl | Stator current transducer time constant | s | 0.01 | 0.01 | 0.01 |
tMax | SCL timer maximum level | s | 1 | 1 | 1 |
tMin | SCL timer minimum level | s | 0 | 0 | 0 |
tOff | SCL reset delay time | s | 5 | 5 | 5 |
tScl | SCL timer reference | s | 1 | 1 | 1 |
tVtScl | Terminal voltage transducer time constant | s | 0.01 | 0.01 | 0.01 |
VInvMaxPu | SCL maximum inverse time output | pu | 100 | 100 | 100 |
VInvMinPu | SCL minimum inverse time output | pu | 0 | 0 | 0 |
VOel1MaxPu | Maximum OEL output limit | pu (base UNom) | 10 | 10 | 0 |
VOel1MinPu | Minimum OEL output limit | pu (base UNom) | -10 | -8.7 | -0.1 |
VOel2MaxPu | Maximum OEL lead-lag 1 output limit | pu (base UNom) | 100 | 20 | 0 |
VOel2MinPu | Minimum OEL lead-lag 1 output limit | pu (base UNom) | -100 | -20 | -0.1 |
VOel3MaxPu | Maximum OEL PID output limit | pu (base UNom) | 100 | 100 | 0 |
VOel3MinPu | Minimum OEL PID output limit | pu (base UNom) | -100 | -100 | -0.1 |
VtMinPu | SCL OEL minimum voltage reference value | pu (base UNom) | 0.9 | 0.9 | 0.9 |
VtResetPu | SCL OEL voltage reset value | pu (base UNom) | 0.8 | 0.8 | 0.8 |
VUel1MaxPu | Maximum UEL output limit | pu (base UNom) | 10 | 10 | 0.1 |
VUel1MinPu | Minimum UEL output limit | pu (base UNom) | -10 | -8.7 | 0 |
VUel2MaxPu | Maximum UEL lead-lag 1 output limit | pu (base UNom) | 100 | 100 | 0.1 |
VUel2MinPu | Minimum UEL lead-lag 1 output limit | pu (base UNom) | -100 | -100 | 0 |
VUel3MaxPu | Maximum UEL PID output limit | pu (base UNom) | 100 | 100 | 0.1 |
VUel3MinPu | Minimum UEL PID output limit | pu (base UNom) | -100 | -100 | 0 |
The parameter sets correspond to a stator current limitation output :
- 1 : with a takeover action at the AVR input;
- 2 : with a takeover action at the AVR output;
- 3 : added to the summation point in the AVR.
Model diagram
The SCL reference current is calculated with the following model :
The SCL OEL activation logic has four inputs (on the left, from top to bottom, IOelActPu, tErr, IRefPu, at the top right corner, VtFiltPu) and one output (IOelBiasPu) calculated as follows :
if (VtFiltPu > VtMinPu and (tErr <= 0 or (IOelActPu > IOelRefPu for a duration >= tEnOel))) or tEnOel == 0
IOelBiasPu = 0
elseif (IOelRefPu == IInstPu and (IOelRefPu > IOelActPu + IThOffPu for a duration > tOff)) or VtFiltPu < VtResetPu
IOelBiasPu = IResetPu
else
IOelBiasPu = 0
The SCL UEL activation logic has three inputs (from top to bottom, IUelActPu, tErr, IUelRefPu) and one output (IUelBiasPu) calculated as follows :
if tErr <= 0 or (IUelActPu > IUelRefPu for a duration >= tEnUel) or tEnUel == 0
IUelBiasPu = 0
elseif IRefPu == IInstUelPu and (IUelRefPu > IUelActPu + IThOffPu for a duration > tOff)
IUelBiasPu = IResetPu
else
IUelBiasPu = 0
The SCL reference logic has two inputs (from top to bottom, IPRefPu, I’RefPu) and one output (IRefPu) calculated as follows :
if KPRef > 0 and abs(I'RefPu) > abs(IPRefPu)
IRefPu = sqrt(I'RefPu ^ 2 - IPRefPu ^ 2)
else
IRefPu = I'RefPu
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
- 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