Type UEL1 Circular Characteristic Underexcitation Limiter Model
Type UEL2C Underexcitation Limiter Model
As indicated previously, each of the under excitation limiters have a unique transfer function. The schematic diagram of each is given below.
For further details on background theory for these over excitation limiters, see IEEE Standard 421.5-2016.
Where,
| Description | Symbol | Type | Value | Units |
|
UEL center settinga |
KUC | A | 1.38 | pu |
|
UEL radius settinga |
KUR | A | 1.95 | pu |
|
|
VURmax | 5.8 | pu | |
|
|
VUCmax | 5.8 | pu | |
|
UEL excitation system stabilizer gain |
KUf | A | 3.3 | pu |
|
UEL integral gain |
TUI | A | 0 | pu/s |
|
UEL proportional gain |
KUL | A | 100 | pu |
|
UEL PI control maximum output |
VUImax | 18 | pu | |
|
UEL PI control minimum output |
VUImin | -18 | pu | |
|
UEL numerator (lead) time constant (first block) |
TU1 | A | 0 | s |
|
UEL denominator (lag) time constant (first block) |
TU2 | A | 0.05 | s |
|
UEL numerator (lead) time constant (second block) |
TU3 | A | 0 | s |
|
UEL denominator (lag) time constant (second block) |
TU4 | A | 0 | s |
|
UEL maximum output |
VUELmax | 18 | pu | |
|
UEL minimum output |
VUELmin | -18 | pu |
Notes:
Where,
| Description | Symbol | Type | Value | Units |
|
UEL real power filter time constant |
TUP | A | 5 | s |
|
UEL reactive power filter time constant |
TUQ | A | 0 | s |
|
UEL voltage filter time constant |
TUV | A | 5 | s |
|
UEL voltage bias |
Vbias | A | 1 | pu |
|
Voltage exponent for real power input to UEL table |
K1 | A | 2 | |
|
Voltage exponent for reactive power output of UEL table |
K2 | A | 2 | |
|
UEL excitation system stabilizer gain |
KUF | A | 0 | pu |
|
UEL reactive power reference time constant |
TQref | A | 0 | s |
|
UEL fixed gain reduction factor |
Kfix | A | 1 | pu |
|
UEL adjustable gain reduction time constant |
Tadj | A | 3 | s |
|
UEL logic switch for adjustable gain reduction |
SW1 | A | pos. A | |
|
UEL integral gain |
KUI | A | 0.5 | pu/s |
|
UEL proportional gain |
KUL | A | 0.8 | pu |
|
UEL PI control maximum output |
VUImax | 0.25 | pu | |
|
UEL PI control minimum output |
VUImin | 0 | pu | |
|
UEL numerator (lead) time constant (first block) |
TU1 | A | 0 | s |
|
UEL denominator (lag) time constant (first block) |
TU2 | A | 0 | s |
|
UEL numerator (lead) time constant (second block) |
TU3 | A | 0 | s |
|
UEL denominator (lag) time constant (second block) |
TU4 | A | 0 | s |
|
UEL maximum output |
VUELmax1 | A/E | 0.25 | pu |
|
UEL minimum output |
VUELmin1 | A/E | 0 | pu |
|
UEL maximum output |
VUELmax2 | A | 99 | pu |
|
UEL minimum output |
VUELmin2 | A | -99 | pu |
|
UEL lookup table real power (first point) |
P0 | A | 0 | pu |
|
UEL lookup table reactive power (first point) |
Q0 | A | -0.31 | pu |
|
UEL lookup table real power (second point) |
P1 | A | 0.30 | pu |
|
UEL lookup table reactive power (second point) |
Q1 | A | -0.31 | pu |
|
UEL lookup table real power (third point) |
P2 | A | 0.60 | pu |
|
UEL lookup table reactive power (third point) |
Q2 | A | -0.28 | pu |
|
UEL lookup table real power (fourth point) |
P3 | A | 0.90 | pu |
|
UEL lookup table reactive power (fourth point) |
Q3 | A | -0.21 | pu |
|
UEL lookup table real power (fifth point) |
P4 | A | 1.02 | pu |
|
UEL lookup table reactive power (fifth point) |
Q4 | A | 0 | pu |