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AC1A


Description

This model is based on IEEE Std. 412.5 type AC1A excitation system model (1). The AVR is composed of a leadlag compensator and a cascaded first order filter.

Mask and Parameters

AVR Parameters

AC1A AVR Parameters tab

*Vuel and Voel are the usual inputs for this excitation system (see Inputs, Outputs section below), but the user can choose to use a fixed constant value directly in the mask by choosing “internal” in the mask option.
Expanding the "AC1A diagram" displays the block diagram (expanded in AC1A AVR Block diagram) in the parameters window.


AC1A Block Diagram


NameDescriptionUnit
TrRegulator input filter time constant. This input filter is not part of the standard and there are no typical values recommended. It was added for flexibility.
s
TbAVR lead-lag numerator time constant
s
TcAVR lead-lag denominator time constant
s
KaAVE filter gain
-
TaAVR filter time constant
s
VamaxMaximum filter output
pu
VaminMinimum filter output
pu
VrmaxMaximum voltage regulator output
pu
VrminMinimum voltage regulator output
pu
KfExcitation control system stabilizer gain
-
TfExcitator control system stabilizer time constant
s

Exciter Parameters

AC1A Exciter Parameters Tab
Expanding the "Exciter diagram" displays the block diagram in the parameters window.


AC1A Exciter Block Diagram

NameDescriptionUnit
TeExciter time constant
s
KeExciter constant related to self-excited field
-
KdDemagnetizing factor
-
KcRectifier loading factor
-
Se1, Se2Exciter saturation factor at the corresponding Vex
pu
Ve1, Ve2Exciter voltage for the exciter saturation function
pu

Initial Values

AC1A Initial Values properties tab

NameDescriptionUnit
Ifd0Synchronous machine field current initial value
pu
Efd0Exciter output voltage initial value
pu

The parameters Ifd0 and Efd0 can be manually set by entering a numerical value. It can also be set automatically, based on load flow calculations, by entering a referenced synchronous machine variable.  For instance, if the name of the synchronous machine on which the excitation system is connected is “SM1”:

  • If a thermal machine or a hydraulic machine is used, Ifd0 shall be set as “=SM1.IfdInit” multiplied by the synchronous machine parameter Xad = Xd – Xl, and Efd0 shall be set as “=SM1.EfdInit”;
  • If a pu standard or pu fundamental machine is used, Ifd0 shall be set as “=SM1.IF_Init” and Efd0 shall be set as "=SM1.EFD_Init".

Inputs, Outputs and Signals Available for Monitoring

Inputs

NameDescriptionUnit
VoelOver-excitation limiter output*pu
Vc1Signal proportional to compensated terminal voltagepu
VuelUnder-excitation limiter output*pu
VrefVoltage regulator reference voltagepu
VsIs defined as the output voltage of a power system stabilizer (PSS)pu
IfdSynchronous machine field current*pu

*If a Synch. Machine (Hydraulic or Thermal) from the Network Machines and Generators library is used, the machine observable Ifd must be multiplied by the synchronous machine parameter Xad = Xd – Xl prior to its input to the exciter. This multiplication is not needed if a Synchronous Machine (pu Standard) or (pu Fundamental) is used.


The HYPERSIM® simulation option “Set Initial Conditions” must be checked for the automatic initialization to work properly.

Outputs

NameDescriptionUnit
 Efd Exciter output voltagepu

References

1. “IEEE Recommended Practice for Excitation System Models for Power System Models for
Power System Stability Studies,” IEEE Standard 421.5-2005.

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