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EXST3


Description

This model is a compound source controlled-rectifier excitation system based on the IEEE type ST3 excitation system model described in the 1981 IEEE committee report [1]. The EXST3 component was developed in line with the references [1] [2].

Mask and Parameters

AVR parameters

Expanding the "EXST3 diagram" displays the block diagram in the parameters window.



Name

Description

Unit

Parameter range

Tr


Regulator input filter time constant. This input filter is not part of the IEEE committee report and there are no typical values recommended in [1]. It was added for flexibility.

N.B. This parameter can be set to “0” if the filter is not used.

s

--

VImax

Maximum regulator input voltage

pu

--

VImin

Minimum regulator input voltage

pu

--

Tb

AVR lead-lag numerator time constant

s

--

Tc

AVR lead-lag denominator time constant

s

--

Ka

AVR filter gain

--

--

Ta

AVR filter time constant

s

--

VRmax

Maximum voltage regulator output

pu

--

VRmin

Minimum voltage regulator output

pu

--
KjVoltage regulator gain----

Exciter Parameters

Expanding the "Exciter diagram" displays the block diagram in the parameters window.

Name

Description

Unit

Parameter Range

EFDmax

Maximum exciter output voltage

pu

--

Kg

Feedback gain constant of the inner loop field regulator

-

--

VGmax

Maximum inner loop voltage feedback

pu

--

Kp

Potential circuit real part gain coefficient

-

--

Ki

Potential circuit imaginary part gain coefficient

-

--

Kc

Rectifier loading factor proportional to commutating reactance

-

--

Xl

Reactance associated with potential source

pu

--

ThetaP

Potential circuit phase angle

Degrees

--

Initial value tab


Name

Description

Unit

Variable = {Possible Values}

Ifd0

Synchronous machine field current initial value

pu

--

Efd0

Exciter output voltage initial value

pu

--


The parameters Ifd0 and Efd0 can be set manually, 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".

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

Inputs and Outputs and Additional Signals Available for Monitoring

Inputs

NameDescription

Unit

Voel*

Over-excitation limiter output

Input 

Vc1

Signal proportional to compensated terminal voltage (refer to the Load Compensator block documentation)

 If the Load Compensator block is not used upstream to the exciter block, then Vc1 is equal to Vt (main alternator terminal voltage)

Input 

Vuel*

Under-excitation limiter output

Input 

Vref

Voltage regulator reference voltage

Input 

Vs

Is defined as the output voltage of a Power System Stabilizer (PSS) [1].

Input 

Id

d-axis component of generator terminal current

Input 

Iq

q-axis component of generator terminal current

Input 

Vd

d-axis component of generator terminal voltage

Input 

Vq

q-axis component of generator terminal voltage

Input 

Ifd**

Synchronous machine field current

Input 

*Vuel and Voel are normally inputs to this excitation system but the user has the option to use a fixed constant value directly in the mask by choosing internal in the mask option.
**The observable field current Ifd from the synchronous machine in HYPERSIM needs to be multiplied in its current version by the machine’s Xad = Xd – Xl prior to its input to the exciter if a thermal machine or a hydraulic machine is used. This multiplication is not required if a pu standard or pu fundamental machine is used.

Outputs

NameDescription

Unit

Efd

Exciter output voltage

pu 

The terminal current calculation is performed in terms of Id and Iq using the following equation:

Similarly, the terminal voltage calculation is performed in terms of Vd and Vq using the following equation:

References

1.  I. C. Report, "Excitation System Models for Power System Stability Studies," in IEEE Transactions on Power Apparatus and Systems, vol. PAS-100, no. 2, pp. 494-509, Feb. 1981.

2. PSS®E 34.2.0 Model Library. NY, USA: Siemens Industry, Inc., 2017.

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