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Description

This model is based on the ST4B excitation system in which is applied a low-pass filter to the terminal voltage transducer output, EC. This model is a variation of the Type ST3A model, with a proportional plus integral (PI) regulator block replacing the lag-lead regulator characteristic that was in the ST3A model. Both potential-and compound source rectifier excitation systems are modeled as shown in the figure below. The PI regulator blocks have nonwind up limits. The voltage regulator of this model is typically implemented digitally, so the model is identified with the suffix “B.”

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IEEE, "IEEE Recommended Practice for Excitation System Models for Power System Stability Studies," in IEEE Std 421.5-2016

The other features of the regulator are a low value gate for the OEL limit function, and the UEL and V/Hz control are summed into the input to the regulator. This means that on a unit with PSS control, the PSS will be active if the unit goes into UEL limit control, unlike some previous designs that had take-over type limiters. There is flexibility in the power component model to represent bus-fed exciters (KI and XL both equal to zero), compound static systems (XL = 0), and potential- and compound-source systems where XL is not zero. The appropriate PSS model to use with the ST4B excitation model is Type PSS2B.

Mask and Parameters

AVR Parameters

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

Exciter Parameters

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

Initial Values

Inputs, Outputs and Signals Available for Monitoring

Inputs

Outputs

References

[1] "IEEE Recommended Practice for Excitation System Models for Power System Stability Studies," in IEEE Std 421.5-2016 (Revision of IEEE Std 421.5-2005) , vol., no., pp.1-207, 26 Aug. 2016, doi: 10.1109/IEEESTD.2016.7553421.