Discrete-time or continuous-time single input PSS1A power system stabilizer

**Library:**Simscape / Electrical / Control / SM Control

The SM PSS1A block implements a single-input PSS1A power system stabilizer
(PSS) that maintains rotor angle stability in a synchronous machine (SM) in conformance
with IEEE 421.5-2016^{[1]}.
Typically, you use a PSS to enhance the damping of power system oscillations through
excitation control.

You can switch between continuous and discrete implementations of the block by using the
**Sample time (-1 for inherited)** parameter. To configure the
integrator for continuous time, set the **Sample time (-1 for
inherited)** property to `0`

. To configure the integrator
for discrete time, set the **Sample time (-1 for inherited)** property
to a positive, nonzero value, or to `-1`

to inherit the sample time
from an upstream block.

This diagram illustrates the overall structure of the PSS1A power system stabilizer:

In the diagram:

*V_SI*is the power system stabilizer input. Commonly used inputs are speed, frequency, or power. For more information, see V_SI.The Low-Pass Filter (Discrete or Continuous) block can be used to model a transducer, with a time constant

*T*._{6}*K*models the stabilizer gain._{s}The Washout (Discrete or Continuous) block models a high-pass filter. Here,

*T*is the time constant._{5}The Second-Order Low-Pass Filter (Discrete or Continuous) block takes into account the low-frequency effects of the high-frequency torsional filters. Here,

*A*and_{1}*A*are the stabilizer denominator constants for the second-order block._{2}The two Lead-Lag (Discrete or Continuous) blocks models additional dynamics associated with the power system stabilizer, and represent two stages of the lead-lag compensation.

[1] *IEEE Recommended
Practice for Excitation System Models for Power System Stability
Studies.* IEEE Std 421.5-2016. Piscataway, NJ: IEEE-SA,
2016.

[2] Kundur, P. *Power
System Stability and Control*. New York, NY: McGraw Hill,
1993.

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