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Discrete-time or continuous-time single input PSS7C power system stabilizer

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

The SM PSS7C block implements a double-input PSS7C 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 represent two different types of dual-input power system stabilizers with this same model:

A stabilizer that uses electrical power and speed (or frequency) signals to calculate the integral of the accelerating power. This make the calculated stabilizer signal insensitive to mechanical changes.

A stabilizer that uses a combination of electrical power and either speed or frequency. To achieve the desired stabilizing signal shaping, the system uses the speed directly, without phase-lead compensation, and adds a signal that is proportional to the electrical power.

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 PSS7C power system stabilizer:

In the diagram:

*V_SI1*and*V_SI2*are the two power system stabilizer inputs. Commonly used inputs are speed, frequency, or power.Two Washout (Discrete or Continuous) blocks are represented for each stabilizer input, with time constants

*T*to_{W1}*T*, along with a transducer, represented by a Low-Pass Filter (Discrete or Continuous), with time constants_{W4}*T*and_{6}*T*._{7}To allow a ramp-tracking filter characteristic, the Ramp Tracking Filter subsystem models a network of lead-lag and low-pass filter blocks in series.

To provide phase compensation, the Multi-band subsystem implements a canonical state equation, with time constants

*T*to_{i1}*T*and gains_{i4}*K*to_{0}*K*._{4}The PSS output logic subsystem allows the representation of the PSS output logic associated with the generator active power output.

*P*and_{PSSon}*P*are the threshold values used to define a hysteresis._{PSSoff}

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