Second-Order Low-Pass Filter (Discrete or Continuous)

Discrete-time or continuous-time second-order low-pass filter

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Libraries:
Simscape / Electrical / Control / General Control

Description

The Second-Order Low-Pass Filter (Discrete or Continuous) block implements a second-order low pass filter in conformance with IEEE Std 421.5-2016^[1]. In the standard, the filter is a single input, single output signal conditioner that is used in the Power System Stabilizer PSS1A.

In the PSS1A, the filter accounts for some of the low-frequency effects of high-frequency torsional filters. It can also help shape the gain and phase characteristics of the stabilizer.

To switch between continuous and discrete implementations of the Second-Order Low-Pass Filter (Discrete or Continuous) block, adjust the Sample time parameter value.

Initial Conditions

To specify the initial conditions of this block, set Initialization to:

• Inherited from block input — The block sets the state and output initial conditions to the initial input.

• Specify as parameter — The block sets the state initial condition to the value of Initial state.

Ports

Input

u — Filter input

scalar or vector

Filter input.

Data Types: single | double

Output

y — Filtered output

scalar or vector

Filtered output. The output has the same number of elements as the input.

Data Types: single | double

Parameters

Coefficient of s, A1 — A1 coefficient

0.1 (default) | positive scalar

A1, the signal conditioning frequency filter coefficient of s.

Coefficient of s^2, A2 — A2 coefficient

0.2 (default) | positive scalar

A2, the signal conditioning frequency filter coefficient of s².

Initialization — Initial state specification

Inherited from block input (default) | Specify as parameter

Specify the initial state condition for this block. For more information, see Initial Conditions.

Initial state — Initial state

0 (default) | real number

Block initial state.

Dependencies

To enable this parameter, set Initialization to Specify as parameter.

Sample time (-1 for inherited) — Block sample time

-1 (default) | 0 | positive scalar

Time between consecutive block executions. During execution, the block produces outputs and, if appropriate, updates its internal state. For more information, see What Is Sample Time? and Specify Sample Time.

For inherited discrete-time operation, set this parameter to -1. For discrete-time operation, set this parameter to a positive integer. For continuous-time operation, set this parameter to 0.

If this block is in a masked subsystem or a variant subsystem that supports switching between continuous operation and discrete operation, promote this parameter to ensure correct switching between the continuous and discrete implementations of the block. For more information, see Promote Block Parameters on a Mask.

References

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

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018b