First-Order Filter

Implement first-order filter

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Libraries:
Simscape / Electrical / Specialized Power Systems / Control / Filters

Description

The First-Order Filter block implements one of the following transfer functions based on the Filter type selected in the block parameters window.

Low-pass filter:

$$H(s)=\frac{1}{1+Ts}$$

High-pass filter:

$$\begin{array}{c}H(s)=\frac{Ts}{1+Ts}\\ s=\text{Laplace operator}\\ T=\text{time constant}\end{array}$$

Characteristics

The key characteristics of the First-Order Filter block are:

• The input accepts a vectorized input of N signals and implements N filters. This feature is particularly useful for designing controllers in three-phase systems (N = 3).

• You can initialize filter states for specified DC and AC inputs.

• The block enables you to compute and plot filter response.

Direct Feedthrough	Yes
Sample Time	Specified in the Sample Time parameter Continuous if Sample Time = 0
Scalar Expansion	Yes, of the parameters
States	One state per filter
Dimensionalized	Yes

Examples

Use First-Order Filter Block with Lowpass and Highpass Filters

The power_FirstOrderFilter example shows various uses of the First-Order Filter block using two Filter type parameter settings (Lowpass and Highpass).

The model sample time is parameterized with variable Ts (default value Ts = 50e-6). To simulate continuous filters, specify Ts = 0 at the MATLAB^® command prompt before you start.

Ports

Input

Port_1 — Filter input

scalar | vector

First-order filter input signal, specified as a scalar or a vector.

Output

Port_1 — Filter output

scalar | vector

First-order filter output signal, returned as a scalar or vector.

Parameters

Filter type — Low-pass or high-pass filter

Lowpass (default) | Highpass

Determine the type of first-order filter. Set to Lowpass to implement a low-pass filter, set to Highpass to implement a high-pass filter.

Time constant (s) — Filter time constant

10e-3 (default) | positive scalar

First-order filter time constant, specified in seconds.

Sample time — Sample time of block

0 (default) | nonnegative scalar

Sample time of block, specified in seconds. Set to 0 to implement a continuous block.

Initialize filter states — AC and DC initial input

on (default) | off

When selected, the filter states are initialized according to the AC initial input: [ Mag, Phase (degrees), Freq (Hz) ] and DC initial input parameters.

AC initial input: [ Mag, Phase (degrees), Freq (Hz) ] — Magnitude of initial AC component

[0, 0, 60] (default) | three-element vector | N-by-3 matrix

Specify the magnitude of the initial AC component of the input signal, its phase, in degrees, and its frequency, in hertz. When the input is vectorized (N signals), specify an N-by-3 matrix, where each row of the matrix corresponds to a particular input. Phase can be any value. Mag and Freq must be positive.

Dependencies

To enable this parameter, select Initialize filter states.

DC initial input — Initial DC component of input signal

0 (default) | scalar | 1-by-N vector

Specify the value of the initial DC component of the input signal. When the input signal is vectorized, specify a 1-by-N vector, where each value corresponds to a particular input.

Dependencies

To enable this parameter, select Initialize filter states.

Plot filter response — Plot filter response and Bode diagram

off (default) | on

When selected, the filter step response and its Bode diagram (magnitude and phase of transfer function as a function of frequency) are plotted in a figure.

Frequency range (Hz): [Start, End, Inc.] — Frequency range to plot filter Bode diagram

[0, 200, 1] (default) | three-element vector of nonnegative scalars

The frequency range used for plotting the filter Bode diagram. Specify a vector containing the starting frequency, the end frequency, and the incremental frequency, in hertz.

Dependencies

To enable this parameter, select Plot filter response.

Extended Capabilities

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

Version History

Introduced in R2013a