Lead-Lag Filter

Implement first-order lead-lag filter

• 

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

Description

The Lead-Lag Filter block implements the following transfer function:

$$H(s)=\frac{1+T_{1}s}{1+T_{2}s}$$

where

$$\begin{array}{c}s=\text{Laplace operator}\\ T_1,T_2=\text{time constants}\end{array}$$

This type of filter is used mainly for implementing lead-lag compensation in control systems. The key characteristics of the Lead-Lag Filter block are:

• Input accepts a vectorized input of N signals, thus implementing N filters. This feature is particularly useful for designing controllers in three-phase systems (N=3).

• The same block is used for continuous or discrete model. Changing the sample time Ts from 0 to a positive value automatically discretizes the filter, and vice versa.

• Filter states can be initialized for specified DC inputs and outputs.

Examples

The power_LeadLagFilter example shows two uses of a vectorized Lead-Lag Filter.

The model sample time is parameterized with variable Ts (default value Ts = 50e-6). To simulate continuous filters, specify Ts = 0 in the MATLAB^® Command Window before simulating the model.

Characteristics

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

Ports

Input

In1 — Input signal

scalar | vector

Input signal the block applies the transfer function to.

Output

Out1 — Output signal

scalar | vector

Output after the block has applied the transfer function.

Parameters

Time constant T1 (s) — T₁ filter time constant

5e-3 (default) | positive scalar

Specify the filter time constant(s) T₁ in seconds.

Time constant T2 (s) — T₂ filter time constant

20e-3 (default) | positive scalar

Specify the filter time constant(s) T₂ in seconds.

DC initial input and output — Input and output signal initial DC value

0 (default) | scalar | vector

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

Sample time — Block sample time

0 (default) | positive scalar

Specify the sample time of the block, in seconds.

Extended Capabilities

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

Version History

Introduced in R2013a