Implement second-order filter
Simscape / Electrical / Specialized Power Systems / Control / Filters
Based on the Filter type selected in the block menu, the Second-Order Filter block implements the following transfer function:
Band-stop (notch) filter:
The key characteristics of the Second-Order Filter block are:
Input accepts a vectorized input of N signals, implementing N filters. This feature is particularly useful for designing controllers in three-phase systems (N = 3).
Filter states can be initialized for specified DC and AC inputs.
It enables you to compute and plot filter response.
- Filter type
Specify the type of filter:
- Natural frequency fn (Hz)
Specify the natural frequency of the filter, in hertz. This value must be a scalar or a vector. Default is
- Damping ratio Zeta (Q = 1/(2*Zeta))
Specify the damping ratio of the filter. The damping ratio is typically a value between 0 and 1. Default is
The damping ratio is related to the filter quality factor Q:
For a bandpass or a bandstop filter, the 3 dB bandwidth is given by
- Sample time
Specify the sample time of the block, in seconds. Set to 0 to implement a continuous block. Default is
- Initialize filter states
When this check box is selected, filter states are initialized according to the AC initial input and DC initial input parameters. Default is selected.
- AC initial input: [ Mag, Phase (degrees), Freq (Hz) ]
Specify the magnitude of the initial AC component of the input signal, its phase, in degrees, and its frequency, in hertz. Default is
[0, 0, 60].
When the input is vectorized (N signals), specify an N-by-3 matrix, where each row of the matrix corresponds to a particular input.
The AC initial input parameter is visible only when the Initialize filter states parameter is selected.
- DC initial input
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. Default is
The DC initial input parameter is visible only when the Initialize filter states parameter is selected.
- Plot filter response
When this check box is 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. Default is cleared.
- Frequency range (Hz): [Start, End, Inc.]
Specify the frequency range for plotting the filter Bode diagram. Specify a vector containing the starting frequency, the end frequency, and the incremental frequency, in hertz. Default is
[0, 500, 1].
The Frequency range parameter is visible only when the Plot filter response parameter is selected.
|Sample Time||Specified in the Sample Time parameter|
Continuous if Sample Time = 0
|Scalar Expansion||Yes, of the parameters|
|States||Two states per filter|
shows the Second-Order Filter block using two Filter type parameter
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 starting the simulation.