Implement second-order filter
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.
Specify the type of filter: Lowpass, Highpass, Bandpass, or Bandstop (notch).
Specify the natural frequency of the filter, in hertz. This value must be a scalar or a vector.
Specify the damping ratio of the filter. The damping ratio is typically a value between 0 and 1.
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
Specify the sample time of the block, in seconds. Set to 0 to implement a continuous block.
When this check box is selected, filter states are initialized according to the AC initial input and DC initial input parameters.
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.
The AC initial input parameter is visible only when the Initialize filter states parameter is selected.
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.
The DC initial input parameter is visible only when the Initialize filter states parameter is selected.
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.
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.
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|
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.