FFT Analyzer
Description
The FFT Analyzer app allows you to perform Fourier analysis of simulation data and provides access to all the simulation data that are defined as structure-with-time variables in your workspace. The app displays the spectrum as a bar graph or as a list in percentages relative to a base value or to the DC component of the signal.
![](fft_analyzer_app.png)
Open the FFT Analyzer App
powergui Block Parameters dialog box: On the Apps tab, click FFT Analyzer.
MATLAB® command prompt: Enter
powerFFT
Parameters
Structure with time (click to update)
— Refresh simulation data variables
button
Refreshes the list of simulation data variables in the Structure with time drop-down menu. Refreshing allows you to import additional simulation signals from the workspace without the need to close and reopen the tool. If the workspace contains no structure-with-time variables, the drop-down menu shows Empty list.
Structure with time
— List of simulation data variables
Empty list (default)
Lists all the simulation data variables that are present in your workspace. Use the drop-down list to select the structure-with-time variable that you want to analyze. If the workspace contains no structure-with-time variables, the list shows Empty list. Structure-with-time variables are generated by the Scope and To Workspace blocks in your model.
Signal
— Selected signal
no default
Lists the signal of the structure-with-time variable specified in the Structure with time drop-down menu. Structure-with-time variables that have multiple signals can be generated by a Scope block that has multiple input ports. The list shows the name of the signals as they are labeled in your models. If a signal is not labeled, such as the third signal of Scope2 in this figure, the list shows unnamed (input 3).
Dimension
— Index of selected signal
no default
Indicates the index of the signal specified by the Signal parameter. For example, the Dimension parameter allows you to select the Ib measurement of a three-phase signal connected to the second input of Scope2 block.
Zoom on
— Upper plot zoom
Signal
(default) | FFT window
Select Signal
to display the complete view of the signal
selected by the Structure with time, Signal,
and Dimension parameters in blue in the upper plot. The FFT window
that is specified by the Start time, Number of
cycles, and Fundamental frequency parameters is
displayed in red.
Select FFT window
to display only the portion of the
selected signal where the FFT analysis is performed in the upper plot.
Start time (s)
— Start time of the FFT analysis
0 (default) | positive scalar
Specifies the start times for the FFT analysis. The FFT analysis is performed on the portion of the signal starting at the specified time and for the specified number of cycles.
Number of cycles
—
1 (default) | positive integer
Specifies the number of cycles of the selected signal to analyze for the FFT analysis.
Fundamental frequency (Hz)
—
60 (default) | positive scalar
Specifies the fundamental frequency, in Hz, as a reference frequency for the FFT analysis.
Max frequency (Hz)
—
1000 (default) | positive scalar
Specifies the maximum frequency, in Hz, for the FFT analysis.
Max frequency for THD computation
—
Nyquist frequency
(default) | Same as Max frequency
Select Nyquist frequency
to compute the THD to the
maximum frequency equal to the Nyquist frequency. The Nyquist frequency is half the
sampling frequency of the selected signal.
Select Same as Max frequency
to compute the THD to the
maximum frequency equal to the frequency specified in the Max frequency
(Hz) parameter.
The THD calculation includes all the inter harmonics of the selected input signal.
Display style
— Display style for spectrum
Bar (relative to fundamental)
(default) | Bar (relative to specified base)
| Bar (relative to DC component)
| List (relative to fundamental)
| List (relative to specified base)
| List (relative to DC component)
Select Bar (relative to fundamental)
to display the
spectrum as a bar graph relative to the fundamental frequency. Select Bar
(relative to specified base)
to display the spectrum as a bar graph
relative to the base defined by the Base value parameter. Select
Bar (relative to DC component)
to display the spectrum as a
bar graph relative to the DC component of the signal.
Select List (relative to fundamental)
to display the
spectrum as a list in percentages relative to the fundamental or DC component. Select
List (relative to specified base)
to display the spectrum
as a list in percentages relative to the base value defined by the Base
value parameter. Select List (relative to DC
component)
to display the spectrum as a list relative to the DC
component of the signal.
Base value
— Harmonics base value
1 (default) | positive scalar
Enter a base value for the display of harmonics.
Frequency axis
— Frequency axis of FFT spectrum
Hertz
(default) | Harmonic order
Select Hertz
to display the spectrum frequency axis in
hertz. Select Harmonic order
to display the spectrum
frequency axis in harmonic order relative to the fundamental frequency.
Compute FFT
—
button
Displays the FFT analysis results for the selected simulation data signal in the FFT graph.
Version History
Introduced in R2021a
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