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power_fftscope

Perform Fourier analysis of signals stored in Structure with Time format

Syntax

power_fftscope
FFTDATA = power_fftscope(ScopeData)
FFTDATA = power_fftscope(FFTDATA)
power_fftscope(ScopeData)
power_fftscope(FFTDATA)

Description

power_fftscope opens the FFT Analysis Tool dialog box to perform Fourier analysis of signals stored in a Structure with Time format. The dialog box provides access to all the Structure with Time variables that are defined in your workspace. This tool can also be activated from the Powergui block dialog box by selecting FFT Analysis.

FFTDATA = power_fftscope(ScopeData) returns the FFT results for the signal saved in the ScopeData structure. fftdata is a structure with the fields in the following table:

FieldDescription
timeThe time vector of the structure with time signal saved in the ScopeData variable.
signalsThe signals saved in the ScopeData variable.
blockNameThe name of the Scope block associated to the ScopeData variable.
inputThe input signal of the selected Structure with Time variable.
signalThe index of the selected input signal specified by the input field.
StartTimeThe start time of the FFT window.
cyclesThe number of cycles of the FFT window.
fundamentalThe fundamental frequency of analyzed signal.
MaxFrequencyThe maximum frequency evaluated by the FFT analysis.
THDmaxFrequencyThe maximum frequency for the THD calculation. Set the value to inf to calculate the THD at the Nyquist frequency.
FFTdataThe analyzed signal (FFT window data).
THDbaseThe base used to compute the THD. Set to "fund" to normalize the THD with respect to fundamental value. Set the THDbase to "DC" to normalize the THD with respect to the DC component value.
magThe computed magnitude of FFT.
phaseThe computed phase of FFT.
freqThe frequency vector.
THDThe computed Total Harmonic Distortion for the analyzed signal. The THD calculation includes all the inter-harmonics of the selected input signal.
samplingTimeReturns the sampling time of the selected input signal.
samplePerCycleReturns the number of samples per cycle of the selected input signal.
DCcomponentReturns the DC component value of the selected input signal.
magFundamentReturn the fundamental component value of the selected input signal.

FFTDATA = power_fftscope(FFTDATA) uses the FFTDATA structure as a template variable to modify analysis settings and signal selection, and to perform FFT analysis.

power_fftscope(ScopeData) plots the FFT analysis results for the last simulation cycle of the signal saved in the ScopeData structure.

power_fftscope(FFTDATA) plots the FFT analysis results for the signal options specified in the FFTDATA structure.

Dialog Box

Refresh

If selected, refresh the list of structures with time variables in the Available signals list. Refreshing allows you to import additional simulations signals without the need to close and reopen the tool.

Name

Lists the structures with time variables that are present in your workspace. These structures are generated by the Scope or To Workspace blocks in your model. You can refresh the list of available signals by clicking the Refresh button. The signals must be sampled at a fixed rate by using the Scope block settings. Use the drop-down list to select the variable that you want to analyze.

Input

Select the input signal of the selected structure with time variables specified in the Structure field. Structures with time variables having multiple inputs can be generated by a Scope block having multiple input ports.

Signal number

Indicates the index of the selected input signal specified by the Input parameter. For example, the Signal number parameter allows you to select the phase A signal of a three-phase signal connected to input 2 of a Scope block.

Display Signal

If selected, in the upper plot, displays the signal selected by the Structure, Input, and Signal number parameters.

Display FFT window

If selected, in the upper plot, displays the portion of the selected signal where the FFT analysis is performed.

Start time(s)

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

Specifies the number of cycles of the selected signal to analyze for the FFT analysis.

Fundamental frequency

Specifies the fundamental frequency, in hertz (Hz), as a reference frequency for the FFT analysis.

Max Frequency

Specifies the maximum frequency, in hertz (Hz), for the FFT analysis.

Max frequency for THD computation

Select the Nyquist frequency to compute the THD to a maximum frequency equal to the Nyquist frequency. The Nyquist frequency is half the sampling frequency of the selected signal.

Select the Same as Max frequency to compute the THD to a maximum frequency equal to the frequency specified in the Max frequency parameter.

The THD calculation includes all the inter-harmonics of the selected input signal.

Display style

In the drop-down list, 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 % relative to the fundamental or DC component. Select List(relative to specified base) to display the spectrum as a list in % 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

Enter a base value for the display of harmonics.

Frequency axis

In the drop-down list, 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.

Display

In the lower plot, displays the FFT analysis results for the selected measurement.

Close

Closes the FFT Analysis Tool window.

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