This is an online Fast Fourier Transform (FFT), which can determine the harmonic magnitude and phase of the input signal as a function of time. The input signals first sampled before they are decomposed into harmonic constituents.
Options are provided to use one, two or three inputs. In the case of three inputs, the component can provide output in the form of sequence components.
The user may select one of the following three FFT block types:
1 Phase: This is a standard 1-phase FFT. The input is processed to provide the magnitudes Mag and phase angle Ph of the fundamental frequency and its harmonics (including the DC component dc).
2 Phase: This is nothing more than two 1-phase FFTs in a single block, in order to keep things compact and organized.
3 Phase: As above, is merely three 1-phase FFTs combined in one block.
+/-/0 seq: This takes a 3-phase input XA, XB, XC and calculates the FFT preliminary output through a sequencer, which outputs positive (+), negative (-), and zero-sequence magnitude and phase components of the fundamental, and each harmonic. The DC components of each phase are also output.
3 Phase SLD: Same as 3-phase above except the input connection is a 3 element array.
+/-/0 Seq SLD: Same +/-/0 Seq above except the input connection is a 3 element array.
The sequence components are computed based on the simple transformation equation:
NOTE: Due to the discrete nature of the algorithm, any sub-harmonics or inter-harmonics present in the measured signal will interfere with the output. The measured signal should be free from inter-harmonics and sub-harmonics for accurate results.
More: |