Datasheet

90E36A POLY-PHASE HIGH-PERFORMANCE WIDE-SPAN ENERGY METERING IC
Function Description 19 April 2, 2013
3.6 FOURIER ANALYSIS FUNCTION
The 90E36A offers a hardware DFT Engine for 2
nd
to 32
nd
order har-
monic component, both V and I of each phase with the same time
period.
The registers can be divided as follows:
- voltage and current for each phase
- phase A / phase B / phase C
- 32 frequency components (fundamental value, and harmonic
ratios)
- Total Harmonic Distortion (THD)
The harmonic analysis is implemented with a DFT engine. The DFT
period is 0.5 second, which gives a resolution frequency bin of 2Hz. The
input samples are multiplied with a Hanning window before feeding to
the DFT processor. The DFT processor computes the fundamental and
harmonic components based on the measured line frequency and sam-
pling rate, which is 8KHz.
Figure-6 Analysis Function
Hanning
Window
X
DFT
Computation
Engine
Frequency
Components
for
Fundamental
and Harmonic
Post-
Processing
Ratios for
Fundamental
and Harmonic
Harmonic Analyzer
Line Frequency
Sample
Frequency
Sample
Capture
Input
sample
from DSP
processor
X
Scaler
To DMA Module