Question regarding implementation of 3-phase power metering based on FFT metering libraries, deciding whether to use qt timer based U-I phase shift compensation or software based.
- how to trigger SD conversion (312us interval)?
- is there additional delay needed between SD triggering for each phase as in Figure 5.?
- how to fill phase-shift correction buffer for METERLIBFFT3PH_InitMainBuffPhX?
- is it ok to calculate phase shift correction based on power factor during calibration
process and use same value for each harmonic in buffer?
But you might also note that if you take, for instance, 32 samples per phase, that's 96 samples total, or one every 3.75 degrees. 120 degrees is indeed exactly a 32-sample delay. So with these regularly-placed interleaved-samples of all three phases you get exact in-phase alignment of a binary-count of samples on each phase (convenient for FFTs of course!) --- if sample '0' is 0-degrees on phase A, sample 32 will be 0-degrees on phase B, and sample 64 will be 0 degrees on phase C.
All phases (ADC results) are absolutely independent in this case. You may imagine it as three 1-ph meters, in fact. You will get three independent binary buffers. For your 32-samples example it means, that you sample input periodic signal every 11.25 degree (360/32) on each phase:
sample '32' = sample '0' of the next period, etc., etc.
2.