ADE7854 energy accumulation configuration

Hi,

I am trying to configure the ADE7854 with the following conditions:
- PMAX = 33516139
- Source frequency = 8000 Hz
- V_FS = 389,26228V
- I_FS = 44,19417A
- 3 phases to be measured
- Reading accumulated energy every 1 second (awatthr, bwatthr and cwatthr)
- Need to support reverse energy (negative watthr)

Which type of energy accumulation would you recommend?

In 'normal accumulation mode', I encountered the following issues:
- Loss of measurement data when reading
- Accuracy (value/LSB) cannot be set below 0,000597331 watt/hr.
Further described here: https://ez.analog.com/energy-metering/f/q-a/551942/ade7854-energy-accumulation-inaccuracy-when-reading-on-higher-interval

I've also looked at "Lince cycle active energy accumulation mode", but I'm not sure if this is possible with reverse energy, measuring 3 phases (and reading at the specified interval (1s) rather than looking at the interrupts)?

Hope you can answer my question(s).
Thanks in advance.

Regards,
Casper

  • Hi Casper

    If you set a short accumulation time 1 sec and bin your reading base on positive or negative energy this is the best you can do. You can do smaller times to improve your resolution and accuracy of neg and pos power.

    so at 1 sec full scale power = 8000 lsb 

    at 1000:1 or 44,19417A/1000 you will get   8 lsb in the WATTHR register over 1 sec.

    So if you set to 1 sec line cycle accumulation and bin energy  to positive or negative in the micro. This is not perfect if the power changes from pos to negative there is some overlap and cancelation of power in the accumulation. The smaller the integration time the less error you should get.

    The internal accumulator hold and residual so it is not lost just left in the accumulator. This accumulator will hold something less than 0,000597331 watt/hr

    I am not sure why in normal accumulation mode you would lose energy is this in comparison to cf output? Are you doing read with reset or linecycle accumulation.

    Dave

  • I am not sure why in normal accumulation mode you would lose energy is this in comparison to cf output? Are you doing read with reset or linecycle accumulation.

    Hi Dave,

    Thanks for your reply.
    The issue I am experiencing with normal energy accumulation is as follows; (this is all with reset-on-read)
    When reading at a higher interval (for example 1 vs 10 seconds), I don't get the same energy consumption over time.
    So, when reading a constant 1 w/hr every second, I would expect to read 10w/hr every 10 seconds.

    I think this is caused by the "readings below the LSB" being reset as well.
    So, for example, if LSB is set to 1 kw/h, I might lose up to 0.9kw/h per reading.
    (reading 10 times more causes more loss of 0.9kw/h accumulation)
    Could you verify this thought?

    Thanks in advance.
    - Casper


  • Why are you setting to 1Kw/lsb you will get better resolution if pmax is 0x1FF686B. Try line cycle accumulation for 1 sec do you get the same problem? It is possible the path resets not sure if that is the case. I will see if I can verify.

    I would still recommend line cycle accumulation for this case.

    Dave

  • Are you setting your noload correctly?