STPM10: Reactive and Total Harmonic Distortion

royconejo · ‎2016-03-23

Posted on March 23, 2016 at 20:34

Hi, first of all I'm sorry for the offtopic, but there is no smart meter IC section on the entire forum, which is odd.

I've a functional prototype of a Smart Meter running on a STM32-F0/STPM10 platform. Before entering pre-production we'll need to solve this issues:

1) Sometimes the active power register goes DOWN by a little amount, generally decrementing by 2 (7,6 microWatt) when it does. We managed to count for this, but is it normal?

2) Active and Apparent energies are being measured well, we calculate cos fi and all. But Reactive as read is always not exact or even closer compared to the power triangle resulting from given P and S to get R. From the datasheet we have interpreted that the KAW constant should be multiplied by two to get the amount of Wh consumed, I mean:

ReactivePowerConsumed = ReactiveRegisterRead * 2 * KAW

For Type1 energy, we shold multiply by 4:

ActiveFundamentalPowerConsumed = Type1RegisterRead * 4 * KAW

Is this right?

3) Since Type1 energy is Active with noise and harmonics filtered, is there some way to calculate THD using this given data? or, what is the recommended method? is it possible to reliably sample iMOM and uMOM several times higher than the line frequency to do a FFT?

Thanks in advance,

Roy.

#stpm10

Tesla DeLorean · ‎2016-03-23

Posted on March 23, 2016 at 21:46

which is odd

I think it means you're supposed to work through the normal ST sales/support channels, and work with an assigned FAE?

The user space for power meters is pretty small and niche, and participants would be your competitors.

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royconejo · ‎2016-03-23

Posted on March 23, 2016 at 22:17

Hello clive1, I was expecting not to. It is a very narrow channel in which only a few medim/big companies can have a place.

It has been extensively proven that an open community with open knowledge gives more advantages and fair competition than ''problems''. Besides, this technology could be extensively applied not only in distributor smart meters but domotics, intelligent buildings and so forth if more small teams are involved and informed.

Just my own thoughts. Besides, if I don't receive any support through the usual channels I'll be in problems and I'll be forced to choose another provider.

Tesla DeLorean · ‎2016-03-23

Posted on March 24, 2016 at 00:06

I'm just trying to scope expectations, forums can be like empty rooms, I and a handful of other 'users' carry this forum. I don't work for ST, and I'm not looking to get into an argument about the merits of 'community' or smart meters, but forums only work if people show up and participate. I'm not sure where smart meter people hangout, but I don't think there are many active members here.

We'll see who else responds here, but we've had half-a-dozen meter questions here over the years, and I'm pretty sure the threads went nowhere.

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royconejo · ‎2016-03-23

Posted on March 24, 2016 at 01:42

Thanks clive1, I really appreciate your comments. I was exactly pointing to people with some experience on this IC, not official support. Perhaps there are none, or they can't share. That's ok. Same thing goes if someone has a problem with the STPM10 and I can help.