Guru
Joined: 13/10/2014
Location: AustraliaPosts: 1860
| Posted: 01:49am 27 Apr 2025 |
FYI: Following on from kWh code changes to my Solar Monitor:
NOTE: The efficiency quoted when doing static loaded efficiency testing on the Inverter is in the high ninety % range, depending on the AC Load PF, it's normally measured with a resistive load which presents a very high PF to the Toriod.
The efficiency I'm calculating here is a "Long Term" indication of combined Inverter conversion loss, plus combinations of reactive, capacitive and inductive Load loss, and resistive Loads for a "System Wide" indication of overall Solar to AC efficiency.
Loads that cause harmonics (THD) and reactive power loss account for most of the loss indicated in the overall efficiency.
After rewriting the code for accumulative DC kWh readings (loss adjusted to also Indicate AC output kWh) the Load (Inverter kWh) is tracking commercial AC kWh meters perfectly for total kWh after 11 days 24/7 running.
The overall efficiency is running at 90%, obviously the efficiency increases slightly when higher power levels are run for longer periods of time and decreases as average consumption drops when workshop equipment is not being used, we have had very low power usage over this time which is holding the accumulative efficiency low.
The second loss is from poor AC Load Power Factor (PF), currently with just normal low House loads the PF is 63% which is very poor, this causes extra heating of the Toroids and higher power from the Inverter and Batteries to produce the True AC power consumed by the Load.
The commercial AC Monitors are taking the PF into account when calculating kWh, obviously Inverter DC power knows nothing about the effect of AC PF, it just delivers the power the Toriod needs to meet the AC demand and overcome the PF loss.
The Monitor also tracks, total PVA generation, total PVA to the Inverter (Load), total PVA Charge to the Batteries and Total discharge from the Batteries.
The Monitor now accurately tracks DC Kwh Battery Charge and Discharge cycles, tracking is better than the BMS and other commercial independent Battery monitors, as they fall off at very low charge/discharge rates and lose accuracy.
And I finally settled on the Minute accumulator updating with 60 counts per minute.
Without knowing how granular commercial AC kWh Meters were, I was unsure if that would be enough to get turbulent DC power levels to accurately track AC kWh readings, turns out it is.
I'm sure someone will point out that I could have any number of samples for Minute accumulation values, which I tested with no real change, 60 is a nice round number and total DC kWh (loss adjusted) accurately tracked AC kWh accumulation at that sample value. I look forward to seeing how this works out over the next few months.
Perhaps I need some auto PF correction cap banks.
That's the problem with the newer "Inverter Drives" in Fridges, Freezers, and Air conditioning, add all the SMPS Plug packs powering everything these days, then add the high power workshop equipment with Induction motors, big Brush motors and the number of SMPS AC chargers for Battery operated equipment that always seem to be charging 3 or 4 big somethings
It's nice when the 2.8kW Water Heater turns on and dumps a nice big resistor across the AC, makes the PF look a bit better.
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Edited 2025-04-27 12:37 by KeepIS