Okay, here's what I tested today:
Experiment-1:
Setup: A Victron 15k/230/200 that I set to 240v/60Hz single phase. I connected it's Output-1 directly to the L1-L2 of an Enphase IQ Combiner. I placed one 20-amp breaker on the combiner, and wired that directly to the red/black of a Q-cable with
one IQ7+ (connected to a 375w Bifacial panel). The IQ Combiner and the IQ7+ were both new-in-box, unconfigured.
Result: The IQ7+'s LED lit up with a blinking red, indicating that it was receiving power, "The AC grid is either not present or not within specification." -- according to the manual. No lights on the IQ Combiner at all.
Analysis: I looked over all of the connections, and I noticed that the IQCombiner's Envoy circuit board had a wire that led over to the unconnected (remember, this is single-phase 240v) "neutral" bus bar. My suspicion is that the power supply for the built-in Envoy runs on 120v, and that's why no lights were showing.
Experiment-2:
Setup: Same setup/config as Experiment-1, but I put the Autotransformer between the inverter and the IQ Combiner. The autotransformer was setup to produce 120/240v split phase, and created a neutral that could then be supplied to the IQ Combiner.
Result: Same red blinking lights on the IQ7+, but now, I had red blinking lights on the built-in Envoy as well! Progress! After a few minutes, the Envoy finished booting and I was able to press the "AP mode" button and get a green light. The IQ7+ started blinking orange, indicating that "The AC grid is normal but there is no communication with the Envoy." After a minute or two, the IQ7+ began to flash green, "Normal operation. AC grid function is normal there is communication with the Envoy."
At this point, I pulled out my phone and opened the Enphase Installer's Toolkit and was able to connect to the Envoy, update it's firmware / grid profiles and finish provisioning the one IQ7+. It took longer and was more complicated that it probably needed to, because I have
really terrible cell reception at the site and no other way to connect to the Internet.
Analysis:
- It appears that I was correct about the IQ Combiner's built-in Envoy being powered by 120v. Going back, and reviewing the schematics for the autotransformer confirmed this suspicion: L1 and L2 are essentially pass-through (they run through a DPDT breaker), with the windings producing a neutral.
- My suspicion is that I could put a very small 240v -> 120v power supply inside the housing of the IQ combiner, and wire it directly to the Envoy's terminal block and then it wouldn't matter "which side" of the autotransformer the combiner is connected.
- I believe that the "Powerline Communication" that the Envoy uses to talk to the IQ7+ will also work on "either side" of the autotransformer, since L1-L2 are pass-through.
After configuration, I was able to witness that my battery was charging with power produced by the panel. After adjusting the panel to point directly at the sun, I saw that it was producing ~380w, of which ~280w were being pushed back into the battery. I imagine the difference is the self-consumption of the Envoy (~8w) as well as the Quattro (~80w). Were I to wire up a second panel, I'd expect that the full production of that panel would be pushed back -- I'll test this once I receive a second IQ7+.
So, to answer my own questions (from above):
- My understanding is that the Victron has an installable assistant that can manage the frequency shifting necessary to control these units. Has anyone played with this?
This is the case, provided you are not connected to the grid -- it seems the Quattro is only capable of managing the frequency if it is operating in "Island mode." I was able to connect my computer using the MK3-usb cable and install the "PV assistant." I artificially lowered the top-end voltage configured for the battery and witnessed that the Quattro produced a frequency shift that turned off the IQ7+. (I'll play with it further to determine if I can do better than just "on/off" in the near future, but for now "on/off" is sufficient to my purposes.)
- Is it possible to place the Enphase Envoy on the 240v side of the autotransformer?
Yes.
- Do I need to get a different model # Envoy, depending on which side of the autotransformer it plugs into?
Kind of. The IQ Combiner seems to only come in a US model, and the built-in Envoy PCB is powered by 120v. If you put the IQ Combiner on the split-phase side of an auto transformer, you have a neutral / 120v and it will "just work."
I have not tested this, but it's very likely to work: If you put it on the 240v-single phase side, then it seems you need to purchase and install a small 240v-120v power supply and adjust the internal wiring to accommodate it. I will order the necessary power supply and report my results.
- If I install on the main-panel side of the autotransformer, will I need another Envoy if I install more panels in another location on the same micro-grid?
No. It appears that since the "Powerline Communication" only involves L1-L2, there's no interruption of communication, and it seems that you could put IQ7's on both sides of an autotransformer and it would not cause a problem.
- What would the best micro-inverter "grid profile" to use for a setup like this? (Though, I suppose that depends on the answers to some of the above.)
It does not seem to matter. You can choose a grid profile and configure the Victron to produce power within those specifications*.
*provided that you are not connected to the grid.
