What I'm learning about DIY Enphase and Hoymiles Microinverters
- Thread starter ncsolarelectric
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ncsolarelectric
Engineering Support CEO
It's a really crapy scratchy potentiometer and I had too much coffee. However, when the voltage was low and the PS was running in constant current mode, it did exhibit that behavior. After I set it, the voltage would drop and the current was maxed out. To control the output of the microinverter requires a power source operating with current-mode control like a buck converter, not voltage control. I don't see too many OTS power supplies that have a controllable interface, like the old GPIB units. What do they use these days for test equipment anyway?
fromport
Solar Addict
a)
I have no experience yet with hooking up a generator to an enphase system controller 2.
When it was discussed during the hands on training day it was referred to as "possible but with a lot of exceptions"
Older generators are likely not to work together, so people would be forced to replace their genset as well.
b)
I just looked up some documentation.
There is a list of approved generators.
c)
This document https://enphase.com/sites/default/files/2021-10/Enphase-Generator-Support-Technical-Brief.pdf
literally says "Back feed protection for remote start generator with M-series" and advises to install a shedding relay.
I don't have any feedback from real life experience.
ncsolarelectric
Engineering Support CEO
Oh, this is absolute gold! Thank you.
This makes it incredibly easy to connect an AC-coupled HM + Battery ESS to my existing Enphase system. It never needs to run when the Encharge is fully charged, so it can't back feed the battery inverters, they will simply use the energy to re-charge from the HM battery. So I could pair an 48V, LG Chem, EG4, or other UL Listed 48Vdc battery, with a bunch of HM microinverters and extend my Enphase battery capacity "cheap". Awesome!
@Ampster did you notice the parameters you were looking for in that grid profile regarding P/f droop, and P/V droop? Both of those specs are in there. As I suspected, it works in the positive direction for voltage. If the voltage exceeds 254.4Vac, the power drops 20.83%/V, so at 259.2Vac the power has dropped to zero.
Apparently, the FW is also one-sided. It starts at 60.1Hz and power is reduced at 50%/Hz at a rate of 2%/s. At 62Hz, the power is reduced to zero, but what about 58Hz? It's not on there.
This makes it incredibly easy to connect an AC-coupled HM + Battery ESS to my existing Enphase system. It never needs to run when the Encharge is fully charged, so it can't back feed the battery inverters, they will simply use the energy to re-charge from the HM battery. So I could pair an 48V, LG Chem, EG4, or other UL Listed 48Vdc battery, with a bunch of HM microinverters and extend my Enphase battery capacity "cheap". Awesome!
@Ampster did you notice the parameters you were looking for in that grid profile regarding P/f droop, and P/V droop? Both of those specs are in there. As I suspected, it works in the positive direction for voltage. If the voltage exceeds 254.4Vac, the power drops 20.83%/V, so at 259.2Vac the power has dropped to zero.
Apparently, the FW is also one-sided. It starts at 60.1Hz and power is reduced at 50%/Hz at a rate of 2%/s. At 62Hz, the power is reduced to zero, but what about 58Hz? It's not on there.
| Frequency Watt (FW) | - | |
| FW F&C Code | 20497 | |
| FW Function Activated | 1 | |
| Start of Frequency Watt Droop (Fstart) | 60.1 | Hz |
| FW Droop Slope (Kpower_Freq) | 50 | Pn%/Hz |
| Recovery Ramp Rate (RRR) | 2 | Rated%/s |
| FW Settling Time (Tr) | 5 | s |
| Volt Watt (VW) | - | |
| VW F&C Code | 24576 | |
| VW Function Activated | 1 | |
| Start of Voltage Watt Droop (Vstart) | 254.4 | V |
| End of Voltage Watt Droop (Vend) | 259.2 | V |
| VW Droop Slope (Kpower_Volt) | 20.83 | Pn%/V |
svetz
Works in theory! Practice? That's something else
The manual ones can be had fairly cheaply, but those with APIs are expensive... that's why I came up with the PWM approach. After seeing your setup though I've realized you don't even need the PWM. Just like the chargers are stacked in that drawing to accomodoate different levels of solar power, the microinverters can also be stacked for incremental power output. I'll put up an alternate drawing when I get some time.
The Enpower has a relay switch it uses to turn the generator on/off, the Envoy decides when and it's configurable and the output is voltage controlled (generators are a voltage source after all).
As to back-feeding, it's not 100% prevented; that's why the Enphase engineering documents requires the minimum generator size be roughly on par with the number of active panels (that is you can also use PV shedding when the generator is running if needed).
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svetz
Works in theory! Practice? That's something else
Enphase engineering covers the daylight_solar+battery+generator use case; but... if you only run at night then solar surge must always be zero.
Frequency-watt power throttling is only greater than 60 Hz for the U.S. grid. However, under 60 Hz will soon be a methodology by which a utility can request more power from ESSes (e.g., a home-owner with a grid-tied battery).
ncsolarelectric
Engineering Support CEO
Nice!
I can see how being able to write and install my own grid profile would be incredibly powerful.
Ampster
Renewable Energy Hobbyist
Are you saying that the Enphase System Controller 2 has 48 volt leads so you can add battery capacity to the Encharge? If so wouldn't that allow DIYers to cannibalize sales of Encharge batteries?
Thanks. I understand the general concept of UL1741SA and how it works. I am not well versed in the terms p/f and P/V droop but so far have not found a need to think about those things. The unanswered question for me in your earlier experiment is whether the System Controller 2 is using frequency or voltage to control the AC coupled inverters.
ncsolarelectric
Engineering Support CEO
No, I'm saying that it can control turning a generator on/off based on the SOC of the Encharge battery. The generator, in this case, is the HM microinverters pulling power from a 48Vdc battery bank.
Unfortunately, I don't have a means of observing frequency and power simultaneously in real-time (yet). Just one sample every 15 minutes or so. The weather is not cooperating either. Clouds coast to coast. I can look for Power/Voltage control, but I never saw the microgrid go above 241V. According to the grid parameter, it would need to be above 254.4Vac, and I can confirm that didn't happen.
ncsolarelectric
Engineering Support CEO
Ah! There's the rub. If the generator isn't on the list, it isn't in the Installer App, so the generator port of the SC2 can't be activated. So it's a no-go doing it that way unless I buy one of those generators to activate it.
svetz
Works in theory! Practice? That's something else
Given there are only two wires representing on/off, I suspect you could pick anything on the list and it would at least appear to work.
The question is what's under the covers in terms of timing/power limits. Although once activated, those might be adjustable.
ncsolarelectric
Engineering Support CEO
It looks like Enphase did use P/f control to curtail the HM inverter. See my latest experiment with lots of data.
(Wonder why my dog is named Data?)
phipsi1237
New Member
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Tried deleting my post because I didn't realize there were already over 170 posts. I'll read first before repeating...Sorry.
phipsi1237
New Member
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Where is this document? All the new warranty information talks about "covered owners" and defines that.
fromport
Solar Addict
Can you please write down in a few sentence what the outcome was instead of forcing me to view a video ?
Thanks!
ncsolarelectric
Engineering Support CEO
The HM-Inverter throttled back as the voltage and frequency increased, with a very light load on the IQB3T microgrid. The microgrid voltage started at 239.9V. As the HM ramped up the voltage, the frequency increased, 241.6V 60.12Hz, 243.1V 60.30Hz, 246.3V 60.68Hz, 242.9V 60.29Hz. At the same time, the IQ8+ inverters ramped down to 4 to 6 watts each and then went to 0 watts each. The HM supported the entire 110W load for 30 minutes while the IQ8s took a snooze. When I added the air conditioner, they woke back up and stayed throttled to about 34W each, until I reconnected the grid. The Enphase system forms the microgrid, so that shows it regulates using P/F control and can control the HM inverters on the same grid but not at the same P/F rate as the IQ8s. In other words, they don't share equally while drooping. The IQ8s are "faster" in the sense that they "droop" their output power more quickly than the HM-350NT.
Considering that the HM will droop power with voltage P/V, such that at 254.4V it starts drooping the output power, by 259.2V it's 0 power, and at 264V it disconnects the output completely. The IQB3T grid voltage input spec goes all the way to 264V. So in that sense, they are compatible and under normal conditions, they should be able to work well together. I would consider adding an additional surge protector in my combiner box to limit any surge from the solar panels that might damage the battery or SC2. It has a 10mm MOV, which IMO is a toy.
svetz
Works in theory! Practice? That's something else
In the video you mentioned the 246V surge wasn't a problem. You probably know, but just in case, "surge" means something else. In the U.S., the permissible grid range is plus or minus 5% of 240V and all UL gear will operate in those ranges.
Surge protecters for 240V typically don't kick-in until much higher voltages, for example, this 240V surge protection device kicks in at 470V.
You can't measure surge with a standard meter. Surge voltages can easily hit 1,000V from normal occurrences such as a high-amp inductive motor turning off inside the home. There are multiple of these per day in the average home. Fantastically high surges (e.g., 100,000V) also occur, but at a much lower rate (e.g., nearby lightning strikes).
Usually, they don't let the magic smoke out all at once because they're so fast (typically measured in microseconds). Instead, they erode your electronic devices little by little.
Surge protecters for 240V typically don't kick-in until much higher voltages, for example, this 240V surge protection device kicks in at 470V.
You can't measure surge with a standard meter. Surge voltages can easily hit 1,000V from normal occurrences such as a high-amp inductive motor turning off inside the home. There are multiple of these per day in the average home. Fantastically high surges (e.g., 100,000V) also occur, but at a much lower rate (e.g., nearby lightning strikes).
Usually, they don't let the magic smoke out all at once because they're so fast (typically measured in microseconds). Instead, they erode your electronic devices little by little.
fromport
Solar Addict
So when you combine IQ & HM on your system working from Enphase batteries, the HM will do the heavy lifting even throttling the IQ to 0.
When more load needs to be served IQ will ramp up but still not work "as hard" as the HM's.
I don't know if that is such a good combination. I would rather have everyone pull it's fair share instead of a few doing the hard work all the time.
ncsolarelectric
Engineering Support CEO
I'm an expert at designing surge suppressors and power protection circuits. In the 1990's we were shipping power conditioners to India where the power quality was attrocious. +/- 50-100% swings in voltage, above and below nominal. The trick is to use an MOV then a smaller value MOV in series with a gas discharge tube. If the voltage exceeds 265V, it starts to clamp. If it exceeds 300V, the gas tube sparks and the 2nd MOV adds more energy absorption to keep it from getting any higher.
Back in 2012 a company hired me as a consultant to design the power protection circuit for their microinverter, based on a similar comment to yours that I made. "OTS surge traps won't work." When they got to doing their UL testing, the OTS surge protector didn't protect their inverter and it failed the test. They called me and I fixed it in under a week, and in under a month, they redesigned the board and passed the UL test. Then promptly ran out of funds and went under. Had they hired me a year earlier when I made the comment.... who knows.
Just FYI. Thanks.
ncsolarelectric
Engineering Support CEO
My goal is low cost, not perfection. Here, energy is only 7.7 cents a kWh. Enphase is too expensive, period. HM is less than half the price. If it works, I couldn't care less that the Enphase inverters are slackers.
