What I'm learning about DIY Enphase and Hoymiles Microinverters

[ncsolarelectric]

I changed my comment to read Ensemble. My apologies if I sounded like I was trashing the IQ8. I have been using IQ7s for several years and recently installed another 23 to AC couple with my hybrid. I have had good support from Enphase.

If I read the initial comment by @ncsolarelectric the IQ8 can not natively generate power without the addition of the System Controller 2? He does describe it as pricey but I do not know how much it adds to an installation? That may be the technology that you were referring to?

They can't form a microgrid without the System Controller 2, a cell modem, a wifi communications kit, and 2 load controllers or an IQ battery. Wholesale, that's over $2700 to $3700 for just those parts. Not counting the solar or Envoy. It's even higher if you're doing a line-side tap and need the main and output breakers for the SC2.

 

[ncsolarelectric]

Thanks for running that low-wattage off-grid experiment. That was super exciting and very encouraging.
I posted a comment there, but I'm suspicious that the "consuming" is correct, could be like you were seeing earlier where the output isn't truly from the CT. Possibly @fromport knows if there's a setting like he had in #81.

I'd really like to see the Hoymiles output during that test, if the Hoymiles is throttling back that's seriously big news. I've based the "it doesn't use frequency shifting" based on my digital meter's reading, but it could be my meter isn't accurate enough. Do you have a clamp meter you can measure the amps on the Hoymiles output?

I have a cheap Fluke amp clamp arriving today to measure the current and voltage. The test is to turn off the IQ8s except for the IQ Battery 3 to form a microgrid with the least Enphase inverters, and then reduce the load to a minimum. Then see if the inverter throttles back the current automatically to prevent overvoltage, or if it hiccups like the APSystems microinverters by just disconnecting itself. Damn mail is slow and the sky is dark!

 

[svetz]

...The test is to turn off the IQ8s except for the IQ Battery 3 to form a microgrid with the least Enphase inverters, and then reduce the load to a minimum...

Sweet! I'd suggest getting the amp reading of the Hoymiles output on-grid, and then the amp reading of the load and Hoymiles off-grid at the lowest wattage you can get (100 watts in your other test). Possibly an IQ8 output for scenario 2 below if the readings are unexpected.

When I saw the 100 watts in the video that just seemed wrong. It seemed the Hoymiles should be outputting 300 watts and at least one IQ8 had to be outputting power. If an IQ8 wasn't generating power, then the Hoymiles should have to go into anti-islanding and shutdown. With a clamp meter, you'll hopefully be able to get the data needed to know precisely what is happening.

Below are three possibilities that occurred to me. I believe you have 10 panels with IQ8H-240-72-2-US, so each IQ8 is about 380W, or a 3.8 kW max system, currently set up with one Hoymiles and nine IQ8s generating around 3 kW peak.

1. Frequency shifting is occurring and all the microinverters (including Hoymiles) are throttled back. With 10 microinverters throttled back to 100 watts total, each should be outputting 10 watts, or 0.04 amps, which will be hard to get a good reading on. The load should be 0.4 (=100W/240V) amps. This is probably the best possible case (also means I need to replace my old meter which says there is no frequency shifting and eat a lot of crow on the forums ; -).
   
   
2. No frequency shifting is occurring and the IQ8s are throttle back such that each outputs 11 watts (100W/ 9 IQ8 microinverters) and the Hoymiles is outputting 300 Watts (1.25 amps) for a system total of 400 watts. Since the load is only consuming 100 Watts, the power out of the IQ8s would be voltage suppressed (e.g., the Hoymiles operating as a current source and the IQ8s as a voltage source) and the remaining 200 Watts would be backfed through the nine IQ8s (Mosfets are bidirectional), in which case the amps on the Hoymiles should be about 1.25 amps (probably closer to 1 amp, you'd need an on-grid reading to know the no-throttling value) and the current on the IQ8s should be 200/9 = 22W, or 0.08 amps - where the power is dissipated across the panel as heat (which isn't good for the panels and probably bad for the IQ8s). This is probably the worst possible case, although if the panels are bidirectional that means that any surge issues are further divided by the panels (good in that it reduces voltage magnitude of spikes, bad in that the panels are subject to them).
   
   
3. No frequency shifting, but the Enlighten load reading of 100W is wrong. The actual draw is 400 watts (that is Enlighten is reporting only the IQ8s output and ignoring the Hoymiles output). If that's the case the Hoymiles should be about 1 to 1.25 amps, the IQ8s around 0.05 amps, and the load about 1.6 amps.

I'm looking forward to the results because although those are the three things I can think of, I fully expect Murphy to provide a twist and it does something totally different and unexpected.

 

[ncsolarelectric]

Sweet! I'd suggest getting the amp reading of the Hoymiles output on-grid, and then the amp reading of the load and Hoymiles off-grid at the lowest wattage you can get (100 watts in your other test). Possibly an IQ8 output for scenario 2 below if the readings are unexpected.

When I saw the 100 watts in the video that just seemed wrong. It seemed the Hoymiles should be outputting 300 watts and at least one IQ8 had to be outputting power. If an IQ8 wasn't generating power, then the Hoymiles should have to go into anti-islanding and shutdown. With a clamp meter, you'll hopefully be able to get the data needed to know precisely what is happening.

Below are three possibilities that occurred to me. I believe you have 10 panels with IQ8H-240-72-2-US, so each IQ8 is about 380W, or a 3.8 kW max system, currently set up with one Hoymiles and nine IQ8s generating around 3 kW peak.

1. Frequency shifting is occurring and all the microinverters (including Hoymiles) are throttled back. With 10 microinverters throttled back to 100 watts total, each should be outputting 10 watts, or 0.04 amps, which will be hard to get a good reading on. The load should be 0.4 (=100W/240V) amps. This is probably the best possible case (also means I need to replace my old meter which says there is no frequency shifting and eat a lot of crow on the forums ; -).
   
   
2. No frequency shifting is occurring and the IQ8s are throttle back such that each outputs 11 watts (100W/ 9 IQ8 microinverters) and the Hoymiles is outputting 300 Watts (1.25 amps) for a system total of 400 watts. Since the load is only consuming 100 Watts, the power out of the IQ8s would be voltage suppressed (e.g., the Hoymiles operating as a current source and the IQ8s as a voltage source) and the remaining 200 Watts would be backfed through the nine IQ8s (Mosfets are bidirectional), in which case the amps on the Hoymiles should be about 1.25 amps (probably closer to 1 amp, you'd need an on-grid reading to know the no-throttling value) and the current on the IQ8s should be 200/9 = 22W, or 0.08 amps - where the power is dissipated across the panel as heat (which isn't good for the panels and probably bad for the IQ8s). This is probably the worst possible case, although if the panels are bidirectional that means that any surge issues are further divided by the panels (good in that it reduces voltage magnitude of spikes, bad in that the panels are subject to them).
   
   
3. No frequency shifting, but the Enlighten load reading of 100W is wrong. The actual draw is 400 watts (that is Enlighten is reporting only the IQ8s output and ignoring the Hoymiles output). If that's the case the Hoymiles should be about 1 to 1.25 amps, the IQ8s around 0.05 amps, and the load about 1.6 amps.

I'm looking forward to the results because although those are the three things I can think of, I fully expect Murphy to provide a twist and it does something totally different and unexpected.

5pm and no amp clamp yet, it's been raining and overcast all day.

Scenario #4. The Enphsae inverters are throttled back to zero. The HM attempts to push current into them but the voltage rises to the allowable limit at the array. At that point, the HM inverter throttles itself back to prevent the overvoltage and this inherently throttles down the current it's pushing to what the load can handle and stay in range. Unlike the APSystem's microinverters, the HMs have the ability to throttle their output. They comply with UL 1741-SA, so they can be phase controlled to deliver VARS as well.

I do not think frequency shifting is done to limit power. Frequency shifting is done to test for an island. Phase shifting is done to limit power by converting it to VARS, or amplitude modulation is done at 60Hz to lower the output current by controlling the amplitude of the reference in code. At least that's how I did it in 1993.

Also, regarding back feeding DC current into the panels. Yes, the panels act like 400W resistors that are dissipating maybe 30W each. It is not going to hurt them at all. They dissipate more heat than that just sitting in the sun doing nothing. It's silicon. Heat is not its weakness, brittleness is. Silicon is one of the most brittle elements there is.

 

[svetz]

Scenario #4. The Enphsae inverters are throttled back to zero.

You could be right that even throttled to zero they still output signal which would prevent the Hoymiles from going into anti-islanding. Can't wait to see the test results, most exciting thing I've seen on the forums in a while.

I do not think frequency shifting is done to limit power.

California (i.e., CA Rule 21), Hawaii (HECO 14H) , and Puerto Rico PREPA/PECO all say they have "limited grids" in relation to distributed energy sources and therefore the utility must be able to throttle back power from DERs to keep the grid stable. A DER is a Distributed Energy Resource, which is any grid-tied wind/solar/etc operation like you and me.

IEEE 1547 was modified to include a frequency-to-watt percentage to accommodate that, at 60 Hz you're allowed 100% output. So the power company, by varying the frequency, can control how many watts your panels output if the inverter is compliant.

UL 1741 is the Underwriters Laboratories inverter test standard and was updated to include the changes. So, it would actually be weird if the inverter testing standard didn't include the frequency shifting to throttle power requirement.

Unlike the APSystem's microinverters, the HMs have the ability to throttle their output.

AFAIK, APSystems are compliant with UL 1741-SA, so they should be able to throttle inverters too.

Frequency shifting is done to test for an island.

There are a lot of rules around this, simply put anti-islanding is also in UL 1741 and it should occur when frequency or voltage go outside of certain ranges for certain times. There are a lot of complicated rules on that.

Also, regarding back feeding DC current into the panels. Yes, the panels act like 400W resistors that are dissipating maybe 30W each. It is not going to hurt them at all. They dissipate more heat than that just sitting in the sun doing nothing. It's silicon. Heat is not its weakness, brittleness is. Silicon is one of the most brittle elements there is.

The 400 watts is power generation, not resistance. According to this:

...Most solar panels have an internal resistance of it’s about 3 ohms...

The cells act like diodes, but I'm not sure what would actually happen in that instance. On the one hand, if the microinverter is reversed you'd be running the DC in opposite polarity. But, because it's daytime, the photons would tend to push the current forwards. A single Hoymiles doesn't have enough watts to overpower 9 other panels, so I doubt there's any reverse flow. Pretty sure it creates heat, no clue what the impacts are or where it's really generated.

 

[ncsolarelectric]

You could be right that even throttled to zero they still output signal which would prevent the Hoymiles from going into anti-islanding. Can't wait to see the test results, most exciting thing I've seen on the forums in a while.


California (i.e., CA Rule 21), Hawaii (HECO 14H) , and Puerto Rico PREPA/PECO all say they have "limited grids" in relation to distributed energy sources and therefore the utility must be able to throttle back power from DERs to keep the grid stable. A DER is a Distributed Energy Resource, which is any grid-tied wind/solar/etc operation like you and me.

IEEE 1547 was modified to include a frequency-to-watt percentage to accommodate that, at 60 Hz you're allowed 100% output. So the power company, by varying the frequency, can control how many watts your panels output if the inverter is compliant.

UL 1741 is the Underwriters Laboratories inverter test standard and was updated to include the changes. So, it would actually be weird if the inverter testing standard didn't include the frequency shifting to throttle power requirement.


AFAIK, APSystems are compliant with UL 1741-SA, so they should be able to throttle inverters too.


There are a lot of rules around this, simply put anti-islanding is also in UL 1741 and it should occur when frequency or voltage go outside of certain ranges for certain times. There are a lot of complicated rules on that.


The 400 watts is power generation, not resistance. According to this:

The cells act like diodes, but I'm not sure what would actually happen in that instance. On the one hand, if the microinverter is reversed you'd be running the DC in opposite polarity. But, because it's daytime, the photons would tend to push the current forwards. A single Hoymiles doesn't have enough watts to overpower 9 other panels, so I doubt there's any reverse flow. Pretty sure it creates heat, no clue what the impacts are or where it's really generated.

Thank you. I need to upgrade my knowledge of 1547 and 1741-SA. I know what they were 10-12 years ago. I haven't kept up with the changes since I left CA. In NC, the rules are pretty slack outside of major cities.

 

[ncsolarelectric]

Damn if it didn't work like a charm! (Update 2:30PM - it did NOT work like a charm! It shuts down when on a microgrid. The rest of this post is what I saw, but I didn't check the status of the inverter itself. The flashing RED LED indicates an Invalid AC Grid. That is the state it was in below.)

I waited until my battery was fully charged and the system put out near full power. Then I reduced the load to 100-200W and switched to battery backup mode. The microinverters immediately throttled back their output INCLUDING the Hoymiles inverter. It went all the way down to 0.1A, with and without the Enphase PV microinverters in the circuit.

So 1 HM-350NT and 4 IQ8BAT inverters keep the voltage regulated at 240V, the HM only puts out 0.1A and the system seems to work fine. I don't know what the long-term effects would be, or what would happen if the ratio were the other way, but this actually seems to work without any export control. Nice!

Update: Maybe, with the speed of today's processors, the microinverter can calculate impedance and limit the output accordingly. It's a thought, because I didn't see it try to push the voltage higher, it just throttled back to what was needed automatically.

 

[svetz]

... the load to 100-200W ... microinverters immediately throttled back their output INCLUDING the Hoymiles... went ... to 0.1A,

240V x 0.1 amps = 24W. If the other 9 microinverters were throttled to 24W you'd be over 100-200W... but... that 0.1A could have been rounded up a teensy bit.

But at < 1 amp I'm sure the Hoymiles is throttled down. Wow! What a fantastic result! Kudos to you man, apologies if I sounded doomy/gloomy, was trying to state what I thought might be the worst-case scenarios to ensure you knew the risks. Guess I need to go find a spoon and a new meter.

Update: Maybe, with the speed of today's processors, the microinverter can calculate impedance and limit the output accordingly. It's a thought, because I didn't see it try to push the voltage higher, it just throttled back to what was needed automatically.

Now that's a thought! Possibly I don't need spoon or a new meter? You didn't by chance get a frequency reading on your AC did you?
Hmmm, now that I think about it, the meter API query shows frequency too:

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        "pwrFactor": 0.997,
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        "freq": 60.000,  // frequency
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        "instantaneousDemand": -1273.174,
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        "apparentPower": 1860.757,
        "reactivePower": -577.720,
        "pwrFactor": -0.675,
        "voltage": 245.906,
        "current": 15.116,
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        "channels": [
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[Ampster]

Damn if it didn't work like a charm

Unless I missed something, what you are saying is that the IQ8 with the System Controller 2 can act like a grid forming inverter and AC couple to any UL 1741 GT inverter. The remarkable part is that it was done without a battery. I suspect the modulation of the IQ8s is through PLC or other protocal and is fairly fast. I do not recall if you had any measures of frequency to determine how the Hoymiles micro ramped down. I wonder how much capacity in micros or other GT inverters could be added before the System Controller 2 had difficulty with AC coupling that capacity without having a battery as a buffer.

 

[ncsolarelectric]

Unless I missed something, what you are saying is that the IQ8 with the System Controller 2 can act like a grid forming inverter and AC couple to any UL 1741 GT inverter. The remarkable part is that it was done without a battery. I suspect the modulation of the IQ8s is through PLC or other protocal and is fairly fast. I do not recall if you had any measures of frequency to determine how the Hoymiles micro ramped down. I wonder how much capacity in micros or other GT inverters could be added before the System Controller 2 had difficulty with AC coupling that capacity without having a battery as a buffer.

It did have the battery and 4 IQ8BAT inverters in parallel to form the microgrid but I turned off the 9 IQ8+ on the panels. The battery was fully charged when I started. I've got a video to upload but it takes time to edit and I haven't started yet.

Determining the full capacity would be the next test, but I don't really want to disassemble all my panels to do it. I will get the DTU connected this Friday, I'm taking the 20-min. installer training webinar. (LOL!) Then I can see if the inverter puts out any alarms when operating like this. With just a DMM, I don't know for sure what is going on. I see 0.1A, it could be that the inverter has shut down completely and that is just the off-state current. I suppose I could repeat the test and go look at the LED on the inverter with a mirror, to see if it's red. Thanks!

 

[ncsolarelectric]

Okay, that settled it. The HM-350NT does NOT work on the microgrid. I tested it several different ways and it only works when the grid is present. When I thought it throttled back to 0.1A, it actually shut down completely due to an "invalid AC grid". I then added more load so that I could lower the impedance of the microgrid, but it still shut down completely. No-go, guys! I'm sorry. I'll keep investigating to figure out why not. I have an isolation transformer and other gear to play with. Thanks for the conversation, it helps to have more than one mind working on a problem.

 

[Ampster]

It did have the battery and 4 IQ8BAT inverters in parallel to form the microgrid but I turned off the 9 IQ8+ on the panels. The battery was fully charged when I started. I've got a video to upload but it takes time to edit and I haven't started yet.
........

I did not realize you had turned off the IQ8s and had a battery.

 

[ncsolarelectric]

Okay, that settled it. The HM-350NT does NOT work on the microgrid. I tested it several different ways and it only works when the grid is present. When I thought it throttled back to 0.1A, it actually shut down completely due to an "invalid AC grid". I then added more load so that I could lower the impedance of the microgrid, but it still shut down completely. No-go, guys! I'm sorry. I'll keep investigating to figure out why not. I have an isolation transformer and other gear to play with. Thanks for the conversation, it helps to have more than one mind working on a problem.

On one hand, it's not what I was hoping for. On the other hand, this makes it very easy to add Hoymiles microinverters to an Enphase array, because they won't affect the Encharge system. They just don't offer the added benefit of running in parallel with that microgrid (yet).

 

[Ampster]

They just don't offer the added benefit of running in parallel with that microgrid (yet).

I thought they were on the CEC list? Maybe that was prospective? If they are on the list I would assume that they would be CA Rule 21 compliant which also means they were UL1741SA compliant and should be able to respond to frequency Watt changes from the grid forming inverter. However that assumes the System Controller 2 can perform that function. Does any Enphase documentation talk about AC coupling to other GT inverters other than Enphase micros?

 

[ncsolarelectric]

I thought they were on the CEC list? Maybe that was prospective? If they are on the list I would assume that they would be CA Rule 21 compliant which also means they were UL1741SA compliant and should be able to respond to frequency Watt changes from the grid forming inverter. However that assumes the System Controller 2 can perform that function. Does any Enphase documentation talk about AC coupling to other GT inverters other than Enphase micros?

They are on the CEC list and they are UL1741-SA compliant, but it requires feedback on MODBUS from a meter to the DTU to make it work. My meter is on order, I was testing it raw, unregulated by a meter or the DTU. I posted that info here a couple of pages ago.

 

[Ampster]

but it requires feedback on MODBUS from a meter to the DTU to make it work. My meter is on order, I was testing it raw, unregulated by a meter or the DTU. I posted that info here a couple of pages ago.

Yes, I saw that but did not understand why you were going that route if they were UL 1741 compliant. However, I realize that one can not make the assumption that the System Controller 2 in conjunction with the IQ8s to use frequency Watt as the control mechanism as a generic AC coupling algorithm would do it.

Does any Enphase documentation talk about AC coupling to other GT inverters other than Enphase micros?

So that question remains. If the System Controller 2 in conjunction with the IQ8s can use frequency Watt modulation to control any GT inverter you would not need to use the meter because if the Hoymiles are Rule 21 compliant they could be modulated by the frequency Watt changes of the grid forming inverter. if the System Controller 2 can indeed do that.

 

[Ampster]

I found this document that seems to suggest that the System Controller 2 cannot use the typical frequency Watt modulation to control GT inverters. It says, " ...the Enphase AC Battery or Enphase IQ Battery are not grid forming, AC coupling of these storage solutions is not covered in this document."
I think they use the term, "grid forming" in the context of AC coupling. You clearly demonstrated that it can form a microgrid.
Sorry about the digression. I understand it better now,

 

[ncsolarelectric]

I found this document that seems to suggest that the System Controller 2 cannot use the typical frequency Watt modulation to control GT inverters. It says, " ...the Enphase AC Battery or Enphase IQ Battery are not grid forming, AC coupling of these storage solutions is not covered in this document."
I think they use the term, "grid forming" in the context of AC coupling. You clearly demonstrated that it can form a microgrid.
Sorry about the digression. I understand it better now,

That document is from 2018, long before the IQ8.

Funny thing is, I have a video from this morning where the HM-350NT was definitely running on the microgrid, putting out full available power at 240W while the battery was charging. It worked with and without the other Enphase inverters connected. The HM would drop to 0.1A and then come back up to 1A. So I have evidence that it works when the Encharge battery is low (< 50%) and charging. This afternoon, however, when the battery was fully charged and I switched it to the microgrid, the HM inverter shut down with an Invalid AC Grid fault. I need to do more testing.

 

[fromport]

That document is from 2018, long before the IQ8.

Don't forget that all enphase batteries have 4 IQ8X-BAT-US microinverters inside.
They worked on iq8 for storage first before releasing the iq8 for under PV panels as a separate product. Micro grid forming is really an IQ8 only quality.

 

[svetz]

Okay, that settled it. The HM-350NT does NOT work on the microgrid.

It would help to understand the configuration, what precisely was done, and the results. Sounds like it worked earlier, then didn't work?
Was the battery fully charged? I've noticed on mine that the battery needs to be around 96-97% before it'll turn the microinverters on at low-load.

 

[ncsolarelectric]

It would help to understand the configuration, what precisely was done, and the results. Sounds like it worked earlier, then didn't work?
Was the battery fully charged? I've noticed on mine that the battery needs to be around 96-97% before it'll turn the microinverters on at low-load.

I'm going to repeat the test more thoroughly tomorrow. Two possibilities. 1. It worked in the morning while the battery was charging. Or 2. It didn't work and draws about 1A of reactive current while in the "Invalid AC Grid" fault condition. Which fooled me into thinking it was putting out 240W in the earlier test.
Tomorrow, if there's sun, I will verify that the inverter is operating normally, and if it's in the fault condition, I will measure the current and see if it is still 1A whilst in that condition.

 

[ncsolarelectric]

I'm going to repeat the test more thoroughly tomorrow. Two possibilities. 1. It worked in the morning while the battery was charging. Or 2. It didn't work and draws about 1A of reactive current while in the "Invalid AC Grid" fault condition. Which fooled me into thinking it was putting out 240W in the earlier test.
Tomorrow, if there's sun, I will verify that the inverter is operating normally, and if it's in the fault condition, I will measure the current and see if it is still 1A whilst in that condition.

Option 2 it is. When running on a microgrid, the HM inverter shows an "Invalid AC Grid" fault and does not output power regardless if the battery is charging, or discharging, or loaded, or unloaded, up to my available load.

This is great news in that, without a DTU or feedback, I can connect HM inverters to an Enphase system and probably any other grid-tied system, without them interfering with or damaging the Enphase microgrid. The HM inverter goes into standby until the grid comes back + 5 min. This allows me to upgrade systems for less than half the cost of adding more Enphase inverters. Nice!

This is bad news for anyone who wanted to use these in parallel with their off-grid system. I don't have any other off-grid inverters to test it with and I can't afford an EG4 or MPP inverter. Anyone out there who would like to try it, LMK. Maybe Will would like to try it on his system?

 

[svetz]

Frankly, I'm surprised they stay in anti-islanding mode. The Enphase microgrid has characteristics indistinguishable from the grid, so how would they know? I can see it at the beginning of a test during the switch over or 10-15 min afterwards, but after the time-out period it should be indistinguishable. Possibly when the HM resets it causes an instability? If so, you'd see the error repeat every 5 minutes or so. At least it doesn't seem to cause the IQ8s to become unstable.

 

[ncsolarelectric]

Frankly, I'm surprised they stay in anti-islanding mode. The Enphase microgrid has characteristics indistinguishable from the grid, so how would they know? I can see it at the beginning of a test during the switch over or 10-15 min afterwards, but after the time-out period it should be indistinguishable. Possibly when the HM resets it causes an instability? If so, you'd see the error repeat every 5 minutes or so. At least it doesn't seem to cause the IQ8s to become unstable.

Me too. It must have something to do with the stiffness of the microgrid. The waveform and voltage of the Enphse microgrid are superb. But if the HM can perturb my little 1.28kW microgrid, then it will go into anti-islanding mode. It may work on a 6.5kW or a 12kW system where the microgrid is stiffer. Perhaps it is just that the IQ Battery 3T + 9 IQ8+ inverters are not enough to make the HM inverter thinks it's on the real grid

 

[ncsolarelectric]

From the HM tech support, it is unlikely that these inverters will work on a microgrid. The anti-islanding protection can detect it and will shut down the microinverters. They didn't suggest any means to prevent it. However, they have a new product that is an AC coupled hybrid battery inverter + battery that will be released at SNEC in September and will be available in North America near the end of the year, or early 2023.

Also, I got the DTU setup and working in no time. Here's a screenshot of today.

Update, I like that I can see the output of the module on the DC side too! This is a Jinko 400W Mono PERC module, but the sky has some high-altitude haze, preparing for afternoon thunderstorms.... again.