Enphase AC to hybrid system
- Thread starter amanra13
- Start date
I was told that the battery settings don't apply when running off grid ac coupled, so what settings could be causing the frequency to shift. I saw it shifting from 60.1 to 60.9hz. Using the CA grid profile and enabling state of charge in charge settings it went up to 5 amps. Because it kept changing to 60.1hz not all of the inverters would stay on, in the last try I had 32 inverters running. I thing only 9 were putting out power.
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,702
32 iQ7 inverters is certainly pushing the limit of what a single XW-Pro can handle on the output. That is a potential of over 7,600 watts. The XW-Pro recommends less than 6,000 watts of AC coupled solar. With the small load on the system and that much solar power, it may very well have been causing the system to go unstable. Try turning off some of the iQ7's to get it down under 6,000 watt. I would say 24 is about the limit.
SoC control requires either a Schneider Battery Monitor, or a BMS that can communicate with the XW-Pro. Without those, you have to use voltage control.
What are your batteries again? When doing AC coupling, Schneider recommends that your battery can accept the full power of your solar array. At 6,000 watts of solar, that means a charge current of around 120 amps or so. The XW-Pro will try to frequency shift to control the maximum current, but as we have seen, it may not be able to hold control, and some of the iQ7's will shut down from time to time. If your batteries are lithium, you should probably set the temp compensation to zero. I see you have the maximum charge rate set at 60%, that would be about 84 amps. Your software is a bit different from mine, I don't have a separate line for actual charge current values in amps.
Are you trying to do daily cycling on grid, or just backup power and able to run off grid?
SoC control requires either a Schneider Battery Monitor, or a BMS that can communicate with the XW-Pro. Without those, you have to use voltage control.
What are your batteries again? When doing AC coupling, Schneider recommends that your battery can accept the full power of your solar array. At 6,000 watts of solar, that means a charge current of around 120 amps or so. The XW-Pro will try to frequency shift to control the maximum current, but as we have seen, it may not be able to hold control, and some of the iQ7's will shut down from time to time. If your batteries are lithium, you should probably set the temp compensation to zero. I see you have the maximum charge rate set at 60%, that would be about 84 amps. Your software is a bit different from mine, I don't have a separate line for actual charge current values in amps.
Are you trying to do daily cycling on grid, or just backup power and able to run off grid?
newbostonconst
Solar Enthusiast
- Joined
- Sep 24, 2019
- Messages
- 1,004
My guess looking at the charts is that the battery voltage is getting to high and the inverter is cutting power requirement back and is shutting down the microinverters.
Do you have anything to put a load on the batteries to get the voltage back down and see if it stops freq shifting?
Do you have anything to put a load on the batteries to get the voltage back down and see if it stops freq shifting?
This system is for off grid power, I have only used it once since I installed. Most of the time my loads are small, my average usage is about 2000 watts. I have my panels in strings of 16 and can either have them on or off, I have 4 strings, the most each string puts out is 3000 watts and most of the time when I am testing they are less than 2000 watts. It doesn't seem to matter what my loads are or my power coming in is. It will power my load and maybe charge the battery, but the most I have gotten is 5 amps. I have the Schneider battery monitor and I am on the latest firmware for the XWPro and the Insight. The batteries are 121 of the Nissan leaf lithium batteries from three cars, according to the specs they can handle up-to 120 amps, I think that is too much and I try to limit it to 60 to 80amps for charging, as far as discharging they seem to handle all of the power that the XWPro can produce. The XW all ways frequency shift and limit the incoming power, I tried several experiments over the weekend and only managed to charge the batteries one time, and that was at 5 amps. It all ways limit my power to just about my loads and then pulls a little bit out of the batteries, this is what happened to me 6 weeks ago when the power was out for 4 days. My batteries never charged from the solar and pulled my batteries down to far, I ended up hooking up my generator through the XW and charged them back up.
How do I get my battery volt down or how do I adjust the XW to not cause the voltage to frequency shift. I feel that I have a large batter bank of about 1000ah. And again 32 Enphase is at most 6000 watts on my system. And 84 amps of charging is where I would like to be, just never get there. And this is just off grid for power down situation, basicall I am trying to replace my gas generator with this battery generator.
How do I get my battery volt down or how do I adjust the XW to not cause the voltage to frequency shift. I feel that I have a large batter bank of about 1000ah. And again 32 Enphase is at most 6000 watts on my system. And 84 amps of charging is where I would like to be, just never get there. And this is just off grid for power down situation, basicall I am trying to replace my gas generator with this battery generator.
newbostonconst
Solar Enthusiast
- Joined
- Sep 24, 2019
- Messages
- 1,004
The one chart show you are charging at 56 volts. This is at the limit for the normal 48 volts your invert is designed for.... I am thinking the unit is limiting itself because it is near its max voltage. Can you easily eliminate one cell group from your battery and try that?
Just ideas and trying to help. Good Luck.
Just ideas and trying to help. Good Luck.
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,702
Oats49250,
I have an idea for a little experiment for you.
Shut off all of the strings of Enphase, while the sun is still down in the early morning. This will cause all of the inverters to fully power down and reset.
Then run some load, about 1,000 watts or so, from the batteries through the XW-Pro. Once the batteries run down to below 54 volts, about 3.86 per cell or less, assuming you are running 14S, then turn on the breaker to just one string of the Enphase inverters.
Then watch the dashboard screen from the XW-pro. You should see the 1,000 watt load initially coming out of the battery to the XW-Pro, then going up to the house. Then as the solar comes online, after the normal 5 minute delay, the power going out should reduce by the amount the solar is producing. If the one string is not enough, it may still be consuming from the battery bank. Compare how much the flow to the house dropped to when the Enphase solar is reporting for energy produced. The Enphase Enlighten does not update for at least 15 minutes. Give it some time to actually get a graph, or open the Enphase installer toolkit and connect to the local Envoy. The toolkit gives a near live power being produced readout. I think you can also get that by entering the ip address of the Envoy into a web browser on the local network. I just tried this on mine and it shows "Production 1.02 kW at 8:41 am" right at the top pf the page, no login needed to see that.
Let it run like this, just one string for a bit and see what it does. As the sun comes up, your single string should start to produce more than your load, but if not, try adding just a second string. It will again take about 6 minutes before the inverters start producing. Try to use just enough panels to get it to charge instead of discharge. Watch the battery current and voltage. Ideally we want the current below what you set for maximum, and the voltage still more than 2 volts before your absorb voltage limit. That should stay running without frequency shift. If it does that, let it run for over an hour and then take a snapshot of the battery summary plot.
If things are acting up, and it keeps tossing the iQ7s offline, then there is a problem. If it stays online and charging, then add another string and see what happens. I really think you are just getting to a point where you are overpowering the XW-Pro and it has o limit the solar coming in. Let us know what this does.
I have an idea for a little experiment for you.
Shut off all of the strings of Enphase, while the sun is still down in the early morning. This will cause all of the inverters to fully power down and reset.
Then run some load, about 1,000 watts or so, from the batteries through the XW-Pro. Once the batteries run down to below 54 volts, about 3.86 per cell or less, assuming you are running 14S, then turn on the breaker to just one string of the Enphase inverters.
Then watch the dashboard screen from the XW-pro. You should see the 1,000 watt load initially coming out of the battery to the XW-Pro, then going up to the house. Then as the solar comes online, after the normal 5 minute delay, the power going out should reduce by the amount the solar is producing. If the one string is not enough, it may still be consuming from the battery bank. Compare how much the flow to the house dropped to when the Enphase solar is reporting for energy produced. The Enphase Enlighten does not update for at least 15 minutes. Give it some time to actually get a graph, or open the Enphase installer toolkit and connect to the local Envoy. The toolkit gives a near live power being produced readout. I think you can also get that by entering the ip address of the Envoy into a web browser on the local network. I just tried this on mine and it shows "Production 1.02 kW at 8:41 am" right at the top pf the page, no login needed to see that.
Let it run like this, just one string for a bit and see what it does. As the sun comes up, your single string should start to produce more than your load, but if not, try adding just a second string. It will again take about 6 minutes before the inverters start producing. Try to use just enough panels to get it to charge instead of discharge. Watch the battery current and voltage. Ideally we want the current below what you set for maximum, and the voltage still more than 2 volts before your absorb voltage limit. That should stay running without frequency shift. If it does that, let it run for over an hour and then take a snapshot of the battery summary plot.
If things are acting up, and it keeps tossing the iQ7s offline, then there is a problem. If it stays online and charging, then add another string and see what happens. I really think you are just getting to a point where you are overpowering the XW-Pro and it has o limit the solar coming in. Let us know what this does.
I can try that and see, wouldn't be to hard but the spec sheet for the inverter states that the DC voltage range is from 40 – 64 V (48 V nominal).
I think why they recomend that voltage is if I drop one group the max charge voltage would be 48.6 to 49 volts.
I can try this, will have to wait till I have a morning to try this. I can say that I have did this when my power was out for 4 days, what I was getting is the same. Enphase will power my loads but always draws a little out of the battery. But when the Enphase power starts to exceed the load the inverter starts frequency shifting. What is disappointing with this is Schneider will no longer help me and they wont replace or return my inverter.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,522
For my SMA string inverters, default frequency range is 59.4 to 60.5 Hz. That is the standard in-spec frequency range, so your microinverters shouldn't go offline below 60.5 Hz.
Start at that frequency (or higher), would like power output to ramp down with frequency. Mine are 100% at 61 Hz ramped down to 0% at 62 Hz.
If your microinverters do frequency-watts, there should be a similar range of frequency where they ramp down output.
There could also be frequency shift rate, Hz/second that the tolerate, and that the Schneider produces. My battery inverter takes several seconds to swing frequency, easy to watch with hand-held meter. It has to source/sink power while waiting or PV inverters to respond.
When I used a PV inverter that didn't respond correctly, frequency continued to rise until it was knocked offline, then frequency ramped back down.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,522
For my SMA string inverters, default frequency range is 59.4 to 60.5 Hz. That is the standard in-spec frequency range, so your microinverters shouldn't go offline below 60.5 Hz.
Start at that frequency (or higher), would like power output to ramp down with frequency. Mine are 100% at 61 Hz ramped down to 0% at 62 Hz.
If your microinverters do frequency-watts, there should be a similar range of frequency where they ramp down output.
There could also be frequency shift rate, Hz/second that the tolerate, and that the Schneider produces. My battery inverter takes several seconds to swing frequency, easy to watch with hand-held meter. It has to source/sink power while waiting or PV inverters to respond.
When I used a PV inverter that didn't respond correctly, frequency continued to rise until it was knocked offline, then frequency ramped back down.
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,702
My thinking on this problem is that there may be a bad connection somewhere, or a BMS issue. Using the lower amount of power may show what is really going on. If there is a weak connection somewhere in the battery to inverter system, then the apparent voltage will climb with charge current. If the voltage goes too high, then the system goes into frequency shift as it sees the battery becoming full. Starting with a single string as the sun comes up should show if the system is stable as the power ramps up. Looking at the battery summary plot above, I do see the battery voltage changing nearly 0.5 volt for a 60 amps change in current. That works out to 0.008 ohms, or 8 milliohms, which does not sound too bad, but it is quite a bit more than my system is showing. Back when I had my power failure and it went off grid, it went from 23 amps charging to 18 amps discharging. That is a 41 amp swing, and the battery voltage only moved 0.17 volts. 0.17 / 41 = about 4 milliohms, and that was with just my single 360 amp hour battery bank and one JK-BMS handling all of the current.
The Enphase do frequency shifting, the problem is the Schneider shifts to much and shuts them down, instead of putting the power into my batteries.
So could there be a resistance problem? Could my resistance be to high? Can I measure that somehow?
newbostonconst
Solar Enthusiast
- Joined
- Sep 24, 2019
- Messages
- 1,004
Where are your micros tied into? Your main panel? or sub panel at the Schneider?
What are wire sizes in between the micro's and Schneider?
What are wire sizes in between the micro's and Schneider?
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,522
It should shift and just keep shifting until power hits desired amount. Mine takes a few seconds to shift and GT PV inverters respond immediately. Could be the battery inverter shifted at a rate faster than PV inverter thought was acceptable, so it drops off. Are you sure your microinverters are ramping down power? If you have an AC clamp meter and the shift is slow enough you should be able to watch that.
There may be some parameter settings that work better.
I was looking for numbers like rate of change Hz/second, which I haven't found, but I did find this. Says for off-grid, so PV inverter settings wouldn't be UL1741, but does XW take care of disconnecting them from grid when necessary? Does XW perform anti-islanding? I don't know, but my Sunny Island does. One of my Sunny Boy models I had to set to "offgrid" when running behind Sunny Island, but now I'm using models which work correctly set to "backup".
"For off-grid: As a second option, when it is not possible to set the battery and PV inverter to the same grid code, it is recommended to disable Freq-Watt P(f) Droop and Freq-Watt P (f) PreDist on the battery inverter (Figure 6) in Grid Codes settings. The smart AC-coupled PV inverter's P(f) curve should be set to start active power reduction at nominal frequency 50/60 Hz and finish it (fully reduce to zero) at 54/64 Hz. This is what the battery inverter frequency shift is configured to in case when grid code P(f) is not activated on it."
"2. Select the appropriate region grid code from the Select Region pulldown menu. a. For grid interactive systems, the appropriate grid code is specified by the utility in their interconnection rules. b. For AC-coupled systems, ensure that the AC coupled PV inverters are set to the same grid code. c. Note, off-grid systems may typically use any of the grid codes. For off-grid AC coupled systems, the California Rule no. 21-2018 grid code is recommended for the XW Pro and PV inverters"
"3. Verify that each inverter accepted the correct Grid Code Region by navigating to Devices -> (inverter) -> Grid Codes"
It did take me a couple tries to get parameters accepted by my Sunny Boys (operator error?)
Sub panel on the out side of my barn. That panel feeds my barn and my house. The wire size in that panel is 2 gauge feeding the Enpahse panel and the Barns panel. I have 4/0 feeding the house.
