Adding storage to my Enphase system

[GXMnow]

So I have a new issue...



I got up this morning and I like to check how low the battery went. WOW!!! What happened?

I doubt this was my PLC. It does not try to adjust charge current before 6 am. This started happening shortly after 5 am, I was still asleep. Discharge current shot from 9.44 amps to 74.33 amps. At 53.26 volts, that works out to over 3,900 watts at 5:07 am. The current tapers off to 51 amps after 3 minutes, but then the XW switches to charge mode, pushing 19 amps. But then it swings more and more for 90 minutes. The peak discharge rate hit 88.48 amps at 52.38 volts for over 4,600 watt at 6:13 am. It was just a short peak, but if only my normal overnight house load was running, that could be an export of close to 4,000 watts. That may have just exceeded my 16 amp export limit. It was short, and the 20 amp breaker obviously didn't trip. The highest charge current peak hit 56.64 amps 53.34 volts just over 3,000 watts at 6:15 am, that is after my PLC would normally start adjusting the current. The last of this event ended at 6:42 am and the PLC resumed proper export power control and zeroed the export power properly again. And it smoothly transitioned into charging current control as the sun rose about 8:40 with no sign of any issue.

And once again, there is no entry of any issue in the event log. But it sure looks like the grid was coming on and off that whole time. But with no solar coming in, it was going into charge each time the grid came back? But then it stayed out of charge once the grid was stable? That's not what it usually does? This is just odd?

I just looked at the "Energy Comparison" chart.


This only shows the full hour totals, but it is still pretty telling. The output back to the grid went from just 66 watt hours in the 4 am hour to 792 watt hours in the 5 am hour and 698 watt hours in the 6 am hour. But then back to nothing in the 7 am hour. Grid input (consumption) also went way up, from nothing overnight to 639 watt hours at 5 am and 691 watt hours at 6 am. But if you look at the net grid power, the total for the 2 hours is still just 160 watt hours, or 0.16 kilowatt hours, so the total power was really nothing.

The battery energy is really odd.
My system typically discharges between 700 and 1,200 watts through the night as things cycle on and off. So all the hours up to 4 am are in the range, discharge only, no charging. But then the 5 am hour has a discharge of 1.5 KWHs AND a charge of 0.448 KWHs. Net just over 1 KWH of discharge, which is about normal. And the same happened in the 6 am hour. 1.4 KWH of discharge, and 0.508 KWHs of charge.

I will do another Gateway reset and see if anything shows up in the event log.

 

[GXMnow]

Completed the Gateway reboot at 10:37 am.

No new event entries. Last events are the 12 and 14th that triggered the charging. So odd.

 

[400bird]

Someone else here reported a similar issue. Mine did it once in the wee hours of the morning. Something like 2 am and lasted about 2 hours, just like yours.

I have no idea where to go looking. I'm thinking it has something to do with grid frequency. Maybe the XW reacted to the grid frequency changing?

 

[GXMnow]

So this was interesting.

It was about 5:15 pm, it is still sunny, but at a very low angle, the Enphase panels are making just a tick more power than the house needs, so I am exporting a small amount of power, looks like about 500 watts right now. The XW is showing in "Grid Sell" but it's not selling anything. Here is the Status page in Advanced mode


You can see my current imbalance with L1 exporting 4.3 amps while I am importing 1.7 amps on L2. Sitting basically idle, the battery current is just 48 watts. The Victron charge controller is sitting in Float, pushing about 300 watts, so the batteries are seeing a small bit of charge current still.

While I was looking at this page, my eye caught a green flash in the grid of "Active Grid Support Features", but that first time it was too shar ofr me to figure out which one lit up. I watched it for a few minutes and saw it happen 3 more times. It lit up the top middle one "Freq-Watt Under Freq". With the page scrolled as I had it, I can see the grid frequency in 2 places, and both of them never changed from showing just "60" with no decimal showing. So I am not really sure what all is going on there.

Not sure if this will be the final layout, but I think it looks pretty good. I added a strip of Panduit wire duct under the charge controller. The pipe through the wall pokes through the back of the Panduit, so it is totally hidden now.

The black cable out the bottom is the Spectrum cable modem COAX. It was just tacked to the wall, it goes up on the left side of the XW and across the ceiling joists. The grey lead dropping out on the left side is the battey temp sensor from the XW. It's on the top battery module in my old battery bank.

The Victron now has the #6 awg wire in all openings. It's a tight fit.


My neighbor to the east has a tall palm tree, it's now casting a morning shadow onto my DC array.



My tree you can see off the corner of the garage is no issue. It's shadow is in my driveway. I am hoping it gets a little warmer and I can complete getting the wire up on the garage roof all into the conduit and tied up nicely under the panels. I have all of the materials. But it is windy an cold on the roof except when I need the DC panels making power. If I get everything lined up, I think I can move the wiring into conduit in about 1 hours of down time. Once it is over 65F out on my roof.

 

[GXMnow]

Sure enough, right as I sent the previous reply, I look over and the "Freq-Watt Under Freq" was lit, and I caught it with a screen capture.



And this time, it stayed for a bit and is showing 59.9 Hz.

 

[svetz]

Does California have enabled the "request for renewable energy" by drooping the frequency? I thought that was still in the discussion stages? If so, do you get special rates?

Or, is this just a situation where the grid is low on energy causing the dynamos to slow due to the extra drag?

I still haven't seen anyone post what they were really worried about (needing to cut out residential solar which they do by over-frequency).

 

[GXMnow]

Does California have enabled the "request for renewable energy" by drooping the frequency? I thought that was still in the discussion stages? If so, do you get special rates?

Or, is this just a situation where the grid is low on energy causing the dynamos to slow due to the extra drag?

I still haven't seen anyone post what they were really worried about (needing to cut out residential solar which they do by over-frequency).

I don't think the frequency dips are anything intentional. My guess is it is just load not being compensated fast enough.

My XW just did a smaller version of the odd charge/discharge swings. But this time it was much shorter in duration and the current did not swing as far. As the sun is not up yet, it was inverting from battery pulling about 10 amps, about 550 watts to run the basic house loads. But at 6:14 am it switched to charging at 17.6 amps, then discharging at 64.7 amps at 6:15 am, only 1 minute later?? At 6:17, two minutes later, it's back to charging at 13.9 amps. Another 2 minutes, and it's discharging at 62.9 amps. Then just 1 minute, it goes to charging at 6.9 amps. Only another minute and back to discharging at 46 amps, then 2 minutes until charging at 30.6 amps. Then the final spike of discharging at 66.8 amps. And just 1 minute later, it is back under my PLC control, pulling about 12 amps to run the house loads again at 6:25 am.

The total time from going off the rails to back in control was under 12 minutes. I wish I was watching it a little sooner to see this in action. I noticed it about 10 minutes after the spikes stopped. But looking at the PLC data, I really doubt it was doing this. While it can issue commands in well under a minute, the rules I set for starting and stopping a charge cycle do not allow it to swing like that. I require a fairly large swing in the available solar vs loads before it will reverse like that. This must be happening directly within the XW-Pro/Gateway. My guess again is that it is trying to stabilize wandering grid voltage/frequency issues. As big as the charge spike were, they only put 76 watt hours into the battery, but took out more like 200 watt hours. In the 12 minutes, it was exporting battery to grid for 5-7 minutes while charging from grid for about the same total amount of time. It smooths the graph to full minute steps, so it is likely about 6 minutes of each. But the discharge power was double the charge power. Here is a zoom in of the graph.

 

[GXMnow]

I have a theory.

The utility is adjusting the grid voltage.

I have only seen this happen a few times, always in the early morning, and only when exporting to the grid. The way the XW inverter works, it is acting as a voltage source, using the resistance to the grid to produce the export current I am asking for. It's not really a current source like a typical grid tied inverter.

Think of this like DC power. The grid is a giant battery, and my XW is a tiny battery. There is a small resistance between them, and to produce an export current, my XW battery is at a tiny bit higher voltage. Lets say it is 0.1 ohms, and I am exporting at 3 amps, so the voltage difference is 0.3 volts. But then the grid voltage changes, increasing by 1 volt. Now, instead of exporting by 3 amps, I am importing by 7 amps. The XW senses this difference, so it ramps the voltage to adjust, but it over shoots by a little, causing a bit too much export for a second, and as it comes close to the right setting, the voltage again moves a little further. The process repeats. Any time the grid voltage rises, my system momentarily goes to charging, taking some energy from the grid. If the grid voltage drops, it will increase the export current, until it can adjust to the right level again. I think this is why it makes that wave, and is always hunting back to the current my system was set for. It never stays at the large import or export power, it it just a peak.

What do you think? Does this seem likely?

P.S. It happened a second time at 6:30 this morning.

 

[Hedges]

Your inverter pushes power into the grid regardless of grid voltage, should only be maybe a glitch if grid voltage changes.
Except at some voltage limit where inverter is knocked offline, or does volts-watts.

UL-1741-SA allows wider voltage (and frequency) range, but has limited time ride-through.
Also allows optional ramp-down of power in response to frequency or voltage.

If any of that is happening, you ought to have inverter grid settings grid voltage parameters in the range where inverter is supposed to respond.

If your inverter is set for a particular amount of export, then the control loop could respond in mysterious ways.

I've watched my SBS ringing up and down with several second time constant.

 

[GXMnow]

I'll keep an eye on it, but so far, as odd as it looks, it is not causing a big problem. My battery bank has no issue dealing with the 80 amp charge swing. And as long as they net meter based on the full hour average, it is cancelling out.

I am 99.9% sure, it is nothing I am doing. It's not the PLC causing this. IT is something between the grid and the XW-Pro inverter.

 

[GXMnow]

Check this out.



It is shortly after 3 pm, the battery is full, and the sun is still shining strong. The Enphase panels are making a lot of power, so much that I am exporting over 3,000 watts to the grid. AC1 active power 3,016 watts, with 15.4 amps to L1 and 12.2 amps to L2. But, the frequency is low, so the XW is trying to "Help" it's pulling just 1.5 amps from the battery to export an additional 86 watts. When the "Freq-Watt Under Freq" turns off, the batery current falls back to zero, or even charging a tiny bit. But each time I see that flag light up, it pulls some battery current.

Here it is a couple minutes later, not correcting for frequency. A cloud also moved in so the back feed current dropped to just 1,342 watts.

DC power went from -86 watts to +44 watts.

If every XW on the grid is doing this, maybe it could help stabilize the grid.

 

[faccnator]

That has to be a setting right?

 

[GXMnow]

That has to be a setting right?

I am pretty sure that is part of the "CA Rule 21" Grid Code. The inverter was in "Grid Sell" mode, but I was only commanding it to export about 300 watts to cover loads in my main panel. Normally, about 20 watts extra would be going to the grid. But at that time, the AC coupled Enphase solar was already back feeding around 3,000 watts. Since my battery was already full, I dropped out of charge mode and with my grid tied inverters covering all mode loads and then a lot more, the XW-Pro battery inverter would normally just sit idle until the sun went down. But here it is, pushing out an extra 86 watts. A tiny drop in the bucket. But the AC frequency was low by less than 0.1 Hz. Any time the grid went back to 60.0 the current draw from the battery would stop.

 

[Hedges]

0.1 Hz shouldn't be curtailing based on Rule 21 or -SA.
Original UL-1741-SA considered grid in-spec from 59.3 to 60.5 Hz. I think the frequency-watts ramp down is from 60.5 to 61 Hz.

Variations in measurement error might have more to do with it.

In your screen shots, all I ever see is 60 Hz. But some have "freq-watt under freq" highlighted in green.

 

[GXMnow]

In your screen shots, all I ever see is 60 Hz. But some have "freq-watt under freq" highlighted in green.

In post #1,765 it dropped enough to show as 59.9 Hz.
I agree, it is going active very early. But I can see it happening. It is a very tiny amount of current. 86 watts at 240 volts is 0.358 amps. That is about my minimum static load back in my main panel. I just had a little fun since I wanted to heat up a Pretzel dog anyways.

Here is the screen, with my PLC monitor window. The PLC window is not very user friendly. In the simulated LCD window, you can see the Batt Volt at 57.670 and in the XW DC voltage readout, it rounds it to 57.7 volts. The Solar panels are nearly done making power, and I am starting to use some battery. This is my base load in my main panel, it is small. The XW window shows it as 88 Active Watts with a -0.9 power factor. My PLC asks just for Watts and it is showing 107. Battery watts is -670 in the XW window, and -664 in the PLC window. Again, the XW is rounding it off. I am not showing the lower section, Output of the XW. But the PLC is showing the output side running at 521 watts. That is my refrigerator, lights, this PC etc.

In the PLC green window on the left side, variable "U" is the current the PLC is telling the XW to send back to the main panel. In this snap shot it shows 391. That is milliamps of grid sell current.


And if you look in the XW window below th PLC screen, you see AC1 active current 0.4 amps, again, rounded from 0.391 to 0.4 amps.

Now I press start on the microwave oven, which is currently plugged into an outlet off of the main panel, not the backup loads. This places about a 1,700 watt load in the main panel.



Now we see the variable "U" in the PLC is now calling for 7,745 milliamps to the main panel. And if you look at the AC1 Active Current, there it is 7.7 amps. But that is at 240 volts. The microwave is only on L1. 10.5 amps are going out L1, and 5.4 amps are going out L2. Most of the L2 current is going to the utility transformer and coming back in to help power the oven at nearly 15 amps total on L1 in the main panel.

I am actually very surprised it works as well as it does like this. And the power meter totally ignores the phase imbalance. I have had it exporting over 15 amps on one leg, and importing over 14 amps on the other, and it shows just like 50 watts going out to the grid. I just hope they never change the meters to read the current of L1 and L2 independently.

 

[Hedges]

Power meter may even sum magnetic fields from L1 & L2, not measure them separately. Therefore can't distinguish wattage difference when voltage differs.

Could be what you're seeing is just due to voltage delta. You might figure out it was trying to be zero but calculating inaccurately, or something like that.

 

[GXMnow]

Today has been interesting. The weather just can't make up it's mind. It went from clouds to sunny, to drizzle, back to sunny, and now back to clouds. I was out in my garage and I heard the XW-Pro hum get pretty loud, I look up and it's charging at over 50 amps with the extra energy coming in from the Enphase system. Out of curiosity, I open the Victron Ap and WOW! The 2,000 watts of DC panels is producing 2,000 watts and the Victron 150-35 is clipping at 35 amps. The air was cool, there was a little wind, the clouds parted to let direct sunlight on the panels, and there were nice white clouds reflecting light on the panels as well. The condition didn't last long, but it was certainly real. And yes, I checked in the Enphase logs, and all 16 panels also hit clip at 245 watts. But since it was only for 3 minutes, it does not show on the 15 minute bars.



Looks like it was up there for about 3 minutes. That pushes my total charge current up to 85+ amps. Not a problem for my battery bank, and it's great to see it cranking like that. Too bad it can't keep it up. Clouds moved in and the DC system has been under 18 amps since.

 

[400bird]

Today has been interesting. The weather just can't make up it's mind. It went from clouds to sunny, to drizzle, back to sunny, and now back to clouds.

I'm pretty sure the rest of the country calls this phenomenon "spring"

Otherwise, sounds like those panels are working great!

 

[GXMnow]

And now my DC system has produced the most it ever has in a single day. We had 2 bad days of production, so the battery was right down to my normal 50.5 volt cut off, and it was not a super sunny day, so the Enphase system didn't top it up too quick. So that left room in the battery and it pushed 10.1 KWH's. It should push even more, but I have no place for the energy to go until I start running the A/C.

 

[GXMnow]

We are now 2 weeks into the next billing month. Things are looking good, even with a few storms moving through. Here is what So Cal Edison is reporting so far.



I made it through the stormy weekend on the 24th without using any grid power, but on the 30th, I did end up net importing 0.92 KWHs. Oops. If I let the battery discharge a little deeper, that would have zeroed out as well. But on the whole, it certainly won't matter at all. I have net exported 97 KWHs in just 2 weeks, averaging almost 7 KWHs a day going out. The days are getting longer, and the weather should also be getting clearer.

My panels were starting to get a bit dirty, but this big storm on Saturday cleaned them off really nice. The Victron system has now been running for 3 months in it's current configuration. As of 1 pm today, it has pushed 567 KWHs to my battery. The XW-Pro charged another 566.3 KWHs into the battery so far this year. I did not expect them to be that close of a match. The Enphase system is 2.4 times the production, but it is also running the house and only the extra goes into the battery. Then the XW-Pro discharged the battery for a total of 1 Megawatt hour. Since it topped 1,000 kilowatt hours, it dropped the precision. Oh well.

The Enphase system has produce 1.4 MWHs so far this year. It also dropped to just one decimal of precision, but I can add up the first 3 months. Jan. 428.1 KWHs Feb. 402.2 KWHs Mar. 611.3 KWHs. Total so far 1,441.6 KWHs. Divide that by 4.8 KW of panels and it works out to 300 sun hours on the array. The Victron system has only 2,000 watts of panel so 561 KWH / 2 = 280 sun hours. It's a little less, but much closer than I was getting with the BougeRV charge controller. And to be honest, it is actually much better than that. Because it has been dropping to Absorb and Float quite a bit so it is curtailing power it could have made. Here is the last 30 days from the Victron.


20 of the last 30 days went into absorb. I am trying to write some code for the PLC so that when the battery goes over 57.5 volts, it will export some more power o the grid. Why throw it away when I could get credit for it. The had part is that I need to get the export from the Enphase system and add to that to command the XW export values. But I still can't exceed 16 amps of export at any given time. Earlier today, I saw the Enphase system hit 3,900 watts. That is all 16 inverters clipping and 16 amps coming from the array.