MPP SOLAR PIP-7248MAX

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coulomb
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Re: MPPSolar PIP-7248MAX / Voltronic Power Axpert MAX 7.2k

Post by coulomb »

birdibird wrote: Thu, 04 Feb 2021, 19:57 This device has already been discussed in this thread, so why open a new one?
@coulomb can you merge the 2 threads?
Done.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
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paraterra
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Re: MPP SOLAR PIP-7248MAX

Post by paraterra »

Hi

I'm looking into PIP 504MGX and PIP 7248MAX (or 8048MAX). I don't want to feed back into the grid and so far I was under the impression that th eMPP PIP models don't feed back in.

Now I came across following post in another forum (https://powerforum.co.za/topic/7733-adv ... ment=88670) claiming that occasionally the 7248MAX model feeds back into the grid.

I'm now confused.

Does anybody know more on this topic ?
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Re: MPP SOLAR PIP-7248MAX

Post by coulomb »

paraterra wrote: Thu, 18 Mar 2021, 01:19 Hi

Welcome to the forum.
Now I came across following post in another forum (https://powerforum.co.za/topic/7733-adv ... ment=88670) claiming that occasionally the 7248MAX model feeds back into the grid.
Yes, but only in SUB mode, only small amounts, and only for very short periods of time, less than a second. As soon as the grid voltage disappears, the relay connecting AC-out to AC-in will drop off, so no power will be fed to the grid. Even in the rare case when other inverters are islanded and keep power on that island, most of those will be grid feed inverters that will drop off within about 30 seconds, as required.

Only if a set of inverters without island detection such as PIPs in SUB mode remain connected in an island, will there be a problem. They would have to be islanded with small enough loads that they can power all those loads. I've only just realised this problem, and only by thinking about your concern. And it all depends on whether I understand this mode correctly. It may be for example that PIPs have some form of islanding detection, though I doubt it. So my guess is that the danger is slight, but present. It doesn't even require that power is exported, just that the AC-in port could be connected to the inverter output when it is generating AC power from an energy source (PV).

I explained the details of SUB mode better (as far as I believe I know them) here.

[ Edit: fixed url. ]
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
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Re: MPP SOLAR PIP-7248MAX

Post by coulomb »

Partly to sort it out in my own mind, I thought I'd describe in more detail how I think that this problem might arise. Let's consider a working class suburb on a working day. There is a fault affecting just one transformer, or there is scheduled maintenance, so the grid is disconnected for that small group of houses. Say it's 100 houses. It's a moderately affluent suburb, where 25% of the residents have solar (obviously the details could vary and the situation could still hold). Most of the residents are at work, so the loads are small, well under 25% of their inverters' rated capacity. It's a sunny day, with plenty of solar power available. If they have batteries, most of them are full, so there is negligible battery charging happening. These houses' solar energy systems are saving their residents from having to use much grid power; only 50 kW was being supplied by this transformer (500 W average over the 100 houses) when the grid disconnected. The 25 houses have 5 kW inverters each, so they can supply 125 kW between them. So the loss of 50 kW of grid power can be comfortably supplied by them, even while supplying their own loads. Now suppose that most of these 25 inverters (enough to cover the 50 kW deficit with ease) are the type that don't have proper islanding protection, and are in an SUB-like mode where their inverters are connected to the grid cables.

Islanding protection requires techniques like frequency shifting, sudden voltage changes, or the like, that supposedly can tell the difference between the grid (which is assumed to be stiff and resists such sudden changes) and PV inverters, which are assumed not to resist such changes as much. I'm not convinced that it's easy for any inverter, even those with impressive certifications, to tell the difference between a bunch of inverters in parallel and the actual grid, but let's leave that aside for now. It's possible with the proliferation of clones and work-alike copies that there will be more than just PIP inverters in SUB mode in this category, I don't know how widespread this is.

In this admittedly rare scenario, it seems to me that the inverters could all stay connected to the grid cables, supplying power from their inverters fed by 125 kW of PV to that cable, and all believing that the 230 V that they see at their AC-in terminals is being energised from the grid (the power supply supply grid, not just the grid cables). This could surprise a line worker, or at the very least make it impossible to work on the fault because the worker would have to contact all the people in the street (most of who are at work in this scenario) and disconnect them from the grid. Perhaps just disconnecting the first 10 houses would be enough, but even that is a ridiculous amount of extra work that should not be necessary. Even if the worker gives up and reconnects the grid (if the grid was only disconnected for scheduled maintenance), the island and the rest of the grid would have drifted in phase from each other, so that connecting the two could cause significant fault current until the inverters dropped out through overload. Some of them may become damaged by this fault current, and the grid switch could be damaged.

I've ignored the effect of three phases in this scenario, to keep it simple.

The problem will be rare, because it requires a sequence of rare events. But accidents usually happen due to a series of rare events; watch any of the air accident investigation TV shows if you need convincing of this. So I don't think you can say that because of its rarity, we can just ignore this problem.

As consumers of PIP inverters, we do have some control over this. We could just not choose to use the SUB (power loads from Solar before Utility before Battery) mode. However, that means missing out on a really useful mode, where small shortfalls from PV to power the load can be supplied by the grid, leaving the battery to charge or remain fully charged. If you're trying to keep your battery full, the alternatives are modes where the loads are powered completely by the grid, and PV is used only to charge the battery (unless it's ready full, in which case PV can't be used at all). If you happen to live in an area with frequent load shedding, this could be an awkward choice to make.

In my mind, I imagined until today that this problem was confined to the models with high voltage solar charge controllers. But I now I realise that the PIP-5048MK (Axpert King) also has this problem, despite its one way AC-DC converter. It has an SUB mode as well, which I believe will have the same problem. [ Edit: Duh! The King in SUB mode will have the AC-in relay off, which means that no power at all will feed in the AC-in terminals, and this problem disappears. The King blends AC-in and PV at the DC bus, not at any AC level. ]

I'm acutely aware that my understanding of all of this is tenuous, so anyone that knows more and can disprove any of my theory, please do so.

Edit: it's just occurred to me that the inverters could be monitoring AC-in power, including the direction of power flow. They certainly monitor the power flow of their DC-AC inverters. Or perhaps a small circuit detects power flow into the AC-in port, and I would not aware of such a circuit or measurement capability. If this is the case, it would be trivial to disconnect a relay and prevent this problem almost entirely. I say almost entirely because even with this situation, the problem persists in the far rarer but possible situation where the grid was supplying negligible power before cutoff and there are no houses without an inverter powering its loads. Then all the inverters are supplying no power to the grid cables, potentially until an unfortunate power line worker touches an active wire. While this is currently unthinkingly rare, with the proliferation of PV systems increasing all the time, it may come close to the rare but must be considered category in future.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
paraterra
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Re: MPP SOLAR PIP-7248MAX

Post by paraterra »

Thx @coulomb for your detailed and quick response.

I'm trying to digest all the information and grasp my head around which model / mode will not have this slight risk of grid feed.

Is it correct to say ? that
- all low voltage SCC models (5048MS, 5048MK) won't have this risk; but only allow grid + solar mix towards battery (not load) ?

- or only low voltage SCC model 5048MK won't have that risk; due to double conversion ?

- all high voltage SCC models 5048MG(X), 5048GK, 7248MAX, 8048MAX) have (or might have) this issue of feeding into grid in SUB mode ?

beyond this, looking at bugs and according firmware patches 5048MK seems the a well supported model
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Re: MPP SOLAR PIP-7248MAX

Post by coulomb »

paraterra wrote: Fri, 19 Mar 2021, 21:25 - all low voltage SCC models (5048MS, 5048MK) won't have this risk;
Yes. I was wrong about the MK/King; it doesn't have the risk. I've added an edit to my post.
but only allow grid + solar mix towards battery (not load) ?
Yes, except that the MK/King can blend (safely at the DC level) AC-in and PV towards the load.
- or only low voltage SCC model 5048MK won't have that risk; due to double conversion ?
No. All low voltage SCC models are safe from the risk of energising the grid during a blackout.
- all high voltage SCC models 5048MG(X), 5048GK, 7248MAX, 8048MAX) have (or might have) this issue of feeding into grid in SUB mode ?
Yes.
beyond this, looking at bugs and according firmware patches 5048MK seems the a well supported model
There have been a lot of firmware revisions for the MK/King of late, yes. I wonder if it's because they are intended for critical applications such as auto tellers and servers, and so there are more demanding and/or influential customers for this model. Hopefully there will be some patched firmware for MK/Kings in the next several months; Weber and I have one for testing now. Patching the MK/Kings will be a slower process for several reasons.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
vincent.p
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Re: MPP SOLAR PIP-7248MAX/islanding protection

Post by vincent.p »

Dear Coulomb, dear all,
Islanding problem is real and taken into account by numbers of grid network regulators.
Here in France, whatevver your solar installation, hybrid, or grid connected but off grid type (normally intended to fully consume production), security breakers are especially required by the law.
It is often used ENPHASE circuit breaker that detects frequencies drift, too high/too low voltage. ABB solution or others are also available at higher cost (for higher power).
Finally the security system against islanding can be more expensive than the inverter itself !!!
In France you normally have also to install insulation transformer when your inverter is not galvanically insulated. Only a way to kill off grid installation, and DIY installation.
The circuit breaker is not exactly always installed for off grid inverter when installation is done by the house owner, the transformer never.
Cost of such transfo decreases interest for homebrew installation.
Since imported hybrid inverters must (or should!) complies with local regulation (at higher cost), all installation conformities rely only on the conformity declaration of the manufacturers. Off grid inverters never complies by nature, probably for economy reason.
In other words, self made declared installation (known by grid company) have very low chance to pass successfully the inspection and grid test without additionnal security breaker.
The french grid company only accepts 3 security breakers without tests (one already obsolete). Other solutions need to be checked and sometime refused.
Without any advertising, Enphase breaker is the cheapest, but non flexible solution. Others can be programmed and updated according different standards.
Vincent.
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Power : 6 kWp + PIP 8048 MAX + 3 US5000 Pylontech
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derBastler
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Re: MPP SOLAR PIP-7248MAX

Post by derBastler »

New Software arrived ;)

I got it directly from one of the support teams

Reflash(45.07)
Remote Panel_Reflash_MCU(12.11)

https://mega.nz/file/tV1nUQDR#yKMU7Nq0b ... D0_zsAlEIc
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Re: MPP SOLAR PIP-7248MAX

Post by coulomb »

derBastler wrote: Tue, 05 Oct 2021, 04:29 New Software arrived ;)
Thanks for sharing.
Reflash(45.07)
Remote Panel_Reflash_MCU(12.11)
45.07 is the same as has been seen before. I compared the dsp.hex files to be sure (it's not as though version numbers are always unique).

Removable display firmware version 12.11 is newer than I've seen. So it looks like all the changes are happening in the removable display firmware, presumably updating the BMS handling code. So it's good to know that the DSP side of things is stable. This firmware returns 44, 45, or 43 from the QGMN command (Query General Model Name); I don't have these codes documented.

Weirdly, QMN (Query Model Name) returns either VMIII-nnnn, KING-nnnn, or MKS2-nnnn. nnnn is the output rating apparent power, which comes from the DSP's response to the QPIRI command (device rating information enquiry). My guess is that QMN is now an obsolete command, obsoleted by QGMN.

Edit: PIP-7248-MAX models (Axpert MAXs) may report as MKS2-7200 from the QGMN command. So maybe QMN isn't obsolete after all.
MG ZS EV 2021 April 2021. Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
Patching PIP-4048/5048 inverter-chargers.
If you appreciate my work, you can buy me a coffee.
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