Need some help with a Huawei three phase solar inverter and battery

Forums › Home Workshop DIY › Need some help with a Huawei three phase solar inverter and battery - reporting all up the wazzoo

naturalhighNZ

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#311834 18-Feb-2024 19:55

Hey folks, I've been on here before trying to understand issues I am having with my Huawei inverter, usage and what it is reporting. In a nut shell, I had this system commercially installed now about six months ago and since then have been battling big discrepancies between what the inverter says has been exported and imported, vs what the power company says. This is out by up to 50% at times.

My original problem was I wasn't getting any answers from the company but have now had an explanation, which was provided over the phone and I'm still struggling to understand the implications of it.

Basically they've told me that due to net metering issues the system will, say if an item requires 1.5kw; use .5kw on one phase, and import 1.0kw on the other two phases, and report that the usage was covered by the inverter (more or less). They are pretty much saying this is an anomaly of three phase solar in New Zealand and they are learning as they go as well.

My counter point has been that I had asked if there would be value in seeking to change to single phase they said no, it wouldn't make any difference and rather to embrace future capacity advantages of three phase. So I didn't bother. They also didn't obviously highlight any of these issues to me.

I am now wondering how much it impacts - it's likely my system is drawing more power from grid than it probably needs as a result, but in particular the reporting is utterly useless because I can't rely on anything that I am seeing.

I am really wondering if any of the above rings true. I am a layman myself and the person who explained it clearly wasn't experienced but was reading off information they had in front of them. I'm trying to work out how to proceed - if I expect some money back on the inverter to compensate; or if other inverters DON'T have this issue. Apparently Huawei have advised this is something they are aware of and is on their road map for a future new inverter.

Hoping someone who is in the business may be able to tell me more here or help me understand this mess and how much of it I should accept / vs what should have been explained first.

I may have confused a number of things in this - so hoping for some help to work my way through resolving what from my perspective is a system that doesn't:

A: Perform as well as expected (the draw that occurs at various points in the day despite a full battery and generation - probably due to phases)

B: Reporting that is pointless from the app.

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#3197202 18-Feb-2024 20:50

My understanding is that all current three phase inverters will inject an equal amount of power into each phase, regardless of loads in the installation. This is presently more-or-less mandated by AS4777, the standard the inverters are built to. There is an option in there for the inverter to react to voltage imbalance (not the same as load imbalance) and provide an imbalanced output based on that, but I went looking a while back and couldn't find an inverter that actually does this.

For battery-connected inverters, when told to zero out power consumption, the result is the inverter needs to make a choice:

Balance the power consumption of the least loaded phase, resulting in one phase with no import/export and two phases with reduced import.
Balance the total installation power consumption, meaning that while some phases may be importing power and others exporting, total power consumption is zero.
Balance the highest-loaded phase, resulting in one phase with no import/export and two phases with some excess exported power.

A results in you still paying for power, B results you being charged and credited simultaneously, and C results in you being paid the export rate for some power that you probably didn't want to export out of the battery.

Three separate three-phase inverters would be a very expensive and fairly inefficient 'solution' to this 'problem'.

Shifting to a single-phase supply and single-phase inverter would likely result in a significant decrease in available maximum demand from the grid. There is likely a reason why the property was commissioned with three-phase and a change to single-phase could result in blowing pole fuses.

Revenue metering is the issue here. This document goes into the legal aspects - particularly relevant is page 7 onwards.

The current metering code expressly forbids mixing import and export power, whether at different times or on different phases.

Therefore, each revenue meter essentially has two counters per phase, one for import, one for export. Each counter can only ever count up. If you are exporting on one phase and importing on another, those counters will be increasing and you will be billed for import and credited for export in the given time period, even if the total power in the time period is zero.

eonsim

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#3197270 18-Feb-2024 22:34

Someone Somewhere has summarized it nicely.

In NZ there is no such thing as net metering (where exported power cancels out import power at a 1:1 rate) as you might read about from overseas websites.

Any power you export gains you the specified credit (typically 8-18c per kWh), while any import charges you at your specified tariff (anything from 12c to >30c per kWh). For a single phase system this isn't typically a problem your house will draw on the inverter first, then if that can't provide enough power it will draw on the grid to top up the amount your house needs, inversely when you generate more power than you need the excess will be exported up to your lines company export limit (which is 5kW for a lot of NZ), if you reach the export limit the inverter will reduce the power it generates.

For example you need 2kW on a single phase inverter:

The inverter is producing 1kW, so you use that 1kW, and import and extra 1kW to make up the difference and get charged for it.
The inverter is producing 2kW, you use that power with out importing or exporting anything.
The inverter is producing 6kW, you use 2kW and export 4kW for credit.

This gets more complicated with 3 phase houses, especially if the houses have unbalanced load on the three phases for example all household circuits are on phase 1, the stove + AC on phase 2 and phase 3 is unused or used by the garage.

As described above nearly all 3-phase inverters have to balance their generation across all three phases, and the majority of them are designed to split the power equally so if you generate 3kW then there is 1kW per phase. There are 1 or 2 inverters that can do partially unbalanced export say 30% more on one phase which would give 1.3kW, 0.85kW and 0.85kW when there is unbalanced load. The consequence of this is that unless your household power use is evenly balanced across all three phases (highly unlikely) you will end up having increased load on one or more phases that the inverter can't balance and thus must draw from the grid, even while it is exporting on the other phases.

For example 3-phase inverter with 3kW load, and generating 3kW (1kW per phase), export tariff 8c and import tariff of 25c for 1 hour.

Phase 1 has 3kW load, inverter supplies 1kW to phase 1, so house imports 2kW from Grid (costs 2x25c = 50c), phase 2 and 3 have no load and are exporting 1kW each (earns 2x8c = 16c). In this scenario your net cost is 36c.
Phase 1 has 2kW load, Phase 2 has 1kW load, so inverter supplies 1kW to phase1 and imports 1kW on phase 1 (cost 25c), phase 2 use equals generation (cost 0c), phase 3 exports 1kW (earns 8c), in this scenario your net cost is 17c.
Phase 1, 2 and 3 have 1kW load, inverter supplies 1kW to each phase (no cost load = generation on all phases), in this scenario there is no cost and your solar is working optimally.

As you can see unless your load is balanced across all three phases you end up getting charged more for the power you import than the power you export, in such cases there are a few things you can do. Note that pretty much for all of this it's key to know how your power load is distributed across your 3 phases (hopefully they installed a 3 phase import/export meter linked to your inverter so you can see this).

Work out the power load of your house hold appliances/gear and make sure they are split evenly across circuits which are each linked to a different phase. Effectively you would need to audit all the energy use in your household evenly divide it into three groups then get a sparky into hopefully balance the circuits as much as possible, which likely would require rewiring the house and careful management of load going forward.
Switch to a electricity provider that pays a higher export tariff (12-18c) and has time of day charging which means power during the day costs less (see octopus, Electric kiwi, Ecotricity). This reduces the differences between your export and import prices increasing the financial return.
Switch to a single phase or two single phase inverters. If your load is primarily on one or two phases it you may be better off replacing the 3 phase inverter with one or more single phase inverters. If your load is evenly split on two phases then getting two inverters of the same size would help substantially. If the load is unbalanced say 70% on one phase, 25% on the second and 5% on the third then you could get two different sized inverters (for example a 6kW and 2kW) that match your load.

Hopefully this makes some sense to you, the simplest solution which won't be a total fix but might help is to switch to a Electricity company with time of use and a higher export tariff.

If you do have an unbalanced load across your three-phases and the solar installer knew this I'd be highly unimpressed with them and be asking questions about fit for purpose. If neither you nor the Solar company knew you had unbalanced load then it's a muck up on both parts, but they really should have mentioned this possibility when selling and installing the system.

SomeoneSomewhere

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#3197271 18-Feb-2024 22:43

It's essentially 100% guaranteed that any multi-phase house is going to have a significant load imbalance at any given time. The 'law of large numbers' simply doesn't apply, unlike commercial buildings with hundreds of individual loads and most large (>10kW) loads being balanced three phase.

I suspect the issue is that the OP has a battery system, and thought/was told that this meant they could zero out usage during peak times. The issue is that that's not quite how the metering regime works.

naturalhighNZ

32 posts

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#3197287 19-Feb-2024 07:14

Thanks all for the replies. That's really useful and helps me understand how the system is operating in three phase.

To clarify they suggested optimising - I said, didn't you already do this? I remember them saying it was important before install. They have not installed three phase metering monitoring as far as I am aware - this is my issue, the reporting is rubbish - the Huawei app does not show me anything detailed enough and the data is out by a magnitude of 50% or more some days. This is unacceptable I feel - given monitoring is intrinsic in solar. Is it the solar company or power company that would install the three phase metering monitor?

Noteworthy is this was a new build and all these conversations could have been had before any wiring was done - thus I asked them should I switch to single phase and they gave an emphatic no - embrace the three phases! Oh dear.... (I have that in writing).

The monitoring is my biggest sticking point. It's the issue I am most dissatisfied with. But absolutely I believed having a battery would allow me to ride out peak periods etc. I currently don't understand what the battery is doing when it is exporting, sounds like it is sometimes feeding the grid, and other times phases? The only saving grace atm is that my nighttime rate equals almost to a T the export rate. So it has meant I've shifted high use stuff (i.e. car charging) to night time and not bothering trying to "optimise" solar during the day - acknowledging this is impossible with my setup.

I am really trying to work out what I should expect here - I feel that the monitoring issue should be remediated; or compensated for quite considerably ($18,8k inverter). I note the suggestion they could install two single phase inverters on the phases most used - but I have no idea what those are or how the loads are spread at all. So I might need to push this with the company?

Any suggestions on practical next steps - keeping in mind it is only six months since install and go live of the system wasn't until September.

SomeoneSomewhere

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#3197412 19-Feb-2024 10:11

You absolutely have three phase revenue metering from the power company. You may need to specifically request access to get the half-hourly data or it may just be available on the website. I don't believe the revenue meters break it down by phase.

The metering from the inverter is likely what you're looking at. It's not wrong, just measured differently. It's almost certainly measuring all three phases.

If your house is using 1kW, 2kW, and 6kW on the three phases, the inverter will sum it and say you're using 9kW. It'll then inject 9kW, 3kW per phase. It then measures that as 9kW load, 9kW generation, 0kW total load

The revenue meter sees -2kW, -1kW, and 3kW. It sums this to 3kW export, 3kW import.

Both are correct, but the answers are different.

If you post load graphs from the inverter we might be able to confirm this is what's happening.

Ge0rge

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#3197424 19-Feb-2024 10:33

Something else to consider - the inverter might not actually be doing any metering, other than it's own production.

My (admittedly single phase) inverter does not have any monitoring of the property import/export. It simply makes as much power as it can based on available sunshine, and pumps it out. It doesn't know if that energy is consumed on the property or exported.

I have a Shelly Pro 3EM that does all my metering, and it's within margin of error compared to what the power company bills me each month. Perhaps something like that might be an option to give you a third data set to compare the other two with?

Edit: Just re-read that the OP does have monitoring. I'd still consider the 3EM as an option to help work out what's happening.

SomeoneSomewhere

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#3197452 19-Feb-2024 11:48

Yeah, a purpose built check meter is almost certainly going to give you more complete/useful data than metering as part of something else.

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naturalhighNZ

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#3197457 19-Feb-2024 12:22

Here's a go at sharing some pictures. All from the 17th.

Ge0rge

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#3197468 19-Feb-2024 12:45

The first thing that leaps out at me is why are you charging your battery from the grid at 0400, instead of using the sun to charge it slightly later in the day? You're paying a premium to charge you battery, and then exporting your own generation for chump-change!

naturalhighNZ

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#3197478 19-Feb-2024 13:14

Na it's not quite like that.

From 2200-0700 I pay 13 cents per kW (rounded) incl gst. Export I receive 13 cents a kW.

So by my thinking I am better off using the battery to offset my peak costs from 0700-0930 and locking that in, than trying to combine generation, charging and import.

Fourth power company in six months and it seems to be working the best for me at this stage considering the heavy and almost daily EV charging we do. Thus daily cost goes between $6 and $11ish.

eonsim

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#3197632 19-Feb-2024 18:46

It might be worth looking at the website of the inverter manufacturer and logging into their cloud version, which I think is FusionSolar for your inverter. It's possible there is more detailed information in that system compared to the mobile app you are currently using. Hopefully that will allow you to see what exactly is happening on each phase of your system rather than the summed total.

One question, what is size (kW) of the inverter and installed panels, also the capacity of the battery? Looking at the figures above it seems the inverter is capping it's generation at ~6.5kW (the flat line) which is rather odd. Typically you only get that sort of flat line if you have more panels than inverter (and 6.5kW seems an odd size for an inverter) such that the inverter limits generation. Or secondly if you have an export limit set that means the inverter can't export more than a set amount, but with 3-phase I'd expect that to be something like 5kW per phase or 15kW total (if you had a 15kW inverter + panels)...

Given your day export rate is equal to your night import rate, timeshifting as much use to overnight makes sense. Also as your currently doing using your battery to offset the peak period rates is ideal.

If you can get more information about your individual phase power use there may be some other optimizations that could be implemented in the shoulder periods. Also you are using a lot of power when you get home at 5pm, is an EV charging then, or AC turning on? If so it would pay to delay the charging, or have the AC turn on earlier before you get home during the part of the solar day when you have more generation.

naturalhighNZ

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#3197640 19-Feb-2024 19:33

I am having a really hard time with the FusionSolar site - it's worked for me in the past, but now isn't accepting my passwords nor my request to password reset. Argh! It's infuriating how much is locked behind the installers section of the app - I can't even action a password reset request. Anyway I'll get onto that - I can see a bit more if I look at the unit itself in the app - for example I can see:

AC Output across A, B and C - Grid Voltage and Grid Current - not sure if those have much value or use given what I am working on?

The system is: System size 8.19 kWDC (STC) Estimated annual production 10,967 kWh Solar panel 21 × 390W Trina Solar Vertex S 1754 mm × 1096 mm · Monocrystalline 1 × Huawei SUN2000-6KTL-M1 · 6600W Three phase · 98.6% max. efficiency Battery storage 1 × Huawei LUNA2000-5-S0 5kWh (5kWh usable) · Lithium Ion Estimated system efficiency 97% Sounds like the inverter is awfully small. Jeez. I am really starting to feel like I got ripped off. I would've assumed a direct correlation between system efficiency and generation - i.e. the cap you are referring to, unless it is only losing me 3% with more panels than inverter which is probably okay as I lose efficiency? I don't know. In summary, I still, the more I read, feel like none of this was adequately explained; and that the inverter isn't giving me useful data; and the performance is not what was made out. I mean even these assumptions they make (i.e. utility costs dropping from $300 a month to $92.99 first year average - that estimate MUST have assumed single phase, I just can't imagine anything other than that). 8.19kW solar system with 5kWh battery storage $18,900.00 $18,900.00 Huawei SUN2000 6KW KTL 3-phase Hybrid Battery Ready Inverter /10 Year Warranty Advanced Monitoring Optimiser Technology/25 Years Warranty

5PM I am pretty sure is getting home, switching TV on, and turning on the induction hob and / or oven for dinner. Pretty sure anyway. EV is set to power on at 10PM until 7AM.

Couple of photos I could get when logging in directly to the inverter via wifi connection locally:

naturalhighNZ

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#3197649 19-Feb-2024 20:02

Really immensely confusing when they have the system at 8.19kW and then the inverter at 6kW in my opinion. How is a lay person supposed to get their head around all this?

Ge0rge

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#3197651 19-Feb-2024 20:08

21 panels @ 390W each gives you 8.19kW - that's your max gen from the panels .

6kW is how much your inverter can produce.

Systems are often set up with more panel capacity than the inverter can produce to help out in winter, cloudy days etc. The inverter will "clip" in mid summer, but produce more in winter than if you only had 6kw of panels - you'd barely ever max the inverter.

SomeoneSomewhere

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#3197652 19-Feb-2024 20:08

The inverter is definitely measuring all three phases, but as you can see it's aggregating the values for power whereas the metering code requires the revenue meter to consider them separately.

6.6kW inverter and 8kW of panels is a slight over-panel situation, but IMHO this is not bad. It's just not a very big system and much of the cost is in the battery.

If you can get half-hour CSVs out of the power company, we might be able to tell you how much you're losing by paying to export and reimport.

Having the panels exceed the inverter capacity means that in absolute full sun, the inverter will limit capacity. However, in any situation other than full sun, more panels gives you more power. It depends on cost-per-watt of panel and inverter, but more panel is probably better in most cases. That is, 6.6kW inverter and 8.2kW panels is preferable to say a balanced 7.4kW system.

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