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

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110 posts

Master Geek
Inactive user

#3198093 20-Feb-2024 21:55

You are close now, change the signal point to show Pa Pb and Pc and that will show the loads on all 3 of your phases. The graph just currently shows phases b,c and then the total of all 3 phases

naturalhighNZ

32 posts

Geek

#3198096 20-Feb-2024 22:08

CrazyM: You are close now, change the signal point to show Pa Pb and Pc and that will show the loads on all 3 of your phases. The graph just currently shows phases b,c and then the total of all 3 phases

Ffffffffff why must this be so hard! What would I do without you guys 🤣 thanks I'll give it another go and report tomorrow. Hoping someone may be able to help identify if it is poorly optimised on the phases....

SteveXNZ

59 posts

Master Geek

Lifetime subscriber

#3198108 20-Feb-2024 23:11

naturalhighNZ:

What I would be interested in is a bit more detail on the actual issue you have with EK's billing here, and how this is the cause for the issue you are having? I'd be interested to know if Powershop use the same system, and would be happy to join you in a dispute if there is an issue here.

My first issue with EK is lack of 3-phase disclosure, whether from direct questions or on their website. Next issue is lack of supporting data - they refuse (or cannot) supply 3-phase data from my smart meter, even though the meter captures 3-phase power flows and a wealth of other information that would be really useful to know, and at a greater accuracy than my DTSU666 provides.

Then there's the billing algorithm. For a given TOU period/tariff, the cost is currently "imported energy x import tariff - exported energy x export tariff"

My argument is that it should be "(imported energy - exported energy) x import tariff if positive, or x export tariff if negative".

Ie let's say that in a given TOU peak period I import 10kWh and export 8kWh. Current algorithm says I pay 10 x 40c - 8 x 14c = $2.88. I argue that I should pay (10-8) x 40c = $0.80.

I don't know what Powershop's algorithm is - you'll have to ask them, and hopefully they'll disclose it.

Delving into the mechanics of 3-phase power takes a bit of effort. Traditionally, 3-phase installations are used to run factories and workshops where 3-phase electric motors drive heavy plant, taking advantage of the torque characteristics 3-phase provides (having the voltage of each phase offset from the others by 120 degrees). Domestic consumers normally get along just fine with single phase, typically 63 amps/240V = 15kW. But increasingly, all-electric homes with an EV charging in the garage can easily blow through this, so while not cheap quite a few are switching to or installing 3-phase without a heavy electric motor in sight.

So now we have 3 x 15kW pipes coming into our homes. Cool - 45kW to play with. But not so fast. We have 3 semi-independent pipes, and loads need to be evenly distributed over these phases. Your sparky will be careful to do this, and your lines company will insist he does.

Then we introduce the complication of a 3-phase solar inverter which takes DC power from solar and batteries and inverts it to AC to feed the house loads while playing a merry balancing act dance with the grid. Your solar inverter will have a power rating (in my case 10kW), so that means it can only invert 10/3=3.3kW per phase - important for when you're considering the draw on your backup circuits when there's a grid outage. For me, this means understanding every circuit in my switchboard, what phase it's on, whether it's on grid or backup, and what appliances it services. Get it wrong and there's a hard or soft breaker trip.

That's why having detailed per-phase data is so important. I'm finally at that point now, but you may not be so lucky if you can't query your inverter's Modbus registers. In that case you use the mobile/web app that comes with your system to query it, and hope you get the info you need. Failing that, can your retailer provide the stats from your smart meter? In my case with EK that's a resounding NO. Final option is to get your sparky to install a separate meter with CT clamps that measures and reports the grid power flows.

And that merry dance I was talking about? Your solar installer should be able to tell you exactly how the inverter performs its load balancing. Expect it to balance net energy well, but not necessarily by equalising the power flows on the phases. That's tricky electrically. And why should it? Net energy is what's important here - if only the retailers would play ball.

SomeoneSomewhere

1802 posts

Uber Geek

Lifetime subscriber

#3198163 21-Feb-2024 10:20

I don't think it's up to the retailer unless they want to lose a significant amount of money.

The lines company charges the retailer line charges (typically up to about 10c/kWh, more for low users) for imported energy.

The lines company charges or credits the retailer for energy exported - Wellington electricity is 0c but others may charge a fee.

Even if no total energy is imported/exported so the actual grid spot price is irrelevant, the lines company will still be charging that 10c/kWh but crediting 0c/kWh on the export.

NZ is moderately unusual in that we essentially have a flat rate regardless of connection size, up to 69kVA (3~ 100A). Many countries would charge you a higher daily charge for connections above around 23kVA (1~ 100A), or subject you to a maximum demand pricing.

Ge0rge

2052 posts

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#3198175 21-Feb-2024 11:09

Unfortunately, I can't see NZ going to net metering, the current system in regards to micro-generation is too much of a cash-cow for everyone involved in the generation and delivery of electricity.

I returned 154.08kWh to the grid last month, and got to pay Octopus $53.62 for the privilege.

SteveXNZ

59 posts

Master Geek

Lifetime subscriber

#3198390 21-Feb-2024 15:25

As a general rule, electricity retailers provide a bundled service for consumers by buying electricity on the spot and contract wholesale market from the big generating companies (Genesis, Mercury, Meridian & Contact), and transmission or distribution services from lines companies/Transpower in the form of fixed and variable charges.

These are reflected on consumer invoices where the energy charge in kWh is primarily related to energy use in TOU/ripple control categories, and a fixed daily charge which is primarily related to grid connectivity and services. I use the word “primarily” as it’s up to each retailer as to how they translate energy purchase to energy sale, and transmission/distribution services to fixed daily charges with associated margins. No doubt there’s a bit of cross-fertilisation as retailers seek maximum competitiveness.

I fail to see why there should be differentiation between single phase and 3-phase energy sale to the consumer, when there’s no corresponding cost to the retailer when buying on the wholesale market from the generators. Perhaps I’ll find out as I progress my case through UDL.

SomeoneSomewhere

1802 posts

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#3198457 21-Feb-2024 17:44

OP, which lines company/region are you in? I'll dig out their line charges and pricing methodology, which is required to be published openly.

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naturalhighNZ

32 posts

Geek

#3198459 21-Feb-2024 17:56

CrazyM: You are close now, change the signal point to show Pa Pb and Pc and that will show the loads on all 3 of your phases. The graph just currently shows phases b,c and then the total of all 3 phases

Okay I think I got it - love to know if any insights or anything I can take from this. What I note, and probably my issue with the installer, is that I very clearly am importing at times when I'd rather not be related to the phasing.

Re the other question - I'm in Northland (Whangarei) - be interesting to know how the pricing works but I think Powershop are reasonably good at sharing this - but I may not be seeing the full picture. I'd be happy to lobby on the issue of net metering though, I certainly agree the current model is just dumb.

SomeoneSomewhere

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#3198488 21-Feb-2024 19:14

I expect you'll find that if you look at any individual vertical slice in the 1700-1900 (ish) section that your inverter is battery exporting in, you'll find that a+b+c=0. That's what the inverter is trying to achieve, and all it probably can achieve.

Interestingly, it looks like there are now inverters that allow for three phase unbalanced output. I didn't find that last time I looked. It might be worth talking to them and seeing if a) Huawei can offer a software or hardware upgrade to support this, or b) whether an inverter swap could be possible (but the battery might not be compatible with the new inverter). I wouldn't hold out too much hope.

You're on Northpower's network then, and their charges apply to your retailer

You can check the EA Your Meter site to find out which price category you're in, but I'm going to assume it's "DM7-TOU Residential Standard - Principal Place of Residence (Time of Use)".

That means that, for your connection, the retailer pays:

$1.3425/day to Northpower
$0.4575/day to Transpower (passed through Northpower, I think)
10.15c/kWh to Northpower during peak periods
6.31c/kWh to Northpower during shoulder periods
Nothing for energy used in off-peak periods
Nothing for energy used by ripple switched loads on either a night only (NO8, night store) or 18h/day minimum (CN18, e.g. hot water) profile
1c/kWh for energy exported to Northpower from your PV or battery, regardless of time of day.

This is what Northpower charges for moving the energy around. It does not include the cost to buy/sell the energy from the spot market.

So at peak time, when you are exporting 1kWh on one phase, and importing 1kWh on another phase, Northpower will be charging a fee of 10.15c for the import and 1c for the export, adding up to a total of 11.15c. There would be no charge or credit for the actual energy from the spot market, because they cancel out.

naturalhighNZ

32 posts

Geek

#3198489 21-Feb-2024 19:27

When you say there is no spot price charge because they cancel out, I thought that is the precise issue with three phase, in that they don't - and I'll still be paying 30ish cents per kW to import, and receiving 13 cents to export. So in that scenario - 1kW out and 1 kW in - I end up paying 17 cents to the provider.

I might be missing what you are actually trying to tell me there...

SomeoneSomewhere

1802 posts

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#3198495 21-Feb-2024 19:49

The cost for your retailer to get you energy is made of two parts:

1: Cost for them to buy the energy on the spot market (varies from nothing to ~50c/kWh).

2: Cost for them to pay Northpower to get the power to you. (16.25c/kWh if you're on a low user TOU plan)

The money you get back from selling power is also split up:

3: Revenue from selling the energy on the spot market (varies from nothing to ~50c/kWh). This is the exact same price as 1.

4: Cost for them to pay Northpower to accept the power back onto the network (1c/kWh).

1 & 3 cancel out when you buy energy, and sell it straight back.

2 & 4 are the cost to have the energy couriered to you and then mail it straight back. These add up to 17.25c/kWh if you are on a low user plan during peak periods.

naturalhighNZ

32 posts

Geek

#3198496 21-Feb-2024 19:51

Oh sorry yes from the providers perspective. Got it. Yeah that makes sense. For me the result is obviously quite different. My bills have continued to range from $175 at the lowest to almost $300 at the highest since around November.

SomeoneSomewhere

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#3198497 21-Feb-2024 20:00

Yeah. So switching power companies and yelling at the power company is unlikely to do much: they're just passing on what the lines company charges, and given the lines companies all seem to have fairly similar pricing structures, I'm pretty sure that this is something handled by the Regulator.

On the other hand, Flick I believe buys back power at spot market prices. That could potentially be moderately profitable for exporting during evening peaks (spot prices 20+c/kWh), at the cost of receiving less while exporting at midday if the spot prices start to sag at noon. We aren't really seeing that yet.

naturalhighNZ

32 posts

Geek

#3198550 21-Feb-2024 20:31

Yeah my plan wasn't to yell at the power company :-) Though I do think some pressure on the Electricity Commission wouldn't hurt re: needing some better policy here.

That said, Flick is an interesting prospect. The spot pricing always makes me a bit nervous - most of my export would be during the day so not sure how that would pan out. Is there anywhere you can see what the prices were say over the past month?

Edit: Never mind... I checked; they don't supply my address :(

SomeoneSomewhere

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#3198554 21-Feb-2024 20:52

Transpower runs electricityinfo.co.nz.

You're most interested in Bream Bay BRB0331, but the prices at Otahuhu (OTA2201) are almost identical.

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