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Inverter hates washing day


Fuenkli
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the cycling loads of the washing machine, tumble drier and iron totally confuses my inverter. It is trying in vain to adjust fast enough to have an optimized PV yield. It is especially slow when it has to change from battery charging to discharging mode. Is this normal? Are the Goodwe inverters worse than the competition? Does the zero export setting contribute to this slow adjustment speed? Why is it difficult to build an inverter able to adjust much faster to changing load conditions? 

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I'm curious. How bad is this?

A Victron ESS setup, especially when using an external meter, is pretty slow when it comes to this. It feeds in 60% of the error on each reading (every second) and adjusts the level every 2.5 seconds, so it takes a good 5 seconds to adjust to the new load level. With my own washing machine, this means it has usually just reached the new level when the machine stops and changes direction. Despite the slowness it has never really bothered me that much.

I have not looked into how fast the Fronius is, but I think it is a little faster than the Victron.

So what do you see with the Goodwe?

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1 hour ago, plonkster said:

So what do you see with the Goodwe?

I observed the following. It is not 100% accurate because I can only monitor it with the EzManage App which updates the values only every 2 sec or so. Would be nice to have a fast real time graphical view of all the important parameters to analyze the inverters behavior.

 

abrupt unloading of heavy load on Inverter:

- back feed to grid for 3 sec

- MPPT overreacts and almost shuts down PV production by increasing V 

- MPPT reaching maximum production level again after 15 sec (if the next load cycle arrives at < 15 sec MPPT never recovers and production goes lower and lower in every subsequent cycle)

- Battery charging reduces or stops in line with PV production reduction

- Battery charging back to max after 15 sec  and > 30 sec if the inverter was in battery discharge mode

 

abrupt loading of heavy load on inverter:

-  grid supply for 15 sec if there is sufficient PV capacity and > 30 sec if it has to change into battery discharge mode 

 

 

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I shall compare with my Victron system...

43 minutes ago, Fuenkli said:

- back feed to grid for 3 sec

Same thing happens more or less.

43 minutes ago, Fuenkli said:

- MPPT overreacts and almost shuts down PV production by increasing V 

Depends on how full the batteries are. If there is space in the batteries, then the energy simply shifts over to charging the batteries. If the batteries are full, then the MPPTs back off as well.

46 minutes ago, Fuenkli said:

- MPPT reaching maximum production level again after 15 sec (if the next load cycle arrives at < 15 sec MPPT never recovers and production goes lower and lower in every subsequent cycle)

If the charger has to ramp up from zero, then yes, it might take some time, but generally the MPPTs move faster than this. Again, only a problem if the batteries are really full. If there is space in the batteries, the MPPT just soldiers on...

48 minutes ago, Fuenkli said:

-  grid supply for 15 sec if there is sufficient PV capacity and > 30 sec if it has to change into battery discharge mode 

Grid supply for around 5 seconds and then either PV or battery. Because ESS runs permanently connected to the grid this is completely seamless and the shift is gradual.

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Let me add though, if I am not mistaken, I think the Goodwe brings the solar in on the high voltage side, and then charges from there to the batteries. The Victron system brings the solar in on the DC side, so naturally things are going to be a lot smoother on that end. A comparison is not really apples for apples :-)

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thanks Plonkster for the feedback. It is not really a problem for me either. I think looking over a full days production the losses are probably negligible. I am just curious how inverters work. I would love to spend a day with the soft and hardware engineers in the development department of an inverter company and discuss all the details with them. I used to work in an internal combustion engine development department and understand the problems  and compromises engineers face. 

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Interesting. Axperts with the low voltage SCCs (145 V max PV input) seem fine with washing machine type loads, though I haven't looked closely. And of course they don't attempt to push/pull power to/from the grid.

I wonder how the high voltage SCC versions (e.g. Infini, Axpert MKS II, Axpert VM series) compare. In particular, the Infinis, which are grid interactive (in many modes), and most have the higher voltage SCCs (400-500 V max PV input).

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8 minutes ago, Fuenkli said:

Is there any disadvantage with the Victron/ESS principle? Why do you think Goodwe has chosen a different route?

The top one avoids double-conversion so it is more efficient. If you chop off the buck/boost bit and the battery, you have a normal grid-tied inverter :-)

The bottom one bucks the PV voltage down to battery voltage (not too bad, since the controllers are generally 150V or 250V input), at around 97% efficiency as advertised, and then boosts it again at around 93% efficiency. So total PV->grid efficiency is 90%, while the Goodwe (if my guess is right) would likely do >95% here.

Conversely, the Goodwe inverter would be only around 90% efficient in charging the battery from PV, while the Victron setup is 97% efficient.

The slowness in the Goodwe, if I understand your post correctly, is because of the way the buck/boost bridge to the battery is controlled. Sudden changes in load affects the top part of the picture (PV/Grid) while the bottom part is slow to catch up.

36 minutes ago, Coulomb said:

I wonder how the high voltage SCC versions (e.g. Infini, Axpert MKS II, Axpert VM series) compare. In particular, the Infinis, which are grid interactive (in many modes), and most have the higher voltage SCCs (400-500 V max PV input).

I suspect they do precisely the same thing.

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18 hours ago, SilverNodashi said:

Are you running all 3 appliances at the same time?

yes sometimes they do. Lost the fight with SWAMBO and the domestic worker 😁. I did however observe the mentioned inverter behavior even if only 1 cyclic load like the iron is constantly switching on and off. 

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14 minutes ago, Fuenkli said:

mentioned inverter behavior even if only 1 cyclic load like the iron is constantly switching on and off.

Some part of the pipeline is almost always dampened to make it stable, so this is really unavoidable. In my experience the largest limiting factor are the MPPTs, they really don't like being messed about. I see some new tech coming in now, SMA has some memory feature that I read about where the controller will remember where the maximum points are so it can get back to that point faster. But the entire thing is a bit like masses connected together with springs and if one of them jiggles about all the rest jiggles around with it, sometimes hitting a resonant point, and hence the damping.

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30 minutes ago, Fuenkli said:

yes sometimes they do. Lost the fight with SWAMBO and the domestic worker 😁. I did however observe the mentioned inverter behavior even if only 1 cyclic load like the iron is constantly switching on and off. 

That is normal. Any heating element does that to maintain it's set temperature. This is why I don't run heating elements together, wherever possible. 

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13 minutes ago, plonkster said:

SMA has some memory feature that I read about where the controller will remember where the maximum points are so it can get back to that point faster

 makes a lot of sense. This is what a human tasked to manually optimize the max point would intuitively do. Just shows you how far AI still has to go to match or even surpass humans. 

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  • 2 weeks later...

a small contribution? B)

we have a solar geyser, so why not use it also for the washing machine? [at present with a 3kw element permanently connected to grid, which will soon be changed to 1kw element connected to pv]

reason being that as soon as the 2kw plus element in washing machine kicks in the inverter decides to move the load to grid - even in good sunshine with 2.4kw pv and 100%soc pylontechs [stupid move of the inverter i might add].

solution:

as the washing machine is more or less next to a basin i fill it [see correct level in image] with warm water coming from the geyser [about 50C] through the soap tray with a short hose pipe, i then set the machine at 40C [lowest it can go] and wash - no electricity for element needed.

i did some reading [google and youtube] on this. turns out front loaders use less water and clean more efficient than top loaders or twin tubs EXCEPT if you re-use the water from the latter, this will save water.

just saved myself buying an 'economic' AAAA rated machine [twin tub/top loader] at a cost equivalent of thousands of kilowatts and liters of water :D

i must add it is just my wife and i in the house and i 'work' from the house - doing such chores as would befit a domestic servant and housewife at times ;)

God bless!

g

water level front loader.jpg

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53 minutes ago, gabriel said:

why not use it also for the washing machine?

There is a post on the internet somewhere, from a South African, who installed a tempering valve so that his dishwasher could fill with preheated water from the solar geyser.

With washing I want to use hot water only for the wash (and only luke-warm, just enough to make the enzymes in the powder work). So your best bet here might be a machine with a hot-fill option.

Or... just get a proper hybrid inverter. I remember all these ideas I had until I started running ESS. Now it is just not a problem anymore :-)

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30 minutes ago, plonkster said:

Now it is just not a problem anymore :-)

i try and get at that situation with my present setup - i have already over-capitalized on energy efficiency, which in common parlor is wasted money. :unsure:

37 minutes ago, plonkster said:

just enough to make the enzymes in the powder work

from what i can establish 40c is more than enough for washing just about everything as most enzymes seem to be quite 'active' in that temperature :) - we have grown accustomed not to treat stains before washing and not to pre-soak stuff anymore... at a cost

1 hour ago, plonkster said:

So your best bet here might be a machine with a hot-fill option.

as i said, at this stage our LG is still doing fine. unfortunately i bought one with only a cold inlet, if i had a dual inlet it would save me the manual transfer of warm water... B)

with the knowledge gained on this forum i believe to be in a much better situation with my next solar/energy project - this includes everything from pvs to a kettle  :D.

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On 2018/10/17 at 1:46 PM, Coulomb said:

I wonder how the high voltage SCC versions (e.g. Infini, Axpert MKS II, Axpert VM series) compare.

i seem to have one of those and in the microwave scenario with a sudden load of about total 2200watt [total home] it reverts to grid in about 30sec. this with pvs producing 950watt and pylons at 99%soc. earlier today when the sun was higher the axpert could handle about 2000watt total [toaster] without reverting to grid.

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6 hours ago, gabriel said:

i seem to have one of those 

I don't think you have a higher voltage SCC model; those have a maximum PV input of 400-500 V. Yours would be 145 V, I think. If you are running firmware version 73.00b or 73.00c (one of your posts said this), then you should have a 145 V SCC model, and I would hope (but don't know for certain) that it would stop you from updating with inappropriate firmware. 

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On 2018/11/02 at 12:20 PM, plonkster said:

There is a post on the internet somewhere, from a South African, who installed a tempering valve so that his dishwasher could fill with preheated water from the solar geyser.

With washing I want to use hot water only for the wash (and only luke-warm, just enough to make the enzymes in the powder work). So your best bet here might be a machine with a hot-fill option.

Or... just get a proper hybrid inverter. I remember all these ideas I had until I started running ESS. Now it is just not a problem anymore :-)

Alan Falck

I think he lives up against the Helderberg

 

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