Home solar output throttling

[edddo]

Anyone here also getting stung by this?
The idea is that if the grid voltage exceed your inverter voltage then the inverter shuts down and your production stops.
My sisters system has just about been rendered useless - certainly any break even period has been multiplied by X.
Our system with 6.5kw of panels and a battery is now worth significantly less to us as on good sunny days I estimate we get throttled to the tune of a 20 to 30% reduction in daily output/feed-in.
I have asked my installer to request our distributer (Ausnet) to adjust the local network point as apparently that is possible. But I don't think that resulted in anything. I will be going back to my seller/installer to see if there is any adjustment for throttling in the inverter ( Solax brand) as some of the smarter inverters can adapt to high grid voltages somehow.

In any case I feel like I have been sold an idea that has not materialised - the best production days/times are often throttled and I expect this is a problem that will only get worse. Incentive for more independence from the grid really - more battery and maybe a generator?

[Slunnie]

Anyone here also getting stung by this?
The idea is that if the grid voltage exceed your inverter voltage then the inverter shuts down and your production stops.
My sisters system has just about been rendered useless - certainly any break even period has been multiplied by X.
Our system with 6.5kw of panels and a battery is now worth significantly less to us as on good sunny days I estimate we get throttled to the tune of a 20 to 30% reduction in daily output/feed-in.
I have asked my installer to request our distributer (Ausnet) to adjust the local network point as apparently that is possible. But I don't think that resulted in anything. I will be going back to my seller/installer to see if there is any adjustment for throttling in the inverter ( Solax brand) as some of the smarter inverters can adapt to high grid voltages somehow.

In any case I feel like I have been sold an idea that has not materialised - the best production days/times are often throttled and I expect this is a problem that will only get worse. Incentive for more independence from the grid really - more battery and maybe a generator?

You're on the money there, the grid voltage is higher than what the inverter will put out and so the inverter shuts down until the grid voltage drops again. It probably shuts down during the peak of the day because every other solar system is returning power to the grid.As you know, your network supplier will have to tap down the transformer voltage at the street. My solar was useless until they did this. If I recall correctly, I potentially may have delt directly with Essential Energy who maintain the network here rather than Origin who are my retailer.

[edddo]

You're on the money there, the grid voltage is higher than what the inverter will put out and so the inverter shuts down until the grid voltage drops again. It probably shuts down during the peak of the day because every other solar system is returning power to the grid.As you know, your network supplier will have to tap down the transformer voltage at the street. My solar was useless until they did this. If I recall correctly, I potentially may have delt directly with Essential Energy who maintain the network here rather than Origin who are my retailer.

Yes its my understanding that as the number of solar installations increase that this happens on high output days - that is the grid voltage is bumped up by more and more solar systems and once it is above about 255V - most inverters shut shop. I wonder if new buyers are informed - I was not 2 years ago but it didnt seem to be an issue here until last summer.

[Tombie]

My system puts out the most power on sub-optimal days when the lesser installations are producing less.

Once we great bright, clear, supper sunny conditions it throttles back.

Our entire grid here is on solar. So we regularly see line voltages climb above 255v

[350RRC]

If the grid and the connection to Tas was improved more of your 'excess' power could go there during the day and more could come back at night or when the wind ain't blowing.

The cable looks to be limited to about 490 Mw at the moment.

You can watch these energy transfers updating every 5 mins live here:

ELJM: NEM Regional Generation Summary (http://nemlog.com.au/gen/region/)

DL

[dero]

An excellent business plan , if you have few morals [ ie the govt & their corp mates ]
Suck everybody in , get your power for virtually nothing , sell it for the same old price or better & reap in the profits .
Great for the economy , not so good for the average bloke .
And they even get to claim credit for being eco friendly .

[Homestar]

Very common problem now and something most people don't understand when installing solar. The only real way to do anything about it is to load shift or put batteries in. Start using all the heavy electricity using appliances during the day - dishwasher, washing machine, etc - this will then use what solar is being made effectively costing you nothing to use them. Most more modern inverters have a connection for batteries now so that's another option, but not a cheap one - well worth doing if you're in the market for an EV so you can effectively charge it for nothing overnight off the batteries. Also, if you have a storage style hot water system, you can put an extra heating element in and sink the solar into the HWS to reheat it during the day if you have nothing else to do with it.

But just using the power as it's made is the best way of saving a bundle on your electric bill and it will pay for itself in no time. If no one's home during the day, timers are great for certain things but some appliances may need updating - like some dishwashers for example - to units with inbuilt timers.

[windsock]

Yep, people need to be more aware of the market they are effectively entering into when installing grid connected systems.

A combination of sales zeal and the prospective prosumer being blinded by possible $$. Self consumption is a critical step required to remedy the situation. Maximise your return by reducing your energy expenditure. This is a key driver to uptake in industry - self-consumption at peak cost time of use.

[roverrescue]

I’ve noticed some potential loss on our 9.8kW system
AGL have an upper daily limit on the 17c FIT
Once that limit is reached no more nice FIT

We now have an invertet pool heater which will happily eat as much power as it is fed (19kW unit from memory) but that’s heating effective NOT 19kW usuage

Anyways

A question - does anyone know a way to control a load on a specific circuit via the output of an array?

The heater doesn’t really care about turning on and off

It would be nice to have the heater ONLY running if day the array output is 5kW or greater ???

S

[edddo]

Very common problem now and something most people don't understand when installing solar. The only real way to do anything about it is to load shift or put batteries in. Start using all the heavy electricity using appliances during the day - dishwasher, washing machine, etc - this will then use what solar is being made effectively costing you nothing to use them. Most more modern inverters have a connection for batteries now so that's another option, but not a cheap one - well worth doing if you're in the market for an EV so you can effectively charge it for nothing overnight off the batteries. Also, if you have a storage style hot water system, you can put an extra heating element in and sink the solar into the HWS to reheat it during the day if you have nothing else to do with it.

But just using the power as it's made is the best way of saving a bundle on your electric bill and it will pay for itself in no time. If no one's home during the day, timers are great for certain things but some appliances may need updating - like some dishwashers for example - to units with inbuilt timers.

Are you sure that when throttled, that solar power is available to the household, or to a battery? I thought it just put you on the grid.

[edddo]

There is a product on the market that deals with this problem

EdgeIQ | Edge Electrons (https://www.edgeelectrons.com/edgeiq)

Pricey but may well be worthwhile very soon. I dont understand how these work?

[Homestar]

Are you sure that when throttled, that solar power is available to the household, or to a battery? I thought it just put you on the grid.

Yes, the solar will provide power to anything it can - just because the inverter can’t pump it into the grid because the local voltage is too high it doesn’t mean you can’t use your own power. [emoji106]

[edddo]

My seller/installer does not agree with you - When part throttling it will feed the house and battery but when it is off it forces me onto the grid..but perhaps some setups are different.

[Homestar]

My seller/installer does not agree with you - When part throttling it will feed the house and battery but when it is off it forces me onto the grid..but perhaps some setups are different.

What make and model inverter do you have - that’s different from any other system I’ve heard of - usually you use what you want and any you aren’t using goes back to the grid if it is available to take it (ie the local grid voltage not being too high). Grid power is only used when you are consuming all of the available solar or it’s dark, etc.

Why would a system be designed to not give the grid power OR you power - that doesn’t make any sense.

[BradC]

Most more modern inverters have a connection for batteries now so that's another option, but not a cheap one - well worth doing if you're in the market for an EV so you can effectively charge it for nothing overnight off the batteries.

I've never seen the maths on that stack up. Pay $x for a battery to save $y on electricity. Over the lifetime of the battery anytime I've done the sums x>y. Has it improved?

[Tombie]

I’ve noticed some potential loss on our 9.8kW system
AGL have an upper daily limit on the 17c FIT
Once that limit is reached no more nice FIT

We now have an invertet pool heater which will happily eat as much power as it is fed (19kW unit from memory) but that’s heating effective NOT 19kW usuage

Anyways

A question - does anyone know a way to control a load on a specific circuit via the output of an array?

The heater doesn’t really care about turning on and off

It would be nice to have the heater ONLY running if day the array output is 5kW or greater ???

S

Link to inverter, put a smart controller on pool heater.
Use IFTTT to control based on output.

[Homestar]

I've never seen the maths on that stack up. Pay $x for a battery to save $y on electricity. Over the lifetime of the battery anytime I've done the sums x>y. Has it improved?

I think it’s borderline - certainly didn’t work with AGM but with the price of Lithium and Sodium falling and both having extremely long life cycles, would be interesting to run the numbers - I’ll have a play.

[Graeme]

Link to inverter, put a smart controller on pool heater.
Use IFTTT to control based on output.My Fronius inverter has load management support, able to switch up to 4 relays depending on criteria set on a web page. I use it to switch my HWS.

[edddo]

What make and model inverter do you have - that’s different from any other system I’ve heard of - usually you use what you want and any you aren’t using goes back to the grid if it is available to take it (ie the local grid voltage not being too high). Grid power is only used when you are consuming all of the available solar or it’s dark, etc.

Why would a system be designed to not give the grid power OR you power - that doesn’t make any sense.

@Homestar

This is my system Solax Power Station | Sunshine Coast Solar Power (https://www.thesunworks.com.au/solax-power-station/)

[roverrescue]

Hmmm
Thanks Tombie and Graeme
My inverter is. 3ph 15kW jobby and should also have load management

I’m kicking myself for not running an extra few wires in the conduit from board to pool house now !!!

Might need to magic up a BT or wireless or something rely / switch thingamajigger

S

[Graeme]

My PV system is some distance from my house so I use a home-grown system that utilises a cheap wireless remote control system to power a relay wired in parallel with the HWS's off-peak switch in the house switch box. The off-peak switch is normally disabled as the inverter's load management facility has an option for daily minimum on-time that I can configure if there's been a run of cloudy days.

[Homestar]

There is a product on the market that deals with this problem

EdgeIQ | Edge Electrons (https://www.edgeelectrons.com/edgeiq)

Pricey but may well be worthwhile very soon. I dont understand how these work?

It’s not that simple - while that device will show the system the grid voltage is lower - in reality it isn’t and unless that device is breaking the law it can’t allow a higher voltage back into the grid - which is what your system needs to do to push its power in there - with it without that device. It says up to 15% more - but 15% of 0 is still 0. If the grid voltage is too high to allow any input from the PV system, this won’t help. I’m only on my phone at the moment but will post a better explanation at some point.

[Homestar]

@Homestar

This is my system Solax Power Station | Sunshine Coast Solar Power (https://www.thesunworks.com.au/solax-power-station/)

Thanks - not much technical data there - do you have anything on the ‘throttling’ you are describing? Is that something above and beyond what the inverter would normally do once the local voltage reaches its peak voltage or something else?

[Graeme]

It’s not that simple - while that device will show the system the grid voltage is lower - in reality it isn’t and unless that device is breaking the law it can’t allow a higher voltage back into the grid - which is what your system needs to do to push its power in there - with it without that device. It says up to 15% more - but 15% of 0 is still 0. If the grid voltage is too high to allow any input from the PV system, this won’t help. I’m only on my phone at the moment but will post a better explanation at some point.
It appears that this device can allow the PV system to provide more of the household consumption when the grid voltage is unnecessarily high, saying as much as 15% more is produced by the PV system and therefore less drawn from the grid, but it doesn't appear to claim to increase export.

[Homestar]

It appears that this device can allow the PV system to provide more of the household consumption when the grid voltage is unnecessarily high, saying as much as 15% more is produced by the PV system and therefore less drawn from the grid, but it doesn't appear to claim to increase export.

Could be the case but that’s not how I read it. The standard inverters don’t need help to supply the household they’re connected to.

[Graeme]

They would if the grid voltage is already above the inverter's upper limits or close enough to severely limit the inverter's o/p. However the electricity supplier then has to reduce the voltage back to within their allowable limit.

[Homestar]

Not that simple and there’s quite a bit to consider and understand but I don’t seem to be making anyone understand - probably my fault for not explaining clearly enough, so I’ll not continue with this - I work with the grid and the supply authorities and with how solar interact with the grid so I’ll stick to actually doing that rather than this. I am trying to help the OP not have an argument about this.

[steveG]

My take on that device is that it will stop your inverter seeing the high grid voltage and shutting down.
It won’t help with the solar harvest being fed back into the grid, but will reduce your power consumption as the household continues to be powered from the solar rather that the solar inverter going offline and resulting in 100% of your consumption coming from the grid while its offline.

Steve

[BradC]

My take on that device is that it will stop your inverter seeing the high grid voltage and shutting down.
It won’t help with the solar harvest being fed back into the grid, but will reduce your power consumption as the household continues to be powered from the solar rather that the solar inverter going offline and resulting in 100% of your consumption coming from the grid while its offline.

Steve

I've been trying to figure out how it works, and the only think I keep coming up with is it's some form of switched converter which can take anything > 225VRMS and regulate it down to 225VRMS. Certainly possible, but it seems like a completely mental solution to a "problem". It'd also theoretically and necessarily completely block any supply *to* the grid. I'm sure it has a bypass to allow that when the grid voltage is low enough to allow in-feed.

I'd love to get some technical information, and some real efficiency numbers because I can't for the life of me think of any other way to achieve what it purports to achieve.

I'd also love to see what distortion it presents to the grid.

[cjc_td5]

What make and model inverter do you have - that’s different from any other system I’ve heard of - usually you use what you want and any you aren’t using goes back to the grid if it is available to take it (ie the local grid voltage not being too high). Grid power is only used when you are consuming all of the available solar or it’s dark, etc.

Why would a system be designed to not give the grid power OR you power - that doesn’t make any sense.If the inverter could differentiate like that, why doesn't it keep supplying the house when the grid power is off? I've no technical backup at all, but I'd say it just shuts down if the grid supply is out of spec (ie too high or too low...)??

[BradC]

If the inverter could differentiate like that, why doesn't it keep supplying the house when the grid power is off? I've no technical backup at all, but I'd say it just shuts down if the grid supply is out of spec (ie too high or too low...)??

They shut down when the grid power is too high to try and keep things under control (prevent the voltage being pushed higher). They shut down when the grid loses power to prevent them energising a disconnected part of the grid and electrocuting a linesman (islanding).

Before Western Power got their **** together here (around 2012/13), we used to see surges up to 270V on a hot summers day with fast moving cloud cover.

[slug_burner]

PV inverters will usually disconnect from the grid when the grid is out of spec. It is only when you have a battery that you can make use of the PV coming off the roof if you lose the connection to the grid.
Sure would like some batteries but the economics of batteries are still not there for most people. I will go that way for ideological reasons to do my bit to reduce our carbon output.

[Graeme]

PV inverters will usually disconnect from the grid when the grid is out of spec. They are legally required to disconnect.

[cjc_td5]

They are legally required to disconnect.Agreed. My point was that when the grid drops out the inverter turns off rather than try to supply the home only. If the grid voltage is too high, does the inverter turn off or try to supply the home only?

[BradC]

Agreed. My point was that when the grid drops out the inverter turns off rather than try to supply the home only. If the grid voltage is too high, does the inverter turn off or try to supply the home only?

How can the inverter “try to supply the home only”?

[Tombie]

Agreed. My point was that when the grid drops out the inverter turns off rather than try to supply the home only. If the grid voltage is too high, does the inverter turn off or try to supply the home only?

It cannot do so unless you have a battery style system with some significant smarts- then it can charge the battery and the battery supplies the home.

A conventional unit is essentially 2 wires attached to the house side of the meter. If it’s producing it contributes and what isn’t “taken” by the house is forced through the meter into the grid.

There’s no control system to lock out the network and regulate power to the house.

[cjc_td5]

How can the inverter “try to supply the home only”?

I think Gav (Homestar) made an observation earlier in the thread that the inverter supplied the home first then cut supply to the grid if the voltage was too high. I don't think they are that smart, if the grid voltage is too high the inverter simply turns off? I made the comparison to a "grid off" scenario where there would be an opportunity for the inverter to supply the house only (subject to balancing, brown out and all sorts of issues of course) isolated from the grid, but it chooses to just turn off completely.

[BradC]

I think Gav (Homestar) made an observation earlier in the thread that the inverter supplied the home first then cut supply to the grid if the voltage was too high. I don't think they are that smart, if the grid voltage is too high the inverter simply turns off? I made the comparison to a "grid off" scenario where there would be an opportunity for the inverter to supply the house only (subject to balancing, brown out and all sorts of issues of course) isolated from the grid, but it chooses to just turn off completely.

Tombie described it pretty well. These inverters are "grid-tie". They are designed to feed power back into the grid. As they are on the consumer side of the meter, any power consumed locally doesn't register on the meter. Any power produced above that consumed locally causes the meter to record it as being fed back to the grid. Conversely, any power consumed which exceeds the output of the solar system comes from the grid and is metered as power consumed. There is no methodology by which these devices can disconnect the grid from the house, so there is no way they can operate when the grid fails. If they were to operate, they would be trying to power the segment which is disconnected with potentially catastrophic results.

Being able to be on-grid/off-grid is a more complex arrangement with requirements for transfer switches and a whole host of safety interlocks to prevent islanding. No different to the use of whole house generation really.

Likewise, when the grid voltage rises above the threshhold, these inverters have to stop producing to protect the grid (and connected devices) from uncontrolled voltage rise. There's no way to say "the grid voltage is too high, so I'll just supply the house".

[Graeme]

The inverter, if correctly configured, will throttle back to effectively produce nothing rather than shut-down, then ramping up quite quickly as the voltage drops either by loads from household appliances or the grid voltage drops. My inverter had incorrectly had its voltage limits changed by the installer attempting to account for a 5-6V drop between the inverter's sensor at the meter box and at the inverter itself some 20m away, but the incorrect parameters caused the inverter to shut-down within 1 second of the voltage hitting the disconnect limit seen at the meter box which then took a few minutes to restart.

After I discussed my suggested voltage limits with the local Essential Energy inspector, the installer reset most of the voltage limits to my suggestions and in 18 months the inverter has only dropped-out once.

[edddo]

Today my retailer/installer came out and made an adjustment to the inverter threshold ( if that makes sense?).
He adjusted it up from 253v to 258v, apparently.
Then said that all new installations around here are set at 258 currently, on advice from distributor, Ausnet.
So if mine was throttling every time the grid went over 253(or maybe lower)..which is basically the middle 6 hours of the day on a sunny day this time of year..then this should make a very significant difference. I suspect he should have done this when I first raised it with him many months ago.

[Gav 110]

There's no way to say "the grid voltage is too high, so I'll just supply the house".

The grid voltage only becomes to high if there is no (or not enough) load and all the inverters in the grid area are trying to force the power being produced into the grid
If you are consuming power when your system is producing its peak power, then there will be no need for it to generate a higher voltage to push it back into the grid, therefore going into over voltage fault mode
As suggested before, if you can set your appliances (dishwashers, washing machine, pool pumps, hot water system etc) to turn on when your solar system is producing its peak power you will alleviate this situation
I have setup for customers Current Transformer Relays to boost a secondary element in there hot water system (standard (upper) element thermostat set at 55-60, secondary (lower) element thermostat set at 65-70)
A couple of years ago but I’m sure this is the current transformer used
Model MSCS | Miniature Current Switch is a low cost solution for monitoring on and off status of light to medium current loads in compact spaces. Applications include BAS, HVAC, small industrial motors, refrigeration, pumps, fans, and lighting. | Dwyer Instruments (https://www.dwyer-inst.com.au/Product/ProcessControl/CurrentTransformers-Switches/ModelMSCS#specs)
With a 24volt control system and contactor

[emoji481][emoji481]

Gav

[BradC]

The grid voltage only becomes to high if there is no (or not enough) load and all the inverters in the grid area are trying to force the power being produced into the grid
If you are consuming power when your system is producing its peak power, then there will be no need for it to generate a higher voltage to push it back into the grid, therefore going into over voltage fault mode

You'd need a pretty significant load to pull your incoming voltage down such that it is below the threshold at your metering point. You're effectively relying on your lead-in and consumer mains to have sufficient resistance to drop that, and then making sure your inverter isn't pushing it back up to the cutoff.

[Gav 110]

You'd need a pretty significant load to pull your incoming voltage down such that it is below the threshold at your metering point. You're effectively relying on your lead-in and consumer mains to have sufficient resistance to drop that, and then making sure your inverter isn't pushing it back up to the cutoff.

The idea is not to pull down the incoming voltage, it is to use the power that your solar system is producing Incoming voltage should not be at the threshold as the inverters on neighbouring solar systems will (should) have shut down
It is your own inverter trying to push the power into the grid
If your solar system is always cutting out on over voltage fault then in my opinion you have wasted your money on a system that is producing too much power that you are not using, maybe money better spent on LED lighting to lower your power usage when your solar system isn’t producing power (night time)

[emoji481][emoji481][emoji481]

Gav

[Old Farang]

I put this here as a general observation for those that are involved with PV systems. This article is not recent, so the over voltage problem is not new., or an unknown fact. Basically, what is being said is that the inverters will require voltage regulation using the grid voltage as a reference to control the inverter output voltage.

The voltage level stability of a grid (at the local transformer) cannot be maintained at a steady linear level just by tap changing. On the other hand, voltage regulation of an inverter can be controlled to match the grid voltage in a linear fashion electronically. In simple terms, the output load of the inverter, just as with a engine driven generator, has to be matched to the grid voltage to limit the load on either source.

(PDF) Voltage regulation via photovoltaic (PV) inverters in distribution grids with high PV penetration levels (researchgate.net) (https://www.researchgate.net/publication/260736407_Voltage_regulation_via_photovoltaic_PV_i nverters_in_distribution_grids_with_high_PV_penetr ation_levels)

[rover-56]

The inverter, if correctly configured, will throttle back to effectively produce nothing rather than shut-down, then ramping up quite quickly as the voltage drops either by loads from household appliances or the grid voltage drops. My inverter had incorrectly had its voltage limits changed by the installer attempting to account for a 5-6V drop between the inverter's sensor at the meter box and at the inverter itself some 20m away, but the incorrect parameters caused the inverter to shut-down within 1 second of the voltage hitting the disconnect limit seen at the meter box which then took a few minutes to restart.

After I discussed my suggested voltage limits with the local Essential Energy inspector, the installer reset most of the voltage limits to my suggestions and in 18 months the inverter has only dropped-out once.

My inverter (Fronius Primo) with 5.2kW panels has an internal limit set by the installer to limit grid feed in to 4kW. I think this is separate to the ultimate shut down setting if the grid voltage goes too high.
It also switches a relay to connect the HWS in at the element wattage (3.2kW). So the inverter rarely reaches the 4kW feed in limit anyway.
Terry

[Graeme]

Yes, the export limit is unrelated to voltage. For Essential Energy in NSW the single phase limit is 5kw but my installer wanted to set mine lower for no good reason but set it to my requested 5kw. I also requested access to allow load management changes so now I have full load management and export configuration control via the web page.

Mine's a Primo 8.2 with 8kw of panels that often gets to 8.3kw on bright, cool days when the 3.6kw HWS is heating. I usually have ON set to very slightly under 5kw to delay switching on as late as possible to maximise export for the day.

[Old Farang]

Yes, the export limit is unrelated to voltage.
There may well be an export limit in Kw's set by the grid provider, but the voltage IS what is "pushing" the amps into the grid. It is no different than any other electrical source feeding a load. The "generator" (be it whatever) voltage output has to exceed that of the grid, or plain and simple, amps cannot flow into the grid if isn't. It is by how much the voltage exceeds that of the grid that regulates how much current can flow.

[Graeme]

But throttling back because the export limit has been reached has nothing to do with any voltage limit.