Dealing with excess solar:

[Lincs Robert]

Hi,

Now that the weather is a bit sunnier, I’m sure we are all starting to see issues regarding excess gross capacity with our solar PV systems. In order to get enough capacity through the winter we end up with too much capacity in the summer - as even after storing as much as possible in batteries means that we end up exporting large amounts of power. Many people are limited in how much they can export - so if we’re not careful, we end up with potentially exporting more power than we’re allowed - which can cause our DNO problems. I’ve been pondering this and have come up with a solution the early testing of which works. However, it only applies if you have solar edge inverters, which I have.

There’s a feature on Solar edge called RRCR. This is designed to limit the amount of power an inverter generates and, in certain territories such as Australia the inverter is connected to an external control unit which is under the control of the DNO. This gives the DNO the ability to reduce the output to 60% 30% or zero and then back to full power again. It’s very neatly implemented by solar edge but the documentation is a little confusing and spread across a number of their application notes. Also, it isn’t particularly well documented in the installation manuals. However, I’ve managed to piece it all together, make sense of it and get it working.

RRCR control is implemented by a four input pins on the GPO interface board. By connecting a number of relays to these inputs and configuring the feature, it’s possible to control the maximum power output of the inverter in a series of steps. I’ve tested this using a simple pushbutton arrangement which works and gives me the ability at the push of a button to select hundred percent, 60%, 30% or zero output from my inverter. The next step is to connect these inputs to Wi-Fi switch devices under Alexa control. This will give me the ability to simply command the inverter to step its power down or up, either from home or anywhere using the Alexa app.

I can see a scenario where the output is set to 100% until such time as the batteries are charging and then reduced to limit export. this can be done by looking at the app and deciding what action to take or perhaps having it under time of day control based on experience of similar days.

Following my testing, I now have to properly install all of this and get it working. To complicate things slightly, I have a number of solar edge inverters the first one is my feed in tariff device which I don’t wish to control at all. It’s additional inverters that need to be controlled in this way.

There are four inputs, L1,2,3,4. Solar edge have pre-configured a number of the 16 possible state combinations to give these % steps. The other states are not defined, but could be. So you could set steps to be anything you want & by presenting the L inputs from the relays to match the reduction state is implemented. Once a state is in place, it stays there until a new state takes over, or at midnight reverts to 100% again - ready for the following day.

All in all a very neat little feature, hidden in plain sight.

I’m hoping that this information is of interest to people. I will keep you appraised as things progress but wanted to give a bit of early insight as I’m not sure if people are aware that their solar edge devices have this capability.

All the best - Rob

[Fintray]

Hi Rob

I had the same problem in that at certain times my export from my Solaredge inverters was pushing up the mains voltage to around 260V, which when it was clear skies was ok. However when there was some clouds passing over the sudden ramp up of voltage after a cloud cleared the sun caused my SMA SunnyBoy inverter to trip out then it had to go through its reconnection process, this could happen several times a day.
As the SunnyBoy is on my FIT's system I want its output to be as high as possible and not have it stopping and restarting.

To overcome this problem I adjusted the active power control of the Solaredge inverters so that as the voltage rose the power would be gradually reduced to prevent it getting so high, I also reduced the Wakeup gradient time to slow down the rate of increase in power which helps when there are clouds passing over.
It's been a couple of years since I did this and it seems to be working fine.

[Lincs Robert]

Hi Rob

I had the same problem in that at certain times my export from my Solaredge inverters was pushing up the mains voltage to around 260V, which when it was clear skies was ok. However when there was some clouds passing over the sudden ramp up of voltage after a cloud cleared the sun caused my SMA SunnyBoy inverter to trip out then it had to go through its reconnection process, this could happen several times a day.
As the SunnyBoy is on my FIT's system I want its output to be as high as possible and not have it stopping and restarting.

To overcome this problem I adjusted the active power control of the Solaredge inverters so that as the voltage rose the power would be gradually reduced to prevent it getting so high, I also reduced the Wakeup gradient time to slow down the rate of increase in power which helps when there are clouds passing over.
It's been a couple of years since I did this and it seems to be working fine.

Thanks for the feedback. So my main SE inverter (FiT) isn't controlled at all. On the others I've already implemented site export limitation - which helps, but only to a point. This will be an additional level of control implemented at very little cost - which means I’ll be able to turn things down if I wish - which I cant do at the moment. The RRCR implementations in Australia see a simple radio receiver connected to the inverter & the utility company can simply reduce inverters in a particular area if they are seeing over voltage caused by lots of solar export on sunny days - of which there are a lot!

[Fintray]

Yes I can see the need for the RRCR control being activated in Australia with the amount of rooftop solar and the constantly high insolation compared with us in the UK. Our usual mains voltage is around 250V as we are near the end of a rural circuit.

[dan_b]

What does RRCR stand for?

[Fintray]

RRCR – Radio Ripple Control Receiver.

[sharpener]

There is a related issue whereby with a lot of generation it can be better to charge the battery at half the rate for twice as long so you are not trying to export above your limit as soon as the battery is full.

This is potentially an attractive thing to do as I don't think my DNO will agree to me exporting more than 16A bc the voltage peaks at over 250V most days now. ATM it is academic as I don't yet have a smart meter so am not on Outgoing and not losing any revenue. Once I get the HP and smart meter fitted things will change.

The downside is the risk the sun will go in and the battery will not reach 100% SoC. So I am hoping that either I can automate the decision process using the daily forecast and Node Red, or Victron will add this functionality to their evolving Dynamic ESS software.

Anyone already doing this, and how?

[Mart]

Also, for a DC side battery, especially with the massive Wp overcapacity that Solaredge inverters can handle (up to 200% of rating), then it may be wise to prevent the battery filling before peak generation, so that the inverter output + battery diversion, doesn't fall short of generation.

PS - My SE inverters shutdown temporarily if grid voltage reaches 253V. Hasn't happened for many years.

[Joeboy]

There is a related issue whereby with a lot of generation it can be better to charge the battery at half the rate for twice as long so you are not trying to export above your limit as soon as the battery is full.

This is potentially an attractive thing to do as I don't think my DNO will agree to me exporting more than 16A bc the voltage peaks at over 250V most days now. ATM it is academic as I don't yet have a smart meter so am not on Outgoing and not losing any revenue. Once I get the HP and smart meter fitted things will change.

The downside is the risk the sun will go in and the battery will not reach 100% SoC. So I am hoping that either I can automate the decision process using the daily forecast and Node Red, or Victron will add this functionality to their evolving Dynamic ESS software.

Anyone already doing this, and how?

We topped out the increased size stack yesterday. HWT was full and EV was out and about so nowhere to put it. We only suffer from this for about 6 weeks per year. It was only 5 minutes.

Will be interested to see the development of automation side. I do mine remotely but manually if that makes sense. Bringing in voltage sensing smart switches which can be software triggered by a weather app sounds good. Although I'd think it simpler to stick to a switch or relay that triggers at a set voltage. N/O & N/C smart relay would get you there?

[sharpener]

Also, for a DC side battery, especially with the massive Wp overcapacity that Solaredge inverters can handle (up to 200% of rating), then it may be wise to prevent the battery filling before peak generation, so that the inverter output + battery diversion, doesn't fall short of generation.

PS - My SE inverters shutdown temporarily if grid voltage reaches 253V. Hasn't happened for many years.

Not sure I quite understand.

My DC side MPPT is what gets controlled to limit production, in order to preserve max generation hence income from the older FIT setup. Also the Victron can turn down the MPPT at will, but can only shut off the old Steca inverters by frequency control and that only in off-grid (power cut) mode.