Sufering from inverter stall due to overvoltage on the grid. Can we use ESS with AC coupling to store solar energy in battery while grid voltage is too high and discharge battery in the grid when grid has correct voltage?
asked
Can we use ESS and AC coupling to avoid losing production when grid volatge is too high?
Yes, you can configure certain boundaries, when a "grid loss" should be detected, such as Over/ undervoltage or over/underfrequency.
In either case, the inverter then will switch to invertermode, isolate the grid and use the batteries / ac-coupled pv.
You just have to take care that the ac-coupled inverters support it, some inverters wont turn on, when not grid-connected.
Also mind the Faktor 1 rule, when using ac-coupled PV in offgrid situations.
Issue: When MP2 detect ACin voltage above grid code limit, it disconnect ok, but in the same time MP2 increase frequency on AC-out which disconnect the AC coupled PV inverter. No production to battery at all anymore while ACin is above grid code limit.
Is there a workaround to this to have PV prodcution inspite of grid issue?
Setup: MP2 GX, Pylontech battery, AC coupled PV inverter 4 kW.
It is intentional that the Multiplus start to regulate the AC-Out-Frequency to control AC-coupled PV. When the batteries are full the Multiplus need to be able to turn of AC-coupled PV.
the system should bring the AC-coupled Inverters back online, when required. In My case (Also Pylontech Batteries) I also found that this is not happening "as expected".
So, during the Configure Process, you can also set a PV-restart voltage. By default this is 45V, which is maybe -300% Soc for the Pylontechs :P
you can adjust this to bring the AC-coupled PV online at higher DC-Voltages. I've set it to 49V, which is roughly 50% soc.
(in the ESS Wizzard)
Thought about this Option for a while - you ddidn't mention any DC-coupled PV? So, apparently the condition "Batteries enter Bulk" will never be true for your setup - because without DC-PV it can't do that, while AC-PV is turned off.
Hence, I assume the PV restart Voltage is the only thing that kicks in for your system, therefore a voltage matching 50-70% SoC should be what you want here. (Dunno how too high values behave, but in theory it wouldn't hurt to try to keep AC-PV online to maintain a SoC of ~ 90% while the sun is available)
How big is your MP2? I see from yr other post you have 4kW of PV, does this infringe the 1:1 rule?
The MP2 should only go into frequency shift mode when the battery is full and the PV output exceeds the local loads. This is what mine does, after a while the battery is slightly depleted and will accept charge again, the cycle repeats every 10 minutes.
Check what the output/frequency characteristic of the inverter is, you may need to adjust the frequency settings in the ESS Assistant. My settings are below:
Our MP2 GX is a 5kA. The issue is other. When the grid voltage is out of psec versus the grid code limits, The MP2 seems to be looking at grid quality by increasing frequency. Thus increase goes to ACout also and disconnect the AC coupled inverter on ACout.
Why does the MP2 do that? Is there a workaround?
As far as i know its completly normal behavior, the multi is not a protection device, it disconnects grid because overvoltage is also used to stop the multi feeding back power to grid just like the regulations on pv inverters have
if your grid is unstable and voltage is to high many times, put in a grid monitor/grid protection relay, then grid gets disconnected when overvoltge is there and switches back when normal
The multi is disconnecting grid when voltage is to high, but still monitors it, thats why its frequency shifting the pv inverter
Another option could be to replace the pv inverter for mppt’s
Tkx. Do you know of a grid monitor relay that would do and not too priccy?
Ziehl is the well known brand mentioned in the Loss of Mains page here. They are expensive (?>Eur 1000?) and it is not clear to me if it will solve your problem.
I do not understand why the Multi should increase the frequency in grid-rejection mode except in the situation there is nowhere for the PV generation to go, then it has to throttle it for reasons described in the 1:1 rule description here.
It does not do that when the grid is off. Frequency shift then works perfectly. The work around we have is the open the MCB feeding the MP2 to put it off--grid manually. That cannot be a fianl solution.
