question

eyub avatar image
eyub asked

How to limit inverter power in ESS system

hello i am new to Victron

we have installed our first Victron system Quatro 10kva with 4 x 300 ah 12.8v Lithium batteries, the system is ESS with grid-connected and possible grid shortages during the day, and 11.52 kwp PV is installed and connected to the system through 2 x 250/150 MPPT chargers.

the situation is that during the midday 10 am-2 pm the solar is reaching 8000-9000 watt the load is about 5000w and since we activated the feedback to the grid so when the solar is high and the batteries are full the system is overloading since the solar is greater than the inverter 8000kw limit but as far as I know it is ok to oversize the inverter since it will cut off the extra power when it doesn't need it, but it is not doing it it is overloading and shutting down.


my question is that is there a situation where I can limit the solar in the setting that stops inverting more than 8000 watts so as not to overload the inverter ??

when batteries are not full it is ok since the excess solar is sent to the batteries and no issues but it is an issue when the batteries are full and feedback is activated the inverter keeps trying to invert the solar even if it is more than the 8 kW

ESSerror
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @eyub

Yes you can limit the inverter power in the ESS menu

8 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

eyub avatar image eyub commented ·

how you can do that because in the ve configure or in the color control because in the color control i couldn't find where to limit the inverter power

0 Likes 0 ·
Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ eyub commented ·

Hi @eyub

in the GX device, in the ESS menu:


1 Like 1 ·
screenshot-2020-06-14-212135.png (89.4 KiB)
dcsonka avatar image dcsonka Daniël Boekel (Victron Energy Staff) ♦♦ commented ·
Hello Daniel,


Does this mean that without switching on the inverter power limitation in the GX, I would be literally able to overload the inverter in certain cases?

Isn't there a built in protection in the Quatros/Multis limiting their output power to the nominal (datasheet max) value by default?

I experienced the same behavior, like above described. My Multiplus 3K had a constant load of 3.5kW on its ACout for about 10min when I noticed and switched off some of the loads in order to prevent from frying my Multi. The PV power + battery combined was enough to give 3.5kW constant input to the inverter, so it just did its job and kept inverting whatever the load was requesting on the ACout.

I expected that the grid would kick in as soon as I am over the inverter's max load.

The question is if i switch on and set the inverter's max power, then it corresponds to per Multi (I have a 3phase system) or the combined power of the 3 Multies?


Thanks


Dezso

0 Likes 0 ·
ejrossouw avatar image ejrossouw dcsonka commented ·

@dcsonka I suggest upgrading to the latest 2.93 firmware and look at the features below as opposed to limiting the inverter.

1681233750589.png



0 Likes 0 ·
1681233750589.png (31.0 KiB)
dcsonka avatar image dcsonka ejrossouw commented ·

Hi, I have this firmware, but switching on the DC-coupled PV excess will not protect the inverter, quite the contrary, the inverter will push the excess energy back to the grid without limitation, hence, I am frying again my inverter.

Based on what I saw in my install base (as well as the above case), there is no protection on the inverter's output power unless i limit it somehow.

The inverter can be protected two ways:

  1. implement a well over-sized inverter, ensure that your loads are not exceeding the specs of your inverter's output power, that will cost $$$
  2. cut off the inverter's output power at the specs and compensate it from the grid

It seems that the current implementation doesn't work like that. So I can overload the inverter when there is enough power on the DC input side.

When there is not enough power on the DC input side (and there is no grid), then the inverter shuts down with overload.


0 Likes 0 ·
Matthias Lange - DE avatar image Matthias Lange - DE ♦ dcsonka commented ·
Without grid the inverter always tries to deliver the power needed by the loads.

There is no way to limit the output power.

You have AC Out 2 and (depending on the exact model you have) at last one relay that you can use to switch off loads in case of overload.

1 Like 1 ·
ejrossouw avatar image ejrossouw Matthias Lange - DE ♦ commented ·

"I expected that the grid would kick in as soon as I am over the inverter's max load." Implies the system is grid connected and you will also not use ESS for off-grid. Also, as per the original post "the situation is that during the midday 10 am-2 pm the solar is reaching 8000-9000 watt the load is about 5000w and since we activated the feedback to the grid so when the solar is high and the batteries are full the system is overloading" suggesting that while grid connected and exporting from an oversized solar array results in inverter overloads.

0 Likes 0 ·
ejrossouw avatar image ejrossouw dcsonka commented ·

Overloads are possible and shutting down is a last resort as a result of not responding in a timely manner to the warning or simply a poor design by not correctly taking into account the nominal, maximum and occasional peak loads from the outset. I have both an off-grid and ESS system, the latter set to zero export and both see the MPPTs reduce ouput in line with the demand regardless of the fact therer is lots of sunshine.

0 Likes 0 ·
gazza avatar image
gazza answered ·

With DC coupled PV Grid feed NOT enabled then the battery BMS should command the MPPTs to throttle back when the batteries are full and AC loads are small. Does that part work?

However, when DC coupled PV feed-in is "Enabled" that throttling no longer takes place (it's in the manual), so the MPPTs are left to free run to the max they can handle... in the OP's case 150A from each MPPT. I am assuming half the PV on each MPPT ie 5750W? Also assuming a nominal 53V out (? I don't know your details?) then that equates to circa 108A. At peak you could have 216A DC available, just from PV?
The DC coming into the inverter for conversion will be limited by the discharge rate of the batteries and the additional available MPPT output. So, if you are going to have PV feed-in "enabled" I would suggest try reducing the MPPT max output current, this can be done with Victron Connect, >Settings.
I have experienced excessive PV power(..ie more than should be possible) with a smaller system in peak sun with the occasional cloud situation. eg 3600W from 3.2kW of panel. So, don't assume that 11.5kW is the max your system will produce in certain transient conditions.

2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

ejrossouw avatar image ejrossouw commented ·

I agree ... to some extent ;) A dynamic mechanism that ensures the DC solar export and active inverter loads combined does not exceed the inverter maximum output, would be more ideal. For Victron to implement it, I trust will be far from simple. As for limiting output, I am not a fan and personally oversized my PV system for various good reasons by almost 80%. One being that I can charge at 170A from 2 x 250/100 MPPTs if there is only a small 70W baseload. Also, I can comfortably run loads to the 4.4kW max of my inverter while also charging at a still very healthy rate at the same same. I intentionally elect not to export given future inverter upgrades, EV charging etc. will probably still see me come up short as all the possibly space on the roof has already been used for solar. PS - Yes, I did the other day see an 9.5kW blip from my 7.8kW array, but these never last long enough to upset the system.

0 Likes 0 ·
dcsonka avatar image dcsonka commented ·

"With DC coupled PV Grid feed NOT enabled then the battery BMS should command the MPPTs to throttle back when the batteries are full and AC loads are small. Does that part work?"

Yep, this works.

However, my whole haus is connected on the critical loads output. It works pretty well, however, when my e-car is connected to the charger (slow charge, 6Amp/230V 1380W per phase) and we start using other high-power appliances, I can easily exceed the max power of the inverter. I thought, that the inverter will work up to 3kW and then start adding the necessary extra power from the grid. The manual says that it can add 13Amp and the rest comes from the grid. But I think I just misinterpret something here.

0 Likes 0 ·

Related Resources

What is ESS training video

ESS Quick Installation Guide

ESS design and installation manual

Additional resources still need to be added for this topic