Power sharing and oversized inverter

[Emi]

Hello, 

I'm working on a system that has serveral orientations using an inverter with a sufficient number of MPPT, but...

I have 5 orientation, inverter that I have to use has 10 MPPT.

Then, using power sharing I had to change MPPT number in inverter model because PVSyst don't allow empty MPPT.

Power sharing is ok, but PVSyst returns an error message about inverter ovesized.

I would use a single 100kW inverter with 10 MPPT (I changed to 7 MPPT) for all the "Tetto" subarray.

How can I solve this issue?

Many thanks

[dtarin]

You have a very low DC/AC ratio for that inverter. To get around this, go into advanced settings and set the following. If you need to adjust it lower, set the first one there to .01. The inverter is oversized for that design though, so you might be better off with something smaller. 

 

[garf]

Hi, what if the manufacturer said their inverter can't have Power sharing between MPPT? 

if that the case, can we still share the power between MPPT for PVsyst simulation? thanks

[Emi]

On 7/7/2023 at 9:07 PM, dtarin said:

You have a very low DC/AC ratio for that inverter. To get around this, go into advanced settings and set the following. If you need to adjust it lower, set the first one there to .01. The inverter is oversized for that design though, so you might be better off with something smaller. 

 

 

Ok, thanks.

I tried an inverter with lower power.

Now, the sum of my subfields is 44.16kWp and my inverter is 40kWac rated power.

Anyway, I don't understand how to assign the various strings to inverter inputs using "power sharing".

Now, I have 5 strings with 5 different orientations, as per attached image.

Within red lines the problems I'm facing.

Could you suggest any solutions, please?

Many thanks

 

[Lazare Fesnien]

Dear Emi, 

You set one string for two MPPT inputs, it can't work

[Emi]

ok, right,

now I set 1 MPPT for each subarray, 

always 5 orientations.

How could I go ahead to fix the system? Many thanks

 

 

[Lazare Fesnien]

You must use the "power sharing" tool to set the power distribution correctly

[Emi]

 

Clear, but I have 5 orientations and 4 inverter MPPT.

Then, must I use optimizer?

And in this case, how I can assign two different orientations (with modules optimizers) to the same MPPT ?

Tnx

[Emi]

this is the situation about power sharing using optimizer option for the first 2 strings

[dtarin]

8 hours ago, garf said:

Hi, what if the manufacturer said their inverter can't have Power sharing between MPPT? 

if that the case, can we still share the power between MPPT for PVsyst simulation? thanks

Which manufacturer said this? You may not want to power share if it cant be done in the field, otherwise you will underestimate your clipping losses. Take for example you have a DC/AC ratio on one MPPT input of 1.0 and on another MPPT input a ratio of 1.4. The latter will have high clipping losses if you don't have power sharing in field. If the DC/AC ratios are similar or the same, then I think you could be fine, but if they are significantly different, I would not. 

Edited July 10, 2023 by dtarin

[garf]

On 7/10/2023 at 11:02 PM, dtarin said:

Which manufacturer said this? You may not want to power share if it cant be done in the field, otherwise you will underestimate your clipping losses. Take for example you have a DC/AC ratio on one MPPT input of 1.0 and on another MPPT input a ratio of 1.4. The latter will have high clipping losses if you don't have power sharing in field. If the DC/AC ratios are similar or the same, then I think you could be fine, but if they are significantly different, I would not. 

I questioned the huawei sale person regarding power sharing between MPPT. and He told me their inverter doesnt has power sharing between mppt.

But when i asked their engineer if I can put CSI 550Wp x 22PV/string for both input of the MPPT. And he said can as long as the number of PV/string is same for both input.

So, I am also unsure now.

Wonder if anyone psychically doing this in field...can share your experiences? 

thanks

[dtarin]

Yes, as long as string size is the same and the input currents are within inverter spec, you can do anything. But the question is not that, but instead if mppt inputs can be jumpered. With chint inverters, they can, at least for the 50 and 60kw versions. Haven't used string inverters in a while.  We ran into a situation where they weren't jumpered in the field and we were getting high losses/overloading. After they were jumpered, we saw expected performance. havent used Huawei so don't have anything to help you with them specifically at the moment.