Multi mppt function and Power sharing

[Johng9i]

Hi to all,

I am an electrical engineer student and i would someone to explain me the "Multi mppt function and Power sharing" on pvsyst with simple words and examples.

 

Thank you in advance.

 

John

[Muhammed Sarikaya]

Hi John,

I will show you a simple example of how to use the multiple MPPT feature.

Let's say you have an inverter with 2 MPPT entries and you want to define each of them.

First, you need to create two sub-arrays as below. When you select the first subarray, all the parameters you define are independent of the second subarray. This means that you have to select the second inverter to set all the parameters independently.

To begin, the first subarray defines one MPPT entry of your inverter. Be careful, the box labeled "Nb of MPPT inputs" should be set to 1, meaning you are configuring only one MPPT entry of the inverter. You decide to configure 15 modules in series and 1 string. See below:

 

Then, you select the second sub-array and you have to enter "1" in the box "Nb of MPPT inputs" to define only one MPPT entry of the inverter. Also, because its entry is different from the first subarray, we decided to define 18 modules in series and 1 string. See below:

 

Next, you need to set up "Power Sharing."

Click on the "Power Sharing" button.

Follow these steps to set it up, see below:

 

You have to move the sub-array from the right to the left under the inverter.

I hope this helps you understand how to use the multi-MPPT feature and power sharing.

 

Regards,

Muhammed Sarikaya

[LauraH]

Hi,

Normally, we model mixed module blocks by finding an equivalent block that uses just one module model.  Could we accommodate a mixed block using the multiple MPPT feature?  If the block only contains two module models that are identical except for bin class, say 445s and 450s, would that make a significant difference to the production on that inverter (due to differences in inverter operation, not just the module rating)?  I'm wondering whether it's worth the effort to represent the block more specifically.

Thanks! 

[dtarin]

Yes, it is typical to use the MPPT feature to model mixed blocks and good practice. It doesn't necessarily need to be due to different bin classes, loading ratios are also relevant even with a single bin (clipping is non-linear). This is of course dependent on the inverter in question, design, etc. 

With regards to representation, what's "significant" is dependent on project details and opinion. A mixed bin design on a single mppt will be more impactful due to increased mismatch losses, which are up to the user to define. Modeling this in PVsyst using the mppt sharing feature and creating distinct sub-arrays allows one to specify mismatch individually, and documenting this in reporting is good practice. If all of these differences are averaged out, is there a difference in production? I am not sure, but it would probably take the same amount of time to model individually as it would to determine these average values and model as a single sub-array.

Edited January 8 by dtarin