On Grid Inverters with multiple MPPT's

[Hugovm]

Hello everybody. I'm working at a company in Brazil that is starting to plan and build PV systems.
We were making some researching new Inverters to buy when a company advertised their product as better than the others with the following claim:
"...some of them with better technical characteristics (you can look at the warranty and MPPT numbers)."

They have from inverters with 1 MPPT up to inverters with 8 MPPT's.
From what I have researched, MPPT's are important to Off Grid systems and batteries, but I haven't found much information about it's use in On Grid systems. Can anyone here explain me that? Does the number of MPPT's impact on the efficience of the system or is it just a scam?

I have done some research on this forum but haven't found anything about this exact question.
Also, sorry for my english. It's not my main language and it's kind of rusty.

[bonaire]

Look at PowerOne (www.power-one.com)

I have two of their string inverters at home - model is Aurora PVI 3.6. Each has 2 MPPT controllers on them. You can read up on their stuff at their web site. They're #2 inverter company in the world behind SMA - so, very trustable. My system is 32 total modules (255W each). Each set of 8 goes into one MPPT.

Let's say you have a roof with two different sides you want to put modules up on. You can use these two MPPT inputs to do that without buying two inverters.

[Hugovm]

So from what I have understood, the MPPT number is also the number of strings that I can input on the inverter, considering 1 string per MPPT.

From this, may I assume that a higher number of MPPT's is better because it will allow smaller strings and therefore a better control from the MPPT?
Also, I don't quite get the beneffits for a On Grid system. I understand that batteries will limit the output without the MPPT. The grid however will not limit the output in this way. Is the only beneffit the weather output correction?

[inetdog]

but I haven't found much information about it's use in On Grid systems. Can anyone here explain me that? Does the number of MPPT's impact on the efficience of the system or is it just a scam?

Whether the energy is going to a battery charge controller (CC) or to a grid tied inverter (GTI) the solar panels themselves have the property that to get the maximum power from them the load needs to be able to separately adjust the voltage and the current drawn. A simple resistor or a simple constant voltage input will not extract all the possible power as the light level on the panels (and therefore the current) varies.

Any time you have different panel types, different numbers of panels, or different partial shading effects in two or more strings of panels, you will need to send only identical strings to one MPPT input.

Now it turns out that is there is no partial shading you can have otherwise identical strings with different facing directions combined into one MPPT input. (Unless there is a really big temperature difference between them.) But you will have more flexibility and better monitoring if you send different facing arrays to different MPPT inputs too.

It is not a scam in the sense that MPPT really works and gets you more power. It also allows you to use even higher voltages per string into a GTI and thus save on wiring costs.

To some extent you can mix together strings with different current ratings or different voltage ratings if you have only one MPPT input. The rule of thumb is that the Vmp values (for parallel) or the Imp values (for series) should not differ by more than 5%. But this is a rule of thumb only. In some cases you can tolerate a much larger mismatch.

[Hugovm]

Thank you for your answers! They helped quite a lot!