Optimal PV Panel String Connection: Inverter & Panel Parameters for 210-480V MPPT Voltage Range

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#1 16278067 14 Feb 2017 13:14

Anonymous Anonymous

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Post #1
16278067 14 Feb 2017 13:14

Hello.

How many PV should be connected in one string to be the most optimal, assuming that all strings are connected only to MPPT inputs?

Taking sample parameters of the inverter:
- Voltage from MPPT PV panels: 210-480V
- Nominal PV voltage: 360V
- Maximum PV current: 26A
- Maximum PV short-circuit current: 15A

and examples of PV parameters:
- Isc: 3.9-9.7 A
- Voc: 18.0-20.2V

I assume that the best connection (counting by voltage) will be 360V / 20.2V = 17 panels (or maybe you should take 480V / 20.2V = 23 PV?).
while counting on the current 26A / 9.7A = 2.7 (string), that is a maximum of two strings tied to one input.

Are the assumptions about the calculation method correct? Please justify your answer.
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#2 16278397 14 Feb 2017 15:36

franekmigas franekmigas

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Post #2
16278397 14 Feb 2017 15:36

By the parameters, I can see that they are monocrystalline panels, could you please send me the name and type of the inverter and panels?
#3 16278434 14 Feb 2017 15:56

Anonymous Anonymous

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Post #3
16278434 14 Feb 2017 15:56

franekmigas wrote:
...

The data of the inverter and panels are examples (but real). If you think it matters then I will send you the models. However, I am interested in the general method of selecting the amount of PV and not this particular case.
#4 16278519 14 Feb 2017 16:32

franekmigas franekmigas

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Post #4
16278519 14 Feb 2017 16:32

You should pay attention, first of all:
Panels - voltage and maximum current
Inverter - DC voltage and maximum current
and then you choose the number of panels in a string and how many strings you can connect with each other
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#5 16278841 14 Feb 2017 18:40

putas putas

Renewable energy sources specialist

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Post #5
16278841 14 Feb 2017 18:40

If it is possible, we connect them in series so that the total operating voltage of the panels under load is close to the suggested operating voltage of the inverter.
Besides, there are three parameters that we do not exceed
- max inverter input voltage - i.e. one string without load cannot exceed this voltage, we even leave a few% slack, on a frosty and sunny day the panels can output a voltage slightly above the norm
- max input current of the inverter - that is the total max current of all strings
- the total power of all panels does not exceed 115-120% of the inverter power
#6 16278865 14 Feb 2017 18:47

Anonymous Anonymous

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Post #6
16278865 14 Feb 2017 18:47

putas wrote:
If it is possible, we connect them in series so that the total operating voltage of the panels under load is close to the suggested operating voltage of the inverter. ...

Which one

Quote:

Taking sample parameters of the inverter:
- Voltage from MPPT PV panels: 210-480V
- Nominal PV voltage: 360V

are you able to write without looking at the manual for details, is it 480 (maximum) or 360 (optimal)?

If it is optimal (360), will I produce less energy by connecting the string in 460 than if I combined the string in 360 or not to worry about it and the MPPT will lead the 460 to the right point.
#7 16278895 14 Feb 2017 18:54

franekmigas franekmigas

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Post #7
16278895 14 Feb 2017 18:54

You still need to know the maximum DC input current of the inverter
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#8 16278981 14 Feb 2017 19:18

Anonymous Anonymous

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Post #8
16278981 14 Feb 2017 19:18

franekmigas wrote:
You still need to know the maximum DC input current of the inverter

Yes, yes .. thanks. For now, I am investigating V
#9 16279126 14 Feb 2017 20:03

krzysiek_krm krzysiek_krm

Level 40

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Post #9
16279126 14 Feb 2017 20:03

Hello,
Without analyzing the documentation, or asking the manufacturer what he meant, it is difficult to say anything meaningful.
It is possible that the nominal voltage was given just like that, but it is possible that it is actually optimal, for example the inverter achieves the highest possible efficiency at this voltage, which is quite advantageous, because then the maximum power of the device can be obtained.

greetings
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#10 16279164 14 Feb 2017 20:12

franekmigas franekmigas

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Post #10
16279164 14 Feb 2017 20:12

2 examples from my installation.
#11 16279295 14 Feb 2017 20:46

Anonymous Anonymous

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Post #11
16279295 14 Feb 2017 20:46

krzysiek_krm wrote:
Hello,
... it is possible, however, that it is actually optimal, for example the inverter obtains the highest possible efficiency at this voltage, which is quite advantageous, because then the maximum power of the device can be obtained.

I understand that we are "if we are". So what about MPPT?
Does (assuming the phrase "optimal" is properly used) mean that the MPPT cannot squeeze the right power point (read - voltage) from the PV and therefore should be connected as close as possible to the optimal voltage point or will MPPT do the trick?

Let's not stick to my example - describe it from your own installations, from your own experience: should you find the optimal voltage or connect the maximum voltage (with comments from my colleague putas) and the rest will be taken care of by MPPT?

Or maybe each inverter is so different that you should ask the manufacturer for details (or from the manual), as suggested by his colleague krzysiek_krm?
#12 16279385 14 Feb 2017 21:13

franekmigas franekmigas

Level 11

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Post #12
16279385 14 Feb 2017 21:13

I have 2 installations.
1: Mastervolt XS3200 + 40 panels GS-50 (4 strings * 10 panels) max voltage 580V
2: Mastervolt XS2000 + 4 panels Q.Cell Q.PRO - G4.1 265W (1 string), maximum voltage 140V
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#13 16279452 14 Feb 2017 21:33

3301 3301

Level 34

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Post #13
16279452 14 Feb 2017 21:33

And don't you think that in the case of 2 installations you have a little too low voltage, in this MPP inverter the range is from 145V and you have 140 and maybe that is why the efficiency of the 2nd installation. is lower by approx. 1% than the installation. 1.
Tomorrow I have to receive such an inverter only XS 6500, I will start testing it.
#14 16279470 14 Feb 2017 21:40

franekmigas franekmigas

Level 11

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Post #14
16279470 14 Feb 2017 21:40

Very good 2 MPPT inverter, so the possibilities are very large
#15 16279485 14 Feb 2017 21:45

3301 3301

Level 34

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Post #15
16279485 14 Feb 2017 21:45

Probably a better solution would be two of them after 2000, but there was a bigger one and the price was much lower than two
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#16 16279505 14 Feb 2017 21:49

prose prose

Level 35

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Post #16
16279505 14 Feb 2017 21:49

Here is a simple diagram that MPPT will not do everything on the example of the Fronius IG 60 HV inverter, giving the DC input max voltage is lost on production.

Here is the inverter data.
#17 16279507 14 Feb 2017 21:50

franekmigas franekmigas

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Post #17
16279507 14 Feb 2017 21:50

this 6500 is really 2x3200 in electronics and 2000 is a pile worth nothing
#18 16279523 14 Feb 2017 21:53

3301 3301

Level 34

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Post #18
16279523 14 Feb 2017 21:53

It made me feel good, although I was not aware of it
#19 16279538 14 Feb 2017 21:57

franekmigas franekmigas

Level 11

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Post #19
16279538 14 Feb 2017 21:57

those that have the inscription on the right side of the plate work the longest
MADE IN PRC
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#20 16279548 14 Feb 2017 22:00

prose prose

Level 35
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Post #20
16279548 14 Feb 2017 22:00

I tried on high, low and medium and 280V as in the chart I got the best results, each inverter has its best working point at MPPT point.

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#21 16279712 14 Feb 2017 23:03

Anonymous Anonymous

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Post #21
16279712 14 Feb 2017 23:03

Thank you, you can always count on the old guard ;)

as for me, the topic is closed - I will wait a day, maybe someone will want to comment - but please comment on the topic.
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Topic summary

The discussion centers on optimizing the connection of photovoltaic (PV) panels to an inverter with a specified MPPT voltage range of 210-480V. The main inquiry involves determining the optimal number of panels to connect in a string, considering the inverter's nominal voltage of 360V and maximum current specifications. Participants emphasize the importance of matching the total operating voltage of the panels to the inverter's optimal voltage for efficiency, while also adhering to the inverter's maximum input voltage and current limits. The consensus suggests that while the MPPT can adjust to varying voltages, connecting panels closer to the optimal voltage can enhance performance. Examples of installations and inverter models are shared, highlighting the practical implications of these calculations.
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