Large scale solar park design

[acog]

Hi Guys,

In summary the question is: is it ever deemed a more economical solution to parallel PV modules before the combiner box (i.e. series AND parallel connections in a 'string' of PV panels) for a large scale solar PV project?


Some more detail:


When designing a large scale solar project, do you typically connect all PV modules in each string [highlight #FCE94F]in series only[/highlight] then parallel at the combiner box such that the desired open circuit DC voltage of each string is just under the DC input voltage limit for the inverter?

Example- individual module open circuit voltage is 48 volts, inverter DC input voltage limitation is 1000VDC, then 20 panels in series per string would be used (960V string max voltage).

OR

Is it more economical to connect a combination of [highlight #FCE94F]series and parallel[/highlight] PV modules before the run to the combiner box to make the most of the string cable current carrying capacity, which might otherwise be oversized for mechanical strength reasons if only a series solution was performed.

Example- individual module open circuit voltage is 48 volts, inverter limitation is 1000VDC, then 80 panels could be used per string, with four times the string current and the same open circuit voltage.


Solar PV cable comes in various sizes (standard PV1-F of TUV 2 Pfg 1169/08.2007), from 2.5mm up to 10mm twin or single core either 4mm or 6mm.

Thanks in advance for any input.

 

[cranky108]

Sorry to say, but many of us don't work much with low voltage such as with solar panels, or with DC systems outside of battery control systems. So I'm not sure how much help we can be.

Actually we have a solar contractor do this, and we take the 13 kV from the step-up transformer.