When a under performing PV Module/ Low Watt peak Module are connected in a healthy string And String output limited by under performing module. This string limits the output of String combiner box ( SCB ). This SCB Limits the Inverter generation.
Ex.
21 Module connecting in series in a string each 310 Wp & one module of 260 Wp. string output is - 21*260 = 5.460 KW ( 21*310=6.510 KW )
One SCB having 24 String than Output is - 5.460*24=131 KW ( 24*6.510=156 KW )
One Inverter haning 9 SCB INV O/P is - 9*131=1179 KW ( 9*156=1404 KW )
Difference of 50Wp in a Module will make a difference of 225 KW ( 725 Module which is approx to one SCB ).
Is this Correct or Not.
IF Yes Please explain in detail........................
Dear Godara,
I feel the sizing of String Combiner Box (SCB) is done based on the voltage rating of the string. and Based on the voltage rating of the strings only you can decide what size of Inverter would be suitable. This way will give you the limits of both the SCB and Inverter.
In series connected PV panels the operating voltage of PV panels will be same. From the characteristics of the PV panel rated 260 Wp you need to find out the current for the respective voltage. One more point is the current at MPP of 310 Wp panel if the current of both panels are near by then under STC you will get required power.
The key factor deciding it will the voltage at MPP for the PV under different solar irradiance if you can get the data you will have a clear picture.
hope this may help you, all the best
- No that s overestimated if one module makes less power either shaded or soiled or glass breakage it will " mostly " effect the combiner box only.
- Let s assume V x A that s already stated correctly above
- either the one string produces e.g 1 or 2 or 3 Amps less
Depending on MPPT value it will effect strings of combiner box indirectly as well.
You could loose assuming ~ 600 VDC x 7 A = 4200 while other produce depending on modules 8.5 to 9 A ~600 VDC x 8.5 A = 5100 W
very theoretically as funny enough the worst string will also make good strings perform less - acting like a dump load / for All
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