Tigo's optimizers (MLPE: TS4-A-O) can help compensate for production losses due to uneven strings and Mix and Match Different PV Module Types, as long as the variance (between the parallel strings' output) remains below 25%.
Design Note: TS4-O can mitigate losses caused by mismatch, but it cannot compensate for insufficient irradiance or for system designs outside Tigo’s recommended limits, such as parallel strings with more than a 25% difference in string length.
For more info on this topic, see: Designing your TS4 system for different tilts, angles, and orientation
Design Considerations:
Uneven string management requires Tigo TS-4-O Optimizers on all modules within the parallel string design in the array.
Important: Non-Optimizing TS4s ( TS4-F, TS4-2F, TS4-M or TS4-S) cannot compensate for imbalances in production, so it is important that the parallel strings design includes: Mounting all PV-Modules in the same orientation (to the sun) and parallel string lengths are the same (no uneven strings or mismatched PV-Modules).
Here are some important guidelines to follow when designing parallel strings of different lengths:
- Follow the inverter minimum and maximum MPP voltage requirements
- Design strings to be as long as possible (within the MPP voltage requirements)
- Design for shade to fall on the longer of the strings, or evenly across all strings
-
Design the number of longer strings (in parallel) as low as possible
(example: Design for 2 short - 1 long, instead of 1 short - 2 long)
Note: If the system includes Tigo's TS4 DUO products (TS4-R-O-Duo for example), they must be deployed on strings of equal length (only). Do not include uneven strings or mismatched PV-Modules in your design.
How to Calculate Maximum String Mismatch:
To calculate the maximum amount of string-to-string mismatch, use the following equation:
1-(short string/long string) = % mismatch
(must be less than or equal to 25%)
Lastly, remember that the shortest string's voltage must be above the inverter MPP minimum voltage requirements, and the longest string's voltage must be below the inverter's MPP maximum voltage requirements (including the temperature correction for local historical temperatures).
Additional Resources
Designing your TS4 system for different tilts, angles, and orientation
TS4-O Optimizer Placement Guidelines
Mix and Match Different PV Module Types