PV-Modules with Tigo's optimizers (MLPE: TS4-A-O) added to them can help to compensate for production losses due to uneven strings and PV-Module Mismatch, as long as the variance (between the parallel strings' output) remains below 25%.
Disclaimer: Tigo Optimization products help to mitigate losses for these scenarios, but no MLPE can compensate for the lack of sunlight or extreme design considerations (i.e., over the stated 25% variance, between parallel strings). For more info on this topic, see: Module Orientation vs. Azimuth: Multiple, Design Considerations
Uneven string management requires Full Deployment of Tigo Optimizer MLPEs. This means, an Optimizer must be included on each and every PV-Module within the parallel string design (Partial Deployment is not an option).
Important: Non-Optimizing MLPEs (like: TS4-F, TS4-2F, TS4-M or TS4-S) do not offer the ability to 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:
- Strictly 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 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 temp-correction for local historic temperatures).