Dual MPPT

When you model a PV system with more than one subarray, SAM assumes that each subarray in the system operates at its maximum power point.

When subarrays have different maximum power voltages (Vmp) because of their different orientations, SAM estimates the inverter input voltage by either averaging the subarray Vmp values, or using a more sophisticated algorithm if you check the box under "PV Subarray Voltage Mismatch" on the System Design input page.

We do hope to add support for both multiple MPPT inputs to an inverter, and for multiple inverter types in one system in a future version of SAM.

Best regards,
Paul.

Dear Jen,

If all of the modules are in the same orientation, and the module string length for each MPPT input on the inverter is the same, then SAM's single MPPT input model will work fine to represent an inverter with multiple MPPT inputs.

When you model the array using multiple subarrays, you can assign different tilt and azimuth angles to each subarray (or combine subarrays with fixed arrays and trackers). The only limitation is that SAM requires all subarrays to have the same number of modules per string (and type of module), and models the inverter as if all subarrays were connected to a single inverter. In that case, SAM estimates the effect of voltage mismatch between the subarrays.

You are correct that SAM models shading of the array by nearby objects as a reduction of the beam irradiance incident on the array.

Best regards,
Paul.