How to change the MPPT configuration in RatedPower?

The MPPT configuration options are only available when an E-W structure is selected. You would need to choose this structure first, and then go back to “Equipment > Inverter > MPPT configuration” and select the preferred configuration. 
If you’re using a tracker or a fixed structure, this option won’t be available. The reason is because our energy model will consider a flat terrain and homogeneous irradiance, meaning that no difference will be computed in terms of energy in each of the different MPPT levels of that inverter (it would be like using an inverter with only one MPPT). However, the software does consider the parameters with regards to voltage and temperature to calculate the MPPT window. If you would like to size a specific number of strings/inverter, then we recommend checking this article.