PVWatts is built and maintained by the National Renewable Energy Labs. The tool can be found here: http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/
PVWatts was created before Smart Modules and optimizers became commercially available, and therefore there is no specific call-out for this technology. The program does allow you to input assumptions on your derate factors in the DC to AC derate dialog box. By entering the following values into the calculator, you can reasonably predict the output an optimized module will give you.