Can we add Feed-in Tariff into HOMER?

With a little work, you can model that kind of incentive with the current version of HOMER.  You could model a wind turbine, for example, and let HOMER calculate how many MWh/yr it will produce with your wind regime.  Then you could multiply that by the value of the renewable energy certificate to find the annual income that wind turbine would derive from that incentive.  Then you could subtract that from the wind turbine O&M cost to account for the subsidy.

That trick, however, will yield accurate results only if the renewable energy incentive lasts throughout the project lifetime.