direct load control

[Mounika Vanjarapu]

sir
   In the direct load control we provide incentives for the curtailed
load.here we set a virtual generator in order to include the incentives in
the objective function.But the virtual generator cost is (marginal
benefit-incentives).
 for example  i take the marginal benefit=38,incentive=20,the curtailed
load is 13.5MW.then the virtual generator cost is 18.now the objective
function includes
13.5*18 but not 13.5*20 which is my incentive.
         how my incentive will include.