Hi, I am using MatPower during my MSc thesis in which I study the behaviour of a storage system connected to a distribution network with distributed generators (DGs). My objective is to maximise the DG export subject to the grid's constraints (voltages, line limits) - objective function: max Pdg. I though that putting the costs of the main grid's generator (slack bus) equal to zero, and the DGs' costs a negative value I would get the maximum DG output. However, it seems that this is not the case since I get a different DG export for different negative costs. If I was right, then the DG export (maximum achieved subject to system constraints) should be the same for every negative cost.
Do you think that my thinking is wrong? What would you suggest me to do in order to maximise the DG export. I read section 5.3 but I think that I do not have to add more variables and costs, since I can model DG units as plain generators. Thank you in advance, Dionisis
