Yes, I am using dispatchable loads and as far as the costs, grid infeed is of free cost, distributed generation is more expensive and the energy not supplied generators are of the highest cost. When there is energy not supplied the voltage in that nodes reaches the maximum upper limit (1.06) . When I change the voltage limit, the dispatch is again the same and the problematic nodes reach the new maximum upper limit. I think that the problem is the initial voltage of the gens in mpc.gen(:,6). What values should I put? The system originally had only load buses( with voltage less than 1 ). Now that I have transformed those buses to gen buses I should predetermined the voltages of the gens. I tried to put the same voltage as the mpc.bus (:, 8). But these values seem to be not so accurate in the end. How should I evaluate what values to put in the mpc.gen(:,6)?
From: [email protected] Subject: Re: reluctant energy not supplied in a distribution system with opf Date: Tue, 11 Feb 2014 11:14:31 -0500 To: [email protected] I also suspect it is a reactive power or voltage problem. Is there a voltage limit binding at the buses where energy is not supplied (I assume you are using dispatchable loads)? If so, you might get some insight from doing some perturbation analysis. Simply change that voltage limit by a very small amount and see how the dispatch changes. My guess is that the only way to maintain the voltage is by using the expensive distributed generators. Shifting generation to the grid infeed would likely result in more load shedding to keep voltages in line. Presumably load shedding is even more costly than the distributed generation?Kind Regards,Angelina -- Ray ZimmermanSenior Research AssociateB30 Warren Hall, Cornell University, Ithaca, NY 14853phone: (607) 255-9645 On Feb 11, 2014, at 5:48 AM, angelina sirri <[email protected]> wrote:Dear Dr Zimmerman,I am using an 11kV distribution system, which is consisted of two radial circuits connected by a normally open point. The network has one grid infeed (Vg=1) whereas all the other nodes where occupied only by loads (with Vm<1). Now I increase the loading of the circuits and have added distributed generators in all the load buses, which will only operate in case there is a line fault in the system(otherwise there is no need for them to operate because the grid infeed can give really high power, comparing to the load and the lines rating is also really big) . For the voltage problems, I have added reactive power in each node. The thing that confuses me is , that when there is a line fault (the worst case scenario line loss), there is always energy not supplied , although a path from the main supply exists and also the rating of the lines allows that power to pass through the line. This happens mainly for the most distant nodes. In that case, all the available distributed generators generate at their Pmax , but the grid infeed value is really small. Why the opf prefers to use the really expensive generators of the distant nodes (used for the energy not supplied) instead of absorbing that power from the free of cost grid infeed? I can guess that is a reactive problem or a voltage problem but I cannot find a suitable solution. Any help would be of high importance,King Regards,Angelina
