I didn’t realize you were using an OPF. Since you mentioned a slack bus, I assumed you were using a simple power flow. The OPF does not have a concept of slack (only a voltage angle reference).
You could try setting VMIN and VMAX equal to the set-point voltage (the corresponding generator’s VG) for your source and wind gen buses and then completely eliminating the reactive power limits for both source and wind gen and the voltage limits at all other buses by setting the mins to –Inf and the maxes to +Inf. Also, make sure you do not have binding branch flow limits, by setting RATE_A to zero everywhere. If this still doesn’t work, try reducing PMAX of the wind generator until it does. I assume you’ve confirmed that you can solve the case when the wind generator is not producing, correct? -- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 USA phone: (607) 255-9645 > On Mar 23, 2015, at 3:18 PM, angelina sirri <[email protected]> wrote: > > I hadn't thought of limiting the mpc.gen(wind_farm,10) to be equal to > mpc.gen(wind_farm,9). > Previously I had mpc.gen(wind_farm,10)=0 , so when wind output was higher > than the total load, simply results.gen(wind_farm,2) was almost equal to the > total load, and the rest of the wind output was curtailed. > > Now I tried mpc.gen(wind_farm,10)= mpc.gen(wind_farm,9) so in the results, > the slack bus absorbs the remaining wind power , having a negative output. > However the opf does not converge, and I am sure that this is because of > voltage issues. > > I have tried to > - increase Qmin and Qmax limits (both of the wind farm and the slack bus), > -I have tried relaxing the voltage limits (in the mpc.bus(:,12) and > mpc.bus(:,13) > -step down the transformer in the slack bus (by changing the value of > mpc.branch(branch of the transformer 33/11kv, 9)). But still I cannot succeed > convergence. > > What more could I try? > > From: [email protected] <mailto:[email protected]> > Subject: Re: how power can be absorbed by the slack bus > Date: Mon, 23 Mar 2015 12:00:53 -0400 > To: [email protected] <mailto:[email protected]> > > Have you simply tried it? I can’t think of any reason that a negative output > from the slack bus should cause problems. > > Ray > > > On Mar 20, 2015, at 1:32 PM, angelina sirri <[email protected] > <mailto:[email protected]>> wrote: > > Dear all, > > I am trying to simulate active network management in distribution network in > 11kv. I have a distribution network with 40 nodes. Of those, one node is the > distribution substation node, which is also the slack bus, and also I have in > another node a wind farm.The rest of the nodes are loads. > For the cases that I have a low demand and a wind power output higher than > that, I would like to let the wind farm inject that power back to the main > network (which I do not neither include in the mpc. case , nor simulate). > For example, let's say that I have the following: > sum(mpc.bus(:,3))=5MW; %total active demand > sum(mpc.bus(:,4))=4MVar; %total reactive demand > > mpc.gen(slack bus,9)=20MW; %maximum slack bus output > mpc.gen(wind_farm,9)=10MW; %maximum wind power output > > So in this case, the wind farm is able to feed the rest of the network, with > zero power taken from the slack bus (if with opf, wind generator is cheaper > than the slack). > How could I feed the remaining 5MW (10-5) from the wind farm back to the > grid, getting in the results sth like: > results.gen(slack bus,2)=-5MW? > > I guess that I will have voltage issues, but in first place I was wandering > how this could happen in case I do not have voltage issues. Afterwards, to > face the voltage issues I was thinking to manually change the tap of the > transformer behind the slack like that: > > mpc.branch(branch of the transformer 33/11kv, 9) = range between 0 to 1; > > Any proposal would really help!! > Kind Regards, > Angelina
