Dear Dr Zimmerman,
My optimization problem determines generation capacity and location based on the results from Matpower power flow(by calling a function). After iterations are stopped, I looked at the slack bus branch values in Command Window and saw that I have 122.54 from bus 1 to 2 (due to 189.98 MW generations in slack bus) which is a violation for the branch. Now I also have the results from my optimization giving bus 19 and 8 as the optimal places. To my dismay if I add two DGs (got from the last step ) into the locations and I run PF again I don’t see this violation! Example: my results says optimal capacity for bus 19 and 8 are 32 and 47 MW,I changed the mpc.gen and got -40.97 from the bus 1 to 2 and -53.33 for the slack bus generation (No Violation anymore!!) *Do you thing that there might be a problem with my code? Or does that make sense?* On Wed, Jan 18, 2012 at 3:27 PM, Ray Zimmerman <[email protected]> wrote: > Iman, > > If I understand correctly, your optimization program gives you a dispatch > that is optimal in some sense but results in violated thermal limits and > you want to redispatch the generation to respect the thermal limits. > Correct? > > If so, what criteria do you propose to use to determine this redispatch? > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > On Jan 18, 2012, at 9:13 AM, iman wrote: > > *Dear Dr Zimmerman, Shiyang, Li and Arash* > > > Thank you for your reply to my problem. Dr Zimmerman has said that I need > to use OPF *instead of PF* for branch thermal constraints. The problem is > that I am using another optimization method connected to Matpower and this > optimization program only needs to use V,P,Q and delta values from the > power flow calculations. In my optimization program, I am trying to > minimize P loss and other things so if I use OPF, my final results would be > affected and they are not purely from my optimization method. > > I also tried to code the thermal limit for PF myself but I haven’t been > able to. > > *Would you please help me in coding the thermal constraints?* > > > Regards > > Iman > > > 2012/1/13 新浪VIP <[email protected]> > >> Hi Iman， >> 1, Even your object is to study the system near static limit, keeping all >> generation of PV buses is usually not reasonable, because this scenario may >> never occur. For this sake, when we calculate load margin for example, we >> normally increase P generation with loads. >> >> 2, Power is always conserved on static state. Without PV generation >> increasing >> , the slack bus has to compensate all the deficit, 236.55 MW here. >> >> 3, Like what Dr Ray said, if you want to involve thermal limits of >> branches, you may either use OPF solver, or code you own function to adjust >> PV generations. >> >> Shiyang Li >> >> 发自我的 iPhone >> >> 在 2012-1-12，21:44，iman <[email protected]> 写道： >> >> Dear Shiyang, Li >> >> Thanks for taking time answering. >> >> I didn’t increase any generations in the PV buses because my objective >> for increasing the load is pushing the system to the instability margin >> (like voltage drop in buses). >> >> I agree with you that network loss doesn’t seem a real number as well as >> other numbers. >> >> In the case30.m (base case) after running pf I have: >> >> *Total generation capacity =335 MW* >> >> *On-line capacity =335 MW* >> >> *Continued Gens (actual generation)=191.6 MW* >> >> *Load = 189.2 MW* >> >> *Losses=2.44 MW* >> >> * * >> >> *Branch 1-2 =10.89 MW* >> >> *Branch 1-3=15.08 MW* >> >> ****Now I multiply Pd (demanded power)by 2 to make the whole consumption >> twice, I have*** >> >> *Total generation capacity =815 MW* >> >> *On-line capacity =815 MW* >> >> *Continued Gens (actual generation)=402.2 MW* >> >> *Load = 378 MW* >> >> *Losses=23.82 MW* >> >> * * >> >> *Branch 1-2 =154.81 MW* >> >> *Branch 1-3=81.08 MW* >> >> * * >> >> * * >> >> Having said the above in brief: >> >> 1-In Bus 1 (Slack) we have 236.55 MW injection power .Where does this >> added amount come from? >> >> 2-What if I want to fix branch 1-2 limit to 100 MW (or 100 MVA)? What >> should I do? >> >> >> Thank you for your attention and time >> >> Wish you the best. >> >> Iman >> >> >> On Wed, Jan 11, 2012 at 7:45 PM, 李诗旸 <[email protected]> wrote: >> >>> Dear Iman,**** >>> >>> With the load increasing, have you increase the generation from PV >>> buses? I don’t think the network loss could usually increase to nearly 10 >>> times even at static limit. You may double the Pg on PV buses with the >>> load. Then, if you still want to impose the branch thermal limits, you have >>> to code the function to adjust the Pg for PV buses based on participant >>> factors (branch flow sensitivity w.r.t. generation) or others.**** >>> >>> ** ** >>> >>> Shiyang, Li**** >>> >>> ** ** >>> >>> ** ** >>> >>> *发件人:* [email protected] [mailto: >>> [email protected]] *代表 *iman >>> *发送时间:* 2012年1月12日 0:57 >>> *收件人:* [email protected] >>> *主题:* limits on the branches**** >>> >>> ** ** >>> >>> Dear all,**** >>> >>> ** ** >>> >>> I want to use power flow (PF) for the load increase studies. I picked 30 >>> bus system with Pg=23.54 MW for the slack bus. Running the power flow with >>> the base loads ,I get 25.97 MW which is quite close to 23.54.**** >>> >>> Now I want to increase all of the loads 2 times. Running pf I get 236.55 >>> MW for the slack bus .**** >>> >>> I think in practice thermal line limits doesn’t allow this amount of >>> power dragging from slack bus.**** >>> >>> I want to make my problem practical by imposing thermal limits on the >>> branches .How can I do that?**** >>> >>> ** ** >>> >>> Thank you in advance for your patience **** >>> >>> I look forward to hear from you guys**** >>> >>> Iman**** >>> >> >> >> >> -- >> Best regards >> Iman >> >> > > > -- > Best regards > Iman > > > -- Best regards Iman
