Iman Like what Dr. Zimmerman said, you should first establish your criteria for dispatch adjusting then consider how to achieve. I suggest you may look up some books, usually about security analysis, to find out those ready-made methods for redispatch, then code your own depending on your aim. Actually there has been much valuable work on it.
Shiyang Li 发件人: [email protected] [mailto:[email protected]] 代表 iman 发送时间: 2012年1月18日 22:13 收件人: MATPOWER discussion forum 主题: Re: 答复: limits on the branches 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
