Hi Ray, Thanks for your advice. I had not considered using new variables and this is a new area for me, so I hope my questions are not too dumb. The process of introducing new variables and constraining them makes sense, as do the additional constraints that you suggest for fp and fn:
fp – fn = p_i(theta) fp >= 0 fn >= 0 However, I am very unsure as to how I can link the new variables to the positive and negative flows. The constraints that you suggested will ensure that the sum of the positive and negative flows will equal the total sum of the flow between two areas. But I do not understand how can I further constrain fp and fn such that fp = sum(positive_flow) and fn = sum(negative_flow) using linear constraints. After looking through some of the existing extensions, I can’t find any examples of constraints or variables being applied based on the sign of other variables and so I am really not sure of how to implement this. Am I overthinking this problem? Any further advice would be very appreciated. Regards, Dominic Von: [email protected] [mailto:[email protected]] Im Auftrag von Ray Zimmerman Gesendet: Montag, 4. Mai 2015 19:24 An: MATPOWER discussion forum Betreff: Re: Adaption of Interface Flow Limits Extension Hi Dominic, Yes, it can be done, but you will need to introduce some new variables, say fp and fn, to represent the positive and negative components of the branch flows. Then you can construct the constraints you want on those variables, rather than directly on the flows themselves (the p_i from (7.6) in the User’s Manual<http://www.pserc.cornell.edu/matpower/docs/MATPOWER-manual-5.1.pdf>) as is done by the current implementation. You will need additional constraints to define these new variables, such as … fp – fn = p_i(theta) fp >= 0 fn >= 0 With zero cost on fp and fn, it’s still possible that both would be positive at the same time for flows where your constraints aren’t binding. It shouldn’t really affect anything, but if it bothers you, you could add a very tiny cost to them. Ray On May 4, 2015, at 11:21 AM, Hewes, Dominic <[email protected]<mailto:[email protected]>> wrote: Dear Matpower Community, The ‚Interface Flow Limits‘ extension allows me to limit the sum of all line flows between two areas to within a set range. However, I want to instead apply two limits – one to the sum of the positive flows, and one to the negative flows. For example, whilst the sum of the flow between area 1 and area 2 can be set as 1200MW using the existing iflims extension, I want to ensure that the flow from area 1 to area 2 = 1400MW and the flow from area 2 to area 1 = 200MW. My question is the following: is it possible using user defined constraints to achieve my aim in matpower? I would need to apply one constraint to the sum of positive flows from area 1 to 2, whilst applying another constraint to the sum of negative flows from area 1 to 2 – but I cannot work out how to write this as a matpower constraint. Any help with this problem would be appreciated. Regards, Dom
