Constraint with lagged index

Question

Dear All,In a model, I have a constraint as:y(g,t) - z(g,t) = u(g,t) - u(g,t-1) forall (g,t) All variable are binary variable. g is a set of generator unit and t is a set of time. How to implement this constraint in AIMMS if there a three generator units and the time periods (t) are 1,2, and 3. For the initial condition, generator units #1 and #2 are off-line prior to the first time period indicated by the value of u = 0 while generator unit #3 is online indicated by the value of u = 1. Thank you.

Chris Kuip · Accepted Answer

Hi Rahmat,To refer to the previous period of the first planning period, I usually use a parameter with initial data.So let  iu(g) := data { '#1' : 0, '#2' : 0, '#3' : 1 } ;Then I can use it in a constraint like:  y(g,t) - z(g,t) =  u(g,t) - if t = first( s_TimePeriods ) then iu(g) else u(g,t-1) endifHope this helps.With kind regards,Chris

rahmat · Answer

@Chris KuipThank youfor your very prompt reply. I’ll try this to the model.Thank you.

Constraint with lagged index

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