Difference in a sum

GAMSPy
1

Here’s an improved version of your message with clearer details about the error and your model setup:

Hello,

I’m working on a GAMS model where I have a variable L representing the battery’s level of charge in MWh over time periods t. One of my constraints involves limiting the change in charge level between consecutive time periods.

Here’s the formula I’m trying to use:

pow[t] = (L[t+1] - L[t]) <= C

However, I encounter this error:

TypeError: Domain item must be type Set, Alias, ImplicitSet or str but found <class 'gamspy._algebra.expression.Expression'>

It seems the error arises because of L[t+1].

How can I reference the next value of L (i.e., L[t+1]) within the same constraint, so I can calculate the difference with L[t]?

2

Hi Paul,

The operation you are referring to called the “lead” operation. Here is how you can write it correctly:

pow[t] = (L[t.lead(1)] - L[t]) <= C

See Lead and Lag Operation for more details.

Muhammet

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