A question about User Constraint

[Lee]

Sorry to bother again.
I just start to learn how to use Process set and Commodity set. And is demo11, it creat a Process set called PP_RENNEW. Then it was used to specifies a minimum renewable penetration share.
I saw the value is negative and Iwant to know why. If I change it to postive, the constraint will be invalid?

[Antti-L]

> I saw the value is negative and I want to know why.

It is due to basic algebra. The default form of inequality constraints is such that the terms referring to variables are all on the LHS (Left-Hand-Side). So, if your constraint is something like:

  SUM({p ∈ PP_RENEW }, 1×VAR_FLO(REG1,2050,p,ELC))  ≥  0.2×VAR_COMPRD(REG1,2050,ELC)

In the standard form the it will thus be:

  SUM({p ∈ PP_RENEW }, 1×VAR_FLO(REG1,2050,p,ELC)) − 0.2×VAR_COMPRD(REG1,2050,ELC) ≥  0

As you can see, the sign of the term referring to VAR_COMPRD has been changed due to moving it onto the LHS. And because of that, the UC_COMPRD coefficient must be −0.2 when using this default arrangement. The negative per cent values in your screenshot are defining exactly those UC_COMPRD values on the LHS. Alternatively, one can also explicitly tell the model generator, which terms are supposed to be on the LHS and which are on the RHS, but that's more like an advanced option.

[Lee]

> I saw the value is negative and I want to know why.

It is due to basic algebra. The default form of inequality constraints is such that the terms referring to variables are all on the LHS (Left-Hand-Side). So, if your constraint is something like:

  SUM({p ∈ PP_RENEW }, 1×VAR_FLO(REG1,2050,p,ELC))  ≥  0.2×VAR_COMPRD(REG1,2050,ELC)

In the standard form the it will thus be:

  SUM({p ∈ PP_RENEW }, 1×VAR_FLO(REG1,2050,p,ELC)) − 0.2×VAR_COMPRD(REG1,2050,ELC) ≥  0

As you can see, the sign of the term referring to VAR_COMPRD has been changed due to moving it onto the LHS. And because of that, the UC_COMPRD coefficient must be −0.2 when using this default arrangement. The negative per cent values in your screenshot are defining exactly those UC_COMPRD values on the LHS. Alternatively, one can also explicitly tell the model generator, which terms are supposed to be on the LHS and which are on the RHS, but that's more like an advanced option.

Thank you Antti! You help me a lot!