Minor update to variable names (#7)

* Minor update to variable names
* Added fixed `link_opex_fixed`

Author: JulStraus

docs/src/links/capacitycostlink.md

@@ -91,8 +91,8 @@ with paranthesis.
 
 Two additional variables track capacity utilization and associated costs over sub-periods:
 
-- ``\texttt{ccl\_max\_cap\_use}[l, t_{sub}]``: Maximum capacity usage in sub-period ``t_{sub}`` for link ``l``.
-- ``\texttt{ccl\_cap\_cost}[l, t_{sub}]``: Operational cost in sub-period ``t_{sub}`` for link ``l``.
+- ``\texttt{ccl\_cap\_use\_max}[l, t_{sub}]``: Maximum capacity usage in sub-period ``t_{sub}`` for link ``l``.
+- ``\texttt{ccl\_cap\_use\_cost}[l, t_{sub}]``: Operational cost in sub-period ``t_{sub}`` for link ``l``.
 
 ### [Constraints](@id links-CapacityCostLink-math-con)
 
@@ -117,21 +117,21 @@ All additional constraints are created within a new method for the function [`cr
 The capacity utilization constraint tracks the maximum usage within each sub-period:
 
 ```math
-\texttt{link\_in}[l, t, cap\_resource(l)] \leq \texttt{ccl\_max\_cap\_use}[l, t_{sub}]
+\texttt{link\_in}[l, t, cap\_resource(l)] \leq \texttt{ccl\_cap\_use\_max}[l, t_{sub}]
 ```
 
 The capacity cost is calculated as:
 
 ```math
-\texttt{ccl\_cap\_cost}[l, t_{sub}] = \texttt{ccl\_max\_cap\_use}[l, t_{sub}] \times \overline{cap\_price}(l, t_{sub})
+\texttt{ccl\_cap\_use\_cost}[l, t_{sub}] = \texttt{ccl\_cap\_use\_max}[l, t_{sub}] \times \overline{cap\_price}(l, t_{sub})
 ```
 
 where ``\overline{cap\_price}`` is the average capacity price over the sub-period.
 
 Finally, costs are aggregated to each strategic period:
 
 ```math
-\texttt{link\_opex\_var}[l, t_{inv}] = \sum_{t_{sub} \in t_{inv}} \texttt{ccl\_cap\_cost}[l, t_{sub}]
+\texttt{link\_opex\_var}[l, t_{inv}] = \sum_{t_{sub} \in t_{inv}} \texttt{ccl\_cap\_use\_cost}[l, t_{sub}]
 ```
 
 In addition, the energy flow of the constrained resource should not exceed the maximum pipe capacity, which is included through the following constraint:

src/link/model.jl

@@ -2,14 +2,14 @@
     EMB.variables_element(m, ℒˢᵘᵇ::Vector{<:CapacityCostLink}, 𝒯, modeltype::EnergyModel)
 
 Creates the following additional variable for **ALL** capacity cost links:
-- `ccl_max_cap_use[l, t]` is a continuous variable describing the maximum capacity
+- `ccl_cap_use_max[l, t]` is a continuous variable describing the maximum capacity
   usage over sub periods for a [`CapacityCostLink`](@ref) `l` in operational period `t`.
-- `ccl_cap_cost[l, t]` is a continuous variable describing the cost over sub periods
+- `ccl_cap_use_cost[l, t]` is a continuous variable describing the cost over sub periods
   for a [`CapacityCostLink`](@ref) `l` in operational period `t`.
 """
 function EMB.variables_element(m, ℒˢᵘᵇ::Vector{<:CapacityCostLink}, 𝒯, ::EnergyModel)
-    @variable(m, ccl_max_cap_use[ℒˢᵘᵇ, 𝒯] >= 0)
-    @variable(m, ccl_cap_cost[ℒˢᵘᵇ, 𝒯] >= 0)
+    @variable(m, ccl_cap_use_max[ℒˢᵘᵇ, 𝒯] >= 0)
+    @variable(m, ccl_cap_use_cost[ℒˢᵘᵇ, 𝒯] >= 0)
 end
 
 """
@@ -46,20 +46,25 @@ function EMB.create_link(
 
     # Max capacity use constraints
     @constraint(m, [t_sub ∈ 𝒯ˢᵘᵇ, t ∈ t_sub],
-        m[:link_in][l, t, p_cap] .≤ m[:ccl_max_cap_use][l, t_sub]
+        m[:link_in][l, t, p_cap] .≤ m[:ccl_cap_use_max][l, t_sub]
     )
 
     # Capacity cost constraint
     @constraint(m, [t_sub ∈ 𝒯ˢᵘᵇ],
-        m[:ccl_cap_cost][l, t_sub[end]] ==
-        m[:ccl_max_cap_use][l, t_sub[end]] * avg_cap_price(l, t_sub)
+        m[:ccl_cap_use_cost][l, t_sub[end]] ==
+        m[:ccl_cap_use_max][l, t_sub[end]] * avg_cap_price(l, t_sub)
     )
 
     # Sum up costs for each sub_period into the strategic period cost
     @constraint(m, [t_inv ∈ 𝒯ᴵⁿᵛ],
         m[:link_opex_var][l, t_inv] ==
-            sum(m[:ccl_cap_cost][l, t] for t ∈ t_inv)
+            sum(m[:ccl_cap_use_cost][l, t] for t ∈ t_inv)
     )
+
+    # Fix the fixed OPEX to avoid unconstrainted variables
+    for t_inv ∈ 𝒯ᴵⁿᵛ
+        fix(m[:link_opex_fixed][l, t_inv], 0; force = true)
+    end
 end
 
 """

test/link/test_CapacityCostLink.jl

@@ -207,27 +207,27 @@ end
     )
 
     # Max capacity use per sub-period:
-    #    link_in[t] ≤ ccl_max_cap_use[t_sub_end]
+    #    link_in[t] ≤ ccl_cap_use_max[t_sub_end]
     @test all(
         all(
             value(m[:link_in][cc_link, t, power]) ≲
-            value(m[:ccl_max_cap_use][cc_link, t_sub[end]])
+            value(m[:ccl_cap_use_max][cc_link, t_sub[end]])
             for t ∈ t_sub
         )
         for t_sub ∈ 𝒯ˢᵘᵇ
     )
 
     # Capacity cost at end of sub-period: cap_cost == max_cap_use * avg_cap_price
     @test all(
-        value(m[:ccl_cap_cost][cc_link, t_sub[end]]) ≈
-        value(m[:ccl_max_cap_use][cc_link, t_sub[end]]) * EMF.avg_cap_price(cc_link, t_sub)
+        value(m[:ccl_cap_use_cost][cc_link, t_sub[end]]) ≈
+        value(m[:ccl_cap_use_max][cc_link, t_sub[end]]) * EMF.avg_cap_price(cc_link, t_sub)
         for t_sub ∈ 𝒯ˢᵘᵇ
     )
 
-    # Strategic-period sum: link_opex_var == sum(ccl_cap_cost over t_inv)
+    # Strategic-period sum: link_opex_var == sum(ccl_cap_use_cost over t_inv)
     @test all(
         value(m[:link_opex_var][cc_link, t_inv]) ≈
-            sum(value(m[:ccl_cap_cost][cc_link, t]) for t ∈ t_inv)
+            sum(value(m[:ccl_cap_use_cost][cc_link, t]) for t ∈ t_inv)
         for t_inv ∈ 𝒯ᴵⁿᵛ
     )