FIX: monotonic constraint for traditional formulations

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## staged
 
+- Fixed monotonic constraint for traditional formulations
 - Added function keyword argument `check_enabled` to `build_nested_graph` to control `calc_connected_components`
 - Added option `disable-grid-forming-constraint-block-cuts` to disable block-cut constraints in grid-forming inverter constraints
 - Added support for PowerModelsDistribution v0.15

src/core/constraint.jl

@@ -1188,3 +1188,19 @@ function constraint_energized_blocks_strictly_increasing(pm::AbstractUnbalancedP
         JuMP.@constraint(pm.model, z_block_n2 >= z_block_n1)
     end
 end
+
+
+"""
+    constraint_energized_loads_strictly_increasing(pm::AbstractUnbalancedPowerModel, n_1::Int, n_2::Int)
+
+Constraint to ensure that the number of energized load blocks from one timestep to another is strictly increasing
+and that once energized, a load block cannot be shed in a later timestep.
+"""
+function constraint_energized_loads_strictly_increasing(pm::AbstractUnbalancedPowerModel, n_1::Int, n_2::Int)
+    for load_id in ids(pm, n_2, :load)
+        z_demand_n1 = var(pm, n_1, :z_demand, load_id)
+        z_demand_n2 = var(pm, n_2, :z_demand, load_id)
+
+        JuMP.@constraint(pm.model, z_demand_n2 >= z_demand_n1)
+    end
+end

src/prob/mld_traditional.jl

@@ -133,7 +133,7 @@ function build_mn_traditional_mld(pm::PMD.AbstractUBFModels)
         end
 
         if ref(pm, n_1, :options, "constraints")["enable-strictly-increasing-restoration-constraint"]
-            constraint_energized_blocks_strictly_increasing(pm, n_1, n_2)
+            constraint_energized_loads_strictly_increasing(pm, n_1, n_2)
         end
 
         n_1 = n_2
@@ -258,7 +258,7 @@ function build_mn_traditional_mld(pm::PMD.AbstractUnbalancedPowerModel)
         end
 
         if ref(pm, n_1, :options, "constraints")["enable-strictly-increasing-restoration-constraint"]
-            constraint_energized_blocks_strictly_increasing(pm, n_1, n_2)
+            constraint_energized_loads_strictly_increasing(pm, n_1, n_2)
         end
 
         n_1 = n_2