fix interchange overwrite

src/devices_models/devices/area_interchange.jl

@@ -168,6 +168,7 @@ function add_constraints!(
     },
 ) where {T <: AbstractPTDFModel}
     @assert !isempty(inter_area_branch_map)
+
     time_steps = get_time_steps(container)
     device_names = [PSY.get_name(d) for d in devices]
 
@@ -195,13 +196,16 @@ function add_constraints!(
         inter_change_name = PSY.get_name(area_interchange)
         area_from = PSY.get_from_area(area_interchange)
         area_to = PSY.get_to_area(area_interchange)
+        direction_branch_map = Dict{Float64, Dict{DataType, Vector{<:PSY.ACBranch}}}()
         if haskey(inter_area_branch_map, (area_from, area_to))
-            inter_area_branches = inter_area_branch_map[(area_from, area_to)]
-            mult = 1.0
-        elseif haskey(inter_area_branch_map, (area_to, area_from))
-            inter_area_branches = inter_area_branch_map[(area_to, area_from)]
-            mult = -1.0
-        else
+            # 1 is the multiplier
+            direction_branch_map[1.0] = inter_area_branch_map[(area_from, area_to)]
+        end
+        if haskey(inter_area_branch_map, (area_to, area_from))
+            # -1 is the multiplier because the direction is reversed
+            direction_branch_map[-1.0] = inter_area_branch_map[(area_to, area_from)]
+        end
+        if isempty(direction_branch_map)
             @warn(
                 "There are no branches modeled in Area InterChange $(summary(area_interchange)) \
           LineFlowBoundConstraint not created"
@@ -211,11 +215,13 @@ function add_constraints!(
 
         for t in time_steps
             sum_of_flows = JuMP.AffExpr()
-            for (type, branches) in inter_area_branches
-                flow_vars = get_variable(container, FlowActivePowerVariable(), type)
-                for b in branches
-                    b_name = PSY.get_name(b)
-                    _add_to_jump_expression!(sum_of_flows, flow_vars[b_name, t], mult)
+            for (mult, inter_area_branches) in direction_branch_map
+                for (type, branches) in inter_area_branches
+                    flow_vars = get_variable(container, FlowActivePowerVariable(), type)
+                    for b in branches
+                        b_name = PSY.get_name(b)
+                        _add_to_jump_expression!(sum_of_flows, flow_vars[b_name, t], mult)
+                    end
                 end
             end
             con_ub[inter_change_name, t] =