Changed the default number of units based on is_candidate. (#1036)

docs/src/concept_reference/number_of_units.md

@@ -1,3 +1,3 @@
 Defines how many members a certain [unit](@ref) object represents. Typically this parameter takes a binary (UC) or integer (clustered UC) value. Together with the [unit\_availability\_factor](@ref) and [units\_unavailable](@ref), this will determine the maximum number of members that can be online at any given time. (Thus restricting the [units\_on](@ref) variable). It is possible to allow the model to increase the `number_of_units` itself, through [Investment Optimization](@ref). It is also possible to schedule maintenance outages using [outage\_variable\_type](@ref) and [scheduled\_outage\_duration](@ref).
 
-The default value for this parameter is 1.
+The default value for this parameter is 1. The default value is 0 when [candidate\_units](@ref) has been defined for the unit in question.

src/constraints/constraint_units_available.jl

@@ -53,7 +53,10 @@ function _build_constraint_units_available(m, u, s, t)
             init=0,
         )
         <=
-        + number_of_units(m; unit=u, stochastic_scenario=s, t=t)
+        # Change the default number of units so that it is zero when candidate units are present
+        # and otherwise 1.
+        + ifelse(is_candidate(unit=u), number_of_units(m; unit=u, stochastic_scenario=s, t=t, _default=0), 
+            number_of_units(m; unit=u, stochastic_scenario=s, t=t) )
         - units_unavailable(m; unit=u, stochastic_scenario=s, t=t)
     )
 end

templates/spineopt_template.json

@@ -289,7 +289,7 @@
         ["unit", "is_renewable", false, "boolean_value_list", "Whether the unit is renewable - used in the minimum renewable generation constraint within the Benders master problem"],
         ["unit", "min_down_time", null, null, "Minimum downtime of a `unit` after it shuts down."],
         ["unit", "min_up_time", null, null, "Minimum uptime of a `unit` after it starts up."],
-        ["unit", "number_of_units", 1.0, null, "Denotes the number of 'sub units' aggregated to form the modelled `unit`."],
+        ["unit", "number_of_units", 1.0, null, "Denotes the number of 'sub units' aggregated to form the modelled `unit`. The default value becomes zero if `candidate_units` has been defined."],
         ["unit", "online_variable_type", "unit_online_variable_type_linear", "unit_online_variable_type_list", "A selector for how the `units_on` variable is represented within the model."],
         ["unit", "outage_variable_type", "unit_online_variable_type_none", "unit_online_variable_type_list", "Determines whether the outage variable is integer or continuous or none(no optimisation of maintenance outages)."],
         ["unit", "scheduled_outage_duration", null, null, "Specifies the amount of time a unit must be out of service for maintenance as a single block over the course of the optimisation window"],

test/constraints/constraint_unit.jl

@@ -155,11 +155,12 @@ function test_constraint_units_available()
         end
     end
 end
+
 function test_constraint_units_available_units_unavailable()
     @testset "constraint_units_available_units_unavailable" begin
         url_in = _test_constraint_unit_setup()
         number_of_units = 4
-        candidate_units = 3
+        candidate_units = 3 
         units_unavailable = 1
         unit_availability_factor = 0.5
         object_parameter_values = [
@@ -191,6 +192,40 @@ function test_constraint_units_available_units_unavailable()
             @test _is_constraint_equal(observed_con, expected_con)
         end
     end
+    @testset "constraint_units_available_units_unavailable_default" begin
+        url_in = _test_constraint_unit_setup()
+        candidate_units = 3
+        number_of_units_when_candidates_units = 0 
+        units_unavailable = 1
+        unit_availability_factor = 0.5
+        object_parameter_values = [
+            ["unit", "unit_ab", "candidate_units", candidate_units],
+            ["unit", "unit_ab", "units_unavailable", units_unavailable],
+            ["unit", "unit_ab", "unit_availability_factor", unit_availability_factor],
+        ]
+        relationships = [
+            ["unit__investment_temporal_block", ["unit_ab", "hourly"]],
+            ["unit__investment_stochastic_structure", ["unit_ab", "stochastic"]],
+        ]
+        SpineInterface.import_data(url_in; relationships=relationships, object_parameter_values=object_parameter_values)
+        m = run_spineopt(url_in; log_level=0, optimize=false)
+        var_units_on = m.ext[:spineopt].variables[:units_on]
+        var_units_invested_available = m.ext[:spineopt].variables[:units_invested_available]
+        constraint = m.ext[:spineopt].constraints[:units_available]
+        @test length(constraint) == 2
+        scenarios = (stochastic_scenario(:parent), stochastic_scenario(:child))
+        time_slices = time_slice(m; temporal_block=temporal_block(:hourly))
+        @testset for (s, t) in zip(scenarios, time_slices)
+            key = (unit(:unit_ab), s, t)
+            var_u_on = var_units_on[key...]
+            var_u_inv_av = var_units_invested_available[key...]
+            expected_con = @build_constraint(var_u_on <= number_of_units_when_candidates_units + var_u_inv_av - units_unavailable)
+            con_key = (unit(:unit_ab), s, t)
+            con = constraint[con_key...]
+            observed_con = constraint_object(con)
+            @test _is_constraint_equal(observed_con, expected_con)
+        end
+    end
 end
 
 function test_constraint_unit_state_transition()