Add minimum node state constraint

docs/src/mathematical_formulation/constraints.md

@@ -14,6 +14,10 @@
 
 @@add_constraint_node_state_capacity!
 
+### [Minimum node state](@id min_node_state)
+
+@@add_constraint_min_node_state!
+
 ### [Cyclic condition on node state variable](@id constraint_cyclic_node_state)
 
 @@add_constraint_cyclic_node_state!

examples/6_unit_system.json

@@ -82929,7 +82929,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/capacity_planning.json

@@ -3161,7 +3161,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/multi-year_investment_with_econ_params_with_milestones.json

@@ -3150,7 +3150,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/multi-year_investment_with_econ_params_without_milestones.json

@@ -3078,7 +3078,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/multi-year_investment_without_econ_params.json

@@ -3241,7 +3241,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/reserves.json

@@ -1785,7 +1785,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/rolling_horizon.json

@@ -1785,7 +1785,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",
@@ -4809,17 +4816,17 @@
         [
             "node",
             "electricity_node",
-            "node_state_cap",
-            100,
+            "node_availability_factor",
+            1,
             "Base"
         ],
         [
             "node",
             "electricity_node",
-            "node_availability_factor",
-            1,
+            "node_state_cap",
+            100,
             "Base"
-        ],        
+        ],
         [
             "node",
             "electricity_node",

examples/simple_system.json

@@ -1785,7 +1785,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/stochastic.json

@@ -3071,7 +3071,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

examples/unit_commitment.json

@@ -1785,7 +1785,14 @@
             "node_state_min",
             0,
             null,
-            "The minimum permitted value for a `node_state` variable."
+            "The minimum permitted absolute value for a `node_state` variable."
+        ],
+        [
+            "node",
+            "node_state_min_factor",
+            0,
+            null,
+            "The minimum permitted per unit value for a `node_state` variable."
         ],
         [
             "node",

src/SpineOpt.jl

@@ -171,6 +171,7 @@ include("constraints/constraint_max_node_voltage_angle.jl")
 include("constraints/constraint_min_capacity_margin.jl")
 include("constraints/constraint_min_down_time.jl")
 include("constraints/constraint_min_node_pressure.jl")
+include("constraints/constraint_min_node_state.jl")
 include("constraints/constraint_min_node_voltage_angle.jl")
 include("constraints/constraint_min_scheduled_outage_duration.jl")
 include("constraints/constraint_min_up_time.jl")

src/constraints/constraint_min_node_state.jl

@@ -0,0 +1,88 @@
+#############################################################################
+# Copyright (C) 2017 - 2021 Spine project consortium
+# Copyright SpineOpt contributors
+#
+# This file is part of SpineOpt.
+#
+# SpineOpt is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# SpineOpt is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#############################################################################
+
+@doc raw"""
+To ensure a minimum storage content, the $v_{node\_state}$ variable needs be constrained by the following equation:
+
+```math
+v^{node\_state}_{(n, s, t)} \geq \max(p^{node\_state\_cap}_{(n, s, t)} \cdot p^{node\_state\_min\_factor}_{(n, s, t)}, p^{node\_state\_min}_{(n, s, t)}) \quad \forall n \in node : p^{has\_state}_{(n)}, \, \forall (s,t)
+```
+
+Please note that the limit represents the maximum of the two terms.
+The first term is the product of the storage capacity and the minimum factor, which is a per-unit value of the storage capacity.
+The second term is the minimum state, given in absolute values.
+
+See also
+[node\_state\_cap](@ref),
+[node\_state\_min](@ref),
+[node\_state\_min\_factor](@ref),
+[has\_state](@ref).
+"""
+function add_constraint_min_node_state!(m::Model)
+    _add_constraint!(
+        m, :min_node_state, constraint_min_node_state_indices, _build_constraint_min_node_state
+    )
+end
+
+function _build_constraint_min_node_state(m::Model, ng, s_path, t)
+    @fetch node_state, storages_invested_available = m.ext[:spineopt].variables
+    @build_constraint(
+        + sum(
+            + node_state[n, s, t]
+            for (n, s, t) in node_state_indices(m; node=ng, stochastic_scenario=s_path, t=t);
+            init=0,
+        )
+        >=
+        + sum(
+            + node_state_lower_limit(m; node=ng, stochastic_scenario=s, t=t)
+            * (
+                + number_of_storages(m; node=ng, stochastic_scenario=s, t=t, _default=_default_nb_of_storages(n))
+                + sum(
+                    storages_invested_available[n, s, t1]
+                    for (n, s, t1) in storages_invested_available_indices(
+                        m; node=ng, stochastic_scenario=s_path, t=t_in_t(m; t_short=t)
+                    );
+                    init=0,
+                )
+            )
+            for (n, s, t) in node_state_indices(m; node=ng, stochastic_scenario=s_path, t=t);
+            init=0,
+        )
+    )
+end
+
+function constraint_min_node_state_indices(m::Model)
+    (
+        (node=ng, stochastic_path=path, t=t)
+        for (ng, t) in node_time_indices(
+            m; node=intersect(indices(node_state_cap), indices(candidate_storages)), temporal_block=anything
+        )
+        if (has_state(node=ng) && is_longterm_storage(node=ng)) || _is_representative(t)
+        for path in active_stochastic_paths(
+            m,
+            Iterators.flatten(
+                (
+                    node_state_indices(m; node=ng, t=t),
+                    storages_invested_available_indices(m; node=ng, t=t_in_t(m; t_short=t)),
+                )
+            )
+        )
+    )
+end

src/data_structure/preprocess_data_structure.jl

@@ -47,6 +47,7 @@ function preprocess_data_structure()
     generate_unit_flow_capacity()
     generate_connection_flow_capacity()
     generate_node_state_capacity()
+    generate_node_state_lower_limit()
     generate_unit_commitment_parameters()
 end
 
@@ -859,6 +860,22 @@ function generate_node_state_capacity()
     end
 end
 
+function generate_node_state_lower_limit()
+    function _node_state_lower_limit(f; node=node, _default=nothing, kwargs...)
+        maximum([_prod_or_nothing(
+            f(node_state_cap; node=node, _default=_default, kwargs...),
+            f(node_state_min_factor; node=node, kwargs...)),
+            f(node_state_min; node=node, kwargs...)]
+        )
+    end
+
+    node_state_lower_limit = ParameterFunction(_node_state_lower_limit)
+    @eval begin
+        node_state_lower_limit = $node_state_lower_limit
+        export node_state_lower_limit
+    end
+end
+
 _prod_or_nothing(args...) = _prod_or_nothing(collect(args))
 _prod_or_nothing(args::Vector) = any(isnothing.(args)) ? nothing : *(args...)
 _prod_or_nothing(args::Vector{T}) where T<:Call = Call(_prod_or_nothing, args)

src/run_spineopt_basic.jl

@@ -208,6 +208,7 @@ function _add_constraints!(m; log_level=3)
             add_constraint_nodal_balance!,
             add_constraint_node_injection!,
             add_constraint_node_state_capacity!,
+            add_constraint_min_node_state!,
             add_constraint_node_voltage_angle!,
             add_constraint_non_spinning_reserves_lower_bound!,
             add_constraint_non_spinning_reserves_shut_down_upper_bound!,

src/variables/variable_node_state.jl

@@ -35,6 +35,12 @@ function node_state_indices(m::Model; node=anything, stochastic_scenario=anythin
     )
 end
 
+function node_state_lb(m; node, kwargs...)
+    node_state_lower_limit(m; node=node, kwargs..., _default=NaN) * (
+        + number_of_storages(m; node=node, kwargs..., _default=_default_nb_of_storages(node))
+    )
+end
+
 function node_state_ub(m; node, kwargs...)
     node_state_capacity(m; node=node, kwargs..., _default=NaN) * (
         + number_of_storages(m; node=node, kwargs..., _default=_default_nb_of_storages(node))
@@ -52,7 +58,7 @@ function add_variable_node_state!(m::Model)
         m,
         :node_state,
         node_state_indices;
-        lb=node_state_min,
+        lb=node_state_lb,
         ub=node_state_ub,
         fix_value=fix_node_state,
         initial_value=initial_node_state,

templates/spineopt_template.json

@@ -247,7 +247,8 @@
         ["node", "node_slack_penalty", null, null, "A penalty cost for `node_slack_pos` and `node_slack_neg` variables. The slack variables won't be included in the model unless there's a cost defined for them."],
         ["node", "node_state_cap", null, null, "The maximum permitted value for a `node_state` variable."],
         ["node", "node_availability_factor", 1.0, null, "Availability of the `node`, acting as a multiplier on its `node_state_cap`. Typically between 0-1."],
-        ["node", "node_state_min", 0.0, null, "The minimum permitted value for a `node_state` variable."],
+        ["node", "node_state_min", 0.0, null, "The minimum permitted absolute value for a `node_state` variable."],
+        ["node", "node_state_min_factor", 0.0, null, "The minimum permitted per unit value for a `node_state` variable."],        
         ["node", "number_of_storages", 1.0, null, "Denotes the number of 'sub storages' aggregated to form the modelled `node`."],
         ["node", "state_coeff", 1.0, null, "Represents the `commodity` content of a `node_state` variable in respect to the `unit_flow` and `connection_flow` variables. Essentially, acts as a coefficient on the `node_state` variable in the `node_injection` constraint."],
         ["node", "storage_lead_time", {"type": "duration", "data": "0h"}, null, "A storage's lead time, i.e., the time between the moment at which a storage investment decision is takien, and the moment at which the storage investment becomes operational."],