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UnitCommitment.jl/src/model/formulations/base/storage.jl

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Julia

# UnitCommitment.jl: Optimization Package for Security-Constrained Unit Commitment
# Copyright (C) 2020, UChicago Argonne, LLC. All rights reserved.
# Released under the modified BSD license. See COPYING.md for more details.
function _add_storage_unit!(
model::JuMP.Model,
su::StorageUnit,
sc::UnitCommitmentScenario,
)::Nothing
# Initialize variables
storage_level = _init(model, :storage_level)
charge_rate = _init(model, :charge_rate)
discharge_rate = _init(model, :discharge_rate)
is_charging = _init(model, :is_charging)
is_discharging = _init(model, :is_discharging)
eq_min_charge_rate = _init(model, :eq_min_charge_rate)
eq_max_charge_rate = _init(model, :eq_max_charge_rate)
eq_min_discharge_rate = _init(model, :eq_min_discharge_rate)
eq_max_discharge_rate = _init(model, :eq_max_discharge_rate)
# Initialize constraints
net_injection = _init(model, :expr_net_injection)
eq_storage_transition = _init(model, :eq_storage_transition)
eq_ending_level = _init(model, :eq_ending_level)
# time in hours
time_step = sc.time_step / 60
for t in 1:model[:instance].time
# Decision variable
storage_level[sc.name, su.name, t] = @variable(
model,
lower_bound = su.min_level[t],
upper_bound = su.max_level[t]
)
charge_rate[sc.name, su.name, t] = @variable(model)
discharge_rate[sc.name, su.name, t] = @variable(model)
is_charging[sc.name, su.name, t] = @variable(model, binary = true)
is_discharging[sc.name, su.name, t] = @variable(model, binary = true)
# Objective function terms
add_to_expression!(
model[:obj],
charge_rate[sc.name, su.name, t],
su.charge_cost[t] * sc.probability,
)
add_to_expression!(
model[:obj],
discharge_rate[sc.name, su.name, t],
su.discharge_cost[t] * sc.probability,
)
# Net injection
add_to_expression!(
net_injection[sc.name, su.bus.name, t],
discharge_rate[sc.name, su.name, t],
1.0,
)
add_to_expression!(
net_injection[sc.name, su.bus.name, t],
charge_rate[sc.name, su.name, t],
-1.0,
)
# Simultaneous charging and discharging
if !su.simultaneous_charge_and_discharge[t]
# Initialize the model dictionary
eq_simultaneous_charge_and_discharge =
_init(model, :eq_simultaneous_charge_and_discharge)
# Constraints
eq_simultaneous_charge_and_discharge[sc.name, su.name, t] =
@constraint(
model,
is_charging[sc.name, su.name, t] +
is_discharging[sc.name, su.name, t] <= 1.0
)
end
# Charge and discharge constraints
eq_min_charge_rate[sc.name, su.name, t] = @constraint(
model,
charge_rate[sc.name, su.name, t] >=
is_charging[sc.name, su.name, t] * su.min_charge_rate[t]
)
eq_max_charge_rate[sc.name, su.name, t] = @constraint(
model,
charge_rate[sc.name, su.name, t] <=
is_charging[sc.name, su.name, t] * su.max_charge_rate[t]
)
eq_min_discharge_rate[sc.name, su.name, t] = @constraint(
model,
discharge_rate[sc.name, su.name, t] >=
is_discharging[sc.name, su.name, t] * su.min_discharge_rate[t]
)
eq_max_discharge_rate[sc.name, su.name, t] = @constraint(
model,
discharge_rate[sc.name, su.name, t] <=
is_discharging[sc.name, su.name, t] * su.max_discharge_rate[t]
)
# Storage energy transition constraint
prev_storage_level =
t == 1 ? su.initial_level : storage_level[sc.name, su.name, t-1]
eq_storage_transition[sc.name, su.name, t] = @constraint(
model,
storage_level[sc.name, su.name, t] ==
(1 - su.loss_factor[t]) * prev_storage_level +
charge_rate[sc.name, su.name, t] *
time_step *
su.charge_efficiency[t] -
discharge_rate[sc.name, su.name, t] * time_step /
su.discharge_efficiency[t]
)
# Storage ending level constraint
if t == sc.time
eq_ending_level[sc.name, su.name] = @constraint(
model,
su.min_ending_level <=
storage_level[sc.name, su.name, t] <=
su.max_ending_level
)
end
end
return
end