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perf: skip charge/discharge lock binaries for one-directional batteries #89

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perf: skip charge/discharge lock binaries for one-directional batteries #89

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34 changes: 21 additions & 13 deletions src/optimizer/optimizer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -211,13 +211,19 @@ def _setup_variables(self):
else:
self.variables['z_c'][i] = None

# Binary variable to lock charging against discharging
# Binary variable to lock charging against discharging. A battery
# that cannot discharge (d_max=0) or cannot charge (c_max=0) needs no
# lock: the constraint pair is vacuous, and the binaries only add
# integrality work for the solver.
self.variables['z_cd'] = {}
for i, bat in enumerate(self.batteries):
self.variables['z_cd'][i] = [
pulp.LpVariable(f"z_cd_{i}_{t}", cat='Binary')
for t in self.time_steps
]
if bat.c_max > 0 and bat.d_max > 0:
self.variables['z_cd'][i] = [
pulp.LpVariable(f"z_cd_{i}_{t}", cat='Binary')
for t in self.time_steps
]
else:
self.variables['z_cd'][i] = None

def _setup_target_function(self):
"""
Expand Down Expand Up @@ -504,14 +510,16 @@ def _add_battery_constraints(self):
self.problem += (self.variables['d'][i][t] <= bat.d_max * self.time_series.dt[t] / 3600.
* (1 - self.variables['y'][t]))

# lock charging against discharging
for t in self.time_steps:
# Discharge constraint
self.problem += (self.variables['d'][i][t] <= bat.d_max * self.time_series.dt[t] / 3600.
* self.variables['z_cd'][i][t])
# Charge constraint
self.problem += (self.variables['c'][i][t] <= bat.c_max * self.time_series.dt[t] / 3600.
* (1 - self.variables['z_cd'][i][t]))
# lock charging against discharging (skipped when the battery
# cannot both charge and discharge: nothing to lock)
if self.variables['z_cd'][i] is not None:
for t in self.time_steps:
# Discharge constraint
self.problem += (self.variables['d'][i][t] <= bat.d_max * self.time_series.dt[t] / 3600.
* self.variables['z_cd'][i][t])
# Charge constraint
self.problem += (self.variables['c'][i][t] <= bat.c_max * self.time_series.dt[t] / 3600.
* (1 - self.variables['z_cd'][i][t]))

def solve(self) -> Dict:
"""
Expand Down
2 changes: 1 addition & 1 deletion test_cases/013-grid-export-limit-hit.json
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Original file line number Diff line number Diff line change
Expand Up @@ -199,7 +199,7 @@
},
"expected_response": {
"status": "Optimal",
"objective_value": 17.5372629588039,
"objective_value": 17.531374666979104,
"limit_violations": {
"grid_import_limit_exceeded": false,
"grid_export_limit_hit": true
Expand Down