eyeprolog

Microgrid dispatch

How should a campus cover its load with renewables, a battery, and the grid?

A campus microgrid needs 620 kW. Solar and wind cover part of it; the battery can cover more, but must keep a reserve; the grid covers the rest, up to a contract limit. EyeProlog computes the dispatch and states whether every constraint holds.

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The question

The dispatch policy is simple and auditable:

use renewables first;
discharge the battery, but never below its required reserve;
import whatever is still missing from the grid.

Is the resulting plan stable, meaning within the grid contract and with the reserve intact?

The facts

load_kW(campus_interval_17, 620.0).
solar_kW(campus_interval_17, 180.0).
wind_kW(campus_interval_17, 90.0).
battery_max_discharge_kW(campus_interval_17, 320.0).
required_battery_reserve_kW(campus_interval_17, 80.0).
grid_contract_limit_kW(campus_interval_17, 150.0).

One 15-minute-style planning interval with all quantities in kilowatts.

The rules

battery_dispatch_kW(Site, Dispatch) :-
  net_deficit_kW(Site, Deficit),
  reserve_aware_battery_limit_kW(Site, Limit),
  (Deficit =< Limit -> Dispatch = Deficit ; Dispatch = Limit).

grid_import_kW(Site, Import) :-
  net_deficit_kW(Site, Deficit),
  battery_dispatch_kW(Site, Dispatch),
  (Import is Deficit - Dispatch).

stable_dispatch(Site) :-
  contract_ok(Site),
  reserve_ok(Site).

The battery covers the deficit up to its reserve-aware limit; the grid imports the rest. The plan is stable only if both the contract and the reserve checks pass.

The answer

eyeprolog examples/microgrid-dispatch.pl

renewablePower_kW(campus_interval_17, 270.0).
batteryDispatch_kW(campus_interval_17, 240.0).
gridImport_kW(campus_interval_17, 110.0).
reserveAfterDispatch_kW(campus_interval_17, 80.0).
status(campus_interval_17, stable_dispatch).
reason(campus_interval_17, "battery dispatch covers the deficit while preserving reserve and grid contract limits").

Renewables give 270 kW, leaving a 350 kW deficit. The battery supplies 240 kW (its 320 kW maximum minus the 80 kW reserve), and the grid imports the remaining 110 kW, under the 150 kW contract.

The reason

step(battery_dispatch_kW(campus_interval_17, 240.0),
     rule(11),
     ['Site' = campus_interval_17, 'Dispatch' = 240.0, 'Deficit' = 350.0, 'Limit' = 240.0],
     [net_deficit_kW(campus_interval_17, 350.0),
      reserve_aware_battery_limit_kW(campus_interval_17, 240.0),
      (350.0 =< 240.0 -> 240.0 = 350.0 ; 240.0 = 240.0)]).
step(contract_ok(campus_interval_17),
     rule(14),
     ['Site' = campus_interval_17, 'Import' = 110.0, 'Limit' = 150.0],
     [grid_import_kW(campus_interval_17, 110.0),
      grid_contract_limit_kW(campus_interval_17, 150.0),
      110.0 =< 150.0]).

The deficit (350) exceeds the battery limit (240), so the if-then-else takes the limit. The grid import of 110 kW is then within the 150 kW contract.

The check

condition('C1', resolution, ok, 21).
condition('C5', re_decision, ok, 10).
steps(31).
verified(21).
recomputed(9).
composed(1).
trusted(0).
verdict(checked).

Every rule step replays and every arithmetic step is recomputed. The one if-then-else decision is recorded as the branch it took, including the failed test \+ 350.0 =< 240.0, which the checker decides again too. The plan’s feasibility is fully checked.

Try it

Raise the load to 700 kW. Which constraint fails first, and what happens to status/2?
Add a rule that reports why a dispatch is unstable, naming the failed constraint.
Lower required_battery_reserve_kW to 0. Is the plan more robust or less, and does the model say so?

Learn more in The Art of EyeProlog, Chapter 14.

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