Area interchange

Area-interchange control adjusts each area's net interchange to match its schedule. Its accounting determines which flows and loads contribute to that interchange.

Scope

Area-interchange control is disabled by default and is enabled through the area_interchange solve option: 1 accounts tie-line flows only, and 2 accounts tie-line flows and loads. When enabled, it drives each area's net interchange to the schedule in the area records.

Accounting

The net interchange of an area is the sum of the flows leaving it on tie branches, each read at the branch's metered end (MET); tie losses therefore fall outside the metered reading rather than being split between areas. A DC link crossing an area boundary contributes the sending converter's power. In mode 2, a load whose declared area differs from the area of its bus is additionally attributed to the declaring area: its power counts toward the declaring area's interchange and against the hosting area's.

Adjustment

Each area names a slack machine bus (ISW). The active power of that machine is redispatched until the area's net interchange reaches PDES within the tolerance PTOL, both in MW. The result reports an area that cannot be adjusted from its declared slack machine. Area schedules must be jointly consistent with the system power balance.

Attainability

When a target is tighter than the solution can resolve, the closest attainable interchange is reported and the control stops adjusting.