The coupling surface#

The surface every other file in the library is written against. It declares one Port_p per port, one balance per bus, and the relation that says which bus a port sits on. It sets the objective on total_cost, which it reads under given: each component that costs something adds its cost to that sum. Nothing in it names a component class, so it is the one file that does not change when a component class is added.

PyPSA gives each component class a bus column and sums the classes into Bus-nodal_balance. Here a component is wired to a port and the port to a bus, so the balance sums ports and stays as written however many fragments merge. The how-to guide shows the same shape with fewer names.

A flow is positive where the port injects into its bus. Every component reads that convention, and no component restates it.

description: >-
  The coupling surface every component in this library is written against: one
  flow per port, one balance per bus, and one cost to minimise. A component is
  wired to a port, the port to a bus, and the balance names no component class.
  A flow is positive where the port injects into its bus. A component that
  costs something adds its cost to `total_cost`.
dimensions:
  snapshot: { dtype: datetime, description: dispatch periods }
  bus: { dtype: str, description: network nodes }
  port: { dtype: str, description: "the connections components make, one label per connection" }
relations:
  Port_bus: { key: port, values: bus }
variables:
  Port_p:
    dims: [snapshot, port]
    description: what a port puts into its bus in a snapshot, negative for a withdrawal
constraints:
  Bus_nodal_balance:
    description: "`Bus-nodal_balance` — what the ports on a bus put in nets to nothing"
    dims: [snapshot, bus]
    expression: sum(Port_p, by=Port_bus, over=port, into=bus) == 0
given:
  expressions:
    total_cost: { dims: [], description: what running the system costs }
objective:
  sense: minimize
  expression: total_cost

The coupling surface every component in this library is written against: one flow per port, one balance per bus, and one cost to minimise. A component is wired to a port, the port to a bus, and the balance names no component class. A flow is positive where the port injects into its bus. A component that costs something adds its cost to total_cost.

Sets#

Variables#

Given#

Objective#

Subject to#

Bus_nodal_balance

Variable domains#

Port_p