Why need bus

[edxu96]

The bus’s role is to enforce energy conservation for all elements feeding in and out of it (i.e. like Kirchhoff’s Current Law).

• https://pypsa.readthedocs.io/en/latest/design.html#buses-are-the-fundamental-nodes

[edxu96]

Several software packages and books refer to “PV bus”, “slack bus” or “PQ bus”. These expressions mix together two different concept: (i) the concept of bus, which provides a topological information and (ii) the concept of generators or loads, which are devices connected to a bus. Actually, there is no real matter in connecting a PQ load and a PV generator at the same bus. Thus, strictly speaking, expressions as “PV bus” or “PQ bus” are misleading and should be avoided. [milano2010power]