SlackTerminal priorities

[jeandemanged]

• Do you want to request a feature or report a bug? Feature

• What is the current behavior?

  • there can be only one SlackTerminal per VoltageLevel.
  • over a network, all SlackTerminal-s have the same priority

• What is the expected behavior?

  • being able to have multiple SlackTerminal-s per VoltageLevel.
  • SlackTerminal-s can be prioritized (over the entire network, not just within a VoltageLevel), e.g. by specifying an integer value (1: highest priority for selection, 2: second priority, and so on ...)

• What is the motivation / use case for changing the behavior? Example use case: cim:SynchronousMachine.referencePriority (in CGMES import).

  • In the case where there are two generators in on VoltageLevel, gen1 with priority 1, gen2 with priority 2, current CGMES importer will put extension only on gen1. If the user disconnects the generator in priority 1, the other generator with priority 2 cannot be picked up with today's implementation of SlackTerminal.
  • In the case of two VoltageLevel-s, VL1 with gen1 of referencePriority1, VL2 with gen2 of referencePriority2, today it is not possible to represent that gen1 has higher priority than gen2 for slack slelection.

• Please tell us about your environment:

  • PowSyBl Version: 5.0.0
  • OS Version: ...

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, spectrum, etc)

issue raised during discussion on #2402