Selection of slack generator from CIM/CGMES data
If no external grid injection exists, one generator is required to be selected as slack generator for power flow calculation. This is also important for dynamic simulation where a reference generator is needed (in PowerGrids library).
In the description of CGMES standard, the reference (slack) generator is marked by the attribute SynchronousMachine.referencePriority in _SSH.xml, where 0 = don't care (default), 1 = highest priority (slack generator), and 2 is less than 1 and so on.
For instance:
<cim:SynchronousMachine.referencePriority>1</cim:SynchronousMachine.referencePriority>marks a generator with the highest priority, i.e. the slack generator, and should be replaced by a slack object in ModPowerSystems. Whereas
<cim:SynchronousMachine.referencePriority>0</cim:SynchronousMachine.referencePriority>
marks a normal generator that can be replaced by a PVnode object.