Check, improve and document subcomponent handling about dpsim

[JTS22]

Classes which include subcomponents (changes in #141):

Class	Uses mSubComponents	Pre- and Post-step called by parent?	Parent calls Pre- and Post-steps via mSubComponents?	Remarks
DP_Ph1_AvVoltageSourceInverterDQ	yes	yes	yes	-
DP_Ph1_NetworkInjection	yes	yes	yes	-
DP_Ph1_PiLine	yes	yes	yes	changed to utilize mSubComponents
DP_Ph1_PQLoadCS	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
DP_Ph1_RxLine	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
DP_Ph1_RxLoad	yes	yes	yes	changed to utilize mSubComponents
DP_Ph1_RxLoadSwitch	yes	yes	yes	changed to iterate over mSubComponents
DP_Ph1_SVC	no	yes	no	Class is malformed, should not compile. Not making any changes...
DP_Ph1_SynchronGeneratorIdeal	yes	yes	yes	changed to iterate over mSubComponents instead of only using comp. 0
DP_Ph1_SynchronGeneratorTrStab	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
DP_Ph1_Transformer	yes	yes	yes	-
DP_Ph1_VoltageSourceRamp	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task. Also, why does this class exist at all? Can this not be handled by the normal VoltageSource + SignalGenerator?
EMT_Ph1_VoltageSourceRamp	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task. Also, why does this class exist at all? Can this not be handled by the normal VoltageSource + SignalGenerator?
EMT_Ph3_AvVoltageSourceInverterDQ	yes	yes	yes	-
EMT_Ph3_NetworkInjection	yes	yes	yes	-
EMT_Ph3_PiLine	yes	yes	yes	changed to utilize mSubComponents
EMT_Ph3_RxLine	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
EMT_Ph3_RXLoad	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
EMT_Ph3_SynchronGeneratorIdeal	yes	yes	yes	changed to loop over all subcomponents
EMT_Ph3_SynchronGeneratorTrStab	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
EMT_Ph3_Transformer	yes	yes	yes	-
SP_Ph1_AvVoltageSourceInverterDQ	yes	yes	yes	-
SP_Ph1_Load	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
SP_Ph1_NetworkInjection	yes	yes	yes	-
SP_Ph1_PiLine	yes	yes	yes	changed to utilize mSubComponents
SP_Ph1_RXLine	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
SP_Ph1_SolidStateTransformer	yes	has no tasks	has no tasks	changed to add subcomponents into list
SP_Ph1_SynchronGeneratorTrStab	yes	yes	yes	changed to utilize mSubComponents and to call subtasks in parent task
SP_Ph1_Transformer	yes	yes	yes	-

[JTS22]

In addition to the changes made in #141, I propose another way to further unify the behavior of components with subcomponents: By creating a shared superclass MNASimPowerComp that is derived from both SimPowerComp and MNAInterface, it becomes possible to extract the various MNA method calls on the subcomponents into this common superclass. This means that the parent components only register their subcomponents once (e. g. through addMNASubComponent) and then only contain methods concerned with the MNA operations in the parent. The calls to the MNA methods of the child are handled by the superclass instead, drastically cutting down on the amount of duplicated code (especially the for (auto comp : mSubComponents) loop) in the parent classes. The MNAPreStep and MNAPostStep classes contained in almost all parent components can also be merged into the common superclass. A first working example of this can be found in #144 (Comparison with #141 in subcomponents...unify-mna-subcomponents).

[dinkelbachjan]

I would suggest that the new superclass is used only for components that are composed of subcomponents, e.g. PiLine, while the simple components, e.g. Inductor remain untouched. The new superclass could be explicitly called CompositePowerComp. It handles the adding of subcomponents and the collection/arrangement of their mnaPreStep and mnaPostStep methods as you described. Any additional functionalities brought by the composite component class can be encapsulated in mnaParentPreStep and mnaParentPostStep, which are methods offered by CompositePowerComp.

[dinkelbachjan]

@m-mirz We are thinking of inserting a new class CompositePowerComp as described above to unify the subcomponent handling. What do you think about that?