This a controller block used for modular expansion valve models
as presented in
AixLib.Fluid.Actuators.Valves.ExpansionValves.ModularExpansionValves.
The controller block consists of simple PID controllers for each
expansion valve and no further control strategy is implemented.
However, these PID controller are only initialised and activated if
no external controller is provided (i.g. if useExt =
false).
If the controller block is implemented, appropriate values must be applied for all parameters describing the PID controller.