Use Powerconnections in Subsystems

[HaSchneider]

How can I use powerconnections as interfacing connections in Subsystems?
I tried different things like the following but without succes:

class MySubsystem(Subsystem):
    def __init__(self, label):
        self.num_in = 2
        self.num_out = 1
        super().__init__(label)

    def create_network(self):
        hex= SimpleHeatExchanger('hex')
        c1 = Connection(self.inlet, "out1", hex, "in1", label="1")
        c2 = Connection(hex, "out1", self.outlet, "in1", label="2")
        pc1 = PowerConnection(self.inlet, "power_out1", hex, "t", label="3")
        self.add_conns(c1, c2, pc1)
mysub = MySubsystem('mySubsystem')
nw = Network()
so = Source("source")
si = Sink("sink")
ps= PowerSource('heat')
c1 = Connection(so, "out1", mysub, "in1", label="1")
c2 = Connection(mysub, "out1", si, "in1", label="2")
c3 = PowerConnection(ps, "out1", mysub, "in2", label="3")
nw.add_conns(c1, c2)
nw.add_subsystems(mysub)

Results in:

ValueError: Error creating connection. Specified connector for inlet of class SubsystemInterface (power_out1)  is not available. Select one of the following connectors .

[fwitte]

Hi @HaSchneider,

quick and unfortunate answer: Not possible right now (#839). But this is a good incentive to change that. I will make a draft for a SubsystemInterface (and respective changes to Subsystem) this weekend (unless you are faster ;)).

Best

[fwitte]

My approach would be extending SubsystemInterface to handle all types of connections and allow to specify num_power_in etc. in Subsystem.__init__. By default power inlets and heat inlets and outlets would be zero. With this you are are not forced to declare them in your __init__ for backwards compatibility. Only question would be, should that forcing to declare them be kept optional or be mandatory in a future version?

[fwitte]

@HaSchneider: this would be the draft #1014, can you review that?

[HaSchneider]

Nice, looks good and the use is straight forward!
In my opinion, only the interface connections that are actually needed should have to be declared. Otherwise you would need to write too much unnecessary code. So I would be in favor of keeping the current solution.

[fwitte]

Okay, so then we go with mandatory specification for normal Connections because that is kind of the default case, and optionally specify these extra parameters :).