Replace power factor input by reactive power or phase angle input in multi phase converters

[christiankral]

The transient multi phase inverter model now uses a power factor input. In the actual implementation the reactive power is generated such way, that an inductive load can be supplied. Alternatively, this model shall be adapted that the reactive power or the phase angle phi shall be used instead of the power factor cos(phi). This change will then enable to switch from inductive to reactive loads, if required.

@luizhrbueno Do you have a preference: reactive power or phase angle input?

[lhbueno]

Set of reactive power could be an interesting idea, however, it might cause issues in cases of low irradiation (desired reactive power > power generation).
I believe that just the phase angle is enough.

[christiankral]

As discussed in #11, additionally, an AC current limitation (maximum current IACMax) will be implemented. This feature shall consider the following aspects

• If active power does not exceed the IACMax, reactive power is limited such way that IACMax is not exceeded
• If active power exceeds IACMax, an assert shall be triggered

[christiankral]

I separated the implementation of the phase angle from the implementation of the current limitation (#16).

[christiankral]

Implemented phase angle phi in b1a88aa.