Superclass of elements which have one port i.e.two electrical pins of
type ComplexPin.
The identity of the phasor of the current flowing into pin p
and the phasor of the current flowing out of pin n is forced
by internal current balance.
The only differences to class OnePort are the calculations of the
internal current phasor as well as the values of active and reactive
power.
Hence, class OnePortSrc shall only be used to build source components
like voltage sources or current generators.