Ideal voltage source with constant amplitude and phase, and with resistive-inductive inner impedance.
There are 3 different initialisation choices.
1) v_ini, alpha_ini initial terminal voltage and phase angle, 2) v_ini, p_ini initial terminal voltage and active power, 3) pq_ini initial terminal {active power, reactive power},
Note: v0, alpha0 denote the exciting voltage ('behind reactance'), NOT the terminal voltage. v0 and alpha0 are kept constant during simulation. The values are determined at initialisation by the respective initial values above.
Frequency: the source has always system-frequency.