  The ongoing energy transition challenges the stability of the electrical
power system. Stable operation of the electrical power grid requires both the
voltage (amplitude) and the frequency to stay within operational bounds. While
much research has focused on frequency dynamics and stability, the voltage
dynamics has been neglected. Here, we study frequency and voltage stability in
the case of simple networks via linear stability and bulk analysis. In
particular, our linear stability analysis of the network shows that the
frequency secondary control guarantees the stability of a particular electric
network. Even more interesting, while we only consider secondary frequency
control, we observe a stabilizing effect on the voltage dynamics, especially in
our numerical bulk analysis.
