Power systems show a complex non-linear behaviour due to different phenomena widespread over different time frames. Thus, power system stability is a significant research issue. Bifurcation theory can contribute to face these power system security problems. The study of local bifurcations and chaos through the analysis of power system equations can provide a deep insight into the complex behaviour of such large and interconnected systems. This paper describes the numerical continuation methodology and it shows an application example to voltage control in power systems.