Simulations and analysis of voltage stability and its influence on power quality are presented in this article. The voltage stability concern to the capacity of the power system to maintain an appropriate voltage profile, both in normal operation and in the event of severe disruption. Methods of assessing stability used here are based on the use of algebraic equations obtained from the model of power flow (static methods). From the continuation power flow, PV curves are used to carry out stability analysis. Such analysis allows evaluating how close the system is of a voltage collapse. Softwares produced by CEPEL: ANAREDE® and PlotCEPEL® were used for simulation and analysis of results.