Resumo:
Voltage stability problems have been a focus of special attention in the last
years. Many papers have shown the importance of the study and many occurrences
around the world show it may have serious consequences. Since power systems have
been working under severe operating conditions, the ability of keeping a power system
stable under the voltage collapse point of view has become a point of concern and
effective measures to improve the reactive power and voltage control must be taken. If
there measures are not taken, successive load increase may drive a system to instability.
In this scenario, analyzing the operating points of interest must include the
diagnosis regarding its stability, as well as the load margin calculation and control
actions determination. Because this is a vast area of study, this work focuses on the
effects of reactive power in the load margin. For this sake, some methodological tools
already shown as effective are employed.
Therefore, an association between the pieces of information obtained from the
continuation method and QV curve is developed. This is obtained by using some
programs already available in the literature. The objective is to extract and discuss
some relevant aspects about the study. For this sake, four test systems (IEEE-14, IEEE 30, IEEE-57 and IEEE-118 buses) are used.
In a first stage, critical buses, buses candidate for reactive power compensation
with the meaning of reducing losses and buses subject to reactive power monopoly are
identified; in a second stage the load margin is calculated by the continuation method.
Finally, the QV curve is executed for the base case and for an operating point close to
the voltage collapse point, with and without reactive power compensation.
The results obtained show that the proposed methodology may be useful to
determine a reactive power compensation strategy aiming to avoid voltage collapse
problems
