Secondary voltage control system based on fuzzy logic

•We focus on secondary voltage control.•Critical buses are identified to form critical areas.•Modal analysis employed.•Fuzzy logic employed for voltage control.•IEEE 118-bus academic system employed.

This paper discusses the problem of secondary voltage control in power systems. This problem is of deep interest for researchers and engineers, since it imposes serious restrictions to system's operators. In general, this problem is resolved by selecting pilot buses representative of a region. Instead, in this paper, modal analysis is used to identify a coherent group of buses to be monitored. The set of information collected by modal analysis is considered by a fuzzy logic-based algorithm, so a voltage control policy is implemented. The academic IEEE 118-bus system is employed with all its limits considered, so the results may be reproduced.