An application of fuzzy logic based control for power systems governing multiple flexible alternating current transmission system (FACTS) devices is described here. Sufficiently accurate relations have been derived to determine setpoints of FACTS devices using fuzzy reasoning, in order to meet the requirements for power flows. These expressions are based on so-called coefficients of influence, which are online adapted employing a fuzzy gain scheduling method. The controller prototype has been tested using simulation software for power systems in order to assess its performance considering the Swiss power system as a study case. Results show that the developed control strategy is a very effective tool for dealing with power flows in complex transmission networks using multiple FACTS devices