This paper presents an approach to control power systems with several flexible AC transmission system (FACTS) devices. This approach relies on ‘robust control’ design techniques, but uses some heuristic rules for defining the controller design procedure instead of being based on a precise definition of model uncertainties. Design algorithms of and robust controllers are cast in a ‘black-box’ framework, leaving some free design parameters to be tuned by the user. The resulting controllers have decentralized structure, using only local information. The strong interconnection between two FACTS devices in a power system is shown to represent a difficult situation for conventional PID controllers. This situation is directly solved by the proposed methodology.