Abstract : The deregulation of the electricity market modifies considerably the technico-economic approach in the exploitation and the optimization of power systems. In this new context, power system specialists are more and more confronted with many challenges. Thus the power system operators are limited to serving the actual power demand by pushing the operating point closer to the generation and tie-line stability limits. Due to the weakness of these tie-Hnes, oscillations are often created between generating stations of different areas in the power system. This kind of oscillations is called "inter-area" oscillations ; for an efficient damping of these oscillations, a supplementary damping loop can be set on Power System Stabilizers (PSS) or on reactive power injectors (FACTS devices). These controllers can have "distant input signaIs": signaIs coming from other area that the controller's one. These remûte input signaIs are synchronized via signaIs emitted by Global Positioning System satellites. In this work, the network analysis is yield with the small signal stability theory and the controllers are tuned using LMI (Linear Matrix Inequalities techniques). Perfonnances and robustness of these controllers are compared to controllers designed with other techniques (particularly with Residue and non-linear techniques). Moreover, because of deregulation of the electricity market, the increasing presence of controllers in power systems, and therefore their increasing closeness, may result in harmful interactions between the various controllers, called "control interactions", that can noticeably decrease overall system performance. An efficient and innovative strategy for control interaction mitigation is proposed. This strategy consists on the design of a controller having distant signaIs input and on the use ofLMI techniques (Linear Matrix Inequalities) to tune it. Simulation tests carried out by using two test systems show the effectiveness of the different approaches.