We have successfully optimized the controller settings of the Power System Stabilizers (PSS) of the remaining units of the ZETES Thermal Power Plant (2790 MW). Optimum settings of the PSSs ensure positive damping not only to local (~1Hz) oscillations but also to inter-area (~0,15Hz) oscillations, and thereby, contribute to stability of Turkish power grid given the significant size of the power plant. We would like to thank all our team and stakeholders who contributed to this critical success.