I. Introduction
Disturbances, sustained power system oscillations, and their effective amelioration have for many years presented a major challenge to the electricity supply industry. This is especially the case in the context of the rapidly growing integration of distributed generation and loads into power transmission and distribution networks [1]. Much previous work [4] has centred round the question as to what effective role such widely used devices as the generator automatic voltage regulator (AVR) and power system stabilizer (PSS) play in the attenuation of these power system instabilities. Other related questions concern the best power system location for PSSs and how best to assess their proper tuning and robustness [2] in the face of changing power system operating conditions.