In order for the island of Ireland to achieve the ambitious government target of 40% of electrical energy from renewable energy sources, mainly from wind turbine generation, significant changes in power system network topology and operational procedure are required. The impact of these changes on power system stability needs to be fully investigated to ensure secure and reliable operation of the power system. Therefore, the aim of this thesis is to analyse the impact of wind turbine generation on small signal and frequency stability whilst taking advantage of phasor measurement unit (PMU) technology installed in the All-Island power system for the purpose of stability analysis and parameter estimation. PMU data of active power from the main AC North-South interconnector as well as from fixed-speed and doubly-fed induction generator based wind turbines is employed to obtain the All-Island inter-area and wind turbine oscillation modes. A correlation coefficient analysis between inter-area frequency oscillation and the active power output of thermal power plants and wind turbine generation is conducted to identify the source of the oscillations. A number of case studies with differing operational procedures are simulated using DigSILENT to understand the mechanisms that may influence the small signal stability performance of a power system with high DFIG penetration. The implementation of Prony Analysis to analyse small signal stability is conducted by employing both simulated and actual PMU ringdown data. Both wide-area and single-site PMU based techniques are assessed for purposes of monitoring small signal stability. The frequency response metrics are assessed with respect to the power system’s intertia and system non synchronous penetration to understand the significance of these parameters during frequency events. A method to estimate a synchronous generator’s inertia constant from PMU data during a frequency disturbance is proposed and described.