Wind farm stability analysis in the presence of variable-speed generators

Variable-speed technologies have been adopted to improve the efficiency of electricity generation in wind farms. Among these technologies, doubly-fed induction generators have widely spread and their stability issues have been experienced and analysed. In recent years, permanent-magnet synchronous generators have been also exploited, connected to the grid through full-scale converters, ensuring high flexibility, reducing losses and weight. The presence of these technologies heightens the necessity of deeply investigating wind turbine behaviour under different disturbances. In this paper, a small- and large-disturbance stability analysis is carried out in order to compare dynamic characteristic of wind farm equipped with the aforementioned generation technologies. To this purpose, a detailed model of wind turbine, together with relevant control schemes, is adopted for each generator of a real-sized wind farm. The compliance of the plant with fault-ride-through requirements imposed by transmission system operator is also verified.