Renewable energy sources, such as wind, solar, wave, tidal and hydro, play a significant role in today’s electrical power systems and the share of electricity produced through this kind generation plants constantly increases. In particular, wind and solar installations are being favored by system utilities and power providers. As an example, the capacity of renewable generation in Sweden reached 51% of the total generation capacity in 2017, with a peak of about 11% of energy production coming from wind. Moreover, by the year 2040, the total energy generation capacity in Sweden is projected to go '100% renewable', with about 45% coming from wind and solar sources.
In line with this trend, wind power has become one of the fastest growing sources of electricity globally over the past 15 years. As a result of this, various researches have gone underway to enhance the energy production, increase the lifetime of the wind turbines and their ability to safely connect to the power system. Modern wind turbines are interfaced with the power system through power-electronic converters to increase their flexibility and functionalities, allow to operate at variable speeds as well as to facilitate grid-code compliance. But an increased penetration level of wind power could compromise the stability of the power system due to various factors including: the intermittent nature of the produced power, reduced system inertia and interactions between power-electronic converters as well as between converters and other passive components installed in the power systems. In particular, the latter has been experienced in a number of actual installations, where the first recorded event occurred in southern Texas in 2009, when a wind farm became radially connected to a series-compensated transmission line. The aim of this thesis is to provide the groundwork for a deep understanding of the root causes of this specific phenomenon. Through system modeling and frequency-domain analysis, the work focuses on the identification of the key parameters that affect the stability of the system, understand their impact as well as proposing effective countermeasures.