Small-signal stability analysis of HVAC-interconnected offshore wind power plants

The integration of Offshore Wind Power Plants (OWPPs) to power networks is considered as a major step towards the decarbonisation of energy production. These power plants are often connected to the onshore network via High-Voltage-Alternating-Current (HVAC) interconnections and are comprised of numerous devices, such as power converters, reactive power compensators and transmission lines. Each of these devices may introduce detrimental resonances and dynamic interactions between each other and with the onshore network, thus endangering its safe operation. To avoid these interactions and guarantee stability, detailed dynamic studies are necessary. Specifically, eigenvalue-based, small-signal stability analysis is considered a prominent method for identifying oscillatory modes under small disturbances. In this paper, a comprehensive stability analy-sis of a representative, HVAC-interconnected, OWPP is presented based on a small-signal, state-space representation approach. The dynamic models of all participating devices are presented and practical aspects of the analysis are addressed. Then, several parameter stability limits are investigated, with limitations resulting from both the steady state operation point conditions, as well as from the dynamic operation of the system. The linear model used for the study is validated in the time domain against a nonlinear electromagnetic transient model, developed in Matlab/Simulink.