Grid forming and grid following comparison for an offshore wind farm connected via a HVAC cable

Due to the more constant and strong wind resource and an improvement in offshore infrastructures, wind turbines are being positioned further offshore. Although for distances longer than 80-100 km HVDC cables are usually preferred for the transmission system, this paper presents a study which considers a wind farm aggregated model connected to the onshore electrical grid via a HVAC export cable. Two converter control strategies are compared, a grid forming (GFM) and grid following (GFL) units, to identify and quantify any advantage and challenges that the GFM technology might have. These controllers are compared in terms of frequency and time domains considering different power and voltage operating points. Power and voltage steps, polezero maps and disk margins are the frequency studies chosen to compare robustness and stability. A time domain assessment is performed to study the impact of both controllers with regards to voltage sag and frequency drops. Further, an analysis of different grid strengths was performed. The GFM controller has shown to be more robust to all kinds of disturbance and grid strengths