A Study on Short Circuit Ratio as a Metric for the Voltage Stability of Offshore Wind Farms Connecting with High Voltage AC Transmission Cables

The paper examines the relation between the short-circuit ratio (SCR) and voltage stability for offshore wind farms. Considering the capacitance of submarine transmission cables as well as the short circuit capacity at the onshore substation, it derives the equations for SCR by applying the Thevenin's theorem to the four-terminal circuit. The obtained equations reveal that, in case of low SCR at the onshore bus, the SCR at offshore bus can be greater than that at the onshore bus and can increase as the capacity of the wind farms increases. However, studies with a metric for voltage stability show that the voltage stability is deteriorated with the increase of the offshore wind farm. The results indicate that SCR—a widely-used metric to evaluate voltage stability—can bring misleading results for the voltage stability of offshore wind farms.