Abstract: The present disclosure relates to a method and system for evaluating a grid condition of an AC power grid. A time series of voltage and current signals of the AC power grid is captured and a local frequency of the AC power grid is identified. The time series of the voltage and current signals is transformed at the identified local frequency of the AC power grid into transformed signals. Equivalent circuit parameters are estimated from the transformed signals based on a description of an equivalent circuit of the AC power grid. A value of a grid condition indicator is determined based on the calculated equivalent circuit parameters and the identified local frequency of the AC power grid and processed in a grid monitoring system for evaluating the grid condition of the AC power grid.

Abstract: System for providing electrical power to wind turbine components comprising a busbar, an electrical grid, and an auxiliary power source for selectively providing electrical power to the busbar with an auxiliary power voltage, wherein the main voltage is different from the auxiliary power voltage. The system includes one or more wind turbines comprising a wind turbine generator, a main transformer for connecting the wind turbine generator to the busbar, one or more wind turbine components, and an auxiliary wind turbine transformer. The wind turbine components are arranged to be selectively connected to the main transformer and the busbar through a first path or a second path. The system is configured to select the first path if the voltage at the busbar is the main voltage and to select the second path if the voltage at the busbar is the auxiliary power voltage.