Operating a wind turbine to provide reactive power

A method of operating a wind turbine, wherein the wind turbine comprises a wind turbine rotor and an electrical power system including a doubly-fed induction generator mechanically coupled to the wind turbine rotor, wherein the electrical power system is configured to exchange electrical power with a power grid, wherein the method comprises:

• obtaining a grid requirement for the wind turbine to exchange reactive power with the power grid, wherein providing the reactive power in accordance with the grid requirement by the electrical power system requires the electrical power system to consume an active power amount;
• and
• providing, by the electrical power system, the reactive power in accordance with the grid requirement to the power grid while consuming the active power amount, wherein the providing of the reactive power includes:
• supplying the electrical power system with the required active power amount, wherein the wind turbine is operated such that the electrical power system does not deliver active power to the power grid, and
• operating the doubly-fed induction generator as a variable-speed rotating condenser to provide at least a part of the reactive power to the power grid;
• wherein the reactive power in accordance with the grid requirement is provided when a wind speed at the wind turbine is below a cut-in wind speed of the wind turbine or close to the cut-in wind speed, wherein the wind-speed is close to the cut-in wind speed when the wind speed differs from the cut-in wind speed by less than 10, 5 or 3 percent of the cut-in wind speed.