Method, power plant, and computer program product for use in controlling power output by a power plant. The power plant includes a wind farm with a plurality of wind turbines, a grid power converter (such as one or more HVDC links), a sensor to measure the frequency of a power grid, and a supervisory controller. The supervisory controller implements a control algorithm that adjusts the power output from the power plant in response to the frequency of the power grid dropping below a first target frequency by changing the pitch of the blades of at least one wind turbine, increasing the level of a portion of the power contributed by at least one wind turbine, or increasing the level of the power output by the grid power converter.