A method of controlling a power plant connected at a point of connection to an electricity grid is provided. The power plant includes a power production facility connected to a power storage facility. The method includes determining a reactive power grid demand and/or voltage grid demand of the electricity grid, obtaining operating data for the power plant facilities, computing reactive power and/or voltage references for the power plant facilities on the basis of the grid demands and the operating data, and operating the power plant facilities on the basis of the references such that a net reactive power and/or a net voltage at the point of connection fulfills a grid demand. A plant controller for controlling a power plant is also provided. A power plant including power production facilities connected to power storage facilities, and the plant controller using the method is also provided.