The present invention provides a method of operating a wind turbine including a generator (4) that provides variable voltage at variable frequency and has a stator and a rotor. The wind turbine includes a turbine assembly (2) having at least one blade for rotating the rotor of the generator (4), and a power converter that interfaces the generator (4) to a supply network (NETWORK) operating at nominally fixed voltage and nominally fixed frequency. The power converter includes a generator bridge (10) electrically connected to the stator of the generator (4) and a network bridge (14). A dc link (12) is connected between the generator bridge (10) and the network bridge (14). A filter (16) having network terminals is connected between the network bridge (14) and the supply network. A first controller (18) is provided for controlling the operation of the semiconductor power switching devices of the generator bridge (14). Similarly, a second controller (46) is provided for controlling the operation of the semiconductor power switching devices of the network bridge (14). In response to a change in wind speed (e.g. an increasing or decreasing wind speed) the method comprises the steps of: (i) controlling the second active rectifier/inverter (14) to change the level of power exported out of the dc link (12) such that the dc link voltage changes from a desired level, and (ii) controlling the first active rectifier/inverter (10) to import sufficient current into the dc link (12) through the generator bridge (10) from the generator (4) to restore the dc link voltage to the desired level.