A wind turbine comprising a plurality of wind turbine blades, a blade anti-ice system including a blade heating arrangement associated, wherein the anti-ice system includes a control system and a power supply configured to provide power to the blade heating arrangement, characterised in that the power supply comprises a power converter. A benefit of using a power converter to supply electrical power to the heating devices is that power can be applied in a stepless manner. A much finer degree of control is therefore achieved over the thermal energy applied to the blade since the power can be ramped up gradually as the system controller determines that the icing conditions are becoming more severe. As a result of the use of the power converter, the magnitude of thermal energy that is applied to the blade can be increased gradually and smoothly.