Wind turbine control system

A closed loop electronic control system for wind turbines to extract the maximum power available from variable wind speeds by maintaining operation of the turbine close to the Betz limit. Two control systems are claimed, both comprise two anemometers to measure the wind speed arriving 4 and leaving 5 the blades of a wind turbine and a method of transforming the impedance of a fixed resistive power load with controls 6 to alter a switched mode voltage convertor 3 that supplies power to a force cooled resistive load 8. This works to modify the braking force and thus give the optimum angular velocity of the turbine blades. The first embodiment uses computing means to calculate the optimum velocity in order to satisfy the Betz criteria. The second embodiment uses computing means to calculate the power delivered to the heating element as a function of the output voltage with respect to the incident and exhaust wind speeds. It also using a fuzzy logic system to vary the switcher voltage gain using a recursive iteration to maintain the maximum power extraction. The resistive load may be used to heat a liquid or gas 7 for domestic consumption, e.g. hot water.