A control system for a wind turbine comprises: a sensor arrangement for capturing measures related to the turbine operation and fatigue accumulation; an upper level controller, which, on the basis of a statistical treatment of said measures, calculates optimized control settings at discrete points of time; a measurement module which processes said measures into instantaneous values; and a lower level controller that receives said control settings and said instantaneous values and calculates instantaneous optimal commands to control turbine actuators. The lower level controller comprises a continuous-time damage model which calculates the rate at which damage is accumulated at any time, and an optimal controller which controls operational states of the turbine, either by directly giving feedback of the instantaneous values to the actuators, or by generating a turbine performance objective function which is continuously optimized by repeatedly solving a receding horizon optimization problem.