Control policies for wind-energy conversion systems

Wind energy is usually converted into electrical energy through a wind rotor driving a generator. It is well known that maximum conversion efficiency occurs when the wind rotor is loaded in such a way that its rotational speed is allowed to fluctuate in sympathy with wind-speed variations. In the paper, the wind-rotor/generator dynamics are investigated for a number of control policies, and it is shown that the system response is a function of wind speed. Owing to this relationship, control strategies based on static optimum matching premises are unlikely to be optimal under continuously changing conditions. To prove this hypothesis, the aerogenerator dynamics were simulated on an analogue computer, and, for a given recorded windspeed sample, the energy delivered was measured for a number of control strategies. The results indicate that, for the wind sample used and aerogenerator simulated, sophisticated control policies do not necessarily result in maximum energy yield. An attempt is made to interpret this paradox in terms system dynamics