AUTONOMOUS WIND ENERGY-CONVERSION SYSTEM WITH A SIMPLE CONTROLLER FOR MAXIMUM-POWER TRANSFER

The paper describes a small autonomous wind energy conversion system that has been designed and implemented as a prototype unit for the demonstration of wind-electricity generation. A simple, closed-loop control system assures maximum-power transfer by the aid of a lookup table which relates the electrical power output of the system to the shaft speed. The lookup table is deduced from the turbine and generator data and corrected by field tests. A directly-coupled, wound-rotating field synchronous generator is used for energy conversion. The generator speed in this system is variable while the terminal voltage is substantially constant. The terminal voltage is kept under control by varying the field current to meet various load and battery conditions. In the paper a new criterion for determining optimum dimensions of a generator for wind energy conversion system applications is introduced. This criterion envisages a maximisation of the energy output for the chosen wind regime while keeping the generator cost at a minimum. To obtain the optimum solution of the cost minimisation problem, the constrained optimisation problem is first converted to the unconstrained form by using the external penalty approach and then solved using the Devidon-Fletcher-Powel method. Results of the optimisation are presented and evaluated in the paper.