This thesis deals with the dynamics of a wind energy conversion system in a number of control strategies. The thesis begins with a brief review of control and principal modes of operation of wind turbines.

Commercial wind turbines are operated in fixed, twin or variable speed mode. A mode of operation is achieved by controlling either pitch angle or generator reaction torque or yaw angle using nonlinear controllers. Reported studies of wind turbine control in various operational modes are inconclusive. A comparison of different modes of operation of a wind turbine and the suitability of the controller need further investigation.

In this thesis a wind turbine is described that is designed to be capable of operating in any commercial wind turbine mode. The stand-alone Imperial College Wind Energy Conversion System consists of a 6.5 metre diameter, two bladed, teetered rotor, a gear box, a dc generator and a dump load. The system has three control variables, i. e. pitch angle, generator field voltage and yaw angle. Selection of the drive train and the design and development of necessary instrumentation for system control is explained. The system is controlled by nonlinear controllers implemented using a personal computer.

Modelling of the system for the design of controllers is presented. Model linearization and uncertainties are also described. A number of dynamic controller options for the system are considered. The description and design procedures of the PID-type, cascade, optimal state and fuzzy logic controllers are included.

Ten control strategies for the system covering all principal modes of commercial wind turbine operation are explained. The design of controllers for each control strategy is presented. The system is simulated with each control strategy and the performance of the controllers is evaluated. Experimental performance of the system with different controllers in each control strategy is presented. Controller Z:​, performance is analyzed and energy output of control strategies is compared.