Dynamic modelling and analysis of a wind turbine with variable speed

Abstract

On behalf of the operation of the Dutch National Wind Farm, which is under construction now, a study is being performed on the control system design of variable speed wind turbines. To realize this a non-linear dynamic model of a wind turbine with synchronous generator and AC/ DC/AC conversion has been set up, which is presented here. The specific dynamic coupling between generator and DC link results in an implicit set of equations. By using an expression for the load angle of the generator the model is made explicit, which makes it suitable for further analysis. With non-linear simulations and eigenvalue-analysis it is shown that the wind turbine has very fast as well as very slow dynamics. There is also a slightly damped oscillation. Using a linear input-output model the interaction has been investigated. Though speed and direct current are stationary decoupled, there is a large amount of dynamic interaction between them. Control systems have to take this interaction into account