22-05-2013, 11:46 AM
Reduced-order Models of Wind Turbines
Introduction
Increasing numbers of wind turbines are being erected. In the near future, they may start to
influence the dynamics of electrical power systems by interacting with conventional
generation equipment and with loads. The impact of wind turbines on the dynamics of
electrical power systems therefore becomes an important subject, studied by means of
power system dynamics simulations. Various types of power system dynamics simulations
exist and the approach depends on the aspect of power system dynamic behaviour being
investigated.
In this chapter, the focus is on fundamental frequency simulations, also known as
electromechanical transient simulations. In this kind of simulations, the network is
represented as an impedance matrix and only the fundamental frequency component of
voltages and currents is taken into account in order to reduce the computation time. This
simulation approach is mainly used for voltage and angle stability investigations. Models of
wind turbine generating systems that match the fundamental frequency simulation approach
are presented and their responses are compared to measurements.
Chapter outline
First, the most important actual wind turbine types will be described briefly. Although this
will probably be done at several places in the book, it is essential to do it in this chapter as
well, in order to allow the chapter to be read independently. The description will, however,
be very compact and the reader will be referred to other places in the book and to other
literature, in which the wind turbine types are described more elaborately. Then, the
principles of fundamental frequency simulations will be summarized, but the reader will be
referred to Chapter 28, in which modelling and simulation is treated in a more general way
and the assumptions on which the models are based are stated.
The main part of the chapter will consist of models of the subsystems of which the three
described wind turbine concepts consist, namely: rotor, generator and controllers (if any).
The response of the models to a measured wind speed sequence will be compared mutually
and to measurements. However, the reader will be referred to Chapter 32, where model
validation is treated more elaborately.