# Variable Speed Wind Turbines

The combined blade element and momentum theory is an extension of the Rankine-Froude actuator disk theory described in Section 3.3.2. The blade element momentum theory divides the rotor blades into a number of radial blade sections elements , each at a particular angle of attack. These blade elements are assumed to have the same aerodynamic properties as an infinitely long or 2-D rotor blade with the same chord, and aerofoils. This implies that 2-D aerofoil data i.e. lift, drag and moment...

## History from windmill to wind turbine

The historic development of using wind as a source of power shows an evolution from simple drag-type vertical-axis windmills generating mechanical power for local use, via stand-alone wind turbines designed for battery charging and single grid-connected wind turbines producing AC power using aerodynamic lift, to wind farms supplying electricity to the utility grid for distribution to the consumers. In this subsection we shall briefly review this transition from windmills to wind turbines. The...

## Rankine Froude actuatordisk model

The simplest and oldest mathematical model which describes the wind turbine dynamics is the Rankine-Froude actuator-disk model. The concept was introduced by R.E. Froude in 1889 68 , after W.J.M. Rankine 231 had introduced the momentum theory. In this model the rotor is replaced by an actuator-disk, which is a circular surface of zero thickness than can support a pressure difference, and thus decelerate the air through the disk. Physically, the disk could be approximated by a rotor with an...

## Overview wind turbine design codes

In the wind energy community the following design codes are commonly used to model and simulate the wind turbine dynamic behavior, as well as to carry out design calculations ADAMS WT (Automatic Dynamic Analysis of Mechanical Systems - Wind Turbine) 57 . ADAMS WT is an add-on package for the general-purpose, multibody package ADAMS. ADAMS WT is developed by Mechanical Dynamics, Inc. (MDI) under contract to the National Renewable Energy Laboratory (NREL), specifically for modeling...

## Main wind turbine modes of operation

In this chapter the main wind turbine modes of operation will be discussed. In general, the following modes of operation can be distinguished 179 In the startup mode the rotor of the wind turbine is accelerated, and the generator is connected to the utility grid. In the power generation mode, power is extracted from the wind and converted to electricity. In this mode the wind velocity ranges from the cut-in wind velocity Vci, via the rated velocity Vr to the cut-out wind velocity Vco as...