Abstract

The subject of this study is the design, construction and simulation of a small wind turbine with an axial flux permanent magnet generator. In this framework a small wind turbine was fully constructed based on existing plans. Initially, the basic characteristics, uses and prospects of small wind turbines are mentioned. Basic principles of aerodynamics are briefly explained followed by the description of the way of constructing the rotor blades, the yaw and the protection system.

The characteristics, main topologies and basic equations of axial flux permanent magnet machines are described. A review of scientific literature is undertaken on axial flux generators used on wind turbine applications. The design method of the generator is presented, a simulation of the magnetic field is performed using the FEMM finite element analysis software and the induced EMF is estimated as well as the performance of the generator with the use of MATLAB.

The construction of the generator is described and the results of experimental measurements on the generator are compared with the outcome of the simulation. Subsequently, the different ways of connecting the small wind turbine are examined. Reference is made to microgrids, as the wind turbine can be a part of them, and different ways of connecting a small wind turbine are discussed. The variable speed operation when connected to an AC bus of the utility grid or a microgrid is described and the MPPT function is explained. The operation of the wind turbine when connected to a DC bus either directly to a battery bank or with an MPPT converter is being examined. The operation of the wind turbine that was constructed is simulated for the two different ways of connection to a DC bus. The power curve and other characteristic curves for both connection schemes are calculated by the development of models in MATLAB. The annual energy yield is estimated for different mean windspeeds and comparisons are carried out. Finally, improvement proposals are being made. As far as the DC coupling is concerned, the possibility of increasing the produced power with the connection of an inductance is investigated. The power curve and the annual energy yield are estimated and show a significant increase compared with the direct battery connection. As far as the generator is concerned, a new design is carried out with an improved stator winding for AC coupling and low wind speeds.

Keywords: small wind turbines, axial flux machines, microgrids, battery charging, DC coupling, MPPT

Author: Panos Kotsampopoulos / kotsa@power.ece.ntua.gr

Responsible PhD: Kostas Latoufis / latoufis@power.ece.ntua.gr

Supervising Professor: Nikos Hatziargyriou / nh@power.ece.ntua.gr

PDF: Full version (Greek) and Short version (English)