Contribution to the Control of Doubly Fed Induction Machine DFIM

-IIAbstract Currently, doubly fed induction generators (DFIGs) are widely used for wind turbines. Compared to other variable-speed generators; the main advantage of the DFIG is that the power electronic devices must deal with only about a third of the generator power, compared to full power converters used in synchronous generators . This difference reduces the costs and losses in the power electronic components, rather than other solutions, such as fully converting systems; finally, the overall efficiency is improved. Furthermore, among all the induction generator configurations for generation systems the use of (DFIG) configuration with back to back pulse width modulated voltage source converters (VSC) is one of the best topologies available and it is suitable for both grid connected systems as well as standalone systems. Here only stand-alone application of DFIG is considered. In this thesis, mathematical modelling of doubly fed induction machine is presented. Two control approaches are proposed to improve the control of the rotor side converter which give the best solution to overcome the drawbacks of the recent control methods and provide a high performance stator- voltage magnitude and frequency regulation for all possible operation scenarios (voltage magnitude, load, and rotor speed variations). Various aspects of standalone DFIG generation system such as stator-voltage magnitude and frequency regulation, computational requirement minimization, sensors number reduction, from rotor side converter control is carried out. All proposed control methods have been verified in both simulation and 3 kW DFIG laboratory experimental bench