Abstract
With the situation of energy source exhaustion and environmental pollution, the wind energy generation is gaining more and more attention around the world. It is now recognized that many large farms will employ doubly fed induction generator (DFIG) variable speed wind turbines. Hence, some elementary sensor-based flux-oriented control strategies have been successfully implemented in current wind power industry practice. Also, it is very important to reduce cost. Sensorless control might be a good way to save the cost of sensor and provide similar satisfactory transient performance of sensor-based control. The main theme of this thesis will study a model reference adaptive system (MRAS) for a speed sensorless control of the vector controlled DFIG system. The main contributions of this thesis can be summarized as follows: First, conducting the Static characteristics of DFIGs and their operating capacity. Second, the dynamic model of grid side converter and rotor side converter will be constructed, respectively. According to those models, the dc-link control for grid side converter and the active/reactive control for rotor side converter can be shown. Third, we propose two sensorless controls, including the Back-emf model reference adaptive system control and the Instantaneous-reactive power model reference adaptive system control, are studied. Also, we simulate those two sensorless controls by Matlab/Simulink. Finally, a xPC system which is constructed by Matlab/Simulink control a 2.2 kW DFIG hardware platform in real time. The Back-emf model reference adaptive system control will be use in the DFIG system. We will show the measured waveforms to demonstrate the performances of the proposed sensorless controls.