Control of Double Fed Electrical Machine (DFIG)
This project examines different control strategies for DFIG machine used as a generator in wind energy system. Renewable energy sources, especially wind energy conversion systems (WECS) are becoming more and more popular due to rapid consumption of fuel resources in recent years. Doubly fed induction generator based wind turbines are very advantageous because of its four quadrant active and reactive power flow capability and reduced power converter sources. For example, stator active and reactive power can be controlled with a 30% power rated rotor side converter at +/-0.25 slip variation. Robustness of any implemented control structure can easily be lost due to nonlinearities, variations in the DFIG parameters and network voltage failures. In this project we examined the controller structures that do not need information on machine parameter dependent terms. Instead we use simple disturbance observer to evaluate compensation terms. In addition we design controller in the stator voltage frame of references what gives us simpler and more reliable structure. The laboratory setup is developed for verification of the results.