Modelling and design of grid connected doubly fed induction generator

Date

2019-12

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Abstract

This thesis focuses on the variable wind speed application of the Doubly Fed Induction Generator (DFIG). The vector control scheme is applied to the DFIG for the control of the torque, the dc bus voltage and the reactive power exchange with the grid. The grid connected DFIG is simulated and with the controller blocks for the rotor side converter and grid side converter control. The vector control of the DFIG is performed by applying stator flux orientation control scheme in synchronously rotating dq frame for the rotor side. The grid voltage orientation vector control is implemented in the grid side converter. The torque of the induction generator is controlled by the rotor side controller while the dc-link voltage and the exchange of reactive power with the grid is controlled by the grid side converter. The DFIG based WECS system due to variable speed application and low converter rating makes it one of the most popular wind turbines used. The variable speed application of the DFIG is conducted in this thesis. The vector control scheme is one of the most popular control schemes. The robust control of the machine is possible with minimum harmonic distortion. The current loops and the overall vector control scheme are studied in detail in the thesis. The maximum power point tracker is also implemented to maximize the power output of the wind turbine generator system. The injection of the third harmonics to the reference signal to increase the output voltage still maintaining the power quality is also implemented in the thesis. Furthermore, the analysis of the crowbar protection system to protect the system under symmetrical voltage dips is also performed.

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Keywords

Doubly fed induction generator (DFIG), Vector control, Variable speed wind turbine

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