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Abstract:
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This thesis report describes the modeling procedure for available the wind turbine generator (WTG ) technologies . The models are generic in nature and manufacturer independent . These models are implemented on commercially available dynamic simulation software platforms like PSCAD /EMTDC and MATLAB /SIMULINK . A brief introduction to the available WTG types is provided to understand the technological differences and their key features . The related theoretical concepts to the working of a WTG are explained , which acts as an aid for model development and implementation . Using the theoretical concepts as basis , a WTG model is divided into four parts :
1 . Aerodynamic model
2 . Mechanical drive train model
3 . Electrical machine model
4 . Controller model
Once the different parts of a WTG are introduced , a groundwork for model implementation on the software platforms is laid . A step -by -step process of implementing a PSCAD or MATLAB model of a WTG is introduced in this thesis . Starting with the most fundamental WTG technology such as fixed -speed also known as direct -connect wind turbine . The model implementation is adanvced to other superior technology like the dynamic rotor resistance control (DRR ) and the doubly -fed induction generator (DFIG ) . To better understand the working of a DFIG , a current -source regulated model (without electrical machine ) emulating the DFIG is built on both PSCAD and MATLAB . A full blown converter model of the DFIG with back -to -back converter is then built in PSCAD /EMTDC .
An approach to determine the reactive power capability (Q limits ) of a DFIG is described . Rotor current limitation and stator current limitation of the DFIG are considered in determining the minimum and maximum reactive power delievered by the DFIG . Variation in the Q limits of a DFIG for change in wind speed is analysed with two different wind speed scenarios .
1 . Wind speed from cut -in to rated i .e . 6 m /s - 14 m /s .
2 . Wind speed above rated to cut -out i .e . 14 m /s - 20 m /s .
Such an analysis , is useful in determining the operating mode of the DFIG . At low wind speeds (below rated ) , the DFIG can be operated as a STATCOM for exporting and importing reactive power (similar to synchronous machines ) . While above rated wind speeds , the DFIG can be set to produce maximum active power . Using the DFIG current -source model implemented in MATLAB /SIMULINK , laboratory experiments to plot the power profile of the DFIG is explained . Another experiment to perform independent P -Q control of the DFIG is also included in this report . |