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Advanced modeling and analysis of the doubly-fed induction generator based wind turbines
The doubly fed induction generator based wind turbine (DFIG-WT) with a partially rated converter, which is currently the dominating concept in the market, suffers from high short-circuit current and DC voltage magnitudes during symmetrical and unsymmetrical grid faults. The incorporated frequency converter is sensitive against high current and voltage magnitudes. Therefore, a proper protection is essential. This can be achieved through protective devices like chopper and/or crowbar or through full disconnection from the grid under severe fault conditions. However, this may not subject the DFIG-WT to the grid codes requirements. Furthermore, the high short-circuit current magnitudes will eventually elevate the fault current levels in the grid. Therefore, a deep understanding of the dynamic response of the DFIG-WT during different types of fault is essential in, assessing fault ride through (FRT) capability, proper design of the electric power system component and right settings of the protective relays for selective disconnection. In this thesis a detailed modelling of the individual components of the DFIG-WT considering all the system non-linarites was made. A controller was developed for each of the turbine, the machine side converter and the line side converter. The controller allows for maximum energy yield, fast and accurate response, and a separate control of the positive and negative sequence components as well as selective frequency components. A new criterion was proposed to assess the stability of the DFIG-WT output currents and voltages when connected to the grid with the consideration of the system’s non-linarites. A detailed analysis of the DFIG-WT response to symmetrical and unsymmetrical faults was carried out. The analysis has considered the complete system considering the controller influence as well as the system’s non linarites. Based on the analysis a new set of mathematical equations describing the short-circuit current, transient impedance, time constants and eigen frequencies were proposed ...
Advanced modeling and analysis of the doubly-fed induction generator based wind turbines
The doubly fed induction generator based wind turbine (DFIG-WT) with a partially rated converter, which is currently the dominating concept in the market, suffers from high short-circuit current and DC voltage magnitudes during symmetrical and unsymmetrical grid faults. The incorporated frequency converter is sensitive against high current and voltage magnitudes. Therefore, a proper protection is essential. This can be achieved through protective devices like chopper and/or crowbar or through full disconnection from the grid under severe fault conditions. However, this may not subject the DFIG-WT to the grid codes requirements. Furthermore, the high short-circuit current magnitudes will eventually elevate the fault current levels in the grid. Therefore, a deep understanding of the dynamic response of the DFIG-WT during different types of fault is essential in, assessing fault ride through (FRT) capability, proper design of the electric power system component and right settings of the protective relays for selective disconnection. In this thesis a detailed modelling of the individual components of the DFIG-WT considering all the system non-linarites was made. A controller was developed for each of the turbine, the machine side converter and the line side converter. The controller allows for maximum energy yield, fast and accurate response, and a separate control of the positive and negative sequence components as well as selective frequency components. A new criterion was proposed to assess the stability of the DFIG-WT output currents and voltages when connected to the grid with the consideration of the system’s non-linarites. A detailed analysis of the DFIG-WT response to symmetrical and unsymmetrical faults was carried out. The analysis has considered the complete system considering the controller influence as well as the system’s non linarites. Based on the analysis a new set of mathematical equations describing the short-circuit current, transient impedance, time constants and eigen frequencies were proposed ...
Advanced modeling and analysis of the doubly-fed induction generator based wind turbines
Naggar, Ahmed El (Autor:in) / Erlich, István
08.09.2017
Hochschulschrift
Elektronische Ressource
Englisch
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