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Doubly Fed Induction Generator’s (DFIG) Contribution to Improve Voltage Stability in Grid using Rotor Side Converter and Grid Side Converter

Abstract:

Nowadays wind energy has become one of the most important and promising sources of renewable energy, which gives additional transmission capacity and better means of maintaining system reliability. Variable speed wind turbines that present gives many advantages compared to the fixed speed wind turbines due to growth of technology related to wind systems. These wind energy conversion systems are connected to the grid through Voltage Source Converters (VSC) to make variable speed operation possible. The stator of the generator is directly connected to the grid while the rotor is connected through a back-to-back converter which is dimensioned to stand only a fraction of the generator rated power. Grid connected Doubly Fed Induction Generator (DFIG) gives more efficient to the wind power with the most reliable system in the present era. The DFIG brings the advantage of utilizing the turns ratio of the machine, so the converter does not need to be rated for the machine’s full rated power. The rotor side converter (RSC) usually provides active and reactive power control of the machine but the grid-side converter (GSC) keeps the voltage of the DC-link constant. The additional advantages of reactive power generation by the GSC are usually due to the fact that it is more preferable to do so using the RSC. However, within the available current capacity the GSC can be controlled to participate in reactive power generation in steady state as well as during low voltage periods. The GSC can supply the required reactive current very quickly whereas the RSC passes the current through the machine resulting in a delay. Both converters can be temporarily overloaded, but at that time, the DFIG is able to provide a considerable contribution to grid voltage support during short circuit periods. In this paper we focus on analysing a wind turbine system using MATLAB Sim Power Systems. The machine used was a doubly fed induction generator (DFIG). A fault ride through situation was investigated. As protection against short circuit transients, the crowbar protection was modelled.

Author Name : K.R.Venkatesan, J.Madhavan

Keywords: Wind Power, Voltage Source Converter, Doubly Fed Induction Generator (DFIG), Crowbar.