Transient Control Of Double Fed Induction Generator Based Wind Turbines Under Symmetrical Voltage Dips

With the problem of energy crisis and environment deterioration getting worse, more and more attention from the world are focused on the development and utilization of renewable clean energy, and the wind power gains a quite fast development. With the increasing integration of wind power into grid, the issue of fluctuat and random wind power becomes extremely obvious, and its impact on grid seems more severe. As a result, the grid codes is more and more strict to the wind power.The double-fed induction generators(DFIG) are widely used in wind power for its small converter capacity and low cost. But its special structure makes its low transient ride through(FRT) capacity. To realize the FRT, not disconnect from the grid and inject required reactive power current, the DFIG must adopt appropriate transient control scheme. Therefore, this paper will do some analysis and research work on transient behavior control for DFIG under symmetrical voltage dips.Firstly, this paper introduces the operation principle of the DFIG system. Then the mathematical model of the turbine, generator and the convertor are built and their basic control strategy are presented. Then, the transient characteristics of DFIG under symmetrical voltage dips are analyzed. Based on the symmetrical components theory, the positive and natural components of flux, voltage and current are separated. Therefore, the paper estabished the positive and natural model of DFG are established, and some modified reference transient control and Crowbar protection scheme are analyzed and summarized. To optimize the electromagnetic torque, an improved reference transient control is present. In order to verify the validity of the transient control, a simulation study of transient control for DFIG is carried out in Matlab/Simulink. At last, a 10 kW experiment platform of DFIG based on dSPACE is designed and set up. Research and analyse of experiment for grid connection, stable and transient operation of DFIG is done to verify the reliability of the platform and the availability of transient control for DFIG.