Reactive power analysis and control of doubly fed induction generator wind farm
ABSTRACT Power relations of doubly fed induction generator (DFIG) wind power generation system are analyzed. Based on this, a method is proposed to calculate the reactive power limit. Furthermore, the reactive power control of DFIG wind farm is studied and the control scheme is provided to exert the reactive power dealing capability of wind power system. A reactive power compensation strategy for the local user using DFIG wind farm and the distribution algorithms of reactive power demand are given. Simulation results are provided to verify the proposed theory.
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ABSTRACT: In this paper, a wind energy conversion system (WECS) using a grid-connected wound rotor induction machine controlled from the rotor side is compared with both fixed speed and variable speed systems using a cage rotor induction machine. The comparison is done on, the basis of: (1) major hardware components required; (2) operating region; and (3) energy output due to a defined wind function using the characteristics of a practical wind turbine. Although a fixed speed system is more simple and reliable, it severely limits the energy output of a wind turbine. In case of variable speed systems, comparison shows that using a wound rotor induction machine of similar rating can significantly enhance energy capture. This comes about due to the ability to operate with rated torque even at supersynchronous speeds; power is then generated out of the rotor as well as the stator. Moreover, with rotor side control, the voltage rating of the power devices and DC bus capacitor bank is reduced. The size of the line side inductor also decreased. Results are presented to show the substantial advantages of the doubly fed system.IEEE Transactions on Energy Conversion 10/2002; · 2.43 Impact Factor
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ABSTRACT: A new output feedback control algorithm for a doubly fed induction machine (DFIM) is presented. The asymptotic regulation of active and reactive power is achieved by means of direct closed-loop control of active and reactive components of the stator current vector, presented in a line-voltage-oriented reference frame. To get the maximum generality of the solution, the usual assumption of negligible stator resistance is not made. A full-order DFIM model is used for the control algorithm development. The proposed control system is robust with respect to bounded machine parameter variations and errors on rotor position measurement. In the paper, it is also shown how the proposed current control algorithm can be modified in order to achieve asymptotic active current tracking and zero reactive current stabilization during steady state. An extension for the speed control objective and output EMF control during the excitation–synchronization stage are also presented. Simulation and experimental tests demonstrate high dynamic performance and robustness of the control algorithm for typical operating conditions. The proposed controller is suitable for both energy generation and electrical drive application with restricted speed variation range.Control Engineering Practice. 01/2004;
Conference Proceeding: The influence of control strategies on the energy capture of wind turbines[show abstract] [hide abstract]
ABSTRACT: The energy capture of wind turbines depends not only on the specific wind conditions found at the site where the turbine is installed, but it depends also on the control strategy used for the turbine. As differences in the site conditions make the influence of the control strategy difficult to measure, very different results have been reported. In this paper the results of a simulation-based approach are presented, which are valid for a broad range of sites. It is shown how a lot of the different results found in the literature can be explained by different site conditionsIndustry Applications Conference, 2000. Conference Record of the 2000 IEEE; 02/2000