Study On Control Strategy Of DFIG Wind Turbine For The Participation Of System Primary Frequency Regulation

Due to the decoupling control system, variable-speed constant-frequency double fed induction generator (DFIG) wind turbine has no response to the system frequency variation, thus the large-scale wind farm based on DFIG wind turbines does not have the frequency regulation capability as synchronous generator while integrating into the power grid. Thus, with the increase of the capacity of single wind turbine and the rapid development of the integration of large-scale wind power, the pressure of the power grid frequency regulation is larger. In order to make the integrated wind turbines meet the frequency response capability requests of the Grid Code, it’s necessary to do study on the control strategy of wind turbine for the participation of power grid frequency regulation.Based on the traditional power reserve control and kinetic energy control, this paper studies the control strategy of DFIG wind turbine for the participation of power grid frequency regulation while under the rated wind speed, and proposes some effective frequency control method. For under-rated wind speed condition, the deloading operation is firstly realized through over-speeding control, making wind turbine has some power reserves. Then an additional frequency control loop is added to the active power control system of the rotor-side convertor which make wind turbine have frequency response capability. At the same time, And at the same, the determination of some parameters in the additional frequency control loop is analyzed and discussed to ensure the safety and steady operation of the wind turbine during the participation of the primary frequency regulation. For a better primary frequency regulation imitation of synchronous generator, a further design about the additional primary frequency regulation controller on the rotor-side convertor of DFIG wind turbine is made, and the primary frequency regulation that totally imitates the power-frequency characteristic of synchronous generator is realized.At last, a study power system with a large-scale wind farm is built in Matlab/Simulink, as well as the simulation modules of the additional frequency control loop, and simulation experiments are done for different frequency variation conditions. The simulation results show that the proposed frequency control strategies are able to enable DFIG wind turbine have a quick response to the system frequency variation, and participate in the system primary frequency regulation effectively. As a result, the frequency regulation capability of the whole system is improved.