Study on the Connection of DFIG to Grid Based on Double-vector PWM

With the increasing of wind penetration in power systems, many national grid codes demand complete models and simulation studies under different system conditions in order to ensure that the connection of a wind farm would not have a detrimental impact on the grid. It is now recognized that doubly fed induction generators (DFIG) are used in many large farms. A systematic control methodology for connection of wind-turbine-driven DFIGs to the grid is presented in this paper. The purpose is to optimize control and enhance performance doubly fed induction generator wind power system by using double-vector-PWM control. The control strategies of DFIG under vector control in stator flux orientation of rotor side converter and vector control of grid side PWM converter are investigated. A dynamic model of the DFIG wind turbine is derived to develop a vector controller to decouple dynamically active and reactive power control, and keep the DC link voltage stable, and supply low distortion currents both in the machine rotor and the supply grid. The simulations confirm the response of the DFIG independent of speed and dynamic performance of the complete system. The model is suitable to be used in a wind farm and the network under various system disturbances.