PROJECT TITLE :

Dual-Loop Control Strategy for DFIG-Based Wind Turbines Under Grid Voltage Disturbances

ABSTRACT:

For a multimegawatts doubly-fed induction generator (DFIG), the grid voltage disturbances could affect the stator flux and induce the transient stator flux, thanks to the direct affiliation of the stator and therefore the grid. The buildup of the transient stator flux caused by the variations of the stator voltage may introduce harmful power and torque oscillations to the DFIG, and even lead to rotor overcurrent. For the standard field-oriented vector control strategy, the planning of the controller is predicated on the steady-state model of the DFIG, that neglects the dynamic of the stator flux, and, thus, it cannot work well during the transient state to decay the transient flux and to suppress the flux accumulation. In this paper, a dual-loop management strategy, that includes the standard current loop and an additional flux loop, is proposed to not only control the active and reactive power, but conjointly decay the stator transient flux, and avoid the buildup of the stator transient flux. Moreover, the proposed strategy will acquire nearly constant stator active power and electromagnetic torque, which could prolong the lifetime of the drive train. A case study on a typical a pair of-MW DFIG-primarily based wind turbine demonstrating the effectiveness of the proposed control strategies is verified with simulations in MATLAB/Simulink. The proposed control strategies also are experimentally validated employing a scaled-down seven.five-kW DFIG. The simulation and experimental results clearly validate the effectiveness and feasibility of the proposed strategy, and show the improved dynamic performances of the DFIG.