Analysis of wind turbine driven double-output induction generator under abnormal condition of the grid

This paper describes the study undertaken to assess the steady state and dynamic behavior of a double-output induction generator (DOIG) driven by wind turbine after its disconnection from the grid. The machine model is based on the stationary reference frame with vectorized dynamic model and control unit is based on the line-voltage oriented reference frame. The machine side converter provides good decoupling between the active and reactive power and the network side converter controls the power flow between the DC bus and the AC side and allows the system to be operated in sub-synchronous and super synchronous speed. The induction machine runs at a specific speed with the stator disconnected from the grid (Is=0), the rotor is suddenly excited with slip-frequency voltages derived from voltage regulators so as to produce commended open-circuit stator terminal voltage. Behavior under varying input power typically observed in wind turbines is also reported. A MATLAB computer simulation study was undertaken and results on 1.5 kW wind turbine are presented indicating grid abnormalities and varying input power.