Dynamic Behaviour of a Doubly Fed Induction Machine with Generator-side Converter under Abnormal Condition

This paper describes the dynamic behaviour of a doubly-fed induction machine, operating with wind turbine. The rotor circuit of the machine consists only of a generator-side converter working under abnormal condition at stator side (fault condition and voltage drop take place in transmission lines of the grid system). The induction machine model is based on the stationary reference frame and the control-unit model is based on the line-voltage oriented reference frame. The generator-side controller provides good decoupling between active and reactive power. A powerful MATLAB/SIMULINK was used for the simulation of the wind energy conversion system of a 4 kW wind generator. The simulation results of the generator side converter show that the speed, torque and the φ sin (power factor) can be regulated independently to match the reference signals. The effects of assumed abnormal condition in the grid system are discussed with regard to stator current and rotor current of the induction machine. The results indicate that during a fault condition the inverter should be disconnected in order to reduce the high oscillation in stator currents and rotor currents. In the case of a voltage drop, it indicates that the inverter should be automatically disconnected with a protective relay.