Transient Behavior Analysis of Induction Generator at Three-Phase Fault Condition

In recent years, renewable energy generation has been coming up for effective use of natural energy, such as wind energy. Induction generators consisting squirrel-cage rotors are widely used as wind generators because of their salient features like robust rotor design, simplicity in the construction, maintenance free operation, etc. In this paper, it is derived that the transient current, electromechanical torque, and active power taking into account rotor speed change of induction generators at three-phase fault conditions. The output equations of the induction generator has nonlinearity, and the speed-time characteristic in a fault period is also expressed by the nonlinear equation. The approximation to derive analytical formulas for transient conditions is proposed, and the transient behavior of the induction generator is analyzed by the developed equations. The simulation block diagram in MATLAB/SIMULINK is constituted using the system equation in consideration of the nonlinearity of the induction generator. The simulation results obtained from each theoretical analysis are in close agreement with that of results obtained using MATLAB/SIMULINK simulation. Furthermore, theoretical discussion also developed to determine the fault phase angle and the time at which maximum transient currents flow in the system.