MODELLING AND SIMULATION OF CURRENT TRANSIENTS OF FIXED SPEED AND DOUBLY-FED INDUCTION GENERATOR IN POWER SYSTEM DISTURBANCE CONDITIONS

摘要

The paper deals with the transient behavior of the grid connected Doubly Fed Induction Generator (DFIG) and Self-Excited Induction Generator (SEIG) during grid voltage disturbances. It is shown that, because of such disturbances, the induction generator may be subject to severe electromechanical transients. In the first part, the modeling and power control of the DFIG is achieved by using Park's model and vector control technique. The computation of the transient stator and rotor currents and electromagnetic torque during voltage dips is performed. Simulation results are given for variable depth voltage dips applied to the stator of the DFIG. In the second part, the effect of the crowbar protection is discussed. When the voltage dip appears and the crowbar protection is activated the DFIG behaves as a self-excited induction generator with shorted rotor windings. The disturbance considered in the SEIG operation is a short interruption of the grid voltage. In this case, a laboratory test bench is used to perform the experimental tests. In the third part of this work, an analytical model is developed in order to study the transient currents and torque during grid disturbances. Magnetic saturation is accounted for in the modeling of the induction generator. The simulated and analytical results are compared to those obtained by practical tests.