ALTERNATIVE MODELS OF THE DOUBLY-FED INDUCTION MACHINE FOR POWER SYSTEM DYNAMIC ANALYSIS

The paper focuses on the suitability of alternative models of the doubly-fed induction machine (DFIM) for the study of crowbar action. The quasi-stationary model disregards the fundamental frequency transients in the machine currents and, as a result, can lead to incorrect prediction of the sequence of crowbar actions, whereas the detailed simulation of the entire network is computationally unfeasible. For studies focussing primarily on the influence of the DFIM on the interconnected system, the quasi-stationary model can still be used. For the detailed study of the machine transients, however, the fifth order model with the rest of the network represented by a single-machine operating on an infinite bus is necessary. Simulation results have revealed that the crowbar does not significantly affect the real power output of the machine during fault. However, the effect of the crowbar on the reactive power is more pronounced, particularly the second switching that may take place after fault clearance. This situation can impede the postfault voltage recovery process in the network and has to be considered undesirable from the point of view of the network.