| With the scale of power system larger and larger, the whole power system gets more and more complicated, and operation safety and stability of machines and grid become very important. Large generating units will be subject to the impact of various special operation and faults. It has very important theoretical value and practical meaning in engineering to make deep calculation and analysis on the transient behaviour of power system under disturbances. Systematic analysis for transient processes of machines and grid involves grid equations, electric machine equations, mechanical equations of shaft system, which is complicated. Taking two typical disturbances as three phase sudden short circuit and out-of-phase synchronization as examples, the dissertation has a study on transient behaviour of machines and grid under disturbances. By the method of alternating field, imposing pulsation MMF on direct and quadriture axis respectively, parameters of direct and quadriture axis are calculated. On this basis, by software SIMSEN, digital model of machines and grid for transient analysis is set up, where the modules like infinite bus, transformer, generator, excitation system are taken into account completely. In such a way, the processes of sudden short circuits in the terminals for no load and load conditions, and out-of-phase synchronization are analyzed. The work includes the computation on 2D electromagnetic field of a 650MW turbogenerator and its steady and transient parameters. Simulations on various no load and load short circuits in machines terminals, as well as the transient processes of out-of-phase synchronizations with different phase angles are made. Curves of mechanical and electrical variables with time are obtained. Comparison between calculation and test is made. Calculation and analysis show that, in the cases of out-of-phase synchronization, the electromagnetic torque is largest at closing phase angle of 120o, and the current is largest at closing phase angle of 180o.
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