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A synchronous generator model for the U.B.C. electromagnetic transients program Martinich, Terrence Gordon

Abstract

In recent years, problems have arisen with electro-mechanical interaction in turbine-generator units in power systems. This torsional interaction between the mechanical shaft system and electrical system occurs in the subsynchronous resonance phenomenon, that may arise in series compensated transmission lines, and in faulty synchronization. Shaft torques caused by these disturbances may be sufficiently severe as to damage or destroy the turbine-generator shaft. Therefore, to study these cases, there was a need to represent generators in digital computer transients programs in more detail than as simple voltage sources behind reactances. Addition of a synchronous generator model to the U.B.C. Transients Program is described. The model of the generator represents both the electrical and shaft torsional dynamics and possesses a large degree of generality. The model assumes constant excitation and no magnetic saturation of the iron in the machine. Interface to the Transients Program is through a three-phase Thevenin equivalent circuit of the external electric network as seen from the generator terminals. Trapezoidal rule implicit integration is applied to the machine equations followed by use of Newton's method to solve the resulting nonlinear algebraic equations. Test cases are presented to verify the new solution technique, followed by examples of possible applications of the synchronous machine model. In a study of faulty synchronizations of an unloaded generator, conclusions were in agreement with the findings of a manufacturer.

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