This study is aimed at predicting steady-state and dynamic responses after a sudden load shed for the TFTR motor-generator (MG) system. In the paper, a discussion on the methods, assumptions, and validation of the MG computer model is presented. The model includes the salient pole features (using two-axis theory) and effects of saturation. The steady-state model describing MG performance under normal conditions ignores the changes in flux linkage of windings other than the field winding. This simplification reduces the complexity of the model, yet it still describes the regular pulses of the TFTR generator satisfactorily. Only the field relation is described by the differential equation, and the rest are algebraic. The dynamic response of load shed-a special case in dynamic study-can be of importance in predicting the behavior of the MG system associated with the severe overvoltage problem. More elaborate synchronous generator models are required in this case. Not only the field winding voltage relation, but also the damper winding voltage relation must be described by differential equations. The complete solution can be obtained by means of the Laplace transform. Validation of the MG computer model has been performed by comparison with actual MG load scenarios recorded on electronic digitizers for TFTR shots. The simulation results are comparable to the recorded MG performance data.
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