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Abstract
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The performance of the excitation system plays a very important role in the voltage stability of the power grid. The brushless excitation system with Brushless AC Exciter offers lower failure rate and thus higher reliability in comparison to the static system with high-rated power electronics converters, brushes and slip-rings. However, its dynamic response is impaired due to exciter lag in producing the required field current. In this paper, the optimal design of an exciter for large-scale power-plant synchronous generator based on the magnetic equivalent circuit method is pursued. The design goals are reducing the overall volume, minimizing the magnitudes of the cogging torque and the field current ripples while satisfying the grid code requirements such as the ceiling values of available field voltage and current, rise time and settling time of the rectified output voltage under dynamic conditions. In addition, the other electrical, magnetic, thermal and mechanical constraints are included in the design algorithm. The proposed design method is used for obtaining the optimal specifications of an exciter for a 25MW, 11kv power-plant generator in order to attain superior characteristics than the existing one. The analytical results are validated using 2D finite-element studies and the experimental measurements.
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