Performance of a computer-based two-phase excitation system for a variable-speed dual-excited synchronous generator

A computer-based two-phase excitation system for a variable-speed dual-excited synchronous generator (DESG) has been implemented. The excitation system has an automatic frequency regulation (AFR) scheme and an automatic voltage regulation (AVR) scheme. The two regulation schemes act on the excitation currents independently to enable the DESG to supply power at constant frequency and constant terminal voltage while its rotor is driven at a variable speed. The authors describe the implementation of the excitation system and its performance when the AFR scheme is set to the AUTO control mode and the AVR scheme is set to the MANUAL control mode. Real-time results are presented showing the performance of the AFR scheme when the DESG is operating under different system disturbances for an operational slip range of +or- 10%. The results show that the excitation system is flexible, fast acting, and accurate. The steady-state error in the regulated output frequency is much less than 0.1%.