If the capacitance C of the series capacitor is chosen based on the following equation:

then series resonance occurs and the voltage in the output terminal and that in the imaginary terminal μ becomes the same, suppressing the voltage increase.

Fig. 11 gives the characteristics of V_d and V_sc0 versus output power P_out for the tested system with duplex reactor (type A) when a set of capacitors was inserted between the output terminal of the duplex reactor and the load. In this case, C of 550 μF (X_c=5.79Ω) was used for the duplex reactor having X_γ = 5.31Ω. From the figure it is clarified that the increases in V_d and V_sc0 can be compensated with the capacitor. In Fig. 12 an example of output voltage waveform is shown for the case of the system with the capacitors. It is seen that almost no distortion in the output terminal voltage waveform was obtained even when the capacitor was connected.

　

Fig. 12 Output Terminal Voltage Waveforms when Capacitors are Connected.

　

7. CONCLUSIONS

　

In this paper, novel and simple circuit configurations have been proposed to realize a shaft generator system without output voltage distortion, and steady-state characteristics of the system have been investigated.

　

The following have been concluded from the discussion:

(1) A satisfactory harmonics elimination in output voltage waveform is achieved by canceling out the subtransient inductance of the synchronous compensator with duplex reactor.

(2) A set of steady-state equations for the proposed system has been derived, and the idea of designing the duplex reactor has been clarified.

(3) The steady-state characteristics have been discussed, and it has been clarified that THD of output voltage can be adjusted with the inductances of the duplex reactor, and that the dc link voltage and the synchronous compensator terminal voltage increase with an increase in the output power when the output terminal voltage is kept constant.

(4) To suppress the voltage increases of the system a simple method using capacitors has been proposed. It has been clarified that the increase in the voltages is suppressed greatly with this method.

　

The transient performances of the proposed shaft generator system will be reported at the earliest opportunity.

　

Acknowledgements

　

We express our sincere thanks to personnel from Gifu Works, Taiyo Denki Co., Ltd. for cooperating in this study. Also, some of these studies have been done with the help of Grant-in-Aid for Scientific Research of the Ministry of Education, Science, Sports and Culture, Japan, and the Research Institute for Technology of Tokyo Denki University.

　

References

　

[l] H. Gundlach "Statrc frequency converters for shaft generator systems," The Institute of Marine Engineers, London, UK, January 1972

[2] J. Nishiyama. H. Kotera. T. Kishimoto. M. Yamaji and M. Tsuji, "Shaft driven AC generator for fixed pitch propeller," Journal of the M. E. S. J., Vol. 13, no. 6, pp. 442-449, June 1978

[3] S. Nishikata, A. Odaka, Y. Koishikawa, and T. Kataoka

"Performance analysis of shaft generator systems,"

Trans. IEE of Japan, Vol. 118-D, No. 10, pp. 1209-1216. October 1998

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