In the Japanese National Railways, it is a difficult problem to control an electric power system consisting of both hydraulic and steam power stations that are subject to high load variation rate. Fig. 1 shows the entire block diagram with control system obtained by experiments and theoretical calculations. The author solved this problem, using digital differential analyzer DA-1 which is an accessory of digital electric computer Bendix G-15 D. The block diagram represents a 9th or 10th order differential equation whose characteristic equation has 9 or 10 roots. Results of the analysis with DA-1 are as shown by Figs. 9 to 14, where
f1=frequency deviation (c.p.s.) of hydraulic system to unit step (100MW) load fluctuation
f2=frequency deviation (c.p.s.) of load to unit step (100MW) load fluctuation
f3=frequency deviation (c.p.s.) of steam system to unit step (100MW) load fluctuation
P=local power fluctuation (unit=100MW)
(9) represents 9 roots obtained by Intercom routine of Bendix G-15 D. A pair of roots have a positive real part, which means the generation of unstable oscillation. Fig. 9 shows the gradual increase of amplitudes of the said components. It is believed that in actual system, there are some damping factors such as K≠0 in various parts, so that such oscillation will not be caused. Result of the analysis with analog computer is given by Fig. 15, which shows bigger error than in case by DA-1. The actual phenomena, however, are rather considered more similar to the results by analog computer due to some unknown damping factors. In the result by analog computer, errors are pretty big and yet can not be determined.
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