Automatic Frequency Control of an Isolated Small Hydro Power Plant

The paper presents a new technique of automatic frequency control of an isolated small hydro power plant. Presently surplus generation due to decrease in load is dissipated in a dump load. But surplus water can be used for irrigation which is the primary requirement of the local community for their survival at large number of locations. It is being wasted in the dump load and the new scheme proposed in this paper eliminates the dump load, while the input power of the hydro plant is controlled by an on/off and a servo controlled valves. The on/off control linearly raises or lowers the generation by 30%, while the servo motor controls the generation to the required extent. It is shown that the rate of opening or closing of the on/off control valve has considerable effect on the transient response of the system. Finally, the dynamic responses due to step disturbance for different nominal loadings of the system, gain settings, rate of closing/opening of the on/off control valve are also presented.