Water level regulating system

A water level regulating system controlling water levels of head tanks of a plurality of hydroelectric plants installed in cascade along a stream, each of said hydroelectric plants including a hydraulic turbine, guide vanes controlling a discharge flowing through the hydraulic turbine, and a water level regulator which regulates the water level of the head tank as a controlled variable by controlling an opening of the guide vanes as a manipulated variable, said water level regulator of an upstream hydroelectric plant comprising:

• means for varying a reference water level of the head tank of the upstream hydroelectric plant in accordance with the opening of the guide vanes of the upstream hydroelectric plant to produce a set water level of the head tank of the upstream hydroelectric plant;
• a summing point producing a difference between the set water level and an actual water level of the head tank of the upstream hydroelectric plant as an actuating signal;
• a compensator compensating the actuating signal using controlling parameters, and outputting the compensated signal as a first manipulated signal which is supplied to the guide vanes of the upstream hydroelectric plant as the manipulated variable;
• means for varying the controlling parameters of said compensator in accordance with the opening of the guide vanes of the upstream hydroelectric plant;
• and
• means for supplying the first manipulated signal to the water level regulator of a downstream hydroelectric plant as a feedforward signal;
• said water level regulator of the downstream hydroelectric plant comprising:
• means for varying a reference water level of the head tank of the downstream hydroelectric plant in accordance with the opening of the guide vanes of the downstream hydroelectric plant to produce a set water level of the head tank of the downstream hydroelectric plant;
• a summing point producing a difference between the set water level and an actual water level of the head tank of the downstream hydroelectric plant as an actuating signal;
• a compensator compensating the actuating signal using controlling parameters, and outputting the compensated signal as a second manipulated signal;
• means for varying the controlling parameters of said compensator in accordance with the opening of the guide vanes of the downstream hydroelectric plant;
• and
• means for correcting the second manipulated signal using the feedforward signal supplied from the upstream hydroelectric plant and supplying the corrected signal to the guide vanes of the downstream hydroelectric plant as the manipulated variable.