Abstract: A method for stabilizing the rotation speed of a machine with S-characteristics is provided. The method includes calculating a target net head and a target opening to affect guide vanes of the machine, the target net head and the target opening being calculated so that the torque exerted by water flow on the turbine is null and that the machine rotates at a target rotation speed; determining a real net head to which the machine is subjected; comparing the target net head with the real net head; and adjusting the opening of the guide vanes so as to converge towards the target opening and reduce a height difference between the target net head and the real net head.

Abstract: This method allows determining the operating point of a hydraulic machine in a considered operating range, such as turbine mode, and comprises steps that consist in a) determining two coordinates (N?11, T?11) of a first series of potential operating points of the hydraulic machine for the orientation affected to guide vanes of the machine, b) measuring the rotation speed of the machine, and c) determining the torque exerted by water flow on the machine. The method further includes steps consisting in d) calculating two coordinates (N11, T11) of a second series of potential operating points of the machine in function of the rotation speed (N) measured at step b) and the torque determined at step c), and e) deducing the two coordinates (N11_real, T11_real) of operating point that belongs both to the first and the second series in the said considered operating range of the machine.