Method for stabilizing the rotation speed of a hydraulic machine with S-characteristics and installation for converting hydraulic energy into electrical energy

1. A method for stabilizing a rotation speed of a hydraulic machine with S-shaped characteristic curves so that the hydraulic machine is configured for coupling to a grid, the hydraulic machine including a runner and a distributor that is arranged around the runner and that includes a plurality of movable guide vanes, the method comprising:

calculating a target net head and a target opening to affect the guide vanes of the hydraulic machine, the target net head and the target opening being calculated so that a torque exerted by a water flow on the runner of the hydraulic machine is null and that the hydraulic machine rotates at a target rotation speed based on a grid frequency;

determining a real net head to which the hydraulic machine is subjected;

comparing the target net head with the real net head;

measuring a real rotation speed of the hydraulic machine;

comparing the real rotation speed with the target rotation speed; and

adjusting the opening of the guide vanes so as to reduce a speed difference between the target rotation speed and the real rotation speed, converge towards the target opening, and reduce a height difference between the target net head and the real net head.

2. The method according to claim 1 , wherein the opening of the guide vanes is adjusted by calculating a set point opening to affect the guide vanes.

3. The method according to claim 2 , wherein the set point opening is calculated by summing up the target opening with a first opening variation depending on the height difference between target net head and real net head and with a second opening variation depending on the speed difference between target rotation speed and real rotation speed.

4. The method according to claim 3 , wherein the first opening variation is outputted by a first corrector module, having as an input the height difference between target net head and real net head.

5. The method according to claim 4 , wherein the first corrector module is a proportional derivative corrector.

6. The method according to claim 3 , wherein the second opening variation is outputted by a second corrector module, having as input the speed difference between the target rotation speed and the real rotation speed.

7. The method according to claim 6 , wherein the second corrector module is a proportional integrative corrector.

8. An installation for converting hydraulic energy into electrical energy, comprising:

a machine having a runner; and

a distributor arranged around the runner and including a plurality of adjustable guide vanes, wherein the distributor is configured to determine a real net head of the installation;

wherein the installation is configured to:

calculate a target net head and a target opening to affect the guide vanes of the machine, the target net head in the target opening being calculated so that a torque exerted by a water flow on the runner of the machine is null and that the machine rotates at a target rotation speed based on a grid frequency,

compare a target net head with a real net head to which the machine is subjected,

calculate the target rotation speed of the machine,

measure a real rotation speed of the machine,

compare the real rotation speed with the target rotation speed, and

adjust the opening of the guide vanes so as to reduce a speed difference between target rotation speed and real rotation speed converge towards the target opening, and reduce a height difference between the target net head in the real net head.