Claims:CLAIMS

1. Method for controlling, advantageously coupling to the grid, a hydraulic unit (1) having a synchronous generator (2) intended to be connected to a grid (3) via a circuit breaker (4), a hydraulic turbine (5) provided with a runner (6) mechanically coupled to the rotor of the synchronous generator (2) via a shaft line (9) to drive the synchronous generator (2), and means for adjusting a torque to the shaft line, the method comprises:
a) a step of adjusting, advantageously increasing, the flow of water into the runner (6) from a time t0 to a time t1;
b) a step of closing the circuit breaker (4) at time t1, t1 being a time for which the rotation frequency of the rotor of the synchronous generator, called generator frequency, is equal to the frequency of the grid within a first tolerance interval and the grid phase and the synchronous generator phase are aligned within a second tolerance interval, the method being characterized in that the step a) comprises a sub-step a1) executed from a time t2 to time t1, wherein an adjustment torque, calculated with a controller (7) called adjustment controller, is applied to the shaft line (9) so that, at a time t3, for which the generator frequency enters for the first time within the first tolerance interval, the difference between the synchronous generator phase and the grid phase, is equal to a predetermined value A within a third tolerance interval, time t1 being the nearest time with respect to time t3 for which the grid phase and the synchronous generator phase are aligned within the second tolerance interval.

2. Method according to claim 1, wherein the predetermined value A is in the range [0°, 270°], preferably [0°, 180°], and more preferably [0°, 45°] if the frequency of the grid is above the frequency of the generator, or in the range [-270°, 0°], preferably [-180°, 0°], and more preferably [-45°, 0°] if the frequency of the grid is below the frequency of the generator.

3. Method according to any one of claim 1 or 2, wherein time t2 is a time for which the rotation frequency of the rotor, called intermediate rotation frequency, is below 95%, preferably 80%, more preferably below 70%, of the grid frequency.

4. Method according to any one of claim 1 to 3, wherein the means for adjusting a torque comprise wicket gates.

5. Method according to any one of claims 1 to 4, wherein the adjustment torque comprises an adjustment of the flow of water running into the runner via an actuator, called first actuator (10), the first actuator (10) being controlled by the adjustment controller, and wherein during execution of sub-step a1), the adjustment controller calculates, advantageously in real time, the needed flow of water running into the runner (6).

6. Method according to claim 5, wherein the adjustment controller is communicating with sensors adapted for measuring the generator frequency and the generator phase.

7. Method according to claim 5 or 6, wherein the adjustment controller is further provided with a hydrodynamic based model for the calculation of the needed flow of water running into the runner (6).

8. Method according to claim 7, wherein the hydrodynamic based model is a hydrodynamic analytical model of the hydraulic unit (1) and the feedback loop contains a state estimator, advantageously based on an extended Kalman filter.

9. Method according to claim 5, wherein the adjustment controller controls a second actuator (11) adapted for applying an electrical torque on the rotor of the synchronous generator (2) during sub-step a1).
10. Method according to claim 9, wherein the adjustment controller calculates a theoretical trajectory of frequency rising of the rotor.

11. Method according to claim 10, wherein the second actuator (11) controls the electrical torque in real time so that the frequency rising of the rotor sticks to the theoretical trajectory.

12. Method according to claim 9, wherein the second actuator (11) comprises a variable frequency drive.

13. Method according to claim 9 or 12, wherein the second actuator (11) uses a feedback loop for controlling the electrical torque during sub-step a1).

14. Method according to one of claims 9 to 13, wherein the second actuator (11) is powered by an AC/DC conversion unit coupled with a battery, or a thyristor bridge connected to the grid (3).

15. Computer program for implementing the method according to one of claims 1 to 14.

Dated 22nd day of October 2019

Gopinath Arenur Shankararaj
OF K & S PARTNERS
AGENT FOR THE APPLICANT(S)
IN/PA-1852
, Description: