Method for starting a hydraulic turbine

A method for controlling a hydraulic unit having a synchronous generator to be connected to a grid via a circuit breaker, a hydraulic turbine provided with a runner mechanically coupled to the rotor of the synchronous generator via a shaft line to drive the synchronous generator, and means for adjusting a torque to the shaft line, the method comprises:

• a) a step of adjusting a flow of water into the runner from a time t0 to a time t1;
• wherein t1 is a time at which rotation speed of the rotor of the synchronous generator is equal to synchronous speed within a first tolerance interval and a grid phase and a synchronous generator phase are aligned within a second tolerance interval,
• b) the time interval from to t0 time t1 comprising a sub-interval from a time t2 to time t1, with t0<=t2<=t3<t1, wherein during the sub-interval a sub-step is executed that comprises applying an adjustment torque, calculated with an adjustment controller, to the shaft line via a first actuator that controls the flow of water into the runner and a second actuator coupled to a stator of the synchronous generator, wherein:
• (1) during the sub-step, adjustment of the generator rotation speed and the synchronous generator phase occurs in parallel via simultaneous control of the first and second actuators;
• (2) at time t3, the generator rotation speed enters for the first time within the first tolerance interval;
• (3) at time t3, a difference between the synchronous generator phase and the grid phase is brought to a predetermined value A within a third tolerance interval;
• and
• (4) time t1 is the nearest time after t3 for which the grid phase and the synchronous generator phase are aligned within the second tolerance interval;
• c) closing the circuit breaker at time t1.