Method for controlling the operation of a submersible power plant

A method for controlling operation of a submersible power plant, the submersible power plant comprising a structure and a vehicle, the vehicle comprising at least one wing, the vehicle being arranged to be secured to the structure by means of at least one tether;

• the vehicle being arranged to move in a predetermined trajectory by means of a fluid stream passing the vehicle, wherein the vehicle comprises a pitch control system being arranged to change an angle of attack of the at least one wing, the method comprising:
• determining if a speed of the fluid passing the vehicle is higher than a predetermined value,
• if the speed of the fluid passing the vehicle is higher than the predetermined value,
• Ia:
• starting the vehicle by adjusting the angle of attack of the at least one wing to reach operation depth of the vehicle, and initiate movement of the vehicle in a predetermined trajectory starting power generation, and;
• Ib:
• controlling the speed of the vehicle during power generation by adjusting the angle of attack of the at least one wing to optimize power output, and;
• Ic:
• stopping the vehicle by adjusting the angle of attack of the at least one wing such that a lift exerted on the wing by the fluid passing the vehicle is essentially zero, and
• determining if the vehicle has lost power,
• if the vehicle has lost power,
• IVa:
• stopping the vehicle by adjusting the angle of attack of the at least one wing such that the lift exerted by the fluid passing the vehicle is essentially zero,
• IVb:
• determining that power has been restored to the vehicle,
• IVc:
• upon determining that power has been restored to the vehicle, adjusting the angle of attack of the at least wing to initiate movement of the vehicle in the predetermined trajectory starting power generation,
• and;
• if the speed of the fluid passing the vehicle is lower than the predetermined value,
• IIa:
• adjusting the angle of attack of the at least one wing to move to and/or to keep the vehicle in a position that enables the vehicle to start when the speed of the fluid passing the vehicle is determined to be higher than the predetermined value.