Question

Wind turbine can be used to support the grid frequency. Let us assume, that generator rotates at 1.360 MW power with a rotating speed 12 rpm. How long turbine can provide 2 MW power be decelerating the wind rotor speed, if the allowed speed deviation is 20 %. Assume constant aerodynamic power P = 1,360 MW during the deceleration. Total inertia of wind turbine is 4820000 kgm².

The given aerodynamic power was 1.360 MW. The requested power to the grid is 2 MW. This means, that additional power must be taken from the rotor inertia. The initial rotor speed is 12 rpm and the allowed speed deviation is 20 %.

Approximate, that the torque is behaving linearly during the transient.

(Give the answer of accuracy of at least three significant digits.)

Minimal allowed rotational speed

Answer rpm

Torque at the beginning (speed 12 rpm)

Answer kNm

Torque at the end (speed is minimal allowed rotational speed)

Answer kNm

The aerodynamic torque at the beginning (speed 12 rpm)

Answer kNm

The aerodynamic torque at the end (speed is minimal allowed rotational speed)

Answer kNm

The average torque

Answer kNm

The time to decelerate the rotor from 12 rpm to minimal rotational speed

Answer s

Answer 1