I have been using the NREL offshore 5-MW baseline wind turbine model. When I increased the generator-torque constant in region 2(K) slightly, for example, from 0.025576386 to 0.027, the generator torque is shown in the attachment picture. By the way, the wind speed is constant(8 m/s) and I removed the torque rate limiter and saturation blocks.
I would like to ask why such a slight increase of K would cause such fluctuation of generator torque?
Dear Xin Tong,
Your plot shows that the torque drops quickly and settles at around 20 kNm. If you look at Figure 7-2 (torque-speed curve) of the NREL 5-MW specifications report (nrel.gov/docs/fy09osti/38060.pdf), you’ll see that the transition from Region 1 1/2 to 2 is at around 20 kNm. My guess is that you changed the torque constant in Region 2 without changing the torque in Region 1 1/2, resulting in a jump in torque at the transition speed (871 rpm). This jump in torque will cause the torque oscillations you are seeing in your plot.
Best regards,