Dear Jason,

I am confusing about a state that was included in the OpenFAST linearization. There is a DOF called the Variable speed generator DOF (internal DOF index = DOF_GeAz). Intuitively, this is the generator’s angular position, so its derivative should be the generator speed. However, for the linearization at a specific operating point (OP), I found that the OP of the derivative of the Variable speed generator DOF (internal DOF index = DOF_GeAz) always equals the value of the rotor speed OP. Does this mean this DOF is the rotor azimuth and its derivative is the rotor speed? If so, how about their corresponding derivatives in the Matric A and C? This may be induced by a possible mistake that I made, so I attached a *.Lin file for your reference.

LinearizationOutputSampleABCD.lin.txt (46.4 KB)

Thank you!

Xianping