Steady-state response of the wind turbines

I would like to ask you about the steady-state response of the wind turbines. When a wind turbine is operating normally, its transient response at startup, you said in the definition of a 5MW wind turbine (Definition of a 5-MW Reference Wind Turbine for Offshore System Development J. Jonkman, S. Butterfield, W. Musial, and G.Scott. Technical Report, 2009. page 32), is an artifact of computational analysis and needs to be mitigated (this is your suggestion). In this case, how to analyze the dynamic response at startup?
Another question is that when the wind turbine is stopped and idling, the system dynamic responses calculated by the FAST software also has a transient process. Is the transient response also a calculation error (an artifact of computational analysis)?
I am looking forward to your reply.

Dear @HaiYan.Liao,

It looks like you asked a very similar question in a separate forum post: 1.Wind turbine steady-state response. I responded there, requesting clarification on your question.

Best regards,