Dear Cheng,
Mitigating platform motion and regulating power likely require different pitch-angle commands. Normally the mean pitch angle at a given mean wind speed will be determined such that rated torque and speed are maintained. Mitigating platform motion likely requires reduced pitch-control gains or pitch and torque oscillations about their mean values. Please consult the literature on floating offshore wind control e.g. as discussed recently in the following forum topic: Negative Damping - FOWT.
Best regards,