The 2 1/2 degrees of freedom structure considered has been used in real applications for many years but it has not been shown to follow from the solution of an H2 optimal control problem. A Kucera type of polynomial solution is presented which provides a theoretical basis for the structure adopted. The proposed controller structure has the advantage that low frequency tracking properties can be achieved, as in single degree-of-freedom designs but no constraints then apply to the high frequency tracking behaviour, since it is effectively determined by a two degrees-of-freedom structure. A wind turbine example is presented.