Can an appropriate gain-scheduling realisation enhance performance?

The choice of realisation for gain-scheduled controllers is demonstrated to have a considerable influence on the performance achieved. An extended local linear equivalence condition is introduced which is of general application. This condition ensures that at evenly operating point (not just the equilibrium operating points) the linearisation of the gain-scheduled controller matches the appropriate member of the family of linear controllers upon which the design is based. This properly may be derived for a wide class of SISO gain-scheduled systems. With regard to the wind turbine application, the gain-scheduled controller satisfying the extended local linear equivalence condition causes a large reduction in the power peaks in comparison to other realisations. This reduction is similar to that achieved by appropriately realised gain-scheduled control in comparison to linear control, thereby illustrating the importance of adopting an appropriate realisation.