  A model-based feasible control strategy for multi-rotor systems is presented,
pursuing two control objectives simultaneously: Mechanical loads on the main
tower are to be mitigated, and an externally determined power change is to be
followed to obtain fast power reference response in power systems. For this
purpose, a scalable control strategy consisting of two levels is proposed: The
first level consists of the decentralized control of each rotor unit. By using
an LPV formalism, it is shown how the nonlinearities of the controlled system
are considered in the design using a decentralized wind speed observer of each
rotor to improve the overall closed-loop performance. To mitigate the lateral
loads on the multi-rotor main tower caused by asymmetric rotor thrust forces, a
higher-level controller is introduced. Finally, the applicability of the
controller structure is demonstrated by simulation studies.
