Variable-pitch power regulation of tethered-wing systems based on robust gain-scheduling H-infinity control

Abstract

In this paper, we address the power regulation of tethered-wing systems and illustrate the benefits of employing variable-pitch control to alleviate dynamic mechanical loads and power fluctuations. The proposed control scheme is based on a strategy to maximize the generated power during low-speed wind and prevent force and power overloads during the high-speed wind. To implement this strategy, we employ a tether reeling-speed controller to maintain optimal generator speed in low-speed winds, and a MIMO speed-force controller to prevent power surges in high-speed winds. Additionally, the minimization of the wing’s pitch angle activity during high-speed wind is considered as another control objective in the proposed scheme. The controllers are synthesized using H∞ method and are made robust with respect to the system’s dynamic and parametric uncertainties. The synthesis procedure is predicated on a linear parameter varying (LPV) expression of the dynamics of the system. The effectiveness of the strategy and the performance of the controllers are showcased through simulations conducted with a comprehensive 3-dimensional simulator for tethered-wing systems.