Naslov
Set-theoretic control of a wind turbine

Autori
Hure, Nikola

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Faculty of Electrical Engineering and Computing

Mjesto
Zagreb

Datum
23.11

Godina
2017

Stranica
223

Mentor
Vašak, Mario

Ključne riječi
set-theoretic control methods, discrete-time systems, hybrid systems, nonlinear systems, constraints, scalability, invariant set, operating envelope protection, approximate constrained time-optimal control, piecewise affine model identification, one-step set computation, one-step set appro-ximation, clustering-based polyhedron over-approximation, wind turbine, unscented Kalman filter, overspeed protection, overload protection, utility-scale wind turbine experiments, aero-elastic simulations

Sažetak
This thesis discusses the set-theoretic methods for control of high-order systems. Specifically, focus of the thesis is given on the operating envelope protection and constrained time-optimal control design in the algebra of polyhedral sets, whereas the utility-scale wind turbine is used to validate the proposed algorithms. Generally, set-theoretic control design for high-order systems suffers from the computational intractability which is related to the complexity of the specific operations between the sets. Algorithms that are proposed in this dissertation alleviate those shortcomings at the expense of suboptimality. The developed set-theoretic methods are completely executed offline, whereas the computational cost for the on-line operation of the resulting control law is reduced to a minimum. Thus, a hard real-time claims can be posed, which is an important property for the technical systems with high safety requirements. Technical systems are often restrained in their operating region, whereas for their safe operation and reliability given constraints should be respected. It is well known that the operating envelope protection of a dynamical system with an additive and bounded uncertainty can be achieved by construction of corresponding robust control invariant set. Invariant set-based framework can include the uncertainties of the model and system state estimation in the design process. To this aim, the operating envelope protection system design for nonlinear discrete-time systems is proposed in this thesis. The method employs a suitably defined linear model with additive uncertainty confined in a finite set in order to construct the invariant set-based protection system. In that regard, an approximate method is proposed to derive the suboptimal solution to the corresponding robust control invariant set design problem. The proposed method is validated in both simulation and real experiment on the utility-scale wind turbine in the overspeed and structural overload protection case study. Part of the thesis is dedicated to the identification and control of hybrid systems. Thus, thesis includes generalisation of the clustering-based method for a piecewise affine model identification of multiple-input single-output processes to identification of multiple-input multiple-output piecewise affine models. The respective approach can be used to obtain simpler models compared to the state of the art and thus also leads to the simpler problems for the set-theoretic control design. Moreover, the approach to approximate constrained time-optimal control is presented. It can be used to enable scalability of the method to high-order systems. The proposed approach is validated on aero-elastic simulations of a utility-scale wind turbine.

Izvorni jezik
Engleski

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