Long-Horizon Direct Model Predictive Control: Modified Sphere Decoding for Transient Operation

Karamanakos, P; Geyer, T; Aguilera, RP

Long-Horizon Direct Model Predictive Control: Modified Sphere Decoding for Transient Operation

Karamanakos, P Geyer, T Aguilera, RP

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Publication Type:: Journal Article
Citation:: IEEE Transactions on Industry Applications, 2018, 54 (6), pp. 6060 - 6070
Issue Date:: 2018-11-01

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Field	Value	Language
dc.contributor.author	Karamanakos, P	en_US
dc.contributor.author	Geyer, T	en_US
dc.contributor.author	Aguilera, RP https://orcid.org/0000-0003-4166-8341	en_US
dc.date.issued	2018-11-01	en_US
dc.identifier.citation	IEEE Transactions on Industry Applications, 2018, 54 (6), pp. 6060 - 6070	en_US
dc.identifier.issn	0093-9994	en_US
dc.identifier.uri	http://hdl.handle.net/10453/132128
dc.description.abstract	© 1972-2012 IEEE. In this paper, we present modifications to the sphere decoder initially introduced in the work of Geyer and Quevedo and modified in the work of Karamanakos et al. that significantly reduce the computation times during transients. The relative position of the unconstrained solution of the integer quadratic program underlying model predictive control (MPC) with respect to the convex hull of the (truncated) lattice of integer points is examined. If it is found that the unconstrained solution does not lie within the convex hull - a phenomenon that is observed mostly during transients - then a projection is performed onto the convex hull. By doing so, a new sphere that guarantees feasibility and includes a significant smaller number of candidate solutions is computed. This reduces the computation time by up to three orders of magnitude when solving the optimization problem at hand. Nonetheless, the reduction of the computational burden comes at a cost of (mild) suboptimal results. The effectiveness of the proposed algorithm is tested with a variable speed drive system consisting of a three-level neutral point clamped voltage source inverter and a medium-voltage induction machine. Based on the presented results, the sphere decoding algorithm with the proposed refinements maintains the very fast transient responses inherent to direct MPC. Moreover, it is observed that the occasional implementation of suboptimal solutions does not lead to a deterioration of the system performance.	en_US
dc.relation.ispartof	IEEE Transactions on Industry Applications	en_US
dc.relation.isbasedon	10.1109/TIA.2018.2850336	en_US
dc.rights	info:eu-repo/semantics/closedAccess
dc.title	Long-Horizon Direct Model Predictive Control: Modified Sphere Decoding for Transient Operation	en_US
dc.type	Journal Article
utslib.citation.volume	6	en_US
utslib.citation.volume	54	en_US
utslib.for	0906 Electrical and Electronic Engineering	en_US
utslib.for	0803 Computer Software	en_US
utslib.for	08 Information and Computing Sciences	en_US
utslib.for	09 Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Electrical and Data Engineering
utslib.copyright.status	closed_access	*
pubs.issue	6	en_US
pubs.publication-status	Published	en_US
pubs.volume	54	en_US

Abstract:

© 1972-2012 IEEE. In this paper, we present modifications to the sphere decoder initially introduced in the work of Geyer and Quevedo and modified in the work of Karamanakos et al. that significantly reduce the computation times during transients. The relative position of the unconstrained solution of the integer quadratic program underlying model predictive control (MPC) with respect to the convex hull of the (truncated) lattice of integer points is examined. If it is found that the unconstrained solution does not lie within the convex hull - a phenomenon that is observed mostly during transients - then a projection is performed onto the convex hull. By doing so, a new sphere that guarantees feasibility and includes a significant smaller number of candidate solutions is computed. This reduces the computation time by up to three orders of magnitude when solving the optimization problem at hand. Nonetheless, the reduction of the computational burden comes at a cost of (mild) suboptimal results. The effectiveness of the proposed algorithm is tested with a variable speed drive system consisting of a three-level neutral point clamped voltage source inverter and a medium-voltage induction machine. Based on the presented results, the sphere decoding algorithm with the proposed refinements maintains the very fast transient responses inherent to direct MPC. Moreover, it is observed that the occasional implementation of suboptimal solutions does not lead to a deterioration of the system performance.

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http://hdl.handle.net/10453/132128