Browsing by Author "Raath, Johannes Hendrik"

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    Alternative sphere decoding for finite control set model predictive control of power electronic converters
    (Stellenbosch : Stellenbosch University, 2021-03) Raath, Johannes Hendrik; Mouton, Toit; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The rapid advance in computational power over the past decade has enabled model predictive control (MPC) to emerge as a promising alternative control technique for fast reacting power electronic applications. Trending in the power electronic system eld is - nite control set MPC, whereby a single multiple-input multiple-output (MIMO) controller can be realised to replace complicated PI control loops and deliver control signals for direct application to the converter. As an extension of basic MPC, long-horizon MPC refers to the evaluation of the optimisation criterion over a prediction horizon of more than one. Long-horizon MPC is desirable for its enhanced closed-loop performance during steadystate operation. Unfortunately, long-horizon MPC requires more computations to nd the optimum control action, especially in FCS-MPC, as the computational burden increases exponentially with an extension of the prediction horizon. The computational burden associated with long-horizon MPC can be reduced through mathematical programming where the underlying MPC problem is re-formulated as an integer least-squares problem. With regard to power electronic systems in particular, a recent adaptation of the Sphere Decoding Algorithm (SDA) has emerged as a very popular choice for solving or decoding of the ILS problem. The main objective of this thesis is to devise an alternative decoding strategy that will solve the ILS problem relating to long-horizon FCS-MPC for multi-level inverters. Exponential space algorithms are investigated and matched to an appropriate power electronic application. From the investigation, a novel preconditioning algorithm or projection algorithm evolved. Characteristics that favour modern processing technology are captured and applied to the well-acclaimed SDA to propose a decoding approach that involves matrix calculations. This also permits the e cient precomputation and storage of system matrices o ine for online use. The proposed algorithms are incorporated into a predictive controller for a power electronic drive and are evaluated in real time.