Browsing by Author "Sadie, Adriaan"

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    Model predictive control with space-vector modulation for a grid-connected converter with an LCL-Filter
    (Stellenbosch : Stellenbosch University, 2020-03) Sadie, Adriaan; Mouton, H. du T.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: This thesis presents an indirect model predictive control (MPC) strategy with spacevector modulation (SVM). The controller is used to control a high-power voltage-source inverter (VSI), connected to the grid via an LCL-filter. The controller evaluates a multivariable and convex cost function over a long prediction horizon in order to determine an optimal sequence of references for a space-vector modulator. The MPC strategy is tested in a Matlab simulation. The results of the simulation show excellent steadystate behaviour as well as a fast response during transients. The controller successfully dampens the resonant frequency of the filter and exhibits low grid-current harmonic distortion. The controller is then tested by means of a hardware-in-the-loop (HiL) simulation to verify the functionality of the controller on a field-programmable gate array (FPGA) device. The VHDL (Very high-speed integrated circuit Hardware Description Language) design of the controller is discussed in detail, where emphasis is put on the FPGA resource and time usage. To confirm the efficacy of the design of the controller, the HiL results are compared to Matlab equivalent simulation results. The signals from the HiL compare well to the Matlab results, with only a slight offset, due to differences in the PWM pulses produced by the FPGA-based controller. The controller is able to function in real-time on the FPGA. An alternative small-signal linear quadratic regulator (LQR) controller is also investigated in this thesis. The controller is first tested by means of a Matlab based simulation, which shows excellent steady-state behaviour with low Total Harmonic Distortion (THD) and fast settling time during transients. The controller is also implemented on an FPGA and tested by means of a HiL simulation. The results of the HiL and the Matlab signals are compared, and the LQR controller is able to function in real-time on the FPGA.