Fast model predictive control algorithms for fast-switching modular multilevel converters

For high-power/voltage systems, particularly for high-voltage direct current (HVDC), one of the most potential converter topologies is the modular mutlilevel converter (MMC). Model predictive control (MPC) is one of the switching methods studied in the literature for MMC to simultaneously achieve the three challenging objectives of (1) following the reference of the current waveform requested by upper-level control, (2) mitigating on circulating current, and (3) regulating capacitor voltages of sub-modules. Since the MPC models proposed in the literature suffer from high computation burdens making the algorithm not applicable to high-frequency switching MMCs, a binary integer programming based MPC has been proposed in this paper to optimize this multi-objective problem with minimum computing effort. The main contribution of the algorithms proposed in this paper is to significantly reduce the computation expenses by cutting the searching space from millions of feasible solutions to the incredibly low number of "4", while taking care of the three objectives of MMC control. The performance of the proposed method is evaluated via simulation in MATLAB SimPowerSystems. (C) 2015 Elsevier B.V. All rights reserved.