Model predictive control of modular multilevel converter with reduced computational load

Abstract

Modular Multilevel Converter (MMC) is a promising topology for high voltage/power AC/DC and DC/AC applications. Model Predictive Control (MPC) is an advanced and simple method for power converters control. However, its computational load becomes unacceptable when MMC voltage level increases. An improved MPC for MMC is proposed in the paper. The submodule capacitor voltages are sorted according to the leg current polarity, the proposed MPC decreased the number of the possible actuations in each phase from C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2N</sub> to N+1 for N+1 level MMC. The proposed MPC is verified and evaluated by a MMC-based STATCOM in PSCAD/EMTDC. The results show fast and accurate tracking in reactive current reference. The total DC voltage variation is limited below 1% during the 1.75 cycles transient.