An Indirect Model Predictive Control Method for Grid-Connected Three-Level Neutral Point Clamped Converters With $LCL$ Filters
Mattia Rossi, Πέτρος Καραμανάκος, Francesco Castelli Dezza
Abstract
This article presents a model predictive control (MPC) algorithm for a three-level neutral point clamped converter connected to the grid via an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter. The proposed long-horizon MPC method, formulated as a multicriterion quadratic program (QP), simultaneously controls the grid and converter current as well as the filter capacitor voltage, while meeting the relevant grid standards. To achieve the latter, a carrier-based pulsewidth modulation stage is employed. Finally, soft constraints are included to ensure operation of the system within its safe operating limits, particularly with regards to a potential overcurrent or overvoltage trip during transient operation. The presented simulation results based on a medium-voltage system as well as experimental studies based on a scaled-down prototype verify the effectiveness of the proposed method.