Constrained Long-Horizon Direct Model Predictive Control for Grid-Connected Converters with LCL Filters

This paper presents a direct model predictive control algorithm for a three-level neutral point clamped converter connected to the grid via an LCL filter. The proposed controller simultaneously controls the grid and converter currents as well as the filter capacitor voltage, while meeting the relevant grid standards. Moreover, output constraints are included to ensure operation of the system within its safe operating limits. This is achieved by formulating the direct MPC problem as a constrained integer least-squares optimization problem, wherein the output constraints are mapped into input constraints. The presented results verify the effectiveness of the proposed method.