A model predictive control (MPC) strategy for a three-phase three-level neutral point clamped (NPC) grid-connected inverter is discussed. Conventional two-level inverters are effective when a symmetric fault occurs. But when a three-phase unbalanced fault occurs, they will generate errors and introduce delay in the power system because of the complex design or the neglected negative-sequence component of the grid. To solve this problem, a new method to control a NPC gridconnected inverter is proposed, which combines an MPC strategy with a decoupling double synchronous reference frame phase-locked loop technique. The proposed method reduces the use of PI controllers and enhances the system's response speed. Using simulations and experiments, the proposed MPC strategy for a three-level NPC gridconnected inverter is proven to be accurate and reliable.

<p class="Abstract"><em><span lang="EN-US">T</span></em><span lang="EN-US">his paper proposes a new approach to ensure the torque decoupled to the rotor flux of an induction machine based on the Field Oriented Control (FOC). The suggested method consists of inserting into the conventional d-q synchronous current controller, coupling terms of motor and multi-level inverter models. Making, the dynamic response of stator current components decoupled as well as the rotor flux and torque. In this paper, the mathematic model of an induction motor and multi-level inverter are first derived. Then, the synchronous current controller and modulation strategy for high power inverters are investigated. Finally, the validation through implementation and simulation of a 4.16 kV electric drive with MATLAB/Simulink and SimPowerSystems is performed.  The model simulated in this paper includes an induction motor, nine-level cascaded H-bridge inverter and a carrier based space vector pulse-width-modulation.</span><span lang="EN-US">The results of the simulations of each method has been recorded and the comparison results reveal that the proposed method effectively maintains the rotor flux decoupled to the torque.</span></p>