NPC Three-Level Grid-Tied Inverter Bridge Arm Fault Three-Vector Fault-Tolerant Model Predictive Control

To improve the reliability of grid-tied inverters, a three-vector fault-tolerant model predictive control (MPC) strategy is proposed for the issue of Neutral Point Clamped (NPC) three-level grid-tied inverter bridge arm fault. Firstly, three-phase eight-switch fault-tolerant structure is reconfigured by forming a virtual bridge arm after fault. Next, this paper calculates the duration for each voltage vector based on the principle of modulated MPC. These voltage vectors are combined to form a voltage vector combination. A cost function is employed to evaluate all possible combinations of voltage vectors and select the optimal combination. Additionally, the neutral-point voltage balance at DC side is introduced into the fault-tolerant model cost function to reduce the capacitor voltage fluctuation. Finally, simulation results validate the effectiveness of the proposed fault-tolerant control strategy.