Model Predictive Current Control for Fault-Tolerant Bidirectional Voltage Source Converter With Open Circuit Fault and Unbalanced Grid Voltage

To improve the fault-tolerant operation capability of bidirectional voltage source converter (BVSC), an improved model predictive current control (IMPCC) for fault-tolerant BVSC, is proposed with balanced DC-link capacitor voltage under unbalanced grid voltage. The proposed method can maintain continuous operation even if power device faults and unbalanced grid voltage faults occur together. A current predictive model of the fault-tolerant BVSC is established. By using grid voltages and 90° lagging signals in the αβ stationary coordinate system, the reference current calculation method is designed for BVSC to eliminate power ripple under unbalanced grid voltage, which can avoid the complex positive and negative sequence extraction. DC-link split capacitor voltage balancing is achieved by the improved cost function. Based on the current predictive model and improved cost function, the optimal space voltage vectors are selected for fault-tolerant BVSC. Compared to the existing predictive methods, the proposed IMPCC can balance DC-link capacitor voltage and eliminate the power ripples for fault-tolerant BVSC under unbalanced grid with simple implementation. The experimental results validate the effectiveness of the proposed control scheme.