Reliability Improvement of a 3-Level T-Type Grid-connected Inverter With Dual Vector Modulation Model Predictive Fault-tolerant Control Strategy

Abstract

In this paper, a new 3-Level T-type Inverter(3LT2I) fault-tolerance topology is proposed for the power device failure due to grid voltage fluctuations and peak currents. When a phase leg fails, a new Three-Phase 8-Switch Inverter (3P8SI) is reconfigured. Applying the conventional single vector Model Predictive Current Control (MPCC) to the fault-tolerant structure will output a large current ripple. To reduce the current ripple of 3P8SI under conventional model prediction fault-tolerant control, a Dual Vector Modulation MPCC strategy is proposed. Based on the fault-tolerant operation mechanism of 3LT2I, the mathematical model of the reconstructed 3P8SI is established; in each control cycle, two basic voltage vectors are used to simultaneously track the target vector, and the prediction control principle of the modulation model is used to calculate the value of each voltage vector. action time. In addition, the reference voltage is calculated using the deadbeat control principle to obtain the sector where the reference voltage is located. The advantage of this method is that in each control cycle, only 3 and 4 voltage vector combinations need to be preselected for online evaluation, and the optimal voltage vector combination can be obtained. The experimental results show that the control method has a small output current ripple and good steady-state and dynamic performance.