Circulating Current-Based Open-Circuit Fault Diagnosis for Parallel Inverters

This article proposes an open-circuit fault diagnosis method for parallel inverter switches based on circulating current. The mixed logic dynamic (MLD) model of the parallel inverter system is established. Based on this model, a Luenberger observer is applied to estimate the circulating current of the parallel inverter system. The observed value of the circulating current is compared with the actual value of the circulating current to obtain the residual signal. By using the residual signal, the faulty switches are detected and located. In addition, the reasonable thresholds of the residual signal are set to eliminate the interference of other factors on the fault diagnosis results, which enhances the robustness of the proposed fault diagnosis method. The experimental results verify the effectiveness of the proposed fault diagnosis method. Additionally, the proposed fault diagnosis method does not require additional devices or equipment, and has low cost and good practicability.