A Simultaneous Diagnosis Approach for Power Switch, Grid-Side Current Sensor, and DC-Link Voltage Sensor Faults in Single-Phase Three-Level Rectifiers

This article introduces a scheme for diagnosing power switch, grid-side current sensor, and dc-link voltage sensor faults simultaneously in single-phase three-level rectifiers for the first time. First, the model of the rectifier system with the aforementioned faults is reasonably constructed. Next, an intermediate variable is established for the rectifier system by augmenting the system and performing a series of transformations, which helps reduce the complexity of the system and facilitates subsequent observer design. Subsequently, an innovative reduced-order sliding mode observer (SMO) is devised for the intermediate variable to obtain simultaneous and precise estimation of the original state, grid-side current sensor fault, and dc-link voltage sensor fault. Finally, on the basis of the estimation results, the differentiation between the open-circuit (OC) fault, grid-side current sensor fault, and dc-link voltage sensor fault is achieved, and a fault diagnosis strategy with adaptive threshold is proposed. Specifically, this method facilitates the identification of the defective power switch and proficiently estimates various kinds of grid-side current sensor faults and dc-link voltage sensor faults. The robustness and availability of the developed method are showcased via the presentation of experimental findings and a comparative evaluation.