Fault Diagnosis Strategy for MMC Current Sensors Based on Fault Characteristics Recognition

In order to ensure the safe operation of modular multilevel converter (MMC), the problem of fault diagnosis of insulated gate bipolar transistor (IGBT) has become one of the widely discussed topics. However, as an important component of MMC control link, the fault diagnosis strategy of sensors is rarely reported and studied. This article first analyzes the fault mechanism of current sensors for MMC and elaborates on the characteristics of the submodule (SM) capacitor voltage under different fault types. Then a diagnosis strategy of current sensors fault for MMC based on fault feature recognition is proposed. This strategy can achieve fault detection and localization of MMC output current sensors and arm current sensors by detecting the voltage of SM capacitors, without the need for any additional hardware circuits. The results of the experiment show that the strategy proposed in this article can quickly and accurately realize the fault diagnosis of current sensors for MMC and has robustness under the conditions of load disturbance and parameter mismatch.