Fault diagnosis of voltage sensor in grid-connected 3-phase voltage source converters

This paper proposes a fault diagnosis method of the line-to-line voltage sensors in grid-connected 3-phase voltage source converters. The line-to-line voltage sensors are an essential device to obtain the information of the grid side voltages for controlling the converters. If there are problems in the voltage sensors by some faults, the controller obtains wrong information of the grid voltage. It causes the unbalance 3 phase currents and the pulsation of the DC-link voltage even though the power grid is healthy. Therefore fault diagnosis methods are required to detect the failure and to avoid the abnormal operation. This proposed diagnosis method identifies whether the fault is at the voltage sensor or the power grid when the abnormal values are measured from the line-to-line voltage sensors. Then the fault tolerance control is possible in case of the voltage sensor fault. The proposed method can improve the system reliability by just adding some software algorithm without additional hardware circuits. The usefulness of this paper is verified through the computer simulation and experiment.