Current observer-based online open-switch fault diagnosis for voltage-source inverter

In order to guarantee the system reliability and enhance post-fault maintenance efficiency of inverters, this paper presents an current observer-based online open-switch fault diagnosis method for the voltage-source inverters (VSI). Analyzing the state space model of VSI when fault occurs, a state observer of the system is built to estimate phase currents. Once the open-switch fault occurs, the current residual vector between the estimated currents on observer and the measured currents, and fault diagnosis is realized by exploiting the featured amplitude and phase of the current residual vector. In order to realize on-line diagnosis with high reliability and speed, the average value of current residuals in a fundamental period is obtained and Clark transformation is performed so as to acquire vector angle. In addition, the sum of absolute values of measured currents is normalized to serve as the sign of fault occurrence. The simulation and experimental results show the effectiveness of proposed method.