Contribution on observation and fault diagnosis of a multicellular converter

Abstract

The work presented in this thesis concerns the observation and diagnosis of faults in the 3-cell converter which is considered to be a hybrid system du to its switching behavior. Indeed, the observability analysis has been shown for a hybrid time trajectory using a geometric approach based on the computation of the unobservable subspace along the hybrid time trajectory. A sliding mode observer is then designed for the observable subspace of the converter. The convergence of the observation error is demonstrated using the Lyapunov theory. Observer parameters are computed by solving a linear matrix inequality (LMI). The simulation results show a good reconstruction of the floating voltages of the converter. The second part is devoted to the diagnosis of converter faults. Indeed, a geometric approach has been applied for the determination of the subspaces sensitive to a set of faults and insensitive to another set. Fault detection and isolation is based on the designing of observer-based residual generators. The simulation results show the efficiency of the proposed residual generators based on sliding mode observers.