Reconfiguration of an industrial steam generator using bond graph modelling

In this paper, we survey some recent advances made in the field of bond graph modelling and show that bond graph modelling method is well suited to solve modelling, fault diagnosis and fault tolerant control problems in complex process engineering systems. We present a case study of development and implementation of fault tolerant control scheme for a steam generator process. Steam generator is a safety-critical complex thermo-fluid process, which involves storage and transport of under-saturated and saturated fluids, as well as phase transformations. Bond graph modelling, which is a unified tool for multi-energy domain system representation, is used to model the process. Moreover, the fault indicators are directly obtained from the bond graph model. Causal paths in the model are used to determine various redundancies, which are then used to determine possible system reconfigurations and operating modes, by taking various operating constraints (equipment availability, saturations, power ratings, etc.) into consideration. An academic example is used to explain the steps involved in the analysis of fault indicators, fault isolation, system recovery, operating modes, transition schemes, and selection of appropriate control laws. Implementation of the developed algorithms in a supervision system for the steam generator process and some experimental results from the process, during nominal and reconfigured operations, are presented.