Oscillatory Fault Location Of Multi-Loop Process Systems

The problem of process oscillatory fault location is about studying how to find the source of fault quickly and effectively when plant-wide oscillatory disturbances appear in the multi-loop system. The contribution of this thesis is to locate the position of process fault and to provide information support for further maintenance and protection.With the expansion of process systems and requirement of high reliability, the technology of fault detection and diagnosis has developed from the study of sing-loop system to multi-loop systems. As an important part of the fault detection and diagnosis technology, oscillatory fault location of multi-loop process systems has drawn more and more research attention. Because of the large-scale and complex relation of multi-loop systems, the appearance of system fault will enlarge the influence range, especially when oscillation appears, plant-wide disturbance will affect the production process and product quality seriously.For this reason, the study of reasonable and effective method of oscillatory fault location in multi-loop process systems is necessary. In this thesis we studied the problem of oscillation-propagation systematically with the tool of signed digraph in graph theory, and proposed a new concept called control-loop rooted tree and a new fault location technique. In the end, arithmetic of this method was given and simulation tests showed the effectiveness of the approach.The main contents and results of this paper are as follows:1)We overviewed the research of oscillatory fault detection and diagnosis, analyzed the features of multi-loop oscillatory fault propagation, and explained the difference of some fault location methods.2)We introduced the concept of control-loop digraph, and analyzed the graph with matrix tool and set theory. Then we proposed an improved strict digraph method, and put forward the location arithmetic of this method.3)A method to identify the propagation path of plant-wide oscillation was proposed, which is based on control-loop rooted tree. And we gained the topology structure of loop nodes with the study of control-loop relations.4)A new method of oscillatory fault location based on the combination of control-loop rooted tree and correlation function was proposed. And we gained a location arithmetic which can find the source of oscillation-fault effectively. In the end, the simulation demonstrated that the approach in this paper is effective.