Load-sharing strategy taking account of compressor degradation

The objective of designing a control structure that takes the degradation of the system into account is to preserve its performance and mitigate further damage. This problem is often encountered in process industries, e.g. in gas processing plants, where the question arises how to distribute the control effort among multiple actuators based on their degradation. The main focus of this work is to investigate how to assign the loads in a two-compressor system taking the degradation, i.e. the loss of available performance, into consideration. Contrarily to other approaches, such as methods based on distance to surge or predictive control, the algorithm proposed in this work does not require a reconfiguration of the control structure, at the same time taking explicitly the degradation into account. The simulation results confirm that this approach mitigates further loss of performance, in particular for compressors, which have significantly different degradation rates

Degradation modelling in process control applications

Degradation of industrial equipment is often influenced by how a system is operated, with certain operating points likely to accelerate degradation. The ability to mitigate degradation of an industrial system would result in improved performance and decreased costs of operation. The thesis aims to provide ways for managing degradation by adjusting the operating conditions of a system. The thesis provides original insights and a new classification of models of degradation to facilitate the integration of degradation models into process control applications. The thesis also develops an adaptive algorithm for degradation detection and prediction in turbomachinery, which is able to predict the expected future values of a degradation indicator and to quantify the uncertainty of the prediction. The thesis then proposes two frameworks for load-sharing in a compressor station in which the compressors are subject to degradation. One framework considers management of degradation and the other one focuses on power consumption of the whole station. These examples show how modelling of degradation can have an impact on the operation of an industrial system. The approaches have been evaluated with case studies developed in collaboration with industrial partners. As demonstrated in the case studies, the outcomes of the research presented in this thesis provide new ways to take account of degradation in process control applications. The thesis discusses steps and directions for future work to facilitate the technology transfer from academic to industrial implementation.Open Acces