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Power transmission lines of traditional power transmission systems (PTSs) may suffer from some faults that can lead to blackouts. This work proposes a methodology to construct hierarchical distributed control systems (DCSs) for the automatic fault detection and restoration of PTSs using colored Petri nets (CPNs). If faults occur in power transmission lines, they can be detected by supervisors, and local solutions can be computed to restore the faults. Each supervisor is coordinated by a coordination protocol to perform the computation of local solutions. The structures of traditional PTSs are simplified and defined by CPNs, and the derivation processes of fault detection and restoration based on the proposed coordination protocol are verified by the mathematical methods of CPNs. Finally, the complexity of the proposed hierarchical DCS and coordination protocol is discussed and an example is given to illustrate the proposed method. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

As a type of process plant, a refinery is characterized by the interaction of discrete events and continuous processes. To schedule crude oil operations in a refinery, it is necessary to define and schedule the jobs simultaneously such that heuristics and meta-heuristics cannot be directly applied. It is very challenging to schedule crude oil operations. To solve this problem, it is decomposed into two subproblems hierarchically. At the upper level, a refining schedule is found, while at the lower level a detailed schedule is obtained to realize the refining schedule. Given a refining schedule at the upper level, this paper studies the detailed scheduling problem at the lower level. Based on a control-theoretic perspective, the problem is innovatively transformed to a problem of assigning charging tanks to distillers such that meta-heuristic methods can be applied. Then, a genetic algorithm (GA) approach is developed to solve the problem. In realizing the proposed GA, based on a set of existence conditions of a feasible schedule, methods are presented to guarantee that each chromosome corresponds to a feasible schedule. An industrial case study is used to show the application of the proposed method. It shows that the method works well and is applicable to real-life problems. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Nondeterministic firing of concurrent transitions in Petri nets (PNs) may lead to the disappearance of conflicts. The disappearance implies that the partial conflicting transitions in a conflict become disabled before the resolution of the conflict. The phenomenon is called confusions that are caused by the interlacement of conflicting and concurrent transitions in PNs, which generates incomplete and faulty system conflicting behavior such that conflicts cannot be correctly resolved. In this paper, conflict-increasing confusions (CICs) and conflict-decreasing confusions (CDCs) in a PN are investigated. The relation graph of conflicts and confusions (RGC²) in a PN is proposed to detect the structure of confusions. To avoid the occurrence of confusions in a PN, an algorithm based on generalized mutual exclusion constraints (GMECs) is proposed, which can generate confusion-avoidance supervisors such that the occurrence of conflicts can be ensured in a PN. Finally, an example of confusion detection and avoidance in a flexible assembly system is presented. [ABSTRACT FROM AUTHOR]