White Rabbit Multi-Point Time Distribution Network

A nanosecond-accuracy, scalable, multi-point time- and frequency dissemination has been set up in an existing DWDM optical fiber network spanning approximately 200 km, using the White Rabbit (WR) Precision Time Protocol (PTP). Presented novelties in this paper are: a performance study of 5 cascaded WR switches allowing a wide fan-out; reference delay compensation ensuring that the time received by the user is synchronized with the reference timescale within a few nanosecond offset; experiments with a master clock priority algorithm for redundant operation and experimental results of hold-over performance.

White Rabbit Multi-Point Time Distribution Network

A nanosecond-accuracy, scalable, multi-point time- and frequency dissemination has been set up in an existing DWDM optical fiber network spanning approximately 200 km, using the White Rabbit (WR) Precision Time Protocol (PTP). Presented novelties in this paper are: a performance study of 5 cascaded WR switches allowing a wide fan-out; reference delay compensation ensuring that the time received by the user is synchronized with the reference timescale within a few nanosecond offset; experiments with a master clock priority algorithm for redundant operation and experimental results of hold-over performance.

Unbalanced Current Reduction Method of Microgrid Based on Power Conversion System Operation

In isolated areas such as islands with small power grids, the BESS (Battery energy storage system) can supply the standard voltage and frequency to the power system to achieve 100% of renewable sharing. In addition, the installation of additional BESS may be required in the microgrid due to technical limitations such as redundant operation and manufacturer specifications. Thus, the BESSs in a microgrid can be split into main and sub BESSs which play a role as the main source and auxiliary services, respectively. Generally, the ratio of unbalance current in microgrid system tends to be high, because of inherently unbalanced single phase load distribution. However, because the capacity of BESS is calculated under balanced conditions, the PCS (Power conversion system) of BESS may stop protecting its switching device from a single phase overcurrent in actual operation. From this perspective, this paper proposes that the sub BESSs perform dual current control to supply the unbalanced current instead of the main BESS. In the simulation result of the proposed method, the current unbalance rate of the main ESS has been reduced by about 26%. Through the proposed control scheme, it is possible to prevent an unexpected single phase overload of the main BESS in the microgrid.

Effective Real-Time Scheduling Optimization for Multi-Functional Mixed-Criticality Systems

The heterogeneous distributed embedded systems integrated of multiple functions with different criticality levels are multi-functional mixed-criticality systems (MMCSs). The state-of-the-art work has studied the real-time scheduling in MMCS; however, it is not well designed in system switching mechanism and operation which may lead to missing the deadlines of high-criticality functions and redundant operation. In this study, we improve and optimize the problem by developing an algorithm called rearrangement-based scheduling for MMCS (RSM). The RSM algorithm optimizes the following two main aspects. The first aspect is optimizing system-criticality switching mechanisms, including system criticality changed up and down. The second aspect is the effective operation in system-criticality switching to reduce redundant operation. Experiments are performed, and results show that the RSM algorithm can achieve lower overall makespan and deadline miss ratios (DMRs) than the existing algorithms.

Research on redundant control mode of coordinated controller based on dual control cores

Dual CPU redundant operation of PLC is of great significance to the reliability of industrial automation control system. In view of the problems existing in the traditional dual CPU PLC redundancy control mode based on hardware strategy, this paper proposes a dual CPU redundancy control idea based on software strategy, and describes in detail the specific scheme of Dual CPU redundancy software design using A-B ControlLogix series PLC.

Analysis of the reliability properties of duplex structures of emergency protection systems with constant redundancy

The work is devoted to the comparison of two options for the operation of the duplex structure of controllers for the developed methods for assessing the reliability and fault tolerance of multichannel control safety systems and emergency protection systems with incompatible states and a variety of possible options for the sequences of occurrence of obvious and hidden failures with the calculation of the probabilities of these systems being in a working condition in a false state triggers at a given time interval.The problem of ensuring the reliability of information management systems is a complex and complex problem, especially for potentially dangerous technical complexes.For the developed mathematical model for assessing the reliability and fault tolerance of multichannel control systems for safety and emergency protection as systems with elements with three incompatible states: the system is in a healthy state, in a state of false (redundant) operation at a given time interval, it is necessary to compare two options for the duplex structure of controllers.The paper compares two variants of operation of the duplex structure of controllers: Hot StandBy and SA&C.Based on the results obtained, SA & C systems with restoration is a better option compared to the Hot StandBy system with restoration.The results obtained will be used in further studies to obtain dependencies for much more complex structures of automatic protection systems.

Dynamic Top-K Interesting Subgraph Query on Large-Scale Labeled Graphs

A labeled graph is a special structure with node identification capability, which is often used in information networks, biological networks, and other fields. The subgraph query is widely used as an important means of graph data analysis. As the size of the labeled graph increases and changes dynamically, users tend to focus on the high-match results that are of interest to them, and they want to take advantage of the relationship and number of results to get the results of the query quickly. For this reason, we consider the individual needs of users and propose a dynamic Top-K interesting subgraph query. This method establishes a novel graph topology feature index (GTSF index) including a node topology feature index (NTF index) and an edge feature index (EF index), which can effectively prune and filter the invalid nodes and edges that do not meet the restricted condition. The multi-factor candidate set filtering strategy is proposed based on the GTSF index, which can be further pruned to obtain fewer candidate sets. Then, we propose a dynamic Top-K interesting subgraph query method based on the idea of the sliding window to realize the dynamic modification of the matching results of the subgraph in the dynamic evolution of the label graph, to ensure real-time and accurate results of the query. In addition, considering the factors, such as frequent Input/Output (I/O) and network communication overheads, the optimization mechanism of the graph changes and an incremental maintenance strategy for the index are proposed to reduce the huge cost of redundant operation and global updates. The experimental results show that the proposed method can effectively deal with a dynamic Top-K interesting subgraph query on a large-scale labeled graph, at the same time the optimization mechanism of graph changes and the incremental maintenance strategy of the index can effectively reduce the maintenance overheads.

Incipient Fault Detection of the Inverter Fed Induction Motor Drive

Inverter fed Induction motor drives are deployed across a variety of industrial and commercial applications. Although the drives in the question are well known for their reliable operation in any type of environment, it becomes an important daunting critical task to have them in continuous operation as per the applications’ requirement. Identifying the faulty behavior of power electronic circuits which could lead to catastrophic failures is an attractive proposition. The cost associated with building systems devoted for monitoring and diagnosis is high, however such cost could be justified for the safety-critical systems. Commonly practiced methods for improving the reliability of the power electronic systems are: designing the power circuit conservatively or having parallel redundant operation of components or circuits and clearly these two methods are expensive. An alternative to redundancy is fault tolerant control, which involves drive control algorithm, that in the event of fault occurrence, allows the drive to run in a degraded mode. Such algorithms involve on-line processing of the signals and this requires Digital Signal Processing of the signals. This paper presents the FFT and Wavelet transform techniques for on-line monitoring and analyzing the signals such as stator currents.