Ethernet-based Communication Network Research Articles

Utilization of SDN Technology for Flexible EtherCAT Networks Applications

At the beginning of the current century, Ethernet-based communication networks began to be implemented in industrial applications. Some previously used protocols were migrated to Ethernet networks, while many others were strictly developed for this communication medium. Numerous industrial Ethernet protocols do not deliver all the capabilities provided by the Ethernet. For example, limitations may arise associated with wireless communication, use of dedicated switching devices, or operation solely for certain topologies. On the other hand, new technologies are now available, such as software defined networks (SDN), that add new features to Ethernet-based communication systems. In this paper, an EtherCAT network in combination with SDN is analyzed. EtherCAT network may only consist of devices with an implemented EtherCAT protocol stack. Therefore, regular Ethernet switches cannot typically be used in this network and, hence, special network infrastructure may be required to create topologies other than standard line topology. It is shown, however, that this limitation can be overcome by the application of SDN. In addition, a definition of datagram forwarding rules (called SDN flows here) is given, and we demonstrate that EtherCAT datagrams can be sent through routes that are required for proper EtherCAT network operation.

ITANS: Incremental Task and Network Scheduling for Time-Sensitive Networks

Recent trends such as automated driving in the automotive field and digitization in factory automation confront designers of real-time systems with new challenges. These challenges have arisen due to the increasing amount of data and an intensified interconnection of functions. For distributed safety-critical systems, this progression has the impact that the complexity of scheduling tasks with precedence constraints organized in so-called cause-effect chains increases the more data has to be exchanged between tasks and the more functions are involved. Especially when data has to be transmitted over an Ethernet-based communication network, the coordination between the tasks running on different end-devices and the network flows has to be ensured to meet strict end-to-end deadlines. In this work, we present an incremental heuristic approach that computes schedules for distributed and data-dependent cause-effect chains consisting of multi-rate tasks and network flows in time-sensitive networks. On the one hand, we provide a common task model for tasks and network flows. On the other hand, we introduce the concept of earliest and latest start times to speed up the solution discovery process and to discard infeasible solutions at an early stage. Our algorithm is able to solve large problems for synthetic network topologies with randomized data dependencies in a few seconds on average under strict end-to-end deadlines. We have achieved a high success rate for multi-rate cause-effect chains and an even better result for homogeneous or harmonic chains. Our approach also showed low jitter for homogeonous cause-effect chains.

Cost-Effective Hot-Standby Redundancy With Synchronization Using EtherCAT and Real-Time Ethernet Protocols

When designing and manufacturing industrial computer systems, many different issues must be considered. The most important of these are the temporal characteristics and real-time operation. Another factor is the distribution of the system, usually over a wide area, operation in harsh environments, and, finally, the system’s dependability. When addressing the last issue, redundancy is commonly employed. This can be applied in many ways, e.g., by providing redundant communication links (buses and communication modules) and redundant sensors, input/output modules. This article considers systems that have computing unit redundancy, for which programmable logic controllers (PLCs) are often used. On the one hand, systems of this kind should be reliable and capable of real-time operations. On the other hand, they should be economically attractive. There are many solutions available on the market for the implementation of systems with redundancy. However, they are always rather expensive. Of course, the price is for a robust solution with dedicated hardware and many built-in features that are crucial in highly reliable systems, such as autodiagnostics. Nevertheless, such powerful products are not always required. This article presents an example of a cost-effective implementation of an industrial controller with hot-standby redundancy using regular devices and an Ethernet communication interface for the needs of synchronization of the computing units. For this purpose, EtherCAT and real-time Ethernet protocols were used. Note to Practitioners—This article is motivated by the problem of high cost of application of systems with computing units redundancy based on dedicated components, such as the latest S7-1500R/H Redundant System by Siemens or PACSystems Profinet System Redundancy by Emerson (former GE IP). The above solutions are powerful and sophisticated. However, sometimes, simpler solutions would suffice. This article shows how a system with computing unit redundancy could be built in a cost-effective way and, at the same time, provide all the basic features expected from systems with redundancy, i.e., fault detection, automatic switchover, and synchronization. All this is done with a common embedded programmable device and an open Ethernet-based communication network.

Formal reliability and failure analysis of ethernet based communication networks in a smart grid substation

AbstractSecure and continuous operation of a smart grid substation mainly depends upon the reliable functioning of its communication network. The communication system of a smart substation is typically based on a high performance Ethernet communication network that connects various intelligent embedded devices, such as Intelligent Electronic Devices (IED) andMerging Units (MU), to ensure continuous monitoring, automation and efficient demand response of the smart substation. Traditionally, Reliability Block Diagram (RBD) and Fault Tree (FT) methods are used to develop reliability and failure models for these communication networks by considering the failure characteristics of their substation intelligent embedded devices and other components, like transformers and circuit breakers. These resulting reliability and failure models are then analyzed using paper-and-pencil methods or computer simulations, but they cannot assure accuracy in the analysis due to their inherent limitations. As an accurate alternative, we propose a methodology, based on higher-order logic theorem proving, for conducting the formal RBD and FT-based reliability and failure analysis of smart substation communication networks, respectively. This paper also describes a sound transformation of smart grid FT models to their equivalent RBDs - a well-known method to reduce the complexity of FT-based failure analysis. Some ML-based tactics have been developed to automatically compute the reliability and failure probability of smart grid substations for practical purposes.

Using IEC 61850 GOOSE Service for Adaptive ANSI 67/67N Protection in Ring Main Systems with Distributed Energy Resources

Smart Grids are electricity networks that use digital technology to co-ordinate the needs and capabilities of all generators, grid operators, end users and electricity market stakeholders in such a way that it can optimize asset utilization and operation while maintaining system reliability, resilience and stability. However, Smart Grids are increasingly proposing a much more distributed architecture with the integration of multiple Distributed Energy Resources (DERs) that demand different control and protection schemes. In that sense, the implementation of standards such as IEC 61850 and the integration with Ethernet-based communication networks provide novel tools to manage DER efficiently. This paper analyses the potential usage and benefits of ANSI 67/67N protection in combination with Generic Object Oriented Substation Event (GOOSE) communication service, from the standard 61850 of the International Electro-technical Commission (IEC), for providing adaptive network protection, specifying the configuration and implementation and exposing the obtained results.

A service interruption free testing methodology for IEDs in IEC 61850-based substation automation systems

This paper presents a methodology for the testing of intelligent electronic devices (IEDs) in IEC 61850-based substation automation systems (SAS), without any service interruption to the end users, during the testing process. IEC 61850-based SAS provides opportunities for a new level of substation operation, enhancing operating efficiency, and protection reliability based on Ethernet-based communication networks. Due to these changes to the conventional substations, importance and dependency on IEDs is increasing rapidly. Frequency of faults occurring in the power systems is random in nature and is unpredictable. It is necessary to test and maintain the IEDs to ensure their proper operation at crucial times. This paper presents a novel methodology for testing the IEDs, without compromising the service reliability during the testing process. The proposed methodology exploits the inherit characteristics of IEC 61850 standard i.e. Network - based communication, interchangeability between multivendor IEDs, and engineering based on substation configuration language (SCL) files. The feasibility and robustness of the proposed method has been verified by performing several performance verification tests with different performance metrics.

Design of a Backup IED for IEC 61850-Based Substation

The IEC 61850-based substation automation system (SAS) provides opportunities for a new level of substation operation, enhancing operating efficiency and protection reliability with a new environment based on an Ethernet-based communication network and high-performance intelligent electronic devices (IEDs). With these changes, importance and dependence on IEDs are increasing rapidly in IEC 61850-based substations. While consideration of protection device faults has so far been infrequent, IED faults will become increasingly important in the future. Thus, this paper proposes a design of a backup IED for protection IED faults in IEC 61850-based substations. The proposed backup IED can be remotely converted into any type of protection IED without IED exchange, firmware update, or field control. The backup IED was designed through SCL engineering and file transfer functions in IEC 61850 and implemented by Windows programming with a commercially available IEC 61850 library.

EPON을 기반으로 한 해상 풍력 단지 통신망 구조

In recent, the communication networks of wind power farm are becoming crucial technologies for monitoring and controlling the large-scale offshore wind power farm. In this paper, EPON based communication network architectures are proposed in order to combat the problems of conventional Ethernet based communication network such as delay, data processing overhead and the fairness of data transmission among turbines in offshore wind power farm. The proposed architecture constructs the point to multi-point network by using OLT and ONUs installed in central control center and wind turbines respectively. The EPON based communication network architecture has low cost, high reliability, and fair transmission capability. To evaluate the performance of proposed architectures, the wind power farm based on IEC 61850 is modelled by using OPNET The simulation results are analyzed and compared with conventional Ethernet based communication network in terms of the overhead, delay and fairness of data transmission.

Performance of IEC 61850-9-2 Process Bus and Corrective Measure for Digital Relaying

International Electrotechnical Commission (IEC) standard 61850 proposes the Ethernet-based communication networks for protection and automation within the power substation. Major manufacturers are currently developing products for the process bus in compliance with IEC 61850 part 9-2. For the successful implementation of the IEC 61850-9-2 process bus, it is important to analyze the performance of time-critical messages for the substation protection and control functions. This paper presents the performance evaluation of the IEC 61850-9-2 process bus for a typical 345 kV/230 kV substation by studying the time-critical sampled value messages delay and loss by using the OPNET simulation tool in the first part of this paper. In the second part, this paper presents a corrective measure to address the issues with the several sampled value messages lost and/or delayed by proposing the sampled value estimation algorithm for any digital substation relaying. Finally, the proposed sampled value estimation algorithm has been examined for various power system scenarios with the help of PSCAD/EMTDC and MATLAB simulation tools.