Network Operating Research Articles

Fairness in optimal operation of transactive smart networked modern multi-carrier energy systems: A two-stage optimization approach

Multi-Carrier Energy Systems (MCESs) have attracted global appeal and indicated broad outlooks in developing green energy resources in the community. The transactive networked operation of multiple MCESs improves economic opportunities and system flexibility. Nevertheless, how to fairly and convincingly allocate the total expenses among MCESs is a crucial challenge that is addressed in this paper. To tackle the fairness issue, a two-stage optimization framework in the transactive networked MCESs is developed. In the first stage, named the islanding operation mode, the operation cost of each MCES is minimized and the optimization outcomes are sent to the central operator of the transactive networked MCESs. In the second stage, the central operator solves an optimization problem to minimize the total operation cost of the transactive networked MCESs considering energy transactions among MCESs and fairness constraints. The fair cost allocation constraints lead to similar or less contributions in total operation cost in the transactive networked structure compared with the islanding mode. The proposed model is structured as a Mixed-Integer Linear Programming problem and formulated in GAMS modeling language. The results indicate that the proposed two-stage optimization approach decreases the operation cost of the networked MCESs by 16.7% while the fairness issue was satisfied.

Analysis of the Influence of Load on the Value of Zero-Voltage Asymmetry in Medium-Voltage Networks Operating with Renewable Energy Sources

The phenomenon of voltage asymmetry is common in electricity networks and is the cause of many unfavourable phenomena occurring, such as an increase in power and energy losses, as well as the abnormal operation of certain loads. Voltage asymmetry can be caused by several different factors, which include the design of the transmission line (e.g., routing of conductors in relation to each other and the earth), the parameters of consumer circuits (e.g., unequal loading of individual phases), or the design of network equipment (e.g., generators or transformers). An asymmetrical condition also occurs during system disturbances such as single-phase short circuits or lightning. One of the many factors impinging on voltage asymmetry in the electrical network is also the effect of load, but in the case of medium voltage power networks, this effect is neglected in the literature. This paper presents and evaluates the influence of the power consumed by consumers on the values of zero-voltage asymmetry factor indices in medium voltage compensated power networks with the neutral point earthed by an inductance (Petersen coil) operating with wind and photovoltaic power plants.

Detection of Underwater Ships Categorically Using Convolutional Neural Network and Power Efficient Remotely Operated Vehicle

Detection of Underwater Ships Categorically Using Convolutional Neural Network and Power Efficient Remotely Operated Vehicle

Simulation Study of the Control Strategy of a DC Inverter Heat Pump Using a DC Distribution Network

Photovoltaics, energy storage, direct current and flexibility (PEDF) are important pillars of achievement on the path to manufacturing nearly zero energy buildings (NZEBs). HVAC systems, which are an important part of public buildings, play a key role in adapting to PDEF systems. This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems. Along with the characteristics of a DC distribution network and different operating conditions, a DC inverter heat pump has the ability to adapt to changes in the DC bus voltage and adds flexibility to the system. Theoretical models of the DC inverter heat pump integrated with an ice storage unit were developed. The control strategies of the DC inverter heat pump system considered the influence of both room temperature and varied bus voltage. A simulation study was conducted using MATLAB & Simulink software with simulation results validated by experimental data. The results showed that: (1) The bus fluctuation under the rated working voltage had little effect on the operation of the unit; (2) When the bus voltage was fluctuating from 80%–90% or 105%–107%, the heat pump could still operate normally by reducing the frequency; (3) When the bus voltage was less than 80% or more than 107%, the unit needed to be shut down for the sake of equipment safety, so that the energy storage device could adjust to the sharp decrease or rise of voltage.

Experimental tests of submersible vane pumps

The technical task of creating new designs of submersible vane pumps is to maintain stable operating parameters and increase the productivity of the pumping station with periodic regeneration and sediment removal. The pumping well station contains an outer chamber and an inner chamber, in which a pumping unit is installed, and pipelines are connected to the lower and upper pools. In the structure under study, the upper parts of the outer and inner chambers are equipped with a sealed head, and the lower part of the outer chamber is equipped with a stopper. The side surface of the inner chamber is made of elastically deformable material. An elastic pipeline with an ejector at its end with curvilinear helical grooves on the inner surface of the nozzle part of the ejector is connected to the pipeline connected to the tailpipe, and water level meters are installed in the outer chamber. The technique of balance testing of new designs of submersible vane pumps was applied because the existing technology is insufficient for correct balance tests. Research methods involve the design of the impeller, which is rigidly mounted on the shaft. The methodology has been adjusted to apply to multistage pumps with different types of impellers. In the energy balance of this pump, the power losses due to friction in the individual axial support of the impeller are additionally determined. Experimental work was carried out, resulting in measurements of the hydrodynamic moment acting on the guide vane grate. Experimental work was carried out on a vertical stand with new pump impellers ETsV-10-120-40 and with a service life of 1 year. Parametric tests made it possible to determine the change in the external parameters of the pump depending on changes in its operating conditions and network characteristics.

Performance Assessment of a RIS-Empowered Post-5G/6G Network Operating at the mmWave/THz Bands

Reconfigurable Intelligent Surfaces (RISs) are considered to be a key enabling technology for 6G as they can potentially provide a boost in performance with a high energy efficiency. RISs rely on the use of arrays with a large number of low-cost quasi-passive reflecting elements which can be individually tuned in order to shape the radio wave propagation. This can effectively enable the implementation of smart radio environments, increasing the capacity and improving the coverage of the system. Since most RISs related studies focus on evaluating the gains of RIS based solutions in simplified communication scenarios, in this paper we investigate the potential benefits of RISs when integrated into future wireless networks within the context of post-5G/ 6G systems. With this aim, we present an iterative algorithm for accomplishing the joint design of the access point precoder and phase-shifts of the RIS elements considering a multi-stream multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) link. Based on this approach, we then present the system-level evaluation of a RIS-aided post-5G/6G network deployment operating in two different bands, mmWave and sub-THz, and which considers both near-field and far-field propagation models. The results obtained in two different environments namely, Indoor Open Office (IOO) and Urban Micro Truncated (UMT), show that the adoption of the proposed RIS-based approach can effectively improve the throughput and coverage area.

Multi-Unit Franchising and Relational Governance: A Study of Operating Networks in Brazil

Multi-Unit Franchising and Relational Governance: A Study of Operating Networks in Brazil

К ВЫВОДУ УРАВНЕНИЙ РЕГУЛИРОВАНИЯ И АНАЛИЗУ ОСОБЕННОСТЕЙ ГИДРАВЛИЧЕСКИХ РЕЖИМОВ ОТКРЫТЫХ СИСТЕМ ТЕПЛОСНАБЖЕНИЯ БЕЗ РЕГУЛЯТОРОВ РАСХОДА НА АБОНЕНТСКИХ ВВОДАХ

Energy efficiency and improved quality are currently very relevant issues in the housing and communal sector. These can be addressed, first of all, by introducing automated control systems and implementing optimized algo-rithms for monitoring and regulating heating and heat supply processes in general. The task of studying the features of the hydraulic regime of open heat supply systems without flow controllers at subscriber inputs is considered. Since a significant number of heating networks are open, the ban on their operation was reversed by Federal Law No. 438-F3 of December 30, 2021. Existing literature on open heating networks was analyzed and summarized. The hydraulic re-gime of open heating networks is very complex; its characteristic features are not sufficiently detailed and not clearly explained in the literature. This introduces difficulties in improving the quality of operation of open networks and uni-versity educational programs. In this paper, a detailed derivation of the main relationships characterizing the hydraulic regime is provided, with the assumption that the analyzed heat network is configured according to S.A. Chistovich’s ho-rizontal track principle. This makes it possible to reduce the calculation of a real operating network to a calculation of the hydraulic regime of a single-loop equivalent heat network using Kirchhoff’s laws for hydraulic circuits, which, un-like electrical circuits, are always non-linear circuits. The obtained solutions for specific cases were analyzed; in partic-ular, the influence of the water intake on the heating mode of consumers was studied for various characteristics of the heat supply system and outdoor temperature. The aforementioned algorithms can be used both for the algorithmic sup-port of automated heat supply control systems and for educational purposes.

Assessment of SIRGAS-CON tropospheric products using ERA5 and IGS

Abstract Zenith Tropospheric Delays (ZTDs) are used to correct tropospheric effects that cause a delay in the signal measured by Global Navigation Satellite Systems (GNSS) receivers and obtain accurate measurements. ZTD can be estimated from GNSS processing, which means they may suffer from occasional or systematic errors. Therefore, it is necessary to assess the quality and stability of these data over time, since ZTDs are used in several applications that require centimeter precision. Within this context, this work aims to assess the available ZTD of the whole Geodetic Reference System for the Americas Continuously Operating Network (SIRGAS-CON), consisting of 467 stations, spanning the period from January 2014 to December 2020 using the most recent Numerical Weather Model ERA5 from the European Centre for Medium-Range Weather Forecasts and common stations to the International GNSS Service (IGS) for an intercomparison. Results show that 10% of the stations present some instability, such as periods of highly dispersed data or discontinuities, with more occurrence in stations located in Argentina, Uruguay and Colombia. The remaining 90% proved to have stable and reliable ZTD, both in comparison with ERA5 and IGS.

A multi-objective optimization of FCL and DOCR settings to mitigate distributed generations impacts on distribution networks

Despite providing increased reliability and power quality in meeting the load demand, the integration of DGs has imposed challenges on the protection system. High penetration of DGs changes the overall network impedance and increases the fault current level in the network. Consequently, some buses are exposed to critical conditions, violate the circuit breakers (CB) handling capacity, and affect the existing relay coordination settings. To mitigate these adverse impacts, fault current limiters (FCL) can be a potential solution to minimize the short circuit current within permissible switchgear-rated limits. Due to its expensive cost, it is crucial to ensure the optimal FCL placement and sizing, and at the same time maintain the effectiveness of the protection performance during various network operation states. This research formulates FCL and directional overcurrent relay (DOCR) settings as a combined protection coordination scheme optimized by a multi-objective hybrid optimization technique. The proposed formulation aims to determine the minimal FCL sizing with minimum investment cost to satisfy the relay coordination constraints at high fault-level buses, irrespective of DG locations and network operating state. User-defined relay characteristics (UDC) are employed to intensify the DOCR coordination performance and obtain minimum operating time, where the conventional inverse relay constants (A&B) are optimized with (TSM & Ipu). The combined UDC relay settings and FCL problem formulation solution attained by MO-hybrid optimization can lessen the escalated electromagnetic stresses, costly switchgear replacement, and relay maloperation. The performance of the proposed technique is assessed by implementing it on the radial (IEEE-33 Bus) and meshed (IEEE 30-Bus) DNs with optimized FCL sizing and relay settings. The optimal results demonstrate the effectiveness of the proposed technique in maintaining the relay coordination performance in the presence of DGs and FCL under an ON/OFF grid connection.

Hardware alarms reduction in Radio Base Stations by forecasting Power Supply Units headroom

Power Supply Units (PSUs) are the components that supply Radio Base Stations (RBSs) with electric power, making it an essential unit for mobile communication networks. A power supply malfunction is critical and must be resolved, but immediate troubleshooting could result in additional operational costs. Based on the prediction of PSU usage by an advanced generalized additive model for time series forecasting called Prophet, the PSU power headroom is derived and the maintenance schedule is proposed, which depends on the severity of demand for power. The safety criteria are derived from the critical operational conditions for several consecutive worst-case scenarios. A PSU alarm will only be generated under the most critical circumstances for an RBS, having multiple PSUs, and sent to the Network Operating Center (NOC). This approach not only allows us to better schedule maintenance and keep operational continuity but also to improve the overall energy efficiency and costs. • Proposing a method for alarm handling in power system for Radio Base Stations. • Generating alarms based on a new triggering logic in the severity of the power headroom variation. • Deriving power headroom based on Machine Learning prediction of PSU usage. • Improving the maintenance schedule and overall energy efficiency.

Dispersion compensation using cascaded apodized CFBGs under MTDM transmission technique: Enhanced system performance

This study focuses on compensating chromatic dispersion affecting the propagated signal in a standard single mode optical fibers (SSMFs). We propose a model that consists of an identical four stages cascaded linear chirped apodized fiber Bragg gratings (CFBGs) in a post-compensation scheme under Maximum Time Division Multiplexing (MTDM) technique. MTDM is free of the limitations resulting from the fiber nonlinear effects. It, thus, effectively utilizes optical wavelength and operating in various network of different distances and capacities. Therefore, MTDM is designed to be used in the high-capacity and high-speed transmission systems. The evaluation of the proposed model performance is performed through a comparative study using different connections and the most common apodization functions. This comparative study includes three cases based on the used connection scheme. A 10 Gbps Wavelength Division Multiplexing (WDM) 70 km link is simulated under ordinary operating parameters. Optisystem 7.0 is used for the simulation and evaluation process, in terms of two metrics which are quality factor (Q-factor) and bit error rate (BER). In the pre-compensation scheme, the highest results are: Q-factor = 7.664 and BER = 8.99 × 10–15, using the raised cosine apodization function. Using the raised sine apodization in the post-compensation connection realizes the best performance: Q-factor = 8.58 and BER = 4.77 × 10–18. In the symmetrical-compensation scheme and using the raised sine apodization, the proposed model attains the highest Results: Q-factor = 7.49 and BER = 3.53 × 10–14. The proposed model achieves at least 92.6% improvement in BER and 3.75% in Q-factor over the related works. The study is a simulation work and is performed through Optisystem ver. 7.

Extensive performance analysis of OpenDayLight (ODL) and Open Network Operating System (ONOS) SDN controllers

The term Software Defined Network or SDN is one of the many emerging technologies that has been revolutionizing the concept of networking. By decoupling the Data and Control plane, it has lot to offer in the field of information technology. The Control Plane is regarded as the brain of the network, which is a centralized unit of SDN network along with the controller. Selection of SDN controller is one of the most important task in designing of SDN based Network. Through this paper, we intend to compare two eminent controllers: OpenDayLight and ONOS controllers, according to their efficacy. Mininet, which is meant for demonstrating the simulation of switching and end-devices, has been taken into account. Apart from this, we have used Wireshark Packet Analyser and iperf, which provides real-time traffic flow between Mininet and the Controller. Performance of the controller plays an important role in the network and answers question like how it is going to perform. There are the various factors that helps in evaluating the performance of SDN controller. After analysing, it has been found that ONOS has better performance, with respect to throughput, TCP Window Scaling, TCP/UDP Bandwidth, Burst Rate, Jitter, Goodput, TCP Stevens Graph, Round Trip Time (RTT), and its usability. This paper helps us to understand performance abilities between ONOS and ODL in medium-to-large scale SDN Networks.

Evaluation of the robustness of SDN controllers ONOS and ODL

Software-defined networking relies on a controller as its main element. Therefore, it is critical for the controller to present features that improve the overall network performance while ensuring continuity of service despite failures. OpenDayLight (ODL) and Open Network Operating System (ONOS) are two important open-source distributed controllers. The objective of this study is to evaluate how ODL and ONOS deal with different failure scenarios in both their data and control planes. In the data plane, the evaluation analyzes both link and switch failures and recovers, different flows in reactive and proactive modes. In the distributed control plane throughput and latency are considered when the number of switches and controllers increase, the time to synchronize the network operations among the controllers, the time for a master to recover from failure, and whether network operations are reinstalled after the failure of a master controller. Our evaluation shows that ONOS achieves better results than ODL in the data plane, and ODL surpasses ONOS in the experiments performed in the control plane.

Machine Learning k-Means Cluster Support S-FSCV Algorithm to Estimate Integrated Network Operating State

Machine Learning k-Means Cluster Support S-FSCV Algorithm to Estimate Integrated Network Operating State

Research on Structural Toughness of Railway City Network in Yellow River Basin and Case Study of Zhengzhou 7–20 Rainstorm Disaster

With the gradual networking of inter-city relations and the increase in acute impact and chronic stress, the measurement of the resilience of urban network structures is particularly prominent. Based on the construction of the urban network by passenger train trips in the Yellow River Basin, this paper analyzes and assesses the characteristics of the structural resilience of the urban network, and probes into the network resilience and urban response under the circumstances of node failure and line failure in Zhengzhou. The main conclusions are as follows: (1) The urban network in the Yellow River Basin was clearly hierarchical, with a significant spatial distribution of “low in the north and high in the south”, and the overall characteristics of “robustness” in small areas and “fragility” in large areas. The network connection forms were diversified and open. The network transmission efficiency was high, and the edge cities depended on the core cities with prominent characteristics, and the risk load of regional core cities rose. (2) The network structure was “robust” as it maintained high operational efficiency and connectivity under random attacks. Under deliberate attacks, the city network operated efficiently with a small increase in connectivity before the 60% threshold, and after the threshold, the overall network started to split into many sub-networks, and the network fragmentation gradually increased until the network collapsed. (3) Zhengzhou node failure and line failure states in the Yellow River Basin urban network were resilient, in the sense that when suffering important nodes and lines going down it could still maintain good network operation efficiency, and the core nodes in the impact of natural disasters could adapt to the destructive nature of the network through the urban network structure self-regulation.

A DDoS Vulnerability Analysis System against Distributed SDN Controllers in a Cloud Computing Environment

Software-Defined Networking (SDN) is now a well-established approach in 5G, Internet of Things (IoT) and Cloud Computing. The primary idea behind its immense popularity is the separation of its underlying intelligence from the data-carrying components like routers and switches. The intelligence of the SDN-based networks lies in the central point, popularly known as the SDN controller. It is the central control hub of the SDN-based network, which has full privileges and a global view over the entire network. Providing security to SDN controllers is one such important task. Whenever one wishes to implement SDN into their data center or network, they are required to provide the website to SDN controllers. Several attacks are becoming a hurdle in the exponential growth of SDN, and among all one such attack is a Distributed Denial of Service (DDoS) attack. In a couple of years, several new SDN controllers will be available. Among many, Open Networking Operating System (ONOS) and OpenDayLight (ODL) are two popular SDN controllers laying the foundation for many other controllers. These SDN controllers are now being used by numerous businesses, including Cisco, Juniper, IBM, Google, etc. In this paper, vulnerability analysis is carried out against DDoS attacks on the latest released versions of both ODL and ONOS SDN controllers in real-time cloud data centers. For this, we have considered distributed SDN controllers (located at different locations) on two different clouds (AWS and Azure). These controllers are connected through the Internet and work on different networks. DDoS attacks are bombarded on the distributed SDN controllers, and vulnerability is analyzed. It was observed with experimentation that, under five different scenarios (malicious traffic generated), ODL-3 node cluster controller had performed better than ONOS. In these five different scenarios, the amount of malicious traffic was incregradually increased. It also observed that, in terms of disk utilization, memory utilization, and CPU utilization, the ODL 3-node cluster was way ahead of the SDN controller.

Optical Network Management by ONOS-Based SDN Controller

The possibilities to manage the optical network with a logically centralized SDN control plane based on the Open Network Operating System (ONOS) are investigated. The structure of the controller and its main functional blocks are considered ensuring the collection of information about the state of network elements, the solution of the main control tasks, interaction of control systems built on different technological bases, are considered. The role and place of the open network operating system in the controller structure are shown, the description of the ONOS multilevel architecture in the form of a set of functional modules is given, the purpose and functions of the ONOS subsystems are analyzed, protocols and interfaces making it possible to present the SDN network as a model are described. The peculiarity of the model is that the managed network can be represented as a set of virtual network functions. Therefore, the control process becomes independent of which vendor's equipment was used to build the network, as well as whether the network is built on real physical elements or virtual ones. Using the ONOS allows you to build a logical centralized control plane in the SDN networks. The existing set of functional modules, services and interfaces in the ONOS allows you to perform optical network management tasks. For the further development of the ONOS, it is necessary to develop mathematical models and methods for the optimal solution of control problems in various operating conditions, which will become application-level software modules in the future.

Deep learning-based feature extraction for prediction and interpretation of sharp-wave ripples in the rodent hippocampus.

Local field potential (LFP) deflections and oscillations define hippocampal sharp-wave ripples (SWRs), one of the most synchronous events of the brain. SWRs reflect firing and synaptic current sequences emerging from cognitively relevant neuronal ensembles. While spectral analysis have permitted advances, the surge of ultra-dense recordings now call for new automatic detection strategies. Here, we show how one-dimensional convolutional networks operating over high-density LFP hippocampal recordings allowed for automatic identification of SWR from the rodent hippocampus. When applied without retraining to new datasets and ultra-dense hippocampus-wide recordings, we discovered physiologically relevant processes associated to the emergence of SWR, prompting for novel classification criteria. To gain interpretability, we developed a method to interrogate the operation of the artificial network. We found it relied in feature-based specialization, which permit identification of spatially segregated oscillations and deflections, as well as synchronous population firing typical of replay. Thus, using deep learning-based approaches may change the current heuristic for a better mechanistic interpretation of these relevant neurophysiological events.

P4-TINS: P4-Driven Traffic Isolation for Network Slicing With Bandwidth Guarantee and Management

Network slicing is an essential technology for 5G mobile networks. It partitions network resource logically into multiple isolated slices, each of which can satisfy a suite of network requirements for one specific service. However, it cannot be fulfilled by the current SDN (Software-Defined Networks), since the conventional SDN data-plane technology, OpenFlow, is not flexible enough to offer fine-grained network resource control or queue/packet scheduling. It leads to many research studies developing corresponding solutions on programmable switches. In this work, we focus on the support of the bandwidth guarantee and management for network slices. Although several studies with the similar goal have been proposed, they do not consider interference among different flow types or use the built-in meter for easy deployment on COTS (Commercial Off-The-Shelf) P4 switches. To this end, we first conduct a case study to examine the interference cases. We then propose a solution, designated as P4-TINS (P4-driven Traffic Isolation for Network Slicing), to resolve the interference by isolating different types of traffic flows in priority queues and set the P4 switch’s bucket size based on the time granularity of its bandwidth management operation. It cannot only ensure the guaranteed bandwidth for each slice but also enable coexistent slices to fairly share residual bandwidth. We have confirmed its effectiveness experimentally based on our prototype over an ONOS (Open Network Operating System) controller and a COTS P4 switch.