System Restoration Research Articles

Evaluation of system design modifications for full system decontamination of Kori Unit 1

Kori Unit 1 is planning a system decontamination project to reduce radiation exposure of decommissioning workers, prevent the spread of contamination and down-grade the level of classification of radioactive waste. The system decontamination range for Kori Unit 1 will be the entire primary system, including RCS, CVCS and RHRS. Some system design modifications are required for the system decontamination operation. In this paper, major system design modifications were evaluated based on the conditions that system restoration is needed after completion of system decontamination. The major system design modifications are CIDF connection location to system, system decontamination operating pressure control, RCP seal water injection and formation of letdown flow. It was evaluated that there was no negative effect on the system due to the system design modifications. However, as the RCP seal water is injected into the system in the oxidation process, the concentration of the oxidizing agent is diluted. Therefore, the oxidizing agent injection and system decontamination operation procedures should be developed to address the dilution effect of the oxidizing agent. The system design modifications dealt in this paper will be finally confirmed through on-site investigation in the future, and if necessary, the system design modifications will be re-evaluated.

Interaction of Neural Stem Cells (NSCs) and Mesenchymal Stem Cells (MSCs) as a Promising Approach in Brain Study and Nerve Regeneration

Rapid developments in stem cell research in recent years have provided a solid foundation for their use in medicine. Over the last few years, hundreds of clinical trials have been initiated in a wide panel of indications. Disorders and injuries of the nervous system still remain a challenge for the regenerative medicine. Neural stem cells (NSCs) are the optimal cells for the central nervous system restoration as they can differentiate into mature cells and, most importantly, functional neurons and glial cells. However, their application is limited by multiple factors such as difficult access to source material, limited cells number, problematic, long and expensive cultivation in vitro, and ethical considerations. On the other hand, according to the available clinical databases, most of the registered clinical trials involving cell therapies were carried out with the use of mesenchymal stem/stromal/signalling cells (MSCs) obtained from afterbirth or adult human somatic tissues. MSCs are the multipotent cells which can also differentiate into neuron-like and glia-like cells under proper conditions in vitro; however, their main therapeutic effect is more associated with secretory and supportive properties. MSCs, as a natural component of cell niche, affect the environment through immunomodulation as well as through the secretion of the trophic factors. In this review, we discuss various therapeutic strategies and activated mechanisms related to bilateral MSC–NSC interactions, differentiation of MSCs towards the neural cells (subpopulation of crest-derived cells) under the environmental conditions, bioscaffolds, or co-culture with NSCs by recreating the conditions of the neural cell niche.

Rolling optimization of transmission network recovery and load restoration considering hybrid wind-storage system and cold load pickup

A common solution to deal with the stochasticity introduced by fast-ramping wind power integration is to equip wind farms (WFs) with energy storage systems (ESSs) to formulate hybrid WF-ESSs. In addition to leveling off wind power fluctuations during normal operations, a hybrid WF-ESS can be a flexible power source to accumulate the power system restoration. In this paper, we propose a rolling optimization model for transmission network recovery and load restoration considering the contributions of WF-ESSs. The proposed model is formulated as a mixed integer linear programming problem that simultaneously optimizes the amount and location of restorable load blocks as well as the restoration lines. The cold load pickup features of interrupted loads considering the outage duration are modeled in detail. A chance-constrained method is employed to deal with the uncertainty of wind power, and a rolling horizon-based framework is adopted to reduce the influence of forecast error. Case studies are conducted on both New England 39-bus system and part of a provincial power system in China. The results show that the load restoration process can be significantly accelerated by employing the proposed method and contributions of hybrid WF-ESSs to power system restoration are validated.

Optimal Power Systems Restoration Based on Energy Quality and Stability Criteria

Electric power systems (EPS) are exposed to disconnections of their elements, such as transmission lines and generation units, due to meteorological factors or electrical failures. Thus, this research proposes a smart methodology for the re-entry of elements that have been disconnected from the EPS due to unforeseen events. This methodology is based on optimal AC power flows (OPF-AC) which allow verifying the state of variables such as voltage, angular deviation, and power (these variables are monitored in normal and fault conditions). The proposed study considers contingencies N-2, N-3, N-4, and N-5, for which the disconnection of transmission lines and generation units are carried out randomly. The analysis of the EPS after the disconnections of the elements is carried out by means of the contingency index, with which the impact that the disconnections of the elements have on the EPS is verified. In this way, the optimal route is generated to restore the elements that went out of operation, verifying that when the elements re-enter the acceptable limits, voltage and voltage angle are not exceeded. According to the results of the methodology used, it was found that NM contingencies can be applied in the proposed model, in addition to considering stability restrictions, modeled as restrictions on acceptable voltage limits, and a new restriction for the voltage angle between the differences of the bars.

A new approach for generator startup sequence online decision making with a heuristic search algorithm and graph theory

Most system restoration strategies following blackouts are obtained by offline methods, which are efficient in theory. But this may not be the case. A new method is proposed to decide the generator startup sequence during the system restoration. The Monte Carlo tree search algorithm is used to search for the generator to be recovered according to the real-time situation of the power system. All paths from the restored system to the chosen generator are obtained by Depth-First Search. And the K-shortest paths are obtained by Yen’s Algorithm to decide the best restoration path. Then, key constraints are verified. Especially, the constraint on the hot start of generators is considered. Finally, the feasible scheme with the maximum power generation is selected for implementation. In addition, the cranking process of G33 to G32 in the IEEE39-bus test system is taken as an example to illustrate the efficiency of this method. Depth-First Search detects 42 restoration paths, and Yen’s Algorithm selects three most reasonable paths from them, which greatly improves the efficiency of online decision making.

Bayesian Optimization and Hierarchical Forecasting of Non-Weather-Related Electric Power Outages

Power outage prediction is important for planning electric power system response, restoration, and maintenance efforts. It is important for utility managers to understand the impact of outages on the local distribution infrastructure in order to develop appropriate maintenance and resilience measures. Power outage prediction models in literature are often limited in scope, typically tailored to model extreme weather related outage events. While these models are sufficient in predicting widespread outages from adverse weather events, they may fail to capture more frequent, non-weather related outages (NWO). In this study, we explore time series models of NWO by incorporating state-of-the-art techniques that leverage the Prophet model in Bayesian optimization and hierarchical forecasting. After defining a robust metric for NWO (non-weather outage count index, NWOCI), time series forecasting models that leverage advanced preprocessing and forecasting techniques in Kats and Prophet, respectively, were built and tested using six years of daily state- and county-level outage data in Massachusetts (MA). We develop a Prophet model with Bayesian True Parzen Estimator optimization (Prophet-TPE) using state-level outage data and a hierarchical Prophet-Bottom-Up model using county-level data. We find that these forecasting models outperform other Bayesian and hierarchical model combinations of Prophet and Seasonal Autoregressive Integrated Moving Average (SARIMA) models in predicting NWOCI at both county and state levels. Our time series trend decomposition reveals a concerning trend in the growth of NWO in MA. We conclude with a discussion of these observations and possible recommendations for mitigating NWO.

Development of a reversible transformer model for the calculation of inrush currents energizing from higher and lower voltage windings

AbstractTransformers are normally energized from the higher voltage winding. In power system restoration, however, they may be energized from the lower voltage winding. Therefore, a reversible transformer model that is able to accurately calculate inrush currents and some other low‐frequency transients is required regardless of which winding is energized. Although a reversible transformer model based on a topology‐based model that considers magnetic couplings between phases has been proposed, it is difficult to determine the parameters of the model because iron‐core and winding design information are not available in most cases. In addition, the approximation of the design information required when such information is not available does not always hold accurately. In this article, a reversible transformer model that can be composed only from available information such as nameplates and test reports, without using the design information (or the approximation), by using mutually coupled magnetic resistances has been developed. As a result of verification using a 500 VA single‐phase three‐winding transformer, it is indicated that the inrush currents calculated by the developed model are in good agreement with those obtained by the laboratory measurements using the test transformer regardless of which winding is energized.

Multi-Period Restoration Model for Integrated Power-Hydrogen Systems Considering Transportation States

This article proposes an innovative integrated power and hydrogen distribution system (IPHDS) restoration model in response to multiple outages caused by natural disasters. During the restoration, repair crews and mobile battery-carried vehicles are considered to repair faulted lines and support critical power loads. Also, the network reconfiguration is taken into consideration in the restoration model to pick up loads. Besides, to address the different response time of hydrogen and power systems, the aerodynamic law-based dynamic hydrogen flow model is applied in the hydrogen system. The proposed model is presented as a mixed-integer linear program, which is verified on a 33-bus-48-node IPHDS with multiple outages. The present results verify the effectiveness of the proposed method.

Guest Editorial: Enhancing hosting capability for renewable energy generation in active distribution networks

Guest Editorial: Enhancing hosting capability for renewable energy generation in active distribution networks

Advanced extended-term simulation approach with flexible quasisteady-state and dynamic semi-analytical simulation engines

Power system simulations that extend over a time period of minutes, hours, or even longer are called extended-term simulations. As power systems evolve into complex systems with increasing interdependencies and richer dynamic behaviors across a wide range of timescales, extended-term simulation is needed for many power system analysis tasks (e.g., resilience analysis, renewable energy integration, cascading failures), and there is an urgent need for efficient and robust extended-term simulation approaches. The conventional approaches are insufficient for dealing with the extended-term simulation of multi-timescale processes. This paper proposes an extended-term simulation approach based on the semi-analytical simulation (SAS) methodology. Its accuracy and computational efficiency are backed by SAS's high accuracy in event-driven simulation, larger and adaptive time steps, and flexible switching between full-dynamic and quasi-steady-state (QSS) models. We used this proposed extended-term simulation approach to evaluate bulk power system restoration plans, and it demonstrates satisfactory accuracy and efficiency in this complex simulation task.

Learning Sequential Distribution System Restoration via Graph-Reinforcement Learning

A distribution service restoration algorithm as a fundamental resilient paradigm for system operators provides an optimally coordinated, resilient solution to enhance the restoration performance. The restoration problem is formulated to coordinate distribution generators and controllable switches optimally. A model-based control scheme is usually designed to solve this problem, relying on a precise model and resulting in low scalability. To tackle these limitations, this work proposes a graph-reinforcement learning framework for the restoration problem. We link the power system topology with a graph convolutional network, which captures the complex mechanism of network restoration in power networks and understands the mutual interactions among controllable devices. Latent features over graphical power networks produced by graph convolutional layers are exploited to learn the control policy for network restoration using deep reinforcement learning. The solution scalability is guaranteed by modeling distributed generators as agents in a multi-agent environment and a proper pre-training paradigm. Comparative studies on IEEE 123-node and 8500-node test systems demonstrate the performance of the proposed solution.

Distribution System Restoration by Reconfiguration and MG formation Considering Post-Restoration Failure Probability

Recent weather-related disasters experienced worldwide with considerable damages to the interconnected power infrastructure have highlighted the importance and urgency of enhancing the resiliency of the distribution grid. A Resilient distribution grid can withstand and recover from such rare events. Resiliency against extreme events is conceptualized in three distinct stages: prior, during, and after the event. Rapid recovery is a feature of after the event stage. In this paper, restoration strategies to restore maximum loads as quickly as possible are investigated. The proposed approach attempts to restore the critical loads by using tie-switches to reconfigure the network. In the case of isolated areas without the possibility of using upstream utility grid, sectionalizing the grid into several microgrids (MGs) is proposed to improve the system resiliency. The number of isolated MGs is an issue that is required to be correctly determined. So, a new approach is proposed to compromise between amount and reliability of supplied load to find the optimum number of MGs. The proposed method is simulated on the unbalanced IEEE-123 and 37-bus distribution grid with random locations for DERs.

Voltage stability improvement of an Egyptian power grid‐based wind energy system using STATCOM

AbstractThe increase in electricity demand places its focus on renewable energies as sustainable energy resources. Wind energy is one of the most important green energy sources. The doubly fed induction generator (DFIG)‐based wind farm has now gained prominence due to its many advantages, such as variable speed operation and autonomous control of active and reactive power. When the DFIG stator windings are directly connected to the power grid, when a grid fault occurs, some unwanted high current may be produced in the rotor windings, and the protection system will prevent the rotor side converter (RSC) from operating. Therefore, voltage stability is a significant factor in maintaining the DFIG‐based wind farm in operation during grid faults and disturbances. This paper applies a static synchronous compensator (STATCOM) to restore the voltage levels of the Egyptian power grid connected to Al Zafarana‐5th stage wind farm, which is made of 100 Gamesa G52/850 kW DFIG machines. In this paper, the STATCOM is controlled by a proportional integral (PI) and is compared with a STATCOM controlled by fuzzy logic control (FLC). For simulation, the MATLAB/SIMULINK environment is used. Moreover, the simulation results show that STATCOM devices with fuzzy logic controllers improve the effects of grid faults and disturbances such as a single line to ground fault, a line to line fault, voltage sag, and voltage swell as compared with STATCOM with PI controllers. Also, STATCOM devices based on FLC improve the stability and power quality of the system and the power system restoration procedures for the existing and future‐planned wind farms.

Two-Stage MILP Model for Optimal Skeleton-Network Reconfiguration of Power System for Grid-Resilience Enhancement

Skeleton-network reconfiguration is an important task and plays a most important role during power system restoration (PSR) after a blackout. By determining the skeleton network, the power system can be restored as soon as possible to minimize the burden of network reconfiguration. In this paper, a resilience-based skeleton-network reconfiguration (NR) strategy, i.e., a two-stage mixed-integer linear programming (MILP)–based NR strategy for grid-resilience enhancement, is proposed to minimize the impact of emergency power outages on power systems. The start-up sequence for non-black-start generators (NBSGs) and line energization sequences are determined in the first-stage optimization model. A serial restoration constraint and a transient frequency constraint are considered to achieve the serial restoration scheme of NBSGs. Except for the generator power, all the variables attained during the first stage are assumed fixed in the second stage. The second-stage optimization model determines the optimal skeleton network by determining the target transmission lines and critical load pickup during the NR phase. Furthermore, the sets of metrics (i.e., system flexibility, power loss ratio, and recovery time resilience) are presented to determine the grid operational resilience in the skeleton-network reconfiguration. Then, two stages of skeleton-NR are formulated as MILP, and the branch-and-bound method is presented to solve both models. Finally, simulation studies are performed on the two modified power system test cases and the results validate that the proposed strategy can efficiently determine the robust skeleton network for practical and detailed PSR planning.

Цивілізаційна парадигма сталого розвитку

Із позицій цивілізаційної теорії визначено суть концепції сталого розвитку. Виконано аналіз діяльності Організації Об’єднаних Націй (далі – ООН) як глобального модератора процесів переходу глобальної економіки на принципи сталого розвитку, що відображено у Декларації про право на розвиток і Декларації на соціальний прогрес, які були затверджені Генеральною Асамблеєю ООН. Обґрунтовано необхідність кардинальної зміни ціннісних чинників соціального розвитку. Доведено необхідність зміни підходів до взаємодії людини і природи, а важливим завданням соціально-економічного розвитку повинно стати збереження і відновлення природних систем, використання природних ресурсів у межах господарської місткості біосфери. Обґрунтовано необхідність застосування цивілізаційного підходу до формування стратегії сталого розвитку. Встановлено, що принципи сталого розвитку цілком вписуються в концепцію “виклик – відгук”, запропоновану А. Тойнбі. Запропоновано об’єднати всі трактування поняття “сталий розвиток” визначенням поняття цивілізаційного розвитку, поданого А. Тойнбі: розвиток відбувається тоді, коли відгук, на той чи інший виклик є не лише успішним, а й спричиняє подальший виклик, на який знову надходить успішний відгук.

Distribution system restoration after extreme events considering distributed generators and static energy storage systems with mobile energy storage systems dispatch in transportation systems

After extreme events and major outages in the distribution system (DS), restoring the de-energized loads becomes the priority of network operators. In such conditions, static energy storage systems (SESSs) and mobile energy storage systems (MESSs) are critical resources for DS outage management to fast restoration of the network. Finding the de-energized islands and associated loads, investigate the optimal load pickup sequence along optimal dispatch of energy storage systems (ESSs) are the main challenges of network outage management in outage duration. Motivated by these challenges, this paper presents a new load restoration strategy by black start distributed generators and non-black start distributed generators and enhances black start service considering static/mobile energy storage systems, and interdependency between transportation and power grids. To this end, a new method is presented, which indicates the formed de-energized islands and their loads after fault occurrence in the network. This method also can check the radiality constraint of the network. In addition, in this paper, a new algorithm is presented that evaluated the best load pickup sequence by considering the priorities of the loads. Various case studies and scenarios are carried out in an IEEE 123-bus distribution system considering the different numbers of faulted lines, damaged roads MESSs and SESSs. Simulation results confirm the efficiency of the proposed restoration strategy.

Resilient scheduling of MESSs and RCs for distribution system restoration considering the forced cut-off of wind power

Mobile energy storage systems (MESSs), wind power and repair crews (RCs) are usually coordinated to restore distribution systems damaged by hurricanes. However, the forced cut-off of wind power occurs as wind speed exceeds the cut-off value, which can lead to sudden power shortage. To address this challenge, this paper proposes a restoration approach considering wind power cut-off to enhance distribution system resilience. The resilient coordination approach takes advantage of MESSs, RCs, network reconfiguration and distributed generators (DGs) to restore the outage distribution system. Considering the uncertainty of wind power cut-off, the proposed method is formulated as a two-stage model on two timescales. On the long timescale, MESSs, RCs, DGs and line switches are robustly optimized to reduce critical load loss considering wind power cut-off. On the short timescale, the output decisions of MESSs and DGs are re-dispatched to compensate for the first-stage strategies after uncertainties realization. In addition, the nonlinear output curve of wind power is linearized in mixed integer linear programming form to facilitate the solution of the robust model. Finally, the modified IEEE-69 distribution system is employed to verify the proposed method. Simulation results show that the proposed method can increase the amount of load restoration by 24.1%.

Состояние и перспективы развития мелиорации в Амурской области

The reclamation complex of the region, after a long period of uncertainty, is among the priorities of agricultural development. The article deals with the problems of land reclamation, which acts as a means of ensuring the sustainable development of the agro-industrial complex of the region, since land reclamation plays a crucial role in increasing the fertility of developed lands and crop yields. However, reclamation systems need constant maintenance. It is noted that forest reclamation is insufficiently developed in the region. The purpose of the study is to analyze the current state of land reclamation in the Amur region. The study was conducted in 2018 – 2021 in the Amur region. It has been established that the majority of reclamation systems are in unsatisfactory condition due to a long service life, lack of repair and maintenance, as well as great wear and tear. As a result of the conducted research, the necessity of restoration and reconstruction of the reclamation systems of the region was established. The ways of development of land reclamation on the basis of restoration, repair, reconstruction and construction of new land reclamation systems are outlined. An example of the reconstruction of the reclamation Gilchinsk drainage system and the results of this reconstruction are given, which are expressed in the fact that agricultural work began to be carried out in optimal agrotechnical terms, regardless of weather conditions, and farmers receive stable high yields of agricultural crops. It was noted that it became necessary to pay attention to the design and construction of land reclamation. The modern approach to the survey of reclamation systems, the main directions of repair of concrete structures of reclamation structures are considered. The subject methods of economics, ecology, principles: diversity of forms are used. To conduct this study, information data from websites and other open sources were used.

Application of Flower Pollination Algorithm for Solving Complex Large‐Scale Power System Restoration Problem Using PDFF Controllers

Automatic Generation Control (AGC) in modern power systems is getting complex, due to intermittency in the output power of multiple sources along with considerable digressions in the loads and system parameters. To address this problem, this paper proposes an approach to calculate Power System Restoration Indices (PSRI) of a 2‐area thermal‐hydro restructured power system. This study also highlights the necessary ancillary service requirements for the system under a deregulated environment to cater to large‐scale power failures and entire system outages. An abrupt change in consumer load demands and disturbances in any control region (area) of a multiarea (interrelated) system causes severe fluctuations in frequency and interarea power exchanges. However, simple Proportional and Integral (PI) controllers are most prevalent in the literature to effectively resolve AGC issues, while its integral gain is smaller due to the larger overshoot in transient performance. Therefore, an attempt has been made with a novel control strategy, known as the pseudoderivative feedforward with feedback (PDFF) controller, is developed to keep the interarea power exchanges and the frequency to the specified limits after load changes. A PDFF controller is designed and implemented using the flower pollination algorithm (FPA) to obtain optimal dynamic performance for different types of potential power flows in a restructured power system under investigation. The proposed PDFF controller localizes the zero at an optimal place that reduces the rise time of the step‐response to reduce the excessive overshoot and gives much better dynamic performances as compared to the PI control structure. The Integral Square Error (ISE) is considered as a performance criterion to derive the optimized gain of the PDFF control structure using FPA. Different PSRI are computed based on the transient response of the 2‐area deregulated multisource system and different restoration measures to be taken are also discussed. The simulation results clearly show that the proposed approach is very powerful in decreasing the frequency and tie‐power digressions under different load perturbations.

К ВОПРОСУ ПЕРЕХОДА ТЕКСТИЛЬНОЙ ПРОМЫШЛЕННОСТИ К ЗАМКНУТОЙ ЭКОЛОГИЧНОЙ БИЗНЕС-МОДЕЛИ РАЗВИТИЯ

The article is devoted to the analysis of modern directions of the process of transition of the textile industry from a linear to a more environmentally friendly closed model of economic development, in particular on the example of the EU countries. The main institutions and mechanisms that support environmental innovations are considered. The European Resource Efficiency Center provides assistance to small and medium-sized businesses in the transition to a global economic model of production through more efficient use of natural resources, reducing harmful emissions into the environment and reducing transport costs. To fundamentally change the trajectory of the development of the textile industry, it is necessary to rethink many aspects of the current model and the entire life cycle of the production and operation of textiles. In the conditions of "fast fashion" with the help of aggressive advertising of manufacturers, the demand for cheap clothes is artificially heated up, and this increases the number of landfills of discarded textiles. The circular economic model is based primarily on the reuse of raw materials, finished products and renewable resources. Experts believe that the circular economy is based on three main principles: maximum conservation of raw materials and finished products, waste-free production, environmentally friendly and restoration of natural systems. The basis of such a model is digital technologies, which allow to speed up and ensure the flexibility of processes at all stages of the production cycle. It is believed that in 10 years, 90 % of buyers, when choosing and buying a product, will pay attention primarily to the reputation of the company (brand) [1]. In the article, from the point of view of a systematic approach, eco-innovations financed in the EU countries are considered at the main stages of the life cycle of any textile product, starting from the stage of preparation of initial textile raw materials, production and finishing of fabrics, cutting and sewing products, and ending with the stage of operation of ready-made clothes. The analysis of modern innovations is carried out, which makes it possible to increase the environmental friendliness of each stage of the life cycle of a textile product in terms of efficiency. At the same time, such a criterion as the size of the carbon footprint was taken as a basis. The effect of extending the life cycle of one product on the amount of harmful emissions is considered. The main directions of digitalization of the main stages of the production of textile products are given. Proposals have also been developed for the use of textile waste at the stage of cutting products