With the increasing complexity of power system structures and the increasing penetration of renewable energy, driven primarily by the need for decarbonization, power system operation and control ...become challenging. Changes are resulting in an enormous increase in system complexity, wherein the number of active control points in the grid is too high to be managed manually and provide an opportunity for the application of artificial intelligence technology in the power system. For power flow control, many studies have focused on using generation redispatching, load shedding, or demand side management flexibilities. This paper presents a novel reinforcement learning (RL)-based approach for the secure operation of power system via autonomous topology changes considering various constraints. The proposed agent learns from scratch to master power flow control purely from data. It can make autonomous topology changes according to current system conditions to support grid operators in making effective preventive control actions. The state-of-the-art RL algorithm—namely, dueling double deep Q-network with prioritized replay—is adopted to train effective agent for achieving the desired performance. The IEEE 14-bus system is selected to demonstrate the effectiveness and promising performance of the proposed agent controlling power network for up to a month with only nine actions affecting substation configuration.
•DSOs need to take care of the increased power electronics-caused harmonic pollution.•A mathematical model for the assessment of radial distribution networks is given.•Pandapower-based open source ...tool for the (un)balanced harmonic analysis is developed.•The accuracy of the tool is verified against commercial tools on different cases.•The tool is available for running simulations, further verification, and upgrades.
With the increasing integration of new technologies, power system operators are facing new operational and planning challenges. Most of these changes are caused by power electronics devices of low carbon (LC) units, resulting in more frequent violations of limits defined in the standards, such as the unwanted occurrence of higher-order harmonics. These aspects indicate that an open source tool, capable of analyzing and estimating future impacts of the above-mentioned phenomena and technologies, would be of great benefit. The paper presents the development of a Phyton-based open source tool as an extension of the existing pandapower library. The upgrade includes the capability of balanced and unbalanced harmonic analysis for LC impact assessment. The technical background and mathematical formulations implemented in the newly developed tool are explained in detail and benchmarked against existing commercial tools showing high accuracy, i.e., the median deviation between the results calculated by the developed and the commercial tool is no larger than 0.21% in the worst-case scenario. In addition to verification, the developed tool is used for the analysis of a real-world network with a high share of LC technologies. The source code of the tool is made available for verification and future updates.
This study presents an improvement of three phase backward/forward sweep (BFS) power flow calculation algorithm for radial distribution systems. BFS power flow method is an iterative method that is ...usually used for power flow calculations in distribution networks due to its convergence and easy applicability. The improvement of commonly used BFS method is based on using breadth-first search method for creation of modified incidence matrix. Such incidence matrix ensures minimum number of searching for connections between nodes. The result is much faster algorithm without accuracy loss. The calculation duration is especially important for real time calculations in active management of distribution system. Reduction of calculation duration by the proposed method is especially expressed in power flow calculations of unbalanced radial networks such as low voltage networks. The proposed method is tested on several unbalanced distribution networks and compared with commonly used BFS method. Results show that the proposed algorithm is accurate and more efficient than compared method.
Simultaneous optimization of controllers in power systems is a challenging research due to the inherent nonlinearity of such a system. Multi-objective optimization is a useful tool for tuning ...excitation controllers and minimizing oscillations that are described through definition of transient and small-signal stability in power systems. In this paper, a Two-Area-Four-Machine (TAFM) power system model is tested on multiple short circuit and load disturbances. A multi-objective performance analysis is investigated by observing the system's behaviour in different cases involving the no-preference method and a priori method called weighted sum objective. The analysis is done through observation of two different objective functions. First objective function includes the sum of the integral of time-weighted absolute errors of rotor speed differences, generator voltage, and tie-line power transfer. Second objective function observes time domain elements: overshoot, undershoot, and settling time of machines' rotor speeds. Results are compared for two methods combined with four different algorithms to provide better insight into the computational performance of each algorithm and objective search method. Algorithms used for controllers' parametrization include two novel algorithms: multi-objective ant lion optimizer (MOALO) and salp swarm algorithm (MOSSA), and two classic algorithms: multi-objective particle swarm optimization with velocity relaxation (MOVRPSO) and simulated annealing (MOSA).
Process of transmission planning needs to provide the location and type of solution that will ensure quality and security of supply network users. Taking into account the stated requirements, the ...transmission network (TN) must have satisfactory electricity transmission capacities (TC) and it is necessary to determine the technical solutions at an acceptable financial cost. In this paper, a model will be presented how to determine the location and type of investment, taking into account the connection of future power plants, users, development plans of neighbouring countries and the energy strategy of Europe. The model evaluates the possibilities of implementation of high-temperature low sag conductors (HTLS) and compacted overhead transmission lines (OHL) on the existing infrastructure or construction of new transmission lines in the same right of way. The main idea of the presented model is to investigate the influence of a proposed investment based on measurement data taking into account losses and TC of the TN as important factors. In order to increase TC taking into consideration TN losses, a number of possible technical solutions will be investigated.
Reactivation from latent cytomegalovirus (CMV) infection is often associated with conditions of immunosuppression and can result in fatal disease. Whether the maintenance of systemic CMV latency is ...mainly governed by factors of the infected cell or by immune control functions is unknown. Likewise, the putative immune control mechanisms which could prevent the induction and spread of recurrent CMV infection are not clearly identified. We took advantage of latently infected B cell-deficient mice and a sensitive method for virus detection to study CMV reactivation after ablation of lymphocyte subsets. A crucial role of both T lymphocytes and natural killer (NK) cells was demonstrated. Within 5 d after depletion of lymphocytes, productive infection occurred in 50% of mice, and 14 d later 100% of mice exhibited recurrent infection. A hierarchy of immune control functions of CD8(+), NK, and CD4(+) cells was established. Reactivation was rare if only one of the lymphocyte subsets was depleted, but was evident after removal of a further subset, indicating a functional redundancy of control mechanisms. The salivary glands were identified as the site of most rapid virus shedding, followed by the detection of recurrent virus in the lungs, and eventually in the spleen. Our findings document a previously unknown propensity of latent CMV genomes to enter productive infection immediately and with a high frequency after immune cell depletion. The data indicate that only the sustained cellular immune control prevents CMV replication and restricts the viral genome to a systemic state of latency.
The maritime industry is undergoing a profound transformation with the integration of autonomous technologies, which brings new challenges and opportunities for the education and training of ...seafarers. This article aims to examine the evolving landscape of autonomous ships and its impact on maritime education, with a focus on the changing roles and responsibilities of seafarers. The levels of autonomy defined by the International Maritime Organization (IMO) provide a framework for understanding the evolution towards fully autonomous ships and highlight the changing roles and responsibilities of seafarers. Using a systematic review based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA), this study examines maritime education for maritime autonomous surface ships (MASS). Using Scopus, Web of Science (WoS) and Google Scholar, a comprehensive search was conducted to identify relevant studies focusing on seafarer training and the impact of automation in the maritime sector. The analysis included bibliometric assessments, historical reviews and a categorization of research topics. This systematic review contributes to a deeper understanding of the current state and trends in maritime education for autonomous shipping. The findings inform educators and industry stakeholders about the critical aspects of education and training needed to address the challenges and realize the potential benefits of autonomous technologies in the maritime sector. The inclusion of bibliometric analysis enriches the study by providing a comprehensive overview of the researchers.
•Dynamic model of an electric arc furnace (EAF) was developed in Matlab/Simulink.•Model is based on simulating varying resistance of the electric arc taking into account its stochastic behavior.•The ...model was applied for estimation of voltage flicker in power transmission network at the point of common coupling.•Calculations of voltage flicker were compared to measurements obtained from various operating conditions of the EAF.•Influence of short circuit power and switching operating condition of the transmission network on flicker levels.
This paper presents a dynamic model of an electric arc furnace (EAF) developed in Matlab/Simulink environment. Model is based on simulating varying resistance of the electric arc in time-domain while taking into account its stochastic behaviour. The model was applied for estimation of voltage flicker in power transmission network at the point of common coupling caused by operation of EAF. Modelling and simulation of an International Eletrotechnical Commission (IEC) flickermeter were also performed in order to calculate voltage flicker from the simulated EAF voltage. In order to verify the developed EAF model, calculations of voltage flicker were compared to measurements obtained from various operating conditions of the EAF such as boring, melting and refining. Influence of short circuit power and switching operating condition of the transmission network on flicker levels at point of common coupling was investigated.
This article takes a close look at the landscape of global navigation satellite system (GNSS) spoofing. It is well known that automated identification system (AIS) spoofing can be used for electronic ...warfare to conceal military activities in sensitive sea areas; however, recent events suggest that there is a similar interest of spoofing AIS signals for commercial purposes. The shipping industry is currently experiencing an unprecedented period of deceptive practices by tanker operators seeking to evade sanctions. Last year’s announcement of a price cap on Russian crude oil and a new ban on Western companies insuring Russian cargoes is setting the stage for an increase in illegal activity. Our research team identified and documented the AIS position falsification by tankers transporting Russian crude oil in closed ship-to-ship (STS) oil transfers. The identification of the falsified positions is based on the repeated instances of discrepancies between AIS location suggestions and satellite radar imagery indications. Using the data methods at our disposal, we reconstructed the true movements of certain tankers and encountered some surprising behavior. These false ship positions make it clear that we need effective tools and strategies to ensure the reliability and robustness of AISs.
This paper discusses the legal nature of human dignity as well as whether and in what manner it merits consideration in the prison privatization decision-making process. The first chapter grasps the ...complexity of the legal concept of human dignity by analyzing how it is approached - its status, roles and content - in notable international and domestic regulations, soft law, sociological and legal theories. The second chapter discusses the qualitative characteristics of the decision to privatize prisons and argues that it is primarily legal (constitutional) in nature, the importance of agent identity and its effect on conceptual permissibility of prison privatization based on the rationale theory of conceptual limitation to privatizing prisons by Dorfman and Harel, and finally, presents the institutional and human rights aspects of prison privatization as discussed by Barak-Erez and Feeley following the 2009 constitutional review decision of the Supreme Court of the State of Israel which held prison privatization to be unconstitutional. The conclusion attempts to formulate an acceptable legal definition of human dignity, gives a summary of author's opinions, and assesses the influence of presented argumentation on recommendation of prison privatization as long-term or short-term solution for addressing human rights violations with overcrowding as underlying cause.
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