Grid Elements Research Articles

Maintaining flexibility in smart grid consumption through deep learning and deep reinforcement learning

The smart grid concept is key to the energy revolution that has been taking place in recent years. Smart Grids have been present in energy research since their emergence. However, the scarcity of data from different energy sources, hardware power, or co-simulation environments has hindered their development. With advances in multi-agent-based systems, the possibility of simulating the behavior of different energy sources, combining real building consumption, and simulated data, storage batteries and vehicle charging points, has opened up. This development has resulted in much research published using both simulated and physical data. All these investigations show that the main problem is that the machine learning algorithms do not fully match the real behavior, it is complex to use them to replicate the different actions to be performed. This paper aims to combine the approach of behavior prediction with state-of-the-art techniques, such as deep learning and deep reinforcement learning, to simulate unknown or critical system scenarios. A very important element in smart grids is the possibility of maintaining consumption within specific ranges (flexibility). For this purpose, we have made use of Tensorflow libraries that predict energy consumption and deep reinforcement learning to select the optimal actions to be performed in our system. The developed platform is flexible enough to include new technologies such as smart batteries, electric vehicles, etc., and it is oriented to real-time operation, being applied in an on-going real project such as the European ebalance-plus project.11Ebalance-plus: https://www.ebalanceplus.eu.

Critical Data Visualization to Enhance Protection Schemes for State Estimation

Intelligent electrical power grids, widely referred to as smart grids (SGs), rely on digital technology resources, especially communication and measurement devices, becoming a cyber-physical energy system. Massive data flow between grid elements makes smart grids more vulnerable to cyber-attacks. Power system state estimation (SE)—an essential function of energy management systems—is one of these data integrity attacks’ targets. Integrity validation routines can fail when insufficient redundancy levels are reached, and spurious data occur. These levels are associated with critical data, i.e., those whose unavailability makes the grid unobservable. Data redundancy is a metric that gives a precarious indication that SE can run. Alternatively, it is more appropriate to quantify this function strength concerning its results’ reliability, which can be achieved by criticality analysis (CA). This paper proposes a novel approach to visualize the results of an extensive CA through representative graphs; they facilitate understanding the usefulness of CA. Critical sets of measurements are generalized, and several metrics are proposed to reveal measuring system vulnerabilities, assisting the design of protection schemes to resist cyber-attacks. Simulations attained on the IEEE-30bus system evince significant improvements in the interpretation/use of CA.

On a Flow Around a Cylinder Over Uneven Bottom

A plane problem of a potential fluid flow around a cylinder of arbitrary section over an uneven bottom with a flow velocity at infinity directed parallel to the bottom is considered. The circulation of the velocity field is determined from Goldshtik’s postulate: the maximum velocity on the contour of the cylinder must be minimal. Two numerical schemes of the boundary element method are developed for solving this problem. The first scheme determines the flow on a bounded but arbitrarily defined bottom surface. The second scheme determines the flow around a contour in a half plane. The comparison of calculations using these numerical schemes with the exact solutions shows the convergence of the method as the grid elements increase. The pressure on the cylinder surface and on the bottom obtained using numerical calculations by the–model is compared with experimental data. Streamlines are also compared taking into account the separation region.

D-q Small-Signal Model for Grid-Forming MMC and Its Application in Electromagnetic-Transient Simulations

The modular multilevel converter (MMC) is a keystone of modern energy transmission systems. Consequently, there is an ongoing pursue for mathematical models to represent it under different configurations and control approaches. In short, this paper introduces an analytical Thévenin-equivalent model for representing the MMC when it is controlled with inner current- and an outer voltage-loop altogether. The model is based on a linearized representation of the converter and conveys the dynamics of passive components, such as submodule capacitors and arm reactors, as well as both control loops. Besides that, the proposed model is divided into a close-loop transfer matrix and the equivalent impedance matrix, both of which represent the relationships between the ac-side dq voltages and currents. We also propose a framework for implementing electromagnetic–transient simulations using the impedance model of this power electronic converter. The framework reduces a multi-bus power grid to a multi-input multi-output (MIMO) feedback system where impedance/admittance matrices of the MMC and other grid elements compose its loops. For validation purposes, it is considered a three-bus power grid comprising one MMC and another two grid-connected VSC. The proposed model was validated by comparing its results with a switching-level PSCAD model of the system.

Spatio-Temporal Differentiation and Driving Factors of Carbon Storage in Cultivated Land-Use Transition

Revealing the response of carbon storage to cultivated land-use transition (CLUT) and identifying its driving factors are of great significance for maintaining ecosystem stability and promoting regional carbon peak and carbon neutrality goals. Given the knowledge gap regarding the driving factors of carbon storage in CLUT, this study takes the Songhua River Basin in the black soil region of China as the case study area. The study aimed to reveal the spatial–temporal heterogeneity of carbon storage in CLUT based on the grid element method and carbon storage density. In addition, the driving factors were demonstrated using the geodetector model. The results show that the cultivated land area gradually decreased from 1990 to 2020, and the transition between cultivated and construction land was the most significant. The carbon storage in cultivated land-use transitions showed a substantial decreasing trend. The conversion of cultivated land to construction land resulted in the loss of 130,443,200 tons of carbon reserves. Moreover, the transformation from unused land to cultivated land led the highest increase in carbon storage, which increased by 29,334,600 tons. The gravity center of carbon storage was stable, moving 28.77 km to the northeast between 1990 and 2020. Conversely, the spatial structure of carbon storage showed a transformation trend from multicore fragmentation to mononuclear agglomeration, with obvious regional accumulation, a weakened degree of fragmentation, and uniform distribution. Carbon reserves increased by 388,600 tons from 1990 to 2000, and carbon reserves lost 60,121,700 tons from 2010 to 2020, nearly 155.700 times. The mean annual rainfall was the main carbon storage factor. The interaction between mean annual rainfall and land-use intensity had strong explanatory power, and the spatial heterogeneity of carbon storage resulted from multiple factors.

Structure and evolution of a tidally heated star

Context. The shearing motion of tidal flows that are excited in non-equilibrium binary stars transform kinetic energy into heat via a process referred to as tidal heating. Aims. We aim to explore the way tidal heating affects the stellar structure. Methods. We used the TIDES code, which solves the equations of motion of the three-dimensional (3D) grid of volume elements that conform multiple layers of a rotating binary star to obtain an instantaneous value for the angular velocity, ω″, as a function of position in the presence of gravitational, centrifugal, Coriolis, gas pressure, and viscous forces. The released energy, Ė, was computed using a prescription for turbulent viscosity that depends on the instantaneous velocity gradients. The Ė values for each radius were injected into a MESA stellar structure calculation. The method is illustrated for a 1.0 + 0.8 M⊙ binary system, with an orbital period of P = 1.44 d and departures from synchronous rotation of 5% and 10%. Results. Heated models have a larger radius and surface luminosity, a smaller surface convection zone, and lower nuclear reaction rates than the equivalent standard stellar models, and their evolutionary tracks extend to higher temperatures. The magnitude of these effects depends on the amount of injected energy, which, for a fixed set of stellar, rotation and orbital parameters, depends on the perturbed star’s density structure and turbulent viscosity. Conclusions. Tidal heating offers a possible alternative for describing phenomena such as bloated or overluminous binary components, age discrepancies, and aspherical mass ejection, as well as the extended main sequence turnoff in clusters. However, establishing its actual role requires 3D stellar structure models commensurate with the nonspherically symmetric properties of tidal perturbations.

Testing of Selected Surge Protection Devices in the Context of the Possibility of Ensuring the Reliability of Power Grids

The paper aims to analyze the parameters of prototypes of new overvoltage protection devices for power grids—a multi-chamber insulator arrester (MCA) and a long flashover arrester (LFA). The article presents the research results on determining the actual MCA and LFA impact characteristics. Moreover, the results were compared to assess the effectiveness of the overvoltage protection devices. The research results presented in this article will supplement missing information about the devices. They will make it possible to evaluate the possibility of using overvoltage protection devices for a new type of spark gap based on a multi-segment system in high-voltage networks of a specific country. The analysis of its properties against the background of atmospheric overvoltages and their impact on high voltage lines will be carried out by assessing the effectiveness of the tested overvoltage protection device in laboratory conditions. The tests will also be carried out by applying standardized lightning and switching surges to the tested device to map the overvoltage processes on the power grid elements. Two different generators will be used for this purpose. The proposed research will also allow learning about the influence of structural elements on the operation of the tested devices.

Choosing the optimal mandible position for inferior alveolar nerve block (IANB) using finite element analysis

BackgroundOne of the most popular methods of local anesthesia in dentistry, inferior alveolar nerve block (IANB) involves the blockade of the inferior alveolar nerve (IAN) and lingual nerve (LN) in the pterygomandibular space. Despite the large number of works describing the contents of this space, the spatial displacements of the anatomical structures of this area at different positions of the mandible have not been sufficiently studied. The aim of our study was to study the spatial movements of the IAN and inferior alveolar artery (IAA) at various positions of the mandible using computer simulation and finite element analysis to find the safest way to conduct IANB. Materials and methodsReverse engineering was used to create a model of the cranial base and the mandible based on computed tomography (CT) data obtained from patient N (male, 24 years old), the arteries of the head and neck were designed from the data of multiphase angiography of patient M (female, 61 years old). Masticatory muscles, sphenomandibular ligament, temporomandibular joint and mandibular nerve were modeled in the SolidWorks software package based on an open database of anatomical structures. The finite element grid was generated in the Solidworks software.In the first series of experiments, the displacement of the mandible was modeled along the vertical axis down by 48 mm (maximum opening of the mouth), in the second series, the jaw was displaced vertically by 48 mm with a simultaneous transversal movement of 10 mm, in the third series, the jaw was displaced along the vertical axis down by 34 mm and transversally by 22 mm. ResultsThe largest distance between IAN and IAA was noted in the third series of experiments. The distance between the nerve and the vessel was minimal in the first series, with an open mouth without lateral displacements. ConclusionThe generated computer model opens new possibilities for studying the dynamic anatomy of the pterygomandibular space. The results of this study can be used for further experimental and clinical trials to find the safest approach to the implementation of IANB, as well as applied in the practice of the educational process.

Numerical Construction of the Transform of the Kernel of the Integral Representation of the Poincaré–Steklov Operator for an Elastic Strip

For an isotropic stratified elastic strip we consider the Poincaré–Steklov operator that maps normal stresses into normal displacements on part of the boundary. A new approach is proposed for constructing the transform of the kernel of the integral representation of this operator. A variational formulation of the boundary value problem for the transforms of displacements is obtained. A definition is given and the existence and uniqueness are proved for a generalized solution of the problem. An iteration method for solving variational equations is constructed, and conditions for its convergence are obtained based on the contraction mapping principle. The variational equations are approximated by the finite element method. As a result, at each step of the iteration method, it is required to solve two independent systems of linear algebraic equations, which are solved using the tridiagonal matrix algorithm. A heuristic algorithm is proposed for choosing the sequence of parameters of the iteration method that ensures its convergence. Verification of the developed computational algorithm is carried out, and recommendations on the use of adaptive finite element grids are given

Informing Streetscape Design with Citizen Perceptions of Safety and Place: An Immersive Virtual Environment E-Participation Method.

As our cities grow, it is important to develop policies and streetscape designs that provide pedestrians with safe comfortable walking conditions and acknowledge the challenges involved in making urban places feel liveable and safe while understanding the critical role of streets around busy destinations. To understand these challenges at a nuanced, human level, new methods of citizen engagement are needed. This paper outlines the development and application of a new citizen perception collection method, using immersive virtual environments (IVE), coupled with an interactive emoji affective activation-pleasure grid and digital slider elements, embedded within an online e-participation survey to quantify, and rank the impact of individual (single-variable) urban design elements and safe system treatments on pedestrians' perceptions of safety and place. The results demonstrate the effectiveness of this method for providing detailed, interrogable, scalable citizen perception data of a variety of urban street design elements and safe system treatments, which allows a statistical analysis of responses and prioritization of the most effective pedestrian-oriented interventions for maintaining or enhancing street vibrancy and liveability. Our IVE e-participation approach is an important contribution to forming a better understanding of streetscapes and provides a valuable method for urban designers and transport planners to prioritise different streetscape place and safety approaches.

Dynamics features of biological rheology in mass species and thermal energy utilizing two viscosity models over heated disc

In this research, heat energy in the Synovial liquid model is discussed over a heated disk involving external heating source and thermal radiation incorporating two viscosity models with magneto-hydrodynamic inspiration. The concept of (BL) boundary layer is imposed to develop the conservation laws for Synovial liquid with thermal transportation in terms of coupled PDEs. The developed PDEs (partial differential equations) are highly nonlinear, complex and coupled, which are reduced into ODEs (ordinary differential equations) with the help of suitable transformation. The converted ODEs (ordinary equations) are solved numerically via finite element scheme (FES) and grid independent examination is established for three hundred elements. The involvement of numerous emerging parameters has been sketched for velocity and temperature fields. Moreover, heat and mass transfer coefficients are computed numerically and the impact of several involved parameters is discussed. The grid independent survey is established against three hundred elements, which is necessary for a convergent solution. Moreover, augmenting values of Weissenberg number retards the fluid velocity. Temperature field depreciates against escalating values of Prandtl number. Influences of parameters on friction among joints are studied which is utilized to investigate lubricant nature in fluids.

Параметрические исследования течений в микросоплах

The work is devoted to parametric investigations of the krypton flow in a conical micronozzle when flowing into a region with low pressure. The features of the flows are studied at various values of the stagnation pressure in the pre-nozzle volume, including the occurrence of a condensed phase in the flow. Mathematical modeling was carried out on the basis of a numerical solution of the complete system of Navier-Stokes equations, supplemented by the equation for the mass fraction of the condensate. The mathematical model takes into account the change in the coefficients of dynamic viscosity and thermal conductivity depending on the gas temperature. The problem was solved by the control volume method on a block-structured regular grid of quadrangular elements using schemes of the second order of accuracy. The equations were integrated with respect to time using the Runge-Kutta method. The calculations were carried out at stagnation pressures of 5, 10, and 15 atm for single-phase and two-phase flows. The distribution fields of temperature and Mach number in the nozzle and in the space behind it are presented. The axial distribution of pressure, temperature, and Mach number has been studied. It is shown that in the case of a single-phase flow, self-similarity of gas flows is observed. The pressure fields were similar, but in a dimensionless form they coincided to each other. In this case, the identity of the velocity and temperature fields was observed at different values of the stagnation pressure. The self-similarity of the flow is violated in the zone of formation of condensed particles. The dimensions of the zones of local temperature increase, as well as the intensity of heat release, depend on the given stagnation pressure, which is reflected in the velocity characteristics of the flow.

Моделирование кинетики нагревания подложки при распылении сэндвич-мишени медь-титан

This study focuses on the special aspects of the heat flow formation during the sputtering of a sandwich target with an internal copper plate and an external titanium one in argon. The kinetics of the heat flow generated by the external plate was determined by the numerical solution of the two-dimensional uniform Fourier’s equation with a set of boundary and zero initial conditions. The Heat Transfer Module of the COMSOL Multiphysics software was used for numerical calculations. In calculations, the grid element size was chosen to be 3.64 mm, which ensures a calculation error of ≤ 5 %. Solving the Fourier’s equation in the time range of 0…500 s with a step of 1 s resulted in a set of the surface temperature distributions of the external plate. When studying heat flows, the external plate was presented as a set of concentric radiation sources with a constant surface temperature. The central source had the shape of a disk, all the others were ring-shaped. The geometric dimensions of the sources and their temperatures were determined by solving the problem of stepwise approximation of the external plate’s surface temperature distribution with a relative error of 10 %. This article provides calculation results for power of 1,000 W and total relative area of the cutouts of 0.25. The comparison of calculated and experimental data is presented.

Asymmetry induces critical desynchronization of power grids.

Dynamical stability of the synchronous regime remains a challenging problem for secure functioning of power grids. Based on the symmetric circular model [Hellmann et al., Nat. Commun. 11, 592 (2020)], we demonstrate that the grid stability can be destroyed by elementary violations (motifs) of the network architecture, such as cutting a connection between any two nodes or removing a generator or a consumer. We describe the mechanism for the cascading failure in each of the damaging case and show that the desynchronization starts with the frequency deviation of the neighboring grid elements followed by the cascading splitting of the others, distant elements, and ending eventually in the bi-modal or a partially desynchronized state. Our findings reveal that symmetric topology underlines stability of the power grids, while local damaging can cause a fatal blackout.

Intensification of heat-exchange of a direct-flow steam boiler of a coil type based on an educational laboratory stand

In the work under consideration, using an experimental stand formed by a cylindrical coil, the modes of air movement through the flue of a ramjet steam boiler were investigated. Experimental studies have revealed shortcomings in the operation of a direct-flow steam boiler and proposed ways to increase heat transfer in a steam boiler by turbulizing the gas-air flow in the convective part of the boiler flue. The Ansys programmable engineering environment was used to simulate the heat exchange between waste gases and water in the heat exchanger. The Ansys SpaceClaim program was used to design the geometric model. Finite element grid was created using the Ansys Icem CFD program. In the process of creation, materials were selected and designated for each part of the model, water and steam temperatures inside the heat exchanger, exhaust gas temperature, boundary conditions and heat exchange conditions between them were also set. After entering all the parameters the model calculations were carried out and the results were presented in the form of a temperature distribution diagram. In conclusion, a variant of further research of aerodynamic processes in a ramjet steam boiler and a demonstration of the selected option were presented.

Variational discretization of one-dimensional elliptic optimal control problems with BV functions based on the mixed formulation

<p style='text-indent:20px;'>We consider optimal control of an elliptic two-point boundary value problem governed by functions of bounded variation (BV). The cost functional is composed of a tracking term for the state and the BV-seminorm of the control. We use the mixed formulation for the state equation together with the variational discretization approach, where we use the classical lowest order Raviart-Thomas finite elements for the state equation. Consequently the variational discrete control is a piecewise constant function over the finite element grid. We prove error estimates for the variational discretization approach in combination with the mixed formulation of the state equation and confirm our analytical findings with numerical experiments.</p>

Ground Slope Stability Analysis

The article analyzes the engineering and geological conditions of the right bank, which is in a state of dynamic equilibrium, of the Oka River. Calculation schemes have been compiled to perform calculations of the total static stability of the slope for two calculated cases in the existing natural state and taking into account the water saturation of the water-bearing rocks, the boundaries of the landslide zone for various cases have been determined. The article identifies possible risks, analyzes the main models of the behavior of the soil base taking into account negative factors, calculates the stability of soil massifs using various known methods. The geometric scheme of the computational model was built on transverse profiles. The width of the calculated area was chosen in such a way that there were no changes in the stress-strain state of the array due to the introduction of artificial boundary conditions along the edges of the finite element grid. The method of calculating stability based on numerical modeling programs by reducing strength characteristics has a number of advantages over the traditionally used methods of calculating stability based on the equations of limiting equilibrium. Based on the results of calculations, the boundaries of the landslide zone for various cases were determined by the method of circular cylindrical sliding surfaces (SAM). A potential landslide zone has been identified, including residential development. Based on the calculations performed, it is proposed to provide alternative measures to ensure the safety of buildings falling into a landslide zone to ensure reliable fastening and minimal impact on the existing slope.

ARMORED HULLS OF DOMESTIC ARMORED PERSONNEL CARRIERS: COMPUTER AND MOCK-UP MODELING OF DYNAMIC PROPERTIES

At the stage of design research of armored bodies of lightly armored vehicles it is extremely important to determine the range of their natural frequencies and natural forms of oscillation. For this purpose, the finite element method is usually used. It is necessary to substantiate the parameters of the finite element model, which provide an acceptable level of accuracy of numerical modeling of dynamic properties of this type of structures. For this purpose, data from parallel numerical and experimental studies of the mock-up of the armored hull of the armored personnel carrier are used. The mock-up of the upper projection of the armored hull is made in the appropriate scale. The material is sheet steel. This mock-up is subjected to dynamic excitation on a vibrating table. Resonant excitation frequencies are recorded, as well as the natural vibration forms. Shock-pulse excitation of the armored hull’s mock-up was also performed. The response to this excitation is recorded using accelerometers. Then, the spectrum of natural vibration frequencies is determined from these oscillograms. In parallel, numerical modeling of natural frequencies and natural vibration forms of the armored hull’s mock-up is carried out. After that, the results of numerical and experimental studies are compared. By varying the parameters of the finite element model, a satisfactory correspondence between the results of numerical calculations and experimental measurements is achieved. In particular, the following are determined: the acceptable type of used finite elements; the number of finite elements required to satisfy the accuracy of numerical modeling of the dynamic properties of similar structures; zones of the recommended thickening-rarefaction of a grid of finite elements, etc. According to the research results, the parameters of finite-element models have been established, which can be used to study the dynamic processes and properties of full-scale armored hulls of lightly armored vehicles.
 Keywords: lightly armored vehicle, mock-up, natural frequency, spectrum of natural vibration frequencies

Research and Development of Criterial Correlations for the Optimal Grid Element Size Used for RANS Flow Simulation in Single and Compound Channels

At present, software products for numerical simulation of fluid dynamics problems (ANSYS Fluent, Ansys CFX, Star CCM, Comsol, etc.) problems are widely used. These software products are mainly based on the numerical solution of the Navier–Stokes equations, the most common and computationally easy method of solving, which is Reynolds averaging (RANS), and further closing the system using semi-empirical turbulence models. Currently, there are many modeling methods and turbulence models; however, there are no generalized recommendations for setting up grid models for modeling flows, while for practical use both the correct mathematical models and the setting of the computational grid are important. In particular, there are no generalized recommendations on the choice of scale of global elements of grid models for typical single channels. This work is devoted to the development and study of relations for a priori estimation of the parameters of a grid model in relation to solving hydrodynamic problems with fluid flow in channels. The paper proposes the introduction of a generalized grid convergence criterion for single channels at high Reynolds numbers. As single channels, a channel with a sudden expansion, a channel with a sudden contraction, and diffuser channels with different opening angles are considered. Based on the results of variant calculations of typical single channels at various Reynolds numbers and various geometric parameters, generalized criterion correlations were obtained to find dimensionless linear scales of grid elements relative to the hydrodynamic characteristics of the flow in the channel. Variant calculations of the compound channel were investigated, which showed the adequacy of correlations proposed.

Алгоритм работы устройства минимизации потерь электроэнергии и токовой загрузки электросетевых элементов энергосистемы

Now there is a continuous increase in loads in electric networks that are undergoing aging of electric grid equipment. These factors lead to a large increase in electricity losses in electrical networks, as well as to a decrease in the current-carrying capacity of electrical network elements. Therefore, the issue of the need to minimize the loss of electrical energy, as well as reduce the current load of network elements, in order to increase its throughput, is becoming more and more acute. One of the most effective ways to reduce power losses and reduce the current load of power grid elements is to regulate the voltage at the nodes of the electrical network by means of power-factor correction unit. However, in order to solve the problems of reducing power losses and current loading of network elements using power-factor correction unit, it is necessary to develop and implement new effective means and algorithms for voltage control, which will allow real-time monitoring of the state of the network and voltage control in the network to achieve the goals.