DIGITAL MODEL OF BOILER HEAT BALANCE

The normative method (NM) of boilers thermal calculation, repeatedly confirmed and refined, contains the structure of ideas and methods that were retained and adapted during the transition to digital technologies. As applied to the analysis of the heat balance of a boiler with flare furnaces, this required the transformation of a large array of initial and reference data, which cannot be applied unchanged when using a computer. This applies to graphical and tabular data, which form up to 80 % of the volume of NM. To obtain the correlation dependences, the authors use a simple and reliable method of unknown coefficients with the inclusion of a verification algorithm, in the case of equidistant arguments these are the Gregory-Newton coefficients. As shown by a preliminary analysis, for almost all dependencies a polynomial of the second degreesometimes replaced by two polynomials is sufficient. By varying the determining factors in the range of nominal values ±20 %, the model response was obtained in the form of a change in fuel consumption. Quantitatively, all material corre-sponds to the normative data, is presented in digital format and methodically corresponds to the Mathcad-15 package. In contrast to the well-known works in this area, all factors affecting the heat balance are represented by approximations taking into account the variability of temperature and pressure.

Reconfiguring Distribution Grids

Optimizing the grid structure becomes necessary in case of post-emergency power restoration or when overloaded. In normal operation, distribution grid parameters are adjusted to reduce the overload and the electricity losses; reconfiguration is not considered. The grid topology is reconfigurable by solving the optimization problem by the branch-and-bound algorithm subject to keeping the parameters within their acceptable limits in the context of line resistance, electricity losses, and power flows for all possible grid layouts. Simulation of a 10-kV distribution grid with four power centers shows that reconfiguring reduces power consumption by 2.9% and the inline active power losses by 256 kW. In this case study, reconfiguring has helped keep the voltage within the acceptable range while not overloading the lines. This study shows the proposed approach is suitable for dynamic grid reconfiguration as a way to reduce the overload and the electricity losses; at the same time, the approach does not require calculating nonlinear steady-state equations for each possible grid topology.

Solar Tracker with a Self-Deploying System

This article provides a brief overview of the state of solar energy in the world. Disadvantages of fossil energy sources are discussed. Low efficiency is considered the main disadvantage of renewable energy sources. A possible way to improve efficiency of solar modules through the use of solar tracking systems (STS) is analyzed. STS is a special device with two drives for horizontal and vertical guidance to ensure that solar modules face the highest light flux source and thereby increase generation of electricity using a special algorithm. The theoretical increase in production for systems under ideal conditions is calculated; working values thereof are given. The disadvantages of the considered type of renewable energy generators are listed. The calculation of wind loads on the STS was carried out according to the presented method. Examples of destruction of solar power plants by natural disasters are given. A new type of solar trackers with a self-deploying system is proposed; these can protect the installation from unfavorable weather conditions. We analyzed accuracy of the positioning algorithm developed for this device. The conclusion contains possible ways of using the installation, its disadvantages, as well as plans for future research.

Recycling Heat Losses of an Oil-Immersed Transformer: Feasibility Study

The paper investigates the feasibility of adding a liquid heater to an oil-immersed transformer. It proves that design the high efficiency of power transformers, losses due to idling and short circuits are substantial and are scattered in the environment as heat. The paper proposes a novel design that implements a liquid (coolant) heater to enable the unit not only to convert electricity, but also to generate heat. In order to analyze the feasibility of such heat recycling, the authors have developed an equivalent thermal circuit and a mathematical model thereof. Said heater can operate in two modes. In the passive mode, the coolant it contains only absorbs the heat emitted (lost) by the power transformer. In the active mode, it also receives the heat emitted due to the passage of electric current through the pipes of the heater. The paper further introduces the definition of heater efficiency. Studies have shown that up to 50 % of transformer heat losses can be recycled by heating the coolant in the heater. The paper presents the relationship between utilized heat and transformer losses, as well as heater efficiency as a function of coolant flow rate. The heater efficiency exceeds 90 % in the active mode.

Flexible Tranmission Elements for Grid Optimization

The article dwells upon optimizing, reduction of losses in, and improving the stability of grids by implementing devices that affect the parameters and power flows in a grid. State-of-the-art technology for better control is crucial for the development of electric power systems. FACTS technologies or flexible alternating current transmission systems, essentially transform the grid from a passive electricity transport into a device that actively controls the grid parameters. The article analyzes the development of a 500/220/110 kV grid that uses parameter-affective devices: SVC, BSK, LCD. Steady-state parameters, active power losses, and electric power losses were calculated for a year before and after the devices were deployed. Each device was therefore analyzed for effectiveness. The parameters of the SVC-equipped 500/220/110 kV grid were calculated for emergency operation with the 500 kV line being offline. Thus, the paper also analyzes the emergency performance of the SVC.

PVsyst Software for Better Energy Efficiency of a Grid-Connected Photovoltaic Power Station

The paper presents a classification of solar tracking systems used in photovoltaic power stations (PVS) and their operating principles. A simulation model of a grid-connected 5-kW PVS has been developed in PVsyst, to which end the researchers selected PVS equipment and optimized the PV cell tilt angles. The paper further analyzes a grid-connected PVS in Orenburg Oblast in PVsyst under the following configurations: static PV cells, not tilted vs seasonally varied tilts; single-axis solar trackers with vertical and horizontal axes of rotation vs a dual-axis solar tracker. The analysis is based on solar insolation data for 2019 obtained from the research team’s HP-2000 weather station. Dual-axis solar tracker and single-axis vertical trackers are shown to have the best year-round generation, providing an increase of 13.2% and 11.5%, respectively, against the static PV cells (no change in tilt).

Investigation of Ways to Reduce the Inrush Current when Starting High-Voltage Motors

The operation of high-power industrial electrical installations, particularly in metallurgy and the oil and gas industry, is associated with complex technological processes that require increased attention to the equipment used, as such equipment is used in complex and dangerous production conditions and in continuous operation facilities. High-voltage air and gas compressors are objects with increased electrical energy consumption and have significant starting currents. These circumstances affect both the shape of the supply voltage and the state of the energy system in general. Currently, the development of methods for limiting inrush currents is an urgent task for objects used in industrial enterprises. Introducing a compressor into the technological process is sometimes requires prior coordination of its start with the equipment in operation, especially that with a high power consumption. The paper studies the existing control system as well as ways to upgrade the system to improve its energy performance.

MULTIVARIABLE CONTROL OF SOLAR BATTERY POWER: ELECTROTECHNICAL COMPLEX AS OBJECT WITH HESSIAN-DRIVEN GRADIENT FLOWS

The paper presents certain development results for the novel extremum seeking controller based on Nesterov’s gradient flows for solar tracking systems. It achieves convergence to an arbitrarily small neighborhood of the set of the cost function optimizers. Our results evident ate that for arbitrarily large compact sets of initial conditions, and arbitrarily small neighborhoods of the optimizer, the controller can be tuned to guarantee convergence taking into account the influence of the Hessian, as well as with tuning parameters that have a fairly clear physical meaning. The influence of the Hessian as a vector field, which is a reflection of the distortion of transient processes in the system, and taking it into account is an urgent task, since it allows for a more flexible impact on the speed of transient processes, and by endowing the system with some damping and smoothing, also for its improved quality.

COMPARATIVE ANALYSIS OF PRESSURE PULSATIONS CAUSED BY SPIRAL-VORTEX STRUCTURES IN THE FLOW PART OF THE HYDRAULIC TURBINE MODEL

The paper studies the pressure pulsations in the hydraulic turbines flow section arise as a result of vortex structures in non-optimal hydraulic turbine operation regimes. The authors directly compare the approaches to the extraction of synchronous and asynchronous components in pressure pulsation signals, as well as using the decomposition into azimuthal modes. Pressure pulsations were measured using four acoustic sensors while varying the operating regimes of the hydraulic turbine model. The pressure pulsations were compared for the shallow draft tube and the deep draft tube of the hydraulic turbine. It is shown that the level of pressure pul-sations is the same for two types of draft tubes. There is no methodological difference in the application of the two approaches to the extraction of pressure pulsations in the flow. The results shall be applicable in the de-velopment of new methods for suppressing spiral-vortex structures in non-optimal regimes of operation of hydraulic turbines in order to increase their overall efficiency.

Development of Remote Monitoring for Solar Heating Systems

This article presents a novel method for developing a stationary remote monitoring system for solar heating / hot water supply systems designed for industrial or residential use. The system is based on a T-Call ESP 32 SIM800L board with a BME280 sensor that can operate in deep sleep mode. The logic board contains a SIM card to connect to the Internet on a data plan. It communicates sensor readings to the server and goes back to sleep mode. The presented case has 60 minutes of sleep, which can be reconfigured easily in the code. The proposed system of remote monitoring and control enables more efficient utilization of solar collector systems for industrial and residential heating and hot water supply.