Steady-state Operation Modes Research Articles

Эквивалентирование участков электроэнергетических систем на основе режимных параметров в узлах эквивалентирования

When modeling steady-state and transient operating modes in electric power systems, it is necessary to determine a section of the electrical network to simplify the processes occurring in the area not covered by equivalenting. In this case, it is necessary to identify equivalents and relationships with respect to the speci-fied section. The purpose of the research is to determine the parameters of the equivalent sections of power systems and their relationships with respect to the given nodes. Methods of mathematical modeling of the elements of power systems, methods of the theory of electric circuits, and methods of matrix analysis are used. To verify the results, electrical circuits of existing power systems and the software package “Auto-mated Workplace of Relay Protection and Automation Service” have been applied. The implementation of the algorithm is carried out using programming in the Python environment. An algorithm to determine the parameters of equivalent circuits of positive, negative and zero sequences is developed and tested when solving the problem of equivalenting a network section with respect to given nodes. Comparison of the levels of currents in case of short circuits according to the developed algorithm and the software package “Automated Workplace of Relay Protection and Automation Service” in the equivalent nodes shows the high accuracy of the equivalent results in accordance with the developed algorithm. The algorithm considers transformer connections when equivalenting with respect to the nodes located at different voltage classes, as well as phase shifts caused by the star-delta conversion.

Deflagration-to-Detonation Transition in a Semi-Confined Slit Combustor Filled with Nitrogen Diluted Ethylene-Oxygen Mixture

The conditions for the mild initiation of the detonation of homogeneous stoichiometric ethylene-oxygen mixtures diluted with nitrogen up to ~40%vol. in a planar semi-confined slit-type combustor with a slit 5.0 ± 0.4 mm wide, simulating the annular combustor of a Rotating Detonation Engine (RDE), are determined experimentally using self-luminous high-speed video recording and pressure measurements. To ensure the mild detonation initiation, the fuel mixture in the RDE combustor must be ignited upon reaching a certain limiting (minimal) fill with the mixture and the arising flame must be transformed to a detonation via deflagration-to-detonation transition (DDT). Thus, for mild detonation initiation in a C2H4 + 3O2 mixture filling the slit, the height of the mixture layer must exceed the slit width by approximately 10 times (~50 mm), and for the C2H4 + 3(O2 + 2/5 N2) mixture, by approximately 60 times. The limiting height of the mixture layer required for DDT exhibits a sharp increase at a nitrogen-to-oxygen mole ratio above 0.25. Compared to the height of the detonation waves continuously rotating in the RDE combustor in the steady-state operation mode, for a mild start of the RDE, the fill of the combustor with the explosive mixture to a height of at least four times more is required.

Optimization of the operating mode of a squirrel-cage induction motor

THE PURPOSE. The presented work aims to optimize the operating mode of an asynchronous motor (AM) with a short-circuited rotor. To implement energy-efficient modes of operation of AM, operating in the resources of a rational electric drive, it is necessary to determine the numerical values of the parameters of the AM equivalent circuit, the currents flowing through the circuit element. There is no significance to this important definition of squirrel-cage currents, in accordance with the identification of the allocation of squirrel-cage rotor currents, which requires a solution along with the determination of the parameters of the IM equivalent circuit.METHODS. To analyze the work of AM in technical and educational formulations, equivalent circuits are presented, which turn into circuits with serial and analytical connections of active and inductive connections. For the established and transient operating modes of AM, it is important to determine the stator and rotor currents, their active and reactive components. In this regard, it is proposed to present the IM equivalent circuit in the form of conductivities connected in parallel, which will allow determining the components of IM currents without complex mathematical models. The replacement circuit of AM consisting of a series and parallel connection of active and inductive resistances has been converted into a circuit consisting of conductances. When converting the AM equivalent circuit, no additional dependencies and coefficients were introduced, and all assumptions that are accepted for IM equivalent circuits refer to the circuit under consideration. RESULTS. It was decided to use the equivalent circuit of one phase of AM, expressed in terms of the conductivities of the stator and rotor. According to the found dependences of conductivities, for the proposed equivalent circuit, the corresponding currents and powers of the AM phase are determined. Formulate the basic principle of optimal frequency control of AM, according to the criterion of energy saving. As an indicator of the efficiency of AM operation in steady-state operating modes, the minimum value of the total losses of the engine, the value of which is determined by the ratio of the product of the active conductivity of the rotor circuit q2s and the active conductivity of the phase q to the square of total conductivity y.CONCLUSION. Based on the results of the analysis of the characteristics of an asynchronous motor, the following conclusion was drawn: the motor will operate with minimal losses if the amplitude of the supply voltage is changed so that the slip of the asynchronous motor is equal to the critical value sξ for a given frequency. For the investigated engine AIR100S4, the critical value is sξ=0.0613 at a network frequency of 50 Hz. The method proposed in the work allows to reduce the loss of active power by 3-5% in the motor windings.

ПРИСТРІЙ ФОРМУВАННЯ ПЕРЕВІРЯЮЧОГО ТЕСТУ ЦИФРОВОГО ТЕЗ РЛС 19Ж6

The general need to develop additional diagnostic equipment is that a fairly large number of complex technical objects are currently in use, which are morally but not physically obsolete, and therefore it is not possible to abandon their use today. Radar 19Ж6 belongs to such objects. The level of diagnostic support for this radar does not meet the requirements for modern models of radio electronic weapons (REW). The 19Ж6 was replaced by another radar with significantly improved diagnostic support. An automated diagnostic complex of the Diana series is used to diagnose and repair modern radar systems of domestic production. This complex is designed to diagnose and restore complex digital and digital-to-analog standard replacement elements. It is possible to adapt a modern diagnostic complex to diagnose outdated equipment, but within the limited funding, it is economically impractical. Accordingly, there is a task to develop modern means of diagnosing typical replacement elements of the 19Ж6 radar, which can be used to equip stations. Within the framework of the overall task, a number of partial tasks can be identified. One of these tasks is the development of a general methodology and a structural diagram of the device for determining the verification test for digital standard replacement elements (SRE) from the 19Ж6 radar. Thus, the article is devoted to the development of a block diagram of the device for forming a diagnostic test as a component of the device for monitoring the technical condition of digital SRE. The structure of the device is completely determined by the methodology of the test structure. The result of the diagnostic test is a decision on the operability or inoperability of the SRE. The need for such diagnostics stems from the fact that the built-in technical diagnostic system does not detect a single inoperable TES, but detects a group of suspected inoperable SRE. To separate the inoperable digital device, it is necessary to use additional equipment. The paper proposes to use an energy-static diagnostic method, the essence of which is that the value of the voltage on an additional resistance, which is measured in a steady-state operation mode, is used as a diagnostic parameter. The method of designing the verification test is the method of experimental evaluation of the length of the test sequence, and the sequence itself is a pseudo-random sequence of input influences.

THE EXPERIMENTAL STUDIES OF A BIOTHERMAL INSTALLATION FOR CALF HOUSE FLOOR’S HEATING RESULTS

Farm animal manure is one of renewable energy resources types that the selfheating at humus process’s property has had. It allocates bioheat suitable for use (heating water for animals watering and cows' udders washing, livestock premises floor heating, etc.). The authors have developed and tested a biothermal installation to increase the efficiency at bioheat released during manure selfheating’s using. The biothermal installation with temperature sensors at the inlet is equipped, as well as at the installation outlet and in the manure mass, at characteristic’s points directly. The active selfheating period is 40-42 days from the start date. Studies have established the average selfheating temperature of the manure mass (3000-3100 kg - a mixture of horse and sheep manure in a ratio of 1:1, humidity 70-75%) for this period, which is 57.9 ± 5.67 °C at a variation’s coefficient of 9,8% with an air temperature fluctuation of 17°C...-2°C. Fluctuation of air temperature does not significantly affect the process of manure mass selfheating. At subzero ambient temperature, the manure selfheating with a slight slowdown continuing . In the steadystate operation mode, the average water temperature at the biothermal installation’s entrance and at the exit from it, is respectively, 44.9 °C and 54.9 °C. This biothermal installation’s average heating capacity and thermal power are 50-53 kJ/kg and 320-325 watts.

Математическое моделирование трансформаторного устройства с короткозамкнутой обмоткой для преобразования однофазного тока в шестифазное напряжение

Представлена математическая модель трансформаторного устройства с короткозамкнутой обмоткой (ТУ с КО), осуществляющее преобразование однофазного входного тока в шестифазное напряжение, которое может быть использовано в релейной защите электрических сетей. На основе математической модели ТУ с КО получена система дифференциальных уравнений в пространстве состояний, необходимых для моделирования и анализа различных установившихся и переходных режимов работы электрических сетей. Использованы подходы теории пространства состояний для получения системы дифференциальных уравнений применительно к структуре ТУ с КО. Получена математическая модель ТУ с КО в форме уравнений в пространстве состояний, позволяющая из однофазного входного тока сформировать систему шестифазных выходных напряжений. На основе предлагаемой модели ТУ с КО создана возможность его применения во входных цепях измерительных органов релейной защиты электрических сетей и проведения исследований.

THERMAL MANAGEMENT OF A SET OF THERMOELECTRIC COOLERS CONNECTED IN PARALLEL IN AN UNEVEN TEMPERATURE FIELD

A method of increasing the efficiency of thermoelectric system for providing thermal modes of distributed heat-loaded elements of an on-board information system is considered. It is shown that thermoelectric coolers are most susceptible to thermal effects. In accordance with the reliability model, they are connected in series with heat loaded elements and to a great extent determine their operability. The inclusion of thermoelectric coolers in the feedback loop of a thermal management system places increased demands on the dynamic performance of the coolers. However, dynamics and reliability performance are at odds with each other, requiring compromise approaches to cooler design and control. Studies have been carried out for an uneven temperature field, a typical dissipation power range, and a fixed geometry of thermocouple branches. Analytical relations for determining the relative operating current depending on the relative temperature difference at a given supply voltage, geometry of thermocouple branches and heat load value have been obtained. The range of actual values of the relative operating current in the area of relative temperature differences is determined. An analysis of relation between relative operating current and refrigerating factor, amount of consumed energy, heat dissipation capacity of a radiator, time of reaching steady-state mode and probability of no-failure operation has been carried out. The dependence of the relative failure rate, energy input, heat dissipation capacity of the heat sink and the number of thermocouples on the supply voltage has been investigated. This made it possible to determine the controlling features and to reveal the efficiency of controlling actions when the coolers are connected in parallel in an uneven temperature field. The possibility of selecting the optimum supply voltage taking into account the limiting factors for mass-size, energy, dynamic and reliability characteristics of a set of thermoelectric coolers with parallel electric connection is shown. This makes it possible to create thermoelectric systems for providing thermal modes with increased reliability while minimizing mass and dimensional characteristics.

A novel experimental procedure for lock-in thermography on solar cells

<abstract> <p>The occurrence of defects in solar cells is intrinsically related to a reduction in the efficiency and reliability of these devices. Therefore, monitoring techniques, such as lock-in thermography, electroluminescence and the I-V characteristic curve are adopted in order to evaluate the integrity of the solar cells. In the present work, a novel experimental procedure for the lock-in thermography of solar cells is proposed, aiming to improve the detection capability of the assay. Conventional techniques use pulse width modulation to operate the cell at a fixed point on the I-V curve. Instead, we propose a methodology based on a sinusoidal electric current excitation in order to extend the range of operational points that are close to the maximum power point as the cell operates in the field. Some traditional image processing techniques (principal component analysis, the fast Fourier transform and the four-step phase-shifting method) have been used to analyze the thermal images captured by an infrared camera during steady-state operation mode of the solar cells using both sinusoidal electric current signal and standard pulse width modulation procedures. Comparison between the results of both procedures found that this novel approach provides smoother and clearer delimitation of the defects. Furthermore, the contrast of the phase images was found to exhibit significant changes between the defective and non-defective regions for different modulation frequencies and types of defects. From the achieved results, it was possible to obtain a satisfactory characterization of the existing defects.</p> </abstract>

Уточненное моделирование и экспериментальное исследование энергоэффективной системы испытаний асинхронных машин

When testing asynchronous machines, it is important to use energy-efficient methods, for example, the method of mutual loading of two machines with articulated shafts. One machine operates in the mode of the motor – frequency converter, the second machine operates in the mode of the generator – industrial frequency network. Both machines are simultaneously tested under load and energy costs for testing are reduced due to its recuperation. The method requires a correct loading algorithm. The modeling of the method based on chain models does not consider the implementation feature. Thus, it is advisable to refine the simulation of the asynchronous machine testing system by the mutual load method. The method is based on strict models considering the coupling of machine torque on a common shaft, the operation of machines in the mode of frequency converter, non-sinusoidal supply voltage, saturation of steel, displacement of current in conductors, for example, based on the associated analysis of electromagnetic fields in both machines. The authors have applied the packages of electromechanical units with electrical and mechanical Ansys Simplorer ports and finite element analysis of electromagnetic fields Ansys Maxwell for refined simulation of the asynchronous machine testing system by the method of mutual loading. Experimental studies of the system have been carried out on laboratory equipment using certified devices. A refined simulation of an energy-efficient testing system of asynchronous machines by the method of mutual loading has been carried out. It is based on calculations of the electromagnetic field and allows us to read the transient and steady-state modes of operation of a two-machine unit with a common shaft. An automated stand has been created that allows testing asynchronous machines by the method of mutual loading. The developed refined simulation of electromechanical processes in asynchronous machines during tests by the method of mutual loading with associated calculations of electromagnetic fields in both machines provides calculated results with an error of no more than 5–7 % in comparison with 40 % error of calculations in the transient modes of operation using chain models.

Data-driven modeling of multimode chemical process: Validation with a real-world distillation column

Real-world industrial processes frequently operate in different modes such as start-up, transient, and steady-state operation. Since different operating modes are governed by different process dynamics, deriving a single data-driven model representing the entire operation of such multimode processes is not a viable option. A reasonable solution to this problem is to develop a separate model for each operating mode, which requires the extraction of data for each operating mode from raw data. Based on this viewpoint, this work develops a data-driven modeling approach using clustering and featuring selection techniques to improve the quality of raw data and develop a predictive model for a multimode industrial process. In particular, the developed method focuses on training a steady-state predictive model as monitoring steady-state conditions is crucial for achieving the desired product quality. Firstly, K-means clustering is performed to extract data describing the steady-state operation mode from the available raw data. Next, feature selection is applied to the clustered data using Pearson’s correlation coefficient to identify input features relevant to target features. Finally, an LSTM model is trained using the clustered data and identified features to predict the steady-state operation. The validity and effectiveness of the developed method are demonstrated using a real-world 2,3-Butanediol distillation process dataset.

Continuous simultaneous saccharification and co-fermentation (SSCF) for cellulosic L-lactic acid production

Continuous fermentation is preferred in industrial bioprocesses by its steady-state operation mode and the significant reduction of switch operation of vessels emptying, cleaning, and sterilizing. General biorefinery fermentation of lignocellulose is conducted in the mode of simultaneous saccharification and co-fermentation (SSCF) thus the continuous operation does not stand well because of the mismatch between the optimal temperatures of cellulase enzymes and microbial cells. This study challenged the continuous SSCF operation for production of high chiral purity L-lactic acid based on the dry biorefinery processing platform. An engineered thermophilic L-lactic acid bacterium Pediococcus acidilactici with complete non-glucose assimilation capacity and antibacterial activity with a nearly perfect match of temperature (42–50 °C) and pH (5.5) with that of cellulase enzyme used (50 °C, pH 4.8). This microbial cell factory allows the enzymatic hydrolysis and fermentation to be conducted simultaneously in one-pot bioreactor and provides the basis for establishing a valid continuous SSCF operation. The continuous SSCF of the biodetoxified wheat straw was established in cascade bioreactors and the performances of L-lactic acid titer, yield, and productivity reached 107.5 ± 1.1 g/L, 0.29 ± 0.01 g/g DM, and 2.69 ± 0.03 g/L/h, respectively. The chiral purity of the cellulosic L-lactic acid reached 99.5 %. The low residual sugar concentration and high-optical purity L-lactic acid product in broth facilitate the subsequent purification of L-lactic acid as the monomer for cyclic lactide or direct PLA synthesis. This multi-stage continuous SSCF technology overcomes the inherent barriers of the batch SSCF operation and provides a prototype for future industrial cellulosic lactic production.

Early Detection of Faults in Induction Motors—A Review

There is an increasing interest in improving energy efficiency and reducing operational costs of induction motors in the industry. These costs can be significantly reduced, and the efficiency of the motor can be improved if the condition of the machine is monitored regularly and if monitoring techniques are able to detect failures at an incipient stage. An early fault detection makes the elimination of costly standstills, unscheduled downtime, unplanned breakdowns, and industrial injuries possible. Furthermore, maintaining a proper motor operation by reducing incipient failures can reduce motor losses and extend its operating life. There are many review papers in which analyses of fault detection techniques in induction motors can be found. However, all these reviewed techniques can detect failures only at developed or advanced stages. To our knowledge, no review exists that assesses works able to detect failures at incipient stages. This paper presents a review of techniques and methodologies that can detect faults at early stages. The review presents an analysis of the existing techniques focusing on the following principal motor components: stator, rotor, and rolling bearings. For steady-state and transient operating modes of the motor, the methodologies are discussed and recommendations for future research in this area are also presented.

Operation maps in calcium looping thermochemical energy storage for concentrating solar power plants

Calcium Looping (CaL) process used as thermochemical energy storage system in concentrating solar plants has been extensively investigated in the last decade and the first large-scale pilot plants are now under construction. Existing research focuses on improving global efficiencies under steady-state and single modes of operation: energy storage or energy retrieval. However, TCES systems will operate under different operation points to adapt the load of its reactors to the solar availability and the energy demand from the power cycle. A thorough analysis of the operation modes provides an extremely large number of potential situations to operate the system. In this study, operation maps which maximize thermal energy availability and energy storage efficiency are defined. Furthermore, a novel approach for the management of partially carbonated solids is examined to reduce the circulation of inert material in the system based on preliminary experimental results which allows for a partial separation of carbonated solids. Two threshold scenarios are analysed: (i) no solids separation as considered in most CaL TCES studies and (ii) ideal total solids separation. The aims of this work are to set methodological criteria to define the optimal operation map and to assess the effect of partially carbonated solids separation on the energy penalties and equipment size. The inclusion of a solid separation stage leads to a maximum increase of energy storage efficiency of 26 % and a size reduction between 53 and 74 % of those heat exchangers affected by solids streams.

Research on steady-state operation modes of electrical spring

With the help of instantaneous power theory and Matlab/Simulink simulation tools, the principle of electrical spring (ES) steady-state operation modes division was analyzed, the instantaneous power changes of ES in different steady-state operation modes were studied, then the equivalence circuit of ES under different operating conditions were deduced, the problem that how the steady-state operation mode of ES switches to stabilizes the critical load voltage with the different working conditions was analyzed. Simulation experiments verify the correctness of the research results.

Power Transformer Condition Monitoring Based on Evaluating Oil Properties

The authors review the techniques applied to diagnose oil aging. Further, the authors put forward a new diagnostic method. It stipulates for an additional high-frequency measuring loop formed in an operating transformer. This dielcometric measuring capacitor cell includes a stray capacitance generated by the transformer winding and core. The monitoring of the dependence between the physico–technological oil parameters and the measuring cell capacity is fundamental for the procedures for determining the composition and properties of the transformer oil filling this cell. High-frequency low-voltage is the output signal. To prevent the cross-impact of low-frequency high-voltage and high-frequency low-voltage circuits, the pilot high-frequency low-voltage is excited by a special coupling capacitor; the output to the power feeder is conducted through an appropriate low-frequency choke, where the measuring capacitor cell does not disturb the normal transformer operation. The key physical processes used for the monitoring are analyzed and described in detail. The authors develop an algorithm to compute the current resistances of both the transformer oil and its impurities. The transformer state is estimated by comparing the parameters specified with preset permissible limits. A structure flowchart based on two synchronous quadrature detectors is proposed for a high-frequency measuring loop. The monitoring system considered allows for determining the following insulating oil properties by using the algorithm for processing the recorded data: moisture content; dielectric losses due to the accumulation of aging products in the oil and its pollution; and the content of dissolved gases in the oil. The monitoring system operability and efficiency are confirmed by appropriate experimental studies. The experiments are conducted using a TM-25-6/0.4 oil-filled transformer with a capacity of 25 kVA in a steady-state operating mode at a load current of 25 A. It is found that the proposed control system allows for identifying a critical defect of increased moisture content in the oil with no more than 10% error, and a sensitivity threshold in the order of tenths of ppm.

Investigation of Existence of Steady States of a Solar Power Plant Operating in the Distribution Network of an Electric Power System

The paper presents the results of studies of the steady-state operating modes of solar photovoltaic stations. Using the data obtained, it is possible to significantly increase the efficiency of using solar power generating plants and significantly increase the service life of additional equipment. The relevance of this study is due to the increasing demand for low-power electric power systems, as well as for renewable energy technologies. For the research, materials were taken from relevant international departments and agencies, the Ministry of Energy of the Russian Federation. In addition, the sources of data are publications and studies of Russian and foreign scientists on the issues under study. The Federal Law No. 35-FZ “On Electricity”, adopted in December 2019 by the State Duma of the Russian Federation, introduces such a concept as “Micro-generation facility”, thereby simplifying the possibility of installing, connecting to the general network of an electrical system, for example, a small solar power plant (SPP) consumer. Small-scale electric power industry at this stage of its life is an energy-efficient tool in the restructuring of the energy sector of the Russian Federation, contributing to the abandonment of the traditional centralized system based on the use of large sources of electric power production, and the transition to alternative methods of generating electricity based on the use of energy sources, updated for specific natural conditions and requests of potential consumers. Reducing pollutants and emissions that are harmful to human health can reduce the level of the existing burden on the country's economy and give an impetus to the development of its potential due to the freed up resources. reduce the burden on the economy, thereby freeing up resources for its growth. Of course, the transition from traditional economic models to the model of “green growth” can be realized only if significant efforts are made to expand international cooperation in this area. At the same time, there is a need for consistent implementation of events at various levels on the part of all states, as well as maintaining the chosen political course for many years.

Energy efficiency assessment of distribution networks

This paper discusses the effectiveness and evaluation of the modes of distributed networks with a voltage of 33/11 kV. Using the example of a fragment of the distribution networks, the features of their construction and the main parameters are analyzed. The calculation of steady-state and post-emergency operation modes in the RastrWin software package was performed, which showed that voltage and power losses in the branches of the distribution network exceed the limit values. The classification of technical measures contributing to partial unloading of the network and increasing the capacity of power lines is given. The power values of additional sources in the form of distributed generation are taken in such a way as to compensate for the power losses in the corresponding connection nodes. An assessment of the efficiency distribution networks, taking into account the use of distributed generation, confirmed a significant reduction in voltage and capacity losses in the network branches and thereby an increase in electricity quality indicators.

Diagnostic Model of Aircraft Turbine Engine Governor Pump

Abstract This paper presents a mathematical model for a hydromechanical fuel governor pump, to be used in parametric diagnostics. The design and operation of the governor are described. The main requirements of the model are formulated, its structure is determined, corresponding to the specifics of the diagnostic task, and assumptions to make the model simpler are presented (single-dimensional flow and absence of heat exchange). The presented model consists of idealized elements with lumped parameters (such as pressure and mass consumption of the working fluid), accounting for the compressibility of the substance and the design arrangement of the governor (presence of mechanical rests, metering orifices of complex shapes, relay switchers, etc.). Equations of elements with lumped parameters, linked by hydraulic channels in one node, are presented. The model – a system of first-order differential-algebraic equations – is solved and the parameters of the governor pump are determined for different steady-state and transient operation modes. We compare our results to the requirements for the corresponding parameters outlined in the Engineering Specifications. The model is matched to the specifications by correcting setting parameters (tightening of elastic springs, areas of throttles, etc.), and a method of initial model linearization is developed. Based on the results, we conclude that our model can be used as a diagnostic algorithm for a governor pump, at the testing and development stages, during manufacturing, repair and maintenance.

МЕТОДИКА РОЗРАХУНКУ ЕНЕРГЕТИЧНИХ ХАРАКТЕРИСТИК ПЕРЕТВОРЮВАЧА ЕНЕРГІЇ МОРСЬКИХ ХВИЛЬ ЗА ПЕРІОД КОЛИВАННЯ ХВИЛІ

The use of efficient and environmentally friendly methods for electricity generation is one of the main concerns in the field of energy. The advantages and disadvantages of wave energy power plants are well-known and continuously researched. There are many approaches and methods for converting wave energy into electrical energy, each with its own advantages and disadvantages, designed for different converter constructions and utilizing various approaches. This article presents a simple converter scheme that converts the energy of cylindrical buoy oscillations into electrical energy. The aim of this work is to develop a methodology for calculating the energy characteristics of this wave energy converter, consisting of a cylindrical buoy, a pulley, and a magneto-electric generator, using the average energy indicators of the generator. The proposed converter scheme utilizes a single cylindrical buoy and a three-phase generator with resistors as the electricity consumer. The sea surface oscillation is represented by a sine wave with higher harmonics. The balance equation of forces acting on the buoy is formulated, taking into account the ratio of the moment on the rotor to its speed. An iterative calculation is used to determine the optimal rotor speed to maximize electricity consumption power. To establish the resistor's resistance, the steady-state operation modes of the generator and the average optimal rotor speed over the period of the sea wave are used. The generator is then modeled with an optimal resistor resistance and a specified variable rotor speed over the wave period. The energy absorbed by a single buoy, with a wave amplitude of 1 meter and a period of 10 seconds, is studied. Ref. 16, fig. 10.

Model-Independent Observer-Based Current Sensorless Speed Servo Systems with Adaptive Feedback Gain

This study proposes a solution to the speed control problem of servo machines in the form of multi-loop current sensorless control with a reduction in the system model dependence level and the number of feedback loops, which provides the two contributions: first, a model-independent observer estimates speed and acceleration using only the position measurement, thereby ensuring the first-order estimation error dynamics; second, the active damping acceleration stabilizes the inner loop with the adaptive feedback gain increasing and decreasing automatically according to the transient and steady-state operation modes. The experimental study highlighted the effectiveness of the acceleration loop adaptation technique, which used an actual servo system comprising the QUBE-servo2 and myRIO-1900.