Single-phase Systems Research Articles

Cu2−xS and Cu2−xSe Alloys: Investigating the Influence of Ag, Zn, and Ni Doping on Structure and Transport Behavior

Cu2−xS and Cu2−xSe (0 ≤ x ≤ 0.2) alloys stand out as highly promising materials for thermoelectric applications, owing to the phonon–liquid electron–crystal (PLEC) convention. In this study, we undertake a comprehensive investigation to reassess the synthesis conditions, with a focus on achieving pure-phased systems through a direct reaction between elements at elevated temperatures. Simultaneously, we present experimental evidence showcasing the feasibility of doping these systems with Ag, Ni, and Zn. The study demonstrates that obtaining single-phased systems requires multi-step processes, and the dissolution of chosen impurities appears doubtful, as evidenced by numerous foreign phase segregations. Additionally, it is revealed that the partial dissolution of individual impurities deteriorates the operational parameters of these chalcogenides. For the optimal Cu1.97S composition, it reduces the thermoelectric figure-of-merit ZT from 1.5 to approximately 1.0, 0.65, and 0.85 for Ag-, Ni-, and Zn-doped systems, respectively, while marginally improving their stability. For metal-like Cu1.8Se, the ZT parameter remains at a low level, ranging between 0.09 and 0.15, showing slight destabilization during subsequent operating cycles. The article concludes with an in-depth analysis of the basic thermoelectric performance exhibited by these doped systems, contributing valuable insights into the potential enhancements and applications of Cu2−xS and Cu2−xSe alloys in the field of thermoelectric materials.

Budeanu’s Distortion Power Components Based on CPC Theory in Three-Phase Four-Wire Systems Supplied by Symmetrical Nonsinusoidal Voltage Waveforms

Budeanu’s power theory, in its fundamental version, describes single-phase sinusoidal and nonsinusoidal systems. Over time, this elementary description has been extended to three-phase three-wire and four-wire systems, regardless of power conditions. Initially, three-phase systems were considered as three independent single-phase systems. A distinct approach was introduced by Czarnecki in his power theory (Currents’ Physical Components—CPC). The energy description and reference of the equivalent parameters of the load are comprehensive in the context of three-phase systems; Czarnecki treats such systems as a whole. This paper introduces a mathematical model to expand the basic Budeanu theory for three-phase four-wire (3-p 4-w) systems powered by symmetrical and nonsinusoidal voltage sources. The proposed approach is based on mutual elements between the fundamental Budeanu theory and the CPC theory, treating the 3-p 4-w system as a whole. In the extended Budeanu theory model, equations for the Budeanu reactive current and the Budeanu complemented reactive current are derived. The article also demonstrates their orthogonality concerning the remaining components, indicating that each of the seven components can exist independently of the others. Furthermore, in the extended Budeanu theory, it is possible to identify which equivalent parameters of the load are responsible for the individual currents (powers) and which components are associated with the total distortion power proposed by Budeanu in 1927. All of the calculations were performed in Matlab/Simulink 2023b software.

HYDRODYNAMIC BASES FOR CALCULATING THE MOTION OF TWO-PHASE SYSTEMS IN COMPLEX PIPELINES

Considering the conditions for the development of an oil field for different layers, the pipeline networks are different. Based on hydromechanics of homogenous fluid and gas, a new model of two-phase systems movement of fluid-gas type in horizontal tubes is suggested and the major calculation formula for complicated pipelines is developed. In constructing a complex system of pipelines transporting both single-phase and two-phase systems, firstly, it is necessary to consider the location of wells in the field, their initial and final flow rates, as well as the physicochemical properties. This method enables us to define the main parameters of complicated pipelines, considering the physical properties of two-phase systems. The equation of two-phase systems movement in simple and complicated pipelines, allowing recommending using this approach in field experience, is obtained as well. Keywords: shear stress, complicated pipeline, multiple connections, diameter, volumetric fluid, and gas discharge.

Synthesis and research of polyurethane urea with 2-(2-aminoethoxy)ethan-1-amine and 3-{2-[2-(3-aminopropoxy)ethoxy]ethoxy}propane-1-amine as macrochain extenders, and compositions with ifosphamide based on them

Polyurethane urea (PUU) was synthesized using macrochain extenders of 2-(2-aminoethoxy)ethan-1-amine (DA1) and 3-{2-[2-(3-aminopropoxy)ethoxy]ethoxy}propan-1-amine (DA3) at a molar ratio of 4,4'-diaminodiphenylmethane (DADP) to DA1 and DA3 as 30:70; 50:50; and 70:30. The tensile strength () of PUU is in the range of 0.74–2.21 MPa, and the relative elongation at break () is 27.4–1003%. According to the DSC method, the studied PUUs are single-phase systems. The glass transition temperature (Tg) of the PUU DA1 series is from 21.920C to –39.480C, and the glass transition temperature for the PUU DA3 is from –20.040C to –33.960C. Based on the synthesized PUUs, composite materials were prepared containing 1 wt.% of ifosfamide (IFO) (=0.74–2.21 MPa, and =31.8–276.3%). According to the results of thermophysical studies, the compositions with IFO are single-phase systems with Tg of –24.80C to –36.220C. Thus, the introduction of IFO into the composition leads to an increase in the packing density of the macrochain, a decrease in the size of the free volume and, consequently, a decrease in the mobility of the blocks in space and a decrease in Сp. Compositions with IFO are resistant to temperatures of ~2500C, which allows thermal sterilization before use. Using the HPLC-UV method, the dynamics of IFO release from samples of PUU compositions synthesized at a molar ratio of DADP:DA1 as 0.5:0.5 and DADP:DA3 as 0.7:0.3 was investigated. It was established that IFO is released within 60 days from compositions based on PUU DA3 in the amount of 29.6%, and from compositions based on PUU DA1 in the amount of 42% with respect to the total amount of IFO introduced. The resulting composites are promising materials for medicine as means of local prolonged therapeutic action.

Control of PV power plants with quasi-Z-source cascaded H-bridge multilevel inverters under failure

At the present time, quasi-Z-source cascaded H-bridge multilevel inverters (qZS-CHBMLI) have gained attention in photovoltaic (PV) applications, due to their advantages over traditional multilevel inverters. They allow single-stage power conversion of a PV power plant by independently adjusting the DC voltage in each module; thus, each PV array operates at the maximum power. This advantage permits dispensing with a DC/DC boost converter and reduces the number of modules required. This paper develops a novel control strategy for a qZS-CHBMLI connected to a single-phase system that guarantees proper operation when a fault occurs in a quasi-impedance source inverter (qZSI). The control strategy is employed in a grid-connected qZS-CHBMLI with three modules, each one with a quasi-impedance network, a 4.8 kW PV array and a voltage source inverter (VSI), with H-bridge topology. The purpose of the control system is to deliver a suitable DC voltage at the input of the VSI and ensure the grid power requirements after a fault in a module. The proposed control system is evaluated through a 40 s simulation in MATLAB/Simulink® in two cases: A) analysis of the system behaviour when there is a variation in the operation limit equation; and B) evaluation of the control strategy under dissimilar operating conditions. In addition, an experimental setup based on an OPAL RT-4510 unit and a dSPACE MicroLabBox prototyping unit is employed to validate the results. The results confirmed the correct response of the applied strategy with the failure of a single module.

Pengaruh Harmonik Akibat Pengoperasian Motor Induksi Tiga Fasa Pada Sistem Tenaga Satu Fasa

The research conducted focuses on analyzing the harmonic effects resulting from the operation of a three-phase induction motor in a single-phase power system and examining changes in harmonic values due to load variations using two capacitors. This study is a continuation of previous research, which only addressed the influence of a single capacitor on a three-phase induction motor in a single-phase power system, without further exploration of the extent of harmonic impact on the motor. The induction motor operates based on the principle of magnetic induction. This investigation employs a single-phase induction motor with lower power capacity compared to a three-phase induction motor. Three-phase induction motors have a small starting torque, preventing them from starting under full load. The study involves increasing the starting torque of the three-phase induction motor and operating it in a single-phase electrical power system using capacitors to improve power factor during the starting process while analyzing its harmonic effects. The research findings indicate that as the load on the motor increases, both the motor speed and harmonic current values decrease. This is evident when there is no load, and the motor speed is 1475 rpm; adding a load does not exceed this speed. The motor speed decreases as the load increases, while the presence of harmonic current values is due to the linear load, such as incandescent light bulbs. The study is conducted by enhancing the starting torque of the three-phase induction motor, imposing a significant load. The motor demonstrates more optimal and stable performance with the new method compared to the old method. Additionally, the harmonic current values with the new method are lower than those with the old method.

Investigation of heat transfer and pressure drop characteristics in metal-foam filled channels in a plate heat exchanger: A comparative experimental study

An experiment was conducted on a single-phase system using water as the working fluid in a Gasket Plate Heat Exchanger (GPHE). The copper metal foam was employed on the corrugated profile in this experiment. The experiment was calibrated using iterative multiple linear regression analysis to find the coefficient of heat transfer on the hot water side for the given heat exchanger with a 60° corrugation angle. A comparative study was carried out between channels that were plain and modified with metal foam. The analysis focused on various factors, including the heat transfer coefficient, frictional pressure drop characteristics, pumping power, and volume goodness factor. The experiments were performed within a Reynolds number range of 200 to 1000, with the hot and cold water temperatures set at 60 °C and 30 °C, respectively. The experiments used copper metal foam with 50 pores per inch (PPI). The foam had a porosity ranging from 0.6 to 0.9, with a pore size of 1 mm. The Nusselt number for the modified GPHE was 1.97 times higher than that of the plain GPHE. Additionally, the frictional pressure drop for the modified heat exchanger was 1.89 times higher than that of the plain heat exchangers. The rate of frictional pressure drop increases at higher Reynolds numbers was higher than the heat transfer coefficient increase for both the plain and modified GPHE. The modified plate heat exchanger shows superior thermal performance compared to a plain GPHE at any given friction power conditions. Additionally, using metal foam-filled channels in contrast to plain corrugated plate channels suggests that the modified GPHE can achieve a more compact design for the same heat-duty application.

Review on the Electric Spring Connected to the Renewable Energy System to Minimize Harmonics and Voltage Profile Enhancement

The emerging smart grid technology known as Electric Spring (ES) has been employed previously to maintain voltage and power stability in renewable energy-based grids that are minimally regulated or self-contained. This study thoroughly investigated the foundational theories, modeling approaches, practical uses, and restrictions associated with Electric Springs by analyzing existing Scholarly works in this domain Electric Springs implement a direct power control approach. solution for the next-generation single-phase Systems, addressing the limitations of current ES control methods. This solution aims to improve power management in microgrids, where integrating renewable energy sources (RESs) poses challenges due to the unpredictable power output. The challenge involves managing two aspects: the variable Power consumed by ES and the power fed into the grid. The suggested straightforward and accurate signal manipulation method, namely, ANN-based Electric Spring (ES), is set to be deployed. This technique can adeptly manage these aspects in both stable conditions and during transitions in Renewable Energy Sources (RES).

Reactive Power Compensation and Distortion Power Variation Identification in Extended Budeanu Power Theory for Single-Phase Systems

This article presents methods of reactive power compensation using passive elements in the form of a capacitor (C) or choke (L) and an LC structure selected in such a way as to lead to the minimization of the reactive current (reactive power) of a single-phase system. The adaptation of the parameters of a passive compensator, reducing reactive power and/or distortion power, was possible through the extended Budeanu theory. In addition, through the extended Budeanu theory and also through the knowledge of the equivalent parameters of the linear load, the obtained results of the increase in distortion power, depending on the structure of the passive compensator, were analyzed. The values listed in the tables, as well as the waveforms of the component currents of a single-phase linear load, were obtained based on calculations and simulation models in MATLAB/Simulink software R2023a.

Układ regulacji jednofazowego przekształtnika fotowoltaicznego ze zmodyfikowanym generatorem kwadraturowym

Control of a photovoltaic converter connected to a single-phase grid requires synchronization with the fundamental component of the voltage. This is performed by the Park transformation of the measured voltage to a rotating orthogonal xy frame. This transformation in single-phase systems requires quadrature signals. The paper proposes that a quadrature generator replace the standard second-order generalized integrator

SIMULATION AND RESEARCH OF SINGLE-PHASE SHORT CIRCUITS IN THE ELECTRICAL NETWORK

The purpose of this work is to model single-phase short circuits in a three-phase electrical network and identify their type by analyzing the angular frequency of the spatial vector. Recently, the saturation of electric networks with powerful non-linear loads, the introduction of conversion equipment and renewable energy sources lead to the need for systematic analysis and research of the quality of electric energy (QEE). One of the factors that significantly affect the operation of electrical equipment is short circuits. In the article, based on the developed model of the formation of QEE distortions, a single-phase short circuit in a three-phase electrical network is investigated by switching it to a single-phase system with two α-β projections and a zero-sequence voltage vector.
 Studies of the influence of the location of the short-circuit point on the voltage in the electrical network have shown that the difference in the distance from the point of damage to the load, type of short-circuit leads to varying degrees of voltage change. Conducted studies have shown that different types of malfunctions and parameters of the electrical network at the point of short circuit cause different disturbances in the electrical voltage in the power supply system. The presence of a short circuit of the same type at different locations leads to different voltage drops and overvoltages. Short-term changes in voltage are the most common distortions of the quality of electrical voltage in electrical networks. The simulation results based on the developed model are consistent with the theory and reliably simulate the change in voltage in the electrical network.
 In the future, the presented model can help in creating a basis for the identification and subsequent control measures of voltage change violations.

Studying the features of simulating fluid movement in porous media

The study of fluid flow in porous media, differing from traditional pipe flow is crucial for developing efficient methods in oil extraction and minerals, considering the challenges associated with ambiguous flows and diverse porous structures. This paper addresses the complexity of investigating fluid flow in porous media, a phenomenon significantly distinct from fluid movement in pipes. Emphasis is placed on the absence of clearly defined flow tubes in porous media, complicating measurements, and analysis. The study introduces a new approach incorporating both analytical and numerical methods, applied to various porous media. The research proposes a mathematical model based on laws and correlations to describe systems, including concepts such as permeability, flow velocity potential, characteristics of single-phase and multiphase systems, and fluid compressibility. Special attention is given to the characteristics of oil reservoirs, determined based on fluid properties in the reservoir, including porosity and saturation, as assessed by engineers. Numerical results represent fluid displacement in a flat channel and a onedimensional problem in a porous medium, performed using finite-difference approximation of equations with an explicit scheme. The numerical results of this model were implemented in the Matlab software.

FILM-FORMING COMPOSITIONS BASED ON POLYURETHANEUREAS WITH EXTENDED RELEASE OF DACARBAZINE

Composite materials with dacarbazine (DK) containing 1 wt. % were obtained on the basis of polyurethane ureas (PUU) containing in the structure as extenders of the macrochain of 2-(2-aminoethoxy)ethan-1-amine, (DA1) 3,6-dioxaoctane-1,8-diamine (DA2) 3-{2-[2-(3-aminopropoxy)ethoxy]ethoxy}propan-1-amine (DA3) with a molar ratio of 4,4’-diaminodiphenylmethane (DADPh) to DA1 and DA3 as 30:70; 50:50; 70:30. The tensile strength of the compositions is within (1.21-1.27) MPa, the relative elongation is (303.9-384)%. Studies of thermophysical properties of synthesized PUU by DSC, TGA methods were conducted. Dacarbazine compositions are single-phase systems with glass transition temperature (Tg) from -33.55°C to -37.06°C. It was established that the introduction of Dacarbazine into the composition of PUU leads to a decrease in Tg and ΔCp during the second warm-up in comparison with the original PUU. Dacarbazine compositions are resistant to temperatures of 270oC, which allows for thermal sterilization before use. The release of Dacarbazine from polymer samples into the solution was studied by the spectrophotometric method. According to the results of the study of the dynamics release of Dacarbazine, it was es tablished that for (PUU DA1)2+DK in 14 days it is 61.74%, (PUU DA2)4+DK - 70.09%, (PUU DA3)2+DK - 56.75% of the total amount of immobilized DK. The resulting composites are perspective materials for medicine as means of local prolonged therapeutic action.

Influence of phase composition and crystal structure on the luminescent properties of calcium aluminates (CaAl2O4, CaAl4O7, CaAl12O19) activated by Eu3+ ions

Calcium monoaluminate, dialuminate, and hexaaluminate and luminophores based on them activated by europium (III) ions were obtained by the citrate-nitrate gel method. X-ray diffraction (XRD) and Full-Profile Rietveld refinement were used to establish the parameters of single-phase systems, to analyze the structure of the investigated compounds, and to determine the most probable sites of calcium substitution by the activator. The interpretation of the emission spectra has shown that europium occupies two crystallographic positions in calcium monoaluminate, while in dialuminate and hexaaluminate europium has only one crystallographic environment. Phosphor emission bands lie in the range from 580 to 720 nm, but the splitting of bands and their intensity are different. This is due to the different symmetry of the europium environment in the aluminate matrixes. This makes it possible to obtain phosphors of different hues of luminescence from the same starting materials, which is confirmed by the Commission Internationale de L'Eclairage (CIE) chromatic coordinate diagram.

CMAS corrosion behavior of dual-phase composite Gd2Si2O7/Sc2Si2O7 as a promising EBC material

Environmental barrier coatings (EBCs) applied to gas-turbine components require excellent corrosion resistance to molten siliceous debris such as sand or volcanic ash in high-temperature environments while maintaining mechanical integrity. To date, most research has focused on single-phase rare-earth (RE) disilicates as candidate EBC materials, but here we report the superior corrosion resistance of a dual-phase disilicate composite, namely Gd2Si2O7/Sc2Si2O7 (70/30 vol%). EBSD measurements of cross-sections of the EBC after exposure to a calcium magnesium alumino-silicate (CMAS) for 0.5, 2, 12, and 48 h at 1400°C reveal that, unlike in single-phase systems, the CMAS reaction layer consists of two distinct sublayers. The inner sublayer consists of a mixture of Ca2Gd8(SiO4)6O2 and Sc2Si2O7 crystals in a Ca-depleted glassy matrix, whereas the thinner outer region contains larger, elongated Ca2Gd8(SiO4)6O2 crystals oriented perpendicular to the composite surface and devoid of any Sc2Si2O7 crystals. The total thickness of the reaction layer is found to be about 20% less compared to that of single-phase Gd2Si2O7 under the same conditions, indicating that dual-phase RE-disilicate composites are a promising materials system for increasing the lifetime performance of EBCs.

Production of Phenylacetylcarbinol via Biotransformation Using the Co-Culture of Candida tropicalis TISTR 5306 and Saccharomyces cerevisiae TISTR 5606 as the Biocatalyst.

Phenylacetylcarbinol (PAC) is a precursor for the synthesis of several pharmaceuticals, including ephedrine, pseudoephedrine, and norephedrine. PAC is commonly produced through biotransformation using microbial pyruvate decarboxylase (PDC) in the form of frozen-thawed whole cells. However, the lack of microorganisms capable of high PDC activity is the main factor in the production of PAC. In addition, researchers are also looking for ways to utilize agro-industrial residues as an inexpensive carbon source through an integrated biorefinery approach in which sugars can be utilized for bioethanol production and frozen-thawed whole cells for PAC synthesis. In the present study, Candida tropicalis, Saccharomyces cerevisiae, and the co-culture of both strains were compared for their biomass and ethanol concentrations, as well as for their volumetric and specific PDC activities when cultivated in a sugarcane bagasse (SCB) hydrolysate medium (SCBHM). The co-culture that resulted in a higher level of PAC (8.65 ± 0.08 mM) with 26.4 ± 0.9 g L-1 ethanol production was chosen for further experiments. Biomass production was scaled up to 100 L and the kinetic parameters were studied. The biomass harvested from the bioreactor was utilized as frozen-thawed whole cells for the selection of an initial pyruvate (Pyr)-to-benzaldehyde (Bz) concentration ([Pyr]/[Bz]) ratio suitable for the PAC biotransformation in a single-phase emulsion system. The initial [Pyr]/[Bz] at 100/120 mM resulted in higher PAC levels with 10.5 ± 0.2 mM when compared to 200/240 mM (8.60 ± 0.01 mM). A subsequent two-phase emulsion system with Pyr in the aqueous phase, Bz in the organic phase, and frozen-thawed whole cells of the co-culture as the biocatalyst produced a 1.46-fold higher PAC level when compared to a single-phase emulsion system. In addition, the cost analysis strategy indicated preliminary costs of USD 0.82 and 1.01/kg PAC for the single-phase and two-phase emulsion systems, respectively. The results of the present study suggested that the co-culture of C. tropicalis and S. cerevisiae can effectively produce bioethanol and PAC from SCB and would decrease the overall production cost on an industrial scale utilizing the two-phase emulsion system with the proposed multiple-pass strategy.

Topology synthesis of integrated active power decoupling converters using asymmetrical H-bridge circuits

Aiming to handle the inherent double-line frequency ripple power in single-phase power systems, a lot of active power decoupling (APD) topologies have been developed. In this paper, a general method is introduced to synthesize APD topologies. The main construction idea is to insert a rectifier/inverter into asymmetrical H-bridge circuits (AHCs) or replace the switch/diode in the AHCs with a rectifier/inverter. This approach not only reveals the formation process of existing APD topologies but also deduces new APD topologies. Finally, an experimental case study has been carried out to illustrate the feasibility and effectiveness of the proposed topology synthesis method.

Design a 25-level inverter topology with less switching devices fed by PV systems

<span lang="EN-US">Multilevel inverter (MLI) technology has lately emerged as one of the most popular solutions for high power and medium voltage energy management. MLIs have many benefits and require more switches for higher levels, which are considered disadvantaged. This could result in large size and extremely expensive cost for the MLI. So, in order to overcome this problem, a new MLI topology is proposed with reduced number of switches. A 25‐level inverter fed by isolated unequal photovoltaic panels as DC sources is chosen in this study. The structure of DC voltages is chosen as (1:1:5:5) Vdc. The proposed approach, which is created using twelve switches, is ideally suited for a high-power application. Multi-carrier with a sinusoidal PWM technique is programmed as a controller. According to the simulation findings, a single-phase system's output voltage and current total harmonic distortion (THD) values are 1.2% and 0.462%, respectively, while a three-phase system's values are 1.07% and 0.342%. These findings prove that the power circuit and investigation were successful.</span>

SISTEM PROTEKSI DAN MONITORING KESEIMBANGAN BEBAN TIGA FASA PADA JARINGAN DISTRIBUSI TEGANGAN RENDAH MENGGUNAKAN MIKROKONTROLER BERBASIS IOT

Three-phase electrical systems are widely used by industrial consumers because of their large power requirements. The 3-phase system is more economical in the delivery of electrical power than the single-phase system because the conductor used is smaller for the same power. A 3-phase system is said to be balanced if the load used is also balanced between the three R-S-T phases. However, in practice the balance of the three phases is very difficult to achieve because the electrical load of each house or industry is not necessarily identical. As a result of this imbalance between the R-S-T phases can cause damage to electronic equipment that uses 3-phase electricity if used continuously.According to PUIL 2011 the unbalance distribution system includes an unbalanced current between phases with provisions up to a tolerance value of 10%. In a 3 phase electrical distribution system, there will often be load imbalances. This is due to the addition or use of electrical loads that do not pay attention to the imbalance in the system.For this reason, in this study, a tool that uses the PZEM-004T sensor, Wemos D1 mini module, and Android Studio was created which can allow for remote monitoring using electronic devices that have installed applications that have been created. when an error occurs, the "reset" button on the monitoring application is used to reset the protection to restore the device. The current difference in the avometer is 1.48A and the sensor is 1.46A and the current flowing to the load is written 1.88A. The contactor works when the relay receives a command from the Arduino nano with a fast time, namely: 1.60 seconds on the first try, 1.72 seconds on the second experiment, and 1.68 seconds on the third experiment.

Grid Equivalent Representation of Power Systems With Penetration of Power Electronics

The Thévenin equivalent is considered as the standard grid equivalent for power system analysis. The integration on power electronics components in the power systems introduces non-linear operation characteristics that cannot be captured by Thévenin equivalent. Therefore, an alternative grid equivalent representation is required. This paper presents a steady-state equivalent representation of power systems with penetration of power electronics, which is suitable for both normal operation studies and short-circuit calculations. This equivalent grid representation is developed based on the voltage-current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U-I</i> ) characteristic of a power system to map the relationship between voltages and currents of a specific network node. Such grid equivalent representation has been presented for single-phase, balanced and unbalanced three-phase power systems in this paper. A methodology is presented to identify operation points when the equivalent system under study is connected to any external system. The proposed equivalent grid representation and the methodology for operation points identification have been tested on the Voltage Source Converter (VSC) based test system and are validated through dynamic simulations.