Search Results (20)

This paper presents a comparative analysis of interior permanent magnet synchronous motor (IPMSM) drives powered by symmetrical and asymmetrical cascaded H-bridge multilevel inverters. The asymmetric topology operates using multiple DC sources with different voltage values, generating a voltage waveform with more output voltage levels than its traditional counterpart, all while maintaining the same hardware configuration. The main goal is to demonstrate that asymmetrical multilevel inverters are a promising option for improving the performance of electric drives while maintaining cost-efficiency and reliability. The proposed comparison is conducted through simulations in the MATLAB/Simulink R2024a environment, which allows an in-depth analysis of the dynamic performance of the electric drive. Additionally, the variation of the DC link input power of each H-bridge and the Total Harmonic Distortion (THD) of the voltage and current of the output of the converters were studied for different operating conditions in both cases. The obtained results were confirmed through real-time validation, demonstrating the applicability of electric drives powered by asymmetric converters and the advantages, in terms of efficiency, harmonic content and dynamic performance, in certain conditions of operation in terms of speed and applied load. Full article

The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely. Full article

Semiconductor lasers, characterized by their high efficiency, small size, low weight, rich wavelength options, and direct electrical drive, have found widespread application in many fields, including military defense, medical aesthetics, industrial processing, and aerospace. The mode characteristics of lasers directly affect their output performance, including output power, beam quality, and spectral linewidth. Therefore, semiconductor lasers with high output power and beam quality are at the forefront of international research in semiconductor laser science. The novel parity–time (PT) symmetry mode-control method provides the ability to selectively modulate longitudinal modes to improve the spectral characteristics of lasers. Recently, it has gathered much attention for transverse modulation, enabling the output of fundamental transverse modes and improving the beam quality of lasers. This study begins with the basic principles of PT symmetry and provides a detailed introduction to the technical solutions and recent developments in single-mode semiconductor lasers based on PT symmetry. We categorize the different modulation methods, analyze their structures, and highlight their performance characteristics. Finally, this paper summarizes the research progress in PT-symmetric lasers and provides prospects for future development. Full article

One of the greatest options to address the growing need for hybrid energy storage systems is a supercapacitor with high specific capacitance, high power density, and more charge and discharge cycles. The valorization of walnut shells, a bio waste, into an activated biocarbon electrode material for the symmetric electric double-layer supercapacitor (EDLC), has been carried out. The valorization method comprises of two-steps for the synthesis of activated biocarbon which are thermal carbonization and ZnCl₂ chemical activation of walnut shells at 700 °C. The sample has good long-term stability and a specific capacitance of 50 Fg⁻¹ @1 Ag⁻¹, making it an excellent supercapacitor electrode material. So, the symmetric electric double-layer capacitor’s (EDLC) promising electrode material was found to be porous AC samples made from walnut shells. Full article

Fifth-generation (5G) technology has enabled faster communication speeds, lower latency, a broader range of coverage, and greater capacity. This research aims to introduce a bidirectional high-speed passive optical network (HS-PON) for 5G applications and services including mobile computing, cloud computing, and fiber wireless convergence. Using 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing techniques, the system transmits uplinks and downlinks with a pair of four wavelengths each. Light fidelity (LiFi) services are provided with blue light-emitting-diode-based technology. With a threshold bit error rate (BER) of 10⁻³, the results demonstrate reliable transportation over a 100 km fiber at −17 dBm received power and in a maximum LiFi range of 20 m. Furthermore, the system offers symmetric 4 × 50 Gbps transmission rates under the impact of fiber–LiFi channel impairments with maximum irradiance and incidence half-angles of 500. Additionally, at threshold BER, the system provides a detection surface range from 1.5 to 4 cm². Compared to existing networks, the system also provides a high gain and low noise figure. A number of features make this system an attractive option. These include its high speed, high reach, high split ratio, low cost, easy upgradeability, pay-as-you-grow properties, high reliability, and ability to accommodate a large number of users. Full article

In this paper, a heuristic approach to doubly fed induction generator (DFIG) protection and low voltage ride through (LVRT) is carried out. DFIG-based wind systems are rapidly penetrating the power generation section. Despite their advantages, their direct coupling grid makes them highly sensitive to symmetrical faults. A well-known solution to this is the crowbar method of DFIG protection. This paper provides a method to determine the optimal crowbar resistance value, to ensure a strong trade-off between the rotor current and DC voltage transients. Further, since the crowbar method requires disconnection from the grid, the linear quadratic regulator (LQR) is applied to the system. This is to ensure fault ride through compliance with recent grid code requirements. The well-known PSO, as well as the recently developed African vultures optimization algorithm (AVOA), was applied to the problem. The first set of results show that for severe symmetrical voltage dips, the AVOA provides a good option for crowbar magnitude optimization, whereas PSO performed better for moderately severe dips. Secondly, when the LQR was optimized via the AVOA, it exhibited superiority over the conventional PSO-based PI controller. This superiority was in terms of rotor current transient magnitude, DC voltage transient magnitude, and reactive power steady-state ripple and were in the order of 67.5%, 20.35%, and 37.55%, respectively. When comparing the crowbar method and the LQR, it was observed that despite the LQR exhibiting superiority in terms of transient performance, the crowbar method offered a unanimously superior settling time. Full article

Photovoltaic system condition monitoring can be performed via single-diode model fitting to measured current–voltage curves. Model parameters can reveal cell aging and degradation. Conventional parameter identification methods require the measurement of entire current–voltage curves, causing interruptions in energy production. Instead, partial curves measured near the maximum power point offer a promising option for online condition monitoring. Unfortunately, measurement data reduction affects fitting and diagnosis accuracy. Thus, the optimal selection of maximum power point neighbourhoods used for fitting requires a systematic analysis of the effect of data selection on the fitted parameters. To date, only one published article has addressed this issue with a small number of measured curves using symmetrically chosen neighbourhoods with respect to the maximum power. Moreover, no study has determined single-diode fit quality to partial curves constructed via other principles, e.g., as a percentage of the maximum power point voltage. Such investigation is justified since the voltage is typically the inverter reference quantity. Our work takes the study of this topic to a whole new scientific level by systematically examining how limiting the current–voltage curve measuring range to maximum power point proximity based on both power and voltage affects single-diode model parameters. An extensive dataset with 2400 measured curves was analysed, and statistically credible results were obtained for the first time. We fitted the single-diode model directly to experimental curves without measuring outdoor conditions or using approximations. Our results provide clear guidance on how the choices of partial curves affect the fitting accuracy. A significant finding is that the correct selection of maximum power point neighbourhoods provides promising real-case online aging detection opportunities. Full article

In this study, the variants of structures are considered for fission fragments of the 235U nucleus caused by thermal neutrons, depending on differences in the initial configuration of proton, neutron and alpha particle compositions, according to a symmetrical model developed for the atomic nucleus. The proposed model is based on the principles of spatial symmetry and the analysis of the binding energy of the nucleus, taking into account the quark structure of nucleons. For the first time, the number of alpha particles in the composition of the 235U nucleus is considered to be 44 and the total number of connections between nucleons is 292. The work compares the binding energy of fragments of the atomic nucleus 235U, which have the same number of protons and neutrons in their composition, but a different number of alpha particles. The results obtained are the basis for an experimental study on the energy characteristics of various fission options of the 235U+n reaction, which is of interest for improving the efficiency of nuclear power sources. Full article

Multilevel inverters (MLIs) have emerged as a feasible option for medium-voltage energy conversion applications with excellent power quality. These inverters have exhibited different advantages over the two-level inverters due to the development of various modulation schemes. In recent years, they have received a lot of attention for a variety of industrial applications, including adjustable speed drives, renewable energy systems, electric vehicles and uninterruptible power supply. The main aim of this paper is to propose a new symmetric- and asymmetric-type multilevel inverter circuit with a reduced number of circuit components. The proposed circuit consists of three DC voltage sources and nine power electronic switches. The proposed topology creates a staircase-type 7-level output voltage waveform under a symmetric condition and a 15-level output voltage waveform under an asymmetric condition, with fewer components and low total harmonic distortion, without using an active filter circuit. A comprehensive comparative analysis is presented to illustrate the advantage of the proposed inverter circuit. The performance of the proposed MLI is verified through many simulation studies in MATLAB/Simulink. Furthermore, to highlight the merits and superiorities of the suggested MLI, a full comparison is performed with the best performance of the existing MLI topologies. Full article

The electric power industry has a dominant contribution to economic development in China, and growth in the industry needs to help the economy grow, protect the environment, and give people access to electricity. The current study’s main goal is to assess the rural and urban populations’ access to electricity, energy use, and economic development in China using yearly data ranging from 1995 to 2017. We applied two unit root tests to check the variables’ stationarity and a symmetric autoregressive distributed lag (ARDL) approach to discover the variable links using long-run and short-run estimates. The Granger causality test was also used in this study under a vector error correction model (VECM) to assess the variables’ unidirectional connection. Short-run results demonstrate that total population access to electricity, urban population access to electricity, and energy use have positive links with economic development, with probability values of (0.004), (0.000), and (0.007), respectively. Similarly, long-run evidence shows that variables such as total population access to electricity, urban population access to electricity, and energy use have a positive relationship with economic growth, with p-values of (0.005), (0.000), and (0.047), respectively. Unfortunately, throughout the investigation, the variable electricity availability to the rural population demonstrated an adverse relationship with China’s economic growth. Furthermore, the Granger causality test results under the vector error correction model (VECM) show that all variables have unidirectional links. China’s implementation of new plans regarding energy consumption has a significant impact on both future energy supply and the country’s ability to stay sustainable. It will be able to maintain the stability of its energy levels as long as it sticks to suitable choices and policy options. Undoubtedly, China is a huge user of energy and an emitter of CO₂ emissions; therefore, possible conservative strategies and policies are required from the Chinese government to use clean energy sources to fulfill its energy demand. Full article

In our previous study, we proposed a perfectly secure Shannon cipher based on the so-called matrix power function. There we also introduced a concept of single round symmetric encryption, i.e., we used the matrix power function together with some rather simple operations to define a three-step encryption algorithm that needs no additional rounds. Interestingly enough, the newly proposed Shannon cipher possesses the option of parallelization—an important property of efficiently performing calculations using several processors. Relying on our previous proposal, in this study we introduce a concept of a one round block cipher, which can be used to encrypt an arbitrary large message by dividing it into several blocks. In other words, we construct a block cipher operating in cipher block chaining mode on the basis of the previously defined Shannon cipher. Moreover, due to the perfect secrecy property of the original algorithm, we show that our proposal is able to withstand the chosen plaintext attack. Full article

At present, primary power generation depends on non-renewable energy resources, which will become extinct. Solar is the best option in renewable energy sources to achieve clean and green power extraction. Solar PV transforms light energy into electrical energy. However, the output power of solar PV changes with solar insolation. It is also affected by environmental factors and the shading effect. One of the key factors that can reduce the PV system output power is partial shading condition (PSC). The reduction in power output not only depends on shaded region but also depends on pattern of shading and physical position of shaded modules in the array. Due to PSCs, mismatch losses are induced between the shaded modules which can cause several peaks in the output power-voltage (P-V) characteristic. This article describes the non-symmetrical reconfiguration technique and compares it with the primary total cross tied connection. The performance of non-symmetrical reconfiguration techniques is evaluated and compared in terms of global maximum power (GMP), voltage and currents at GMP, open and short circuit voltage and currents, mismatch power loss (MPL), fill factor, efficiency, and number of local maximum power peaks (LMPPs) on a 9 × 9 PV array. Full article

Under the current situation, it is necessary to harness solar energy to generate more electricity. However, the disadvantage of solar energy is that it takes a lot of space to install solar panels. An option to optimize PV systems is to improve the maximum power point tracking (MPPT) algorithm based on symmetrical management has the advantage of being easy to use without updating the devices. The improved algorithm achieves symmetry between the maximum power point (MPP) and the output of the PV array, resulting in less power loss and increased system efficiency. This paper presents the MPPT of photovoltaic using the current control modifier perturbation and observation plus fuzzy logic control (CCMP&O−FLC MPPT). The algorithm of CCMP&O−FLC MPPT is applied to reduce the setting time and to reduce oscillation around the set-point at a steady state. This concept was experimented with using a boost converter with MATLAB/Simulink software package and implemented by STM32F4VGA microcontroller. The simulation and experiment results are obtained by comparison with traditional P&O under similar operating conditions. The CCMP&O−FLC MPPT can track MPP faster when the irradiation is rapidly changing and, therefore, can reduce the PV system losses. In addition, the advantages of this proposed method can also be applied to improve the performance of existing systems without modifying existing equipment, unlike modern methods that cannot be applied to older systems. The results showed that the MPPT time and the power output efficiency of the proposed algorithm were 146 milliseconds and 99.5%, respectively. Full article

The success of launching new products is the main challenge of companies since it is one of the key factors of competition. Thus, success in today’s high rival markets depends on the presentation of new products with new options, which must be compatible with customers’ desires. This research aims to analyze the psychological effect of the noise of a new product on the total profit of the chain and the optimal pricing and marketing decisions of the chain’s members. Additionally, a cooperative (co-op) advertising strategy as a coordination mechanism is considered among the partners such that it helps them to obtain their target markets. Commonly, under co-op advertising, the manufacturer pays a percentage of the retailer’s advertising costs. In this chain, the manufacturer and the retailer agree to share the retailer’s advertising costs. Afterwards, four different relations between the manufacturer and retailer are studied and analyzed including three non-cooperative games with symmetrical distribution of market power and one asymmetrical distribution of it. So, four game models and their closed-form solutions are illustrated with a numerical example. It was found that the noise effect affects the total profit of the manufacturer and the retailer, as well as the supply chain by influencing the partners’ advertising policies. In other word, increasing the noise effect of the product indicates to the manufacturer and the retailer to globally and locally advertise more, respectively. In turn, their profits increase, although also increasing the advertising costs. Finally, a complete sensitivity analysis is conducted and reported. Full article

Ionic liquids are potential alternative electrolytes to the more conventional solid-state options under investigation for future energy storage solutions. This review addresses the utilization of IL electrolytes in energy storage devices, particularly pyrrolidinium-based ILs. These ILs offer favorable properties, such as high ionic conductivity and the potential for high power drain, low volatility and wide electrochemical stability windows (ESW). The cation/anion combination utilized significantly influences their physical and electrochemical properties, therefore a thorough discussion of different combinations is outlined. Compatibility with a wide array of cathode and anode materials such as LFP, V₂O₅, Ge and Sn is exhibited, whereby thin-films and nanostructured materials are investigated for micro energy applications. Polymer gel electrolytes suitable for layer-by-layer fabrication are discussed for the various pyrrolidinium cations, and their compatibility with electrode materials assessed. Recent advancements regarding the modification of typical cations such a 1-butyl-1-methylpyrrolidinium, to produce ether-functionalized or symmetrical cations is discussed. Full article