Laboratory Prototype Research Articles

A new configuration of DC-DC converter with increased voltage gain for photovoltaic application

ABSTRACT The output voltage in photovoltaic solar panels is usually low. Therefore, DC-DC step-up converters are employed in these systems to increase the voltage level. A new topology with interleaved non-isolated high gain is suggested for photovoltaic application in the present paper where a combination of two voltage multipliers was used to increase the voltage gain. Employing the interleaved technique reduced the input current ripple. The voltage stress is significantly reduced across the semiconductor components, making it possible for the converter to use high-performance components, and therefore reducing conduction losses. Analysis was performed, and comparisons are presented among the proposed converter and seven similar converters. A 170-watt laboratory prototype with 12.5 V input and 170 V output voltages was fabricated for experimental assessment of the converter’s performance. Finally, experimental results were analysed and compared with analytical results.

High‐efficiency multilevel inverter topology with minimal switching devices for enhanced power quality and reduced losses

AbstractThe advent of multilevel inverters (MLIs) has brought significant advancements in their applications across industrial, residential, and renewable energy sectors, as they produce high‐quality output voltage that closely approximates a sinusoid in small voltage steps or levels, resulting in lower total harmonic distortion (THD) and reduced electromagnetic interference (EMI). However, the MLI topologies require more switching unidirectional/bidirectional semiconductor devices with high standing voltage, gate drivers, and complex control strategies while attaining higher voltage levels. From this perspective of reducing component count and gate drivers, the objective is to develop a new MLI topology that overcomes the drawbacks above. In this article, a novel MLI topology is introduced in symmetric and asymmetric configurations aiming to attain fewer power electronic devices for synthesizing more steps in the load voltage in contrast with conventional topologies. The idea behind the approach is coining the series connected voltage source, which imbibes bidirectional current flow with an additional voltage source for performing algebraic operation under asymmetrical modes of operation. The proposed topology uses minimal on‐state switching devices leading to a diminution of power loss and voltage drop. The suggested topology is optimized for a fewer number of power devices, an input DC supply, and auxiliary gate drivers to achieve a maximum voltage level in the load terminals. The suggested topology has been verified in SIMULINK and the laboratory prototype is constructed in line with the simulated response to demonstrate its performance suitable for real‐time applications.

Experimental Evaluation of a Proposed LQR-LU Optimal Grid Controller in the Applications of Grid-Tied PV Systems

This article aims to design a linear quadratic regulator (LQR)-based optimal current controller along with a Luenberger observer model in order to enhance power quality during the grid's dynamic conditions. To analyze the performance of the proposed control scheme, a three-phase photovoltaic-based gird-tied inverter is considered. A grid controller comprises a DC-link voltage controller to stabilize the capacitor voltage and a current controller to assure the output currents are well controlled according to the dynamic conditions of the grid as well as the source. In general, the capacitor-voltage and current controllers are regulated by traditional proportional Integral (PI) controllers which is associated with many demerits. In this work, a predictive LQR-based current controller with an observer algorithm and an adaptive capacitor voltage controller is proposed to improve the performance of the power grid at various dynamic conditions. The mathematical analogy is evaluated using MATLAB/SIMULINK software with different load and grid-disturbance conditions. Moreover, a laboratory prototype is designed to validate the simulation results. The outcomes prove that the proposed controller is dynamically robust to tackle any disturbance in load and grid.

Multi-Objective Optimization of SEPIC-Cuk Converter for Photovoltaic Application

This paper investigates the optimization of SEPIC-Cuk DC-DC converters to enhance efficiency and compactness, addressing the increasing demands of modern power converters. Given the topological structure, a paralleling approach is crucial due to its potential to improve both size and performance. Utilizing a bipolar SEPIC-Cuk configuration, this research meticulously evaluates, refines, and validates an experimental prototype of a bipolar DC-DC converter. To achieve optimal outcomes, the investigation employs a multi-objective metaheuristic optimization technique, focusing on efficiency and size attributes to design a cost-effective converter. The selection of design parameters - including switching frequency, capacitance, inductance, and power electronic switches - is integral to the optimization process. The proposed converter features a single switch control mechanism to operate a single input and dual output structure, ensuring high efficiency while enhancing converter response and minimizing ripple. A laboratory prototype of a low-cost 300 W converter, designed for a bipolar DC microgrid as a photovoltaic optimizer, has been developed and tested, accommodating an input voltage range of 20 V to 60 V and supporting standard output voltages. Experimental results demonstrate an average efficiency of 97.5% and 98.35% for a 300 W load, validating the effectiveness of the proposed strategy. Additionally, a comprehensive comparison between theoretical predictions and experimental findings is presented, confirming the validity and applicability of the proposed methodology.

Development of a rapid antigen-based lateral flow assay for tick-borne spotted fever rickettsioses.

Tick-borne spotted fever rickettsioses (SFRs) continue to cause severe illness and death in otherwise-healthy individuals due to lack of a timely and reliable diagnostic laboratory test. We recently identified a diagnostic biomarker for SFRs, the putative N-acetylmuramoyl-l-alanine amidase RC0497. Here, we developed a prototype laboratory test that targets RC0497 for diagnosis of SFRs. The concentrations of RC0497 in sera of Rickettsia rickettsii-infected guinea pigs and R. conorii-infected mice were determined by stable isotope dilution-parallel reaction monitoring mass spectrometry (SID-PRM-MS), ranging from 0.1 to 1.1 ng/ml. Using europium chelate nanoparticle reporters, we developed a lateral flow assay (LFA) and evaluated the test with a panel of serum samples of mock and experimentally infected animals. Interestingly, 21 of 22 (95.5%) serum samples from R. rickettsii-infected guinea pigs and R. conorii-infected mice yielded positive results with a ratio of test line / control line greater than the cutoff value determined for non-infected animals. All uninfected samples were in agreement with the intended results, suggesting that the initially assessed specificity of the test is 100%, among these samples. Mice infected with a lethal dose of R. conorii and treated with doxycycline on day 3 post-infection (p.i.), upon RC0497 detection by LFA, displayed significantly decreased rickettsial loads, comparable to the sublethal infection group on day 5 p.i.. A panel of human serum samples spiked with various concentrations of recombinant RC0497 were analyzed by LFA, suggesting that the limit of detection of the LFA was 0.64 ng/mL. These findings suggest that the timely detection of RC0497 by a europium LFA offers guidance for treatment, leading to a significant improvement in infection outcomes. This work, for the first time, shows significant promise for a rapid and easy-to-use platform offering a timely diagnostic assay for severe SFRs.

Classification and Prediction of VOCs Using an IoT-Enabled Electronic Nose System-Based Lab Prototype for Breath Sensing Applications

Classification and Prediction of VOCs Using an IoT-Enabled Electronic Nose System-Based Lab Prototype for Breath Sensing Applications

A method of Increasing the Area of the Herbage on Mountain Forage Lands

The present study reveals that up to 60 percent of mountain grasslands are strewn with stones. Their removal can significantly expand forage land and decrease animal injuries. It has been found out that there are no small-sized units capable of removing stones on sloped terrains. (Research purpose) The research aims to develop and construct a laboratory prototype of a stone removal unit adapted to the Feng Shou 180 mini-tractor, specifically for use on slopes. This unit is intended to facilitate the rehabilitation of mountain regions that are otherwise unsuitable for livestock farming, and enhance soil resistance to both water and wind erosion. (Materials and methods) The technology has been substantiated and the unit prototype has been constructed. The tests were conducted in the mountainous area of the Republic of North Ossetia-Alania, at an altitude of 1540 meters above sea level. The stones were removed from a section of the northern slope with a steepness of 13 degrees in the village of Dargavs. Technical expertise, bench and field tests of the unit were performed in accordance with agrotechnical standards and technical specifications. (Results and discussion) As a result a laboratory prototype of a stone removal unit adapted to the Feng Shou 180 mini-tractor was produced. It is determined that the laboratory prototype meets the agrotechnical standards and technical specifications. The unit proves to effectively remove stones larger than 30 millimeters with an efficiency rate of 91-93 percent. Additionally, it has been demonstrated that the first year of using the unit results in a 90-95 percent increase in the productivity of forage lands. (Conclusions) The use of this unit on mountain slopes significantly enhances the usable area and improves the water-air and nutrient regimes. This adjustment also alters the species composition of the vegetation, increasing the legume component to 16.7 percent and the cereal component to 47.3 percent. Our findings underscore the potential benefits and feasibility of further developing and deploying this prototype on densely stoned forage lands with slopes of up to 13 degrees.

Production of face protectors by 3d printing: distribution of PPE to face the coronavirus

Purpose: The aim of this study is to produce face shields using 3D printing, contributing to the personal protection of healthcare professionals from both public and private health institutions amid the coronavirus pandemic. Theorical framework: At the beginning of the Covid-19 pandemic, it became common for health professionals to report on the scarcity of Personal Protective Equipment (PPE) in their work, which resulted in the high level of contamination of those involved in the front line. The face shield stood out as one of the missing PPEs, important for the health and safety of workers as they offer a physical barrier to contamination by secretions. Methodology/Approach: For this purpose, through the Center for Robotics, Innovation, and Entrepreneurship (CRIE), the prototyping laboratory of the Federal Institute of Minas Gerais campus Governador Valadares (IFMG-GV), different models of face shields were tested. The model that provided the greatest comfort for users was selected, while also requiring less printing time and using less raw material. The production was carried out in accordance with Resolution 356/2020 of the National Health Surveillance Agency (ANVISA), which authorized and decentralized the production of large industries in an extraordinary and temporary manner. Findings: Requirements for the manufacture, importation, and acquisition of medical devices were defined. In total, 223 face shields were produced and donated to the city's healthcare system, serving the Unimed Hospital, the Medical Association, and other local hospitals. Research, practical & social implications: From the action, the IFMG-GV, as a public educational institution, played its role by providing support to local society, influenced by the consequences of the pandemic. Keywords: Covid-19; Face shield printing; 3d printing.

A Current‐Fed Switched Capacitor Inverter With Voltage Boosting, Reduced Harmonic Distortion, and Minimal Device Count

ABSTRACTDC–AC inverters are an important set of power converters when it comes to integration of the renewable energy resources in to the AC grid or to local AC loads. The multilevel inverters (MLIs) are a common and popular choice for such applications. However, MLIs require many switching devices for higher number of voltage levels, multiple isolated DC sources, need for additional charge‐balancing circuits for the DC‐link capacitor, and unequal voltage stress in the devices at higher power levels. Switched capacitor–based inverters are emerging as a popular alternative to the conventional MLIs that do provide inherent charge balancing, reduced device stress, output voltage–boosting capability, and highly compact converters. This work proposes such a current‐fed DC–AC switched capacitor converter (SCC). This converter offers advantages such as reduced count of switched capacitors and power devices, elimination of load‐side filtering elements, reduced switching ripple in output voltage due to inherent interleaving, reduced voltage and current total harmonic distortion (THD), and lower ratings of the switched capacitors. An adaptive hysteresis control scheme is used to track the voltage across the switched capacitors to a desired sinusoidal reference. The overall control architecture is straightforward to implement, and the switching architecture uses overlapping logic to prevent interrupting the input current. The work includes a complete analysis and design procedure. A 500‐W laboratory prototype of the proposed converter is built, with the control architecture implemented using the TMS320F28379D microcontroller. Simulation results are verified with experimental outcomes.

Novel Single-Stage Electrolytic Capacitor-Less Buck-Boost Inverter

Nowadays, single-phase, single-stage, buck-boost power inverters are mostly considered to be used for renewable energy source applications due to their wide range of capabilities. This article introduces a novel, single-phase, single-stage, buck-boost inverter with a wide range of input DC voltage. In addition, the introduced inverter does not use the electrolytic capacitor, which enhances the lifetime and volume reduction in the inverter, avoids the high equivalent series resistance, and reduces the inrush current of electrolytic capacitors in the introduced inverter. Moreover, the introduced inverter exhibits a reduced switch voltage rating, and the novel PWM control strategy with the half-cycle of the sinusoidal is derived to reduce the switching loss of power switches, thus improving the inverter’s efficiency. The operation states, theoretical analysis, and design of components are fully discussed. A comparative study of the introduced inverter with other buck-boost inverter topologies is also reported. Finally, the 500 W laboratory prototype is set up for simulation and experimental verification. The experimental results verify the correctness of operating analysis and simulation.

Simulation and Modeling of Data Transmission Process in Boreholes Using Intelligent Drill Pipe for a Laboratory Experiment

Currently, most oil and gas wells are drilled by continuously transmitting downhole measured information (directional and geological information) in real-time to the surface to monitor and steer the well along a pre-defined path. The intelligent drill pipe method can transmit data over longer distances and at a higher rate than other methods, such as mud pulse telemetry, acoustic telemetry, and electromagnetic telemetry. Nevertheless, it is expensive and requires boosters along the drill string. In the available literature, academic research rarely addresses the data transmission process in boreholes using intelligent drill pipes. Furthermore, there is a need for an effective and validated model to study various controllable parameters to enhance the efficiency of the intelligent drill pipe telemetry without the need to develop several physical lab or field prototypes. This paper presents the development of a model based on MATLAB Simulink to simulate the process of data transmission in boreholes utilizing intelligent drill pipes. Laboratory experimental prototype measurements have been used to test the model’s effectiveness. A good correlation is found between the measured lab data and the model’s predictions for the signals transmitted contactless through intelligent drill pipes with a correlation coefficient (R2) above 0.9. This model can enhance data transmission efficiency via intelligent drill pipes, study different concepts, and eliminate the need to develop several unnecessarily expensive and time-consuming physical lab prototypes.

Applied body-fluid analysis by wearable devices.

Wearable sensors are a recent paradigm in healthcare, enabling continuous, decentralized, and non- or minimally invasive monitoring of health and disease. Continuous measurements yield information-rich time series of physiological data that are holistic and clinically meaningful. Although most wearable sensors were initially restricted to biophysical measurements, the next generation of wearable devices is now emerging that enable biochemical monitoring of both small and large molecules in a variety of body fluids, such as sweat, breath, saliva, tears and interstitial fluid. Rapidly evolving data analysis and decision-making technologies through artificial intelligence has accelerated the application of wearables around the world. Although recent pilot trials have demonstrated the clinical applicability of these wearable devices, their widespread adoption will require large-scale validation across various conditions, ethical consideration and sociocultural acceptance. Successful translation of wearable devices from laboratory prototypes into clinical tools will further require a comprehensive transitional environment involving all stakeholders. The wearable device platforms must gain acceptance among different user groups, add clinical value for various medical indications, be eligible for reimbursements and contribute to public health initiatives. In this Perspective, we review state-of-the-art wearable devices for body-fluid analysis and their translation into clinical applications, and provide insight into their clinical purpose.

Bridgeless Cuk PFC converter with full load range soft switching operation by using a simple auxiliary circuit

This paper proposes a fully soft-switched bridgeless Cuk converter for power factor correction. The main converter utilizes a common ground structure with a single switch, simplifying the trigger signal generation and eliminating the need for positive and negative half-line cycle detection. This switch operates under Zero Voltage Switching (ZVS) enabled by a simple auxiliary circuit with just one switch. This auxiliary switch achieves Zero Current Switching (ZCS). Full soft switching allows for increased switching frequency without compromising efficiency, leading to a reduction in the size of passive components. Additionally, the shared ground between input and output minimizes Electromagnetic Interference (EMI) noise. The converter operates in Discontinuous Conduction Mode (DCM) to simplify the control circuit and inherently provides power factor correction without requiring an input filter due to the presence of input inductor and continuous nature of the input current. To validate the theoretical analysis, a laboratory prototype with 200 W output power, 80V output voltage, and 150kHz switching frequency is implemented. The results demonstrate the maximum theoretical and experimental efficiency of almost 96.2% and 95.8%, while, the full load theoretical and experimental efficiency is around 96% and 95.4%, in sequence. Also, an input current Total Harmonic Distortion (THD) and Power Factor (PF) of around 5.2% and 0.998 at full load is achieved, respectively.

Sensitivity Analysis of a Stator Current-based MRAS Estimator for Sensorless Induction Motor Drives

The sensitivity of speed estimators for parameter variations presents a significant challenge for sensorless Induction Motor (IM) drives, particularly at very low speeds. This paper examines the impact of parameter variations and the PI adaptation mechanism on the stator current-based Model Reference Adaptive System (MRAS). In contrast to the estimation of rotor flux, the MRAS method uses the observed stator current and the stator current estimate error within the adjustable IM model. The stability analysis for changes in machine parameters and PI controller gains is examined using small-signal perturbation. Additionally, a sensitivity analysis of stator and rotor resistance changes is included. A complete simulation using MATLAB/Simulink and experimental validation using a laboratory prototype based on the DSP-DS1103 are provided. The analytical, modeling, and measurement results reveal that the suggested observer responds well and provides precise speed estimation in all four quadrants of operation.

Nonlinear Analysis and Solution for an Overhead Line Magnetic Energy Harvester with an Active Rectifier

Recently, there has been a significant focus on developing various energy harvesting technologies to power remote electronic sensors, data loggers, and communication devices for smart grid systems. Among these technologies, magnetic energy harvesting stands out as one straightforward method to extract substantial power from current-carrying overhead lines. Due to the relatively small size of the harvester, the high currents in the distribution system quickly saturate its magnetic core. Consequently, the magnetic harvester operates in a highly nonlinear manner. The nonlinear nature of the downstream AC to DC converters further complicates the process, making precise analytical modeling a challenging task. In this paper, a clamped type overhead line magnetic energy harvester with a controlled active rectifier generating significant DC output power is investigated. A piecewise nonlinear analytical model of the magnetic harvester is derived and reported. The modeling approach is based on the application of the Froelich equation. The chosen approximation method allowed for a complete piecewise nonlinear analytical treatise of the harvester’s behavior. The main findings of this study include a closed-form solution that accounts for both the core and rectifiers’ nonlinearities and provides an accurate quantitative prediction of the harvester’s key parameters such as the transfer window width, optimal pulse location, average DC output current, and average output power. To facilitate the study, a nonlinear model of the core was developed in simulation software, based on parameters extracted from core experimental data. Furthermore, theoretical predictions were verified through comparison with a computer simulation and experimental results of a laboratory prototype harvester. Good agreement between the theoretical, simulation, and experimental results was found.

Dynamic characteristics of wave entry for a deep-sea mining vehicle: Numerical and experimental studies

The deep-sea mining vehicle (DSMV) experiences complex impacts upon the wave entry, which directly affects the safety and reliability of the whole deployment system. In this paper, a computational fluid dynamics (CFD) method is proposed to investigate hydrodynamic properties and wave-entry effects of a DSMV with varying laying speeds. Firstly, a fifth-order Stokes surface gravity wave simulating Sea State 4 conditions is constructed based on the volume of fluid (VOF) method. Then, the overset mesh scheme is utilized to establish the multiple degree-of-freedom (DOF) model of DSMV which bears the traction loads of laying cable. Laboratory prototype tests are conducted, and the captured results of cavitation evolution and motion properties corroborate the present model. Numerical results indicate that the DSMV entering the wave danger point will experience hydrodynamic forces several to dozens of times greater, severely threatening structural safety. During the wave entry process, two phases of nonlinear deceleration occur, posing a risk to the umbilical cable. Surge and pitch motions caused by waves and structural asymmetry may lead to deployment position deviation. Based on the trends observed in the simulation data, guidance for deployment operations has been proposed.

An innovative high-gain multi-stage non-isolated step-up converter controlled by optimal interval type-2 fuzzy system based maximum power point tracking

In photovoltaic (PV)-based power generation systems, the conventional and interleaved boost converter undertakes a pivotal task by augmenting its low output voltage to high voltage level. These converters have some prominent drawbacks like low voltage gain, high current ripple, unsmooth dc voltage and insufficient efficiency. This paper aims to propose an innovative high-gain multi-stage non-isolated step-up converter (HGNISUC) to triumph over these drawbacks. The proposed structure has been generally constructed using a high-voltage gain dc-dc converter and a classic rectifier which can provide high voltage gain based on dual-winding coupled-inductor (DWCI). Its cost is significantly reduced due to utilization of only one switch and one medium frequency transformer. Since the proposed structure has been operated in the PV system, an optimal interval type-2 fuzzy system based maximum power point tracking (OIT2FS-MPPT) has been designed to transfer the maximum power of solar-energy module to the load side. Due to the multi-objective nature of the control problem, multi-objective grey wolf optimizer (MOGWO) is used to optimally tune the controller parameters. Finally, the performance of the proposed converter has been validated under both MATLAB simulation and lab prototype tests.

A Hybrid Optimization Strategy for Minimizing Conversion Losses in Semi-Series-Resonant Dual-Active-Bridge Converter

To enhance the performance of resonant DC–DC converters, particularly under low-load conditions, a semi-series-resonant dual-active-bridge (Semi-SRDAB) converter with a hybrid optimization strategy is proposed. This strategy aims to reduce conduction-related losses and is designed for applications requiring a wide voltage range. The proposed Semi-SRDAB converter comprises a full-bridge inverter on the primary side and a hybrid-output bridge rectifier on the secondary side. It adopts phase-shift modulation combined with frequency modulation for power control. The hybrid optimization strategy for the Semi-SRDAB converter is investigated, beginning with the deduction of resonant current minimization using phasor analysis. Based on these analysis results, zero reactive power operation and soft-switching operation are achieved for both buck and boost modes. Successful validation has been demonstrated through experimental testing on a 300 W laboratory prototype. Enhanced conversion performance is confirmed by comparing the results with those from previous works.

Optimisation of plasma processes for decontamination of bacterial contaminants on polymeric food packaging materials

Abstract Foodborne diseases present a global health challenge, with over 420 000 deaths annually. Packaging plays a vital role in food safety but can introduce hazards if contaminated. Traditional decontamination methods are energy-intensive or leave toxic residues. Cold plasma technology offers promising solutions for generating antimicrobial reactive species. This study optimises a plasma system for packaging decontamination, achieving high inactivation rates for Staphylococcus epidermidis (gram-positive) and Acinetobacter baumannii (gram-negative), respectively 3.5 and 4.7. Statistical analysis guide process optimisation, highlighting factors enhancing biocidal action: treatment chamber size reduction, high duty cycle, and mist injection. The system proves effective against both kinds of bacteria, with gram-negative bacteria showing higher sensitivity. The study focuses on optimising an innovative process, emphasising the process towards industrialisation and highlighting economic and environmental benefits. This investigation’s innovative approach aims to bridge the gap between laboratory prototypes and industrial applications.

A Simple 18‐Pulse Uncontrolled Star Rectifier by Adopting Dual Passive Injection Circuits at DC Side

ABSTRACTThis research introduces a simple 18‐pulse star rectifier, which is a combination of a conventional double‐star rectifier and two new passive injection circuits. The proposed passive injection circuits are constituted with a specially tapped interphase transformer (STIPT) and four diodes. The proposed passive injection circuits can simultaneously increase the step number of the input line current and the pulse number of the load voltage. The first passive injection circuit (FPIC) doubles the pulse number of the traditional double‐star rectifier converting it into an asymmetrical 12‐pulse star rectifier while the second passive injection circuit (SPIC) further converts the 12‐pulse star rectifier into 18‐pulse star rectifier. For tripling the pulse number of the double‐star rectifier, the STIPT requires to be designed optimally. For designing purpose, the proper tap ratios of the STIPT are determined depending on the minimum total harmonic distortion (THD) of the input line current. When designed optimally, the proposed rectifier simultaneously reduces the THD of the input line current and ripple of the output voltage with increasing pulses. In order to provide experimental validation for the theoretical evaluation, a laboratory prototype is constructed. The theoretical THD of the input line current is about 10.1%, whereas the experimental THD is about 5.42%.