Current Source Research Articles

Current controllers for optimizing laser cooling on cold atom experiments.

The design of a single chip current source based on a common power operational amplifier is presented and demonstrated for the purpose of controlling applied magnetic fields using bias/shim electromagnets in cold atom experiments. The efficacy of the design is realized via application to red-detuned polarization-gradient cooling of 87Rb down to 3 μK. Furthermore, we demonstrate Raman spectroscopy using these devices to apply current and so generate a precise, accurate, and reproducible magnetic field. This work is intended as a short tutorial for new graduate students and postdocs of laser cooling and trapping.

Characterization of In-Field Critical Currents in REBCO Tapes Over Wide Temperature Range by Pulsed Current Source With Supercapacitor

Characterization of In-Field Critical Currents in REBCO Tapes Over Wide Temperature Range by Pulsed Current Source With Supercapacitor

Assembling and testing optoelectronic system to record and process signals from fiber-optic sensors

The given research presents assembling and testing optoelectronic system to record and process signals from fiber-optic sensors. The main optoelectronic systems to record and process the signals from fiber-optic sensors are light source controller and optical power detector. There was assembled controller diagram, which apart from light source includes current source for its adequate operation, as well as the systems necessary for stabilizing its working point. The scheme was modelled for specifying nominal and maximum operation criteria. Construction has been designed in the way, that light source controller includes structures of the current regulation and stabilization super luminescent diode (SLED) and temperature stabilization. Apart from that, there was assembled the microsystem of optical power detector additionally to the light detector, which includes the microsystems of intensification and filtration of the signal measured, processing analog data into digital form, microcontroller, used for preliminary data analysis. Data of optoelectronic systems diagram to record and process the signals from fiber-optic sensors has high response speed, low noise level and sufficient progress.

Analysis of a Resistive-Capacitive Shunted Josephson Junction with Topologically Nontrivial Barrier Coupledto a RLC Resonator

This paper presents the resistive-capacitive shunted Josephson junction (RCSJJ) with a topologically nontrivial barrier (TNB) coupled to a linear RLC resonator. The rate equations describing RCSJJ with TNB coupled to the linear RLC resonator are established via Kirchhoff’s current and voltage laws. The model exhibits four, two, or no equilibrium points depending on the external direct current (DC) source and the fractional parameter. The stability analysis of the equilibrium points with credit to the Routh-Hurwitz stability criterion reveals that the stability of equilibrium points depends on the DC source and the fractional parameter. Current-voltage characteristic reveals the presence of a birhythmicity zone which is sensitive to the fractional parameter m. As the fractional parameter increases, the coexistence of the resonant state is destroyed, which is followed simultaneously by the appearance of a new resonance state. Depending on initial conditions, birhythmic behaviour is characterized by the existence of a limit cycle. The projection of the phase space in the specific plane and the time evolution of charge is predicted in which the amplitude of attractors reported is sensitive to the parameter m. Lastly, with a defined fractional parameter, the amplitude of the branch locked to the resonator is greater than the unlocked branch.

Prospects for cordycepin biosynthesis in microbial cell factories

Cordycepin, an adenosine analog, exhibits diverse bioactivities and holds significant potential for applications in healthcare and agriculture. Fungi of the genus Cordyceps, such as Cordyceps militaris, can naturally produce cordycepin. Current sources of cordycepin primarily involve extraction from fruiting bodies or isolation from liquid fermentation using C. militaris, presenting challenges such as low production intensity, complex separation and purification systems, and high production costs, limiting industrial feasibility. Recent advancements have witnessed the utilization of various fungal chassis cells to successfully engineer heterologous biosynthetic platforms for cordycepin, such as Saccharomyces cerevisiae and unconventional yeasts, offering advantages of high yield, short fermentation cycles, and a broad substrate spectrum. This mini review summarizes the biosynthetic pathways of cordycepin and focused on the comparison of the characteristics, advantages, current performance and prospects for the microbial cell factories, analyzing potential targets for metabolic pathway modification and giving strategies in both genetic engineering and process engineering to enhance production intensity. The mini review particularly emphasizes the crucial role of chassis cell stress tolerance to the toxic product in determining cordycepin yield and highlights the urgent need for high-throughput screening methods for high-yield strains.

Refinement of Global Coronal and Interplanetary Magnetic Field Extrapolations Constrained by Remote-sensing and In Situ Observations at the Solar Minimum

Solar magnetic fields are closely related to various physical phenomena on the Sun, which can be extrapolated with different models from photospheric magnetograms. However, the open flux problem (OFP), the underestimation of the magnetic field derived from the extrapolated model, is still unsolved. To minimize the impact of the OFP, we propose three evaluation parameters to quantitatively evaluate magnetic field models and determine the optimal free parameters in the models by constraining the coronal magnetic fields and the interplanetary magnetic fields (IMFs) with real observations. Although the OFP still exists, we find that magnetic field lines traced from the coronal models effectively capture the intricate topological configurations observed in the corona, including streamers and plumes. The OFP is lessened by using the Helioseismic and Magnetic Imager synoptic map instead of the Global Oscillation Network Group daily synoptic maps, and the potential field source surface + potential field current sheet (PFSS+PFCS) model instead of the current sheet source surface (CSSS) model. For Carrington Rotation 2231 at the solar minimum, we suggest that the optimal parameters for the PFSS+PFCS model are R ss = 2.2–2.5 R ☉ and R scs = 10.5–14.0 R ☉, as well as for the CSSS model, are R cs = 2.0–2.4 R ☉, R ss = 11.0–14.7 R ☉, and a = 1.0 R ☉. Despite the IMFs at 1 au being consistent with the measurements by artificially increasing the polar magnetic fields, the IMFs near the Sun are still underestimated. The OFP might be advanced by improving the accuracy of both the weak magnetic fields and polar magnetic fields, especially considering magnetic activities arising from interplanetary physical processes.

Research on the Control and Modulation Scheme for a Novel Five-Switch Current Source Inverter

Different from the voltage source inverter (VSI), the current source inverter (CSI) can boost the voltage and eliminate the additional passive filter and dead time. However, the DC-side inductor current is not a real current source and is generated by a DC voltage supply and an inductor. Under different switching states, the DC-side inductor will be charged or discharged, which leads to the DC-side inductor current being discontinuous or increasing. To solve the control problem of the DC-side inductor current of the CSI, a novel single-phase CSI topology with five switching tubes for grid-connected applications is proposed. Firstly, the reference calculation method and the hysteresis loop control scheme for the DC-side inductor current are proposed, and the adjustable and constant DC-side inductor current are obtained. Since the PWM signals cannot be directly implemented to the switching tubes, the modulation strategy for the single-phase CSI is proposed in this paper. Then, an active damping method based on the feedback capacitor voltage is presented to suppress the resonance peak caused by the LC filter on the grid side. Finally, the math model of the AC-side structure is established, and the optimal proportional-resonant controller parameters’ design method is explored by the amplitude–frequency characteristic curves. The simulation and experiment are implemented for the proposed CSI topology. The results show that a high-quality power with a good control performance can be obtained with the proposed CSI topology.

Development of a logic regression-based approach for the discovery of host- and niche-informative biomarkers in Escherichia coli and their application for microbial source tracking.

Microbial source tracking leverages a wide range of approaches designed to trace the origins of fecal contamination in aquatic environments. Although source tracking methods are typically employed within the laboratory setting, computational techniques can be leveraged to advance microbial source tracking methodology. Herein, we present a logic regression-based supervised learning approach for the discovery of source-informative genetic markers within intergenic regions across the Escherichia coli genome that can be used for source tracking. With just single intergenic loci, logic regression was able to identify highly source-specific (i.e., exceeding 97.00%) biomarkers for a wide range of host and niche sources, with sensitivities reaching as high as 30.00%-50.00% for certain source categories, including pig, sheep, mouse, and wastewater, depending on the specific intergenic locus analyzed. Restricting the source range to reflect the most prominent zoonotic sources of E. coli transmission (i.e., bovine, chicken, human, and pig) allowed for the generation of informative biomarkers for all host categories, with specificities of at least 90.00% and sensitivities between 12.50% and 70.00%, using the sequence data from key intergenic regions, including emrKY-evgAS, ibsB-(mdtABCD-baeSR), ompC-rcsDB, and yedS-yedR, that appear to be involved in antibiotic resistance. Remarkably, we were able to use this approach to classify 48 out of 113 river water E. coli isolates collected in Northwestern Sweden as either beaver, human, or reindeer in origin with a high degree of consensus-thus highlighting the potential of logic regression modeling as a novel approach for augmenting current source tracking efforts.IMPORTANCEThe presence of microbial contaminants, particularly from fecal sources, within water poses a serious risk to public health. The health and economic burden of waterborne pathogens can be substantial-as such, the ability to detect and identify the sources of fecal contamination in environmental waters is crucial for the control of waterborne diseases. This can be accomplished through microbial source tracking, which involves the use of various laboratory techniques to trace the origins of microbial pollution in the environment. Building on current source tracking methodology, we describe a novel workflow that uses logic regression, a supervised machine learning method, to discover genetic markers in Escherichia coli, a common fecal indicator bacterium, that can be used for source tracking efforts. Importantly, our research provides an example of how the rise in prominence of machine learning algorithms can be applied to improve upon current microbial source tracking methodology.

EEG-Correlates of Competition and Cooperation

The aim was to investigate the peculiarities and localization of the current source density of α- and θ-frequency bands accompanying competition and cooperation with another player, as well as individual figure building in a computer game. The sample included forty-two volunteers (24 females) between the ages of 18 and 47. Analysis of differences in the current source density of 127 channel EEG under different game conditions was performed in the eLoreta program. During competition, the θ-current source density in the anterior cingulate cortex and medial prefrontal cortex was greater than during cooperation. According to the literature on functional correlates of θ-rhythm, it can be suggested that the greater increase in medial frontal θ-rhythm detected during competition may be related to focused attention and cognitive control processes. The alpha current source density in the parietal and visual cortex areas during interactive game modes (cooperation and competition) was lower compared to the individual mode. During cooperation the α-current source density was lower compared to the competition mode. The greatest decrease of the α-current source density in the cooperation mode is consistent with idea of a relation between α-rhythm decrease and the processes of understanding the other person’s intentions.

Temporal and spatial variation of morphological traits and genetic structure in Phengaris teleius myrmecophilous butterflies following habitat and climate changes three decades after reintroduction

A successful reintroduction of Phengaris teleius performed in the Netherlands by translocating 86 individuals from a Polish metapopulation in 1990 represents a unique opportunity to study changes in butterflies from a source and reintroduced metapopulation after such a common conservation practice. Using multilevel comparisons, we tested morphological and genetic changes that occurred after 30 generations since the reintroduction. We also assessed the climatic and connectivity changes that occurred over time in both metapopulation networks. Unexpectedly, we found more significant morphological changes in the current individuals from the source metapopulation, where both sexes had bigger hindwings with different shapes in comparison to the individuals from the original metapopulation in the year of the reintroduction and the ones from the current reintroduced metapopulation. The butterflies from the Dutch metapopulation also had smaller thorax width compared to the ones from the current source metapopulation. The observed morphological changes can be shaped by various factors like changes in climatic conditions and habitat connectivity. Additionally, the genetic analysis revealed a differentiation between the source and reintroduced metapopulation. We found a loss of half of the allelic richness and a bottleneck effect in the reintroduced metapopulation compared to the current Polish one. Our results show that Phengaris butterflies have the potential to adapt to new habitats and respond to climatic changes despite their complex life cycle. A proper long-term habitat management in reintroduced butterfly metapopulations and habitat restoration are key factors influencing the success of reintroduction.

A multifunctional inverter power quality coordinated optimization strategy based on comprehensive evaluation

The large-scale integration of renewable energy sources and power electronic devices has led to increasingly dispersed and networked characteristics of power quality disturbances in distribution systems. Traditional control devices, limited by their fixed-point control, no longer meet the development needs of modern distribution systems. Considering the distribution and structural characteristics of the current new-type sources and loads, a multifunctional inverter power quality coordinated control strategy based on comprehensive evaluation is proposed. This strategy aims to achieve power quality coordinated control by utilizing optimal compensation capacity while the grid-connected inverter provides active power output. Firstly, the traditional ipiq power quality detection method is analyzed and improved to enable detection of harmonics, reactive power, and three-phase imbalance currents in single-phase systems or three-phase four-wire systems. Secondly, in the power quality assessment, a balanced algorithm is employed to obtain the comprehensive evaluation index of power quality, thereby improving the deficiencies of single-weight evaluation. Next, to ensure the grid-connected inverter achieves optimal power quality coordinated control with minimal compensation capacity, an optimization compensation function is established between compensation capacity and comprehensive power quality index. This function is optimized using non-dominated sorting genetic algorithm to enhance equipment utilization and system economy. Finally, the feasibility and effectiveness of the proposed method are validated through simulations, demonstrating the achievement of optimal capacity configuration for power quality coordinated control while ensuring active power output by the grid-connected inverter.

Electrolytes for solid state lithium batteries in the [N13pip]ClO4-LiClO4-Al2O3 system for solid state lithium batteries

The transport, electrochemical, structural, and thermal properties of electrolytes in the ternary system [N13pip]ClO4-LiClO4-γ-Al2O3 (N13pip is N-methyl-N-ethyl-piperidinium cation) were investigated at the molar ratio [N13pip]ClO4:LiClO4 = 0.82:0.18. The addition of alumina leads to a change in the thermodynamic properties of the [N13pip]ClO4-LiClO4 system that can be explained by a partial transfer of lithium perchlorate from the organic phase to the surface of γ-Al2O3. The highest ionic conductivity of 6.2∙10–4 S/cm at 110 °C was observed for the composition containing the volume fraction (f) of γ-Al2O3 equal to 0.5. The increase in conductivity compared to the binary system 0.82[N13pip]ClO4-0.18LiClO4 is achieved due to the amorphization of the organic salt near the salt/LiClO4/oxide interfaces. Galvanostatic cycling with Li electrodes shows that composites with f = 0.5 are stable at 110 °C for at least 68 charge/discharge cycles, and the electrolyte is shown to be electrochemically stable up to 5 V. This system can be used as a solid-state electrolyte in lithium-ion current sources.

Breastfeeding – a survey of fathers’ support needs and preferred sources of information

BackgroundFathers can be a critical source of breastfeeding support for their partner, but little is known about what fathers would like to learn about breastfeeding. Partner’s support and encouragement enhances mother’s breastfeeding confidence and boost the capacity to address breastfeeding difficulties effectively. The aims of this study were to explore what fathers regard as important to learn around breastfeeding, and their current and preferred sources of information.MethodsA structured online survey was conducted, between September 2022 and November 2022, with fathers containing three sections: (1) sociodemographic variables; (2) perceived importance of 26 breastfeeding topics; and (3) sources of breastfeeding information. A convenience sample of expectant and current fathers aged 18 years or older, who were expecting a baby or had a child aged one year or younger, living in Australia, and able to complete survey in English was recruited. Participants were recruited on Facebook advertisement.ResultsA total of 174 fathers participated in the study, majority (75%) were aged 30–39 years, current dads (74%), and university educated (69%). The breastfeeding topics that fathers perceived as the most important/ important to learn about were how to work with their partner to overcome breastfeeding challenges, how fathers can be involved with their breastfed baby, the types of support fathers can provide to breastfeeding mothers, what to expect in the first week and the benefits of breastfeeding. The most preferred health professional sources of breastfeeding information were midwives, child and family nurses and doctors. Among non-health professional sources of support, mobile app, friends and family were most popular.ConclusionBreastfeeding information to enhance fathers’ knowledge and awareness of common breastfeeding challenges, and fathers’ role in supporting their breastfeeding partner, appear to be (most) important for fathers. Mobile app appears to be among the most preferred non-health professional ways to provide breastfeeding information to fathers.

Big Data Technology Usage in Electric Transportation Industry

In the context of critical challenges related to global warming and the necessity of reducing carbon footprint, the electric car sector is experiencing significant growth. This progress inevitably leads to the need for expansion and modernization of the charging station infrastructure. This article conducts a detailed analysis of how big data processing technologies can contribute to the optimization of this infrastructure’s use, the efficiency of charging stations, and the development of personalized services for electric vehicle users. Strategies for solving current problems, particularly in the areas of data security and standardization, are discussed, along with the impact of big data on the formation of new commercial models in the electric transport sector. Special attention is given to the analysis of existing scientific works and publications, which reveal a noticeable deficit of research focused on adapting big data technologies to specific regional conditions and analyzing the behavioral models of electric vehicle consumers. The article identifies key directions for future research aimed at exploring the potential of big data for the intelligent optimization of electric vehicle transport, particularly in areas such as demand forecasting, effective management of charging stations, development of new user services, and integration with broader urban transport management systems. Additionally, the article highlights challenges related to ensuring the confidentiality and security of collected data, the need to integrate diverse data and systems, and the current demand for qualified professionals in the field of big data analysis. The final section of the article focuses on the prospects of using big data in electric transport, their potential contribution to the development of smart city concepts, infrastructure improvement, and enhancing the quality of services for end consumers. Recommendations are provided for key stakeholders in the industry, with the aim of facilitating the adoption of strategic decisions that would take into account future opportunities and challenges. An analytical review of current literature sources and online publications is included, emphasizing the innovative nature of the research conducted.

Adsorption and storage of hydrogen- A computational model approach

Due to the imperative global energy transition crisis, hydrogen storage and adsorption technologies are becoming popular with the growing hydrogen economy. Recently, complex hydrides have been one of the most reliable materials for storing and transporting hydrogen gas to various fuel cells to generate clean energy with zero carbon emissions. With the ever-increasing carbon emissions, it is necessary to substitute the current energy sources with green hydrogen-based efficient energy-integrated systems. Herein, we propose an input-output model that comprehends complex hydrides such as lithium and magnesium alanates, amides and borohydrides to predict, estimate, and directly analyse hydrogen storage and adsorption. A critical and thorough comparative analysis of the respective complex hydrides for hydrogen adsorption and storage is discussed, elucidating the storage applications in water bodies. Several industrial scale-up processes, economic analysis, and plant design of hydrogen storage and adsorption approaches are suggested through volumetric and gravimetric calculations.

Original Empirical Research Protective Effects of Succinic Acid upon Exposure to the Low-Frequency Alternating Magnetic Field Determined in the Experiment

Introduction. The need to simulate the oxidative stress by an experiment of exposure to the low-frequency alternating magnetic field is induced by the persistent increase of the electromagnetic load on the endothermic organisms caused by the annual deterioration of the electromagnetic state of the environment. The low-frequency alternating magnetic field starts a chain of biochemical reactions in the laboratory animals, which alter the homeostasis against the increased intensity of free-radical oxidation (peroxidation) of biomembrane lipids. The preparations containing succinic acid have the antioxidant, antihypoxant, actoprotective and stress-protective effects, tested through various kind of modelling, however, the absence of data on the efficacy of succinic acid under the exposure to the alternating magnetic field has become the reason for the present experiment. The aim of the research is to determine the protective effects of succinic acid upon exposure of the laboratory rats to the low-frequency alternating magnetic field.Materials and Methods. The objects of the research were 90 white outbred male rats weighing 200–250 g, divided into three groups: group 1 — intact, the animals were in standard vivarium conditions and were not exposed to any effect; group 2 — control, the rats were exposed to the low frequency alternating magnetic field (LF-AMF) for 21 days daily per 3 hours, preceded by daily intraperitoneal administration to animals of the 0.9% sodium chloride solution at a dose of 1 ml / kg straight before them being exposed to LF-AMF; group 3 — experimental, the rats were daily intraperitoneally administered the succinic acid at a dose of 100 mg / kg (1 ml / kg) for 21 days prior to being exposed to LF-AMF. The exposure to the low-frequency alternating magnetic field was created by the Helmholtz coils (of diameter 1 m) powered by the alternating current source with a frequency of 50 Hz, with a magnetic field induction of 0.4 mT, whereas the cages with animals were placed in the centre of the device. The actoprotective effect of succinic acid was checked on the 7th, 14th and 21st days from the beginning of the experiment by duration of swimming of rats in water. The antioxidant effect — by concentration of diene conjugates, lipid hydroperoxides, malondialdehyde, ceruloplasmin, vitamin E in the blood plasma of rats measured according to the commonly accepted methods. The stress-protective effect was determined by the masses of the adrenal glands, thymus gland, spleen and the number of erosive defects on the suRussian Federationace of the gastric mucosa.Results. The experimental data has confirmed the actoprotective effect of succinic acid — the duration of swimming of the rats in the experimental group increased by 25–37% compared to the control one. The antioxidant effect of succinic acid under magnetic induction has been manifested in a decreased concentration of lipid peroxidation products against increased level of ceruloplasmin in the blood of rats in the experimental group compared to the animals in the control group. Administration of the succinic acid into the peritoneum of rats in the experimental group under exposure to the low frequency alternating magnetic field has prevented involution of the thymus gland by 45% (7th day), 56% (14th day), 71% (21th day) and the spleen by 52%, 58% and 66% respectively, alongside, the number of erosive and ulcerative defects on the suRussian Federationace of the gastric mucosa has decreased by 2.5–4 times compared to the animals in the control group.Discussion and Conclusion. The protective effects of succinic acid upon exposure to the low-frequency alternating magnetic field have been confirmed that include the stress-protective, actoprotective and antioxidant effects of the exogenous succinate. The ability of succinic acid to prevent the negative changes in the internal organs caused by the magnetic loads is proved by the statistically significant excess of the mass coefficients of the thymus gland and spleen in the experimental group, compared to the control one, along with the fewer erosive defects on the suRussian Federationace of the gastric mucosa. Succinic acid reduces the intensity of lipid peroxidation processes upon the magnetic exposure due to reducing the concentration of lipid peroxidation products and increasing the level of ceruloplasmin in the blood of animals.

A 3 MHz Low-Error Adaptive Howland Current Source for High-Frequency Bioimpedance Applications.

Bioimpedance is a diagnostic sensing method used in medical applications, ranging from body composition assessment to detecting skin cancer. Commonly, discrete-component (and at times integrated) circuit variants of the Howland Current Source (HCS) topology are employed for injection of an AC current. Ideally, its amplitude should remain within 1% of its nominal value across a frequency range, and that nominal value should be programmable. However, the method's applicability and accuracy are hindered due to the current amplitude diminishing at frequencies above 100 kHz, with very few designs accomplishing 1 MHz, and only at a single nominal amplitude. This paper presents the design and implementation of an adaptive current source for bioimpedance applications employing automatic gain control (AGC). The "Adaptive Howland Current Source" (AHCS) was experimentally tested, and the results indicate that the design can achieve less than 1% amplitude error for both 1 mA and 100 µA currents for bandwidths up to 3 MHz. Simulations also indicate that the system can be designed to achieve up to 19% noise reduction relative to the most common HCS design. AHCS addresses the need for high bandwidth AC current sources in bioimpedance spectroscopy, offering automatic output current compensation without constant recalibration. The novel structure of AHCS proves crucial in applications requiring higher β-dispersion frequencies exceeding 1 MHz, where greater penetration depths and better cell status assessment can be achieved, e.g., in the detection of skin or breast cancer.

Масоперенос у пористих електродах свинцево-кислотного акумулятора при розряді

At present, the study of diffusion-controlled processes with volume and heterogeneous chemical reactions plays an important role in various systems, in particular engineering ones, which include electric current sources. Based on familiar equations, this work considers ion exchange processes in the porous spaces of the electrodes of a lead-acid battery during its discharge. Allowance is made for electrochemical processes between the solid electrodes and the electrolyte that fills the porous space. As distinct from the majority of works, allowance is also made for the two-dimensionality of the process, which is due to the geometry of the apparatus and its physical characteristics. An important feature of the work is that in the open zone between the electrodes, the mass transfer is assumed to be convective, whose intensity is much higher than that of the diffusive one in the pores of the electrodes. This allows one to ignore, at least as a first approximation, the resistance of the central zone of the electric cell in the process of ion transfer. This, as one might say, limiting scheme, greatly simplifies the problem of charge transfer through the central zone of the electrochemical cell. It is shown that the electrical conductivity of the solid part of the electrodes plays an important role in the distribution of potentials both in the electrodes themselves and in the porous space. Due to the high electrical conductivity, the negative electrode relative to the positive one operates practically in a one-dimensional mode. It should also be noted that the additional resistance of the separator has a noticeable effect on the operation of the positive electrode, which manifests itself at relatively high currents, when the lack of the charging component becomes noticeable. Another important aspect of the calculation is the determination of the distribution of poorly soluble and poorly conductive lead sulfate (PbSO4), which affects the mass transfer process to a large extent, up to the termination of the discharge. It is shown that at relatively high currents, the formation of the passivating product is concentrated on the outer sides of the electrodes.

Inertia–Active Power Filter Design Based on Repetitive Control

The advent of distributed generation has brought with it a plethora of challenges for the nascent power systems that are being deployed on a large scale. Firstly, the majority of power electronic converters connected to the grid are in current source mode, which results in a lack of inertia and an inability to provide effective inertia or achieve damping support during fluctuations in grid frequency. Secondly, the issue of power quality, caused by the presence of harmonics, is becoming increasingly severe. This is particularly problematic in microgrids or systems with high line impedance, where harmonics can be amplified, thereby further compromising the stability of the power system. To address the deficiency in system inertia, numerous scholars are currently utilizing grid-forming (GFM) technology to achieve virtual inertia. In order to address the issue of system harmonics, it is possible to install active power filter (APF) devices at the point of common coupling (PCC), which serve to mitigate the effects of harmonics. This paper puts forth a proposal for the implementation of an APF with virtual inertia, based on PR + RC composite control. This composite control mechanism serves to enhance the harmonic suppression capabilities of the APF. The introduction of a frequency droop enables the capacitor voltage amplitude to be adjusted during fluctuations in system frequency, thereby achieving virtual inertia and providing active support for system frequency. The experimental results demonstrate that this strategy not only reduces the total harmonic distortion (THD) by 13% in comparison to PI control, indicating excellent harmonic suppression performance, but also allows the system to be inert, achieving positive results in suppressing frequency fluctuations during transients.

Urea Biosensing through Integration of Urease to the PEDOT-Polyamine Conducting Channels of Organic Electrochemical Transistors: pH-Change-Based Mechanism and Urine Sensing

We present the construction of an organic electrochemical transistor (OECT) based on poly(3,4-ethylendioxythiophene, PEDOT) and polyallylamine (PAH) and its evaluation as a bioelectronic platform for urease integration and urea sensing. The OECT channel was fabricated in a one-step procedure using chemical polymerization. Then, urease was immobilized on the surface by electrostatic interaction of the negatively charged enzyme at neutral pH with the positively charged surface of PEDOH-PAH channels. The real-time monitoring of the urease adsorption process was achieved by registering the changes on the drain–source current of the OECT upon continuous scan of the gate potential during enzyme deposition with high sensitivity. On the other hand, integrating urease enabled urea sensing through the transistor response changes resulting from local pH variation as a consequence of enzymatic catalysis. The response of direct enzyme adsorption is compared with layer-by-layer integration using polyethylenimine. Integrating a polyelectrolyte over the adsorbed enzyme resulted in a more stable response, allowing for the sensing of urine even from diluted urine samples. These results demonstrate the potential of integrating enzymes into the active channels of OECTs for the development of biosensors based on local pH changes.