High Duty Ratio Research Articles

Optimal initial duty for improved MPPT under change in irradiances and partial shading conditions

Abstract Solar photovoltaic cells are widely used in renewable energy power generation. The efficient operation of these photovoltaic (PV) system is based on maximum power point tracking (MPPT). Various MPPT methods have been proposed to increase the output of a PV system. But confusion arises when choosing the optimal MPPT algorithm and its parameters such as perturbation time and initial duty. This paper examines the optimal initial duty and perturbation time to improve the performance of conventional MPPT techniques under uniform shading and partial shading. During the change in irradiances, at the initial irradiance the Modified P&O tracked MPPT faster because the modified P&O had less settling time during changes in irradiance for different initial duty ratios. During partial shading conditions, the TCT generates more power than the S and SP topologies and modified P&O tracked the MPPT in less time. However, at the high duty ratio, the P&O and INC gave similar results, which were better than the modified P&O. It was also observed that the initial duty ratio (Di) in the MPPT algorithm had a negligible effect on TCT configuration under partial shading conditions. These findings help in various applications for PV systems.

Response of variation of electrical control parameters to coatings prepared in organo-silicon electrolyte by plasma electrolytic oxidation

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 μm, 83.2 μm and 193.3 μm increased the surface hardness of 6061 aluminium alloy by 6–8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L−1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.

Effect of power supply parameters on discharge characteristics and sterilization efficiency of magnetically driven rotating gliding arc

Plasma sterilization is a new generation of high-tech sterilization method that is fast, safe, and pollution free. It is widely used in medical, food, and environmental protection fields. Home air sterilization is an emerging field of plasma application, which puts higher requirements on the miniaturization, operational stability, and operating cost of plasma device. In this study, a novel magnetically driven rotating gliding arc (MDRGA) discharge device was used to sterilize Lactobacillus fermentation. Compared with the traditional gas-driven gliding arc, this device has a simple structure and a more stable gliding arc. Simulation using COMSOL Multiphysics showed that adding permanent magnets can form a stable magnetic field, which is conducive to the formation of gliding arcs. Experiments on the discharge performance, ozone concentration, and sterilization effect were conducted using different power supply parameters. The results revealed that the MDRGA process can be divided into three stages: starting, gliding, and extinguishing. Appropriate voltage was the key factor for stable arc gliding, and both high and low voltages were not conducive to stable arc gliding and ozone production. In this experimental setup, the sterilization effect was the best at 6.6 kV. A high modulation duty ratio was beneficial for achieving stable arc gliding. However, when the duty ratio exceeded a certain value, the improvement in the sterilization effect was slow. Therefore, considering the sterilization effect and energy factors comprehensively, we chose 80% as the optimal modulation duty ratio for this experimental device.

Switch-2 determines Mg2+ADP-release kinetics and fine-tunes the duty ratio of Dictyostelium class-1 myosins.

Though myosins share a structurally conserved motor domain, single amino acid variations of active site elements, including the P-loop, switch-1 and switch-2, which act as nucleotide sensors, can substantially determine the kinetic signature of a myosin, i.e., to either perform fast movement or enable long-range transport and tension generation. Switch-2 essentially contributes to the ATP hydrolysis reaction and determines product release. With few exceptions, class-1 myosin harbor a tyrosine in the switch-2 consensus sequence DIYGFE, at a position where class-2 myosins and a selection of myosins from other classes have a substitution. Here, we addressed the role of the tyrosine in switch-2 of class-1 myosins as potential determinant of the duty ratio. We generated constitutively active motor domain constructs of two class-1 myosins from the social amoeba Dictyostelium discoideum, namely, Myo1E, a high duty ratio myosin and Myo1B, a low duty ratio myosin. In Myo1E we introduced mutation Y388F and in Myo1B mutation F387Y. The detailed functional characterization by steady-state and transient kinetic experiments, combined with in vitro motility and landing assays revealed an almost reciprocal relationship of a number of critical kinetic parameters and equilibrium constants between wild-type and mutants that dictate the lifetime of the strongly actin-attached states of myosin. The Y-to-F mutation increased the duty ratio of Moy1B by almost one order of magnitude, while the introduction of the phenylalanine in switch-2 of Myo1E transformed the myosin into a low duty ratio motor. These data together with structural considerations propose a role of switch-2 in fine-tuning ADP release through a mechanism, where the class-specific tyrosine together with surrounding residues contributes to the coordination of Mg2+ and ADP. Our results highlight the importance of conserved switch-2 residues in class-1 myosins for efficient chemo-mechanical coupling, revealing that switch-2 is important to adjust the duty ratio of the amoeboid class-1 myosins for performing movement, transport or gating functions.

Anti-interrupted-sampling repeater jamming method based on frequency agility waveform and sparse recovery

Interrupted-sampling repeater jamming (ISRJ) is a type of intra-pulse coherent jamming that poses a significant threat to radar detection and tracking of targets. This paper proposes an ISRJ suppression method based on frequency agile waveform and sparse recovery, starting from the temporal discontinuity and modulation characteristics of ISRJ. This method is particularly suitable for scenarios with high jamming duty ratio (JDR) and high jammer sampling duty ratio (SDR). By dividing the transmitted waveform into sub-pulses with different carrier frequencies and applying a two-round block sparse algorithm, the method accurately recovers three parameters of ISRJ, achieving effective jamming identification, reconstruction, and cancellation. Additionally, a target detection technique based on robust sparse recovery is proposed, significantly improving the stability and accuracy of target detection. Comparative experimental results conducted in three scenarios confirm the effectiveness and superiority of this method under high JDR and SDR conditions.

Interrupted‐sampling repeater jamming suppression based on block sparse recovery and random phase encoding

AbstractThe interrupted‐sampling repeater jamming (ISRJ) is an effective kind of intro‐pulse coherent jamming based on digital radio frequency memory. It appears as a group of false targets that are difficult to distinguish on the range profile after pulse compression, which seriously affects the target identification and tracking. According to the coherence between ISRJ and real target echo and the waveform discontinuity caused by intermittent interception, a new method is proposed for ISRJ parameter estimation and jamming suppression based on block sparse recovery. To ensure the effectiveness of sparse recovery, the transmitted signal is divided into several random phase‐encoded sub‐pulses. Firstly, the pulse‐number and time‐delay of the received echo are estimated by block orthogonal matching pursuit. Then, the jamming slices are identified based on the sampling duty ratio and the Doppler frequency is estimated through matching. Finally, according to the parameter estimation results, the jamming slices are reconstructed to eliminate ISRJ. Numerical experiments in two typical scenarios have shown that this method can effectively suppress ISRJ. Especially in the scenario of high jamming duty ratio, this method exhibits good anti‐jamming performance.

High power voltage multiplier (VM) PFC Converter with inherent ZCS Characteristics and high step-ip gain for enhanced low-line efficiency

In this paper, a Voltage Multiplier (VM) converter configuration has been designed for high Power PFC application, ensuring reduced losses and high system efficiency.The conventional PFC system is improved with adding VM circuit configuration that enhances the static gain features with moderate duty ratio (D), and hence, the reverse recovery (RR) issue is resolved. The VM section inherently adds two main specific features of clamping behavior and ZCS phenomenon to the PFC system. An experimental prototype of 2 kW, 600 V VM PFC converter configuration is designed and its effectiveness is validated under low line input of 100 V , operating at a high duty ratio, D = 0:67. The Real-Time Interface (RTI) feature of dSPACE1104 and MATLAB/Simulink are used to give the control signal for the verification of the system. Always, less than half of the output voltage (300 V ) appears across the switches of the converter, hence, voltage stress of the switch is minimized. Also, ZCS phenomenon is evident during switching commutations due to the snubber circuit behavior of the resonant tank, included in the proposed PFC converter. Hence, the overall system efficiency is improved. Furthermore, higher system efficiency is maintained for different rating which has been tested in this research work.

A High-Efficiency DC-DC Converter Based on Series/Parallel Switched Inductor Capacitors for Ultra-High Voltage Gains

A high-efficiency DC-DC converter employing a modified architecture called the hybrid switched inductor–capacitor series (MHSLCS) is proposed in this paper. The primary goal is to achieve a notably ultra-high voltage gain for renewable energy systems (RESs). Furthermore, the use of only one input capacitor in the MHSLCS eliminates pulsations in the input current at both low and high duty ratios. The proposed converter integrates the MHSLCS with a modified switched capacitor (MSC) that interleaves with the main MOSFET, effectively doubling the voltage transfer gain. Additionally, a modified hybrid switched inductor–capacitor parallel (MHSLCP) is incorporated in parallel with an interleaved auxiliary MOSFET. Both MOSFETs, combined with the MSC, contribute to achieving an ultra-high voltage gain. In addition, the inductors of the MHSLCP operate in a discontinuous conduction mode (DCM), which results in significant stress reductions in the power diodes and switches at high output voltages. The advantages of the proposed converter are multifaceted, demonstrating a high efficiency while minimizing the voltage in power device diodes and MOSFETs. The use of low inductance and capacitance values at high switching frequencies further enhances the performance. Wide-bandgap (WBG) power devices are employed to achieve the desired high voltage gain and efficiency. The proposed converter was designed with a PCB and underwent experimental testing to validate laboratory results. The proposed converter boosted the input voltage from 30 V to a variable output voltage between 325 V and 500 V, with a power output of 325 watts and an efficiency of 95.5%.

Characteristics of high-repetition-rate bipolar pulse DBD under various electrical conditions in atmospheric-pressure air

Numerous studies have been conducted on pulse dielectric barrier discharge (DBD) because it can produce powerful discharges uniformly at atmospheric pressure with a fast rise time. Although much research has been conducted on pulse DBD below 10 kHz, relatively little has been conducted on pulse DBD at high pulse repetition rates (PRRs). Therefore, in this study, the ozone generation and discharge characteristics of bipolar pulse DBD in atmospheric-pressure air at a high PRR of 10 kHz or above were investigated. According to the results of this study, with the exception of electron temperature, most discharge characteristics need for practical applications—like transfer charge, electron density, and discharge uniformity—improved as the voltage and duty ratio increased at high PRR. On the contrary, increasing the PRR exhibited trade-off features like low electron temperature, low discharge uniformity, and a high number of discharges per unit time. Ozone generation demonstrated good results at high voltage, appropriate PRR, and low duty ratio, but applying suitable electrical conditions is crucial considering ozone generation speed and power consumption. The findings of this study will be very beneficial for high-PRR pulse DBD applications that require quick and effective processing. Additionally, they will be useful for researching the characteristics of pulse DBD at high PRR.

Effects of Electrical Parameters on Micro-Arc Oxidation Coatings on Pure Titanium.

The micro-arc oxidation process was used to apply a ceramic oxide coating on a pure titanium substrate using calcium acetate and sodium dihydrogen phosphate as an electrolyte. The influence of the current frequency and duty ratio on the surface morphology, phase composition, wear behavior, and corrosion resistance were analyzed by employing a scanning electron microscope, X-ray diffractometer, ball-on-disk apparatus, and potentiodynamic polarization, respectively. Analyses of the surface and cross-sectional morphologies revealed that the MAO films prepared via a low current frequency (100 Hz) and a high duty ratio (60%) had a lower porosity and were more compact. The medium (500 Hz) and high (1000 Hz) frequencies at the higher duty ratios presented with better wear resistance. The highest film thickness (11.25 µm) was achieved at 100 Hz and a 20% duty ratio. A negligible current density was observed when the frequency was fixed at 500 Hz and 1000 Hz and the duty cycle was 20%.

Switched inductor super boost converter with auxiliary charging mode for low duty operation in a DC microgrid

For a number of applications including the power processing of low voltage renewable sources such as solar PV in grid connected systems, high gain voltage conversion is a basic requisite. A conventional boost converter will have diode recovery issues, increased current ripples, poor transient response, and low efficiency if it is being operated at high duty ratio beyond certain permissible limit. This paper discusses a new converter suitable for the mentioned application that uses three double-duty regulated switches, switched inductor–capacitor to deliver the required high voltage at a low duty cycle. This converter’s basic topology does not include complex circuitry such as transformers, coupled inductors, and cascaded/interleaved configurations. In addition, the proposed converter can operate in auxiliary charging mode, which improves the voltage gain and control flexibility while also expanding the duty ratio range. The converter in discussion has a high voltage gain, a low total voltage standing, a continuous input current, a wide range of duty ratios, and the ability to select the duty cycle as needed. The boundary conditions, as well as the CCM and DCM investigations of the proposed converter are explored. The experiment findings are used to validate the claims made in the theoretical analysis. A comparison with the available high gain DC–DC converters is made to justify the superior performance. A 200 W prototype of the converter is developed and tested in laboratory to validate its feasibility and behavior for the renewable based applications.

Quadratic Boost Converter with CLD Cell

A dc-dc converter is essential for Solar PV system to step up the low voltage from Solar panel/array to required voltage. In Solar PV system, the dc-dc converter will be buck-boost or boost converter. Many new boost converters are derived nowadays. In these, one of the modern converters is quadratic boost converter. Boost converters are required to operate with high duty ratio to achieve the higher output voltage. This high duty ratio limits the switching frequency because of high reverse recovery time, also it results poor efficiency and electromagnetic interference. In existing boost converters, the switches are suffered with high voltage stress.

Double Dual High Step-Up Power Converter with Reduced Stored Energy

This paper introduces a dual-switchhigh step-up DC-DC power converter. The proposed converter features a high step-up voltage gain, relatively low cumulative stored energy over its inductors, low voltage stress on the active switches, and high efficiency, even at a relatively high duty ratio. An assessment of the proposed converter against conventional boost and a high step-up power converter is presented in terms of steady-state time, voltage gain, stored energy over its inductors, and efficiency. The assessment shows a reduction of 81.25% and 62.5% of stored energy in inductors to comply with the same operational conditions. Simulation and experimental results are provided to validate the benefits of the proposed dual-switch high step-up power converter.

Elucidating the molecular determinants of force transmission in myosin ensembles using QCM-D.

Myosin II motors collectively produce force to facilitate muscle contraction via an ATP-mediated mechanochemical process, causing the motors to step along actin filaments. Such myosin II ensembles have been shown to display environment-based mechanosensitive abilities, where ensemble motor duty ratio can change in response to external signals, including force and local rigidity. However, at the single-molecule level, myosin II is non-processive; as such, it is becoming increasingly clear that myosin II motor ensembles do not behave as the sum of their single molecule properties. Interrogation of myosin motors within cytoskeletal filament networks in vitro is needed to understand how motors that crosslink multiple filaments know whether to be in a low duty ratio, non-processive mode as an individual molecule or in a high duty ratio, processive mode within ensembles. A quartz crystal microbalance with dissipation monitoring (QCM-D) is a powerful biophysical tool that can measure the kinetics and viscoelastic properties of protein complexes, films, and surface interactions. Here, we adapt in vitro cytoskeleton reconstitution assays to QCM-D experiments to investigate the assembly kinetics and viscoelastic properties of actomyosin bundles consisting of multiple myosin II motors acting between actin filaments. Actively monitoring the binding kinetics and stiffness of such bundles in real-time with the QCM-D as each element of the bundle assembles into the higher order actomyosin architecture will provide insight into the molecular-level drivers of mechanosensation and communication within the local cytoskeletal environment.

Mechanistic insights into the regulation of human myosin-7a.

Human myosin-7a (Myo7a) is an actin-based motor protein essential for vision and hearing. It plays critical roles in the development and functions of actin rich protrusions. Previous studies using Drosophila homolog showed that myosin-7a is a monomeric, high duty ratio motor and can move processively upon dimerization. However, characterization of full-length mammalian myosin-7a has been limited by the difficulty of expressing and purifying stable, intact protein. Here, we report the production of a complete human myosin-7a holoenzyme in insect cells and study its regulation by intra- and intermolecular mechanisms. We found that human myosin-7a utilizes regulatory light chain (RLC), calmodulin and calmodulin like protein 4 (CALML4) as the light chain subunits. CALML4 is recently discovered highly enriched in stereocilia and identified as a deafness candidate gene. We show that CALML4 does not bind to Ca2+ but plays a key role in regulating the dynamic binding of calmodulin to myosin-7a in response to Ca2+ signaling. The cochlea expresses two myosin-7a splicing isoforms differed by a short N-terminal extension. Using combined optical trapping, biochemistry, and in vitro motility assays, we show that the N-terminal extension greatly influences the enzymatic and mechanical behaviors of mammalian myosin-7a. We propose that the hair cell regulates its mechanosensitivity by adjusting the expression levels of the two myosin-7a isoforms. Finally, using single-molecule motility assays, we show that purified full-length myosin-7a alone does not move processively on actin in vitro, but in the presence of MyRIP, a known myosin-7a binding protein in neuroretina, it exhibits processive movements. Together, our results provide new molecular insight into how myosin-7a functions in hair cell stereocilia and neuroretina. The production of intact human myosin-7a protein enables future studies to understand the molecular details of human vision and hearing loss caused by myosin-7a defects.

Design and Control of High Voltage Gain Interleaved Boost Converter for Fuel Cell Based Electric Vehicle Applications

The need for power is raising rapidly all across the world right now. This last period has seen a dramatic increase in the severity of global warming brought on by the earth's climate. Greenhouse gas emissions from customary fossil fuel-depend vehicles have risen to the forefront of environmental concerns as the number of cars on the road continues to rise. Pollution from traditional internal combustion engines is rising at an alarming rate. A growing number of people see renewable energy based techniques as ideal answers to the problems of rising fuel efficiency regulations and falling pollution levels. In recent years, interest in hydrogen's potential as a new energy vector has grown rapidly; this is because hydrogen can be converted to electric energy in a fuel cell (FC), making it a viable option for powering fuel cell electric vehicles (FCEV). In comparison to other fuel cell types, the working temperature range of a Proton Exchange Membrane Fuel Cell (PEMFC) makes it the best option for usage in automobiles. As the value of FC modules is rather low, a further action is necessary for interfacing with utility grids in FC-based power sources. Even though a traditional boost converter may increase the DC bus voltage from the FC to the necessary level by the inverter, doing so at a very high duty ratio reduces the converter's efficiency and effectiveness. In this study, we propose using high-gain interleaved DC-DC converters to fix this issue. To provide the electric vehicle's power train, this research introduces a radial basis function network (RBFN) with maximum power point tracking (MPPT) method for PEMFC. To determine the PEMFC's optimum operating point, the planned NN-MPPT method employs a RBFN. FCEVS require dc-dc converters with more switching frequencies and heavy voltage gains for propulsion. A three-phase high voltage-gain interleaved boost converter (HV-GIBC) is also developed for the FCEV method to achieve high voltage-gain. Power semiconductors are stressed by leakage current fluctuation and voltage fluctuations are lessened by the interleaving method. We evaluate the MATLAB/Simulink platform's Fuzzy Logic controller against the RBFN-based MPPT controller in an FCEV system's performance evaluation.

Two-Switch Boost Converter With Improved Voltage Gain and Degree of Freedom of Control

The use of renewable resources for low power generation has led to extensive research on power converters for reliable and efficient power conversion. Though conventional boost converter (CBC) remains the widely used topology, its operating range is limited due to constraints on voltage gain and degree of freedom of control (DoFoC). This paper presents a two-switch boost converter (TSBC) which improves the voltage gain and DoFoC by cascading an additional switch-diode pair to the CBC circuit. The additional switch enhances the range of voltage gain without operating CBC at high duty ratios. Additionally, TSBC offers more choices to adjust voltage gain, which enhances DoFoC. The switching interval selection is detailed considering the voltage gain and constraints on circuit variables. The design formulations of TSBC are examined to facilitate optimal choice of components. The features of TSBC are theoretically established with mathematical derivations and are validated by simulations and experiments. The experimental results indicate that for a duty ratio of 0.7 for the existing switch of CBC, an increase in voltage gain from 3.2 to 4.3 is achieved when the duty ratio of the additional switch in TSBC is varied from 0 to 0.1. Similarly, improved DoFoC is demonstrated with inductor current control as well as with constant ripple ratios while maintaining the required output voltage. The proposed converter can easily replace the commonly CBC to improve the gain and DoFoC by simply cascading a switch-diode pair at the input-side of CBC.

Low-intensity pulsed ultrasound promotes proliferation and myelinating genes expression of Schwann cells through NRG1/ErbB signaling pathway

Schwann cells (SCs) are the major component of myelin sheath in the peripheral nervous system, which are necessary in the development, function maintenance, and repair of peripheral nerves. This study aimed to investigate the potential mechanism of low-intensity pulsed ultrasound (LIPUS) affecting the proliferation and myelinating activity of SCs. Rat Schwann cell line RSC96 were cultured and exposed to LIPUS of different duty ratios (control, 20 %, 50 %, 80 %). Results demonstrated that LIPUS with a duty ratio of 50 % showing the maximal effect in facilitating proliferation of SCs. The expressions of Krox20 and myelin basic protein (MBP), the key molecules of SC myelination, and the potent inducer of myelination neuregulin 1 (NRG1) and its receptors ErbB2 and ErbB3 increased significantly by LIPUS. The reaction of these factors to LIPUS were both time- and duty ratio-dependent: namely LIPUS with higher duty ratios took effects when applied repeatedly over more consecutive days. These observations indicated that NRG1/ErbB signaling pathway might contribute to the effects of LIPUS on the proliferation and myelinating status of SCs, which could be one of the mechanisms in the protective role of LIPUS in nerve repair and regeneration. Our work provided novel insights for promising strategies of nerve repair therapy.

Infrared stealth and the flexible metasurface of radar backscattering suppression

Based on the principle of electromagnetic wave cancellation, this paper proposes a coded metasurface which can suppress both radar backscattering and infrared radiation. Two high duty ratio superstructures with two different structures are designed and coded units are worked out on the basis of this. The experimental results indicate that the metasurface can effectively suppress the backscattering of electromagnetic waves in the 8.6–16.3 GHz band, and the average emissivity at infrared atmospheric window is 0.43. At the same time, it has good heat insulation performance, which can effectively suppress infrared radiation. In addition, the metasurface has light mass and flexibility. Therefore, the metasurface has a good prospect for application in the multispectral stealth field.

Myosin II Adjusts Motility Properties and Regulates Force Production Based on Motor Environment.

Myosin II has been investigated with optical trapping, but single motor-filament assay arrangements are not reflective of the complex cellular environment. To understand how myosin interactions propagate up in scale to accomplish system force generation, we devised a novel actomyosin ensemble optical trapping assay that reflects the hierarchy and compliancy of a physiological environment and is modular for interrogating force effectors. Hierarchical actomyosin bundles were formed in vitro. Fluorescent template and cargo actin filaments (AF) were assembled in a flow cell and bundled by myosin. Beads were added in the presence of ATP to bind the cargo AF and activate myosin force generation to be measured by optical tweezers. Three force profiles resulted across a range of myosin concentrations: high force with a ramp-plateau, moderate force with sawtooth movement, and baseline. The three force profiles, as well as high force output, were recovered even at low solution concentration, suggesting that myosins self-optimize within AFs. Individual myosin steps were detected in the ensemble traces, indicating motors are taking one step at a time while others remain engaged in order to sustain productive force generation. Motor communication and system compliancy are significant contributors to force output. Environmental conditions, motors taking individual steps to sustain force, the ability to backslip, and non-linear concentration dependence of force indicate that the actomyosin system contains a force-feedback mechanism that senses the local cytoskeletal environment and communicates to the individual motors whether to be in a high or low duty ratio mode. The online version contains supplementary material available at 10.1007/s12195-022-00731-1.