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1
Madsen, Ole Secher, Arlendenovega Satria Negara, Kian Yew Lim, and Hin Fatt Cheong. "NEAR-BOTTOM FLOW CHARACTERISTICS OF CURRENTS AT ARBITRARY ANGLE TO 2D RIPPLES." Coastal Engineering Proceedings 1, no. 32 (February 2, 2011): 36. http://dx.doi.org/10.9753/icce.v32.currents.36.
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Experimental results for near-bottom current velocity profiles for flows over artificial, definitely 2D ripples made of 1.5 cm high aluminum angle-profile spaced at 10 cm intervals are obtained for the following cases: (i) current alone perpendicular to ripples; (ii) current alone parallel to ripples; (iii) combined orthogonal wave-current flows for current parallel to ripples; and (iv) current alone at an angle of 30° to the ripple axis. The velocity profiles are analyzed by the log-profile method, and show the roughness experienced by the current to increase as the angle between ripple and current direction increases, i.e. demonstrating convincingly the reality of the concept of a direction-dependent roughness for flows over a 2D rippled bottom. Roughness experienced by the velocity component perpendicular to the ripples is, however, found to be independent of the direction of the mainstream flow relative to that of the ripples, and the different roughness experienced by the perpendicular and parallel velocity components gives rise to a turning of the current velocity vector to become increasingly aligned with the ripple crests as the bottom is approached from above. Implications of this feature, in terms of net sediment transport direction in combined wave-current flows in inner-shelf coastal waters, is discussed.
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Cheng, Zhen, and Peter Traykovski. "NUMERICAL INVESTIGATIONS OF THE MECHANISMS ASSOCIATED WITH THE ONSHORE RIPPLE MIGRATION." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 28. http://dx.doi.org/10.9753/icce.v36.sediment.28.
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Quantification of cross-shore sediment transport is one of most intriguing challenges in shoreline and coastal geomorphology. During the past decades, several key mechanisms associated with onshore/offshore sediment transport have been identified, such as wave skewness/asymmetry, progressive wave streaming and undertow current. However, applying these mechanisms to the migration of wave formed bedforms (ripples) is not straightforward. For example, recent field observations off Fire Island, NY showed that ripples migrated onshore even during periods of offshore directed wave skewness, which is contradictory to the prediction of empirical sediment transport formulations. The physical processes driving ripple vortex formation, ejection and boundary layer streaming associated with rippled bed can further complicate the bedload/suspended load sediment transport over ripples. To fully understand these mechanisms, a comprehensive model that can resolve the ripple dynamics and interactions between free surface wave and rippled bed is examined.
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Goldammer, Erik, Marius Gentejohann, Michael Schlüter, Daniel Weber, Wolfgang Wondrak, Sibylle Dieckerhoff, Clemens Gühmann, and Julia Kowal. "The Impact of an Overlaid Ripple Current on Battery Aging: The Development of the SiCWell Dataset." Batteries 8, no. 2 (January 31, 2022): 11. http://dx.doi.org/10.3390/batteries8020011.
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Fast-switching semiconductors induce ripple currents on the high-voltage DC bus in the electric vehicle (EV). This paper describes the methods used in the project SiCWell and a new approach to investigate the influence of these overlaid ripples on the battery in EVs. The ripple current generated by the main inverter is demonstrated with a measurement obtained from an electric vehicle. A simulation model is presented which is based on an artificial reference DC bus, according to ISO 21498-2, and uses driving cycles in order to obtain current profiles relevant for battery cycling. A prototype of a battery cycling tester capable of high frequency and precise ripple current generation was developed and is used to cycle cells with superimposed ripple currents within an aging study. To investigate the impact of the frequency and the amplitude of the currents on the battery’s lifetime, these ripple parameters are varied between different test series. Cell parameters such as impedance and capacity are regularly characterized and the aging of the cells is compared to standard DC cycled reference cells. The aging study includes a total of 60 automotive-sized pouch cells. The evaluation of ripple currents and their impact on the battery can improve the state-of-health diagnosis and remaining-useful life prognosis. For the development and validation of such methods, the cycled cells are monitored with a measurement system that regularly measures current and voltage with a sampling rate of 2 MHz. The resulting dataset is suitable for the design of future ripple current aging studies as well as for the development and validation of aging models and methods for battery diagnosis.
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Kim, Hae-In, Su-Hwan Kim, Seung-Woo Baek, Hag-Wone Kim, Kwan-Yuhl Cho, and Gil-Dong Kim. "Comparison of Interleaving Methods of Parallel Connected Three-Level Bi-Directional Converters." Energies 15, no. 1 (December 21, 2021): 6. http://dx.doi.org/10.3390/en15010006.
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The voltage and current ripples in the three-level bi-directional converter (TLBC) can be reduced by an interleaving technique that controls a phase difference between the modules of power converter. On the other hand, the inductor current ripple in TLBC is increased due to the circulating current between the modules. In this paper, the effects of two interleaving methods on a two-phase TLBC, Z-type and N-type, are investigated and compared. In particular, capacitor current ripple, and voltage ripple are compared by two interleaving methods verified through Powersim (PSIM) simulation.
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Karthikeyan, V., Venkatesan Jamuna, and D. Rajalakshmi. "Interleaved Boost Converter for Photovoltaic Energy Generation." Applied Mechanics and Materials 622 (August 2014): 97–103. http://dx.doi.org/10.4028/www.scientific.net/amm.622.97.
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Renewable energy is derived from natural resources and most commonly used renewable energy system is photovoltaic cells. DC-DC boost converter serves many purposes and usually required in many applications which has a low output voltage such as batteries, photo-voltaic cell. In this paper interleaved boost converter (IBC) topology is discussed for solar energy generation. IBC have better performance characteristics compared to a conventional boost converter due to increased efficiency. DC-DC IBC have been considered and analyzed by input current ripple and output current ripple and output voltage ripple. The waveforms of voltage and current ripples and the output voltage are obtained by using MATLAB/SIMULINK are presented. The design of inductor, capacitor and analysis of ripples has been presented.
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Wang, Haifeng, and Haili Zhang. "An Adaptive Control Strategy for a Low-Ripple Boost Converter in BLDC Motor Speed Control." Power Electronics and Drives 6, no. 1 (January 1, 2021): 242–59. http://dx.doi.org/10.2478/pead-2021-0019.
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Abstract Conventional boost converters are widely used for connecting low-voltage power sources and inverters in motor control. However, a large filter capacitor bank is often used to reduce DC-link ripples that occur when an inverter is connected to a boost converter. Otherwise, significant voltage and current perturbations can impact on battery performance degradation and cause torque ripple, speed ripple and vibration in brushless DC (BLDC) motors. To suppress the converter’s DC-link ripple, this paper proposes a new control strategy for boost converter controller to generate low-ripple DC-link voltage or current at different motor speeds. In the proposed method, observers are designed to adaptively estimate the DC-link voltage and current harmonics. The harmonic terms are used as feedback signals to calculate the DC converter’s duty cycle. The entire control model is implemented on an embedded system, and its robustness is verified by simulation and experimental results that show the DC-link voltage and current ripples can be reduced by about 50% and 30%, respectively.
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Chaturvedi, Shivam, Mengqi Wang, Yaoyu Fan, Deepak Fulwani, Guilherme Vieira Hollweg, Shahid Aziz Khan, and Wencong Su. "Control Methodologies to Mitigate and Regulate Second-Order Ripples in DC–AC Conversions and Microgrids: A Brief Review." Energies 16, no. 2 (January 10, 2023): 817. http://dx.doi.org/10.3390/en16020817.
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Second-order ripples occur in the voltage and current during any DC–AC power conversion. These conversions occur in the voltage source inverters (VSIs), current source inverters (CSIs), and various single-stage inverters (SSIs) topologies. The second-order ripples lead to oscillating source node currents and DC bus voltages when there is an interconnection between the AC and DC microgrids or when an AC load is connected to the DC bus of the microgrid. Second-order ripples have various detrimental effects on the sources and the battery storage. In the storage battery, they lead to the depletion of electrodes. They also lead to stress in the converter or inverter components. This may lead to the failure of a component and hence affect the reliability of the system. Furthermore, the second-order ripple currents (SRCs) lead to ripple torque in wind turbines and lead to mechanical stress. SRCs cause a rise in the temperature of photovoltaic panels. An increase in the temperature of PV panels leads to a reduction in the power generated. Furthermore, the second-order voltage and current oscillations lead to a varying maximum power point in PV panels. Hence, the maximum power may not be extracted from it. To mitigate SRCs, oversizing of the components is needed. To improve the lifespan of the sources, storage, and converter components, the SRCs must be mitigated or kept within the desired limits. In the literature, different methodologies have been proposed to mitigate and regulate these second-order ripple components. This manuscript presents a comprehensive review of different effects of second-order ripples on different sources and the methodologies adopted to mitigate the ripples. Different active power decoupling methodologies, virtual impedance-based methodologies, pulse width modulation-based signal injection methodologies, and control methods adopted in distributed power generation methods for DC microgrids have been presented. The application of ripple control methods spans from single converters such as SSIs and VSIs to a network of interconnected converters. Furthermore, different challenges in the field of virtual impedance control and ripple mitigation in distributed power generation environments are discussed. This paper brings a review regarding control methodologies to mitigate and regulate second-order ripples in DC–AC conversions and microgrids.
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Cheng, Chiu H., Jaco C. de Smit, Greg S. Fivash, Suzanne J. M. H. Hulscher, Bas W. Borsje, and Karline Soetaert. "Sediment shell-content diminishes current-driven sand ripple development and migration." Earth Surface Dynamics 9, no. 5 (October 7, 2021): 1335–46. http://dx.doi.org/10.5194/esurf-9-1335-2021.
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Abstract. Shells and shell fragments are biogenic structures that are widespread throughout natural sandy shelf seas and whose presence can affect the bed roughness and erodibility of the seabed. An important and direct consequence is the effect on the formation and movement of small bedforms such as sand ripples. We experimentally measured ripple formation and the migration of a mixture of natural sand with increasing volumes of shell material in a racetrack flume. Our experiments reveal the impacts of shells on ripple development in sandy sediment, providing information that was previously lacking. Shells expedite the onset of sediment transport while simultaneously reducing ripple dimensions and slowing down their migration rates. Moreover, increasing shell content enhances near-bed flow velocity due to the reduction of bed friction that is partly caused by a decrease in average ripple size and occurrence. This, in essence, limits the rate and magnitude of bed load transport. Given the large influence of shell content on sediment dynamics as well as the high shell concentrations found naturally in the sediments of shallow seas, a significant control from shells on the morphodynamics of sandy marine habitats is expected.
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Mangum, James M., Ferdinand Harerimana, Millicent N. Gikunda, and Paul M. Thibado. "Mechanisms of Spontaneous Curvature Inversion in Compressed Graphene Ripples for Energy Harvesting Applications via Molecular Dynamics Simulations." Membranes 11, no. 7 (July 9, 2021): 516. http://dx.doi.org/10.3390/membranes11070516.
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Electrically conductive, highly flexible graphene membranes hold great promise for harvesting energy from ambient vibrations. For this study, we built numerous three-dimensional graphene ripples, with each featuring a different amount of compression, and performed molecular dynamics simulations at elevated temperatures. These ripples have a convex cosine shape, then spontaneously invert their curvature to concave. The average time between inversion events increases with compression. We use this to determine how the energy barrier height depends on strain. A typical convex-to-concave curvature inversion process begins when the ripple’s maximum shifts sideways from the normal central position toward the fixed outer edge. The ripple’s maximum does not simply move downward toward its concave position. When the ripple’s maximum moves toward the outer edge, the opposite side of the ripple is pulled inward and downward, and it passes through the fixed outer edge first. The ripple’s maximum then quickly flips to the opposite side via snap-through buckling. This trajectory, along with local bond flexing, significantly lowers the energy barrier for inversion. The large-scale coherent movement of ripple atoms during curvature inversion is unique to two-dimensional materials. We demonstrate how this motion can induce an electrical current in a nearby circuit.
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Viatkin, Aleksandr, Riccardo Mandrioli, Manel Hammami, Mattia Ricco, and Gabriele Grandi. "AC Current Ripple in Three-Phase Four-Leg PWM Converters with Neutral Line Inductor." Energies 14, no. 5 (March 5, 2021): 1430. http://dx.doi.org/10.3390/en14051430.
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This paper presents a comprehensive study of peak-to-peak and root-mean-square (RMS) values of AC current ripples with balanced and unbalanced fundamental currents in a generic case of three-phase four-leg converters with uncoupled AC interface inductors present in all three phases and in neutral. The AC current ripple characteristics were determined for both phase and neutral currents, considering the sinusoidal pulse-width modulation (SPWM) method. The derived expressions are simple, effective, and ready for accurate AC current ripple calculations in three- or four-leg converters. This is particularly handy in the converter design process, since there is no need for heavy numerical simulations to determine an optimal set of design parameters, such as switching frequency and line inductances, based on the grid code or load restrictions in terms of AC current ripple. Particular attention has been paid to the performance comparison between the conventional three-phase three-leg converter and its four-leg counterpart, with distinct line inductance values in the neutral wire. In addition to that, a design example was performed to demonstrate the power of the derived equations. Numerical simulations and extensive experimental tests were thoroughly verified the analytical developments.
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Priambodo, Purnomo Sidi, Yosua Adriadi, and Taufiq Alif Kurniawan. "Transformerless SoC-based current control switching battery charger for e-vehicle: design and analysis." E3S Web of Conferences 67 (2018): 03044. http://dx.doi.org/10.1051/e3sconf/20186703044.
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Electric-based vehicles become a necessity in the future to dramatically reduce the effects of pollution. There are various devices involve in the operation of electric vehicles, one of which is a battery charger. This paper discusses the design steps, circuit and ripple performance analysis associated with building a battery charger system. The analysis shows the differences between RL and RC circuits in controlling the output voltage average and the ripples. It shows how RLC mixed circuit improve performance in both controlling the output voltage average and the ripple suppression.
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Kularatne, S. R., J. Doucette, and C. B. Pattiaratchi. "The effect of ripple types on cross-shore suspended sediment flux." Earth Surface Dynamics Discussions 2, no. 1 (April 7, 2014): 215–54. http://dx.doi.org/10.5194/esurfd-2-215-2014.
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Abstract. Field measurements, collected at several low energy, microtidal beaches in south-western Australia were used to study the cross-shore transport and sediment resuspension over different sand ripple types. The measurements included simultaneous records of the water surface elevation, cross-shore current velocity, and suspended sediment concentration, as well as free diver measurements of the ripple dimensions. The observed ripples were classified according to their geometry and sediment suspension patterns into six categories: flat bed, post-vortex ripples, two-dimensional (2-D) ripples, two/three-dimensional (2-D/3-D) ripples, three-dimensional (3-D) ripples, and cross ripples. Flat bed conditions were observed under the highest flow mobility numbers. Post-vortex ripples were observed under slightly lower mobility numbers. The other ripple types occurred under low mobility numbers, with no significant difference in the mobility number among them. Two-dimensional ripples were observed more than the other ripple types in the presence of coarse grains. The suspended sediment concentration at ∼0.05 m above the bed was greater over steep ripples. The net cross-shore suspended sediment flux close to the seabed (at ∼0.05 m) in the swell frequency band varied over the different ripples types: onshore over a flat bed, offshore over post-vortex ripples, onshore over 2-D and 2-D/3-D ripples, and offshore over 3-D ripples. The suspended sediment flux direction over the cross ripples varied between onshore and offshore.
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Akay, Ali, and Paul Lefley. "Torque Ripple Reduction Method in a Multiphase PM Machine for No-Fault and Open-Circuit Fault-Tolerant Conditions." Energies 14, no. 9 (May 2, 2021): 2615. http://dx.doi.org/10.3390/en14092615.
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This paper presents a method that has been developed to reduce the torque ripples under healthy and open-circuit fault-tolerant (OCFT) conditions for a multiphase permanent magnet (PM) machine. For smooth torque, both the phase current and the back electromotive force (back-EMF) should be purely sinusoidal. To improve the torque in a multiphase machine, higher-order current harmonics are injected, which are related to the harmonics in the back-EMF. For this reason, generally, multiphase machines are designed with higher-order back-EMF harmonics. However, these harmonics produce ripples in the torque. In light of this, a torque ripple cancellation method has been developed that first determines an additional current component from the harmonic content of the back-EMF and then injects these additional components to cancel the torque ripple. It has been found that this new torque ripple cancellation method works for both faultless and faulty conditions in a five-phase PM machine. The method has been validated using Finite Element Analysis, and the results are presented in this paper.
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Wang, Zhiqiang, Yan Niu, Xiayu Yan, and Xin Gu. "Low-Carrier-Ratio Modulation Strategy Based on Improved Flux Ripple Model." Energies 15, no. 6 (March 16, 2022): 2173. http://dx.doi.org/10.3390/en15062173.
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Since the quality of the direct and quadrature axis current (dq-axis) is an important performance indicator of a motor, the technique of flux ripple analysis is necessary to determine the appropriate working conditions for various voltage sequences and reduce current fluctuations. However, the traditional flux ripple model cannot analyze dq-axis flux ripples (except under no-load conditions). Therefore, it is unable to calculate the modulation ratio and voltage angle (angle between the reference vector and the q-axis) ranges to satisfy the given q-axis (or d-axis) current fluctuation requirement based on this model. To solve this problem, in this paper, we derived an improved flux ripple model by applying coordinate transformation to the traditional flux ripple model, which can be used to calculate the RMS (root mean square) value of the q-axis and the total flux ripple distribution within sector I under different modulation ratios and voltage angle ranges. The modulation ratio and voltage angle range of low-carrier-ratio modulation strategy (0121 sequence) with a smaller RMS value of flux ripple compared to the traditional modulation strategy (0127 sequence) was determined based on the calculated results of the RMS values of the flux ripple. It was concluded that the 0121 sequence is suitable for high-modulation-ratio conditions as a result of analysis by applying the proposed method to determine the proper working conditions for the low-carrier-ratio modulation strategy, and there was an improvement effect of reducing the current ripple and THD by adopting a low-carrier-ratio modulation strategy instead of the traditional modulation strategy in high-modulation-ratio conditions. The validity of the proposed improved flux ripple analysis method and low-carrier-ratio modulation strategy has been verified by simulation and experiment.
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Li, Huanyu, Miao Li, Chenhong Zhengs, and Bingqian Chen. "Comparison between Modified MPC and DTC Control Method for Permanent Magnet Synchronous Motor." E3S Web of Conferences 115 (2019): 02004. http://dx.doi.org/10.1051/e3sconf/201911502004.
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Direct torque control (DTC) and model predictive control (MPC) are widely used in the control of permanent magnet synchronous motor (PMSM). However, DTC for PMSM can cause large torque ripples and flux ripples, high harmonic distortion of the stator current, and high acoustic noises. Compared to DTC, MPC considers all possible switching states which can reduce the ripples of torque and flux. MPC with one-step delay compensation for PMSM and DTC with one-step delay compensation and two hysteresis comparators for PMSM have been proposed to solve some drawbacks of these two controllers. This paper makes a detailed comparison between these two improved control methods through Simulink and hardware experiments results to analyse the four indicators-torque ripple, flux ripple, transient time and THD of inverter current.
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Ning, Jian Rong, Cheng Yuan Wang, Jia Kuan Xia, and Li Shen. "Current Compensation Control Strategy for Reduction Normal Force Ripple of PMLSM." Advanced Materials Research 433-440 (January 2012): 7275–80. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.7275.
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The ripple normal force of permanent magnet linear synchronous motor (PMLSM) can directly deteriorate the machining accuracy of ultra-precision CNC machine tool which use linear motor direct drive. First, the normal force of PMLSM was calculated using finite element method (FEM) .then, id current compensate lookup table was established by indexing iq current, gap and position of mover .In order to reduce the ripple of normal force and keep the thrust steady, PMLSM current compensation control system was realized by injecting the id current to counteract the normal force ripples using field oriented control (FOC) method. The effectiveness of this proposed method is verified by the simulation using Matlab according to the comparison between the compensation and no compensation cases.
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Faraci, Carla, Pietro Scandura, Carmelo Petrotta, and Enrico Foti. "Wave-Induced Oscillatory Flow Over a Sloping Rippled Bed." Water 11, no. 8 (August 5, 2019): 1618. http://dx.doi.org/10.3390/w11081618.
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In this paper, the findings of an experimental analysis aimed at investigating the flow generated by waves propagating over a fixed rippled bed within a wave flume are reported. The bottom of the wave flume was constituted by horizontal part followed by a 1:10 sloping beach. Bedforms were generated in a previous campaign performed with loose sand, and then hardened by means of thin layers of concrete. The flow was acquired through a Vectrino Profiler along two different ripples, one located in the horizontal part of the bed and the second over the sloping beach. It was observed that, on the horizontal bed, near the bottom, ripple lee side triggered the appearance of an onshore directed steady streaming, whereas ripple stoss side gave rise to an offshore directed steady streaming. On the sloping bed, a strong return current appears at all positions, interacting with the rippled bottom. The turbulence is non-negligible within the investigated water depth, particularly when velocities were onshore directed, due to flow asymmetry. Turbulence caused a considerable flow stirring which, above a non-cohesive bed, could lift the sediment up in the water column and give rise to a strong sediment transport.
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Ahmed, Dris, Bendjebbar Mokhtar, and Belaidi Aek. "DTC-ANN-2-level hybrid by neuronal hysteresis with mechanical sensorless induction motor drive using KUBOTA observer." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 1 (March 1, 2020): 34. http://dx.doi.org/10.11591/ijpeds.v11.i1.pp34-44.
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In this paper, DTC is applied for two-level inverter fed IM drives based on neuronal hysteresis comparators and The Direct Torque Control (DTC) is known to produce quick and robust response in AC drive system. However, during steady state, torque, flux and current ripple. An improvement of electric drive system can be obtained using a DTC method based on ANNs which reduces the torque and flux ripples, the estimated the rotor speed using the KUBOTA observer method based on measurements of electrical quantities of the motor. The validity of the proposed methods is confirmed by the simulation results.The THD (Total Harmonic Distortion) of stator current, torque ripple and stator flux ripple are determined and compared with conventional DTC control scheme using Matlab/Simulink environment.
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Senthilnathan, A., P. Palanivel, and K. Ramash Kumar. "Mathematical Modelling and Torque Ripple Waning in BLDC Motor Using Outgoing-Phase Current Discharge Hysteresis Controlled ANFIS Controller." Mathematical Problems in Engineering 2022 (June 25, 2022): 1–21. http://dx.doi.org/10.1155/2022/3971695.
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This study focused on approaches for reducing torque ripples in Permanent Magnet Brushless Direct current motors (PMBLDC) to provide sophisticated performance and reliable machine drives for both industrial and consumer applications. Torque ripples are caused by current ripple, nonsinusoidal Back Electromotive Force (EMF), and cogging torque at the Brushless Direct Current Motor (BLDCM) output. Acoustic emissions are produced when the torque ripple creates vibrations in the mechanical system, which interacts with the motor housing and reduces the life span of the motor. The BLDC’s uses are limited due to these acoustic emissions. Proportional-Integral (PI), Fuzzy Logic Control (FLC), and Adaptive Neuro-Fuzzy Inference System (ANFIS) speed controller approaches were used to construct and analyze the mathematical model of the BLDC motor in the MATLAB environment. The Adaptive Neurofuzzy Inference System (ANFIS) speed control system has solved the shortcomings of the PI and Fuzzy Logic Control (FLC) techniques. Because of FLC interpolation and flexibility, ANFIS is one of the finest trade-offs between neural and fuzzy systems, allowing for smooth control. Model compactness, a smaller training set, and faster convergence are all benefits of the ANFIS approach over traditional feedforward NN. In this research proposal, a simple control approach based on outgoing phase current discharge hysteresis control (OGCDHC) with minimal torque ripple is presented.
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Choi, Gyuri, Kyeongsik Nam, Mookyoung Yoo, Sanggyun Kang, Byeongkwan Jin, Kyounghwan Kim, Hyeoktae Son, and Hyoungho Ko. "Current-Feedback Instrumentation Amplifier Using Dual-Chopper Fill-in Technique." Applied Sciences 12, no. 20 (October 17, 2022): 10471. http://dx.doi.org/10.3390/app122010471.
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In this study, we describe a dual-chopper glitch-reduction current-feedback instrumentation amplifier (CFIA) with a ripple reduction loop. The amplifier employs the chopping technique to reduce low-frequency noise, such as 1/f noise. A glitch caused by chopping occurs at each chopper clock edge and results in intermodulation distortion (IMD). Owing to the input offset, the chopping technique also produces ripples. In this study, the glitch-induced IMD was reduced using a fill-in technique whereby only neat signals were alternately used as outputs by avoiding the glitch section with dual-chopping channel CFIA. To avoid using a high-order, low-frequency filter, a ripple reduction loop was implemented to reduce the ripple generated by chopping. The CFIA is based on a low-noise chopper fully differential difference amplifier with a cascode stage and a Monticelli-class AB output stage, which can drive a larger load and increase power efficiency. The proposed dual-chopper CFIA was fabricated using a 0.18 µm CMOS standard process, and its current consumption with a 1.8-V power supply is 29.5 μA. The proposed CFIA has a gain of 51 V/V, input referred noise of 53.3 nV/√Hz at 1 Hz, and a noise efficiency factor of 4.48.
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Lur’e, M. S., O. M. Lur’e, and A. S. Frolov. "Suppression of Ripples of Controllable Rectifiers for Power Supply of Magnetic Systems." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 65, no. 4 (August 2, 2022): 317–30. http://dx.doi.org/10.21122/1029-7448-2022-65-4-317-330.
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A number of requirements are imposed on installations associated with regulated DC sources, including low voltage and current ripple in the load, as well as a wide range of output current variation. Such installations are traditionally made on controlled rectifiers or pulse-width converters in which voltage ripples are always present. The paper considers a method for reducing the voltage ripple of powerful rectifiers for powering magnetic systems based on the insertion of a compensating voltage equal in magnitude and opposite in phase to the ripple voltage into the load circuit. The possibility of using ripple compensators connected in parallel and in series with the load, as well as methods of obtaining a compensating voltage is shown. Methods for obtaining compensating voltage are given. In order to exclude the magnetization of the ripple compensator transformer, it is proposed to use several versions of the compensating transformer and the inclusion of ripple compensators. Practical schemes of passive compensators (with a demagnetizing circuit and a bifilar winding) are analyzed. The problem of developing ripple compensators for multiphase rectifiers, as well as ways to solve it, is considered. Practical recommendations for choosing a core material and calculating a transformer are given. On the basis of the presented theoretical and practical considerations for the design of the ripple compensators, simulation models have been developed in the Simulink pack-age of the MATLAB program. A technique for studying ripple compensators using the simulation models of a symmetrical 12-pulse rectifier that has been developed is presented. The results of simulation of passive ripple compensators, performed in two versions, showed their effectiveness, while the scheme was relatively simple and economic costs were relatively low. Also, the time of setting the set current in the system in the presence of a ripple compensator increases by no more than 3 %, and the accuracy and stability of operation do not change.
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Salah, Wael, Dahaman Ishak, and Khaleel Hammadi. "PWM Switching Strategy for Torque Ripple Minimization in BLDC Motor." Journal of Electrical Engineering 62, no. 3 (May 1, 2011): 141–46. http://dx.doi.org/10.2478/v10187-011-0023-1.
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PWM Switching Strategy for Torque Ripple Minimization in BLDC Motor This paper describes a new PWM switching strategy to minimize the torque ripples in BLDC motor which is based on sensored rotor position control. The scheme has been implemented using a PIC microcontroller to generate a modified Pulse Width Modulation (PWM) signals for driving power inverter bridge. The modified PWM signals are successfully applied to the next up-coming phase current such that its current rise is slightly delayed during the commutation instant. Experimental results show that the current waveforms of the modified PWM are smoother than that in conventional PWM technique. Hence, the output torque exhibits lower ripple contents.
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König, Niklas, Matthias Nienhaus, and Emanuele Grasso. "Analysis of Current Ripples in Electromagnetic Actuators with Application to Inductance Estimation Techniques for Sensorless Monitoring." Actuators 9, no. 1 (March 6, 2020): 17. http://dx.doi.org/10.3390/act9010017.
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Techniques for estimating the plunger position have successfully proven to support operation and monitoring of electromagnetic actuators without the necessity of additional sensors. Sophisticated techniques in this field make use of an oversampled measurement of the rippled driving current in order to reconstruct the position. However, oversampling algorithms place high demands on AD converters and require significant computational effort which are not desirable in low-cost actuation systems. Moreover, such low-cost actuators are affected by eddy currents and parasitic capacitances, which influence the current ripple significantly. Therefore, in this work, those current ripples are modeled and analyzed extensively taking into account those effects. The Integrator-Based Direct Inductance Measurement (IDIM) technique, used for processing the current ripples, is presented and compared experimentally to an oversampling technique in terms of noise robustness and implementation effort. A practical use case scenario in terms of a sensorless end-position detection for a switching solenoid is discussed and evaluated. The obtained results prove that the IDIM technique outperforms oversampling algorithms under certain conditions in terms of noise robustness, thereby requiring less sampling and calculation effort. The IDIM technique is shown to provide a robust position estimation in low-cost applications as in the presented example involving a end-position detection.
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Li, Jun, Jun Hong Zhang, and Wei Gao. "Double Pulse Modulation on Current Ripple Suppression." Advanced Materials Research 988 (July 2014): 457–60. http://dx.doi.org/10.4028/www.scientific.net/amr.988.457.
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In the process of the DC-DC conversion, suppressing the output current ripple is very important. Compared with conventional single pulse modulation mode ,double-pulse modulation can more effectively suppress the output current ripple. By principle analysis, the formula is derived, and finally through simulation proved double pulse modulation can suppress the current ripple effectively.
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Farhadi, Arman, Amir Akbari, Ali Zakerian, and Mohammad Tavakoli Bina. "An Improved Model Predictive Control Method to Drive an Induction Motor Fed by Three-Level Diode-Clamped Indirect Matrix Converter." International Journal of Engineering and Technology Innovation 10, no. 4 (September 29, 2020): 265–79. http://dx.doi.org/10.46604/ijeti.2020.5870.
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In this paper, an improved model predictive control method is proposed to drive an induction motor fed by a three-level matrix converter. The main objective of this paper is to present a novel method to increase the switching frequency at a constant sampling time. Also, it is analytically discussed that increasing the switching frequency not only can decrease the motor current ripples, but it can also significantly reduce its torque ripples. Finally, this study demonstrates that reducing the motor current ripple will improve the quality of the supply current. To be the accurate model and validate the motor drive system, a co-simulation method, which is a combination of FLUX and MATLAB software packages, is employed to find the simulation results. The findings indicate that the proposed method diminishes the THD of the supply current up to 26% approximately. Furthermore, increasing the switching frequency results in the torque ripple reduction by up to 10% almost.
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Gerstner, Cynthia L., and Paul W. Webb. "The station-holding performance of the plaice Pleuronectes platessa on artificial substratum ripples." Canadian Journal of Zoology 76, no. 2 (February 1, 1998): 260–68. http://dx.doi.org/10.1139/z97-192.
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The ability to maintain position in a current (station-holding) was determined for the plaicePleuronectes platessa on a simple form of habitat structure, substratum ripples. Twelve sinusoidal combinations of ripple wavelength and amplitude were tested, with wavelengths approximating 0.5, 1, 2, and 5 times fish total length. Although ripple flow patterns varied, all provided regions of retarded flow in the ripple troughs. Therefore, ripples affected station-holding performance in the following three ways: (1) directly, by providing regions of retarded flow, thus creating flow refuges, (2) indirectly, by interfering with behaviors deferring the onset of active swimming, and (3) indirectly, by providing opportunities for new behaviors deferring swimming. The direct effects of retarded flow on performance versus\i indirect effects via swim-deferring behavior were evaluated. Flow retardation was measured as the velocity ratio (utrough/ufree-stream), where utrough is the velocity measured 0.5 cm from the bottom of a trough and ufree-stream is the velocity measured 10 cm above ripple crests. At a velocity ratio >0.4, direct flow-retardation effects were most important in determining observed performance. At a velocity ratio <0.4, indirect interference affected performance. Performance of plaice was maximized on ripples with wavelengths approximately twice their total body length.
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Rosas-Caro, Julio C., Pedro M. García-Vite, Alma Rodríguez, Abraham Mendoza, Avelina Alejo-Reyes, Erik Cuevas, and Francisco Beltran-Carbajal. "Differential Evolution Based Algorithm for Optimal Current Ripple Cancelation in an Unequal Interleaved Power Converter." Mathematics 9, no. 21 (October 29, 2021): 2755. http://dx.doi.org/10.3390/math9212755.
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This paper proposes an optimal methodology based on the Differential Evolution algorithm for obtaining the set of duty cycles of a recently proposed power electronics converter with input current ripple cancelation capability. The converter understudy was recently introduced to the state-of-the-art as the interleaved connection of two unequal converters to achieve low input current ripple. A latter contribution proposed a so-called proportional strategy. The strategy can be described as the equations to relate the duty cycles of the unequal power stages. This article proposes a third switching strategy that provides a lower input current ripple than the proportional strategy. This is made by considering duty cycles independently of each other instead of proportionally. The proposed method uses the Differential Evolution algorithm to determine the optimal switching pattern that allows high quality at the input current side, given the reactive components, the switching frequency, and power levels. The mathematical model of the converter is analyzed, and thus, the decision variables and the optimization problem are well set. The proposed methodology is validated through numerical experimentation, which shows that the proposed method achieves lower input current ripples than the proportional strategy.
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Baburajan, Silpa, Haoran Wang, Dinesh Kumar, Qian Wang, and Frede Blaabjerg. "DC-Link Current Harmonic Mitigation via Phase-Shifting of Carrier Waves in Paralleled Inverter Systems." Energies 14, no. 14 (July 13, 2021): 4229. http://dx.doi.org/10.3390/en14144229.
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DC-connected parallel inverter systems are gaining popularity in industrial applications. However, such parallel systems generate excess current ripple (harmonics) at the DC-link due to harmonic interactions between the inverters in addition to the harmonics from the PWM switching. These DC-link harmonics cause the failure of fragile components such as DC-link capacitors. This paper proposes an interleaving scheme to minimize the current harmonics induced in the DC-link of such a system. First, the optimal phase-shift angle for the carrier signal is investigated using the analytical equations, which provides maximum capacitor current ripple cancellation (i.e., at the main switching frequency harmonic component). These optimally phase-shifted switching cycles lead to variations of the output current ripples, which, when summed together at the DC-link, result in the cancellations of the DC-link current ripples. The results show that when the carrier waves of the two inverters are phase-shifted by a 90° angle, the maximum high-frequency harmonic ripple cancellation occurs, which reduces the overall root-mean-square (RMS) value of the DC-capacitor current by almost 50%. The outcome of this proposed solution is a cost-effective DC-harmonics mitigating strategy for the industrial designers to practically configure multi-inverter systems, even when most of the drives are not operating at rated power levels. The experimental and simulation results presented in this paper verify the effectiveness of the proposed carrier-based phase-shifting scheme for two different configurations of common DC connected multi-converter systems.
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Wang, Haichao, Guorun Yang, Wei Kang, Xinsheng Zhang, Xuexin Fan, and Fei Xiao. "Minimum-Output-Current-Ripple Control of Current-Fed Three-Level Phase-Shift Full-Bridge Converter." Energies 15, no. 17 (September 3, 2022): 6444. http://dx.doi.org/10.3390/en15176444.
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Electrified ports using medium-voltage DC (MVDC) renewable energy microgrids require current-fed dc/dc converters in application scenarios such as battery or ultracapacitor charging units and hydrogen production systems. This paper designs a three-level phase-shift full-bridge (TL-PSFB) converter that interfaces with the MVDC microgrid. Its operation in the current source mode requires a wide output voltage range and small output current ripple. Firstly, the dual-output TL-PSFB topology is introduced, and the principle of phase-shift pulse width modulation (PS-PWM) is presented. Secondly, the principle of the traditional constant-conduction-duty-cycle (CCDC) strategy is analyzed. Then, a minimum-output-current-ripple (MOCR) strategy is proposed by analyzing the relationship between output current ripple, conducting-duty cycle, and phase-shift duty cycle, and a constant current control combined with the MOCR strategy is designed. The output current ripple of the MOCR strategy is smaller than that of the CCDC strategy in a full range of operating conditions. Under the same output current ripple design index, the value and loss of the filter inductor can be reduced with the MOCR strategy. In addition, the MOCR strategy can widen the output voltage regulation range and increase the bus voltage utilization without causing significant changes to the total harmonic distortion (THD) of primary voltage. Finally, experimental results verify the correctness of the theoretical analysis.
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Weigold, J., and M. Braun. "Predictive Current Control Using Identification of Current Ripple." IEEE Transactions on Industrial Electronics 55, no. 12 (December 2008): 4346–53. http://dx.doi.org/10.1109/tie.2008.2007517.
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Dabour, Sherif M., Ahmed A. Aboushady, I. A. Gowaid, Mohamed A. Elgenedy, and Mohamed E. Farrag. "Performance Analysis and Evaluation of Multiphase Split-Source Inverters." Energies 15, no. 22 (November 10, 2022): 8411. http://dx.doi.org/10.3390/en15228411.
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Due to their many advantages over their counterparts, such as Z-source inverters (ZSIs), split-source inverters (SSIs) have recently received much attention as single-stage boost inverters. This paper discusses a multiphase version of the SSI topology for the first time. Among multiphase systems undergoing a revolution in the research area, five-phase motor drives are a relatively practical selection in industrial applications. Therefore, this paper focuses on a five-phase SSI as an example. The topology, operating principles, modulation techniques, and performance analysis of the analyzed topology are introduced. A modified space-vector modulation (MSVM) scheme is developed to eliminate low-frequency ripples in the input current. There is also a detailed analysis and graphical evaluation of the output currents ripples using the space-vector approach. It is evident that multiphase SSI is suitable for motor drives, especially when a high-output voltage gain is required. In addition to having a nearly identical ripple in output current to a conventional VSI, it has the benefit of performing the boosting action in a single stage with fewer passive components and a low ripple in input current. Finally, the simulation and experimental results have been conducted to demonstrate the viability of the multiphase SSI studied in the theoretical study and analysis.
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Huang, Chien-Chun, Yu-Chen Liu, Chia-Ching Lin, Chih-Yu Ni, and Huang-Jen Chiu. "Stacked Buck Converter: Current Ripple Elimination Effect and Transient Response." Energies 14, no. 1 (December 24, 2020): 64. http://dx.doi.org/10.3390/en14010064.
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To balance the cost and volume when applying a low output current ripple, the power supply design should be able to eliminate the current ripple under any duty cycle in medium and high switching frequencies, and considerably reduce filter volume to improve power density. A stacked buck converter was eventually selected after reviewing the existing solutions and discussing their advantages and disadvantages. A stacked buck converter is used as a basis to propose the transient response and output current ripple elimination effect, boundary limit control method, and low output ripple dead time modulation method to make individual improvements. The principle, mathematical derivation, small-signal model, and compensator design method of the improvement method are presented in detail. Moreover, simulation results are used to mutually verify the correctness and effectiveness of the improvement method. A stacked buck converter with 330-V input, 50-V output, and 1-kW output power was implemented to verify the effect of the low output current ripple dead time modulation. Experimental results showed that the peak-to-peak value of the output current ripple was reduced from 2.09 A to 559 mA, and the RMS value was reduced from 551 mA to 91 mA, thereby effectively improving the output current ripple.
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Mandrioli, Riccardo, Manel Hammami, Aleksandr Viatkin, Riccardo Barbone, Davide Pontara, and Mattia Ricco. "Phase and Neutral Current Ripple Analysis in Three-Phase Four-Wire Split-Capacitor Grid Converter for EV Chargers." Electronics 10, no. 9 (April 24, 2021): 1016. http://dx.doi.org/10.3390/electronics10091016.
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The current switching ripple in a three-phase four-wire split-capacitor converter is analyzed in this paper for all the four ac output wires in relation to both balanced and unbalanced working conditions. Specifically, analytical formulations of the peak-to-peak and root mean square (RMS) current ripples are originally evaluated as a function of the modulation index, separately for the three phases and the neutral wire. Initially, the single-carrier sinusoidal pulse width modulation (PWM) technique is outlined, as it generally concerns a straightforward and effective modulation. With the aim of mitigating the current ripple in the neutral wire, the interleaved multiple-carrier PWM strategy is adopted, also avoiding any repercussion on the phase one. Numerical simulations and experimental tests were carried out to verify all the analytical developments.
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Boudouda, Aimad, Nasserdine Boudjerda, and Fares Nafa. "Analysis of output voltage ripple for dual randomized PWM buck converter operating in continuous and discontinuous conduction modes." Acta Polytechnica 62, no. 2 (May 5, 2022): 262–73. http://dx.doi.org/10.14311/ap.2022.62.0262.
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Dual Randomized Pulse Width Modulation (DRPWM) is renowned for its better effectiveness than Simple Randomized Pulse Width Modulation (SRPWM) in reducing conducted Electro-Magnetic Interferences (EMI) in power converters. However, the introduction of low-frequency ripples into the output voltage by dual randomization has not yet been addressed; this effect is investigated in this paper for a buck converter operating in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, the modulating principle is presented. Then, a general analytical expression for power spectral density (PSD) of the input current is derived and validated for the proposed DRPWM scheme for both the CCM and DCM. A comparison of the PSDs of the input current for all RPWM schemes in both the CCM and DCM shows the PSD spreading effectiveness of the dual scheme as compared to simple schemes. Finally, the low-frequency output ripple is analysed using the PSD of output voltage. The results reveal that the output voltage ripple is affected by all the randomized schemes in both the CCM and the DCM. Also, the dual scheme (RCFM-RPPM) introduces the highest low-frequency voltage ripple, especially in the CCM and for low duty cycles. In DCM, the RPPM scheme gives the lowest voltage ripple, while the RCFM scheme gives the lowest voltage ripple in the CCM. The results are confirmed by both theory and simulations.
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Rosner, Marcel, and Andrew Kang. "Understanding and Regulating Twenty-First Century Payment Systems: The Ripple Case Study." Michigan Law Review, no. 114.4 (2016): 649. http://dx.doi.org/10.36644/mlr.114.4.understanding.
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Ripple is an open-source Internet software that enables users to conduct payments across national boundaries in multiple currencies as seamlessly as sending an email. This decentralized Internet payment protocol could provide a cure to an inefficient cross-border payments system. Although Ripple’s technology can reduce significant risks and costs that exist in the international payments system, regulators should adopt a new regulatory framework that responds to how this technology works. This Note performs two functions to help regulators realize this goal. It first helps regulators and other market participants understand how Ripple operates by explaining what Ripple is and comparing it to current payments systems. Second, it suggests a series of principles that regulators should use to monitor decentralized Internet payment protocols like Ripple. It does this by drawing from and tailoring existing regulatory principles to account for the risks reduced and presented by Ripple.
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He, Jun Ping, Jin Lu Wang, and Guo Zhuang Bai. "Design and Analysis of a Novel Interleaving LLC SMPS with Load Current Sharing Performance." Advanced Materials Research 677 (March 2013): 346–53. http://dx.doi.org/10.4028/www.scientific.net/amr.677.346.
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LLC series resonant topology has been widely adopted in many kinds of power converters for its high frequency, high efficiency and high power density advantages. However, the ordinary topology of a single-phase LLC is not fit to be used in low-voltage high-current output field for its relative larger output voltage ripple. In order to provide a low voltage and high current output using a LLC topology, a novel interleaving LLC switched-mode power supply design was proposed to reduce output voltage ripples ripple in this paper. This design used two hardware measures to automatically ensure a good load current sharing effect between two-branch LLC circuits and avoid the PFM difficulties of the active current sharing methods. The principles and design procedures of this novel LLC converter were introduced in detail and verified by Saber simulation results. A 1.5kW DC/DC prototype was built up in the end and the experiment results showed that a good current sharing performance was achieved.
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Goodrich, L. F., and J. D. Splett. "Current Ripple Effect on $n$-Value." IEEE Transactions on Applied Superconductivity 17, no. 2 (June 2007): 2603–6. http://dx.doi.org/10.1109/tasc.2007.899592.
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Pan, Ching-Tsai, Ching-Ming Lai, and Yu-Lin Juan. "Output Current Ripple-Free PWM Inverters." IEEE Transactions on Circuits and Systems II: Express Briefs 57, no. 10 (October 2010): 823–27. http://dx.doi.org/10.1109/tcsii.2010.2058596.
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Matsuyama, S., M. Fujisawa, T. Nagaya, K. Ishii, A. Terakawa, Y. Kikuchi, M. Fujiwara, et al. "Improvement of the energy stability of the Tohoku Dynamitron accelerator for microbeam and nanobeam applications." International Journal of PIXE 23, no. 01n02 (January 2013): 69–75. http://dx.doi.org/10.1142/s0129083513400081.
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The microbeam system at Tohoku University has various applications. Recently higher spatial resolution down to several hundred nm and higher beam current with the resolution of several μm were required. To meet these requirements, a triplet lens system was installed. While the triplet system has higher demagnification, the chromatic aberration is much larger than in the doublet system. To achieve better performance in the triplet system, improvements in the energy resolution of the accelerator are required. Various sources of accelerator voltage ripples were investigated. The high voltage generating circuit was symmetrized and the noise components were reduced to minimize the voltage ripple. The voltage ripple of the accelerator for low-frequency components was reduced to around 70 V. The voltage ripple of the 120-kHz component was 140 Vp-p.
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Shan, Hong Tao, Yuan Ling Cai, and Yu Zhang. "The Research of Current Ripple on Interleaving Parallel High-Frequency Rectifier." Advanced Materials Research 354-355 (October 2011): 1363–66. http://dx.doi.org/10.4028/www.scientific.net/amr.354-355.1363.
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Interleaving Parallel is the unique technology with the combination of SPWM modulation technology with multiple technology. This paper was researched the interleaving parallel rectifier technology in restraining the AC side current ripple in detail, and compared current ripple in the AC side between the single rectifier and the interleaving parallel rectifier. The research was deduced that current ripple in the AC side of the interleaving parallel rectifier was lessened than the same parameters of the single rectifier. The relevant simulations were verified the characteristic of restraining the current ripple in the AC side in interleaving High-Frequency rectifier was effective.
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Brakenhoff, Laura, Reinier Schrijvershof, Jebbe van der Werf, Bart Grasmeijer, Gerben Ruessink, and Maarten van der Vegt. "From Ripples to Large-Scale Sand Transport: The Effects of Bedform-Related Roughness on Hydrodynamics and Sediment Transport Patterns in Delft3D." Journal of Marine Science and Engineering 8, no. 11 (November 8, 2020): 892. http://dx.doi.org/10.3390/jmse8110892.
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Bedform-related roughness affects both water movement and sediment transport, so it is important that it is represented correctly in numerical morphodynamic models. The main objective of the present study is to quantify for the first time the importance of ripple- and megaripple-related roughness for modelled hydrodynamics and sediment transport on the wave- and tide-dominated Ameland ebb-tidal delta in the north of the Netherlands. To do so, a sensitivity analysis was performed, in which several types of bedform-related roughness predictors were evaluated using a Delft3D model. Also, modelled ripple roughness was compared to data of ripple heights observed in a six-week field campaign on the Ameland ebb-tidal delta. The present study improves our understanding of how choices in model set-up influence model results. By comparing the results of the model scenarios, it was found that the ripple and megaripple-related roughness affect the depth-averaged current velocity, mainly over the shallow areas of the delta. The small-scale ripples are also important for the suspended load sediment transport, both indirectly through the affected flow and directly. While the current magnitude changes by 10–20% through changes in bedform roughness, the sediment transport magnitude changes by more than 100%.
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Yaseen, Md, and Dr P. Usha. "Transformerless high gain boost converter for low power applications with feedback control." TELKOMNIKA Indonesian Journal of Electrical Engineering 16, no. 2 (November 1, 2015): 244. http://dx.doi.org/10.11591/tijee.v16i2.1609.
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A transformer-less boost converter which provides high voltage gain without utilizing transformer or coupled inductors and extreme duty cycle is proposed in this paper. Also it is able to cancel the ripples in the input current at a preselected duty cycle, without increasing the number of components. The converter combines the features of boost converter and a three switch high voltage converter. At the input side, two inductors are interleaved for cancelling the input current ripple and at the output side switched capacitor voltage multiplier is used to increase the voltage gain. Feedback control is used to make the output voltage constant in spite of variation in the input or load or both i.e. both line and load regulation is accompanied. This proposed converter configuration helps eliminate the input current ripple and provides voltage deregulation for low power applications.
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Tang, Yufeng, Zhiyong Li, Yougen Chen, and Renyong Wei. "Ripple Vector Cancellation Modulation Strategy for Single-Phase Quasi-Z-Source Inverter." Energies 12, no. 17 (August 30, 2019): 3344. http://dx.doi.org/10.3390/en12173344.
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The double-frequency (2ω) power flows through the DC side of the single-phase quasi-Z-source inverter (QZSI) leads to the 2ω voltage ripple of capacitors and 2ω current ripple of inductors. This paper proposes a ripple vector cancellation modulation strategy (RVCMS) based on the thought of ripple vector cancellation. By analyzing the mechanism of ripple generation and transmission, we can obtain a variation of a shoot-through duty cycle to generate a compensated 2ω ripple used to cancel the 2ω current ripple of inductors caused by the 2ω ripple of DC link current, and the 2ω compensated variation of a shoot-through duty cycle with a specific amplitude and phase is added to the constant shoot-through duty cycle. Finally, simulation and experimental results demonstrate the correctness and effectiveness of the proposed modulation strategy for the single-phase QZSI.
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Cai, Hui, Hui Wang, Mengqiu Li, Shiqi Shen, Yaojing Feng, and Jian Zheng. "Torque Ripple Reduction for Switched Reluctance Motor with Optimized PWM Control Strategy." Energies 11, no. 11 (November 20, 2018): 3215. http://dx.doi.org/10.3390/en11113215.
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The high current ripple and torque ripple are the main drawbacks of the switched reluctance motor (SRM) since the nonlinearity and double saliency, which limits its applications. In order to eliminate the current variation and torque ripple, an optimized pulse width modulation (PWM) control is presented in this paper. The voltage ratio duty is able to be predicted precisely according to the information of the motor running parameter. Based on torque sharing functions (TSFs), the current profile is pre-computed and four regions are defined according to the reference current profiles. The three modes, excitation, demagnetization and freewheeling, are flexibly chosen according to the characteristic of the current profile. It is indicated that it is better than that of conventional PWM modulation in terms of current ripple and the current tracing performance is improved without increasing the switching frequency or changing the hysteresis band. The current ripple is defined as the peak-to-peak value dividing the average value and it is reduced by 40%. A comparison in terms of the torque ripple and copper loss is also carried out: the torque ripple is significantly reduced via the proposed scheme under both magnetic linear and saturation conditions. The torque ripple and copper loss are reduced by about 70% and 12%, respectively. The validity and effectiveness of the proposed control strategy is verified by simulation and experimental results.
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Humbyrd, Chelsea Joy, and Ole Secher Madsen. "PREDICTING MOVABLE BED ROUGHNESS IN COASTAL WATERS." Coastal Engineering Proceedings 1, no. 32 (January 29, 2011): 6. http://dx.doi.org/10.9753/icce.v32.sediment.6.
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Accurately predicting movable bed roughness is essential to the analyses of transport processes, but when the bottom is rippled, as it commonly is in the coastal environment, characterizing the roughness is less straightforward than when the bottom is flat. The common method of predicting roughness, while effective, unnecessarily predicts ripple geometry and requires a model-dependent factor, which varies widely, relating ripple geometry and bottom roughness. We have therefore developed an alternative, more direct method of predicting bed roughness in the ripple regime: the wave energy dissipation factor is predicted from flow and sediment information and then any desired theoretical friction factor model is used to back-calculate the roughness. This paper describes the common and proposed methods of predicting roughness and presents results of preliminary testing of the methods with field data. Both methods adequately predict current velocities in wave-current field flows, with the proposed method yielding the smaller RMS-error of 3.1 cm/s. Remaining questions concerning the appropriate near-bottom orbital velocity required to describe field conditions must be resolved when additional field data becomes available.
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Zhang, Guozheng, Bingxu Wei, Xin Gu, Xinmin Li, Zhanqing Zhou, and Wei Chen. "Sector Subdivision Based SVPWM Strategy of Neutral-Point-Clamped Three-Level Inverter for Current Ripple Reduction." Energies 12, no. 14 (July 17, 2019): 2734. http://dx.doi.org/10.3390/en12142734.
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This paper presents a sector subdivision based space vector pulse width modulation (SVPWM) strategy with reduced current ripple for a three-level inverter. Using the output current ripple theory, closed-form expressions of average current ripple vectors for both continuous and discontinuous switching sequences are derived. Based on the sector and triangle distributions of conventional SVPWM strategy, each triangle is further divided into three small-regions. Then the switching sequence with the lowest magnitude of the average current ripple vector is applied in every small-region, so that the advantages of continuous pulse width modulation (CPWM) and discontinuous pulse width modulation (DPWM) under different modulation index conditions are combined to reduce the current ripple in the whole modulation range. The output performance of the proposed strategy is compared with the conventional CPWM and DPWM strategy, and experimental results verify that the proposed strategy could reduce the current ripple of three-level inverters effectively.
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Goodrich, L. F., and S. L. Bray. "Current ripple effect on superconductive d.c. critical current measurements." Cryogenics 28, no. 11 (November 1988): 737–43. http://dx.doi.org/10.1016/0011-2275(88)90137-3.
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Serrano, Javier, Javier Moriano, Mario Rizo, and Francisco Dongil. "Enhanced Current Reference Calculation to Avoid Harmonic Active Power Oscillations." Energies 12, no. 21 (October 25, 2019): 4075. http://dx.doi.org/10.3390/en12214075.
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Energy storage systems play a key role in the rise of distributed power generation systems, hence there is great interest in extending their lifetimes, which are directly related to DC current ripple. One of the ripple sources is the low-frequency active power fluctuations under unbalanced and distorted grid voltage conditions. Therefore, this paper addresses a multifrequency control strategy where the harmonic reference currents are calculated to reduce harmonic active power oscillations. The stationary reference frame (StRF) approach taken here improves the precision and computational time of the current reference calculation method. Additionally, in order to ensure safe converter operation when a multifrequency reference current is provided, a computational efficient peak current saturator is applied while avoiding signal distortion every time step. If the injected current harmonic distortion is to be minimized, which is a feature included in this work, the peak current saturator is a necessary requirement. Active power ripple is reduced even with frequency variations in the grid voltage using a well-known frequency-adaptive scheme. The simulation and experimental results prove the optimized performance for the control objective: power ripple reduction with minimum current harmonic distortion.
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Moreno-Sanchez, Pedro, Tim Ruffing, and Aniket Kate. "PathShuffle: Credit Mixing and Anonymous Payments for Ripple." Proceedings on Privacy Enhancing Technologies 2017, no. 3 (July 1, 2017): 110–29. http://dx.doi.org/10.1515/popets-2017-0031.
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Abstract The I owe you (IOU) credit network Ripple is one of the most prominent alternatives in the burgeoning field of decentralized payment systems. Ripple’s path-based transactions set it apart from cryptocurrencies such as Bitcoin. Its pseudonymous nature, while still maintaining some regulatory capabilities, has motivated several financial institutions across the world to use Ripple for processing their daily transactions. Nevertheless, with its public ledger, a credit network such as Ripple is no different from a cryptocurrency in terms of weak privacy; recent demonstrative deanonymization attacks raise important concerns regarding the privacy of the Ripple users and their transactions. However, unlike for cryptocurrencies, there is no known privacy solution compatible with the existing credit networks such as Ripple. In this paper, we present PathShuffle, the first path mixing protocol for credit networks. PathShuffle is fully compatible with the current credit networks. As its essential building block, we propose PathJoin, a novel protocol to perform atomic transactions in credit networks. Using PathJoin and the P2P mixing protocol DiceMix, PathShuffle is a decentralized solution for anonymizing path-based transactions. We demonstrate the practicality of PathShuffle by performing path mixing in Ripple.
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Kumar, Dileep, Surya Deo Choudhary, Md Tabrez, Afida Ayob, and Molla Shahadat Hossain Lipu. "Model Antiseptic Control Scheme to Torque Ripple Mitigation for DC-DC Converter-Based BLDC Motor Drives." Energies 15, no. 21 (October 22, 2022): 7823. http://dx.doi.org/10.3390/en15217823.
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Although brushless direct current motor (BLDCM) drives are becoming more popular in industrial and commercial applications, there are still significant difficulties and unresolved research issues that must be addressed. In BLDCM drives, commutation current ripple (CCR) and diode freewheeling during non-commutation zone (NCZ) are the major challenges. To overcome these limitations, this paper proposes a novel PWM-Model Antiseptic Control (PWM-MAC) technique to alleviate the freewheeling of the diode. The proposed PWM technique is used to alleviate the diode freewheeling in the NCZ, whereas the DCLV circuit is utilized to obtain variable DC-link voltage to address the CCR in the CZ. The MATLAB/Simulink results are included along with experimental results obtained from a laboratory prototype of 325 W. The proposed module reduces the current ripple by 31.7% and corresponding torque ripples are suppressed by approximately 32.5%. This evidences the performance of the proposed control technique.