Compensation Of Fluctuations Research Articles

100-km entanglement distribution with coexisting quantum and classical signals in a single fiber

The development of prototype metropolitan-scale quantum networks is underway and entails transmitting quantum information via single photons through deployed optical fibers spanning several tens of kilometers. The major challenges in building metropolitan-scale quantum networks are compensation for polarization fluctuation, high-precision clock synchronization, and compensation for cumulative transmission time fluctuations. One approach addressing these challenges is to copropagate classical probe signals in the same fiber as the quantum signal. Thus, both signals experience the same conditions, and the changes of the fiber can therefore be monitored and compensated. Here, we demonstrate the distribution of polarization-entangled quantum signals copropagating with the White Rabbit precision time protocol classical signals in the same single-core fiber strand at metropolitan-scale distances. Our results demonstrate the feasibility of this quantum-classical coexistence by achieving high-fidelity entanglement distribution between nodes separated by 100 km of optical fiber. This advancement is a significant step towards the practical implementation of robust and efficient metropolitan-scale quantum networks.

Novel chattering free binomial hyperbolic sliding mode controller for asymmetric cascaded E-type bonded T-type multilevel inverter-based dynamic voltage restorer to meliorate FRT capability of DFIG-based wind turbine

The endurance capability of Doubly Fed Induction Generator (DFIG)-based wind turbine to network against different disturbances is an important criterion to meet the recent grid codes requirements. This generator has to provide the required energy under the perturbation conditions which is principally specified by Fault Ride-Through (FRT) capability. It refers to safe and continuous operation of DFIG without interruption which has been performed by Dynamic Voltage Restorer (DVR) using fast and accurate compensation of the voltage fluctuations. This paper aims to introduce an innovative quasi-sinusoidal voltage synthesizer for DVR to enhance the power quality and power delivery. Hence, a new Asymmetric Cascaded E-type Bonded T-type Multilevel Inverter (ACEBTMI) with binary geometric progression form of DC sources is proposed to provide high-step staircase sinusoidal voltage containing low semiconductor switches. Then, accurate triggering signals for the suggested ACEBTMI corresponding to the voltage fluctuations have been provided by new Chattering Free Binomial Hyperbolic Sliding Mode Controller (CFBHSMC). To validate compensation capability of the proposed DVR, ACEBTMI part has been compared with some traditional and familiar multilevel inverters, and also CFBHSMC part has been compared with SMC, FLC and PID controllers. In precise, the simulation results have definitely confirmed the accurate tracking and robust control performance of CFBHSMC to support ACEBTMI-based DVR which enables DFIG to ride-through different voltage perturbations.

Acoustic Resonance Tuning by High-Order Lorentzian Mixing.

Nanoscale mechanical resonators have attracted a great deal of attention for signal processing, sensors, and quantum applications. Recent progress in ultrahigh-Q acoustic cavities in nanostructures allows strong interactions with various physical systems and advanced functional devices. Those acoustic cavities are highly sensitive to external perturbations, and it is hard to control those resonance properties since those responses are determined by the geometry and material. In this paper, we demonstrate a novel acoustic resonance tuning method by mixing high-order Lorentzian responses in an optomechanical system. Using weakly coupled phononic-crystal acoustic cavities, we achieve coherent mixing of second- and third-order Lorentzian responses, which is capable of the fine-tunability of the bandwidth and peak frequency of the resonance with a tuning range comparable to the acoustic dissipation rate of the device. This novel resonance tuning method can be widely applied to Lorentzian-response systems and optomechanics, especially active compensation for environmental fluctuation and fabrication errors.

Improved Single-Phase UPQC With Integrating Auxiliary Capacitor for Power Rating Reduction

Unified Power Quality Conditioner (UPQC) can well achieve comprehensive control for power quality. However, the power rating reductions of the series side and parallel side of the back-to-back connected converters in UPQC are hard to be achieved simultaneously, and they even restrict each other. In this paper, a new topology of UPQC is proposed. It has an LC filter coupled with an external capacitor at the series part. Besides, a comprehensive coordination strategy is proposed to operate the improved UPQC (iUPQC) at reactive power compensation (RPC) mode and voltage fluctuation compensation (VC). Specifically, to achieve the low power rating, the proposed control strategy makes the series part undertakes partial reactive power that needs to be compensated at the parallel side in RPC mode. At the same time, it makes the parallel side coordinates the series side to expand the optimal operation range in VC mode. Compared with the conventional UPQCs, the iUPQC can well reduce the power rating of back-to-back connected converters from both parallel and series sides. Moreover, the optimal parameters design method is also provided. Finally, the effectiveness of the proposed topology and control method is validated by both simulation and experimental results.

Design of Uniform Field Coils Based on the Ferromagnetic Coupling Effect Inside Single-Ended Open Magnetic Shielding Cylinder

This research proposes a novel method for designing uniform field coils inside a single-ended open magnetic shielding cylinder (MSC). It solves the problems of distorted magnetic field distribution and decreased uniformity resulting from the coupling between the coils and the single-ended open MSC. The magnetic field analytical model of the uniform field coils inside the single-ended open MSC with high-permeability materials is first established. Then, minimizing the sum of relative errors of the magnetic field in the target area is taken as the objective function, and the improved particle swarm optimization algorithm is adopted to optimize the structural parameters for ensuring high uniformity of the coils. The results of the simulation indicate that comparing this work with the Lee-Whiting coil in the single-ended open MSC, the maximum relative error of the magnetic field is reduced from 6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> to 2.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> and 6.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> . The experimental results also demonstrate the efficacy of the proposed method, and practicality for real-time compensation of magnetic field fluctuations within single-ended open MSC. The research content provides the basis for improving the performance of the magnetocardiography device.

Single -Phase Hybrid Converter With Series Voltage Compensation On The DC Bar Applied to Micro grids

This work presents the development of computer simulation of a topological structure of singlephase hybrid converter that aims to impose sinusoidal input current and the supply of a DC bus with regulated voltage using the voltage series compensation. With the increase in distributed generation by the use of DC renewable energy sources by microgrids, the characteristics of the structure proposed to make it an excellent alternative for applications involving the compensation of voltage fluctuations due to to the intermittence of microgeneration systems.

Enhanced Power Quality in Single-Phase Grid-Connected Photovoltaic Systems: An Experimental Study

The main aim of the research work presented in this paper consists of proposing an effective control scheme for a grid-connected single-phase photovoltaic (PV) system to enhance not only the power quality at the point of common coupling (PCC) but also to operate with a maximum power point tracking (MPPT) controller. Moreover, an orthogonal signal generator (OSG) module for effective grid synchronization, a current reference generation controller, and a PWM generating block have also been designed and included in this paper. The proposed control strategy allows the MPPT controller to switch to faulty mode and maintains the voltage according to network requirements using an adaptive neuro-fuzzy inference system (ANFIS)-based control whenever a fault occurs at the PCC. The performance of the analyzed control strategy, which is based on the static compensation of the DC-link voltage fluctuations in a grid-connected inverter powered by PV, is further explored through simulations in MATLAB, and the results are included in this paper. Moreover, the control scheme is implemented experimentally using a dSPACE DS 1104 control board and then assessed on a small laboratory-scale single-phase PV system that is subjected to some fault scenarios. The simulation and experimental results have shown improved power quality and robustness against grid fluctuations, resulting in better dynamic performance.

Ramp-Rate Control for Mitigation of Solar PV Fluctuations with Hybrid Energy Storage System

This paper proposes a ramp-rate control (RRC) for mitigation of solar PV fluctuations with a hybrid energy storage system (HESS). The highly fluctuating primary energy source causes photovoltaic (PV) generators to suffer from variable output capacity. Such variations can lead to instability in power systems and problems with power quality due to large PV penetration. The role of energy storage devices (ESSs) as a fluctuation compensator is suggested to minimize these issues using RRC. Distributed Generation Systems (DGs) have become a key challenge as the disruption of DG from the grid during faults results in severe difficulties such as power outages and voltage flickers. Low voltage ride through (LVRT) is a promising method for supplying reactive power under low voltage conditions. The proposed method will enable dynamic control of integrated battery storage (BS) to mitigate power fluctuations during the day while simultaneously charging or discharging the integrated super-capacitor (SC) storage to control sudden variations in a BS to a certain magnitude. A system for exchanging energy between the BS and the SC storage provides uninterrupted control of the rapid fluctuations of the passing cloud. The storage capacity savings are evaluated by using the RRC for the smoothing impact of geographical deflection on PV power production. Simulations conducted with real operational PV power output data taken every 1 s from the power plant during one year confirm the validity of the model. The OP-5700 HIL test-bench is used for the real-time results.

Compensation of plasma fluctuation induced shadowing effects in gas puff imaging data

For gas puff imaging (GPI) studies of turbulent processes in the plasma edge, it is often assumed that the emitted light is mainly proportional to the local electron density. This, however, only holds for low electron densities in the far scrape-off layer. As GPI typically only detects one emission line, data interpretation further inside the plasma (i.e. around the separatrix) is complicated by two effects. First, there is the strongly non-linear connection between plasma temperature and density and the measured line emission. This can lead to incorrect data interpretation such as an artificial doubling of the frequency of periodic plasma perturbations. Second, a shadowing effect in the neutral distribution can hamper the localization of turbulent structures and modes. For this study thermal helium beam data of an ASDEX Upgrade EDA H-mode scenario are analyzed. By comparing these measurements to a synthetic diagnostic, we demonstrate the presence of diagnostic effects and illustrate their origins. It is shown that when line intensity ratios are used for the analysis, instead of emission from individual lines, the underlying plasma dynamics can be well recovered. • Gas puff imaging techniques deliver detailed information of turbulent structures and filaments at the plasma edge region. • The analysis of emission data requires detailed information of the underlying atomic processes to prevent false interpretation of diagnostic effects. • This is demonstrated by comparing a synthetic helium beam diagnostic with measurement data. • It is shown that by analyzing ratios of two emission lines, diagnostic effects as shadowing or frequency doubling can be prevented. • This allows the diagnostic to resolve fast modes at the plasma edge region as demonstrated in an EDA H-mode scenario.

Measuring impacts of tax aggressinevess, earnings fluctuation and executive compensation on earnings management

Measuring impacts of tax aggressinevess, earnings fluctuation and executive compensation on earnings management

Mitigation of Thermal Stability Concerns in FinFET Devices

Here, we developed a procedure for mitigating thermal hazards in packaged FinFET devices. A monitoring system was installed into devices, based on self-heating impact analysis in the system and device levels, to allow for the observation and alerting of chip temperature and reliability risks. A novel algorithm for reducing measurement noise by means of temperature fluctuation compensation and the filtering of invalid data is presented and demonstrated on packaged devices. The results presented in this work show that the proposed techniques make exceptional improvements to sensory accuracy. Using this methodology enables the mitigation of thermal concerns in systems, including large data servers, and accelerates development of smart resource allocation formations.

Power fluctuation mitigation strategy for microgrids based on an LSTM-based power forecasting method

With the rapid penetration of renewable generation systems and active loads, the stability and reliability of modern power systems face several challenges owing to power fluctuations caused by renewable intermittency and load uncertainty. Power fluctuations are more significant in islanded microgrids that possess low inertia. Therefore, this study proposes a novel cost-effective proactive control strategy to mitigate power fluctuations of an islanded microgrid. The proposed strategy produces an early acting control reference for generators based on an improved ultra-short-term power fluctuation forecasting algorithm to significantly increase the fluctuation compensation capacity of the generators. Moreover, the size, workload, and cost of the energy storage system reduce. A combined LSTM neural network structure is employed to achieve accurate power fluctuation forecasting. The effectiveness of the proposed method is verified on an islanded hybrid AC/DC microgrid simulation platform.

A voltage fluctuation compensation control strategy at DC side for integrated power quality control device

The power quality control process in the integrated power quality control device, especially for three-phase unbalance control, usually leads to the capacitor voltage fluctuations on DC side. In rectifier control strategy, the output of the voltage loop is the reference value of the inner current loop, and the DC-side voltage is the reference value of the voltage loop. Therefore, the DC-side voltage instability will overlay a fluctuating component on the reference value, which affects the accuracy of the inner current loop control, causing a considerable impact on the transient performance of the integrated power quality control system. Hence, the stability of the DC-side voltage becomes the main factor of the current loop control strategy. Unfortunately, in practical applications, such fluctuations on DC side are inevitable. In this paper, the DC-side capacitor voltage fluctuation mechanism is studied, and a comprehensive power quality control strategy based on feed-forward compensation is proposed to mitigate the DC capacitor voltage fluctuation influence. The proposed compensation control strategy prevents the impact of DC-side voltage fluctuations on the control system. The simulation conducted on the developed experimental platform verified the feasibility and capability of the feed-forward control strategy of the integrated power quality control system.

Analysis of the Characteristics of a Biharmonic Oscillator with Two Synchronous Modes

The paper investigates the influence of the coupling coefficient of the double-loop filter forming a biharmonic oscillator on the quality factor and resonant impedance of the input impedance at the resonant frequencies of the double-loop filter. The resonant frequencies of the filter are exactly multiples of 2. In this paper show numerical results that simplify the choice of filter parameters to provide conditions for selfexcitation of two oscillations at exactly multiples of frequencies. Two synchronous modes allow to create a generator with compensation for fluctuations in the reactive component of the output impedance of the active element, which increase the phase noise of the oscillator.

Improved elemental quantification in copper ores by laser-induced breakdown spectroscopy with judicious data processing

The trading price and taxes of copper-concentrate exports depend on the chemical composition. Valuable elements such as Cu, Ag, and Mo increase the price while the presence of As reduces it. The quantification of these elements by laser induced breakdown spectroscopy (LIBS) in mineral ores with varied concentrations spanning from ppm to percentage is challenging. Several factors such as matrix effects, signal fluctuations (laser energy fluctuations, plasma instability, sample inhomogeneity), and self-absorption effects can contribute to analytical errors. Although advanced chemometric methods like artificial neural networks (ANN) can account for these limitations, tuning too many parameters may lead to overfitting of the results. Hence, to avoid overfitting, meaningful information should be fed to the model. In this work, a systematic procedure for getting meaningful LIBS spectral data i.e. “judicious data processing” is proposed. It consists of spectra normalization, feature selection and stratified data division. First, the normalization is done by using an internal standard (ISSN) considering emission lines (Al, Ca, Fe, Zn, and Si) of the main components of the matrix. Second, the feature selection is performed by identifying linearly correlated wavelengths (LCW) with the concentration of each target element. Third, stratified data division in the ANN regression is implemented. This approach, involving LIBS-ANN regression, is applied for multi-elemental quantification of valuable (Cu, Ag, Mo) and penalized (As) elements in copper ores. We compared the ANN models, considering features selection by LCW and prior knowledge spectral lines (PKSL), which are usually utilized in the literature. In terms of analytical figures, the root mean square error of predictions (RMSEP) using LCW improved for Cu (1.45% to 1.04%), Ag (8.5 mg·kg−1 to 6.0 mg·kg−1), and As (0.16% to 0.06%), while it remained unchanged for Mo (0.04%). These improvements can be attributed to the decrease of spectral interferences, caused by the selection of the least affected lines and the compensation of signal fluctuations by spectral normalization.

Measuring radiofrequency field-induced temperature variations in brain MRI exams with motion compensated MR thermometry and field monitoring.

An MR thermometry (MRT) method with motion and field fluctuation compensation is proposed to measure non-invasively sub-degree brain temperature variations occurring through radiofrequency (RF) power deposition during MR exams. MRT at 7T with a multi-slice echo planar imaging (EPI) sequence and concurrent field monitoring was first tested in vitro to assess accuracy in the presence of external field perturbations, an optical probe being used for ground truth. In vivo, this strategy was complemented by a motion compensation scheme based on a dictionary pre-scan, as reported in some previous work, and was adapted to the human brain. Precision reached with this scheme was assessed on eight volunteers with a 5 minute-long low specific absorption rate (SAR) scan. Finally, temperature rise in the brain was measured twice on the same volunteers and with the same strategy, this time by employing a 20-minutes scan at the maximum SAR delivered with a commercial volume head coil. In vitro, the root mean square (RMS) error between optical probe and MRT measurements was 0.02°C with field sensor correction. In vivo, the low SAR scan returned a precision in temperature change measurement with field monitoring and motion compensation of 0.05°C. The 20-minutes maximum SAR scan returned a temperature rise throughout the inner-brain in the range of 0-0.2°C. Brain periphery remained too sensitive with respect to motion to lead to equally conclusive results. Sub-degree temperature rise in the inner human brain was characterized experimentally throughout RF exposure. Potential applications include improvement of human thermal models and revision of safety margins.

Development of a battery management system with flying capacitor‐type multiport converter in the discontinuous current mode

AbstractThis paper proposes a multiport converter based on a flying capacitor converter (FCC) topology for use in a battery management system. The proposed circuit operates in discontinuous current mode (DCM) and pulse frequency modulation (PFM) in order to reduce inductor volume. The circuit achieves load fluctuation compensation and maximum power point tracking (MPPT) of the photovoltaic (PV) system by deciding duty ratio based on load current and PV output current. According to the experimental results, an efficiency of more than 95.8% was achieved under all operation conditions. In addition, the maximum efficiency reached 98.8% at the rated load (750 W). Furthermore, the inductor volume reduced by 85.5% compared to that of the conventional circuit (CCM) using two inductors.

Transient and disturbed propeller load compensation in hybrid propulsion using propeller estimator and predictive control

We address the design of a predictive power-split management system for the transient and fluctuating propeller load sharing. Modeling of the power system was carried out based on experimental data gathered from the hybrid plant and on first principles for the diesel engine behavior and battery charging. Propulsion plant and wave disturbance models are employed to simulate realistic marine load application that affects the powerplant operation. A propeller observer is developed to provide the propeller law parameter to the controller, in order to perform load estimation and prediction based on shaft speed elevation. A Nonlinear Model Predictive Controller (NMPC) is designed for the optimal transient power-split problem of a hybrid diesel-electric marine propulsion plant. The NMPC scheme directly controls the torque output of the diesel engine and the electric motor generator ensuring that certain constraints concerning the system overloading are met, avoiding fast accelerations, and load fluctuations of the diesel engine that affect engine performance. The control system was experimentally tested in real-time operation in a physical testbed. Results showed that controller rejected successfully load disturbances and maintained the desired rotational speed of the powertrain as well as the desirable state of charge in battery within the power plant limits, achieving smooth power transitions and compensation of power fluctuations of the diesel engine.

Проточные батареи на основе органических редокс-систем для крупномасштабного хранения электрической энергии

Redox flow battery technology has been known since the 1970s. Their low specific characteristics have been of interest for a long time. Practical interest has arisen in recent decades because of the intensive development of alternative energy (such as solar and wind) and the regulation of peak loads in industrial networks. It turned out that large-scale energy storage systems used for compensation of fluctuations in the generation of energy by the sun and the wind, while producing electric vehicles and power supply systems for large households, are more profitable when they work on flow redox batteries. Firstly, they are easily scalable, and secondly, the energy stored in such batteries is cheap. Since the expansion of the scope of practical use of flow batteries has taken place in recent years, researchers continue to work on increasing the economic efficiency of flow batteries and on the search for more efficient redox systems. One of these areas is the use of cheaper redox systems of organic nature, in particular, quinone, anthraquinone and their analogs. Their high water solubility, well-separated oxidation-reduction potentials, which practically eliminate water splitting, their stability, safety, and low cost on a scale of mass production are the most important characteristics for new aqueous organic electrolytes. So far, organic redox flow batteries are still inferior to vanadium and other inorganic redox batteries in terms of their operational parameters. This drawback hinders their development on industrial scale. However, the results shown in this review can help scientists to improve them and commercialize in the future.

Multi-time scale coordinated optimization of an energy hub in the integrated energy system with multi-type energy storage systems

To comprehensively consider the impact of uncertainties of variable energy resources (VERs) and load demands on the scheduling plans, the paper proposes a multi-time scale coordinated optimization (MTSCO) method of the energy hub (EH) with multi-energy flows and multi-type energy storage systems (MESSs). The MTSCO involves with global optimization of day-ahead economic dispatch (DAED), local intra-day receding-horizon optimization (IDRHO) and real-time adjustment (RTA). DAED formulates the 24-period output of controllable devices integrated in EH through minimizing its operation cost of a single day. Following the formulated DAED plan, IDRHO minimizes the sum of energy purchase cost and MESSs’ penalty cost within every 15 min. Further, RTA provides real-time feedback to IDRHO and minimizes the total adjustment amount of all controllable devices every 5 min. The simulation results indicate that the proposed multi-time scale dispatching and MESSs enable to promote the EH economy, acquire better dispatching solution aiming at uncertainties of VERs and varying load demands and alleviate the grid’s compensation for fluctuation.