Input Power Changes Research Articles

Free-surface-induced ground effect for flapping swimmers

Numerous flying and swimming creatures use the ground effect to boost their propulsive performance, with the ‘ground’ referring to either a solid boundary or a free surface. While our knowledge of how a solid boundary affects biolocomotion is relatively comprehensive, the ground effect of a free surface is not fully understood. To address this limitation, we conduct a numerical investigation on the propulsion performance of a flapping plate under a free surface, subject to a range of control parameters. When the Froude number ( $Fr$ ) is very low (i.e. little surface deformation), the effects of a free surface are similar to those of a solid boundary, with enhanced thrust and input power but little change in efficiency. However, as $Fr$ increases (i.e. more surface deformation), our results reveal an optimal $Fr$ of approximately 0.6, where the free surface induces a more streamlined flow around the flapping plate, effectively reducing the added mass. This results in a significant decrease in input power and greatly enhanced efficiency.

A Compact Broadband Rectifier Based on Coupled Transmission Line for Wireless Power Transfer

Wireless Power Transfer (WPT) can effectively solve the problem of autonomous power supply for low-power devices. Rectifier is the key component in WPT technology. In this paper, a novel impedance matching network for the broadband rectifier is proposed. This impedance matching network compensates for the diode impedance and reduces its impedance change when the frequency or input power changes. The passive boosting mechanism utilizing coupled transmission lines (CTLs) improves the power conversion efficiency (PCE) of the diode in the low power region. The structure is especially optimized for low-power device applications. For validation, a broadband rectifier operating at 1.9–3 GHz is fabricated and measured. The structure fabricated on the Rogers 4003 substrate with a thickness of 1.508 mm and the diode is HSMS2860. The DC voltage Vout on the load (RL=1300 Ω) was measured. The results show that at 0 dBm, the PCE keeps more than 60% at 1.98–3 GHz. The peak PCE of 79.6% is obtained at 4 dBm. The compact size of the broadband rectifier is 19 mm × 21 mm. This broadband rectifier for low input power ranges can be applied to WPT technology.

Analysis of Effect of Input Power and RF Optical Signal Rate on Optical Communication System with OOK-NRZ Modulation

This study analyzed optical and RF signals in optical communication systems using the On-Off Keying Non-Return to Zero (OOK-NRZ) modulation method and the direct-detection receiver model with PIN photodiodes. In this study, a simulation was carried out using Python software. Changes in optical modulation input power and Symbol rate (Rs) were explored to understand their effect on signal characteristics. Models of ideal photodiodes (noiseless) and noisy photodiodes (considering thermal noise, shot noise, and bandwidth constraints) were used to compare receiver signals. The eye diagram analysis was employed to visualize receiver signal variation in a given time span. The results of this analysis provide a better understanding of the influence of changes in input power and symbol rate on optical communication systems through the OOK-NRZ method and insight into the characteristics of the receiving signal under realistic conditions. This study is able to provide guidance for the design and evaluation of optical communication systems using OOK-NRZ modulation and direct detection receivers.

Compact high-efficiency energy harvesting positive and negative DC supplies voltage for battery-less CMOS receiver

In this paper, novel compact high-efficiency multi-band rectifiers that supply positive and negative output voltages are demonstrated for energy harvesting applications. The proposed voltage doubler circuits are used as real DC voltage supplies of radio frequency mm-wave CMOS receivers. Operating multi-band rectifiers have a complicated structure that required more resonance networks to force the rectifier to work in multi-band. Novel series and parallel resonance networks are implemented to force the rectifier to operate in dual-band at frequencies of 850 and 1400 MHz. The proposed resonance network eliminates the Schottky diode impedance variation as the input power or frequency changes and supports the impedance matching and minimizes the insertion loss. A novel high-quality sine-shape micro-strip inductor that obtains a quality factor above 65 over the frequency band from 200 to 1400 MHz and inductance equal to 14 ± 2 nH is designed to improve efficiency and enhance performance at low power levels. The first suggested RF voltage doubler rectifier with series resonance feedback between the input and cathode of the diode and parallel resonance operates at two frequency bands of 850 and 1400 MHz and obtains a peak conversion efficiency of 59%, a saturated output DC voltage is 2.5 V, and the conversion efficiency is 40% at RF-input-power of − 10 dBm. This voltage doubler achieves the required DC supply parameter (1.1 V and 450 uA) for biasing the mm-wave receiver at an RF input power of 0 dBm. Otherwise, the second suggested negative voltage rectifier has a maximum simulated conversion efficiency of 65%, saturated negative DC-voltage is − 3.5 V, and the conversion efficiency is 45% at an RF input power of − 10 dBm. The negative voltage rectifier obtains DC supply parameters (− 0.5 V and no current condition used for a gate bias) at − 10 dBm input power.

Quasi-periodic spectro-temporal pulse breathing in a femtosecond-pumped tellurite graded-index multimode fiber.

We report on the multidimensional characterization of femtosecond pulse nonlinear dynamics in a tellurite glass graded-index multimode fiber. We observed novel multimode dynamics of a quasi-periodic pulse breathing which manifests as a recurrent spectral and temporal compression and elongation enabled by an input power change. This effect can be assigned to the power dependent modification of the distribution of excited modes, which in turn modifies the efficiency of involved nonlinear effects. Our results provide indirect evidence of periodic nonlinear mode coupling occurring in graded-index multimode fibers thanks to the modal four-wave-mixing phase-matched via Kerr-induced dynamic index grating.

Driving system for Mach-Zehnder electro-optic modulators in microwave photonics.

In order to obtain a modulation signal with high bandwidth and highly stable output power without distortion, an electro-optic modulator driving system with quick response to the input signal is designed in this paper. The system mainly includes three parts: power supply module, microwave signal generation module, and automatic gain control (AGC) module. The power supply module provides appropriate voltage and current for other two modules. The microwave signal generation module is used to generate microwave signals. The AGC module adopts the digital AGC control structure and the PID control principle to achieve stable control of the output power of the microwave signal. The hardware is developed, and the software algorithm is integrated into the driving system to verify the effectiveness and stability. The experimental results show that the bandwidth of the AGC module reaches 20 GHz. The proposed AGC module can effectively stabilize the output power of the microwave signal at 10 dBm with fluctuations less than ±1.5 dB, and its stability is improved by 74.95% compared to existing instrument. When the input power changes at 10 KHz, the system can still achieve stable control performance and has exhibited excellent dynamic response characteristics.

Application-based catalytic methanation of steelworks gases under dynamic operating conditions

This paper presents a real and application-based scenario for a dynamically driven catalytic methanation unit, using off-gases from an integrated steel mill as input. Several parameters are subject to dynamic changes during the standard production of steel, such as the available amount and composition of the accumulating process gases, the temperature and operating pressure as well as their periodicity. In addition, the available amount of hydrogen can vary depending on the available fluctuating renewable energy for the installed electrolyzer. Analysis of operating parameters and process routes in steelmaking revealed that among many theoretically possible modes of driving a dynamic methanation unit, which are defined in the literature, there is only one realistic application-based scenario. The definition of this case is supported by experiments performed with a three-stage methanation setup in lab-scale. This experimental campaign covered real cases with dynamic flow rates, adjusting the amount of blast furnace and converter gases based on high variations in the availability of hydrogen. It was possible to achieve very stable product gas compositions, even though load changes in gas input power up to 64% in the range of one to 120 min were executed. The dynamic variations did not result in any additional catalyst deactivation through the whole experimental campaign.

Simulation of millimeter-sized microwave plasma discharge generator under various conditions

A microwave plasma generator (MPG) of a sub-millimeter scale might be suitable for biomedical applications. However, there are still many unknowns regarding the MPG discharge behavior at this scale and specific conditions. A two-dimensional MPG model at the millimeter scale and its simulation and relative calculation in the COMSOL Multiphysics software are presented. A MPG filled with argon and helium is simulated, respectively. The frequency of a microwave source of about 5 GHz is considered. The number density and temperature of electrons as well as chemical composition are obtained at different power and pressure conditions. The electron density peaks slightly downstream of the crossing point, and the electron density is slightly asymmetrically in the y-plane due to the fact that the electromagnetic waves are absorbed asymmetrically. The electron temperature is relatively low everywhere, in part, due to the high operating pressure. The electron temperature peaks directly underneath the wave guide where the wave is absorbed. The electron density increases with the increase in the internal pressure and the input power of the MPG, the electron temperature decreases with the increase in the internal pressure of the MPG, but the electron temperature cannot be affected by the input power change of MPG. The amount of excited Ar+ and Ars (metastable atom) increases with the increase in the input power and pressure of MPG, but the amount of excited Ar almost remained unchanged. In addition, the amount of excited He almost remained unchanged, while the amount of excited He+, Hes (metastable atom), and He2+ increased with the increase in the input power and pressure of MPG. The simulation results of this model are thus informative for understanding the physical characteristics of millimeter-sized MPG, and it will provide a solid basis for the future development of such hardware in small plasma capsules for cancer therapy.

Experimental and Analytical Study of a Proton Exchange Membrane Electrolyser Integrated with Thermal Energy Storage for Performance Enhancement

To peak carbon dioxide emissions and carbon neutrality, hydrogen energy plays a pivotal role in the energy system dominated by wind power and solar power. The proton exchange membrane (PEM) electrolytic hydrogen production technology has advantages of higher current density, higher hydrogen purity, higher load flexibility, and balanced grid load, becoming one of effective ways to consume renewable energy. Experimental analysis finds that the present PEM electrolyser cannot maintain a stable operating temperature as the input power changes; the polarization curve would distort with the change of temperature. This work proposes a PEM electrolyser coupled with the thermal energy storage device to meet power fluctuation and frequent start and stop caused by renewable resources. Through the involvement of the thermal storage device, electrolytic system is able to operate quickly and persistently in an efficient condition. The coupled system effectively reduces energy consumption in the process of start-stop or load changing, which can effectively adapt to the power fluctuation and frequent start and stop caused by renewable energy.

Image processing based fault classification in power systems with classical and intelligent techniques

This paper is devoted to develop interest of power system engineers in learning basic concepts of image processing and consequently using deep networks to solve problems of complex power system networks. To this end, we study fault classification in a power system through automation of equal area (EAC) criterion. By considering EAC graphs as images and using classical image processing techniques, we successfully distinguish between different transient conditions including sudden change of input power as well as short circuit at the sending end and middle points of a single and double circuit transmission lines. In addition to classification, some parameters are also determined from EAC images such as initial rotor angle, clearing angle, and maximum rotor angle. Further, the use of deep networks is introduced to perform the same task of fault classification and a comparison is drawn with multilayer perceptron neural networks. Developed algorithms are tested in MATLAB as well as Pytorch environments.

Design and Control of Ultra-High-Speed Sensorless Drive with Two-Input Power Source for Portable Consumer Electronics

The convenience and usability of portable consumer electronics that require a motor, such as vacuum cleaners and hair dryers, will be greatly improved if both ac and dc two-input power sources can be used. The dc input power is mostly composed of a dc battery, and single-phase voltage is used as ac input power. A converter system capable of converting ac and dc voltage with control technology is required to supply the voltage for motor driving to apply both ac and dc input to the product. Because a limited number of batteries are used to decrease the weight and size of portable products, a system such as a dc converter is necessary to supply the voltage required to operate the motor and to keep the voltage fluctuation according to the usage time constant. When ac power is used in the product, a voltage drop system that can step down the ac voltage to supply voltage to the dc link is necessary to supply the voltage required to operate the motor to the dc-link. In addition, it is important to reduce the size of the system through ultra-high-speed motor operation by increasing the rotation speed because portable consumer electronics that include a motor drive should be light and portable. This paper proposed a system that can supply a stable dc-link voltage required for ultra-high-speed motor control by applying a phase control method to the ac input side and a dc boost converter to the dc input side. Furthermore, the 1-shunt sensorless method was applied to the inverter for ultra-high-speed motor design and ultra-high-speed motor control system that contributes to product miniaturization and material cost reduction, experimental verification. The ultra-high-speed motor driving evaluation under ac and dc input power conditions and the conversion to dc power input when ac power interrupt occurs were performed to more stably verify the system according to the input power change.

Research on nonlinear dynamic performance of the central bevel gear transmission system in aero-engine with complex excitation

For the requirement of the vibration control and fault diagnosis of the central bevel gear transmission system in an aero-engine, this paper proposes a 12-degree-of-freedom dynamic model for the first time in order to investigate nonlinear dynamic behavior of the central bevel gear transmission system considering the internal and external excitations. The dynamic model is developed by the use of lumped parameter modeling. Time-varying meshing stiffness, gear backlash and gear transmission error are included in the internal excitations, the input power of the central bevel gear transmission system, the speed fluctuation of the driven shaft and the high-pressure rotor unbalance excitation are included in the complex external excitations. Using the bifurcation diagram, the largest Lyapunov exponent, time domain diagram, frequency domain diagram, phase diagram and Poincaré map, the effects of input power change, driven shaft speed fluctuation excitation and high-pressure rotor unbalance excitation on the complex nonlinear dynamic behavior of the central bevel gear transmission system are analyzed. The increase of input power, reduction of speed fluctuation and control of high-pressure rotor unbalance are beneficial to expand the stable area of the system.

Analysis and Simulation of a Typical Two Winding Transformer

In this study, we show how input power, terminal voltage, and efficiency changes as a function of load current. In this situation, we've chosen three scenarios they are- Coil connection in Parallel Coil connection in Series Two Winding Transformer Here, we have connected the coils of a single-phase transformer in series and parallel, then observed the transformer's loading as an autotransformer and as a two-winding transformer. It is essential to comprehend the instant polarities of the secondary terminals in relation to the primary in order to properly connect the winding.

Research on VSG Frequency Characteristics and Energy Storage Device Capacity and Charge-Discharge Characteristics Based on Feedforward Branch

Renewable energy is connected to the grid through the inverter, which in turn reduces the inertia and stability of the power grid itself. The traditional grid-connected inverter does not have the function of voltage regulation and frequency regulation and can therefore no longer adapt to the new development. The virtual synchronous generator (VSG) has the function of voltage regulation and frequency regulation, which has more prominent advantages than traditional inverters. Based on the principle of VSG, the relationship between the frequency characteristics and the energy storage capacity of the feedforward branch-based virtual synchronous machine (FVSG) is derived when the input power and grid frequency change. Reveal the relationship between the virtual inertia coefficient, damping coefficient, and frequency characteristics of VSG and energy storage capacity. An energy storage configuration method that meets the requirements of frequency variation characteristics is proposed. A mathematical model is established, and the Matlab/Simulink simulation software is used for modeling. The simulation results verify the relationship between the inertia coefficient, damping coefficient, and energy storage demand of the FVSG.

Power decoupling control of DFIG rotor‐side PWM converter based on auto‐disturbance rejection control

AbstractIn this paper, double PWM converter AC excitation system of the variable speed constant frequency doubly fed induction generator (DFIG) for wind power generation is taken as the research object. At present, most vector control systems of rotor‐side PWM converter adopt feedforward compensation to realize the purpose of power decoupling control. The decoupling effect is greatly affected by the power changes. A power decoupling control strategy based on auto‐disturbance rejection control (ADRC) is proposed. The decoupling control between active power and reactive power is realized by observing the coupling term and the total disturbance of the d‐axis and q‐axis components of the stator current and the stator voltage with the extended state observer and compensating. Simulation analysis and experimental test show that, on the basis of vector transformation, the rotor‐side PWM converter power decoupling control based on ADRC has a small overshoot and fast dynamic response when tracking the change of wind turbine input power, which can achieve the decoupling control between active power and reactive power well. The system has strong robustness and adaptability.

Power distribution method for a parallel hydraulic-pneumatic hybrid system using a piecewise function

The Benedict-Webb-Rubin model or the ideal gas equation of state alone cannot accurately describe the load model of a parallel hydraulic-pneumatic hybrid system. This paper proposes a load model of the energy recovery system based on a piecewise function considering the load components switching problem under high energy regenerative braking and cruise charging conditions. This model can express the influence of the pre-charge pressure of the hydraulic accumulator and the air compressor speed on the system load power. This is accomplished by detecting the hydraulic accumulator state of charge, the transient temperature of nitrogen, and the transient temperature of the air in the reservoir. The load power of the energy recovery system can be estimated under various working conditions and used to guide the adjustment of the hydraulic pump/motor displacement to adjust the power distribution of the energy recovery system. This can solve the problem of ineffective power distribution and overspeed conditions, as well as fluctuation of the air compressor operation caused by changes in mechanical input power. The method proposed in this paper provides a new technical approach for the configuration of parallel hydraulic-pneumatic hybrid power systems.

Broadband High-Efficiency RF Rectifier With a Cross-Shaped Match Stub of Two One-Eighth-Wavelength Transmission Lines

This letter presents a broadband rectifier that can be applied to harvest ambient radio frequency (RF) energy. The matching network consists of three-stage transmission lines. A cross-shaped match stub of two one-eighth-wavelength transmission lines is proposed to realize efficient and broadband impedance compression. The proposed circuit has been optimized and manufactured, and the measured results show that the rectifier can achieve high RF-to-dc conversion efficiency and broadband characteristics. The simulation and measured results were basically consistent. When the input power is 8 dBm and the terminal load is 1.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula> , a bandwidth of 81% (1–2.35 GHz) with an efficiency above 50% and a bandwidth 69% (1–2.05 GHz) with an efficiency above 60% are achieved. The highest conversion efficiency of the test circuit is up to 73.2% at an input power of 8 dBm. Moreover, when the input power changes from 1 to 11 dBm, the efficiency of the rectifier circuit is always above 50%.

Study on linearization of Ka-band wideband traveling-wave tube amplifer

Linearizer is a key component in the millimeter-wave communication system, it plays an important role in improving the linearity performance of amplifier and communication quality. At present, the development of traveling-wave tube amplifier (TWTA) linearization technology cannot meet the application requirements of communication technology, therefore, the research of linearization technology is very important. In this paper we propose a kind of a new wide-band analog pre-distortion structure used to improve the nonlinear characteristics of Ka-band TWTA. The simulation results show that when the input power changes from −20 to 10 dBm in the frequency range of 26−30 GHz, the gain expansion of the linearizer is greater than 5.08 dB, and the phase expansion exceeds 64.81°. The linearizer and the TWTA are cascaeded for testing. The test results show that the gain compression and phase compression of center frequence is less than 3.12 dB and 2.31° respectively, and the third-order intermodulation (IMD3) improves significantly.

Wide-Range Rectifier for Wireless Power Transfer Based on Power Compensation

In this letter, a rectifier based on the reflected power compensation network (RPCN) is designed, which enables the rectifier to maintain high efficiency over a wide range of incident power and load impedance. The proposed rectifier mainly includes a hybrid coupler, phase shift units, matching networks, Dickson circuits, and resistive loads. By integrating the hybrid coupler with the phase shifter, the rectifier can reduce the impact of the non-linear effect of the diode caused by the input power and load impedance change. Through theoretical analysis and processing validation, this rectifier can achieve a power conversion efficiency (PCE) over 60% from −2 to 15 dBm; meanwhile, it can maintain a relatively high PCE over 50% when load range varies from 8 to 97 $\text{k}\Omega $ under the incident power Pin = 7.5 dBm. The rectifier structure fully meets the power supply requirements when applied to the wireless sensor nodes.

Modelling and analysis of extra vessel electro magnetic pump for a small modular lead-bismuth fast reactor

The model of the EVEMP (Extra Vessel Electro Magnetic Pump) with a mass flow of 5000 kg/s and a developed pressure of 15000 Pa in the 350 °C operating temperature has many advantages as a coolant circulation pump for the Micro URANUS.Micro URANUS is an SMR with a rated output of 60 MWt which is abbreviated as ‘Micro Ubiquitous, Rugged, Accident-forgiving, Nonproliferating, and Ultra-lasting Sustainer’. Micro URANUS has a six-angle grid core as a pool type fast reactor using LBE, which is chemically stable as a coolant and can achieve a fast neutron spectrum. It is necessary to utilize natural circulation for the reactor to run without pumps even during normal operation, as well as accident situations. However, natural circulation was calculated to be only possible in the current design up to an output of 30 MWt as the size of the power source is very small compared to that given by the pump. In order to install pumps for enhanced output in Micro URANUS with these very small sizes and special structures, installation of EVEMP using the concept of an electromagnetic pump that is easy to free up space and operates in contactless ways is essential, and this is used to design enhanced power up to 60 MWt. The relationship of performances and design factors are analysed for the optimization of the EVEMP, derives data such as P-Q characteristics, input power changes, and efficiency changes depending on the different input power conditions of the EVEMP are predicted.