Power Hysteresis Research Articles

Magnetic properties and magnetocaloric effect of Borophyne structure: A Monte Carlo study

This study delves into the magnetocaloric effect of the Borophyne structure, employing a Monte Carlo method with a mixed spin composition of σ = 3/2 and S = 1. Each site within the structure is occupied by a spin, with pairwise interactions governed by exchange coupling parameters JSS, Jσσ, and JSσ, the interaction between two neighboring atoms is considered an antiferromagnetic for JSσ < 0 or ferromagnetic for JSσ > 0. The investigation focuses on determining magnetic entropy changes, relative cooling power, adiabatic temperature, and magnetic hysteresis cycles for a range of magnetic parameters. The results obtained from this study demonstrate that the structure under investigation exhibits highly intriguing properties. Through our simulations and analysis, we have uncovered a range of characteristics that highlight the unique behavior of the system.

A power-speed hierarchical optimization framework of diesel/battery/supercapacitor vehicular hybrid propulsion systems

Ships' fuel consumption has emerged as the primary contributor to energy use and pollution in maritime transportation. This paper presents a novel marine vehicular hybrid propulsion system (VHPS) comprising a diesel generator and a hybrid energy storage device (HESD) that integrates batteries and supercapacitors (SCs). However, variations in the power and energy characteristics of the three sources result in heightened intricacies in energy management and system control. Therefore, a power-speed hierarchical optimization framework is proposed to optimize the fuel consumption and stability of the system. Within this framework, an AECMS-GRNN energy management strategy (EMS) is proposed to reduce the fuel consumption of VHPS. Based on the AECMS-GRNN strategy's power distribution results, a multi-zone target speed power hysteresis control strategy is proposed to ensure that the speed of the diesel generator is stable, so as to improve the stability of the system. Finally, an experimental hardware-in-the-loop (HIL) platform is employed to validate the proposed framework's performance. From experimental results, the AECMS-GRNN strategy demonstrates precise load prediction with a minimal predictive ARMSE value of 1.5886 kW. Compared with a conventional rule-based (RB) strategy, AECMS-GRNN strategy can reduce the fuel consumption by 0.077 kg, about 7.7%. Additionally, the proposed speed control strategy ensures a stable speed for the DG, contributing to the system's consistent power supply.

Hybrid Data-Model Predictive Control for Enabling Participation of Renewables in Regulating Reserves Service

A long-horizon hybrid data-model predictive direct power control (HD-MPDPC) scheme is proposed. The hybrid control scheme is for grid-side power electronic converters (PEC) in grid-connected renewable energy sources (RES). Computational burden of conventional MPDPC is alleviated by reducing the number of candidate voltage vectors to be examined in the cost function. This is achieved by employing data-driven forecast of RES output power to identify and eliminate the voltage vectors that do not counteract active and reactive power errors appropriately. RES power is forecasted using recurrent neural networks. The method for eliminating voltage vector candidates is inspired from direct power control, where output of active and reactive power hysteresis controllers along with the sector in which grid voltage vector lies are used to determine the switching states of the grid-side PEC. Thanks to reduced computational complexity, the hybrid predictive control scheme dispatches RES power more reliably over long horizons. This in turn enables RES as a regulating reserves service provider in power systems. Hardware-in-the-loop studies of a grid-connected wave energy conversion system verify reduced computational complexity of HD-MPDPC and its effectiveness in controlling RES output power over long horizons.

Self-Powered Single-Inductor Rectifier-Less SSHI Array Interface With the MPPT Technique for Piezoelectric Energy Harvesting

Piezoelectric energy harvester (PEH) arrays are practical solutions to the low and unreliable power output of a single PEH. However, most PEH circuits are developed for addressing the one-channel ac input from a single PEH. In this article, an extensible rectifier-less synchronized switch harvesting on inductor (ReL-SSHI) array interface with the maximal power point tracking (MPPT) function to manage the multiple ac inputs from the PEH arrays is designed. The ac–dc conversion is performed by the ReL-SSHI topology with passive peak switches featured with self-powered characteristic and fast cold-start. Only one shared inductor is employed, greatly reducing the circuit volume and cost. The MPPT module for each channel is implemented by a simple envelope detector and an ultra-low power hysteresis controller and achieves continuous energy extraction by adapting the fractional normal-operation voltage method. A developed discrete array interface able to handle three PEHs effectively executes the MPPT for each channel with the uphill and downhill response speeds of 2.0 and 7.1 V/s, and a maximal MPPT efficiency of 97.1%. This circuit boosts the power output by 485% compared with that by the traditional full-bridge rectifier, around 33% higher than that from existing synchronous electric charge extraction array interfaces.

Varied performance of printable mesoscopic perovskite solar cells by the non-stoichiometric precursor

Halide perovskite semiconductors such as MAPbI3 always fluctuate around their stoichiometric compositions due to the weighing or annealing, which causes performance variation of related devices. Here, we investigate the comprehensive impact of non-stoichiometric MAPbI3 precursor on the performance including power conversion efficiency (PCE), hysteresis, and stability of printable mesoscopic perovskite solar cells (p-MPSCs). Excess MAI improves PCE, suppresses hysteresis, and enhances stability by promoting hole transport and passivating defects evaluated by a designed mesoporous space-charge-limited-current device, while excess PbI2 impairs device performance. Replacing excess MAI with other monovalent cation halide salts including guanidinium iodide (GUAI), 2-phenylethylamine hydroiodide (PEAI) and rubidium iodide (RbI) further improves the device PCE to 17.02% and minimizes the hysteresis. Our work reveals that making monovalent cation halide salts such as MAI rather than PbI2 excessive is positive for the comprehensive performance enhancement of PSCs and developing more suitable salt substitution will benefit industrializing PSCs.

Junction Temperature Optimization Based Compensation Strategy of Modular Multilevel Railway Power Conditioner

The modular multilevel railway power conditioner (MM-RPC) can effectively improve the power quality of the railway power grid. However, since the operating conditions of MM-RPC frequently vary with the traction load, the junction temperatures of semiconductor devices fluctuate very drastically. Severe junction temperature swings can easily affect the service lifetime and reliability of the MM-RPC. In this article, a power hysteresis based on incomplete compensation control strategy is proposed. The proposed control can effectively reduce junction temperature fluctuations under complex mission profiles and increase the overall life of the system while meeting the power quality requirements. Furthermore, the effectiveness of the proposed control is verified in MATLAB/PLECS electrothermal cosimulation under a section of the load curve of the Beijing–Shanghai high-speed railway traction substation. Finally, the experimental thermal platform is built to validate the effectiveness of the proposed control strategy.

Magnetocaloric effects and magnetic properties in A-site cation-ordered chromate LiM(Ga and In)Cr4O8 spinels

Magnetic properties of LiGaCr4O8 and LiInCr4O8 compounds in spinel structure are investigated by Monte Carlo study (MCS). The magnetocaloric effect and its correlation with structure and magnetism in the two systems have been studied using the MCS for two systems. The magnetization, magnetic susceptibly, magnetic entropy, relative cooling power (RCP) and magnetic hysteresis cycle are found. The two systems show a magnetocaloric effect (MCE) at the magnetic ordering temperature and short and long orders a high and low temperature, respectively. The values of relative cooling power and maximum of magnetic entropy change increase with increasing the values of extremal magnetic field.

Unitized regenerative proton exchange membrane fuel cell system for renewable power and hydrogen generation: Modelling, simulation, and a case study

Unitized regenerative proton exchange membrane fuel cell (URPEMFC) performs the functions of an electrolyser and a fuel cell. Currently, power hysteresis effect (PHE) is a key technological challenge for the URPEMFC because it reduces the efficiency of the system as it switches from electrolyser mode to fuel cell mode and vice versa. Here, a modelling and simulation approach is used to investigate the PHE based on its thermodynamic and electrochemical attributes. URPEMFC model was validated against an experimental study and then used for parametric studies. The results indicate that the PHE occurs when the number of cells is 1, 5 and 10. Moreover, an increase in the lost internal current density and total resistance resulted in an increase in overpotentials of the system. Although the theoretical thermodynamic efficiency of a URPEMFC is about 68.86%, the current study predicted an efficiency of 44% for a stack of 10 cells at current density of 0.5 A cm−2. A case study of an integrated photovoltaic-URPEMFC system for power generation using actual meteorological data is also presented. If optimised, URPEMFC can be applied with renewable energy sources for power-to-gas technologies, power-to-power technologies, hydrogen filling stations or distributed hybrid energy systems.

Modeling of Abnormal Hysteresis in CsPbBr3 based Perovskite Solar Cells

Perovskite solar cells are emerging photovoltaic devices with PCE of above 25%. Perovskite are suitable light absorber materials in solar cells with excellent properties like appropriate band gap energy, long carrier lifetime and diffusion length, and high extinction coefficient. Simulation study is an important technique to understand working mechanisms of perovskites solar cells. The study would help develop efficient, stable PSCs experimentally. In this study, modeling of perovskite solar cell was carried out through Setfos software. The optimization of different parameters of layer structure of solar cell would help to achieve maximum light absorption in the perovskite layer of solar cell. Simulation study is based drift-diffusion model to study the different parameters of perovskite solar cell. Hysteresis is one of the factors in the perovskite solar cell which may influence the device performance. The measurement of abnormal hysteresis can be done by current-voltage curve during backward scan during simulation study. In backward scan, the measurement starts from biasing voltage higher than open circuit voltage and sweep to voltage below zero. The numerical simulation used to study the various parameters like open circuit voltage, short circuit current, fill factor, power conversion efficiency and hysteresis. The simulation results would help to understand the photophysics of solar cell physics which would help to fabricate highly efficient and stable perovskite solar cells experimentally.

Cortical gamma-band resonance preferentially transmits coherent input.

SUMMARYSynchronization has been implicated in neuronal communication, but causal evidence remains indirect. We use optogenetics to generate depolarizing currents in pyramidal neurons of the cat visual cortex, emulating excitatory synaptic inputs under precise temporal control, while measuring spike output. The cortex transforms constant excitation into strong gamma-band synchronization, revealing the well-known cortical resonance. Increasing excitation with ramps increases the strength and frequency of synchronization. Slow, symmetric excitation profiles reveal hysteresis of power and frequency. White-noise input sequences enable causal analysis of network transmission, establishing that the cortical gamma-band resonance preferentially transmits coherent input components. Models composed of recurrently coupled excitatory and inhibitory units uncover a crucial role of feedback inhibition and suggest that hysteresis can arise through spike-frequency adaptation. The presented approach provides a powerful means to investigate the resonance properties of local circuits and probe how these properties transform input and shape transmission.

Thermoelectric power hysteresis in semi-parabolic quantum well

The influence of semi-parabolic surface potential on quantum well thermoelectric power is investigated. The thermoelectric power dependence on the Fermi level and quantum well parameters is determined. It is shown that semi-parabolic quantum well thermoelectric power exhibits hysteresis features. The hysteresic loops and sign change in thermoelectric power dependence on the surface potential are ascribed to properties of electrons at the edges and electron localization.

A synchronous defect passivation strategy for constructing high-performance and stable planar perovskite solar cells

The diverse defects within perovskite film, electron transport layer (ETL) and their interface greatly impair the power conversion efficiency (PCE), hysteresis and stability of perovskite solar cells (PSCs). Herein, we propose a synchronous defect passivation strategy by introducing chelating agent containing movable alkali metal cations, i.e. sodium tartrate (STA)/potassium sodium tartrate (PSTA) into SnO2 aqueous colloidal dispersions to realize the efficient regulation of ETL, perovskite layer and their interface properties. That is, the chelating function and existence of alkali metal ions in additives lead to uniform, less defective and highly conductive SnO2 ETLs, which provides outstanding platforms for depositing perovskite films with high-quality crystallinity to improve the interfacial charge transfer. In particular, a part of Na+ and K+ ions of additives can enter into perovskite film through thermal diffusion and passivate the defects by coordinating with under-coordinated halides via ionic interactions or electrostatic adsorption on the negative charged defects at surface and grain boundaries. Such synchronous optimization for ETLs, perovskite and their interface enables the realization of high PCEs of 20.38% and 21.14% with reduced hysteresis and improved stability for STA-SnO2 and PSTA-SnO2 based PSCs, respectively. This work greatly simplifies the defect passivation process and provides a promising low-cost technique for large-scale manufacturing efficient and stable planar PSCs.

Fast terminal sliding mode control-based direct power control for single-stage single-phase PV system

Today, grid-connected photovoltaic systems have gained widespread penetration among renewable energy systems. For low power applications, a single-phase inverter with less power converter is a good compromise for high efficiency. The control must make it possible to extract the maximum power from the photovoltaic modules, ensure good dynamic performance for active and reactive power injection, ensure power quality, and reject disturbances and parameter mismatch. Besides, the controllers of the grid and PV sides should be coordinated. In this study, a fast terminal sliding mode control combined with Direct Power Control is proposed. Thanks to the two-cascaded control loops, simulations and experimental results with a 1 kW test bench have proven the proposal’s effectiveness in terms of dynamic performances and robustness to irradiance variations. Comparison with deadbeat-Direct Power Control, predictive control, and power hysteresis control shows that our proposal leads to lower Total Harmonic Distortion (3,5%) for the electrical grid’s current and lower time response (one-tenth of half the grid cycle).

Light-induced degradation and self-healing inside CH3NH3PbI3-based solar cells

CH3NH3PbI3 (MAPbI3)-based perovskite solar cells (PSCs) with special hole and electron transport layers (HTL and ETL) were prepared to study their light-induced degradation. Obvious degradation was observed under initial light exposure not only at the device level but also at the film morphology and electronic structure level. Device performance parameters, such as short-circuit current (JSC), power conversion efficiency, fill factor, and hysteresis effect, were aggravated with an initial light exposure of less than ∼8 h at 1 sun intensity. Meanwhile, the deteriorated crystallinity and electronic structure of the MAPbI3 film were also detected with x-ray diffraction, ultraviolet photoelectron spectroscopy, and UV-Visible absorption spectroscopy. The observed degradation is rationally related to the light-induced decomposition of MAPbI3. However, the degradation can be partly recovered with the following light exposure resulting in self-healing of the devices and MAPbI3 films. The self-healing behavior should be ascribed to the conversion of decomposition products back to MAPbI3, because the intermediates are wrapped tightly in the photoactive layer by the compact coverlayers of HTLs and ETLs and some reversible reactions occur consequently. The mechanism of self-healing is discussed by introducing the trapped states derived from ion migration. The PSCs prepared here imply a good optical stability and thus a good performance facilitated by tight wrapping of the active MAPbI3.

Raman-induced pulse destabilization and bistability in an all-normal dispersion oscillator.

We report the experimental study of spectral modulations induced by a stimulated Raman scattering process in an all-fiber all-normal dispersion oscillator. With the use of dispersive Fourier transform, we recorded a series of single-shot spectra of consecutive laser pulses. The data indicate that the Raman process destabilizes the long-wavelength part of the laser pulse spectrum without disrupting the single-pulse generation regime. Our experiments revealed also that the oscillator displayed bistable operation for high pump powers. Two stable dissipative soliton mode-locked states were observed, together with output power hysteresis.

Titanium-carbide MXenes for work function and interface engineering in perovskite solar cells.

To improve the efficiency of perovskite solar cells, careful device design and tailored interface engineering are needed to enhance optoelectronic properties and the charge extraction process at the selective electrodes. Here, we use two-dimensional transition metal carbides (MXene Ti3C2Tx) with various termination groups (Tx) to tune the work function (WF) of the perovskite absorber and the TiO2 electron transport layer (ETL), and to engineer the perovskite/ETL interface. Ultraviolet photoemission spectroscopy measurements and density functional theory calculations show that the addition of Ti3C2Tx to halide perovskite and TiO2 layers permits the tuning of the materials' WFs without affecting other electronic properties. Moreover, the dipole induced by the Ti3C2Tx at the perovskite/ETL interface can be used to change the band alignment between these layers. The combined action of WF tuning and interface engineering can lead to substantial performance improvements in MXene-modified perovskite solar cells, as shown by the 26% increase of power conversion efficiency and hysteresis reduction with respect to reference cells without MXene.

Plasma sprayed copper coatings for improved surface and mechanical properties

Present draft reports an experimental investigation on surface characterization and mechanical properties of plasma sprayed copper coatings on copper substrate. A comparative analysis of two sample coatings fabricated by two different plasma power of 20 kW and 25 kW has been presented. Surface characteristics, mechanical properties and wetting behaviour of both the sample coatings have been invested. Coatings are characterized with bimodal distributions of both fully and partially melted particles. Coating with 25 kW plasma power possesses higher density and hardness compared to other coating. Typical lamellar structure has been observed in the fractured surface of the coatings. Compared to uncoated substrate, coating surfaces show more surface roughness. However, surface roughness decreases with increase in plasma power. Phase analysis using XRD confirms the formation of cuprous oxide due to oxidation of feedstock copper powder at high temperature during coating process. Formation of cuprous oxide with low surface energy material affects the wetting characteristics of the coated surfaces as compared to the uncoated surface. Average advancing contact angle increases with increase in plasma power and huge contact angle hysteresis has been observed for both the coated surfaces. Both the coatings show parahydrophobic behaviour exhibiting petal effect which helps in better heat transfer at higher heat flux.

Coagulated SnO2 Colloids for High‐Performance Planar Perovskite Solar Cells with Negligible Hysteresis and Improved Stability

AbstractOrganic–inorganic perovskite solar cells with a planar architecture have attracted much attention due to the simple structure and easy fabrication. However, the power conversion efficiency and hysteresis behavior need to be improved for planar‐type devices where the electron transport layer is vital. SnO2 is a promising alternative for TiO2 as the electron transport layer owing to the high charge mobility and chemical stability, but the hysteresis issue can still remain despite the use of SnO2. Now, a facile and effective method is presented to simultaneously tune the electronic property of SnO2 and passivate the defects at the interface between the perovskite and SnO2. The perovskite solar cells with ammonium chloride induced coagulated SnO2 colloids exhibit a power conversion efficiency of 21.38 % with negligible hysteresis, compared to 18.71 % with obvious hysteresis for the reference device. The device stability can also be significantly improved.

Coagulated SnO2 Colloids for High-Performance Planar Perovskite Solar Cells with Negligible Hysteresis and Improved Stability.

Organic-inorganic perovskite solar cells with a planar architecture have attracted much attention due to the simple structure and easy fabrication. However, the power conversion efficiency and hysteresis behavior need to be improved for planar-type devices where the electron transport layer is vital. SnO2 is a promising alternative for TiO2 as the electron transport layer owing to the high charge mobility and chemical stability, but the hysteresis issue can still remain despite the use of SnO2 . Now, a facile and effective method is presented to simultaneously tune the electronic property of SnO2 and passivate the defects at the interface between the perovskite and SnO2 . The perovskite solar cells with ammonium chloride induced coagulated SnO2 colloids exhibit a power conversion efficiency of 21.38 % with negligible hysteresis, compared to 18.71 % with obvious hysteresis for the reference device. The device stability can also be significantly improved.

Predictive control method for wind power regulation via a double‐screw expander‐generator and supercapacitor

A modified hybrid energy storage system (HESS) consisting of a double-screw expander-generator (DSEG) and a supercapacitor is proposed here to accommodate wind power fluctuations. The dynamic matrix control (DMC) algorithm is applied to improve the operating performance of the HESS. The reference track of the exchanging active power of the supercapacitor is pre-planned based on wind turbine output, load demand, and the predictive DSEG output. Meanwhile, a linearisation and state of charge (SOC) management strategy for the supercapacitor is proposed to avoid excessive charging-discharging. During the predictive control process, the DSEG input is continually adjusted by means of rolling optimisation combined with feedback correction until the output of the HESS approximates its expectation. Case studies show that the supercapacitor efficiently eliminates the power hysteresis of the DSEG and the DSEG eliminates the intrinsic error caused by the linearisation of the supercapacitor output in turn, indicating that the control effect of the HESS is improved.