Power Stability Research Articles

Research on Optimal Driving Torque Control Strategy for Multi-Axle Distributed Electric Drive Heavy-Duty Vehicles

Multi-axle distributed electric drive heavy-duty vehicles have the characteristics of high transmission efficiency, strong maneuverability, and good passability, making them widely used in large cargo transportation. However, the current driving torque control strategies of multi-axle distributed electric drive heavy-duty vehicles lack comprehensive consideration of their longitudinal and lateral dynamic characteristics, making it difficult to comprehensively optimize multiple performances such as power economy, comfort, and stability. In order to solve the above problems, This work focuses on a five-axle distributed electric drive heavy-duty vehicle. Firstly, given the differences in dynamics between two-axle vehicles and multi-axle vehicles, the dynamic model of the multi-axle distributed electric drive heavy-duty vehicle and its critical components is constructed. Then, by analyzing the characteristics of power economy, comfort, and stability of the multi-axle distributed electric drive heavy-duty vehicle, an optimal driving torque control strategy based on multiple performance coordination is proposed. Finally, on the hardware-in-the-loop (HiL) platform, the performance of the optimal driving torque control strategy proposed in this paper is verified by using the China Heavy-Duty Commercial Vehicle Test Cycle for Truck (CHTC-HT) and a straight-line acceleration driving condition on a split friction road. The simulation test results show that, compared with the traditional torque average distribution strategy, the proposed optimal driving torque control strategy can reduce the energy consumption rate by 3.45% in CHTC-HT. The strategy is attributed to the driving torque distribution based on the vehicle’s optimal instantaneous energy consumption, and vehicle comfort is also ensured by the driving mode switching frequency suppression. Subsequently, the vehicle’s stability on the split friction road is effectively improved by the torque coordination compensation strategy. This control strategy significantly improves the comprehensive performance of multi-axle distributed electric drive heavy-duty vehicles.

Dimerized M‐series Acceptors with Low Diffusion Coefficients for Efficient and Stable Polymer Solar Cells

As the simplest oligomeric acceptors, dimerized acceptors (DAs) are easier to synthesize, and more importantly, they can retain good intermolecular interaction and photovoltaic properties of their parent small‐molecule acceptors (SMAs). Nevertheless, currently most efficient DAs are derived from banana‐shaped acceptors and they might suffer from inferior device stability with high diffusion coefficients. Herein, we design and synthesize two planar DAs (DMT‐FH and DMT‐HF) by bridging two linear‐shaped M‐series SMAs with a thiophene unit. The effects of fluorination position on the diffusion coefficients, power conversion efficiencies (PCEs) and stability of the DAs are systematically studied. Our results suggest that DMT‐HF with fluorination on the ending indanone groups shows enhanced intermolecular interactions, improved PCE and stability compared with the counterpart (DMT‐FH) with fluorination on the central indanone groups. Further optimization on the DMT‐HF‐based devices yields an outstanding PCE of 17.17%, which is the highest among all linear‐shaped SMA‐based DAs. Notably, with the low diffusion coefficient (3.36×10‐24 cm2 s‐1) of DMT‐HF, the resulting device retains over 93% of the initial PCE after 5000 h of continuous heating at 85 oC, suggesting its excellent thermal stability. The results highlight the importance of intermolecular interaction and fluorination for achieving efficient and stable polymer solar cells.

Dimerized M-Series Acceptors with Low Diffusion Coefficients for Efficient and Stable Polymer Solar Cells.

As the simplest oligomeric acceptors, dimerized acceptors (DAs) are easier to synthesize, and more importantly, they can retain good intermolecular interaction and photovoltaic properties of their parent small-molecule acceptors (SMAs). Nevertheless, currently most efficient DAs are derived from banana-shaped acceptors and they might suffer from inferior device stability with high diffusion coefficients. Herein, we design and synthesize two planar DAs (DMT-FH and DMT-HF) by bridging two linear-shaped M-series SMAs with a thiophene unit. The effects of fluorination position on the diffusion coefficients, power conversion efficiencies (PCEs) and stability of the DAs are systematically studied. Our results suggest that DMT-HF with fluorination on the ending indanone groups shows enhanced intermolecular interactions, improved PCE and stability compared with the counterpart (DMT-FH) with fluorination on the central indanone groups. Further optimization on the DMT-HF-based devices yields an outstanding PCE of 17.17 %, which is the highest among all linear-shaped SMA-based DAs. Notably, with the low diffusion coefficient (3.36×10-24 cm2 s-1) of DMT-HF, the resulting device retains over 93 % of the initial PCE after 5000 h of continuous heating at 85 °C, suggesting its excellent thermal stability. The results highlight the importance of intermolecular interaction and fluorination for achieving efficient and stable polymer solar cells.

Sub-picometer level all-solid-state narrow linewidth single-frequency Pr3+:LiYF4 laser in the near-infrared spectral region.

We report an all-solid-state near-infrared single-frequency (single longitudinal mode, SLM) Pr3+:LiYF4 (Pr:YLF) laser with the spectral linewidth at the sub-picometer level. The SLM lasers with center wavelengths of 868 and 907 nm are realized in Pr:YLF crystal for the first time to the best of our knowledge. The maximum output powers of SLM lasers at 868 and 907 nm are 102 and 213mW, corresponding to the narrowest spectral linewidths of 82 MHz (0.21 pm) and 94 MHz (0.26 pm), respectively. At the maximum output power, the beam quality factors in the x and y directions are measured as 1.25 and 1.16 at 868 nm and 1.21 and 1.13 at 907 nm, respectively. The output power stabilities of the 868 and 907 nm SLM lasers are calculated as 1.39% and 0.87%, respectively. The successful realization of 868 and 907 nm all-solid-state SLM lasers makes up for the gap that the Pr:YLF SLM lasers developed in the past are focused on the visible region, enriches the types of near-infrared (NIR) SLM lasers, and can provide practical applications in biomedicine, cold atom physics, and optical atom manipulation.

Comparative Analysis of Physical and Functional Properties of Colored Horse Gram Varieties (Macrotyloma uniflorum) and Its Flour

Pulses has important role in contributing to food and nutritional security and replenishing soil nutrients having a huge potential in addressing needs like future global food security, nutrition and environmental sustainability. Horse gram (Macrotyloma uniflorum) is a minor, under-exploited legume of tropics and subtropics grown under dry-land agriculture. The present study was conducted with the objective to maximize the utilization of horse gram and its flour physical and functional properties. Hundred grain weight and density (3.33 g,1.29 g/ml) were higher in cream colored variety and it was lighter, redder (less green), yellower (less blue) than brown and black colored varieties. Thickness of varieties varied significantly, highest being in brown (2.18 mm) colored variety. Hydration capacity, hydration index, swelling capacity and percent germination (2.92 g/100 grains, 0.93, 3.83 ml/100 grains and 91.66 %) varied significantly with highest being in brown colored variety. Maximum amount of all the flours passed through 52 BSS standard sieve having 300 µ sieve opening. Loose bulk density was high in brown colored flour (0.41 g/ml) whereas tapped bulk density was high in cream colored flour (0.63 g/ml). Cream-colored horse gram flour was lighter (L* value being 78.72), redder (a* value being 5.78) and yellower (b* value being 16.84). There was significant difference in the functional properties of flour. The black colored flour had highest water absorption capacity (2.31 ml/g), oil absorption capacity (2.15 ml/g), swelling power (9.14 g/g), foaming capacity (36.23 %) and foaming stability (32.13 %) than other two flours. The wettability, flowability and cohesiveness of all three flours were good, fair and low respectively. Thus brown and black colored varieties had better physical and functional properties than cream-colored variety. The brown and black colored flour had highest loose bulk density whereas cream colored flour had highest tapped bulk density. Black colored flour had highest water and oil absorption capacity, swelling power, foaming capacity and foaming stability.

Uniform Molecular Adsorption Energy‐Driven Homogeneous Crystallization and Dual‐Interface Modification for High Efficiency and Thermal Stability in Inverted Perovskite Solar Cells

AbstractInterfacial defects between perovskite and adjacent charge transport layers present a significant obstacle, hindering the enhancement of power conversion efficiency (PCE) and stability in perovskite solar cells (PSCs). To address this challenge, a dual‐interface modification is proposed to aim at improving the performance of mixed‐halide PSCs. Specifically, the hole‐collecting side is modified with 5‐Aminopyridine‐2‐carboxylic Acid (APC), while the electron‐collecting side is modified with 2‐thiopheneethylammonium chloride (TEACl). The multifunctional APC enhances charge transfer by tailoring the interface between the perovskite and poly(triarylamine) (PTAA) through multiple bonding interactions, thereby suppressing interfacial nonradiative recombination. Density functional theory studies reveal that APC on the perovskite surface induces uniform adsorption energy, promoting homogenous crystallization without residual stress. Additionally, APC interlayer eliminates the localized edge states induced by the iodine vacancies near the conduction band edge. Further improvement in the device performance is achieved by passivating the top perovskite surface with TEACl, leading to well‐matched energy bands and reduced vacancy trap states. As a result, champion cell achieves a PCE of 24.87% with an open‐circuit voltage of 1.188 V. Furthermore, The dual‐interface modification improves thermal stability due to enhanced ion‐migration activation energy.

Generation and Evaluation of an Efficient Femtosecond Green Laser.

We demonstrate femtosecond ultra-stable green laser generation by an ytterbium-doped polarization-maintaining fiber laser with a 2.4 mm long lithium triborate (LBO) crystal. We generated 5.6 W of femtosecond green light at 520 nm for a fundamental power of 12 W, which corresponds to a conversion efficiency of 46.7%. The fiber chirped-pulse amplifier, which has an environmentally immune front end, delivered 170 fs pulses at a 75 MHz repetition rate centered at 1040 nm. According to the dispersion of the optical material in a double-frequency setup, the introduced dispersion had a negligible effect for the green laser, and the pulse duration of the generated green laser was calculated to be 171 fs, resulting in an excellent power stability, with fluctuation as low as 0.16% of the generated green light. This system could be of great interest in ultrafast optical and photobiology research.

Watt-level ultra-flat wideband supercontinuum generation in GeO2 fiber by femtosecond pulse

The high-power ultra-flat supercontinuum (SC) sources play an important role in various fields. In this letter, we experimentally demonstrated an all-fiber, high-power, ultra-flat SC source in GeO2 highly nonlinear fiber (HNLF) pumped by a femtosecond fiber laser system. The system is mode-locked by a semiconductor saturable absorber mirror with an all-polarization-maintaining (PM) structure. Based on the technology of chirped pulse amplification, a maximum power of 3.12 W was realized with a repetition rate of 80 MHz at 1.56 μm, and the pulse duration was compressed to 124 fs in a segment of PM single-mode fiber. Furthermore, by optimizing the length of the HNLF, a wideband SC spectrum of nearly 700 nm was obtained at10 dB with a maximum power of 1.82 W, and the flatness of the spectrum was better than 5 dB in the range of 1600–2200 nm. We observed that the pulse evolved into a noise-like pulse with a narrowest pulse duration of 62 fs. Thanks to the all-PM structure of the fiber laser, the long-term stability of SC power was manifested with a relative fluctuation as low as 0.53 % over 6 h.

Crown Ethers with Different Cavity Diameters Inhibit Ion Migration and Passivate Defects toward Efficient and Stable Lead Halide Perovskite Solar Cells.

Organic-inorganic hybrid metal halide perovskite solar cells have been considered as one of the most promising next-generation photovoltaic technologies. Nevertheless, perovskite defects and Li+ ionic migration will seriously affect the power conversion efficiency and stability of the formal device. Herein, we designed two crown ether derivatives (PC12 and PC15) with different cavity diameters, which selectively bind to different metal cations. It is found that PC15 in perovskite precursor solution can actively regulate the nucleation and crystallization processes and passivate the uncoordinated Pb2+ ions, while PC12 at the interface between the perovskite layer and hole-transporting layer can effectively inhibit the migration of Li+ ions and reduce nonradiative recombination losses. Therefore, PC12 and PC15 can act as "lubricant" and defect passivators, as well as inhibitors of ion migration, when they are synergistically applied at the surface and bulk of perovskite layer. Consequently, the optimized device achieved a champion efficiency of 24.8% with significantly improved humidity, thermal, and light stability.

Lattice Strain Regulation and Halogen Vacancies Passivation Enable High-Performance Formamidine-Based Perovskite Solar Cells.

Formamidinium lead iodide (FAPbI3) perovskite has lately surfaced as the preferred contender for highly proficient and robust perovskite solar cells (PSCs), owing to its favorable bandgap and superior thermal stability. Nevertheless, volatilization and migration of iodide ions (I-) result in non-radiating recombination centers, and the presence of large formamidine (FA) cations tends to cause lattice strain, thereby reducing the power conversion efficiency (PCE) and stability of PSCs. To solve these problems, the lead formate (PbFa) is added into the perovskite solution, which effectively mitigates the halogen vacancy and provides tensile strain outside the perovskite lattice, thereby enhancing its properties. The strong coordination between the C═O of HCOO- and Pb-I backbones effectively immobilizes anions, significantly increases the energy barrier for anion vacancy formation and migration, and reduces the risk of lead ion (Pb2+) leakage, thereby improving the operation and environmental safety of the device. Consequently, the champion PCE of devices with Ag electrodes can be increased from 22.15% to 24.32%. The unencapsulated PSCs can still maintain 90% of the original PCE even be stored in an N2 atmosphere for 1440h. Moreover, the target devices have significantly improved performance in terms of light exposure, heat, or humidity.

An adaptive two-step staircase static reconfiguration method for improving the power generation of PV array

Partial shading of solar photovoltaic (PV) panels can significantly affect the performance of solar PV arrays. Various reconfiguration techniques have been explored in recent years. Still, their applicability to actual PV power generation is controversial due to the number of electrical switches, physical locations, interconnections and complexity. This study proposes an adaptive two-step staircase (A2SS) static reconfiguration method. The technique is experimentally validated in several conditions and compared with the conventional TCT connection, single-step staircase (1SS) static reconfiguration method, Arrow soduku, modified odd–even–prime (MOEP) and two-step staircase(2SS) static reconfiguration method. For the eight shading cases of LN, LW, LD, Ran, Cen, Cor, CD, and Plus at SET#1, after reconfiguring the PV array using A2SS, the power has a significant improvement of 17.6%, 17.0%, 13.4%, 13.4%, 20.6%, 20.2%, 3.1%, and 0.82% than TCT. In the four shading cases of Lr. C, Lr. O, Lr. T, and Lr. U at SET#2, the power showed a significant improvement of 11.8%, 9.2%, 10.7%, and 15.8% compared to TCT. It also has the best performance in various reconfiguration techniques, which are mentioned. In addition, the A2SS reconfiguration method can be better applied to various sizes of PV arrays. By optimizing the shading distribution and adjusting the row irradiance deviation, the power stability of PV power generation is improved while maximizing energy efficiency.

Multi-paradigm modelling and control of microgrid systems for better power stability in the Rockaways

The Rockaways Peninsula faces issues related to congestion and power outages during times of peak usage. Additionally, it is susceptible to disruptions caused by disasters such as hurricanes and storms. In this paper, we propose a new methodology that employs multi-paradigm modelling and control for the design and implementation of interconnected microgrid systems in the Rockaways. Microgrids are small-scale power networks that incorporate renewable energy technologies for power generation and distribution to enhance the control of energy supply and demand. Multi-paradigm modelling is employed to describe microgrids’ dynamic behavior more accurately by integrating system dynamics, agent-based modelling, as well as discrete event and continuous time simulation. We use agent-based models to describe the behavior of separate microgrid elements and the microgrid as a whole. Discrete event/continuous time simulation is used to analyze real-time operation of electrical parameters, such as voltage, current and frequency. Thus, the design, analysis and performance of microgrids are improved. Also, control strategies are used for the purpose of enabling the microgrids to operate effectively by responding to changes in power supply and demand and minimizing the effects of disturbances. The findings of this study demonstrate the feasibility and resilience benefits of incorporating multi-paradigm modelling and control in the design and management of microgrid systems in the Rockaways, which can result in the development of more durable, efficient, and sustainable energy systems in the region.

Photocontrolled interfacial defect passivation of coumarin 151 with enhanced hydrophobicity for stable perovskite solar cell

Defect passivation has been recognized as an efficient strategy to boost the performance of perovskite solar cells (PSCs) for commercial applications. However, most reported strategies overly emphasize passivation of undesirable defects, while ignoring the inherent instability of perovskite materials caused by environmental risks. In this study, we explore a groundbreaking strategy to integrate various functions of defect passivation, photoresponsivity and photocontrolled hydrophobicity in one device via the surface engineering of 7-amino-4-trifluoromethylcoumarin (C151). The detailed experiments demonstrate that C151 based PSCs have regulated power conversion efficiency and stability responding to UV illumination due to the photodimerization of coumarin. On the one hand, the photodimer of C151 (C151-L) can form stronger chelation with various defect sites in comparison with C151, resulting in optimized energy level arrangement, superior charge extraction/transport and significantly inhibited nonradivation recombination. One the other hand, morphological changes of the perovskite film triggered by UV illumination also bring convertible surface hydrophobicity transition. As a result, the unpackaged C151-L modified device exhibits excellent stability maintaining 91% of its initial PCE after aging for 1000 h under a relative humidity of 30%–40% at 20 °C. Moreover, C151-L plays a positive role in improving the operation stability against high humidity, continuous UV radiation, and heating stress. This work may offer more choices for materials with tunable properties in high-efficiency optoelectronic devices.

Power stabilization of a terahertz-frequency quantum-cascade laser using a photonic-integrated modulator

We demonstrate a technique to stabilize the emission from a 3.4-THz quantum-cascade laser against power drifts, using a recently developed photonic integrated circuit (PIC) structure formed by coupling a racetrack resonator with a ridge waveguide. This structure enables a dynamic power-control range of ±15% and locking over >600 s using a proportional–integral control loop. The resonator yields a 50% weaker perturbation to the laser emission frequency when compared with direct laser modulation, and hence offers the prospect of simultaneous, quasi-independent control of power and frequency. Progress towards integrating the PIC with a precision micromachined rectangular metallic waveguide module has also been demonstrated, with power modulation of the principal laser emission line being observed during pulsed operation.

Power and voltage stability analysis of electric vehicle distribution network considering virtual power plants

Power and voltage stability analysis of electric vehicle distribution network considering virtual power plants

Educational Policy and Activities of East India Company (1600-1765)

Abstract: The 19th century witnessed a profound transformation in the political landscape of many regions, characterized by the rise of nationalism and the subsequent formation of nation-states. This research work delves into the historical context, key drivers, and consequences of this significant historical phenomenon. The research offers light on a crucial time in global history by investigating the causes of nationalism and its effects on the formation of nation-states. Employing a multidisciplinary approach, the research draws from historical, political, and sociocultural perspectives to analyze the rise of nationalism. It delves at how many peoples inside established empires and territories felt a feeling of commonality due to their shared cultural, linguistic, and historical identities. The work delves into the influence of Enlightenment ideas, Romanticism, and intellectual movements that fueled the concept of self-determination and the sovereignty of distinct nations. The study also scrutinizes the role of key historical events and figures that catalyzed the nationalist fervor. From the unification of Italy led by Giuseppe Garibaldi to the German unification orchestrated by Otto von Bismarck, the work examines the strategies employed to consolidate fragmented territories into cohesive nation-states. It also considers the implications of these transformations on regional stability, diplomacy, and balance of power. Furthermore, the research investigates the potential tensions arising from the juxtaposition of national identities and existing imperial structures. It delves into instances where nationalism clashed with multiethnic empires, often leading to complex negotiations of autonomy, self-governance, or secession.

Improving cyber-physical-power system stability through hardware-in-loop co-simulation platform for real-time cyber attack analysis

With advancements in communication systems and measurement technologies, smart grids have become more observable and controllable, evolving into cyber-physical-power systems (CPPS). The impact of network security and secondary equipment on power system stability has become more evident. To support the existing grid toward a smart grid scenario, smart metering plays a vital role at the customer end side. Cyber-Physical systems are vulnerable to cyber-attacks and various techniques have been evolved to detect a cyber attack in the smart grid. Weighted trust-based models are suggested as one of the most effective security mechanisms. A hardware-in-loop CPPS co-simulation platform is established to facilitate the theoretical study of CPPS and the formulation of grid operation strategies. This paper examines current co-simulation platform schemes and highlights the necessity for a real-time hard-ware-in-the-loop platform to accurately simulate cyber-attack processes. This consideration takes into account the fundamental differences in modeling between power and communication systems. The architecture of the co-simulation platform based on RT-LAB and OPNET is described, including detailed modeling of the power system, communication system, and security and stability control devices. Additionally, an analysis of the latency of the co-simulation is provided. The paper focuses on modeling and implementing methods for addressing DDOS attacks and man-in-the-middle at-tacks in the communication network. The results from simulating a 7-bus system show the effectiveness and rationality of the co-simulation platform that has been designed.

Synthesis of trimetallic oxide/nitrogen-doped carbon composite using ZIF-guided combustion pyrolysis for efficient bifunctional oxygen catalysis in zinc–air batteries

Multi-element catalysts coupled with heterogeneous atom-doped carbons have significant potential for bifunctional oxygen catalysis owing to multiple active sites and tunable electronic structures. However, their synthesis routes involve multi-step procedures, limiting efficient screening of optimal designs considering electrocatalytic performance. Herein, we present a single-step strategy for synthesizing Co/Ni/Fe trimetallic oxide (TO) catalysts within nitrogen-doped carbon (NC) networks via combustion pyrolysis of ZIF-67 metal–organic framework/NiO/Fe2O3 precursors. The ultrafast melting-recrystallization induced by a rapid heating-cooling duration (∼1.5 s) lead to uniformly mixing metal elements, enabling abundant oxygen vacancies/strong chemical bonds within the porous structure, and optimizing the energy barrier for bifunctional catalysis, while decreasing interfacial resistances. The optimized TO-NC catalyst exhibits excellent overpotential of 0.88 V, and provides outstanding power density (125 mW cm−2) and stability (>200h) to a liquid zinc–air battery, outperforming those with a Pt/C + Ir/C catalyst. This research establishes scalable yet tunable thermochemical fabrication of multi-element/carbon-based catalysts.

Convergence of power sequences of operators via their stability

This paper is concerned with the convergence of power sequences and stability of Hilbert space operators, where “convergence” and “stability” are considered with respect to weak, strong and norm topologies. It is proved that an operator has a convergent power sequence if and only if it is a (not necessarily orthogonal) direct sum of an identity operator and a stable operator. This reduces the issue of convergence of the power sequence of an operator T to the study of stability of T. The question of when the limit of the power sequence is an orthogonal projection is investigated. Among operators sharing this property are hyponormal and contractive ones. In particular, a hyponormal or a contractive operator with no identity part is stable if and only if its power sequence is convergent. In turn, a unitary operator has a weakly convergent power sequence if and only if its singular-continuous part is weakly stable and its singular-discrete part is the identity. Characterizations of the convergence of power sequences and stability of subnormal operators are given in terms of semispectral measures.

A novel development of an unmanned surface vehicle directly powered by an air-cooled proton exchange membrane fuel cell stack

Most compact Unmanned Surface Vehicles (USVs) used in water quality monitoring and maritime surveillance rely on lithium batteries. However, they're only ideal for short missions. This paper first fabricates a novel lightweight, air-cooled, high-power-density Proton Exchange Membrane Fuel Cell (PEMFC) stack with ultrathin steel bipolar plates as the primary power source for a self-made compact USV. This stack consists of 40 single cells and integrates a reliable air-cooled system, operating in parallel with a supercapacitor to enhance its performance. Experimental results show that this PEMFC-powered USV outperforms the main lithium battery-powered counterpart, offering an extended cruising range and better power stability and significantly increasing the cruising range from 8 km to 38 km when the PEMFC stack and the main lithium battery are of similar volume and weight. Integrating a low voltage purging logic with a 0.4 V threshold in the dead-end anode (DEA) mode results in a remarkable hydrogen utilization rate of up to 98%. Moreover, the average voltage of the PEMFC stack with the supercapacitor consistently exceeds that of the stack without the supercapacitor by approximately 0.125 V, mitigating the impact of rapid load changes. The results verify the feasibility of the proposed air-cooled PEMFC-powered USV.