Grid-following voltage source converter(GFLVSC)and grid-forming voltage source converter(GFM-VSC)have different dynamic characteristics for active power-frequency and reactive power-voltage supports of the power *** p...
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Grid-following voltage source converter(GFLVSC)and grid-forming voltage source converter(GFM-VSC)have different dynamic characteristics for active power-frequency and reactive power-voltage supports of the power *** paper aims to clarify and recognize the difference between gridfollowing(GFL)and grid-forming(GFM)frequency-voltage support more intuitively and ***,the phasor model considering circuit constraints is established based on the port circuit equations of the *** is revealed that the voltage and active power linearly correspond to the horizontal and vertical axes in the phasor space referenced to the grid voltage ***,based on topological homology,GFL and GFM controls are transformed and mapped into different *** topological similarity of the characteristic curves for GFL and GFM controls is the essential cause of their *** on the above model,it is indicated that GFL-VSC and GFM-VSC possess uniformity with regard to active power response,type of coupling,and phasor *** differ in synchronization,power coupling mechanisms,dynamics,and active power-voltage operation domain in the quasi-steady *** studies are undertaken on GFL-VSC and GFM-VSC integrated into a four-machine two-area *** results verify that the dynamic uniformity and difference of GFL-VSC and GFM-VSC are intuitively and comprehensively revealed.
Precise transverse emittance assessment in electron beams is crucial for advancing high-brightness beam *** opposed to intricate methodologies that use specialized devices,quadrupole focusing strength scanning(Q-scann...
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Precise transverse emittance assessment in electron beams is crucial for advancing high-brightness beam *** opposed to intricate methodologies that use specialized devices,quadrupole focusing strength scanning(Q-scanning)techniques offer notable advantages for various injectors owing to their inherent convenience and ***,their stringent approximation conditions lead to inevitable errors in practical operation,thereby limiting their widespread *** study addressed these challenges by revisiting the analytical derivation procedure and investigating the effects of the underlying approximation *** corrections were explored through a combination of data processing analysis and numerical ***,based on theoretical derivations,virtual measurements using beam dynamics calculations were employed to evaluate the correction *** experimental validations were performed at the Huazhong University of Science and technology injector to verify the effectiveness of the proposed compensation *** the virtual and experimental results confirm the feasibility and reliability of the enhanced Q-scanning-based diagnosis for transverse emittance in typical beam injectors operating under common *** the integration of these corrections and compensations,enhanced Q-scanning-based techniques emerge as promising alternatives to traditional emittance diagnosis methods.
Multilevel power conversion technology represents a significant advancement in the field of power electronics, and the active magnetic bearing (AMB) drive is a typical power electronics equipment. This article introdu...
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Multilevel power conversion technology represents a significant advancement in the field of power electronics, and the active magnetic bearing (AMB) drive is a typical power electronics equipment. This article introduces a novel hybrid neutral point clamped (NPC) multilevel AMB drive that incorporates a flying-capacitor (FC) leg, merging traditional NPC structures with the FC configuration. It upgrades the voltage levels of the magnetic bearing (MB) windings from three to five levels, thereby enhancing the system's voltage capacity and facilitating swifter current response times. Additionally, at the same voltage level, this approach improves the electromagnetic interference (EMI) characteristics of the AMB drive, diminishes current ripple and power loss, and improves the suspension precision of the MB. The efficacy of the proposed topology and its control methods has been rigorously validated on a MB blower experimental platform, demonstrating their practical applicability and performance benefits.
In this article, a novel energy management system (EMS) is presented for a grid-connected microgrid using the fuzzy neural network (FNN), aiming to minimize the mismatch between renewable power generation and load pow...
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In this article, a novel energy management system (EMS) is presented for a grid-connected microgrid using the fuzzy neural network (FNN), aiming to minimize the mismatch between renewable power generation and load power demand in the microgrid by controlling the battery charge/discharge power in real time, so as to effectively promote the local consumption of renewable energy. An on-line FNN controller is used to rapidly generate energy management instructions in response to the random variations of the net load power in real time, where the parameters are updated through off-line training periodically. The simulation results show that: 1) the presented FNN-based EMS can get better optimization results compared to each benchmark EMS, achieving an average decrease of 18.0217% on the optimization function value in all tested cases when regarding the best performing one among benchmark EMSs as the comparison object;2) the presented FNN-based EMS has high real-time performance on level of seconds;and 3) the presented FNN-based EMS has good interpretability that all the used parameters in the FNN have interpretable meanings. The experimental results on the testbed match well with the corresponding simulation results, demonstrating the effectiveness and practicability of the presented FNN-based EMS for practical applications.
The application of superconducting(SC)technology enables magnets to excite strong fields with small footprints,which has great potential for miniaturizing proton therapy ***,the slow ramping rate of SC magnets results...
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The application of superconducting(SC)technology enables magnets to excite strong fields with small footprints,which has great potential for miniaturizing proton therapy ***,the slow ramping rate of SC magnets results in a low treatment efficiency compared with normal-conducting(NC)*** address this problem,this study proposes a compact proton therapy gantry design with a large momentum acceptance utilizing alternating-gradient canted-cosine-theta(AG-CCT)SC *** our design,a high-transmission degrader is mounted in the middle of the gantry,and the upstream beamline employs NC magnets with small *** of the degrader,large-bore AG-CCT magnets with strong alternating focusing gradients are set symmetrically as a local achromat,which realizes a momentum acceptance of 20%(or 40%in the energy domain).Therefore,only three magnetic working points are required to cover a treatment energy of 70-230 Me *** to the large momentum acceptance,the proton beam after the degrader can be directly delivered to the isocenter without truncating its energy spectrum,which can significantly increase the treatment efficiency but causes severe dispersion effects during pencil beam ***,a compensation method was introduced by tuning the normal and skewed quadrupoles during the scanning *** a result,the new gantry not only presents a remarkable reduction in the size and weight of the facility but also shows good potential for fast treatment.
Currently, although some progress has been made in infancy-stage rocking-chair aqueous zinc-ion batteries（AZIBs）, more discussions have focused only on the different electrochemical performances displayed by differe...
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Currently, although some progress has been made in infancy-stage rocking-chair aqueous zinc-ion batteries（AZIBs）, more discussions have focused only on the different electrochemical performances displayed by different material types rather than the intrinsic ion transport migration electrochemistry. Herein, we for the first time delve into the mechanism of tailoring the solvation sheath and desolvation processes at the electrode/electrolyte interfaces to enhance the structural stabilities in the deep discharge states. In this work, the TiO2front interfaces are induced on electrochemically active but unstable TiSe2host materials to construct unique TiO2/TiSe2–C heterointerfaces. According to X-ray absorption near edge structure（XANES）,differential electrochemical mass spectrometry（DEMS）, and electrochemical quartz crystal microbalance（EQCM）, the intercalated species are transformed from [Zn（H2O）6]2+to [Zn（H2O）2]2+due to the built-in electric fields（BEFs） effects, further accelerating the ion transfer kinetics. Furthermore, owing to the absence of high-energy desolvation solvents released from desolvation processes, hydrogen evolution reaction（HER） energy barriers, Ti–Se bond strength, and structural stabilities are significantly improved, and the initial CE and HER overpotentials of the TiO2/TiSe2–C heterointerfaces increased from 13.76%to 84.7%, and from 1.04 to 1.30 V, respectively, and the H2precipitation current density even at-1.3 V decreased by 73.2%. This work provides valuable insights into the complex interface electrochemical mechanism of tailoring the solvation sheath and desolvation processes toward rocking-chair zinc-ion batteries.
Base station(BS)backup batteries(BSBBs),with their dispatchable capacity,are potential demand-side resources for future power *** enhance the power supply reliability and post-contingency frequency security of power s...
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Base station(BS)backup batteries(BSBBs),with their dispatchable capacity,are potential demand-side resources for future power *** enhance the power supply reliability and post-contingency frequency security of power systems,we propose a two-stage stochastic unit commitment(UC)model incorporating operational reserve and post-contingency frequency support provisions from massive BSBBs in cellular networks,in which the minimum backup energy demand is considered to ensure BS power supply *** energy,operational reserve,and frequency support ancillary services are co-optimized to handle the power balance and post-contingency frequency security in both forecasted and stochastic variable renewable energy(VRE)***,we propose a dedicated and scalable distributed optimization framework to enable autonomous optimizations for both dispatching center(DC)and *** BS model parameters are stored and processed locally,while only the values of BS decision variables are required to upload to DC under the proposed distributed optimization framework,which safeguards BS privacy *** studies on a modified IEEE 14-bus system demonstrate the effectiveness of the proposed method in promoting VRE accommodation,ensuring post-contingency frequency security,enhancing operational economics,and fully utilizing BSBBs'energy and power ***,the proposed distributed optimization framework has been validated to converge to a feasible solution with near-optimal performance within limited ***,numerical results on the Guangdong 500 kV provincial power system in China verify the scalability and practicality of the proposed distributed optimization framework.
Efficient and accurate insulator defect detection is essential for maintaining the safe and stable operation of transmission ***,the detection effectiveness is adversely impacted by complex and changeable environmenta...
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Efficient and accurate insulator defect detection is essential for maintaining the safe and stable operation of transmission ***,the detection effectiveness is adversely impacted by complex and changeable environmental backgrounds,particularly under extreme weather that elevates accident ***,this research proposes a high-precision intelligent strategy based on the synthetic weather algorithm and improved YOLOv7 for detecting insulator defects under extreme *** proposed meth-odology involves augmenting the dataset with synthetic rain,snow,and fog algorithm ***,the original dataset undergoes augmentation through affine and colour transformations to improve model's generalisation performance under complex power inspection *** achieve higher recognition accuracy in severe weather,an improved YOLOv7 algorithm for insulator defect detection is proposed,integrating focal loss with SIoU loss function and incorporating an optimised decoupled head *** results indicate that the synthetic weather algorithm processing significantly improves the insulator defect detection accuracy under extreme weather,increasing the mean average precision by 2.4%.Furthermore,the authors’improved YOLOv7 model achieves 91.8%for the mean average precision,outperforming the benchmark model by 2.3%.With a detection speed of 46.5 frames per second,the model meets the requirement of real-time detection of insulators and their defects during power inspection.
OH radicals and O atoms are two of the most important reactive species of non-equilibrium atmospheric pressure plasma(NAPP),which plays an important role in applications such as plasma ***,experimental studies on how ...
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OH radicals and O atoms are two of the most important reactive species of non-equilibrium atmospheric pressure plasma(NAPP),which plays an important role in applications such as plasma ***,experimental studies on how the gas content affects the postdischarge temporal evolutions of OH and O in the noble gas ns-NAPP are very *** this work,the effect of the percentages of O_(2),N_(2),and H_(2)O on the amounts of OH and O productions and their post-discharge temporal behaviors in ns-NAPP is investigated by laser-induced fluorescence(LIF)*** results show that the productions of OH and O increase and then decrease with the increase of O_(2)*** OH and O densities reach their maximum when about 0.8%O_(2)is *** increase of the O_(2)concentration results in a decrease of the initial densities of both OH and O,and leads to their faster *** increase of N_(2)percentage also results in the increase and then decrease of the OH and O densities,but the change is ***,when the H_(2)O concentration is increased from 100 to 3000 ppm,the initial OH density increases slightly,but the OH density decays much faster,while the initial density of O decreases with the increase of the H_(2)O *** analysis,it is found that OH and O are mainly produced through electron collisional dissociation.O(^(1)D)is critical for OH generation.O_(3)accelerates the consumption processes of OH and O at high O_(2)*** addition of H_(2)O in the NAPP considerably enhances the electronegativity,while it decreases the overall plasma reactivity,accelerates the decay of OH,and reduces the O atom density.
In this letter, a pulse alternation modulation (PAM) for four-level buck/boost (FLBB) converter is proposed. The inherent flaws of the existing modulations are analyzed. The low slope of the inductor current near the ...
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