Electrochemical synthesis of trimetallic nickel-iron-copper nanoparticles via potential-cycling for high current density anion exchange membrane water-splitting applications

Hydrogen is known for its elevated energy density and environmental compatibility and is a promising alternative to fossil fuels.Alkaline water electrolysis utilizing renewable energy sources has emerged as a means to obtain high-purity hydrogen.Nevertheless,electrocatalysts used in the process are fabricated using conventional wet chemical synthesis methods,such as sol-gel,hydrothermal,or surfactantassisted approaches,which often necessitate intricate pretreatment procedures and are vulnerable to post-treatment contamination.Therefore,this study introduces a streamlined and environmentally conscious one-step potential-cycling approach to generate a highly efficient trimetallic nickel-iron-copper electrocatalyst in situ on nickel foam.The synthesized material exhibited remarkable performance,requiring a mere 476 mV to drive electrochemical water splitting at 100 mA cm^(-2)current density in alkaline solution.Furthermore,this material was integrated into an anion exchange membrane watersplitting device and achieved an exceptionally high current density of 1 A cm^(-2)at a low cell voltage of2.13 V,outperforming the noble-metal benchmark(2.51 V).Additionally,ex situ characterizations were employed to detect transformations in the active sites during the catalytic process,revealing the structural transformations and providing inspiration for further design of electrocatalysts.

Active injection protection scheme for flexible HVDC grids based on amplitude of input impedance

High-voltage direct current(HVDC)grids require fast and reliable protection of the DC lines.The performance of traditional protection schemes is easily impaired by the limitations of the boundary condition and nonlinearity from the control of converters.One of the key technologies for flexible HVDC grids is the half-bridge modular multilevel converter(HB-MMC).Considering the high controllability of HB-MMC,this study proposes an active injection protection scheme to improve the reliability and sensitivity of the HVDC grid protection.The HB-MMC is used to inject a sinusoidal characteristic signal,at the specified frequency,into the DC lines.Then,the voltage and current at the specified frequency are extracted using the Prony algorithm to calculate the input impedance,which is used for the identification of internal and external faults.The active injection protection scheme was simulated for various cases in the simulation software Power Systems Computer Aided Design.The simulation results indicate that the proposed protection scheme is highly reliable and can overcome transition resistance.

A Double-Ended Protection Principle for an LCC-VSC-MTDC System with Strong Anti-Interference Ability

The DC grid technology of multi-power supply and multi-drop-point power reception is an effective solution for large-scale renewable energy integration into the power grid.Line-commutated converter-Voltage source converter(LCC-VSC)power grids are one of the more important developmental directions of the future power grid that have occured in recent years.But the multi-terminal high voltage direct current system has the problems of inconsistent boundary characteristics,inconsistent control,and fault response characteristics,which puts higher requirements on the protection scheme.Thus,a completely new protection principle is proposed in this paper.Firstly,the fault characteristics of distributed capacitance current are analyzed.The reactive power calculated by the distribution parameters of different frequencies is different.Subsequently,the fault characteristics of DC reactive power are analyzed,and a DC reactive power extraction algorithm is proposed.The polarity of the multi-band DC reactive power is used to construct the protection scheme.Finally,the LCC-VSC power grid model verifies the correctness and superiority of the proposed protection scheme.The proposed scheme uses DC reactive power instead of fault current to solve the long delay problem caused by distributed capacitance.Compared with the prior art,the proposed solution is not affected by distributed capacitance and has a stronger anti-interference ability(600Ω+10 dB+1 ms).

A Single-Ended Protection Principle for LCC-VSC-MTDC System with High Resistance Fault Tolerance

Line-commutated converter-voltage source converter(LCC-VSC)power transmission technology does not have the problem of communication failure very usually.It therefore can support the long-distance,long-capacity transmission of electric energy.However,factors such as topology,control strategy,and short-circuit capacities make the traditional protection principles not fully applicable to LCC-VSC hybrid transmission systems.To enhance the reliability of hybrid DC systems,a single-ended principle based on transmission coefficients is proposed and produced.First,the equivalent circuit of the LCC-VSC hybrid DC system is analyzed and the expression of the first traveling wave is deduced accordingly.Then,the concept of multi-frequency transmission coefficients is proposed by analyzing the amplitude-frequency,and the characteristics of each element.Finally,the LCC-VSCDC system model is built to verify the reliability and superiority of the principle itself.Theoretical analysis and experimental verification show that the principle has strong interference resistance.

Blockchain-based Distributed Power Market Trading Mechanism

Distributed power market trading has the characteristics of large number of participants,scattered locations,small single trading scale,and point-to-point trading.The traditional centralized power trading model has the problems of large load,low efficiency,high cost,reliance on third parties and unreliable data.With the characteristics of decentralization and nontampering,blockchain can establish a point-to-point trusted trading environment and provide effective solutions to the above problems.Therefore,this paper proposed a distributed power market trading framework based on blockchain.In this framework,the distributed power supply characteristics and trading needs of each participant are analyzed,a complete distributed trading process based on blockchain is designed.In addition,we have studied the key technologies of distributed power market trading.With the goal of power service reputation and maximum revenue of distributed power providers,we have established a matching degree model,a distributed power market trading optimization model,and designed a smart contract-based power market trading optimization strategy and power trading settlement strategy.Finally,we designed experiments to verify the performance of the proposed framework.

A Similarity Comparison Based Pilot Protection Scheme for VSC-HVDC Grids Considering Fault Current Limiting Strategy

In the voltage source converter based high-voltage direct current(VSC-HVDC)grids,fast and reliable protections are the key technologies.The traditional protection schemes are easily affected by fault resistance,line distributed capacitance,etc.Meanwhile,the influence of fault current limiting strategy(FCLS)has not been fully considered.In this paper,the fault characteristics under FCLS and the feasibility of traditional travelling wave protections are analyzed.To improve the reliability and sensibility,a similarity comparison based pilot protection scheme is proposed,which focuses on the relationship between the fault characteristics and the state of the protected transmission line,with the establishment of a precise frequencydependent transmission line model.The criteria based on the similarity comparison calculated by cross-wavelet can identify the fault effectively.Meanwhile,the protection scheme can also endure the influence of error synchronization.Finally,the protection performance is verified in the PSCAD/EMTDC under different fault conditions.

Improved Subsynchronous Oscillation Parameter Identification with Synchrophasor Based on Matrix Pencil Method in Power Systems

The subsynchronous oscillations(SSOs)related to renewable generation seriously affect the stability and safety of the power systems.To realize the dynamic monitoring of SSOs by utilizing the high computational efficiency and noise-resilient features of the matrix pencil method(MPM),this paper propos es an improved MPM-based parameter identification with syn chrophasors.The MPM is enhanced by the angular frequency fitting equations based on the characteristic polynomial coeffi cients of the matrix pencil to ensure the accuracy of the identi fied parameters,since the existing eigenvalue solution of the MPM ignores the angular frequency conjugation constraints of the two fundamental modes and two oscillation modes.Then,the identification and recovery of bad data are proposed by uti lizing the difference in temporal continuity of the synchropha sors before and after noise reduction.The proposed parameter identification is verified with synthetic,simulated,and actual measured phase measurement unit(PMU)data.Compared with the existing MPM,the improved MPM achieves better accuracy for parameter identification of each component in SSOs,better real-time performance,and significantly reduces the effect of bad data.

High Impedance Fault Detection Based on Attention Mechanism and Object Identification

Detection of high impedance faults(HIFs)has been traditionally a main challenge in the protection of distribution systems,since they do not generate enough current to be reliably detected by conventional over-current relays.Data-based methods are alternative HIF detection methods which avoid threshold settings by training a classification or regression model.However,most of them lack interpretability and are not compatible with various distribution networks.This paper proposes an object detection-based HIF detection method,which has higher visualization and can be easily applied to different scenarios.First,based on the analysis of HIFs,a Butterworth band-pass filter is designed for HIF harmonic feature extraction.Subsequently,based on the synchronized data provided by distribution-level phasor measurement units,global HIF feature gray-scale images are formed through combining the topology information of the distribution network.To further enhance the feature information,a locally excitatory globally inhibitory oscillator region attention mechanism(LEGIO-RAM)is proposed to highlight the critical feature regions and inhibit useless and fake information.Finally,an object detection network based You Only Look Once(YOLO)v2 is established to achieve fast HIF detection and section location.The obtained results from the simulation of the proposed approach on three different distribution networks and one realistic distribution network verify that the proposed method is highly effective in terms of reliability and generalization.

Dynamic Load Restoration Considering the Interdependencies Between Power Distribution Systems and Urban Transportation Systems

After a major outage,mobile emergency resources(MERs)can be dispatched via the transportation system(TS)for service restoration to critical loads in the power distribution system(PDS).In this case study,the efficiency of service restoration in the PDS is associated with the traffic efficiency of the TS,and vice versa,because the PDS and TS are mutually coupled through traffic lights and MERs.This paper proposes a service restoration method considering interdependency between the PDS and TS,which is formulated as a mixed-integer linear program(MILP).The objective includes maximizing the efficiency of both PDS restoration and TS.By solving the MILP,the dynamic load restoration and MER dispatch strategies can be obtained.For the PDS,the availability of MERs,including mobile sources and repair crews,relates to their dispatch in the TS,and their relationship is formulated as mathematical models.For the TS,the dynamic traffic flow is modeled using the cell transmission model and the effect of traffic lights is considered.Case studies validate the effectiveness of the proposed method.

A new coordinated backup protection scheme for distribution network containing distributed generation

This paper proposes a new backup protection scheme,named coordinated backup protection(CBP)scheme,for distribution networks containing distributed generation.The proposed protection scheme takes into account the issues faced by traditional backup protection,such as difficulty in setting parameters and complex cooperation,and considers the features of distribution networks,such as changeable power flow because of high penetration of distributed generation sources and insufficient measuring quantities.The CBP scheme includes two aspects:coordinated substation protection and regional master substation protection,who also work as nearby backup protection and remote backup protection respectively.The two protections support each other by local information coordination and regional information sharing,in order to improve the reliability of fault identification.The configuration principles and performances of the proposed backup protection scheme are addressed in the paper.Different fault conditions in the IEEE 14-node system have been used to illustrate and verify the feasibility of the CBP scheme.

Real-time Synchrophasor Data Compression Technique with Phasor Interpolation and Extrapolation

To completely eliminate the time delays caused by phasor data compressions for real-time synchrophasor applications,a real-time synchrophasor data compression(RSDC)is proposed in this paper.The two-way rotation characteristic and elliptical trajectory of dynamic synchrophasors are introduced first to enhance the compressions along with a fast solving method for elliptical trajectory fitting equations.The RSDC for phasor data compression and reconstruction is then proposed by combining the interpolation and extrapolation compressions.The proposed RSDC is verified by both the actual phasor measurement data recorded in a two-phase short-circuit incident and a subsynchronous oscillation incident,and the synthetic dynamic synchrophasors.It is also compared with two previous real-time phasor data compression techniques,i.e.,phasor swing door trending(PSDT)and exception and swing door trending(SDT)data compression(ESDC).The verification results demonstrate that RSDC can achieve significantly higher compression ratios for offline applications with the interpolation and the zero-delay phasor data compression with the extrapolation for real-time applications simultaneously.

Review of protection and fault handling for a flexible DC grid

With the development of power electronics technology,the flexible DC grid will play a significant role in promoting the transformation and reformation of the power grid.It is immune to commutation failure and has high flexibility in power control and renewable energy grid integration.However,the protection and fault handling technology for a flexible DC grid is a big challenge because of the limited overcurrent capability of the converters.This paper summarizes the development of the flexible DC grid,and analyzes the fault characteristics in detail.Next,the applicability,advantages and disadvantages of the existing protection principle,fault isolation and recovery schemes are reviewed.Finally,the key problems and development trend of the future flexible DC grid are pointed out and forecasted respectively.

Probabilistic load flow method considering large-scale wind power integration

The increasing penetration of wind power brings great uncertainties into power systems,which poses challenges to system planning and operation.This paper proposes a novel probabilistic load flow(PLF)method based on clustering technique to handle large fluctuations from large-scale wind power integration.The traditional cumulant method(CM)for PLF is based on the linearization of load flow equations around the operation point,therefore resulting in significant errors when input random variables have large fluctuations.In the proposed method,the samples of wind power and loads are first generated by the inverse Nataf transformation and then clustered using an improved K-means algorithm to obtain input variable samples with small variances in each cluster.With such pre-processing,the cumulant method can be applied within each cluster to calculate cumulants of output random variables with improved accuracy.The results obtained in each cluster are combined according to the law of total probability to calculate the final cumulants of output random variables for the whole samples.The proposed method is validated on modified IEEE 9-bus and 118-bus test achieve a better performance with the consideration of both traditional CM,2 m+1 point estimate method(PEM),Monte Carlo simulation(MCS)and Latin hypercube sampling(LHS)based MCS,the proposed method can achieve a better performance with the consideration of bothcomputational efficiency and accuracy.

Development and research on integrated protection system based on redundant information analysis

Facing the growth of energy demand and the worldwide interests in renewable energy sources,smart grid has been proposed in order to accommodate the needs of power grid development.In China,digital substations have been widely applied.Moreover,as the worldwide interest and development in smart grid have increased significantly,the digital information availability and communication capability of modern substation have been improved.Different with traditional substation protection configuration based on local information,Integrated Protection(IP)is used to denote the integration of several protective devices for multiple power equipment within the substation into one protective relay,obtaining all the real time information of the substation by communication network.The analysis of sharing information and cooperation among different protection functions helps to realize more reliable and sensitive fault detection.This paper describes several different integrated protection schemes and their respective advantages and disadvantages.The principles and functions applied in integrated protection systems are addressed to provide an overview of the current state of the technology.A new coordinated protection system based on inter-substation information is proposed and simulation study is discussed to verify the improved reliability and sensitivity.

An End-to-end Transient Recognition Method for VSC-HVDC Based on Deep Belief Network

Lightning is one of the most common transient interferences on overhead transmission lines of high-voltage direct current(HVDC)systems.Accurate and effective recognition of faults and disturbances caused by lightning strokes is crucial in transient protections such as traveling wave protection.Traditional recognition methods which adopt feature extraction and classification models rely heavily on the performance of signal processing and practical operation experiences.Misjudgments occur due to the poor generalization performance of recognition models.To improve the recognition rates and reliability of transient protection,this paper proposes a transient recognition method based on the deep belief network.The normalized line-mode components of transient currents on HVDC transmission lines are analyzed by a deep belief network which is properly designed.The feature learning process of the deep belief network can discover the inherent characteristics and improve recognition accuracy.Simulations are carried out to verify the effectiveness of the proposed method.Results demonstrate that the proposed method performs well in various scenarios and shows higher potential in practical applications than traditional machine learning based ones.

Optimization of Distributed Integrated Multi-energy System Considering Industrial Process Based on Energy Hub

As a typical scenario of distributed integrated multi-energy system(DIMS),industrial park contains complex production constraints and strong associations between industrial productions and energy demands.The industrial production process(IPP)consists of controllable subtasks and strict timing constraints.Taking IPP as a control variable of optimal scheduling,it is an available approach that models the IPP as material flow into an extension energy hub(EH)to achieve the optimization of industrial park.In this paper,considering the coupling between the production process and energy demands,a model of IPP is proposed by dividing the process into different adjustable steps,including continuous subtask,discrete subtask,and storage subtask.Then,a transport model of material flow is used to describe the IPP in an industrial park DIMS.Based on the concept of EH,a universal extension EH model is proposed considering the coupling among electricity,heat,cooling,and material.Furthermore,an optimal scheduling method for industrial park DIMS is proposed to improve the energy efficiency and operation economy.Finally,a case study of a typical battery factory is shown to illustrate the proposed method.The simulation results demonstrate that such a method reduces the operation cost and accurately reflects the operation state of the industrial factory.

Distributed Protection for Smart Substations Based on Multiple Overlapping Units

Taking advantage of the information sharing mechanism in smart substations,a distributed protection based on multiple overlapping units is introduced in this paper.The area division and the construction of protection units are studied based on the principle of differential protection.Mutual perception and information interaction among units,calculation with multisource information and coordinated protection schemes are proposed to improve the reliability and adaptability of the substation protection system.A multi agent system(MAS)approach is used to model the units’working process in various situations,such as communication failure and sampled data failure.Test results demonstrate that the method can accelerate the backup protection as well as reduce the power-off range.