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Control scheme of hexagonal modular multilevel direct converter for offshore wind power integration via fractional frequency transmission system

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Journal of Modern power Systems and Clean Energy 2018年第1期6卷 168-180页

作者： Yongqing MENG Bo LIU Huiyong LUO Shuonan SHANG Haitao ZHANG Xifan WANG School of electrical Engineering Xi'an Jiaotong University State Grid Sichuan Provincial electric power corporation Tianfu New Area power Supply Company Henan electric power Research Institute

A fractional frequency transmission system(FFTS)is a promising solution to offshore wind power integration,for which the hexagonal modular multilevel converter(Hexverter)is an attractive choice for power *** Hexverter has recently been proposed to directly connect two three-phase systems of different frequencies and voltage amplitudes,with only six branches in the FFTS in that *** paper examines for the first time the control scheme of the Hexverter when applied to offshore wind power integration via a ***,the frequency-decoupled mathematical model of the Hexverter is deduced by introducing the double dq *** the branch energy of the Hexverter is analyzed in detail and the reactive power constraint equation is *** corresponding control scheme is thoroughly discussed,including the inner loop current control,the outer loop voltage control in both grid-connected mode and passive mode,and a novel optimization method to minimize the circulating current in the ***,a simulation model of offshore wind power integration via a 4-terminal FFTS based on the Hexverter is built in MATALB/Simulink to verify the feasibility of Hexverter and the effectiveness of the control scheme proposed in this paper.

关键词： Hexagonal modular multilevel converter(Hexverter) Offshore wind power integration Fractional frequency transmission system(FFTS) Control scheme Circulating current optimization

Non-permanent Pole-to-pole Fault Restoration Strategy for Flexible DC Distribution Network

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Journal of Modern power Systems and Clean Energy 2021年第6期9卷 1339-1351页

作者： Zainan Li Jiandong Duan Wenchao Lu Xiaotong Du Wei Yang Siyu Tu School of electrical Engineering Xi’an University of Technology State Key Laboratory of Alternate electrical power System with Renewable Energy Sources(North China electric power University) State Grid Hubei maintenance Company

As the structures of multiple branch lines(MBLs)will be widely applied in the future flexible DC distribution network,there is a urgent need for improving system reliability by tackling the frequent non-permanent pole-to-pole(P-P)fault on distribution lines.A novel fault restoration strategy based on local information is proposed to solve this *** strategy firstly splits a double-ended power supply network into two single-ended power supply networks through the timing difference characteristics of a hybrid direct current circuit breaker(HDCCB)entering the ***,a method based on the characteristic of the transient energy of fault current is proposed to screen the faulty branch line in each single-ended power supply ***,a four-terminal flexible DC distribution network with MBLs is constructed on PSCAD to demonstrate the efficacy of the proposed *** factors such as noise,fault location,and DC arc equivalent resistance are considered in the simulation model for *** results prove that the proposed strategy for fault restoration is effective,and features high performance and scalability.

关键词： Flexible DC distribution network pole-to-pole fault fault restoration strategy reclosing strategy transient energy of fault current

Architecture,Key Technologies and Applications of Load Dispatching in China power Grid

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Journal of Modern power Systems and Clean Energy 2022年第2期10卷 316-327页

作者： Yu Dong Xin Shan Yaqin Yan Xiwu Leng Yi Wang State Grid corporation of China Beijing 100031China NARI Group corporation(State Grid electric power Research Institute) Nanjing 211000China

With the development of renewable energy and the changes in the characteristics of power grid,it is becoming increasingly difficult to balance power supply and demand in space and *** addition,the requirement for improved dispatching capability of power grid is ***,the potential of flexible load dispatching should be realized,which can promote the large-scale consumption of renewable energy and the construction of new power *** on the analysis of existing load dispatching studies and the differences in the characteristics of domestic and foreign load dispatchings,a technical architecture and several key technologies are proposed for load resources to participate in power grid dispatching under the new situation,i.e.,the autonomous collaborative control system of load *** system implements the multi-layer coordinated control of main,distribution and micro grids(load aggregators).Adjustable load resources are aggregated through an aggregator operation platform and connected with a dispatcher load regulator platform to realize real-time data interaction with dispatching agencies as well as the monitoring,con-trol,and marketing of *** supports the load resources to participate in network-wide dispatching optimization via continuous power *** key technologies such as the control mode,load modeling,dispatching strategy,and safety protection are also *** the closed-loop control of orderly charging piles and energy storage clusters in the North China power Grid,the feasibility of the proposed architecture and key technologies is *** route has successively supported multiple adjustable load aggregators to partici-pate in the ancillary services market of North China power Grid for ***,the technical challenges of load resources participating in power grid dispatching under the dual carbon goals are discussed and prospected.

关键词： Automatic power control(APC) load modeling load dispatching renewable energy accommodation situation awareness.

Improving IEC thermal model for oil natural air natural transformers using optimised parameters based on dynamic simulation

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High Voltage 2024年第1期9卷 217-229页

作者： Lijing Zhang Yingting Luo Gehao Sheng Zizhan Ni Xiuchen Jiang Department of electrical Engineering Shanghai Jiao Tong UniversityShanghaiChina electric power Research Institute of Guangdong power Grid corporation GuangzhouChina

Accurate assessment of hot-spot temperature is essential for the safe operation of power *** dynamic thermal models cannot estimate hot-spot temperature accurately since some input parameters are roughly determined by transformer capacity and cooling mode while ignoring the effect of winding structure,tank dimensions,and material physical *** improve the accuracy of temperature assessment,empirical parameters of the IEC thermal model including thermal constants,winding and oil exponents are optimised with the help of numerical simulation in this *** on energy conservation and heat transfer theory,a computational fluid dynamic(CFD)model of a transformer in oil natural air natural(ONAN)cooling mode is *** CFD model simulates the entity's structure,sizes,and multi-stage heat dissipation processes realistically,so it can more precisely calculate the dynamic hot-spot *** to the simulated temperature curves at different operating conditions,the thermal constants and oil exponent are estimated using non-linear regression,and the winding exponent is optimised using linear regression.A case study is conducted on an ONAN *** shows the improved IEC model with optimised parameters can more accurately evaluate hot-spot temperature,and the absolute error is decreased by 2.4 K(38.7%)compared with traditional thermal models.

关键词： temperature properties. thermal

Influence of Nano-Al Concentrates on the Corrosion Resistance of Epoxy Coatings

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Journal of Materials Science & Technology 2013年第4期29卷 353-358页

作者： Yongchun Liang Fu-Chun Liu Ming Nie Shuyan Zhao Jiedong Lin En-Hou Han The electric power Research Institute of Guangdong power Grid corporation State Key Laboratory for Corrosion and Protection Institute of Metal ResearchChinese Academy of Sciences

A two-stage process was used to produce nano-composite epoxy coatings. The first step involved preparing nano-AI concentrates with high concentration and low viscosity, and the second step produced nano- composite epoxy coatings by mixing the nano-AI concentrates and epoxy resin. Later, the coating was examined with immersion and salt spray tests. The coatings were characterized by electrochemical impedance spectroscopy （EIS）, scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. The results showed that the 5% nano-AI significantly improves the corrosion resistance of the coatings. There are two effects of nano-AI on the coating. Nano-AI is corroded initially to protect the substrate from corrosion, and then the aluminum oxide and aluminum hydroxide were produced after corrosion of nano-AI, which hindered the transmission of corrosion fluid into the coatings.

关键词： Nanometer metal Organic coatings Salt spray test Electrochemical impedance spectroscopy

An Efficient Method for Identifying the Inactive Transmission Constraints in a Network-Constrained Unit Commitment

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CSEE Journal of power and Energy Systems 2023年第6期9卷 2366-2373页

作者： Ziming Ma Haiwang Zhong Qing Xia Chongqing Kang Qiang Wang Xin Cao the State Key Laboratory of power Systems and the Department of electrical Engineering Tsinghua UniversityBeijing 100084China State Grid hebei electric power Company Shijiazhuang 050000China

Network-constrained unit commitment(NCUC)is one of the most widely used applications in power system and electricity market *** to empirical evidence,some of the transmission constraints in a NCUC are *** and eliminating these inactive constraints can improve the *** this paper,an efficient method is first proposed for identifying the inactive transmission *** physical and economic insights of NCUC are carefully considered and *** the generating costs and power transfer distribution factor(PTDF)are *** only redundant constraints but also non-binding constraints can be identified via the proposed *** acceleration method that combines relaxation-based neighborhood search and improved relaxation inducement is proposed for further reducing the computation *** case study shows that the proposed method can significantly reduce the number of transmission constraints and substantially improve the efficiency of NCUC without impacting the optimality.

关键词： Inactive transmission constraints improved relaxation inducement(IRI) network-constrained unit commitment(NCUC) relaxation-based neighborhood search(RBNS)

Wind speed equalization-based incoming wind classification by aggregating DFIGs

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Journal of Modern power Systems and Clean Energy 2013年第1期1卷 42-48页

作者： Zhaojun MENG Feng XUE Xueming LI Group corporation(State Grid electric power Research Institute) Nanjing 210003JiangsuChina

With the development of wind energy,it is necessary to develop equivalent models to represent dynamic behaviors of wind farms in power *** equivalent wind method is investigated for the aggregation of doubly-fed induction generator wind *** detailed procedures for the calculation of equivalent wind are *** necessity of classifying incoming winds is *** improve the performances of the method,incoming winds are classified according to mean wind speeds and positive/negative semi-variances of wind speeds,and a group of turbines with similar incoming winds are aggregated *** effectiveness of the method is verified through simulations in MATLAB/Simulink.

关键词： DFIG power curve Equivalent wind Aggregated wind turbine

Simulation analysis on policy interaction effects between emission trading and renewable energy subsidy

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Journal of Modern power Systems and Clean Energy 2013年第2期1卷 195-201页

作者： Jie HUANG Feng XUE Xiaofang SONG NARI Group corporation(State Grid electric power Research Institute) Nanjing 210003China

Greenhouse gas emission regulation and renewable energy promotion policies have been implemented in many *** these two kinds of regulation policies have complex interactions between each other,and can either enhance or reduce the overall emission reduction *** not well tuned,these regulation policies may deviate from their original intention and lead to unnecessary social ***,the policy effectiveness,cost effectiveness,and dynamic efficiency of different policy mixtures between emission trading and renewable energy subsidy are studied based on a novel dynamic simulation platform of power economy and power *** results show that these two kinds of regulation policy can coexist,but a good coordination between the emission trading and the renewable energy subsidy can achieve better emission reduction outcomes.

关键词： Dynamic simulation Energy conservation Emission reduction Emission trading Renewable energy Policy effectiveness

A rapid method for determination of acid value in transformer oil by PPy modified electrode

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Journal of Central South University 2014年第6期21卷 2202-2207页

作者：熊英何德良冯勇周舟常新园刘芙蓉 College of Chemistry and Chemical Engineering Hunan University Hunan electric power corporation Research Institute

A polypyrrole-modified glassy carbon electrode （PPy/GC electrode） was prepared and its electrocatalytic behavior towards naphthoquinone in the presence of acid was characterized by linear sweep voltammetry （LSV）. A well-defined new reduction peak appeared at a more positive potential than the original reduction peak. The new reduction peak current was linearly related to the acid value （AV） of oil. Based on it, a rapid electrochemical method for determining AV of transformer oil was developed using PPy/GC electrode. A working curve was obtained in the AV range of 0.01 to 0.40 mg（KOH）.g^-1, with a sensitivity of 39.42 μA0.5/（mg（KOH）.g-l） and the detection limit of 0.0014 mg（KOH）.g^-1 （signal-to-noise ratio is 3, standard deviation is 2.247%）. Moreover, the proposed method has been successfully applied to AV determination of several transformer oil samples with advantages of rapidness, high sensitivity and accuracy compared to the conventional method.

关键词： acid value voltammetry polypyrrole-modified electrode transformer oil