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A new method of frequency-dependent network equivalence for power system

Science China(Technological Sciences) 2012年第7期55卷 1894-1907页

作者： LIN JiKeng YAN YiPeng PU TianJiao LUO ShanShan LIU Tao ZHENG WeiHong WANG XuDong Key Laboratory of Power System Simulation and Control of Ministry of Education(Tianjin University) Tianjin 300072China China Electric-Power Research institute Beijing 100192China Schneider Electric Co. Ltd(China)Shanghai BranchShanghai 200000China Tianjin Electrieal Power Corperation Tianjin 300010China

Electromagnetic transient simulation for large-scale power system is a time-consuming problem.A new frequency-dependent equivalence method is presented in the paper,which might significantly accelerate power system electromagnetic transient *** the method,an effective algorithm is designed to directly transfer the port admittance determinant of external system's mixing matrix into admittance rational function;and the step-by-step strategy for the equivalence of actual large system is put forward,which further reduces the calculation quantities ***,the study of multiple real root pole characteristics of admittance transfer function of two-port network is performed and a proposition is *** on the proposition and residue theorem,the equivalence system for external system corresponding to the admittance rational function is *** computation complexity of the step-by-step equivalence method is about o(┌n/np×T┐)(┌┐ is upper integral operation,n is the total buses number of external system,N P is the total buses number of single step equivalence network,T is single step equivalence time),which indicates that the computation complexity of the method proposed has nearly linear relationship with the buses number of external system,and the method proposed has satisfactory computation *** the mixing matrix of external system includes all the information of external system,therefore,port admittance rational function derived from it can reflect its full frequency characteristic and the equivalence network achieved has high equivalence ***,since the port rational function is gained at the condition of the external system without source,which equals stable passive network,it could not show any unstable pole and need not extra measure to make the equivalence system *** test results of the samples and comparison with other methods demonstrate that the new method proposed is valid and effective.

关键词： equivalence method electromagnetic transient simulation frequency-dependent rational functions mixing matrix

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A schedule power flow auto generating technology in day-ahead security validation

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Dianli Xitong Zidonghua/Automation of Electric power systems 2012年第20期36卷 68-73页

作者： Lin, Yi Sun, Hongbin Wu, Wenchuan Yu, Jun Zhang, Boming State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China National Electric Power Dispatching and Communication Center Beijing 100031 China

Formulation of day-ahead operation schedule for large-scale power grid requires security validation, including static security, dynamic and transient stability. It is an important and basic task for day-ahead security validation to generate an AC power flow that satisfies the demand of the schedule. A new method of generating the day-ahead schedule power flow is proposed, which consists in dividing the problem into two subproblems-the active subproblem and the reactive subproblem. The inconsistency of various kinds of schedule data is coordinated by solving the active subproblem, while a rational voltage distribution is achieved by solving the reactive subproblem. Both of the two problems are formulated as optimization models with constraints satisfied and are solved with an interior point algorithm. Numerical test results on the testing system and real power systems show that the method is capable of providing rational day-ahead schedule power flow. © 2012 state Grid Electric power Research Institute Press.

关键词： Numerical methods

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Battery energy storage system load shifting control based on real time load forecast and dynamic programming

Battery energy storage system load shifting control based on...

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IEEE International Conference on Automation Science and Engineering (CASE)

作者： Guannan Bao Chao Lu Zhichang Yuan Zhigang Lu State Key Laboratory of Control and Simulation of Power System and GenerationEquipments Tsinghua University Beijing China Electric Power Research Institute China Southern Power Grid Guangzhou China

Battery energy storage system (BESS) is one of the key technologies for smart grid and load shifting is one of the fundamental functions of BESS. BESS load shifting performance is determined by the availability of accurate load curves and optimization approaches. In this paper, a real-time control strategy based on load forecast and dynamic programming methods is presented. The predicted load curve is updated on-line through regress forecasting. The proposed optimization model is solved by using dynamic programming technique. The objective is peak shaving and prolonging the battery lifetime, and the constraints considered include battery state-of-charge (SOC), cycling times per day, converter capacity and step power. The above control strategy was successfully applied to the 5MW*4hour lithium-Ion BESS demonstration project in Biling substation, China Southern power Grid. The simulation results based on the actual load data of Biling substation demonstrate the effectiveness.

关键词： Batteries Optimization Discharges (electric) Real-time systems Load forecasting Load modeling US Department of Defense

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power transformer condition assessment by on-line monitoring and trend analysis

Power transformer condition assessment by on-line monitoring...

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IASTED International Conference on power and Energy systems and Applications, PESA 2012

作者： Xie, Qijia Gao, Shengyou Zhang, Hailong Dai, Wen Ruan, Ling Nie, Dexin Lu, Wenhua Key Laboratory of High-Voltage Field-Test Technique of SGCC Hubei Electric Power Testing and Research Institute Wuhan China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China State Grid Electric Power Research Institute Wuhan China School of Electrical Engineering Wuhan University Wuhan China

power transformer condition assessment is the basi of condition-based maintenance and plays a very important role in carrying assets management and risk assessment for power system. As the heart of transmission and transformation system, power transformer's condition has close relation with many factors, such as the production quality of itself, operation environment and so on. This paper analyzes some variables which could represent the transformer's condition, including the data from preventative test, factory test and commission test, diagnostic test, on-line detection and monitoring, routine inspection, operation history, family defection and environment information. Some parameters which have representation are chosen as the condition variables. Artificial neuron network (ANN) and Dempster-Shafer (D-S) evidence theory are adopted to form the multiparameter information fusion condition assessment model. Besides the static value, the change trends of some parameters are considered as an independent evidence section. Cooperating with on-line monitoring, it will be helpful to improve the accuracy and efficiency of condition assessment.

关键词： power transformers

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Multi-source information based current matching state estimation for distribution network

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Dianli Xitong Zidonghua/Automation of Electric power systems 2012年第16期36卷 53-57页

作者： Ju, Yuntao Wu, Wenchuan Cheng, Xueqi Zhang, Boming Sun, Hongbin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China Weifang Power Supply Bureau Shandong Provincial Power Corporation Weifang 261000 China

By taking into account the real-time measurement with low redundancy and of only partial current in distribution systems and referring to the quasi-real-time current measuring data of the metering system, the current matching technique is proposed to solve the distribution network state estimation. The matching current equations in the sense of optimal estimation and its systematic solution are deduced. Based on the assumption that the load power factor is stable, a quasi-real-time measurement generating method is proposed for loads. With boundaries demarcated by real-time current measurement, the distributed network is divided into several measured areas and current matching state estimation is made for each area. Numerical tests and results of an actual system show that the method proposed can satisfy the real-time application demand of the distribution system. ©2012 state Grid Electric power Research Institute Press.

关键词： state estimation

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Optimal allocation of distributed generators in a distribution network using adaptive multi-objective particle swarm optimization

Optimal allocation of distributed generators in a distributi...

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2011 International Conference on Electrical, Information Engineering and Mechatronics, EIEM 2011

作者： Cheng, Shan Chen, Min-You Fleming, Peter J. Li, Xia State Key Laboratory of Power Transmission Equipment and System Security and New Technology School of Electrical Engineering Chongqing University Chongqing China Department of Automatic Control and Systems Engineering University of Sheffield Sheffield United Kingdom

ISBN: (纸本)9781447124665

This study presents the optimal allocation of distributed generators (DGs) in distribution network based on an adaptive multi-objective particle swarm optimization (AMPSO). In order to enable the DGs to make the best contribution to the distribution network, a multi-objective optimization model addressing power loss and a voltage stability index (VSI) is constructed, in which the capacity factor of DGs is taken into consideration. In the AMPSO, some adaptive techniques including the use of dynamically changing inertia weight, time-varying acceleration coefficients, mutation operation and circular crowding sorting have been integrated to improve the convergence and the diversity performance of the algorithm. The proposed algorithm has been used to determine the optimal allocation of DGs in a IEEE 33-bus distribution network. simulation results show that the proposed method can identify the optimal solutions with a good tradeoff between the power loss and the VSI. © 2012 Springer-Verlag London Limited.

关键词： Multiobjective optimization

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Study on Conducted Interference and Radiated Interference of Buck-Boost Converter in Electric Automobile

Study on Conducted Interference and Radiated Interference of...

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FISITA 2012 World Automotive Congress--Volume 6:Vehicle Electronics

作者： Jian Wang Youqun Zhao Liguo Zang Wei Wang College of Energy&Power Engineering Nanjing University of Aeronautics and Astronautics State Key Laboratory of Automotive Simulation and Control

Buck-boost converter is an important component of electric automobile,it is an important interference source in electric automobile,the study of the interference source is very important to restrain *** buck-boost converter in continuous conduction mode(CCM) is established by using circuit simulation software *** to the request of GB18655-2002,the simulation study on common-mode conducted interference,differential-mode conducted interference and far-field radiated interference of buck-boost converter are *** commonmode current radiation of buck-boost converter is simplified as an electric dipole radiation mode and the differential-mode current radiation is simplified as a rectangular loop *** order to improve the electromagnetic compatibility of buckboost converter in electric automobile,some measures to reduce the conducted interference and the radiated interference are proposed.

关键词： Buck-boost converter Conducted interference Radiated interference PSPICE Electric automobile

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INFLUENCES OF BREAKDOWN CHARACTERISTICS OF DISCONNECT SWITCH GAP ON RESIDUAL VOLTAGE

INFLUENCES OF BREAKDOWN CHARACTERISTICS OF DISCONNECT SWITCH...

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The ⅪⅩ International Conference on Gas Discharges and Their Applications

作者： YUE GONGCHANG GUAN YONGGANG LIU WEIDONG CHEN WEIJIANG LI ZHIBING State Key Lab of Control and Simulation of Power System and Generation Equipments Department of Electrical EngineeringTsinghua University State Grid Corporation of China China Electric Power Research Institute

The very fast transient overvoltages(VFTO) are generated during operation of disconnect switch (DS) of gas insulated switchgear(GIS). After the opening operation of DS,the load side busbar is left at a residual *** residual voltage is determined by the opening phase and the breakdown characteristics of SF6 gap of DS. This study obtains the breakdown characteristic of the test DS,including the dielectric strength recovery speed and polarity effect factor of gap of testing *** the stochastic property of DS opening phase,the opening process of DS is simulated by computer under different dielectric strength recovery speeds and polarity effect *** results show that the dielectric strength recovery speed and polarity effect factor have big influences over the residual *** proper value of dielectric strength recovery speed and polarity effect factor could make the residual voltage minor

关键词： simulation INFLUENCES OF BREAKDOWN CHARACTERISTICS OF DISCONNECT SWITCH GAP ON RESIDUAL VOLTAGE

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A compact coaxial gas filled switch

A compact coaxial gas filled switch

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IEEE International Conference on Plasma Science (ICOPS)

作者： Xiaobing Zou Xinjing Cai Xinxin Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China College of Electrical Engineering Northeast Dianli University Jilin China

Summary form only given. As we know, the risetime of the output voltage of a pulse power generator is mainly determined by the performance of the main discharge switch. Recently, to calibrate nanosecond pulse voltage dividers, A nanosecond pulse generator with an output voltage of 2–10 kV was constructed. The generator was composed of a DC charging source, a 50 Ohm coaxial cable as a pulse forming line (PFL), a self-breakdown coaxial gas filled switch, a 50 Ohm coaxial cable as pulse transmission line (PTL), and a matched load. The gas filled switch with two plate electrodes was made as compact as possible to reduce the switch inductance. The gap distance of the switch is fixed to be ∼0.5mm and filled with pressurized nitrogen gas. Extensive tests were made to measure the risetime of the output voltage as the filled gas pressure changed from 0.1MPa ∼0.6Mpa. the averaged risetime of the output voltage is ∼14 ns as the switch gas pressure is set to be 0.1MPa, while the risetime is ∼1.5 ns as the gas pressure increased to 0.6MPa. A CCD camera was used to take pictures of the discharge arc between the main electrodes. As the gas pressre is ∼0.1Mpa, only one single discharge channel was observed. While the gas pressure is above 0.5Mpa, the switch usually breaks down in multi-channel mode, which would result in a low switch inductance and a faster risetime of the output voltage.

关键词： Switches Educational institutions Discharges (electric) Voltage measurement Switching circuits Electrical engineering Generators

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Effects of SiO2 particles on surface charge of epoxy nanocomposites

Effects of SiO2 particles on surface charge of epoxy nanocom...

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International Conference on High Voltage Engineering and Application, ICHVE

作者： B. X. Du Li Wang J. W. Zhang Yong Liu Y Gao Key Laboratory of Power System Simulation and Control of Ministry of Education Department of Electrical Engineering School of Electrical Engineering and Automation Tianjin University TJU Tianjin China

Epoxy used as insulating material in electronic and electrical devices plays an important role in system reliability. Addition of nanoparticles into epoxy can improve the insulating properties compared with undoped material. However, due to the change of the material structure, trap characteristics and charge behaviors are altered as a consequence. This possibly leads to a great risk of electric field distortion and discharge that degrades the insulation. From the viewpoint of safety, it is necessary to investigate the charge behavior on epoxy nanocomposites. This paper presents study aimed at clarifying the effect of nano-filler content on surface charge accumulation and decay behaviors of epoxy nanocomposites with SiO 2 particles. Samples were prepared by dispersing nano-scale SiO 2 into epoxy by mixing with shear force. Corona charging tests were performed at room temperature with a relative humidity of ~ 40%. The charge distribution was measured by means of an electrostatic voltmeter. Obtained results show the dependence of the accumulated charge as well as the charge decay rate upon the concentration of SiO 2 , varying as a function of the charge polarity, charging time and charging voltage. It is suggested that the charge dynamics is dependent upon the characteristics of localized surface states that are altered by the nanoparticles.

关键词： Surface charging Nanocomposites Nanoparticles Electrodes Dielectrics Corona Space charge

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