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A non-iterative affine arithmetic methodology for interval power flow analysis of transmission network

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2013年第19期33卷 76-83页

作者： Ding, Tao Bo, Rui Guo, Qinglai Sun, Hongbin Wu, Wenchuan Zhang, Boming State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Midwest ISO St. Paul 55108 United States

power flow exhibits uncertainty when power injections randomly fluctuate. The variables of power flow problem are correlated through the constraints set forth by power flow equations. Affine arithmetic can effectively overcome the correlation and therefore is adopted in this paper. In order to improve the computational efficiency, non-iterative method was proposed, which can transform the interval power flow problem into optimization problems. Linear programming, nonlinear programming and quadratic programming optimization models were established to obtain intervals of nodal voltage magnitude, phase angle, branch active power and reactive power, respectively. simulation results of 9-bus and 57-bus test system show that the power flow interval obtained by the proposed algorithm is nearly the same as that by iterative algorithms, whereas the branch power flow results are better. The interval power flow problem can be solved quickly and efficiently with time complexity approximately O(m3). As well, parallel computing can be implemented to achieve promising improvement in computation time. © 2013 Chinese Society for Electrical Engineering.

关键词： Quadratic programming

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Influence of annealing method on the space charge properties in polyethylene

Influence of annealing method on the space charge properties...

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Conference on Electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Ninghua Wang Yuanxiang Zhou Hongbin Liu Bin Gao Xidong Liang Zhicheng Guan T. Takada State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Electronic Measurement Laboratory Musashi Institute of Technology Tokyo Japan

In this paper, high-density polyethylene (HDPE) films were prepared by three kinds of annealing methods which were different in cooling speed. The crystallinity of those HDPE samples were measured and compared. A high DC voltage was applied to the samples and the space charge formed was measured. Homo-charges were found in samples that were applied with a negative high voltage. The space charge properties were discussed, based on crystallinity. From these results, it is found that the space charge formed in samples cooled at high speed is more than that of the samples cooled at normal and low speed.

关键词： Annealing Space charge Polyethylene Voltage Current measurement Charge measurement Conducting materials Crystallization Morphology laboratories

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Skin Effect and Eddy Current Loss in Electrical Steel Sheets under Applied Excitation Fields.

Skin Effect and Eddy Current Loss in Electrical Steel Sheets...

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International Conference on Magnetics (INTERMAG)

作者： J. Li Q. Yang S. Wang Y. Li State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin China

Body: By applying electromagnetic diffusion equation, skin effect in electrical steel sheets in the condition of alternating excitation is analyzed based on Maxwell electromagnetic field theory. Due to skin effect is more significant mainly at high frequency, non-dimensionalized treatment for the diffusion equation is produced and eddy current loss is calculated by considering or not skin effect, respectively. Meanwhile, broadband magnetic losses and separation of typical electrical steel are obtained by using a 3-D magnetic properties testing system to bring to light the emergence of skin effect under rotational excitation. The simplification of magnetic constitutive equation is proposed and introduced into the diffusion equation, which is solved by employing finite elements coupled to Fredholm's equation. An approximate expression for the rotational eddy current loss component with skin effect is eventually written. The simulations show that due to the influence of skin effect, non-uniform distribution of induction flux density within electrical steel sheets will become more and more significant, the fl ux density and fi eld intensity nearby the surface are larger than that in the centre of the sheets [1, 2]. And with increasing of alternating excitation frequency, the inhomogeneity of induction flux density will be extended and growing more inhomogeneous, due to the smaller skin depth and a small increase of anomalous loss in the total core losses, as shown in Fig. 1.2. Therefore, alternating eddy current loss P as functions of the peak mean alternating flux density B mamean and the alternating excitation frequency f a can be deduced as follows: limv→∞P ae (B ma_mean f a )=[2ω a (B ma_mean ) 2 /3ρμν 2 =(σπ 2 d 2 /3ρ)(f a ) 2 (B ma_mean ) (no skin effect)[W/kg] (1) limν→0 P ae (B ma_mean f a )=[4ω a (B ma_mean ) 2 /ρμν=(4σ 1/2 π 3/2 d/ρμ 1/2 )(f a ) 3/2 (Bma_mean) 2 (considering significant skin effect) [W/kg] (2) where, ω a is the angular frequency; v = 2δ

关键词： Magnetics Conferences

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An Improved Virtual Resistance Damping Method for Grid-Connected Inverters with LCL Filters

An Improved Virtual Resistance Damping Method for Grid-Conne...

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2011 IEEE Energy Conversion Congress and Exposition (ECCE 2011)

作者： Yi Lei Zhengming Zhao Fanbo He Sizhao Lu Lu Yin State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University 100084 Beijing P. R. China

ISBN: (纸本)9781457705427;9781457705410

In renewable energy generations, LCL filters are commonly used to connect in series with the output ports of the converter to smooth the currents flowing into the grid due to their enhanced attenuation ability and smaller inductance compared to single L filters. However, the inherent resonance of an LCL filter makes the control of such a system challenging, and different passive and active damping strategies have been developed till now. This paper aims to the damping problems of LCL filters and proposes a new approach to realize active damping. Based on traditional virtual resistance damping strategy, the new algorithm employs a lead compensation block in the capacitor current feedback loop so as to alleviate the impact of control delay. It is easy to be transformed from conventional virtual resistance damping method since just an additional digital filter is needed. Theoretical analyses for the essence equivalent relationship between passive damping and virtual resistance damping, as well as the impact investigation of control delay are made in details. The results show that the traditional virtual resistance active damping method is equivalent to passive damping of connecting damping resistance in parallel with the capacitor in the control block diagram, while the proposed virtual resistance active damping method is equivalent to passive damping of connecting damping resistance in series with the capacitor in the control block diagram. Both simulation and experimental results have verified the feasibility.

关键词： absorption of shock BLOCK DIAGRAM Capacitors Filters Virtual Equivalent damping force control block

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Application and Practice of Digital Twin Technology in Monitoring Status of power Equipment in Converter Valve Hall

Application and Practice of Digital Twin Technology in Monit...

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Intelligent Communication and Computer Engineering (ICICCE), International Conference on

作者： He Yongsheng Deng Baojia Lu Zongxiang Zhang Shiling Dai Liangjun State Grid Chongqing Electric Power Company Electric Power Research Institute Deptartment of Electrical Engineering Tsinghua University State Key Lab of Control and Simulation of Power Systems and Generation Equipment

The internal power equipment of ultrahigh voltage converter valve hall is numerous and complex in structure, involving the various information elements such as the temperature and vibration. Moreover, the gas inside ultra-high voltage converter bushing is SF6 gas. Under the current over-load condition of the converter bushing, SF6 gas will decompose. This article focuses on the SF6 gas equipment inside the ultrahigh pressure converter valve hall as the research object, and analyzes specific types and content of SF6 gas decomposition products. In order to effectively detect gas content in the digital twin model of the converter transformer bushing, the new portable SF6 gas chromatograph, laser detection technology and device for HF gas, and partial discharge detection technology research using the acoustic electric coupling method are carried out, providing the effective means for onsite detection of hidden faults in operating equipment. Research has shown the digital twin technology can effectively detect the absorption spectra of gases such as O2, H20, CO, CO2, CF4, SO2, H2S, SOF2, and SO2F2. On the other hand, through digital twin partial discharge detection technology, it is effectively found that the SO2 inside the UHV converter sleeve is 29μL/L, H2S is 4μL/L, CO is 36μL/L, HF=0, detected SO2 and H2S components, determined as the insulation heating defect. The research results of paper provide theoretical and data support for operation status monitoring of SF6 gas insulated power equipment inside the ultra-high voltage converter valve hall.

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Phase-Shift control of Isolated Bidirectional DC-DC Converters for Unidirectional power Flow

Phase-Shift Control of Isolated Bidirectional DC-DC Converte...

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IEEE Energy Conversion Congress and Exposition

作者： Junjie Ge Zhengming Zhao Junchao Ma Fanbo He Liqiang Yuan Ting Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University 100084 Beijing P. R. China

ISBN: (纸本)9781479957774

In the conventional phase-shift control of isolated bidirectional DC-DC converters, the phenomenon of power backflow is quite obvious. General improved phase-shift control methods can reduce the power backflow of the input. However, they do not take the power backflow of the output into consideration. In this paper, a novel phase-shift control of isolated bidirectional DC-DC converters for unidirectional power flow is proposed. It can eliminate the power backflows of both the input and the output at the same time. Furthermore, the converters in the proposed phase-shift control can achieve the zero-current switching in the whole power rang. Experimental results from a prototype verify the feasibility and validity of the proposed control method, and show superior performance.

关键词： DC-DC power converters Voltage control Load flow control systems Educational institutions Prototypes

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Effect of UV Radiation Aging on Creepage Discharge Characteristics of High Temperature Vulcanized Silicon Rubber at High Altitude

Effect of UV Radiation Aging on Creepage Discharge Character...

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中国物理学会第二十二届全国静电学术年会

作者： JIN Fu-bao LIANG Bin ZHOU Yuang-xiang ZHONG Liu ZHANG Ling School Of Water Resources and Electric Power Qinghai University Xining80016China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Ele

Aiming at the special working environment of composite insulators at high altitude area,we investigate the creepage discharge characteristics of aged HTV(High Temperature Vulcanized,HTV)silicone rubber materials by UV(ultraviolet radiation,UV)aging method in this *** results show that the creepage discharge flashover voltage first increased,then decreased as aging time increasing,whereas the creepage discharge initial voltage was not significantly affected by aging *** aging time has little effect on creepage discharge *** aging time contributed to shorter endurance time and higher creepage discharge development *** magnitude of discharges increase rapidly in a short time after *** partial discharge detection system was used to detect the whole creepage discharge development *** to the partial discharge characteristics parameters of creepage discharge,we divided the development process of creepage discharge into initial stage,developmental stage,accelerating stage,and critical breakdown *** with characteristic parameters of unaged HTV silicone rubber,the characteristic parameters for the aged HTV silicone rubber exhibited less fluctuation and clear *** aging not only has an effect on the physicochemical and hydrophobic properties of the materials,but also accelerates the development process of creepage discharge under AC *** should be given enough attention in engineering practice,especially at high altitude area.

关键词： High temperature vulcanized silicone rubber creepage discharge UV aging creepage discharge inception voltage creepage discharge flashover voltage high altitude characteristic parameters

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Effects of Temperature on Creepage Discharge Characteristics in Oil-Impregnated Pressboard Insulation under Combined AC-DC Voltage

Effects of Temperature on Creepage Discharge Characteristics...

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中国物理学会第二十二届全国静电学术年会

The characteristics of oil-impregnated pressboard(OIP)insulation in converter transformer are different with that in traditional AC transformers due to the complication of voltage applied on valve side windings of converter *** is a serious lack of empirical research on effect of temperature on creepage discharge characteristics in OIP under combined AC-DC ***,this study investigates the characteristics spectrum of creepage discharge in OIP under combined AC-DC voltage,and explores the effect of temperature on creepage discharge characteristics under different temperature from 70 to 110℃.The experimental results show that the partial discharge inception voltage and flashover voltage decrease as temperature *** times of low amplitude discharge(LAD)decrease and amplitude of LAD *** temperature had an accelerating effect on the development of creepage discharge in the OIP under combined AC-DC voltage Meanwhile,the times of high amplitude discharge(HAD)gradually increase at each stage of creepage discharge with higher *** analysis indicates that the charge carriers easily accumulate and quickly migrate directional movement along the electric field ahead of *** residual charge carriers are more easily dissipated after ***'hump'region of LAD moves to the direction of higher discharge *** interval time between two consecutive discharges drastically *** HAD intensively appear,result in accelerating the development of creepage discharge in OIP insulation.

关键词： Oil-impregnated pressboard insulation temperature combined AC-DC voltage creepage discharge inception voltage flashover voltage

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Coordinated Wholesale and Retail Market Mechanism for Providing Demand-side Flexibility

Coordinated Wholesale and Retail Market Mechanism for Provid...

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Sustainable power and Energy Conference (iSPEC)

作者： Gang Luo Yujun He Chen Zhao Xuan Zhang Shaohua Lin Yue Zhao Dispatch and Control Center Guangdong Power Grid Co. Ltd Guangzhou China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China

With the trend of electricity market deregulation for recent decades, the consumers at demand-side are progressively encouraged to trade the power in competitive market environment. Conventionally, only large-scale consumers participate directly in the wholesale market that adopts spot energy pricing. Most small-scale consumers are involved in the retail market that offers non-varying tariff predefined by retailers or utility companies. In this work, we investigate a framework of coordinated wholesale and retail market structure that enables consumers in the retail market to reflect the spot price and improve the power system flexibility for the high penetration of renewables. Then, market behaviors of demand-side participants with the proposed market mechanism and some related business models are discussed. The following participation modes for consumers could be opted including: direct trade, trade agented by retailers or organized in virtual power plant (VPP). For a pool-based trade at demand-side, a bi-level market clearing mechanism at transmission and distribution levels is explained. This mechanism seeks to optimize the global demand profile for hosting renewables while solving the operating constraint of loads and local networks. This study can offer constructive advises to promote further development of China's electricity market.

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Losses Modeling Based on Domain Wall Processes and Valida-tion Considering Rotational Excitation of Electrical Steel Sheets.

Losses Modeling Based on Domain Wall Processes and Valida-ti...

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International Conference on Magnetics (INTERMAG)

On the basis of damping principle of vibration, the domain wall processes is investigated and modeled at low-to-medium frequencies in electrical steel sheets. Due to the energy dissipation chiefly descends from a micro-vortex current caused by domain wall motion, the coupled Landau-Lifshitz-Gilbert (LLG) and Maxwell electromagnetic diffusion equations are thus considered to describe the high-frequency characteristics. The overall core losses are eventually deduced in terms of separate contributions by domain wall processes and classical eddy current. Moreover, the calculation model can be extended to rotational excitation pattern. Hence, taking the typical electrical steel sheets as example, the novel core losses calculation model is analysed and compared with the total alternating core losses supplied by electrical steel sheets manufacturers and the 3-D rotating experimental core losses of sheets specimens which are carried out by using a 3-D magnetic properties testing system.

关键词： Magnetics Conferences

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