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Habitat suitability model of the four major Chinese carps

Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and Engineering 2011年第SUPPL. 1期19卷 123-129页

作者： Yi, Yujun Zhang, Shanghong Ministry of Education Key Laboratory for Water and Sediment Sciences Beijing Normal University Beijing 100875 China State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Beijing Normal University Beijing 100875 China Renewable Energy School North China Electric Power University Beijing 102206 China

Coupling habitat suitability function of carps spawning sites with one-dimensional mathematical model, a Habitat Suitability Index (HSI) model to calculate the habitat suitability indices for the four major Chinese carp species was developed. The model was validated by measured data. Using the Habitat Suitability Index model of the four major Chinese carps, the stream habitat for the carp species under different hydraulic condition were assessed. Minimum instream flow and suitable daily discharge increase during the reproduction season for the carp species were suggested. The minimum discharge needed for the four major Chinese carp species in the middle reach of the Yangtze River is 3000 m3/s. Different daily discharge increases are required for different initial discharges. When the initial discharge is 4000 m3/s, the optimal daily discharge increase is approximately 500 m3/(s. d);and when the initial discharge is 9000 m3/s, the optimal daily discharge increase is approximately 800 m3/ (s. d);when initial discharge is 15000 m3/s, the optimal daily discharge increase is approximately 1000 m3/(s. d). Too small or too large of a daily discharge increase is not good for carps spawning.

关键词： Functions

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CAI combustion comparison between NVO strategy and EGRB strategy

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Jilin Daxue Xuebao (Gongxueban)/Journal of Jilin University (Engineering and Technology Edition) 2011年第SUPPL. 1期41卷 47-52页

作者： Li, Hua Cheng, Peng Tan, Man-Zhi Gu, Yan-Hua Wang, Hui Peng, Ya-Ping Guo, Ying-Nan State Key Laboratory of Automotive Simulation and Control Jilin University Changchun 130022 China Beijing Polytechnic College Beijing 100042 China System and Function Development Technical Center United Automotive Electronic Systems Co. Ltd. Shanghai 201206 China

On the basis of self-developed electro-hydraulic variable valve train, controlled auto-ignition (CAI) was achieved under two different EGR strategies on a modified single cylinder engine. Stable CAI operating ranges of these two valve timing scenarios were obtained by plotting tested operating points. Within the operating range, engine performances and combustion features were analyzed. The experimental results indicate that operating range of NVO strategy, allowing more substantial adjustment of valve phase, is wider than that of EGRB strategy at fixed engine speed of 1000 r/min. The maximum BMEP of EGRB strategy slightly exceeds the NVO strategy. Moreover, brake thermal efficiency exceeds 30% in most of these two operating range, higher than conventional engine, with an extremely low NOx emission at the same time. Besides, start of combustion of CAI under NVO strategy is a little advanced and combustion duration is a little shorter compare with that of EGRB strategy.

关键词： Ignition

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A method of collaborative multi-path load forecasting based on maximum entropy principle

A method of collaborative multi-path load forecasting based ...

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作者： Xiao, Jun Zhang, Xuan He, Lin Lin, Li-Peng Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China Tianjin Electric Power Company Tianjin 300010 China

ISBN: (纸本)9781457700668

This paper introduces synergetic theory and proposes multi-path load forecasting automatically coordinated approach based on the maximum entropy principle. Taking the expectation and second order central moment of forecasted results into account and using the maximum entropy principle,this synergetic load forecasting method receives the probability distribution function of the forecasted values and obtains the final high, middle and low forecasting scheme based on the probability theory. Case study has shown the model and method mentioned above can take the affection of the conflicts among different forecasting path into account in forecasting, resulting in higher precision of load forecasting © 2010 Chinese Soc for Elec Eng.

关键词： Forecasting

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Application of automatic differentiation technique to the transient simulation of distributed generation system

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Dianli Xitong Zidonghua/Automation of Electric power systems 2010年第23期34卷 71-75+101页

作者： Wang, Chengshan Huang, Bibin Li, Peng Gao, Fei Ding, Fei Ding, Chengdi Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China

In view of the diversity of the distributed generation control system and the influence on the simulation efficiency due to adoption of the user-defined model based on the basic elements of control systems, a control system compositional modeling method is proposed that consists in combining the basic elements into a number of functions. The corresponding compositional function values and derivatives can be accurately and highly efficiently found using the automatic differentiation technique, effectively increasing the computational efficiency of the simulation program while maintaining the code maintainability and scalability. This method is validated with an example. © state Grid Electric power Research Institute Press.

关键词： Distributed power generation

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Study on transferred lightning overvoltage in microgrid

Study on transferred lightning overvoltage in microgrid

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Asia-Pacific International Symposium on Electromagnetic Compatibility

作者： Hongqiao Yu Shuiming Chen Pengcheng Yang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University

ISBN: (纸本)9781424456215

If the microgrid is stroke by lightning, the lightning overvoltage which transferred though distribution transformer has great influence on the safety of the microgrid. The models of microgrid and high-frequency transformers are established based on the electromagnetic transient calculation program PSCAD/EMTDC. The transferred overvoltage with different lightning strike position in microgrid is researched in this paper. The effect of surge arresters on restricting overvoltage is also analyzed. The simulation results show that surge arresters must be installed at both sides of transformer due to the high overvoltage when the transformer has no load. If the transformer is connected with cables, the overvoltage will be reduced. The longer the cable is, the lower the overvoltage is. The types of loads have a little influence on the overvoltage.

关键词： Lightning Voltage control power transformer insulation Frequency Capacitance Laboratories power system simulation power system modeling power generation Electromagnetic modeling

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Study on lightning protection of cables and transformer in Microgrid

Study on lightning protection of cables and transformer in M...

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China International Conference on Electricity Distribution, CICED

作者： Hong-qiao Yu Shui-ming Chen Yang Peng-cheng State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457700668

The cable and transformer are important distribution equipment in Microgrid. Due to the low insulation level, the insulation of them is easily damaged by lightning. The models of high-frequency transformer and the calculation model of induced lightning with transmission line based on electromagnetic transient calculation software PSCAD / EMTDC are designed in this paper. The lightning protection of cables and transformer in Microgrid, the transferred overvoltage of transformer and the effect of the length of cables and the load types to overvoltage level are researched. The conclusion shows that the induced overvoltage and transferred overvoltage could be reduced efficiently after installing surge arrester at the cables and transformer, but the direct lightning overvoltage is not reduced in the safety range; The longer the cables, the lower the overvoltage is; The inductively load can reduce the overvoltage level slightly while the capacitive and resistance loads has no influence.

关键词： power cables Load modeling Arresters Cable insulation EMTDC Lead PSCAD

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Cascaded battery energy storage system based on dual active bridges and a common DC bus

Cascaded battery energy storage system based on dual active ...

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International power Engineering Conference (IPEC)

作者： Yiding Jin Qiang Song Wenhua Liu Weixin Sun State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

Along with the increasing system capacity, large-scaled energy storage systems are supposed to be connected into 10kV or higher networks. Urban network has strict criterions on power quality of the power electronic devices connected. Moreover, the occupancy and noise of industrial frequency transformers also become restraints to the promotion of urban network energy storage. For that reason, this paper proposes a battery energy storage system based on cascaded dc-ac converter, dual active bridges, and a common dc bus. High frequency transformers are used to replace the industrial frequency transformer for insulation, and battery groups are connected to the common dc bus with respective dc-dc interfaces. This multilevel converter system is easy to modularize, easy to extend, and allows different kinds of batteries to work together. The main circuit and proper control system are designed, with the soft-switching condition and current control issues of the dual active bridge analyzed in detail. The simulation results from EMTDC model verify the operation principles and corresponding control strategies.

关键词： Batteries Voltage control Converters Switches Bridge circuits

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Basic principles of hybrid excitation PM synchronous generator utilizing harmonic for excitation

Basic principles of hybrid excitation PM synchronous generat...

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作者： Xia, Yonghong Wang, Shanming Ma, Mingyuan Hao, Liangliang Qiu, Arui Huang, Shaogang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Department of Electrical and Automatic Engineering Nanchang University Nanchang Jiangxi 330031 China

ISBN: (纸本)9788986510119

A novel method, which utilizes harmonic for excitation, is presented to adjust the air-gap magnetic field for permanent magnet synchronous machine. The structure and basic principles of the hybrid excitation PM synchronous generator(HEPMSG) are introduced. The no-load and on-load electromagnetic field are calculated based on finite element method, and the waveform and effective value of the winding voltage and characteristics of the machine are gained for different loads. Calculation results demonstrate the new hybrid excitation scheme is feasible. This new method combines the advantages of PM machines and electrical excitation machines. The machine removes the brushes and slip rings, which makes permanent magnet machine keep simple and highly reliable.

关键词： Synchronous generators

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Notice of Retraction: The Optimal Bidding Based On The Prospect Theory

Notice of Retraction: The Optimal Bidding Based On The Prosp...

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IEEE PES Asia-Pacific power and Energy Engineering Conference (APPEEC)

作者： Ji-keng Lin Xudong Wang Key laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin China

This article has been retracted by the publisher.

关键词：

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A study on steady characters of inverter interfaced distributed generation in three phase symmetrical system

A study on steady characters of inverter interfaced distribu...

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International Conference on power system Technology (powerCON)

作者： Qiang Jin Yong-Li Li Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin China

Recently inverters are all-pervading used as the connective instrument of distributed generations and distributed power system. When inverter interfaced distributed generations are connected to the distribution system, it may bring some new problems on load flow and fault characteristic and protection. The analysis on steady characters of PQ control mode and VF control mode inverter interfaced distributed generation is done when the system is three phase symmetrical. Generally speaking there are limits on power and current in control system for the security of distributed generations and power electronic devices in inverter, so the analysis is more complex. The mathematical analysis on three phase symmetrical system is done and restriction equations are described whether three phase symmetrical fault occurs or not. For the solution of the equation groups expresses the steady state of the system, so the solution of the equation groups is one and only. Then the restriction equation groups are solved. The solution in different areas shows the reason of steady non-linear character of inverter interfaced distributed generations and the simulation shows the conclusion correct. The steady characteristic curves of PQ control mode and VF control mode inverter interfaced distributed generation about voltage and current and power are got from the function of voltage and current and power at the same time. PQ control mode and VF control mode inverter interfaced distributed generation behave similarly but not identically when three phase symmetrical fault occurs in three phase symmetrical system. The disadvantageous influence on protection is analysed by the way.

关键词： Equations Mathematical model

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