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Method of coordination among strongly coupled power plants for automatic voltage control

Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第12期39卷 165-171页

作者： Wang, Bin Guo, Qinglai Sun, Hongbin Tang, Lei Zhang, Boming Tian, Junjie Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China Dispatching and Communication Center of State Grid Shanxi Electric Power Corporation Taiyuan030001 China

To solve the problem of reactive power non-coordination among strongly coupled plants, a coordinating method for strongly coupled plants for automatic voltage control (AVC) is proposed. The coupling coefficient among plants is introduced, and the plant coordinating group is generated as the coordinating unit. The reactive power unbalanced index among strongly coupled plants is defined. And the current operation state of power grid is determined. In the event the pilot bus voltage is not controlled in place, the control strategy of voltage regulation and reactive power tracking control is adopted so that the pilot bus voltage will be enabled to guarantee that the reactive power unbalanced index between strongly coupled plants will meet the control requirement while tracking optimal settings. If the pilot bus voltage is already in place, reactive correction control based on the objective of plant-to-plant coordination will be carried out to reduce the deviation in reactive load while ensuring that the pilot bus voltage is maintained within the range of control dead zone. Reactive regulating commands will be added to the traditional voltage regulating commands to suppress possible irrational reactive power distribution or reactive fluctuation between strongly coupled plants. Application of the proposed method in a number of regional and provincial grids in China shows that the proposed method is able to reduce irrational reactive power distribution between strongly coupled plants. © 2015 state Grid Electric power Research Institute Press.

关键词： Reactive power

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Smart substation advanced application software adapted for two-level distributed smart dispatch and control

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Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第1期39卷 233-240页

作者： Sun, Hongbin Mu, Jianan Sheng, Tongtian Li, Qingxin Wang, Jing Wang, Bin Wang, Xuran Ji, Guoqiang Wu, Wenchuan Guo, Qinglai Li, Yalou Wang, Dexing Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China China Electric Power Research Institute Beijing100192 China East China Electric Power Dispatching and Control Sub-Center of State Grid Shanghai200120 China

The development of smart grid has posed a challenge to the traditional centralized dispatch mode. The basic contradiction between distributed autonomy and centralized coordination is reexamined, and an architecture of smart substation advanced application software system is proposed, including such advanced applications as modeling, state estimation, intelligent alarming, voltage stability assessment and control, automatic voltage control, risk assessment modeling, etc. This facilitates a change from centralized dispatch and control mode to a more reliable, agile substation-control center two-level distributed smart dispatch and control mode. The features, functions and realization of the proposed advanced application software are described, some field engineering application cases demonstrated, and certain practical aspects of implementation discussed. Finally, the prospect for future development of the smart substation advanced application software is displayed.

关键词： state estimation

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Day-ahead market mode with power consumers participation in wind power accommodation

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Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第17期39卷 120-126页

作者： Xia, Ye Kang, Chongqing Chen, Tianen Li, Yan Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China Northwest Branch of State Grid Corporation of China Xi'an710048 China

Facing the wind power accommodation difficulties revealed in 'Northwest, North and Northeast China' region during heating season overlapping wind resource surplus season, a novel day-ahead market mode is proposed to encourage power consumers to participate in wind power accommodation based on the market reform plan of direct electricity purchase by major power consumers. Based on power consumer and generation company direct transactions in the spot market environment, the day-ahead market mode with power consumers participating in wind power accommodation is designed including transaction application, transaction clearing, transaction settlement and market organization. A day-ahead market model is developed with power consumers participation in the wind power accommodation mode taken into account alongside individual demands of each power consumer's power consumption profile and bidding price limits on power consumers. The rationality and effectiveness of the proposed market mode and model is validated by numerical results. ©2015 Automation of Electric power systems Press

关键词： Wind power

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Real-time economic dispatch model with prohibited zones considering maximum wind power injection

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2015年第4期35卷 759-765页

作者： Ding, Tao Sun, Hongbin Bo, Rui Yao, Zhengyi State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China Midwest ISO Street Paul MN55108 United States Baoji Power Supply Bureau BaojiShaanxi Province721004 China

Due to the physical limitations of the generator, the vibrations in a shaft bearing may be amplified at a certain operation regimes, the prohibited zones are needed which leads to a disjoint power generation instead of continuous output. Besides, the reservation for each generator should also be considered to face with the stochastic integrated generation of large-scale wind power into power grid, which actually reduces the total reservation of the grid. Therefore, the economic dispatch with the multiple objective of minimized cost and maximized wind power integration, as well as the prohibited zones, was set up, and a standard mixed integer quadratic programming was formulated. Furthermore, the test system with six, fifteen and multiple generators were simulated respectively. The results show that the proposed method can be applied to the real-time system. ©2015 Chin. Soc. for Elec. Eng.

关键词： Real time systems

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Reducing the impact of source internal resistance by source coil in resonant wireless power transfer

Reducing the impact of source internal resistance by source ...

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作者： Zhang, Yiming Lu, Ting Zhao, Zhengming State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781479956982

Wireless power transfer (WPT) is the state-of-the-art research interest. In the WPT system efficiency is an important figure of merit. In order to reduce the impact of the source internal resistance and improve the system efficiency of the conventional two-coil structure, a source coil is added to the two-coil structure, forming a three-coil structure. Both the two-coil structure and the three-coil structure are modeled and analyzed with the circuit theory. The system efficiencies of both structures with optimal loads and a fixed load are deduced. The system efficiency of the three-coil structure is proved to be higher than that of the two-coil structure. An experimental apparatus is implemented and the experimental results match well with the theoretical calculations. The larger the source internal resistance, the more significantly the addition of the source coil improves the system efficiency. © 2014 IEEE.

关键词： Energy transfer

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Photovoltaic plant operating statuses identification model based on support vector machine using loss quantity of electricity feature parameters

Photovoltaic plant operating statuses identification model b...

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International Conference on Renewable power generation (RPG 2015)

作者： Kangping Li Fei Wang Zhao Zhen Yujing Sun Zengqiang Mi Hongbin Sun Chun Liu Bo Wang Jing Lu State Key Laboratory of Alternate Electrical Power System With Renewable Energy Sources (North China Electric Power University) Baoding 071003 Hebei Province China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment (Department of Electrical Engineering Tsinghua University) Haidian District Beijing 100084 China China Electric Power Research Institute Haidian District Beijing 100192 China)

ISBN: (纸本)9781510821415

Operating Statuses Identification (OSI) can help operators to find fault timely and minimize the loss. So it is of great significance for optimal operation of photovoltaic (PV) plants. The loss quantity of electricity (LQOE) is defined as that should have been generated but actually not, which is caused by inverter fault, PV modules fault, dust stratification or combinations of them. Firstly, mathematical models of PV cells are proposed to figure out the LQOE of each PV module. Secondly, after analysing the relation between LQOE and operating statuses, an index set of LQOE describing the distinction of different operating statuses are defined including four statistical feature parameters and a user-defined index. Thirdly, Support Vector Classification models for OSI (OSI-SVC) are built with input features extracted from the index set. Lastly, simulations are carried out to verify the effectiveness and evaluate the performance of the OSI-SVC models. The results indicated that the operating statuses can be effectively recognized by the proposed model.

关键词： Feature Extraction Loss quantity of electricity Operating Statuses Identification Support Vector Machine

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Cloud identification model for sky images based on Otsu

Cloud identification model for sky images based on Otsu

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International Conference on Renewable power generation (RPG 2015)

作者： Hongping Li Fei Wang Hui Ren Hongbin Sun Chun Liu Bo Wang Jing Lu Zhao Zhen Xiaoli Liu State Key Laboratory of Alternate Electrical Power System With Renewable Energy Sources (North China Electric Power University) Baoding 071003 Hebei Province China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment (Department of Electrical Engineering Tsinghua University) Haidian District Beijing 100084 China China ElectricPowerResearch Institute HaidianDistrict Beijing 100192 China

Irradiance changes caused by clouds movement are the main factors, which lead to mutation of photovoltaic power. In order to increase the accuracy of the ultra-short-term photovoltaic power prediction, based on of clouds images, the cloud identification for sky images is one of the primary aspects for improving photovoltaic power accuracy. A cloud identification model for sky images is established based on Otsu. Firstly, a series of sky images are collected by Total Sky Imager (TSI) with the regions of clouds and sky are distinguished. Secondly, the color features (based on RGB values) of pixels in sample images and the spectral and texture features of the whole image are extracted; Finally, we established a cloud identification model for sky images based on Otsu according to the clouds' and sky areas' division and the general characteristics featured by pixels and images. The simulated results show that the model in this paper can identify the clouds in a sky images effectively.

关键词： Otsu cloud identification texture threshold Clouds sky images texture textures pixel

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Electrical properties of oil-paper insulation affected by water conductivity during paper-making process

Electrical properties of oil-paper insulation affected by wa...

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32nd Electrical Insulation Conference, EIC 2014

作者： Huang, Jianwen Zhou, Yuanxiang Jin, Fubao Sha, Yanchao Zhang, Ling Le, Trung Hieu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781479927876

Developments of ultra-high voltage grid in China require better insulation materials, and that forces the transformer presspaper and pressboard manufactures to pay more attention to the papermaking process to enhance their product qualities. In this study, pure water and three kinds of sodium chloride solutions with conductivities of 100 μS/cm, 500 μS/cm and 1000 μS/cm were respectively used to prepare presspaper samples. By vacuum impregnation, four kinds of oil-paper samples were acquired. Test results showed that relative permittivity and tand of oil-paper specimens first varied little then increased a lot with the increasing of water conductivity;DC breakdown field decreased while AC breakdown field changed little. To confirm the differences were due to water conductivity, ion chromatography was used to determine the sodium and chloride ion contents of the presspaper samples, we found that the ion contents increased with electrical conductivity. This indicates that water conductivity does have effects on most electrical properties of oil-paper insulation and lower conductivity can bring better insulation performances. © 2014 IEEE.

关键词： Ion chromatography

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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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作者： Ge, Junjie Zhao, Zhengming Ma, Junchao He, Fanbo Yuan, Liqiang Lu, Ting State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9781479956982

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. © 2014 IEEE.

关键词： Zero current switching

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Series-connected HV-IGBTs using active voltage control with status feedback circuit

Series-connected HV-IGBTs using active voltage control with ...

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作者： Ji, Shiqi Lu, Ting Zhao, Zhengming Yu, Hualong Yuan, Liqiang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9781479956982

The transient voltage unbalance is the major problem that limits the application of series-connected IGBTs in high voltage and high power converters. The asynchronous gate delay which causes that series-connected IGBTs do not turn-on and turn-off at the same time results in the most serious unbalanced voltage sharing. The active voltage control technique is proposed in this paper to solve the asynchronous gate delay problem. By sampling the feedback signal caused by unbalanced voltage, the microcontroller generates a time delay for gate driver to compensate the asynchronous gate delay. The most vital part of active voltage control is the status feedback circuit which is also given in detail in this paper. The function of the status feedback circuit and the effect of active voltage control are verified in a two series-connected HV-IGBTs platform in rated operation (5kV bus voltage and 600A load current). © 2014 IEEE.

关键词： Insulated gate bipolar transistors (IGBT)

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