检索结果-内蒙古大学图书馆

Study on Over-Voltage of 220 kV Transformer＇s Neutrals and Protection Strategy

Journal of Energy and power Engineering 2011年第11期5卷 1102-1108页

作者： H.P. Yu S.M. Chen P.C. Yang H. Yin G.L. Wu State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beoing 100084 China Chongqing Electric Power Research Institute Chongqing 401123 China

In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220 kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Currently the value of over-voltage on transformer neutral point and the corresponding protection strategy is based on theoretical formula. This article uses the PSCAD/EMTDC software to calculate the over-voltage on the neutral point of 4 ungrounded power transformers in Chongqing 220 kV power grid. The result shows that the power frequency transient over-voltage on the neutrals may reach 178 kV. If the single-phase grounding fault occurs in ungrounded power system, the power frequency over-voltage on the neutrals will be more serious and rise to 138.6 kV. Non-full phase operation may cause serious ferro-resonance over-voltage on the neutrals of no-load transformer, which may last for seconds and may rise to 723.7 kV, causing serious threat to the transformer neutrals and line-side equipment. The article also studies the gap parameter which should be taken on the neutrals of 220 kV transformers at the end.

关键词： Neutral point power transformer arrester gap power frequency over-voltage lightning over-voltage.

来源：评论

学校读者我要写书评

暂无评论

Design and implementation of automatic voltage control system applied to a power grid in Northeast US

引用

Dianwang Jishu/power System Technology 2013年第2期37卷 349-355页

作者： Zhang, Mingye Guo, Qinglai Sun, Hongbin Tong, Jianzhong Zhang, Boming Wu, Wenchuan Wang, Bin State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China PJM Interconnection PA 19403 United States

With the raising of requirement of power grid operation to voltage control and reactive power management level, automatic voltage control (AVC) becomes a hot spot in the research. Due to the constraints in the management mode, the applied research of AVC is hitherto a blank in North America power grids. An AVC system, which is suitable to special management modes of a certain interconnected power grid in Northeast U. S. and can meet the demand of on-line operation, is designed and implemented. In the designed system, phase shifter models are added into power flow modules and during the computation of control strategy by optimal power flow (OPF) the static security constraints after the assumed faults are considered. Both the data and assessment results of long-term on-line trail-operation show that the reactive power and voltage level of the interconnected power grid can be improved by applying the designed AVC system, and both security and economy of the interconnected power grid can be enhanced.

关键词： Electric power system control

来源：评论

学校读者我要写书评

暂无评论

Transmission expansion planning modelfacilitating low-carbon power sources' development

引用

Dianwang Jishu/power System Technology 2015年第10期39卷 2725-2730页

作者： Du, Ershun Sun, Yanlong Zhang, Ning Chen, Songsong He, Guixiong Kang, Chongqing State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing100084 China China Electric Power Research Institute Haidian District Beijing100192 China

power planning oriented to low-carbon can relief 'carbon lock' effect and facilitate to achieve low-carbon power system. For tapping low-carbon potential of power grid, this paper comprehensively analyzes corresponding low-carbon elements and proposes a novel transmission planning model for promoting low-carbon power sources' development. These analyses include facilitation of integration and accommodation of renewable power, life cycle carbon emission process and reduction of grid loss. Based on multi-scenario technique, the proposed model minutely simulates system operation process considering both typical and extreme operation constrains. Through inequality separation and piecewise linearization, original model is converted into a large scale mixed integer linear programming (MILP) model. Case study of Jiangsu provincial grid verifies validity of the proposed model. ©, 2015, power System Technology Press. All right reserved.

关键词： Life cycle

来源：评论

学校读者我要写书评

暂无评论

First stirling-type cryocooler reaching lambda point of ~4He(2.17K) and its prospect in Chinese HUBS satellite project

引用

Science Bulletin 2019年第4期64卷 219-221页

作者： Jue Wang Changzhao Pan Tong Zhang Kaiqi Luo Xiaotong Xi Xianlin Wu Jianpeng Zheng Liubiao Chen Junjie Wang Yuan Zhou Hai Jin Wei Cui University of Chinese Academy of Sciences CAS Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences Laboratoire National de Métrologie Et d'essais-Conservatoire National des Arts et Métiers (LNE-Cnam) State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Department of Physics and Center for Astrophysics Tsinghua University

The issue of "missing baryons” is always an unsolved mystery in galaxy cosmology, and an important reason for the great uncertainty of the galaxies' formation and evolution. To find the "missing" baryons, extra high-resolution spectral observation and imaging of the soft X-ray band (<1 kev) is required. However, the existing observation methods cannot meet this requirement. Therefore, Tsinghua University leads and proposes the Chinese "Hot Universe Baryon Surveyor (HUBS)" satellite program.

关键词： missing baryons HUBS missing

来源：评论

学校读者我要写书评

暂无评论

Creating multivariable response surfaces by the two-stage adaptive sampling techniques and its application in the optimization of grounding grids

Creating multivariable response surfaces by the two-stage ad...

引用

作者： Zou, J. Guo, J. Zhang, B. He, J.L. Lee, J. Chang, S. State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Electrical Environment and Transmission Group Korea Electrotechnology Research Institute Changwon 641600 Korea Republic of

A fast and efficient adaptive sampling algorithm to obtain the response surface of multivariable objective function is presented. The algorithm is divided into two stages. First, starting with a low-rank interpolation model, the technique systematically increases the rank by optimally choosing new support points in the areas of the highest error until the required accuracy is achieved. Second, the verification between the fitted result and the exact one is carried out. The optimization of grounding grids is performed to show the effectiveness of the proposed algorithm. © 2006 IEEE.

关键词： Algorithms

来源：评论

学校读者我要写书评

暂无评论

Design and engineering application of automatic discovery system for critical flowgates and security operation rules in power grids

引用

Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第1期39卷 117-123页

作者： Zhao, Feng Sun, Hongbin Huang, Tianen Guo, Qinglai Wu, Wenchuan Wen, Bojian 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 Guangdong Power Grid Power Dispatching Control Center Guangzhou510600 China

The framework of an automatic discovery system for critical flowgates and security operation rules in the power grid is designed. Based on the real-time operation data of the power grid, the system is able to automatically find the critical flowgates adapted to the online operation state of the grid. By using the automatic learning method, the system can find the fine rules of critical flowgates as the security operation knowledge of the grid. The functions of the core modules of the system are described, including online automatic discovery of critical flowgates, online calculation of limit transmission capacity of critical flowgates, online generation of mass simulation samples, feature selection, automatic discovery of security operation rules of the power grid. The online application of the system has been realized in Guangdong power grid. The application effect shows that the system is able to generate the security operation knowledge fast enough and refresh it every 15 minutes for online application as required. Meanwhile, the knowledge is capable of not only covering the existing security operation knowledge formulated by experts offline, but also finding new knowledge adapted to the online power grid operation mode, while improving the power grid security and economy.

关键词： Electric power transmission networks

来源：评论

学校读者我要写书评

暂无评论

A phase-disposition PWM method for DC voltage balance in cascaded h-bridge rectifier

A phase-disposition PWM method for DC voltage balance in cas...

引用

2010 International Conference on Electrical Machines and systems, ICEMS2010

作者： Tao, Xinghua Li, Yongdong Sun, Min State Key Lab of Control and Simulation of Power System and Generation Equipments Dept. of Electrical Engineering Tsinghua University China Dept. of Electrical Engineering Naval Engineering University China

In this paper, a novel control scheme for cascaded H-Bridge rectifier (CHBR), which can be used as the primary end of high voltage high power multilevel converters, is presented. The controller is similar with the one for single phase rectifier. To improve the performance of the controller, notch filter and proportion resonance (PR) controller are employed and the discrete methods for them are discussed in detail. The different function of CHBR controller from the single rectifier is for voltage balancing. Therefore, the phase-disposition technology, which is used in the multilevel converter, is introduced to eliminate the voltage error from the expected value. With this approach, the states of the switches of the CHBR are decided correctly by the practical condition and then the DC-link capacitors of the cells are controlled to charge or discharge in the way which results to voltage balancing. The effectiveness of the proposed approach is verified by experimental results.

关键词： Cascaded H-bridge rectifier Phase-disposition PWM PR controller Voltage balance

来源：评论

学校读者我要写书评

暂无评论

Medium and long-term wind energy forecasting method considering multi-scale periodic pattern 10

Medium and long-term wind energy forecasting method consider...

引用

2020 10th International Conference on power, Energy and Electrical Engineering, CPEEE 2020

作者： Lin, Yisha Lu, Zongxiang Qiao, Ying Li, Mingjie Liang, Zhifeng State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China State Grid Corporation of China Haidian District Beijing100031 China

Medium and long-term weather sequence forecast becomes unreliable beyond two weeks since the weather is a chaotic system. Using values of same months for electricity prediction of wind power is the usual method. This approach defaults wind power output with annual cycle law. However, the periodic pattern can be very complicated in fact with multiple time scales. This paper proposes an approach with multi-scale periodic pattern considered. The application of parametric estimation on cumulative distribution function avoids the difficulty of predicting the power curve. Meteorological condition is considered to some extent via multi-scale periodic pattern explored basing on historical energy data. This work is an exploration for medium and long-term wind power forecasting that can well adapt to existing conditions. It has better prediction accuracy than the method without multi-scale periodicity considered. © 2020 The Authors, published by EDP Sciences.

关键词： Wind power

来源：评论

学校读者我要写书评

暂无评论

A neutral-point potential balancing algorithm for five-level ANPC converters

A neutral-point potential balancing algorithm for five-level...

引用

International Conference on Electrical Machines and systems (ICEMS)

作者： Kui Wang Yongdong Li Zedong Zheng State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

Five-level active neutral-point-clamped (ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional neutral-point clamped (NPC) converters and flying-capacitor (FC) converters. Its dc-link is subdivided into two equal parts and the main problem is the neutral-point (NP) potential balancing. In this paper, a NP potential balancing algorithm based on zero-sequence voltage injection is presented. By calculating the NP currents of all key zero-sequence voltages, the most appropriate zero-sequence voltage is selected to generate the demanded NP current. Moreover, by further limiting the span of injected zero-sequence voltages, the NP balancing algorithm can make the two IGBTs connected in series operate at fundamental frequency. A three-phase five-level ANPC inverter prototype was built up and experimental results are presented to verify the validity of this algorithm.

关键词： Capacitors Electric potential Switches Voltage control Inverters Insulated gate bipolar transistors Heuristic algorithms

来源：评论

学校读者我要写书评

暂无评论

Evaluation of cascading failure in power system based on the operational reliability theory

Evaluation of cascading failure in power system based on the...

引用

International Conference on Probabilistic Methods Applied to power systems (PMAPS)

作者： Xin Zou Lin Cheng Yuanzhang Sun State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781424457205;9781424457212

According to the characteristics of the cascading failures in power grid, a lot of assessment methods based on the probability theory have been proposed in recent years. However, most of them ignore the influence of the changing operating conditions on the power system planning and operation. This paper assesses the risk of the cascading failure in the power system based on the operational reliability theory which considering the variation of operating states and environment of the power system. The operational reliability of the power system is calculated based on Markov Process which describes the transient probability of states. The key conception of this theory is that the failure rate and the probability of components are changing along with the life of the equipment, the operating states and the environment conditions. A new evaluation procedure is brought up to calculate the operational reliability indices which can provide the specific information of the cascading failure. The evaluating results of the test system confirm that this approach is applicable to analyze the cascading failures in real power system.

关键词： power system faults power system protection power system reliability Reliability theory power system planning power system transients power grids Markov processes Probability System testing

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：