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International Conference on power Electronics and Motion control (IPEMC)

作者： Huan Chen Hongsheng Chong Kai Sun You Zhou Hang Zhou John Fletcher State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China Nation Institute of Clean and Low Carbon Energy Beijing China School of Electrical Engineering and Telecommunications University of New South Wales Sydney Australia

ISBN: (数字)9781728153018

ISBN: (纸本)9781728153025

The CLLC converter is widely used in bidirectional power conversion systems. The conventional control method for CLLC converter is pulse frequency modulation (PFM) method. However, PFM method can not realize smooth bidirectional power switching, because the driver signals for the primary and the secondary side switches are asymmetric. This paper proposed a voltage-fed control method for CLLC and Synchronous Rectified (SR) Buck two stage converters, which can realize the automatic and smooth bidirectional power switching for CLLC stage. In the proposed control method, the PWM signals for both the primary and the secondary switches are the same. The effectiveness of the proposed voltage-fed control method is verified by experiments.

关键词： Prototypes Switches Pulse width modulation control systems Automatic voltage control power electronics Transient analysis

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Analysis and suppression of subsynchronous oscillation of Rudong wind power through MMC-HVDC system

Analysis and suppression of subsynchronous oscillation of Ru...

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2021 Annual Meeting of CSEE Study Committee of HVDC and power Electronics (HVDC 2021)

作者： J. Li X. Xie J. Yang H. Li Z. Shi K. Wang C. Fu W. Yang Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province Huadong Engineering Corporation Limited Power China Hangzhou Zhejiang Province 310014 China State Key lab of Control and Simulation of Power Systems and Generation Equipment (Dept. of Electrical Engineering Tsinghua University) Haidian District Beijing 100084 China

There may be complex interaction between the converter control systems of wind power and MMC-HVDC, which will lead to sub-/super-synchronous oscillation and threaten the safe and stable operation of the system. The relevant events have been reported in Guangdong Nan'ao, Shanghai Nanhui and Zhangbei projects. Rudong offshore wind power project is the first offshore wind power transmission system in China, and it is still under construction. Therefore, it is of great significance to carry out the research on the risk analysis and suppression measures of sub-synchronous oscillation in Rudong wind power MMC-HVDC system. First, the time-domain simulation model of Rudong wind power MMC-HVDC system is built in the PSCAD/EMTDC simulation model. Then, the effects of the number of wind turbine generators, wind power output and the parameters of MMC-HVDC controller on the sub-/super-synchronous oscillation characteristics of the system are further analyzed. Finally, the suppression measures based on supplementary frequency dependent gain control are proposed, the application position of the controller is discussed, and the parameter optimization method of the controller is given. The research content provides a certain guiding significance for the operation and control of Rudong wind power MMC-HVDC.

关键词： turbogenerators HVDC power transmission wind turbines power transmission control risk analysis time-domain analysis offshore installations HVDC power convertors wind power plants wind power

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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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Two-stage EEG source reconstruction by using the layered recursive algorithm and source contracting method

Two-stage EEG source reconstruction by using the layered rec...

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作者： Zou, J. Xie, Y.Q. Dong, G.Y. State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China School of Physics Peking University Beijing China Prov.-Min. Joint Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability Department of Electrical Engineering Hebei University of Technology Tianjin 300130 China

A two-stage electroencephalogram (EEG) source tomography method is proposed. First, the layer recursive algorithm (LRA) is developed to calculate the cortical potentials from the scalp potentials by using the finite volume method, which can improve spatial resolution of EEG data and be called high-resolution EEG (HIEEG). As a result, the spatial resolution is improved over that obtained with the conventional EEG. Second, the source contracting method is used to localize the equivalent electrical sources inside the brain based on HIEEG data. The applications demonstrate the effectiveness of the method proposed. The LRA provides an alternative implementation to HIEEG. © 2006 IEEE.

关键词： Electroencephalography

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The parameter design method of smoothing inductance based on MMC-MTDC with R-type superconducting fault current limiter

The parameter design method of smoothing inductance based on...

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The 16th IET International Conference on AC and DC power Transmission (ACDC 2020)

作者： P. Guo Z. Yuan G. Liu Y. Zhao Z. Shi Tsinghua University State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Beijing China Shenzhen Power Supply Corporation Shenzhen China Sichuan Energy Internet Research Institute Tsinghua University Chengdu China

The rapid increase of voltage sourced converter brings the great development of the multi-terminal DC technology, both in the DC transmission and DC distribution fields. However, because of the weak impedance characteristic of the VSC-HVDC system, how to suppress and clear DC fault currents becomes a challenge. Considering the stability, the response speed and the system structure, it is not possible to apply excessive inductance at the DC side, hence, the current limiting effectiveness is relatively restricted. On the one hand, with the effective properties, Resistive type Superconducting Fault Current Limiter (R-SFCL) becomes an effective device to solve the problem of VSC-HVDC system under DC faults. On the other hand, because of dynamic energy-impedance characteristics of R-SFCL, the fixed impedance selection method at a certain time to carry out dynamic current limiting analysis is no longer applicable. Therefore, the DC fault current research and R-SFCL characteristic are comprehensively analyzed firstly in this paper. Based on that, a smoothing inductance determination method is proposed to cut off the DC fault current by DC breaker and ensure the continuous operation of remaining parts. Finally, based on a multi-terminal DC system simulation, the improvement and effectiveness of the proposed method are validated.

关键词： power transmission faults HVDC power transmission superconducting fault current limiters HVDC power convertors voltage-source convertors

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Experimental analysis of DC pre-excitation for 3-level inverter-motor system

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第3期26卷 159-163页

作者： Bai, Hua Zhao, Zheng-Ming Hu, Xian Chen, Xin State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing 100084 China South Automation Company Nanjing 210003 China

In the AC adjusting speed system, the significant current impulse frequently occurs in the starting process while the output torque is sufficient. This would damage the power electronics device, cause the unbalance of neutral point in three-level NPC topology, and deteriorate the starting performance. In this paper, a DC pre-excitation strategy, which limits the starting current and enhances the electromagnetic torque via establishing the flux linkage before starting process, is proposed to the three-level inverter under analysis on the mechanism of the above large current. The relevant experiments present its eminent effect on the 380 V/160 kW inverter-motor system. Also this paper discuss the feasibility of its application in high voltage high power inverter.

关键词： Induction motors

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Lightning protection study of transmission line, Part I: Lightning parameters

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Gaodianya Jishu/High Voltage Engineering 2009年第12期35卷 2903-2909页

作者： Chen, Shui-Ming He, Jin-Liang Zeng, Rong State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

Obtaining actual lightning parameters is the fundament of lightning protection of transmission lines. Based on the comprehensive analysis on the methods to acquire lightning parameters, we analyzed the current research states and existed problems of lightning parameters, including annual lightning day, ground flash density, magnitude and waveform of lightning current. The lightning activities have obvious topographical feature, presently the lightning location system (LLS) should be fully applied to acquire the annual lightning day, ground flash density, magnitude of lightning current in different areas. Moreover, the monitoring devices of lightning current should be installed on typical transmission towers with different voltage grades in different areas to obtain the characteristics of real lightning current waveforms and magnitudes, and calibrate and check the lightning current magnitudes obtained from LLS. All these would make the lightning protection of power system focusing on the actual targets. Four sets of the developed monitoring devices of lightning current were installed, and the first lightning current waveform in China, which was similar to the standard waveform recommended by CIGRE, was recorded.

关键词： Electric lines

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Lightning protection study of transmission line, Part III: Protection measures

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Gaodianya Jishu/High Voltage Engineering 2009年第12期35卷 2917-2923页

作者： He, Jin-Liang Zeng, Rong Chen, Shui-Ming State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

The lightning accidents threaten the safe operation of power system. We comprehensively analyzed the developing states, the existed problems in analysis methods and measures of transmission line lightning protection, and discussed the key issues of transmission line lightning protection in China that should be studied. The lightning protection measures are divided into back-up type and leading-type methods, so-called back-up type method is used in lightning protection of transmission line in China, which complicates lightning protection;but the so-called leading-type method is used in other countries, which simplifies lightning protection. The lightning protection measures for different sections of transmission lines should be comprehensively estimated and proposed by considering the micro-topographical feature and the regional performances of lightning parameters along transmission line. The lightning protection should be fully considered in transmission line design, reducing shielding angle of overhead wire, decreasing grounding resistances of tower footings, and suitably installing line surge arresters are fundamental methods of lightning protection of new transmission line.

关键词： Electric lines

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An evolution model with high proportion of renewable energy

An evolution model with high proportion of renewable energy

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Chinese control Conference (CCC)

作者： Weiqi Zhang Xinyan Zhang Yukai Xia Shaowei Huang Jinyu Xiao Chang Lu Shengwei Mei College of electrical engineering Xinjiang University Wulumuqi Xinjiang CN State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing Beijing CN State Power Economic Research Institute Beijing China

Compared with other conventional energy sources, renewable energy, which results in less pollution and has numerous resources, is a significant factor in addressing the current issues of the serious environmental pollution and the resource depletion. Large-scale renewable energy connected to the grid could lead to a the change of the morphological structure and the operation modes of energy transmission. While current power grid evolution models did not consider the characteristics of renewable energy in the evolution strategy. The expansion mechanism of the future transmission network with a high proportion of renewable energy is studied in this paper. The operation cost including renewable energy curtailment are optimized using the production simulations, where the stochastic and intermittent of wind and solar energy are modeled. And the dual variable information is adopted to drive the grid upgrading. The expansion strategies for power grid of Zhejiang province in China are analyzed to balance the construction cost and curtailment cost of renewable energy.

关键词： power grids Load modeling Renewable energy sources Wind power generation Economics Production

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Research on Characteristics of Surface Electric Field on Transmission Lines under Lightning Stroke

Research on Characteristics of Surface Electric Field on Tra...

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第七届亚太防雷国际会议

作者： Zhanqing Yu Zhizhao Li Qian Li Chijie Zhuang Rong Zeng Yong Zhang Yongli Liao State Key Lab of Control and Simulation of Power Systems and Generation EquipmentsDepartment of Elec Department of Mathematical Sciences Tsinghua UniversityHaidian DistrictBeijing 100084China Electric Power Research Institute CSGGuangzhou China

Lightning is a major cause of power interruptions in power transmission *** the Leader Progression Model is an advanced method to evaluate the shielding failure probability of transmission *** the surface electric field on phase conductors and ground wires precisely is important, because the surface electric field has great effect on the upward leader *** this paper, the influence of lightning current and some other factors on surface electric field were analyzed.

关键词： surface electric field transmission lines leader progression model UHVAC

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