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Transient interaction of HVAC and HVDC in converter station in HVDC, IV: Effects of DC sides on AC sides

Gaodianya Jishu/High Voltage Engineering 2011年第7期37卷 1590-1597页

作者： Chen, Shui-Ming Yu, Zhan-Qing Huang, Lu-Lu Xie, Hai-Bin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

China AC-DC power systems are interconnected to form a huge power grid. The nanoseconds, microseconds, milliseconds electromagnetic transient were generated due to AC-DC system operation and fault, the DC converter valve movement, the load generated by changes in the interaction of AC-DC interconnected system electromagnetic transient, which can pose a hazard on AC and DC power systems, in particular, can lead to the commutation of DC system failures and atresia such serious incidents. Based on the broadband characteristics model which can accurately reflect the existing AC-DC interconnected system electromagnetic transient characteristics of the key components, we applied the PSCAD/EMTDC platform to establish a computational model, and revealed DC side electromagnetic transient interaction on AC side. The results show that the DC system has little effect on AC system electromagnetic transient, In various types of failures, the overvoltage produced at side of 750 kV, 330 kV lines and bus are in the allowable range.

关键词： HVDC power transmission

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A DC-link Voltage control Scheme for Single-phase Grid-connected PV Inverters

A DC-link Voltage Control Scheme for Single-phase Grid-conne...

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2011 IEEE Energy Conversion Congress and Exposition (ECCE 2011)

作者： Fanbo He Zhengming Zhao Liqiang Yuan Sizhao Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781457705427;9781457705410

A fast DC-link voltage controller is desirable to reduce the DC-link capacitor for PV inverters. This paper proposes a method for single-phase grid-connected PV inverters to remove the ripple component from the DC-link voltage signal and a scheme to regulate the DC-link voltage based on energy-balance analysis. The proposed scheme provides excellent dynamic performance as well as a function to prevent DC-link overvoltage by limiting the input power, which is verified by both simulation and experiments.

关键词： DC link Polydnaviridae dc-link capacitor Inventors Voltage regulators dynamic characteristics DC link voltage Scheme Voltage regulation link voltage

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Fault diagnosis of direct-drive wind turbine based on support vector machine

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Journal of Physics: Conference Series 2011年第1期305卷

作者： X L An D X Jiang S H Li J Chen State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 100084 China

A fault diagnosis method of direct-drive wind turbine based on support vector machine (SVM) and feature selection is presented. The time-domain feature parameters of main shaft vibration signal in the horizontal and vertical directions are considered in the method. Firstly, in laboratory scale five experiments of direct-drive wind turbine with normal condition, wind wheel mass imbalance fault, wind wheel aerodynamic imbalance fault, yaw fault and blade airfoil change fault are carried out. The features of five experiments are analyzed. Secondly, the sensitive time-domain feature parameters in the horizontal and vertical directions of vibration signal in the five conditions are selected and used as feature samples. By training, the mapping relation between feature parameters and fault types are established in SVM model. Finally, the performance of the proposed method is verified through experimental data. The results show that the proposed method is effective in identifying the fault of wind turbine. It has good classification ability and robustness to diagnose the fault of direct-drive wind turbine.

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Nonlinear dynamic characteristic analysis of a vertical mass unbalanced rotor

Nonlinear dynamic characteristic analysis of a vertical mass...

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23rd International Congress on Condition Monitoring and Diagnostic Engineering Management, COMADEM 2010

作者： An, Xueli Jiang, Dongxiang Liu, Chao Zhao, Minghao State Key Laboratory of Control and Simulation of Power System Generation Equipment Department of Thermal Engineering Tsinghua University Beijing China

ISBN: (纸本)9784883254194

The dynamic properties between torsional and bending vibrations of a vertical mass unbalanced rotor are described. The equation of rotor system motion is obtained by Lagrangian dynamics without considering the external actuating forces and torque, shows coupling effect and nonlinear interaction between the rotor system bending and torsional vibrations. An attempt of theoretical analysis and numerical simulation is made to reveal dynamic characteristics of a rotor system. Theoretical analysis of the rotor dynamic equations based on perturbation theory indicates that at stable state of vibration the coupled effect on the rotor system is nonexistent and the bending vibration becomes equal amplitude with shafting speed at stable vibration state. While the torsional vibration keeps on attenuating until it stops. In addition, the numerical simulation results to the dynamic equations, show that coupled torsional and bending vibrations are induced by mass eccentricity, and coupled effect can only be found in vibration initial state of the rotor system. Other numerical simulation results are consistent with the theoretical analysis.

关键词： Perturbation techniques

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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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作者： Yu, Hong-Qiao Chen, Shui-Ming Yang, Peng-Cheng 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. © 2010 Chinese Soc for Elec Eng.

关键词： Electrolysis

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Experimental investigation and analysis for gearbox fault

Experimental investigation and analysis for gearbox fault

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2010 2nd World Non-Grid-Connected Wind power and Energy Conference, WNWEC 2010

作者： Li, Shaohua Jiang, Dongxiang Zhao, Minghao State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424489213

As an important component of a wind turbine drive chain, the high failure rate of the gearbox can have a serious impact on the operation of wind turbine units. The fault diagnosis of the gearbox is therefore important for the safety of wind turbine units. In this paper, a gearbox experiment rig was built, experiments on the gear surface spalling fault were held on the rig under laboratory conditions, the shaft vibration displacement signals were collected, related vibration signals were analyzed by time domain, amplitude domain, frequency domain and wavelet analysis, and the results of different analysis methods were compared. The results show that the waveform of normal and fault signals are similar, the amplitude of the signals will change while the fault happens, and the wavelet analysis is more effective than frequency domain analysis on gearbox fault features extraction. © 2010 IEEE.

关键词： Frequency domain analysis

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Design and implementation of the high efficiency photovoltaic system with solid state lighting

Design and implementation of the high efficiency photovoltai...

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作者： Hu, Xianlai Yuan, Liqiang Chen, Jian Zhao, Zhengming 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)9788986510119

Photovoltaic application of LED lighting has been a hot trend in residential illumination, for it integrates the advantages of both the PV systems and LED lights. However, it has a series of problems, such as high thermal loss, poor reliability, and a short life span. To address these problems, this paper presents a deep research on the whole system from a low-cost, high-efficiency and long-life point of view. A main circuit integrating maximum power point tracing (MPPT) control and battery management, as well as a double-loop control for LED load is developed. A set of protection system is applied to ensure high reliability of the system. The control strategies are tested on the demonstrator and prove to be effective.

关键词： Integrating circuits

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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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Nanosecond-pulse dielectric barrier discharge using magnetic compression solid-state pulsed power

Nanosecond-pulse dielectric barrier discharge using magnetic...

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IEEE International power Modulator and High Voltage Conference

作者： Shao, Tao Yu, Yang Zhang, Cheng Niu, Zheng Zhang, Dongdong Wang, Jue Sun, Yaohong Yan, Ping Zhou, Yuanxiang Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Electrical Engineering Department Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424471294

Dielectric barrier discharge excitated by unipolar pulsed power is a promising approach for producing non-thermal plasma at atmospheric pressure. A magnetic compression solid-state pulse power generator is used to produce dielectric barrier discharge (DBD). The generator is capable of providing repetitive pulses with the voltage of up to 30 kV and duration of 70 ns at a 300 resistive load. This paper illustrates electrical characteristic and luminous emissions of DBD excitated by repetitive unipolar nanosecond-pulses in atmospheric air. Different from common DBD excitated by high-voltage AC sources, discharge current of DBD in the experimental investigation can be on an order of tens of amperes. When the DBD is created using two liquid electrodes, the luminous emissions from the obverse and flank sides of liquid electrodes show that no filament is observed and the discharge is homogeneous and diffuse in the whole discharge regime. © 2010 IEEE.

关键词： Dielectric barrier discharge

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