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International Conference on Electrical Machines and systems (ICEMS)

作者： Xianlai Hu Liqiang Yuan Jian Chen Zhengming Zhao State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

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： Light emitting diodes Batteries Discharges MOSFET circuits Lighting Photovoltaic systems Snubbers

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Vibration characteristics on a wind turbine rotor using modal and harmonic analysis of FEM

Vibration characteristics on a wind turbine rotor using moda...

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

作者： Chao Liu Dongxiang Jiang Jie Chen State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing China

A wind turbine rotor system containing blades has its own characteristics. The vibration characteristics of blades with special airfoil can influence the vibration characteristics of the rotor system. This paper analyzed the vibration characteristics of a wind turbine rotor including blades with two-dimensional airfoil. The Finite Element Method (FEM) is applied to establish the rotor model, with the purpose that the FEM can adjust complex blades airfoils and acquire the details of the blades vibration characteristics. The modal characteristics are extracted based on the wind turbine model established in the laboratory. Using harmonic analysis of FEM, the excitation forces on the blades caused by the stochastic wind load are imposed on the rotor model and the stable response of the rotor system is calculated using ANSYS. Then the vibration characteristics are analyzed and the characteristics of the harmonic response are studied under different phases of the circumferential and axial forces.

关键词： Blades Wind turbines Rotors Finite element methods Harmonic analysis Force Solid modeling

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X-ray backlighting of wire expansion and plasma merging of z-pinch load with 10-40kA/wire

X-ray backlighting of wire expansion and plasma merging of z...

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IEEE International Conference on Plasma Science (ICOPS)

作者： Xinlei Zhu Xiaobing Zou Ran Zhang Shen Zhao Haiyun Luo Xinxin Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

It is well known that the evolution of wire array z-pinch load can be divided into several phases: wire explosion, inter-wire plasma merging, implosion and stagnation. In this paper, experiments with x-pinch backlighter to study the initial wire explosion and inter-wire plasma merging were performed on the pulsed power generator PPG-I at Tsinghua University. An x-pinch (13-25μm Mo and 5-18μm Wu wires) used as soft x-ray source was installed in the centre between the output main electrodes of PPG-I generator, and the object z-pinch load was installed in one of the return current posts. The object z-pinch load consists of 2-4 tungsten wires of 5-18 μm diameter, 12 mm long, and 2 mm spacing between wires. The evolution images of wire explosion and inter-wire plasma merging were recorded with high resolution x-ray film, which was covered with a mass step-wedge filter to calibrate the mass density distribution of wire explosion and inter-wire merging plasma. Based on extensive discharge tests, the time sequence of backlighting images of z-pinches was obtained. In the paper, we also discussed how to determine the interface between high-density wire core and low-density surrounding plasma, and then presented the expansion rates of high density wire core and the mass density distribution of inter-wire plasma under different z-pinch current.

关键词： Wires Plasmas Merging Explosions Educational institutions Generators Radio access networks

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Experimental investigation and analysis for gearbox fault

Experimental investigation and analysis for gearbox fault

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

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

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.

关键词： Shafts Spectrogram Gears Frequency domain analysis Wind turbines Amplitude modulation Feature extraction

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Modeling and Operation of the power-to-Gas System for Renewables Integration: A Review

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CSEE Journal of power and Energy systems 2018年第2期4卷 168-178页

作者： Xuetao Xing Jin Lin Yonghua Song You Zhou Shujun Mu Qiang Hu State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijing 100084China Department of Electrical and Computer Engineering University of MacaoMacaoChina Department of Electrical Engineering Tsinghua UniversityBeijing 100084China National Institute of Clean and Low Carbon Energy Beijing 102211China Tsinghua-Sichuan Energy Internet Research Institute Chengdu 610213China

power-to-Gas(P2G)plays an important role in enhancing large-scale renewable energy integration in power *** an emerging inter-disciplinary subject,P2G technology requires knowledge in electrochemistry,electrical engineering,thermodynamic engineering,chemical engineering and system *** at P2G modeling and operational problems concerning the research field of power systems and the energy internet,this paper briefly reviews the main technologies and application potentials of the P2G system,and makes systematic summaries of major progresses related to P2G’s integration into the power grid in a bottom-top manner,including the modeling of high/room-temperature electrolysis cells,steady-state/dynamic optimization control of the P2G system,P2G’s integrated model and operational strategies at the grid *** the final part of this paper,suggestions are put forward on future research directions of P2G systems from the aspects of modeling and operational optimization.

关键词： Electrolysis cell multi-energy network modeling and operation power-to-gas

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A computer control and monitoring system for high power converters

A computer control and monitoring system for high power conv...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Rong Yi Zhenming Zhao Xiaoying Sun Liqiang Yuan Jue Qian Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

ISBN: (纸本)7506274078

Computer control and monitoring system (CCMS) is quite important for high power converters (HPCs) operation. This paper presents a novel CCMS, which integrates a database management system (DBMS) into the monitoring software to get the beneficial features such as simple configuration and compact structure. In its communication system, an advanced optical fiber communication (OFC) technology is applied and priority-based communications is proposed to improve the reliability and the real time of the communications. Furthermore, a friendly standard Windows human-machine interface (HMI) is provided. The reliability and performance of the system are verified by system tests and practical operations.

关键词： control systems Computerized monitoring Communication system control Electromagnetic interference Diodes power engineering computing power system simulation Optical fiber communication Real time systems Man machine systems

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Optimal design of the back-to-back IGBT-based converter with the concept of systematic safe operating area

Optimal design of the back-to-back IGBT-based converter with...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Gaoyu Zou Zhengming Zhao Liqiang Yuan Xuesong Wang Ting Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

The key parameters of SOA (safe operating area) of semiconductor devices are hard to be measured when converter is operating, which is not helpful to protect converter at any time. On the other hand, surplus estimating method is widely used to design the main circuit. In order to guarantee the whole system works safely and improve utilization rate of devices, the concept of SSOA (systematic safe operating area) is presented. By determining the relationship of key parameters between devices and converter, the expression of SSOA is described quantitatively. Then it is implemented as a basic rule to design a back-to-back converter based on IGBT for 55kW induction motor optimally. Rated value of DC-link voltage and grid filter of the system is obtained reasonably as well.

关键词： Inductance Insulated gate bipolar transistors Rectifiers power harmonic filters Semiconductor optical amplifiers Induction motors

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Design, simulation and analysis of the low stray inductance bus bar for voltage source inverters

Design, simulation and analysis of the low stray inductance ...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Liqiang Yuan Hualong Yu Xuesong Wang Zhengming Zhao State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

Hard-switching technique under the high voltage and high current is one of main trends of high power inverters. Under this switching mode, the stray parameters of the commutating loops, especially the stray inductance of the DC bus bar, have significant influence on the switching process, electromagnetic interference and component stress of the semiconductor switches. It becomes one of the key points for the safe operation of inverters. Based on an actual 55 kW inverter, the design, simulation and analysis for its bus bar is described in this paper. The bus bar model is built with the method of Partial Element Equivalent Circuit (PEEC), and the stray parameters are extracted from PEEC model and applied in the circuit simulation. Compared with the experimental results, the modeling validity is proved, and the simplified modeling process and design principles for complex physical bus bar are presented.

关键词： Integrated circuit modeling Equivalent circuits Inductance Inverters Capacitance Conductors Analytical models

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Online detection method for internal fault of permanent magnet synchronous generator based on new type of search coil

Online detection method for internal fault of permanent magn...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Daizong Tian Yuguang Sun Wei Du Lin Gui State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing People's Republic of China

ISBN: (纸本)9781728133997

In order to overcome the limitations of traditional fault diagnosis methods, this paper studies the online detection method of internal faults for permanent magnet synchronous generators (PMSG) based on the new type of search coil. Taking a 6-phase PMSG as an example, two types of search coil are fixed in the air gap according to the pole-pair number and the armature winding structure. A calculation method for the induced EMF of the new type of search coil in the PMSG is presented, which is verified by the model machine experiment. simulation and experiments on the 6-phase PMSG show that the open-circuit voltage of the search coil was zero under normal operation, while an obvious EMF was induced in the search coil once the internal asymmetry fault occurred. And according to the period of the voltage, the fault could be distinguished between the internal fault of the stator winding and the demagnetization fault. Based on the new type of search coil, this paper provides a new way for online monitoring of internal faults of PMSGs.

关键词： Circuit faults Stator windings Harmonic analysis Magnetic fields Windings Generators Demagnetization

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A Review on Overvoltages in Microgrid

A Review on Overvoltages in Microgrid

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

作者： Shuiming Chen Hongqiao Yu Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

Now microgrid has aroused increasing attention due to energy sustainable development and the development of distributed generations (DG), such as micro-turbines, gas turbines, wind power, photovoltaic and fuel cells. This paper introduces the basic structure of microgrid and summarizes the overvoltages that can occur in microgrid, including ground fault overvoltages, resonant overvoltages, overvoltage related to voltage regulation, switching overvoltages of inner microgrid, transfer overvoltages from distribution network (such as lightning and switching overvoltages). By analysis, this paper obtains the following conclusion: resonant overvoltages and lightning stroke transfer overvoltages are the most serious for microgrid.

关键词： Surges Resonance Lightning Sustainable development Distributed control Wind turbines Wind energy Photovoltaic systems Solar power generation Fuel cells

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