检索结果-内蒙古大学图书馆

2010 International Conference on Electrical Machines and systems, ICEMS2010

作者： Xia, Yonghong Wang, Shanming Ma, Mingyuan Hao, Liangliang Qiu, Arui Huang, Shaogang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Department of Electrical and Automatic Engineering Nanchang University Nanchang Jiangxi 330031 China

A novel method, which utilizes harmonic for excitation, is presented to adjust the air-gap magnetic field for permanent magnet synchronous machine. The structure and basic principles of the hybrid excitation PM synchronous generator(HEPMSG) are introduced. The no-load and on-load electromagnetic field are calculated based on finite element method, and the waveform and effective value of the winding voltage and characteristics of the machine are gained for different loads. Calculation results demonstrate the new hybrid excitation scheme is feasible. This new method combines the advantages of PM machines and electrical excitation machines. The machine removes the brushes and slip rings, which makes permanent magnet machine keep simple and highly reliable.

关键词： Windings Harmonic analysis Stator windings Rotors Reactive power Power system harmonics

来源：评论

学校读者我要写书评

暂无评论

An Efficient and Stable Ionic Liquid system for Synthesis of Ethylene Glycol via Hydrolysis of Ethylene Carbonate

引用

Chinese Journal of Chemical engineering 2010年第6期18卷 962-966页

作者： MENG Zhenying SUN Jian WANG Jinquan ZHANG Jianxin FU Zengzeng CHENG Weiguo ZHANG Xiangping State Key Laboratory of Multiphase Complex System Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China College of Chemistry and Chemical Engineering Henan Universitv Kaifeng 475001 China School of Chemical and Environmental Engineering China University of Mining & Technology (Beijing) Beijing 100083 China

An ionic liquid system of [Bmim]X/[Bmim]OH(X Cl,BF4,and PF6,) was developed for the hydroly-sis of ethylene carbonate to ethylene glycol. The important parameters,such as the variety of ionic liquids,molar ratio of [Bmim]X to [Bmim]OH,amount of ionic liquid,molar ratio of water to ethylene carbonate,reaction tem-perature,pressure and reaction time,were investigated systematically. Excellent yield(>93%) and high selectivity(99.5%) of ethylene glycol were achieved. Under the optimum reaction conditions,the ionic liquid system could be reused at least five times and the selectivity of ethylene glycol remained higher than 99.5%.

关键词： ethylene carbonate ethylene glycol hydrolysis ionic liquids catalysis

来源：评论

学校读者我要写书评

暂无评论

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

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

Experimental investigation and analysis for gearbox fault

Experimental investigation and analysis for gearbox fault

引用

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

来源：评论

学校读者我要写书评

暂无评论

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

Design and implementation of the high efficiency photovoltai...

引用

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

来源：评论

学校读者我要写书评

暂无评论

A Review on Overvoltages in Microgrid

A Review on Overvoltages in Microgrid

引用

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

来源：评论

学校读者我要写书评

暂无评论

DC pre-excitation application in three-phase induction motor drive system

DC pre-excitation application in three-phase induction motor...

引用

IEEE International Symposium on Power Electronics for Distributed Generation systems (PEDG)

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

Due to the current restriction of semiconductor devices, the start-up is an extremely important process in the ASD (adjustable speed drive) system. DC pre-excitation is one of the effective solutions for increasing the starting torque and depressing the starting inrush current. However the effect of DC pre-excitation would be discounted if it could not be compatible with the induction motor drive control system. Also the stability of the DC pre-excitation application is related to its operational mode. This paper addresses the principle of DC pre-excitation and excavates its relationship with current control. The method to improve the stability of DC pre-excitation effectively shielding EMI is detailed. The relevant study has been implemented in a control system for a 55 kW and 160 kW induction motor and the simulation and experimental results validate the effectiveness of the proposed design method.

关键词： Induction motors Torque DC motors Electromagnetic interference Process control Variable speed drives Switches

来源：评论

学校读者我要写书评

暂无评论

Approaches to enhance discrete control algorithms serving for motor drive system

Approaches to enhance discrete control algorithms serving fo...

引用

IEEE Energy Conversion Congress and Exposition, ECCE

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

The discrete control technology for AC machine drives is widely applied in the industrial field. This paper aims to excavate new approaches to enhance the discrete control system in AC motor drive systems from following aspects: matching design for discrete subsystems, synchronization in the signal processing and dealing with the restrictions in the voltage output. The proposed approaches are incorporated with three key techniques applied in high performance induction motor drive systems: DC pre-excitation, parameter identification and flux observer with a sensorless control to verify the feasibility. The anti-interference and synchronization procedure in the implementation are also proposed. The experimental results from the test on 55kW/400V and 160kW/400V ASD (Adjustable Speed Drives) systems validate the effectiveness of the proposed approaches.

关键词： Switches Variable speed drives Observers Parameter estimation Pulse width modulation Induction motors

来源：评论

学校读者我要写书评

暂无评论

Predictive DC voltage control for three-phase grid-connected PV inverters based on energy balance modeling

Predictive DC voltage control for three-phase grid-connected...

引用

IEEE International Symposium on Power Electronics for Distributed Generation systems (PEDG)

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

DC voltage control is critical for grid-connected inverters, as it contributes to reduce the DC capacitance and improve system reliability as well as MPPT performance. A predictive control scheme of DC voltage for single-stage three-phase grid-connected PV inverters is proposed based on the analysis of the energy balance relationship in one control period, while AC current is also regulated by predictive control. The proposed scheme provides both good dynamic and steady-state performance. The dynamic response is especially excellent. The DC voltage is adjusted as fast as possible with little overshoot.

关键词： Voltage control Inverters Voltage measurement Regulators Predictive control Steady-state Capacitance

来源：评论

学校读者我要写书评

暂无评论

Modal analysis of wind turbine tower

Modal analysis of wind turbine tower

引用

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

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

As the support structure of wind turbine, the tower bears alternating loads of wind when the wind turbine runs. To ensure the reliability of the wind turbine, it's necessary to carry out modal analysis on the tower, and this would prevent the natural frequency of the tower close to the rated speed of wind turbine. In this paper, finite element analysis of the tower is solved using ANSYS, and the natural frequencies and modes of the tower are presented. After comparing the results of three models, a simple model for modal analysis, which can be calculated in short time, is finally determined.

关键词： Poles and towers Wind turbines Modal analysis Finite element methods Analytical models Material properties Solid modeling

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：