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International Conference on power system Technology (powerCON)

作者： An, Haiyun Jia, Hongjie Yu, Xiaodan Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin 300072 China

ISBN: (纸本)9781424459407

In this paper, Lyapunov stability theory and linear matrix inequality (LMI) method are used to analyze the delay-dependent robust stability of power systems with multiple time delays. An improved delay-dependent robust stability criterion for power system with multiple time delays is presented. A proper Lyapunov functional is firstly constructed based on Lyapunov-Krasovskii theory. And, in the deduction of its derivative function along the system trajectory, some necessary slack variables are introduced so as to reduce its conservatism. Then the method is applied to the robust stability analysis for power system with time-varying delays and uncertainties. It can be found the present method is correct, effective and with less conservatism. ©2010 IEEE.

关键词： Stability criteria

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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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Total supply capability and ideal total supply capability for distribution system: Definition, model and algorithm

Total supply capability and ideal total supply capability fo...

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作者： Xiao, Jun Zhai, Wei Gu, Wenzhuo Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University 300072 China

ISBN: (纸本)9781457700668

This paper proposes the definition, model and algorithm of two quantitative indices named the Total Supply Capability (TSC) and Ideal Total Supply Capability (ITSC) for distribution planning. The TSC of a distribution system is comparable to Total Transfer Capability (TTC) in transmission systems, which is defined as the maximum load it can serve under the N-1 guideline for distribution systems, taking into account the capacities of the substation transformers, network link topology, link capacity, and other constraints. The ITSC of a distribution system is the calculated TSC which considers capacities of tie lines are large enough. Mathematical models for TSC and ITSC are set up and procedures to calculate TSC and ITSC are presented. Based on TSC and ITSC calculation, a concept named Potential Supply Capability(PSC) is proposed, which depicts the "potential" or "hidden" TSC of the distribution system. Finally, TSC and ITSC calculation have been performed in a test system with promising results. The case study has shown that TSC and ITSC algorithms are efficient approaches to analyze and evaluate the existing distribution system. © 2010 Chinese Soc for Elec Eng.

关键词： Electric utilities

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Modeling and simulation of grid-connected hybrid photovoltaic/battery distributed generation system

Modeling and simulation of grid-connected hybrid photovoltai...

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作者： Ding, Fei Li, Peng Huang, Bibin Gao, Fei Ding, Chengdi Wang, Chengshan Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China

ISBN: (纸本)9781457700668

Photovoltaic(PV)generation is the technique which uses photovoltaic cell to convert solar energy to electric energy. Nowadays, PV generation is developing increasingly fast as a renewable energy source. However, the disadvantage is that PV generation is intermittent for depending on weather conditions. Thus, the battery energy storage is necessary to help get a stable and reliable output from PV generation system for loads and improve both steady and dynamic behaviors of the whole generation system. The paper presents detailed transient models of the grid-connected PV/Battery hybrid generation system, and all these models are simulated by using MATLAB/Simulink. PV array is firstly connected to the common dc bus by a boost converter, where the battery is also connected by a bi-directional DC/DC converter, and then integrated into the ac utility grid by a common DC/AC inverter. Maximum power point tracking helps PV array to generate the maximum power to the grid, and the battery energy storage can be charged and discharge to balance the power between PV generation and utility grid. Finally, different cases are simulated, and the results have verified the validity of models and control schemes. © 2010 Chinese Soc for Elec Eng.

关键词： Solar energy

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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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Crack Growth Prediction of the Steam Turbine Generator Shaft

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

作者： Dongxiang Jiang Chao Liu State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 People's Republic of China

The power network in China is encountering great changes and large-scale network is increasingly implemented for long distance power transmission as well as various kinds of power electronic devices, which bring in the risk of the torsional vibration of the turbine generator shafts, may cause the fatigue damage and cracks in the product life cycle. The paper analyzed the failed coupling of some 600MW steam turbine generator and calculated the local stress of the assembly under torsional load caused by the network disturbance. Then the crack propagation was analyzed with the predicted crack initiation position and crack propagation routine. The assembled coupling contains shaft, coupling and keys with interferences between the parts. Therefore the contact analysis was included. Extended Finite Element Method (X-FEM) is used to calculate the crack propagation and that the mesh needs not to be regenerated with the crack propagation, which is beneficial for engineering applications.

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Capacity credit evaluation of wind power with sequential Monte Carlo method

Capacity credit evaluation of wind power with sequential Mon...

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2010 International Conference on E-Product E-Service and E-Entertainment, ICEEE2010

作者： Kong, Xiangyu Cui, Kai Jia, Hongjie Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin China State Power Economic Research Institute Beijing China

ISBN: (纸本)9781424471614

Wind can be considered as an interesting alternative to fossil fuels, but as a power source, is both intermittent and diffuse. It is necessary to calculate wind equivalent capacities in order to introduce a coherent evaluation of wind production in the management of the centralized production park. Base on the sequential Monte Carlo simulation technique for wind speeds, an auto-regressive and moving average time series model was used to simulate wind power. And a capacity credit evaluation of wind power method was proposed, which provides the existence probability of wind generation possible outage capacity levels. A number of sensitivity analyses were presented with case studies to illustrate possible applications of the proposed method. ©2010 IEEE.

关键词： Wind power

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

作者： Liu, Chao Jiang, Dongxiang Chen, Jie State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424489213

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. © 2010 IEEE.

关键词： Harmonic analysis

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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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Modal analysis of wind turbine tower

Modal analysis of wind turbine tower

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

作者： Chen, Jie Jiang, Dongxiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424489213

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. © 2010 IEEE.

关键词： Modal analysis

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