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Flexible unbalanced control with peak current limitation for virtual synchronous generator under voltage sags

Journal of Modern power systems and Clean Energy 2018年第1期6卷 61-72页

作者： Tianwen ZHENG Laijun CHEN Yan GUO Shengwei MEI State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Qinghai Key Lab of Efficient Utilization of Clean Energy New Energy Photovoltaic Industry Research Center Qinghai University

Virtual synchronous generator(VSG)is gridfriendly for integrating distributed generations(DGs)since it can emulate the operation mechanism of traditional synchronous generator(SG).However,the traditional VSG control strategy,which is mainly suitable for balanced voltage conditions,may lead to power oscillations,current unbalance and even overcurrent under unbalanced voltage *** overcome this difficulty,a flexible unbalanced control with peak current limitation for VSG under unbalanced operating conditions is *** on the basic VSG control algorithm,the control strategy integrates two novel control modules,which are current reference generator(CRG)and power reference generator(PRG).The proposed control strategy can flexibly meet different operation demands,which includes current balancing,constant active or reactive *** the injected currents are kept within safety values for a better utilization of the VSG power ***,the experimental platform is *** results demonstrate the validness and effectiveness of the proposed control strategy.

关键词： Virtual synchronous generator Unbalanced control Current reference generator power reference generator Voltage sags

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Experimental investigation and analysis of some common faults for wind turbine 68

Experimental investigation and analysis of some common fault...

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68th Society for Machinery Failure Prevention Technology Conference: Technology Solutions for Affordable Sustainment, MFPT 2014

作者： Yang, Wenguang Li, Shaohua Jiang, Dongxiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing100084 China

This paper focus on the fault characteristic by experimental research. A test rig is built for the direct driving stall fix-pitch horizontal axis wind turbine. 8 signals are collected by the experiment system, including wind speed, rotor rotational speed, shaft torque, the output electric power, vertical and horizontal vibration displacement of main shaft, vibration acceleration of the front bearing pedestal and the back bearing pedestal. 11 common wind turbine faults are researched by experiment. These faults are rotor mass imbalance, pneumatic asymmetry, airfoil changed, yaw fault, shaft horizontal misalignment, shaft vertical misalignment, front bearing pedestal looseness, rear bearing pedestal looseness, front bearing outer ring fault, front bearing inner ring fault, and front bearing roller fault. Several signal analysis methods, which are waveform analysis, orbit analysis, amplitude domain analysis, frequency domain analysis and envelope spectrum analysis, are adopted to extract characteristics from vibration signals. The influence on output power and vibration characteristics of these faults is presented by comparing with normal operation. The findings can be used to guide wind turbine fault diagnosis in engineering applications.

关键词： Wind

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H∞ analysis method for the small signal stability of power system

H∞ analysis method for the small signal stability of power ...

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26th Chinese control Conference, CCC 2007

作者： Mei, Shengwei Che, Wenyan State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)7900719229

This work is concerned with the small signal stability problem in multi-machine systems. By means of H∞ theory, firstly the math model with disturbances is constructed;and secondly, the excitation control law for each generator is designed based on solving Riccati Equation. Finally, simulations performed on 4-machine system shows that the proposed H ∞ method has more advantages over LQR method in both damping ratio and H∞ norm of the corresponding closed-loop system and so can enhance the small signal stability of power system greatly.

关键词： Electric power systems

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Finite element analysis on damping characteristics for vibro-impact of integral shroud blade

Finite element analysis on damping characteristics for vibro...

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Joint Conference on Society for Machinery Failure Prevention Technology Conference, MFPT 2015 and ISA's 61st International Instrumentation Symposium, IIS 2015 - Technology Evolution: Sensors to systems for Failure Prevention

作者： Wang, Nan-Fei Jiang, Dong-Xiang Chen, Jing-Ming State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing100084 China

By using theoretical and experimental methods, dynamic characteristics of turbine blades with integral shrouds are studied, and the mechanism of vibro-impact and the effective factors of integrally shrouded blades are mainly presented. By means of finite element calculation, the dynamic frequencies and vibration mode shapes of single shrouded blade are explored under different rotating speeds. The three-dimensional entity unit integral dynamics equation of blades with vibro-impact are established by using nonlinear damping model in this paper. With the help of 3D software Solidworks, the solid model of blade is built. With the aid of FEA software ANSYS, the dynamics and static characteristics of single blade are obtained. Meanwhile, by building the model to set different shroud clearance and exciting force amplitude, the relationships between displacement of blade tip and influence of such as blade shroud clearance and exciting force amplitude are demonstrated. The results of the analysis indicate that the collision structural is an ideal damping structure. As the clearance between blade shrouds is smaller, the damping effect is better. Moreover, results show that blades adopting collision damping mechanism can achieve good damping effect when the blades are subjected to greater exciting force.

关键词： Finite element method

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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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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 lab.ratory. 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 stress and strain for fatigue cumulation evaluation in turbine generator shafts due to torsional vibration

Study on stress and strain for fatigue cumulation evaluation...

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

作者： Jiang, Dongxiang Liu, Chao An, Xueli 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)9784883254194

The cracks emerged in a fossil-fired power plant in China in 2008 and several similar crack accidents had been detected in nuclear turbines in USA before. The possible causes of the cracks are analyzed in previous study while the torsional vibration is one of the most significant factors. The paper analyzes the impact of torsional vibration using the practical running data in some turbine generator unit. Based on the transient response analysis under emulational subsynchronous oscillation model simplified from the practical network, the torques acted on the coupling section are analyzed. Then the stress and strain field is calculated for local dangerous point search in Zone of Vulnerability (ZoV) and the fatigue damage criterion determination. Manson-Coffin equation is used to ascertain whether it is high-cycle fatigue or low-cycle fatigue and the fatigue data from standard test specimen is used. The method using local stress and strain analysis as well as fatigue damage cumulation study may establish a novel way to diagnose the crack in an early stage.

关键词： Transient analysis

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Diagnosis method for rub-impact fault of rotating machinery based on EMD and Hilbert envelop spectrum

Diagnosis method for rub-impact fault of rotating machinery ...

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Joint Conference on Machinery Failure Prevention Technology Conference, MFPT 2016 and ISA's 62nd International Instrumentation Symposium, IIS 2016

作者： Wang, Nan-Fei Jiang, Dong-Xiang Han, Te State Key Laboratory of Control and Simulation of Power System and Generation Equipments Departments of Thermal Engineering Tsinghua University Beijing100084 China

Aiming at the characteristics of the casing vibration acceleration signal of rotating machinery with rubbing fault, a diagnosis method based on EMD (empirical mode decomposition) and Hilbert envelop spectrum is put forward. When the rubbing fault occurs between the rotor and the stator, the vibration acceleration signals from the casing of the rooting machinery will present amplitude-modulated feature due to the periodical rub-impact between the rotor and the stator. However, it is relatively difficult to extract the rub-impact feature since the rub-impact signal in the process of transferring to the casing is always buried in the noise and background signals. In this paper, by means of the powerful capability of EMD and Hilbert envelop spectrum in processing nonlinear signal can accurately describe nonlinear behaviours, the fault signal is adaptively decomposed by EMD to acquire intrinsic mode functions (IMF) containing obvious feature of amplitude modulation. Then some of the sensitive IMF components are transformed by FFT and their Hilbert spectrum are analysed. The analysis results from the experimental signal show that the EMD provides an effective and adaptive method to obtain 'purified' casing vibration acceleration signal, which demonstrates the transient casing vibration more precisely and vividly, decreasing misinterpretation of the machine running condition. Therefore, the EMD approach can be applied to the single-point rubbing fault diagnosis of the rotor systems efficiently. © 2016, Society for Machinery Failure Prevention Technology. All rights reserved.

关键词： Empirical mode decomposition

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The analysis of stator MMF and the calculation of rotor losses in a 12-phase high speed asynchronous generator

The analysis of stator MMF and the calculation of rotor loss...

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ICEMS 2005: 8th International Conference on Electrical Machines and systems

作者： Cheng, Luo Xiangheng, Wang Puqi, Ning Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing 100084 China

ISBN: (纸本)7506274078

To research the influence of multi-phase winding to generators and calculate the losses in solid rotors, the stator mint of a 12-phase asynchronous generator have been well analyzed and finite element method by ANSYS software has been applied to get the accurate losses in the rotor through both harmonic and transient 2-D analysis. The relationship between stator harmonic current and stator harmonic mint has been deduced and proved through ANSYS software to some extent, and rotor losses produced by both stator fundamental current and stator total current have also been obtained and compared. The results show that 12-phase stator winding with appropriate short pitch can effectively eliminate or reduce many mmf produced by stator fundamental and harmonic current and rotor losses are mainly produced by stator fundamental current.

关键词： Asynchronous generators

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Lightning overvoltage suppression of power transformer in UHV GIS by ferromagnetic ring

Lightning overvoltage suppression of power transformer in UH...

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2011 7th Asia-Pacific International Conference on Lightning, APL2011

作者： Zhang, Xiao He, Jinliang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457714665

Lightning overvoltage protection is of great importance to the safety of UHV GIS. The widely used arresters can only suppress the magnitude of lightning overvoltage but lack efficiency on alleviating the steepness. In practice, insulation failure of UHV transformer is often reported. A new protection method is proposed in this paper using ferromagnetic ring as supplement to arresters to suppress lightning overvoltage in UHV GIS. Moreover, equivalent model based on the characteristic of ferromagnetic material and factual dimension of the ring is established for calculation. simulation of an actual 1000kV GIS is carried out to thoroughly evaluate the lightning overvoltage suppressing effect of ferromagnetic rings with different materials and structure dimensions. © 2011 IEEE.

关键词： power transformers

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