• Title, Summary, Keyword: Electromechanical oscillations

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Analysis of thermally induced vibration of cable-beam structures

  • Deng, Han-Qing;Li, Tuan-Jie;Xue, Bi-Jie;Wang, Zuo-Wei
    • Structural Engineering and Mechanics
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    • v.53 no.3
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    • pp.443-453
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    • 2015
  • Cable-beam structures characterized by variable stiffness nonlinearities are widely found in various structural engineering applications, for example in space deployable structures. Space deployable structures in orbit experience both high temperature caused by sun's radiation and low temperature by Earth's umbral shadow. The space temperature difference is above 300K at the moment of exiting or entering Earth's umbral shadow, which results in structural thermally induced vibration. To understand the thermally induced oscillations, the analytical expression of Boley parameter of cable-beam structures is firstly deduced. Then, the thermally induced vibration of cable-beam structures is analyzed using finite element method to verify the effectiveness of Boley parameter. Finally, by analyzing the obtained numerical results and the corresponding Boley parameters, it can be concluded that the derived expression of Boley parameter is valid to evaluate the occurrence conditions of thermally induced vibration of cable-beam structures and the key parameters influencing structural thermal flutter are the cable stiffness and thickness of beams.

Power System Oscillations Damping by Robust Decentralized DFIG Wind Turbines

  • Surinkaew, Tossaporn;Ngamroo, Issarachai
    • Journal of Electrical Engineering and Technology
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    • v.10 no.2
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    • pp.487-495
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    • 2015
  • This paper proposes a new robust decentralized power oscillation dampers (POD) design of doubly-fed induction generator (DFIG) wind turbine for damping of low frequency electromechanical oscillations in an interconnected power system. The POD structure is based on the practical $2^{nd}$-order lead/lag compensator with single input. Without exact mathematical model, the inverse output multiplicative perturbation is applied to represent system uncertainties such as system parameters variation, various loading conditions etc. The parameters optimization of decentralized PODs is carried out so that the stabilizing performance and robust stability margin against system uncertainties are guaranteed. The improved firefly algorithm is applied to tune the optimal POD parameters automatically. Simulation study in two-area four-machine interconnected system shows that the proposed robust POD is much superior to the conventional POD in terms of stabilizing effect and robustness.

UPFC Model for Stability Study Using IPLAN (IPLAN을 이용한 UPFC 안정도 해석 전산 모형)

  • Kim, Hak-Man;Oh, Tae-Kyoo;Jang, Byung-Hoon;Chu, Jin-Bu
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.3
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    • pp.220-225
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    • 1999
  • This paper presents an UPFC (Unified Power Flow Controller) model for stability study using PSS/E. The proposed UPEC model was implemented by IPLAN which is a high level language. As a control strategy for damping electromechanical oscillations, energy function method was adopted. By the adopted control law, the damping effect is robust with respect to loading condition, fault location and network structure. Furthermore, the control imputs are based on local signals. The effect of control of the UPFC model was demonstrated on an one machine infinite bus system and a two area system.

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Fabrication of 1-3 Piezo-composites with a "Dice & Fill" Method and Characterization of Their Piezoelectric Properties as a Function of Lateral Spatial Scale ("Dice와 fill" 방식을 이용한 1-3 압전복합재의 제조와 횡방향 단위 크기에 따른 압전특성 평가)

  • Kim, Young-Deog;Kim, Kwang-Il;Jeong, Woo-Cheol;Kim, Heung-Rak;Kim, Dong-Su
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.4
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    • pp.354-360
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    • 2002
  • The piezoelectric composites had many advantages in comparison with conventional piezoelectric ceramics and piezopolymers for ultrasonic transducers used in NDT and in medical ultrasionic imaging. The electromechanical coupling coefficient should be high and the acoustic impedance should be low in these applications. However, the cross-coupling with spurious oscillations caused by laterally running plate waves exhibited complex motions in the surface of piezoelectric composites with coarse lateral spatial scale. The thickness mode electromechanical coupling coefficient of 1-3type of piezoelectric compoistes were 0.36 to 0.64, and the acoustic impedance of them were 9.8 to 22.7 MRayl. The lateral resonance frequency of 1-3 type piezoelectric composites shifted to high frequency region with decreasing lateral spatial scale.

Advanced Small-Signal Model of Multi-Terminal Modular Multilevel Converters for Power Systems Based on Dynamic Phasors

  • Hu, Pan;Chen, Hongkun;Chen, Lei;Zhu, Xiaohang;Wang, Xuechun
    • Journal of Power Electronics
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    • v.18 no.2
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    • pp.467-481
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    • 2018
  • Modular multilevel converter (MMC)-based high-voltage direct current (HVDC) presents attractive technical advantages and contributes to enhanced system operation and reduced oscillation damping in dynamic MMC-HVDC systems. We propose an advanced small-signal multi-terminal MMC-HVDC based on dynamic phasors and state space for power system stability analysis to enhance computational accuracy and reduce simulation time. In accordance with active and passive network control strategies for multi-terminal MMC-HVDC, the matchable small-signal stability models containing high harmonics and dynamics of internal variables are conducted, and a related theoretical derivation is carried out. The proposed advanced small-signal model is then compared with electromagnetic-transient and traditional small-signal state-space models by adopting a typical multi-terminal MMC-HVDC network with offshore wind generation. Simulation indicates that the advanced small-signal model can successfully follow the electromechanical transient response with small errors and can predict the damped oscillations. The validity and applicability of the proposed model are effectively confirmed.

A Study on the Optimal Parameter Selection of a Power System Stabilizer and Power Converters for HVDC Linked System (HVDC 연계 시스템의 전력계통 안정화 장치와 전력변환기 적정 파라미터 선정에 관한 연구)

  • 조의상;김경철;최홍규
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.65-72
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    • 2001
  • Power system stabilizer act efficiently to damp the electromechanical oscillations in interconnected power systems. This paper presents an algorithm for the optimal parameter selection of a power system stabilizer in two-area power systems with a series HVDC link. This method is one of the classical techniques by allocating properly pole-zero positions to fit as closely as desired the ideal phase lead between the voltage reference and the generator electrical power and by changing the gain to produce a necessary damping torque over the matched frequency range. Control of HVDC converter and inverter are used a constant current loop. Proper parameters of PI controllers are obtain based on the Root-locus technique in other to have sufficient speed and stability margin to cope with charging reference values and disturbance. The small signal stability arid transient stability studies using the PSS parameters obtained from this method show that a natural oscillation frequency of the studycase system is adequately damped. Also the simulation results using the HVDC converter and inverter parameters obtained from this proposed method show proper current control characteristics. The simulation used in the paper was performed by the Power System Toolbox software program based on MATLAB.

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A Study on the Optimal Parameter Selection of a Power System Stabilizer for HVDC Linked System (HVDC 연계 시스템의 전력계통 안정화 장치의 적정 파라메터 선정에 관한 연구)

  • 김경철;최홍규;최병숙;강태은;고영곤
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.15 no.5
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    • pp.81-89
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    • 2001
  • Power system stabilizer act efficiently to damp the electromechanical oscillations in interconnected power systems. This paper presents an algorithm for the optimal parameter selection of a power system stabilizer in two-area power systems with a series HVDC link. This method is one of the classical techniques by allocating properly pole-zero positions to fit as closely as desired the ideal phase lead between the voltage reference and the generator electrical power and by changing the gain to produce a necessary damping torque over the matched frequency range. The small signal stability and transient stability studies using the PSS parameters obtained from this method show that a natural oscillation frequency of the study case system is adequately damped. The simulation used in the paper was performed by the Power System Toolbox software program based on MATLAB.

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Effects of Wind Generation Uncertainty and Volatility on Power System Small Signal Stability

  • Shi, Li-Bao;Kang, Li;Yao, Liang-Zhong;Qin, Shi-Yao;Wang, Rui-Ming;Zhang, Jin-Ping
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.60-70
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    • 2014
  • This paper discusses the impacts of large scale grid-connected wind farm equipped with permanent magnet synchronous generator (PMSG) on power system small signal stability (SSS) incorporating wind generation uncertainty and volatility. Firstly, a practical simplified PMSG model with rotor-flux-oriented control strategy applied is derived. In modeling PMSG generator side converter, the generator-voltage-oriented control strategy is utilized to implement the decoupled control of active and reactive power output. In modeling PMSG grid side converter, the grid-voltage-oriented control strategy is applied to realize the control of DC link voltage and the reactive power regulation. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based is carried out on the IEEE 16-generator-68-bus test system as benchmark to study the impacts of wind generation uncertainty and volatility on small signal stability. Finally, some preliminary conclusions and comments are given.