• Title/Summary/Keyword: Torque oscillation

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Research of the Mechanism of Low Frequency Oscillation Based on Dynamic Damping Effect

  • Liu, Wenying;Ge, Rundong;Zhu, Dandan;Wang, Weizhou;Zheng, Wei;Liu, Fuchao
    • Journal of Electrical Engineering and Technology
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    • v.10 no.4
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    • pp.1518-1526
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    • 2015
  • For now, there are some low frequency oscillations in the power system which feature low frequency oscillation with positive damping and cannot be explained by traditional low frequency oscillation mechanisms. Concerning this issue, the dynamic damping effect is put forward on the basis of the power-angle curve and the study of damping torque in this article. That is, in the process of oscillation, damping will dynamically change and will be less than that of the stable operating point especially when the angle of the stable operating point and the oscillation amplitude are large. In a situation with weak damping, the damping may turn negative when the oscillation amplitude increases to a certain extent, which may result in an amplitude-increasing oscillation. Finally, the simulation of the two-machine two-area system verifies the arguments in this paper which may provide new ideas for the analysis and control of some unclear low frequency phenomena.

Instantaneous torque control of induction motor with line-to-line voltage modulation on the variable load. (가변 부하시 선간전압 변조방식을 이용한 유도전동기의 순시 Torque 제어)

  • No, J.H.;Woo, J.I.;Lee, H.W.
    • Proceedings of the KIEE Conference
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    • 1991.07a
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    • pp.645-648
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    • 1991
  • In conventional sinusoidal wave PWM control, torque oscillation is a problem on account of harmonic component. This paper deals with the choice of line-to-line voltage modulation method, which is effective in using DC(direct current) source voltage and in controlling harmonic oscillation, and the pattern to reduce swiching loss through 1/3 pause of switching interral. So, this paper deals with valid realization of harmonic component and high torque response on variable load by simulation and experiments to compensate occurring problems when line-to-line modulation are applied to PWM inverter.

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Drive-train Jerk Reduction Control for Parallel Hybrid Electric Vehicles (병렬형 하이브리드 전기자동차 구동계의 Jerk 저감 제어)

  • Park, Joon-Young;Sim, Hyun-Sung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.1
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    • pp.17-24
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    • 2011
  • TMED(Transmission Mounted Electric Device) parallel hybrid configuration can realize EV(Electric Vehicle) mode by disengaging the clutch between an engine and a transmission-mounted motor to improve efficiencies of low load driving and regenerative braking. In the EV mode, however, jerk can be induced since there are insufficient damping elements in the drive-train. Though the jerk gives demoralizing influence upon driving comport, adding a physical damper is not applicable due to constraints of the layout. This study suggests the jerk reduction control, composed of active damping method and torque profiling method, to suppress the jerk without hardware modification. The former method creates a virtual damper by generating absorbing torque in the opposite direction of the oscillation. The latter method reduces impulse on the mated gear teeth of the drive-train by limiting the gradient of traction torque when the direction of the torque is reversed. To validate the effectiveness of the suggested strategy, a series of vehicle tests are carried out and it is observed that the amplitude of the oscillation can be reduced by up to 83%.

An Improved Control Method for a DFIG in a Wind Turbine under an Unbalanced Grid Voltage Condition

  • Lee, Sol-Bin;Lee, Kyo-Beum;Lee, Dong-Choon;Kim, Jang-Mok
    • Journal of Electrical Engineering and Technology
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    • v.5 no.4
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    • pp.614-622
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    • 2010
  • This paper presents a control method, which reduces the pulsating torque and DC voltage problems of a doubly fed induction generator (DFIG)-based wind turbine system. To reduce the torque and power ripple, a current control scheme consisting of a proportional integral (PI) controller is presented in a positive synchronously rotating reference frame, which is capable of providing precise current control for a rotor-side converter with separated positive and negative components. The power theory can reduce the oscillation of the DC-link voltage in the grid-side converter. In this paper, the generator model is examined, and simulation results are obtained with a 3 kW DFIG-based wind turbine system to verify the proposed control strategy.

A Basic Study for Tuning Power System Stabilizer Part I : Analyzing the Torque Characteristics of Power System Corresponding to Operating Conditions (PSS 튜닝을 위한 기본 연구 Part I : 계통 운전조건에 대한 토오크 특성분석)

  • 김동준;문영환;김태균
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.9
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    • pp.1064-1072
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    • 1999
  • The basic concepts, which are related to the PSS tuning conditions and performance conditions for the safe of determination of PSS gain and compensation of phasor lagging, are thoroughly investigated in this first part. The performance conditions, where the power system has the lowest inherent damping torque and PSS should provide maximum damping torque, are examined by analysing synchronizing torque and damping torque supplied by the voltage control loop at the oscillation frequency. PSS tuning conditions are also investigated by observing the phasor lagging and the gain, resulted from power system-generator-excitation system depending on operating conditions, such as generator active power, reactive power, transmission impedance and AVR gain. The basic concepts developed in this PartImake it possible to lay foundation for the discussion of PSS tuning in Part II.

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Tuning-free Anti-windup Strategy for High Performance Induction Machine Drives (고성능 유도전동기 구동을 위한 자동 튜닝 Anti-windup 기법)

  • Seok Jul-Ki;Bae Sang-Gyu;Lee Dong-Choon
    • Proceedings of the KIPE Conference
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    • 2004.07a
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    • pp.312-315
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    • 2004
  • This paper presents a tuning-free conditional integration anti-windup strategy for induction machine with Proportional-Integral (PI) type speed controller. The on/off condition of integral action is determined by the frequency domain analysis of machine torque command without a prior knowledge of set-point changes. There are no tuning parameters to be selected by users for anti-windup scheme. In addition, the dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time even in the change of operating conditions. This algorithm is useful in many high performance induction machine applications not to allow the oscillation and overshoot of speed/torque responses. The main idea can be extended to general applications such as chemical processes and industrial robots.

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Characteristics Analysis of Induction Motor by Operation of Non-lineal Loads (비선형 부하의 운전시 유도전동기의 특성 해석)

  • Kim, Jong-Gyeum;Park, Young-Jeen;Lee, Eun-Woong
    • Proceedings of the KIEE Conference
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    • 2006.10b
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    • pp.147-153
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    • 2006
  • Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

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Suppression Control of the Drivetrain-Oscillations of an Electric Vehicle Using Taguchi Method (다구찌 방법을 이용한 전기자동차 구동계의 진동 억제 제어)

  • Kim, Ho-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.5
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    • pp.463-468
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    • 2009
  • Torsional oscillations of the drivetrain in electric vehicles are generated under rapid driving conditions. These lead to an uncomfortable jerking of the vehicle and an increased stress of the mechanical components. To suppress torsional oscillations, the low pass and notch filters between the torque command from the acceleration pedal and electric motor input torque are suggested. The filter parameters are optimized based on Taguchi method with $L_{18}(3^5)$ orthogonal array. The signal to noise (S/N) ratio mainly depends on slew rate of motor input torque, damping ratio and natural frequency of notch filter. With the proposed suppression control scheme, the S/N ratio is shown to be increased by 4.7dB and the torque overshoot of the drive shaft is reduced to 30%.

Assessment of the Influence on Harmonic Torque in Diesel Generating System by using EMTP (EMTP를 이용한 디젤발전시스템 Harmonic Torque의 계통영향 평가)

  • Kim, Soo-Nam;Jung, Moon-Goo;Baek, Byung-San;Kim, Ik-Mo
    • Proceedings of the KIEE Conference
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    • 2003.11a
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    • pp.125-127
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    • 2003
  • This paper presents method of the assessment on the Influence of harmonic torque in diesel generating system by using EMTP(Electromagnetic Transient Program). The objectives is to analysis the influence on power oscillation and voltage fluctuation due to the periodically varying torque developed by the new diesel generator to be installed in existing power system.

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Analysis and Control of Low Frequency Oscillation using TCSC Small Signal Model by Control of Firing Angles (TCSC의 소신호 모형을 이용한 점호각 제어에 의한 저주파 진동 감쇠 효과 해석 및 제어)

  • Kim, Tae-Hyun;Seo, Jang-Cheol;Park, Jong-Keun;Moon, Seung-Ill;Han, Byung-Moon
    • Proceedings of the KIEE Conference
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    • 1995.11a
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    • pp.120-124
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    • 1995
  • TCSC can not only increase power flow but also damp low frequency oscillation by controlling firing angles of thyristors. But, a model considering voltage, current firing angles is not derived. This paper used a small signal model considirng these variables which was derived in paper [1]. TCSC model is combined with swing equation. Being related to rotor angles and firing angles of thyristors, current and synchronizing torque coefficient is reformulated. Because firing angles of thyristors can be controlled only twice within one period, swing equation is transformed to discrete time model. It is shown that low frequency oscillation can be damped by controlling firing angles in one machine infinite bus power system.

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