• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.329-329
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• 2000

In this paper, a spindle system using an electromagnetic exciter is proposed to compensate a spindle disturbance such as unbalance and machining force etc A spindle compliance can be readily varied with a disturbance which is generated by the interact ion between the spindle / workpiece structure and the cutting process dynamics. The varied compliance is one of the major constraints that deteriorates the surface quality of workpiece. This paper suggests a compliance compensation by using the EME in the proposed spindle system. To compensate the varied compliance, firstly a spindle system modeling was conducted by using the bond graph. Then the model is simulated by numerical analysis method and an optimal EME position is determined to compensate a disturbance effectively through simulation, which makes the bearing load to be minimized

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.9 s.102
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• pp.1045-1052
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• 2005

Tn this paper. dual rotor disk configuration with a coreless stator is proposed for the Lorentz force type integrated motor hearing system. An experimental compensation for the effects of high order harmonics is performed using the digital controller of the experimental setup. The runout profile and rotor unbalance are also identified by the extended influence coefficient method. The experimental results confirm that this compensation scheme effectively attenuates the rotor vibration all over the operating range of rotational speed.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.705-707
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• 2000

In this paper, a static synchronous compensator(STATCOM) is proposed in order to compensate both negative-sequence and reactive power. The STATCOM control unit is designed considering the proposed compensation scheme for the unbalanced loads. As a result, the effectiveness of the STATCOM for compensating both negative-sequence and reactive power is verified by computer simulations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1447-1454
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• 2018

In this paper, the design of robust DSC-PLL(Delayed Signal Cancellation Phase Locked Loop) is proposed for coping with frequency variation. This method shows significant performance for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid unbalance and frequency variation. The feedback frequency estimation of DSC-PLL is tracking the drift in the phase by unbalance and frequency variation. The robust DSC PLL is to present the analysis on method and performance under frequency variations. These compensation algorithms can correct for discrepancies of changing the frequency within maximum 193[ms] and improve traditional DSC-PLL. Linear interpolation method is adopted to reduce the discretized errors in the digital implementation of the PLL. For verification of robust characteristic, PLL methods are implemented on FPGA with a discrete fixed point based. The proposed method is validated by both Matlab/Simulink and experimental results based on FPGA(XC7Z030).

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.787-790
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• 2004

In this paper, a novel control scheme compensating for source voltage unbalance and current harmonics and power factor correction in unified active power filter systems combined with shunt passive filters is proposed, where no low/high-pass filter are used in deriving the reference voltage for compensation. Using digital all-pass filters, the phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage. The amplitude of d-axis current in a series filter is controlled as zero for power factor correction. The validity of the proposed control scheme has been verified by experimental results.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.87-91
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• 2003

Most of the loads in industrial power distribution systems are balanced and connected to three wires power systems. However, in the user power distribution systems, most of the loads are single & three phase and unbalanced, generating a large amount of non-characteristic harmonics. With the advent of power electronics and proliferation of non-linear loads in industrial power applications, power harmonics and their effects on power quality are a topic of concern. Harmonics by the unbalance voltage and non-linear loads, cause the increase of machine loss and heating. In order to allow current harmonic compensation, a filter must be installed. This paper describes the performance of passive filter under the voltage unbalance and non-linear load.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.103-105
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• 2004

In this paper, a novel control scheme compensating for source voltage unbalance and current harmonics and power factor simultaneously in unified active power filter systems combined with shunt passive filters is proposed, where no low/high-pass filter are used in deriving the reference voltage for compensation. Using digital all-pass filters, the phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage. The amplitude of d-axis current in a series filter is controlled as zero for power factor correction. The validity of the proposed control scheme has been verified by experimental results.

• Journal of KSNVE
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• v.8 no.5
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• pp.964-973
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• 1998

In this paper we propose a levitation and imbalance compensation controller design methodology of magnetic bearing system. In order to achieve levitation and elimination of unbalance vibartion in some operation speed we use the discrete-time Q-parameterization control. When rotor speed p = 0 there are no rotor unbalance, with frequency equals to the rotational speed. So in order to make levitatiom we choose the Q-parameterization controller free parameter Q such that the controller has poles on the unit circle at z = 1. However, when rotor speed p $\neq$ 0 there exist sinusoidal disturbance forces, with frequency equals to the rotational speed. So in order to achieve asymptotic rejection of these disturbance forces, the Q-parameterization controller free parameter Q is chosen such that the controller has poles on the unit circle at z = $exp^{ipTs}$ for a certain speed of rotation p ( $T_s$ is the sampling period). First, we introduce the experimental setup employed in this research. Second, we give a mathematical model for the magnetic bearing in difference equation form. Third, we explain the proposed discrete-time Q-parameterization controller design methodology. The controller free parameter Q is assumed to be a proper stable transfer function. Fourth, we show that the controller free parameter which satisfies the design objectives can be obtained by simply solving a set of linear equations rather than solving a complicated optimization problem. Finally, several simulation and experimental results are obtained to evaluate the proposed controller. The results obtained show the effectiveness of the proposed controller in eliminating the unbalance vibrations at the design speed of rotation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2206-2214
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• 2011

LDC(Line Drop Compensation) is widely used in controlling ULTC(Under Load Tap Changer) output voltage at distribution substation. However, LDC may experience some difficulties in voltage control due to renewable energy resources and distributed generations. Therefore, more advanced voltage control algorithm is necessary to deal with these problems. In this paper, a modified voltage control algorithm for ULTC and DG is suggested. ULTC is operated with the voltages measured at various points in distribution system and prevents overvoltage and undervoltage in the distribution feeders. Reactive power controller in DG compensates the voltage drop in each distribution feeders. By these algorithms, the voltage unbalance between feeders and voltage limit violation will be reduced and the voltage profile in each feeder will become more flat.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.5
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• pp.249-257
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• 2002

In this paper, a novel control scheme compensating source voltage unbalance and harmonic currents for the combined system of series active and shunt passive power filter is proposed, where no low/high-pass filters are used in deriving the reference voltage for compensation. The phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage set, which is simply obtained by using digital all-pass filters. In order to remove the phase delay in generating the reference voltage for compensation, the reference of 5th and 7th harmonic components is predicted one-sampling ahead. The validity of the proposed scheme has been verified for 3[kVA] proto-type active power filter system.