• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.6
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• pp.274-283
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• 2005

This paper presents a new method to derive energy function based on vector product. Using this method, an energy function to consider transfer conductances and capacitors is derived. Then we recommend a voltage collapse criteria to predict the voltage collapse in power systems by using the energy margin derived by the proposed energy function. This energy function is applied to a 2-bus power system reflecting transfer conductances and capacitors. We show that the energy function derived based on vector product can be applied in order to analyze power system stability and the energy margin can be utilized as a criterion of voltage collapse by simulation for the 2-bus system.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.4
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• pp.310-317
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• 2007

In this paper, the system equation for the balanced two-phase induction motor is derived and the characteristics for speed control is also analyzed in the region of constant torque and constant power. The modified vector control theory is applied to two-phase motor drive system. The speed of two-phase motor drive can be controlled precisely by the modified indirect vector control theory. The modified vector control theory is simpler comparing to the conventional vector control because of the simpler axis transformation. The computer simulations and the experimental results presented to confirm the vector control for two-phase inverter fed two phase induction motor system.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.3
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• pp.274-284
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• 2003

Multi-level converter that is high-capacity electric power conversion system is used widely to electric motor drive system and FATCs(Flexible AC Transmission Systems). H-Bridge converter has been prevalently applied to shunt-type system because it can be easily expanded to the multi-level. In steady states, converter is normally operated in the range of 0.7∼0.8 of modulation Index. Even though zero vectors are not imposed to high modulation index, DC-Link voltage Is constant. It means that converter has another boost vector except for zero vectors among several vectors in 3-level converter. This paper has examined the principle of boost vector and investigated the difference between another boost vector and zero vectors in 3-level converter. In addition, this paper has analysed and compared the charging currents and the capacitor voltages of two topologies. The currents and voltages are related to reference voltage. Therefore, it proposed the calculation method for the voltage ripple and the charging current of each capacitor and compared various DC-Link voltage control methods through the simulation.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.8-13
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• 2008

Because of the robust nonlinear characteristics appearing in today's modern power system, a strong interaction exists between the angle stability and the voltage stability, which were conventionally studied insularly. However, as the power system is a complex unified system, angle instability always happens in conjunction with voltage instability. The authors propose a novel method to analyze this type of stability problem. In the proposed method, the theory of normal forms of vector fields is utilized to treat the auxiliary dynamic system. By use of this method, the interaction between response modes caused by the nonlinearity of the power system can be analyzed. Consequently, the eigenvalue analysis method is extended to cope with performance analysis of the power system with heavy nonlinearity. The effectiveness of the proposed methodology is verified on a 3-bus power system.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.404-406
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• 1996

The objective of this paper is to present a new feature-vector extraction method for the automatic detection and classification of power quality(PQ) disturbances, where FFT, DWT(Discrete Wavelet Transform), and data compression are utilized to extract an appropriate feature vector. In particular, the proposed classifier consists of three parts: i.e., (i) automatic detection of PQ disturbances, where the wavelet transform and signal power estimation method are utilized to detect each disturbance, (ii) feature vector extraction from the detected disturbance, and (iii) automatic classification, where Multi-Layer Perceptron(MLP) is used to classify each disturbance from the corresponding extracted feature vector. To demonstrate the performance and applicability of the proposed classification algorithm, some test results obtained by analyzing 7-class power quality disturbances generated by the EMTP are also provided.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.64-66
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• 2010

In this paper, we propose a temporal diversity scheme based on the vector perturbation for a multiuser multipleinput multiple-output (MIMO) broadcasting system. Our method is inspired by the fact that precoding process of the vector perturbation designed to suppress the multiuser interference causes a reduction of the transmitted signal power. In order to boost up the transmit power, we employ a non-integer based vector perturbation together with temporal transmit diversity. We show from the simulation on 10${\times}$10 multiuser MIMO system that the proposed method outperforms the epetition coded vector perturbation scheme as well as the standard vector perturbation.

• Journal of Power Electronics
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• v.11 no.5
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• pp.688-696
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• 2011

This paper proposes a simple space vector PWM (SVPWM) scheme including overmodulation operation for 3-level NPC (Neutral Point Clamped) Inverters. The proposed scheme features a simple decision and calculation procedure for determining switching times in the overmodulation range by utilizing the duty calculation method used in 2-level inverters and the minimum phase error projection method widely employed in motor drive systems. The proposed scheme does not need to detect the angle of the reference vector or calculate trigonometric functions to determine the magnitude of the voltage vector. The magnitude of the angle of the new reference voltage vector is decided in advance with the help of the Fourier Series Expansion to extend the linearity of the output voltage of 3-level inverters in the overmodulation region. Experimental results demonstrate the validity of the proposed SVPWM scheme including overmodulation operation for 3-level NPC inverters.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.745-750
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• 2007

In this paper, we propose a new gate modification method using the input vector maximizes the number of gates in WLS within the optimum range of the minimum leakage power. We prove that MLV is not always the optimal solution, and that the leakage power and area can decrease when modifying the gates using the input vector for which the number of gates in WLS is maximized within the optimum range of the minimum leakage power for the circuits applying the IVC technique and gate modification method. Using the proposed method, the gate-level description circuit can be converted to the modified circuit which reduces the leakage power by chip designer, and the modified circuit can be applied without any modification in design flow.

• Environmental Engineering Research
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• v.24 no.4
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• pp.559-565
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• 2019

In order to alleviate the environmental pressure caused by production process of thermal power plants, the application of cleaner production is imperative. To estimate the implementation effects of cleaner production in thermal plants and optimize the strategy duly, it is of great significance to take a comprehensive evaluation for sustainable development. In this paper, a hybrid model that integrated the analytic hierarchy process (AHP) with least squares support vector machine (LSSVM) algorithm optimized by grid search (GS) algorithm is proposed. Based on the establishment of the evaluation index system, AHP is employed to pre-process the data and GS is introduced to optimize the parameters in LSSVM, which can avoid the randomness and inaccuracy of parameters' setting. The results demonstrate that the combined model is able to be employed in the comprehensive evaluation of the cleaner production in the thermal power plants.

• Journal of Power Electronics
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• v.15 no.2
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• pp.497-503
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• 2015

This paper analyses the harmonic pollution to power grids caused by several high-power rectifiers, summarizes the requirements for rectifiers in suppressing grid-side current harmonics and optimizes a new-type of current source PWM rectifier with a hybrid switch. The rectifier with a hybrid switch boasts significant current characteristics and cost advantages in the high-power area. To further enhance the working frequency of the current source rectifier with a hybrid switch for suppressing grid-side harmonics and reducing the inductance size, this paper proposes an optimal control strategy based on space vector. It also verifies that the optimal control strategy based on space vector can reduce the total harmonic distortion of the grid-side current of the rectifier with a hybrid switch via circuit simulation and experimental results.