• 전력전자학회논문지
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• 제20권5호
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• pp.389-394
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• 2015

This paper proposes a series-connected power conversion system that integrates a photovoltaic power conditioner and a charge-balancing circuit. In conventional methods, a photovoltaic power conditioner and a cell-balancing circuit are needed for photovoltaic systems with energy storage devices, which results in a complex configuration and high cost. To overcome these problems, a series-connected DC-DC power conditioning system that integrates a photovoltaic power conditioner with a charge-balancing circuit is proposed. During the generation, the system operates as power conditioner only, whereas it operates as a cell balancing circuit during the rest time. For the analysis, the operating principle of the circuit and the controller design are done by PSIM simulation. For verification, a hardware prototype with 48-W photovoltaic modules has been implemented. Results verified that the modularized photovoltaic power conversion system with a series-connected storage successfully works with the proposed method.

• Journal of Power Electronics
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• 제19권3호
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• pp.803-814
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• 2019

This paper proposes a three-phase current balancing strategy in a power transmission system employing distributed static series compensators (DSSCs). With the proposed variable quadrature voltage injection method, the DSSC emulates either an inductive or a capacitive impedance into the transmission line, and the magnitudes of the phase currents are balanced. Hence, the phase imbalances in the power transmission system are significantly reduced. As a result, the power transfer capability of the transmission lines can be improved. The operational principle of the DSSCs, the hardware structure and the control algorithm are described in detail. Finally, the theoretical analyses and the proposed strategy are experimentally verified through a scaled down transmission system with DSSC prototypes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.890-892
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• 1996

This paper presents a method for optimal placement of series condenser in order to improve the power system transient stability using genetic algorithms(GAs). In applying GAs, this approach utilizes two kinds of strings, one is coded by a binary finite-length for the selection of lines to install series condenser, the other is coded by a real value for the determination of injected condenser capacitance. For the formulation. this paper considers multi-objective function which is the critical energy as decelerating energy in power systems and the total injected condenser capacitance. The proposed method is applied to 9-bus, 18-line, 3-machine model system to show its effectiveness in determining the locations to install series condenser and the series condenser capacitance to be injected, simultaneously.

• Journal of information and communication convergence engineering
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• 제21권1호
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• pp.82-89
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• 2023

Various machine-learning models may yield high predictive power for massive time series for time series prediction. However, these models are prone to instability in terms of computational cost because of the high dimensionality of the feature space and nonoptimized hyperparameter settings. Considering the potential risk that model training with a high-dimensional feature set can be time-consuming, we evaluate a feature-importance-based feature selection method to derive a tradeoff between predictive power and computational cost for time series prediction. We used two machine learning techniques for performance evaluation to generate prediction models from a retail sales dataset. First, we ranked the features using impurity- and Local Interpretable Model-agnostic Explanations (LIME) -based feature importance measures in the prediction models. Then, the recursive feature elimination method was applied to eliminate unimportant features sequentially. Consequently, we obtained a subset of features that could lead to reduced model training time while preserving acceptable model performance.

• Journal of Power Electronics
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• 제9권5호
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• pp.691-699
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• 2009

This paper presents the analysis of series active power filter for reactive power compensation, load balancing, harmonic elimination, and neutral current eradication in three-phase four-wire power systems. Generally, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3rd harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts directly influence its compensation characteristics. Hence, the advantage of this control algorithm is the direct extraction of compensation voltage reference without phase transformations and multiplying harmonic current value by gain and the required rating of the series active filter is much smaller than that of a conventional shunt active power filter. In order to show the effectiveness of the proposed control algorithm, experiments have been carried out.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.157-166
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• 2006

In order to model blending surfaces with curvature continuity, in this paper we apply sixth order partial differential equations (PDEs), which are solved with a composite power series based method. The proposed composite power series based approach meets boundary conditions exactly, minimises the errors of the PDEs, and creates almost as accurate blending surfaces as those from the closed form solution that is the most accurate but achievable only for some simple blending problems. Since only a few unknown constants are involved, the proposed method is comparable with the closed form solution in terms of computational efficiency. Moreover, it can be used to construct 3- or 4-sided patches through the satisfaction of continuities along all edges of the patches. Therefore, the developed method is simpler and more efficient than numerical methods, more powerful than the analytical methods, and can be implemented into an effective tool for the generation and manipulation of complex free-form surfaces.

• Journal of information and communication convergence engineering
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• 제9권4호
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• pp.369-374
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• 2011

Generally the neural network and the Fuzzy compensative algorithms are applied to forecast the time series for power demand with the characteristics of a nonlinear dynamic system, but, relatively, they have a few prediction errors. They also make long term forecasts difficult because of sensitivity to the initial conditions. In this paper, we evaluate the chaotic characteristic of electrical power demand with qualitative and quantitative analysis methods and perform a forecast simulation of electrical power demand in regular sequence, attractor reconstruction and a time series forecast for multi dimension using Lyapunov Exponent (L.E.) quantitatively. We compare simulated results with previous methods and verify that the present method is more practical and effective than the previous methods. We also obtain the hourly predictability of time series for power demand using the L.E. and evaluate its accuracy.

• 전력전자학회논문지
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• 제11권1호
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• pp.56-64
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• 2006

지난 수년 동안 고집적 변압기를 이용한 고집적 전원장치가 연구되어 왔다 이러한 고집적 전원장치를 구현하기 위해 직렬 공진컨버터가 꾸준히 적용되어 왔으며, 본 논문에서는 고집적 LLCT 평면 변압기를 적용한 Half-bridge 직렬 공진컨버터에 대해 서술하였다. 뿐만 아니라 고집적 LLCT 평면 변압기 구조에 대해 FEMM을 이용하여 해석하였고, 이론적인 해석과 300W급 시제품을 제작하여 실험 결과를 증명하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.196-199
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• 2001

This paper deals with current harmonics and unbalanced source voltages compensation using combined filter system. Filter system consists of a series active filter and parallel passive filters. Passive filters were a traditional method to compensate current harmonics, so those were installed in power system widely. The active filter can be a substitution to improve filtering characteristics and complement drawbacks of the passive filter. The combined system of the active power filter and passive filter can has a better compensation performances and economical goods. The series type active power filter injects compensation voltage into power system by transformers. It's compensation principle is able to applicate for voltage compensation. A new control algorithm for series active filter to compensate current harmonics and unbalanced source voltages is proposed. In the proposed algorithm, a compensation voltage for harmonic reduction is calculated directly by instantaneous reactive power theory, and a compensation voltage for unbalanced source voltage is calculated in based on a synchronous reference frame. By experiments, we show validity of proposed compensation method.

• Journal of applied mathematics & informatics
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• 제41권1호
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• pp.1-9
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• 2023

In the present paper, two theorems on absolute matrix summability of infinite series are generalized for the 𝜑 - |A, p_n|_k summability method using quasi 𝛽-power increasing sequences instead of almost increasing sequences.