• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.518-522
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• 2001

In recent years, natural energy has attracted growing interest because of environmental concerns. Many studies have been focused on photovoltaic power generation systems because of the ease of use in urban areas. On the conventional system, many photovoltaic modules (PV modules) are connected in series in order to obtain the sufficient DC-bus voltage for generating AC output voltage at the inverter circuit. However, the total generation power on the PV modules sometimes decreases remarkably because of the shadows that partially cover the PV modules. In order to overcome this drawback, an AC module strategy is proposed. On this system, a small power DC-AC utility interactive inverter is mounted on each PV module individually and the inverter operates so as to generate the maximum power from the corresponding PV module. This paper presents a novel flyback-type utility interactive inverter circuit suitable for AC module systems. The feature of the proposed system are, (1) small in volume and light in weight, (2) stable AC current injection, (3) enabling a small DC capacitor. The effectiveness of the proposed system is clarified through the simulation and the experiments.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.549-553
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• 1999

This paper describes a design method of grid-connected photovoltaic power generation systems with three phase inverter. A 3-phase 50kW photovoltaic power generation system including a DC/AC inverter is designed and made in order to investigate the system performance for grid connection. Also the control scheme of a three phase current-controlled PWM inverter is presented by using d-q transformation. The experimental waveforms show that the proposed system has stable behavior with an unit power factor in utility-interactive operation.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.467-474
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• 2000

This paper describes the development of 7he utility vehicle controller using combination system of battery and photovoltaic power for increasing operation time. In order to keep interchangeability, low cost and high performance, a separately excited DC Motor is controlled without velocity and current measurements by $\mu$-processor. For the parallel operation between the solar cell and battery, dc-dc converter is used, which is applied to the maximum power Point tracking(MPPT) and current control algorithm. By the simulation and experimental results of trial product, the vapidity of the proposed system is verified.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.511-515
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• 2003

This paper presents a novel prototype of the utility-interfaced sinusoidal pulse width modulated (SPWM) inverter using the high-frequency flyback transformer fur the small-scale solar photo-voltaic power conditioner (1kW - 4kW). The proposed SPWM power conditioner circuit with a high-frequency link has a function of electrical isolation, which is vital fur solar photovoltaic power conditioner systems with the viewpoint of safety and convenience. The discontinuous conduction mode (DCM) operation of the flyback transformer is also maintained to simplify the topology of the inverter circuit and control scheme. First, the operating principle of the proposed circuit is described far the understanding of the circuit parameters establishment. Then, the digitally constructed SPWM control scheme is presented. The proposed circuit is verified by the computer simulation and the prototype experiment.

• Journal of Power Electronics
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• v.10 no.4
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• pp.428-433
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• 2010

This paper proposes a harmonics reduction technique for the input currents of three phase PWM converters. The quality of the phase angle information on the utility voltage connected to the PWM converters affects their control performance. Under a distorted utility voltage, the extracted phase angle based on the synchronous reference frame PLL method is distorted. This causes large harmonics in the input currents of a PWM converter. In this paper, a harmonics reduction method that makes the input currents in the PWM converter sinusoidal even under distorted utility conditions is proposed. By the proposed method, without additional hardware, the THD (Total Harmonic Distortion) of the input currents can be readily limited to below 5% which is the harmonic current requirements of IEEE std. 519. Its validity is verified by simulations and experimental results.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.48-53
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• 1998

This paper describes on the development of Controller for the Utility Car using Microprocessor. The Utility Car is composed of Controller, separately exited DC motor, battery and potbox. It is easier to for a digitalized controller using microprocessor append new function than an analogized controller. The test driving of controller shows that the Utility Car travels 20 [km] per charge.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.4
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• pp.325-331
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• 1999

In a utility interactive photovoltaic generation system. a PWM inverter is used for the connection between the p photovoltaic arrays and the utility. The dc current becomes pulsated when the conventional inverter system operates i in the continuous current mode and de current pulsation causes the distortion of the accurrent waveform. This paper p presents the reduced pulsation of de input current by operating the inverter with buck-boost chopper in the d discontinuous conduction mode. The dc current which contains harmonic component is analyzed by means of s separating into two terms of a ripple component and a direct component. The constant dc current without p pulsation is supplied from photovoltaic array to the inverter. The proposed inverter system provides a sinusoidal ac c current for domestic loads and the utility line with unity power factor.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.3
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• pp.111-118
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• 2005

Since the residential load is an AC load and the output of solar cell is DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feed-forward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.116-119
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• 2004

The existing monitoring and control systems of utility-pipe conduit (power tunnel, cable tunnel etc) have established communication lines using optical fiber, leaky coaxial cable (LCX), and several kinds of control cable. Due to the properties of the used media, the cost of equipment is considerably high and the maintenance of the system is difficult. Also, the term of carrying out is long so that the extension of the system is in difficulty. Now it is desirable to adopt Power Line Communication (hereinafter, PLC) technology in the monitoring and control systems and use the existing low-voltage power-line for lamplight as communication line. This will lead the reduction of the construction cost and the easy maintenance of the system. In this paper, we research the characteristics of PLC in conduit, design and manufacture the field test system, and analyze the performance of the system by field test. Then, we introduce the reliable monitoring and control system of utility-pipe conduit using PLC.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.344-347
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• 2011

In this paper, we propose the power control problem for cognitive radio networks (CRNs) that maximizes the total utility of the secondary users (SUs). We use the interference temperature constraints to protect the primary users (PUs). The utility functions of SUs can be any increasing functions. We formulate the power control problem as monotonic optimization that can be solved in centralization to achieve the global optimum.