• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.146-151
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• 2005

This paper describes a new voltage disturbance generator for the performance test of a 1-phase UPS(Uninterruptible Power Supply). The proposed scheme has the ability of voltage sag, swell, and outage generation. The structure of the proposed generator is simple and cost-effective. The voltage disturbance can be generated with easy control system. The circuit operation and characteristics of the proposed converter are described and the usefulness of the converter is verified through computer simulations and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.435-441
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• 2003

Dynamic Voltage Restorers (DVR)s are known as the best effective and economic means to compensate for voltage sags and swells. This paper proposes a novel method to generate reference voltages synchronized with the grid whether the line voltages are distorted by a fault or not. The proposed reference wave generator (RWG) looks for the original wave forms from the corrupted line voltages and synthesizes the expected positive sequence reference waves for DVRs. There is no transient problem on the generated reference waves when the line voltages are distorted by the fault.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.331-332
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• 2016

본 논문에서는 PWM 슬루율을 제한하기 위한 LC 필터 설계를 제안한다. 기존의 연구에서는 PWM 입력전압과 필터링된 출력 전압에 대한 주파수 분석을 통해 출력단에 나타나는 슬루율을 제한하였다. 하지만 이러한 분석은 순시 출력 슬루율을 정량적으로 분석하기 어렵다. 본 논문에서는 LC필터의 출력 슬루율을 시간 영역에서 분석하고, 이를 제한하는 LC 필터의 정량적인 설계법을 제시한다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.235-236
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• 2016

본 논문에서는 400Hz 항공기용 3상 4선식 인버터의 전압 제어에 대해 연구하였다. 시스템에서 불평형이 발생하면 중성선 전류가 증가하며 이에 따라 출력전압 불균형 및 왜곡 증가 등 시스템에 심각한 문제를 발생시킨다. 전압의 크기를 제어해주는 RMS 제어의 경우 불평형 발생 시 전압의 크기는 정상적으로 제어가 가능하지만, THD가 상승하여 전력의 품질이 저하될 수 있다. 다른 제어 방식인 비례 공진(PR) 제어는 순시적으로 제어를 함으로써 전압의 크기뿐만 아니라 위상차 및 THD 감소 등의 향상된 전력 품질을 기대할 수 있다. 두 제어방법의 비교는 시뮬레이션 및 실험을 통해 수행하였으며, 두 제어방법 불평형 발생 시 모두 전압의 크기 오차가 3% 이하로 정상적으로 제어하는 것을 확인하였고, THD는 RMS 제어에 비하여 PR 제어의 결과가 2% 감소하는 것을 확인하였다.

• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.56-59
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• 2010

태양광과 풍력과 같은 분산전원이 배전계통에 연계되어 운용되는 경우, 수용가의 규정전압인 220${\pm}$6%(207[V]~233[V])를 벗어나는 현상이 발생할 수 있다. 본 논문에서는 태양광이 연계되는 위치에 따라 변동하는 선로임피던스(R${\pm}$jX)에 의하여 발생하는 순시 전압상승 및 전압강하에 의한 전력품질[과전압/저전압] 저하 현상을 LabVIEW S/W를 이용하여 확인하였으며, 이에 따른 문제점을 분석하고 그 해결책을 제시하였다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.488-489
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• 2008

Based on the fact that renewable energies such as photovoltaic, wind power, etc. are increasingly used in distribution systems recently which affects overvoltage, this paper implements an unified power flow controller(UPFC) to compensate voltage swell. The implemented scheme employs an ac chopper and a low-pass filter along with a series transformer. The ac chopper converts the amplitude of the voltage down to the nominal value. The low pass filter makes the rough waveform of the output voltage of the ac chopper due to switching smoothly by eliminating harmonics. To verify the effectiveness of the implemented UPFC, the results by Electro-Magnetic Transients Program(EMTP) are presented for various overvoltage cases.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.66-68
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• 2008

본 논문은, 전력계통 내의 순시 파형으로부터 전력품질 자동진단을 위한 인공지능형 단상전력품질 진단기를 제안한다. 진단하는 전력품질은 전압강하(Sag), 전압상승(Swell), 과도현상(Transient) 및 전고조파함유율(THD) 이다. 인공지능 구현을 위해서 인공신경망 이론을 이용하였으며, 시뮬레이션 및 TI DSP 320C6713 사용하여 하드웨어를 구현하였다. 인공신경망의 학습을 위하여, 00변전소에서 일년(2007년)동안 측정한 데이터 중에서 Sag, Swell, Transient 특성이 명확히 관측된 150주기의 파형과 정상상태의 50주기 파형으로 구성된 총 200주기의 데이터를 사용하였다. 측정된 파형을 1/60[sec.]마다 256번 샘플링하여, FFT 및 웨이블렛 변환을 시행하여 얻어진 값을 인공신경망 학습에 사용하였다. 상용프로그램 PSIM을 이용하여 인공신경망 학습을 시뮬레이션하였으며, DSP 프로세서를 이용하여 하드웨어로 구현하여 검증하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.144-155
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• 2013

This paper presents a low-cost remote power-quality-failure monitoring system (RPMS) using Android App and TI MCU (micro-controller unit), which is appliable to a micro-grid. The designed RPMS testbed consists of smart nodes, a server, and Android APPs. Especially, the C2000-series MCU-based RPMS smart node that is low-cost compared to existing monitoring systems has both a signal processing function for power signal processing and a data transmission function for power-quality monitoring data transmission. The signal processing function implements both a wavelet-based power failure detection algorithm including sag, swell, and interruption, and a FFT-based power failure detection algorithm including harmonics such that reliable and real-time power quality monitoring is guaranteed. The data transmission function implements a low-complexity RPMS transmission protocol and defines a simple data format (msg_Diag) for power monitoring message transmission. We may watch the monitoring data in real time both at a server and Android phone Apps connected to the WiFi network (or WAN). We use RS-232 (or Bluetooth) as the wired (or wireless) communication media between a server and nodes. We program the RPMS power-quality-failure monitoring algorithm using C language in the CCS (Code Composer Studio) 3.3 environment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.10
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• pp.8-17
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• 2008

This paper presents a stable lighting method for HID lamp for ship from initial discharging current limit with discharging voltage control. The output voltage of the proposed control scheme is boosted for ignition, and the charging voltage is decreased by the resistor discharging. The proposed controller fires the initial discharge at the designed discharging voltage to limit the discharge current. After the discharging, constant current controller is used for brightness in steady state. The proposed control scheme can limit the initial discharge current using the starting point control without a complex voltage controller. so it can improve the life-time of HID lamp and get a stable discharge from restricted the initial discharge current. In order to improve the protection of the system, a simple instantaneous error detecting circuit for open state and short state of HID lamp is used. The proposed error detecting of HID lamp can protect the power system of lamp control. The effectiveness of the proposed controller is verified from the experiments of practical 2.5[kW] HID search light for ship.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.314-323
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• 2016

Overhead line voltage of DC railway traction substations has rising or falling characteristics depending on the acceleration and regenerative braking of the subway train loads. The suppression of this irregular fluctuation of the line voltage gives rise to improved energy efficiency of both the railway substation and the trains. This paper presents parameter estimation schemes using the RC circuit model for an overhead line voltage at a 1500V DC electric railway traction substation. A linear artificial neural network with a back-propagation learning algorithm was trained using the measurement data for an overhead line voltage and four feeder currents. The least square estimation method was configured to implement batch processing of these measurement data. These estimation results have been presented and performance analysis has been achieved through raw data simulation.