• KEPCO Journal on Electric Power and Energy
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• 제6권4호
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• pp.419-425
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• 2020

DC distribution system has been evaluated as an excellent one in comparison with existing AC distribution network because it needs fewer power conversion stages and the full capacity of the equipment can be used without consideration for power factor. Recently, research and development on the implementation of DC distribution networks have been progressed globally based on the rapid advancement in power-electronics technology, and the technological developments from the viewpoint of infrastructure are also in progress. However, to configure a distribution network which is a distribution line for DC, more accurate and rapid introduction of analysis technology is needed for the monitoring, control and operation of the system, which ensure the system run flexible and efficiently. However, in case of a bipolar DC distribution network, there are two buses acting as slack buses, so the Jacobian matrix cannot be configured. Without solving this problem, DC distribution network cannot be operated when the network is unbalanced. Therefore, this paper presented a comprehensive method of analysis with consideration of operating elements which are directly connected between neutral electric potential caused by the unbalanced of load in DC distribution network with bipolar structure.

• 한국전자파학회논문지
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• 제16권6호
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• pp.603-614
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• 2005

본 논문에서는 CQPSK(Compatible QPSK) 변조 방식을 이용하여 APCO P25 규격을 만족하는 직접 변환 방식 디지털 초협대역 무전기를 구현하였다. 초협대역화에 따른 DC-offset 및 AC-coupling 영향, CQPSK 변조 방식에 대한 전력 증폭기의 비선형 특성을 최소화하기 위한 무전기 RF 트랜시버 설계 및 제작 방안을 제시하였다. 직접 변환 방식 RE 트랜시버 및 DSP 모듈과의 연동 시험 결과 송신기의 경우 36.8 dBm의 PEP에서 FCC 방사 마스크 규격을 만족하였다. PWM 제어 신호에 의한 수신기 AGC 동작 범위는 40 dB 범위에서 선형적으로 동작 하였고, 수신 감도 레벨(-116 dBm)에서도 양호한 음성 통화가 가능하였다. 또한 입력 SNR에 따른 BER 성능 및 주파수 오프셋 변화에 대한 BER 성능 측정 결과 무전기 성능 요구 규격을 만족함을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.13-14
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• 2011

The power conversion converter for driving the wireless power transfer system is can be into the two part of the DC power conversion rectifier and the high frequency dc-ac power conversion inverter. In this paper, The operating characteristics of the Class-${\Phi}_2$ resonant inverter have been investigated through by simulation and by experiment. It can be switched at a high frequency without the switching losses and the harmonics are reduced effectively due to the input LC filter. Its switching frequency is 1MHz and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output peak voltage is 170V. The resonant inverter module operated at the commercial power source of 220V was built. And also the electromagnetic coupled resonance coils were designed for wireless power transfer with a 1MHz operating frequency. As a experimental result, the wireless power transmission was confirmed and it is varified the validity of the experiment.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.822-828
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• 2018

AC-DC conversion is a necessary for the systems that require DC source. This conversion has been done via rectifiers based on controlled or uncontrolled semiconductor switches. Advances in the power electronics and microprocessor technologies allowed the use of Pulse Width Modulation (PWM) rectifiers. In this paper, dq-axis current and DC link voltage of three-phase PWM rectifier are controlled by using type-2 fuzzy neural network (T2FNN) controller. For this aim, a simulation model is built by MATLAB/Simulink software. The model is tested under three different operating conditions. The parameters of T2FNN is updated online by using back-propagation algorithm. The results obtained from both T2FNN and Proportional + Integral + Derivate (PID) controller are given for three operating conditions. The results show that three-phase PWM rectifier using T2FNN provides a superior performance under all operating conditions when compared with PID controller.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.1207-1208
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• 2006

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage 380[VDC] and a PWM inverter with LC filter to convent the DC voltage to single-phase 220[VAC]. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%] is obtained over the wide output voltage regulation ranges and load variations.

• 한국인터넷방송통신학회논문지
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• 제23권2호
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• pp.149-155
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• 2023

태양광 발전은 신재생에너지 중 가장 친숙한 발전시설로 약 10여 년 전부터 보급이 확대되기 시작해 현재 시점에서는 시스템의 유지보수관리에 대한 해결 및 기술에 관한 관심이 높아지고 있다. 특히 태양광 발전시스템의 이상 유무 및 부품 교체시기 그리고 시스템의 종합효율을 최대화할 수 있는 대책이 필요하다. 태양광발전시스템의 한 요소인 PV 인버터는 전력용 스위칭 소자에 의존하는 전력변환 시스템으로 DC/DC 컨버터 및 DC-AC 인버터 구성에 따른 직류(DC-Link) 커패시터가 사용된다. 이러한 직류 커패시터 역시 장시간 사용에 따른 노후 및 열화로 인해 PV 인버터의 발전량 감소와 전력손실 그리고 고조파(THD, 교류출력전류 종합왜형률) 증가로 신재생에너지 설비를 통한 계통 안전성(Safety)에 영향을 미치는 요인으로 분석할 수 있다. 따라서 본 논문에서는 태양광발전시스템에서 현재 운영 중인 직류 커패시터 용량 상태에 따른 PV 인버터 동작 특성을 고찰함과 동시에 신재생에너지 설비의 안전성 및 신뢰성을 확보할 수 있도록 연구내용을 제안하였다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.752-759
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• 2013

This paper proposes a method for fault diagnosis and fault-tolerant control of DC-link voltage sensor for two-stage three-phase grid-connected PV inverters. Generally, the front-end DC-DC boost converter tracks the maximum power point (MPP) of PV array and the rear-end DC-AC inverter is used to generate a sinusoidal output current and keep the DC-link voltage constant. In this system, a sensor is essential for power conversion. A sensor fault is detected when there is an error between the sensed and estimated values, which are obtained from a DC-link voltage sensorless algorithm. Fault-tolerant control is achieved by using the estimated values. A deadbeat current controller is used to meet the dynamic characteristic of the proposed algorithm. The proposed algorithm is validated by simulation and experiment results.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1992년도 추계학술발표회논문집
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• pp.47-50
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• 1992

In this paper, the authors propose a so-called new zero voltage switching circuit topology arts an improved PWM strategy. In order to minimize voltage stress in dc-ac high switching frequency power conversion, the proposal circuit is used as interface between DC sully and the PWM inverter. The new ZVS circuit provide PWM inverter with a short zero voltage period in the dc 1ink just before inverter switches operate. By using the proposed modulating signal (transformational sinewave) art carrier sinal (sawtooth ware), the amplitude of the fundamental component is increased about 15 percent more than that of a conventional sinusoidal modulating signal and triangular carrier signal, the switching tosses is reduced. Some simulative results on computer are included to confirm the validity of the analytical results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.529-530
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• 2011

본 논문에서는 대용량 및 장거리 송전을 위한 풍력발전용 MVDC 전력변환 시스템을 제안한다. 이 시스템은 컨버터, 인버터, DC Link, LC필터로 구성되어 있으며 풍력 발전기에서 발생되는 전압을 컨버터가 동작하여 DC 2000V로 제어한다. 변환된 DC Link의 전압은 인버터에서 AC 380V로 변환하여 계통에 연계된다. 제안된 방식의 타당성 검증하기 위해 500[kW]급 풍력발전용 인버터를 제작 및 실험하였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권4호
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• pp.337-342
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• 2005

Direct torque control (DTC) was originally developed for induction machine drives, and, more recently has been applied to permanent magnet brushless AC (BLAC) drives. In this paper, the performance of DTC controlled brushless DC (BLDC) drives is compared with that of PWM current controlled BLDC drives, both with and without current shaping. Both simulation and experimental results are presented, as well as the analysis of the resulting torque waveforms. It is shown that, in addition to exhibiting a fast torque response, a DTC controlled BLDC drive has a significantly lower low-frequency torque ripple than the PWM current controlled BLDC drive without current shaping, and that it is easier to implement than PWM current control with current shaping.