• Journal of Electrical Engineering and Technology
• /
• 제12권5호
• /
• pp.1805-1811
• /
• 2017

Recently, DC systems are considered as efficient electric power systems for renewable energy based clean power generators. This discloses several critical issues that are required to be considered before the installation of the DC systems. First of all, voltage/current switching stress, which is aggravated by large fault current, might damage DC circuit breakers. This problem can be simply solved by applying a superconducting fault current limiter (SFCL) as proposed in this study. It allows a simple use of insulated-gate bipolar transistors (IGBTs) as a DC circuit breaker. To evaluate the proposed resistive type SFCL application to the DC circuit breaker, a DC distribution system is composed of the practical line impedances from the real distribution system in Do-gok area, Korea. Also, to reflect the distributed generation (DG) effects, several DC-to-DC converters are applied. The locations and sizes of the DGs are optimally selected according to the results of previous studies on DG optimization. The performance of the resistive type SFCL applied DC circuit breaker is verified by a time-domain simulation based case study using the power systems computer aided design/electromagnetic transients including DC (PSCAD/ EMTDC(R)).

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 F
• /
• pp.2665-2667
• /
• 1999

This Paper proposes a new toplogy snubber circuit of Full-Bridge DC-DC Converter for reducing conduction losses and snubber circuit heating loss. Using Partial Resonent Soft Switching Method and Clamping, studying on a new snubber circuit for reducing losses that a snubber circuit heating loss in the secondly diode rectification side, a switching losses in the primary side of IGBT inverter and conduction losses in the high frequency insulation transformer. In this paper, we present FB DC-DC converter included a new lossless snubber circuit, and then be analyzed and simulated.

• 한국전자통신학회논문지
• /
• 제15권5호
• /
• pp.923-930
• /
• 2020

현대 사회에서 다양한 전기기기들의 시스템 회로를 동작시키기 위해서는 여러 직류 전원이 필요하다. 회로의 정상적인 동작을 위해 안정된 직류의 공급이 필수적으로 요구되고 이를 위한 컨버터의 중요성은 매우 크다고 할 수 있다. 본 연구는 부하 변동에 상관없이 출력전압의 안정적인 공급을 유지할 수 있도록 승압형 DC-DC 컨버터인 KY 컨버터에 3-극점 2-영점 전압 제어기를 적용한 PWM DC-DC 컨버터 회로를 제안하였다. 제안된 컨버터 회로의 정상 동작 특성을 입증하기 위해 기존의 컨버터 회로와 비교하여 PSIM 시뮬레이션 프로그램과 PCB 기판에서의 회로 동작 실험을 수행하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2015년도 제46회 하계학술대회
• /
• pp.396-397
• /
• 2015

With the increasing utilization of high-voltage, direct current (HVDC) transmissions in modern power systems, the DC grid is becoming a hot topic in academic and practical systems. In the DC grid, one of the urgent problems is the fast clearance of the DC fault in the DC network. One preferred method is to isolate the faulty point from the DC network in a short time. The DC circuit breaker is to interrupt the overcurrent after DC faults occur. In this paper, a self-excited resonant DC circuit breaker is an easy and cheap equipment to interrupt the DC fault current. The Mayr's arc model is utilized to simulate the self-excited DC circuit breaker in a DC test system in PSCAD/EMTDC.

• 전자공학회논문지SC
• /
• 제40권6호
• /
• pp.16-23
• /
• 2003

본 논문에서 보청기를 위한 개별 BJT 소자의 효과적인 바이어스 회로를 제안한다. 보청기에 널리 사용되는 컬렉터 귀환 바이어스 회로는 부귀환 저항을 가지고 있다. 이 저항은 AC와 DC에 동시에 영향을 줌으로서 DC 바이어스 점의 변화 없이 증폭기의 이득을 변화시키기 어렵다. 또한 기존회로는 보청기의 이득이 높을 경우 전원 잡음의 정귀환으로 발진할 수 있는 단점이 있다. 제안된 회로는 컬렉터 귀환 바이어스회로에 베이스와 전원 사이에 컬렉터 저항보다 β배 더 큰 저항을 추가하여 기존회로의 두 가지 단점을 줄일 수 있다. 제안된 회로에서 DC 바이어스 점의 변화 없이 증폭기의 이득을 변경 할 수 있고 모의실험에서 기존회로보다 전원 잡음 이득을 18.5%정도 감소시킬 수 있다.

• 전기학회논문지
• /
• 제68권1호
• /
• pp.215-219
• /
• 2019

Development of DC interruption technology is being studied actively for enhanced DC grid reliability and stability. In this study, coil type superconductor DC circuit breaker was proposed as DC interruption. It is integration technology that combined current-limiting technique using superconductor and cut-off technique using mechanical DC circuit breaker. Superconductor was applied to the coil type. In simulation, Mayr arc model was applied to realize the arc characteristic in the mechanical DC circuit breaker. PSCAD/EMTDC had used to model and perform the simulation. To find out the protection range of coil type superconductor DCCB, the working operation have analyzed based on the rated voltage of DCCB. The results confirmed that, according to apply the limiting device, the protection range was increased in twice. Therefore, the probability of failure of interruption has lowered significantly.

• 한국초전도ㆍ저온공학회논문지
• /
• 제20권4호
• /
• pp.55-59
• /
• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

• 한국전자통신학회논문지
• /
• 제18권4호
• /
• pp.617-624
• /
• 2023

최근, 전자 제품의 소형화와 저소비전력화 및 향상된 효율과 역률개선이 큰 관심 사항이 되고 있다. 본 논문에서는 PWM 제어기반의 AC-DC 컨버터를 설계, 제작하였다. AC-DC 컨버터는 하나의 정류회로와 하나의 출력전압 제어 회로가 직렬로 연결되는 구조로 설계하였으며, 정류회로는 다이오드 기반 단상 전파전류 회로, 출력전압 제어 회로는 PWM 제어기반의 DC-DC 변환 회로를 적용하였다. PWM 제어를 위한 주 제어장치로 아두이노를 이용하였으며, LCD를 출력 단에 구성하여 제어 결과를 확인할 수 있도록 하였다. 시험회로를 통한 반복 실험들을 통해서 오실로스코프와 LCD에 디스플레이 되는 출력전압과 목표 출력전압의 오차를 확인하였으며, 오실로스코프 측정값을 기준으로 약 5%의 오차율을 보임으로써 제안된 설계 방법론의 유효성을 확인할 수 있었다.

• 전기학회논문지
• /
• 제65권12호
• /
• pp.2109-2112
• /
• 2016

The rate of rise of the fault current in DC grids is very high compared to AC grids because of the low line impedance of DC lines. In AC grids the arc of the circuit breaker under current interruption is extinguished by the zero current crossing which is provided naturally by the system. In DC grids the zero current crossing must be provided by the circuit breaker itself. Unlike AC girds, the magnetic energy of DC grids is stored in the system inductance. The DC circuit breaker must dissipate the stored energy. In addition the DC breaker must withstand the residual overvoltage after the current interruption. The main contents of this paper are to ${\cdot}$ Explain the theoretical background for the design of DC circuit breaker. ${\cdot}$ Develop the simulation model in PSIM of the real scaled DC circuit breaker for 1,800V DC railway. ${\cdot}$ Suggest design guidelines for the DC circuit breaker based on the experimental work, simulations and design process.

• 전기전자학회논문지
• /
• 제13권2호
• /
• pp.248-252
• /
• 2009

In this paper, analysis of a noise factor and an effective power strategy for the OLED dc-dc converter are described. One of the main reasons that one may not design the OLED power for dc-dc converter is that OLED's panel noise is composed of FFN(Frame Frequency Noise) and LFN(Line Frequency Noise). Into the bargain, FFN is caused by both the dc-dc (circuit) and driving circuit. It is hard to get rid of FFN, baeause FFN has very little results value for our ears. LFN is adjusted by analog compensation value. Actually, that is more important problem than FFN. It is known that voltage divider for OLED's mode variation is not good for compact power design. In the end, a circuit design for understanding OLED's noise and a novel muti-channel dc-dc converter were presented.