• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.411-414
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• 2011

본 논문에서는 DPSS 기능을 갖는 3중 모드 DC-DC buck 변환기를 설계하였다. 설계된 buck 변환기는 부하 전류가 큰 경우(80mA~500mA)에는 PWM(Pulse Width Modulation) 제어 방식을 사용하고, 부하 전류가 작은 경우(1mA~80mA)에는 PFM(Pulse Frequency Modulation) 제어 방식을 사용하며, 부하 전류가 1mA 이하인 대기모드(sleep-mode)에서는 LDO(Low Drop Out)를 사용한다. 또한, PFM 제어 방식에서 부하 전류가 작은 경우 효율을 증가시키기 위해 DPSS(Dynamic Partial Shutdown Strategy) 기법을 사용하였다. 그 결과 넓은 부하 전류 범위에서 높은 효율을 얻을 수 있다. 제안된 벅 변환기는 CMOS 0.18um 공정을 이용하여 설계되었다. 3.3V의 입력전압을 받아 2.5V의 출력전압으로 강압시키며, 최대 부하전류는 500mA이고, 스위칭 주파수는 1MHz이다. 최대효율은 97.03 %, 칩 크기는 PAD를 포함하여 $1465um{\times}895um$이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1141-1142
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• 2011

An electrical vehicle (EV) is a huge issue in the automotive industry. The EV have many electrical units: electric motors, batteries, converters, ets. The DC power distribution system (PDS) is essential for the EV. The DC PDS offers many advantages. However, multiple loads in the DC PDS may affect the severe instability on the DC bus voltage. Therefore, a voltage bus conditioner (VBC) may use the DC PDS. The VBC is used to mitigate the voltage transient on the bus. In this paper, sliding mode controller (SMC) is designed for the VBC of DC PDS in the EV. The simulation results by PISM simulation package are presented for validating the proposed control technique.

• Journal of Electrical Engineering and Technology
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• 제6권1호
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• pp.67-75
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• 2011

The development of electric vehicle power electronics system control, composed of DC-AC inverters and DC-DC converters, attract much research interest in the modern industry. A DC-AC inverter supplies the high-power motor torques of the propulsion system and utility loads of electric vehicles, whereas a DC-DC converter supplies the conventional low-power and low-voltage loads. However, the need for high-power bidirectional DC-DC converters in future electric vehicles has led to the development of many new topologies of DC-DC converters. The nonlinear control of power converters is an active research area in the field of power electronics. This paper focuses on the use of the fuzzy sliding mode strategy as a control strategy for buck-boost DC-DC converter power supplies in electric vehicles. The proposed fuzzy controller specifies changes in control signals based on the surface and knowledge on surface changes to satisfy the sliding mode stability and attraction conditions. The performance of the proposed fuzzy sliding controller is compared to that of the classical sliding mode controller. The satisfactory simulation results show the efficiency of the proposed control law, which reduces the chattering phenomenon. Moreover, the obtained results prove the robustness of the proposed control law against variations in load resistance and input voltage in the studied converter.

• 전기학회논문지
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• 제60권9호
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• pp.1674-1683
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• 2011

More than 80% of electric loads need DC electricity rather than AC at the moment. If DC power could be supplied directly to the terminal loads, power conversion stages including rectifiers, converters, and power adapters can be reduced or simplified. Therefore, DC microgrids may be able to improve energy efficiency of power distribution systems. In addition, DC microgrids can increase the penetration level of renewable energy resources because many renewable energy resources such as solar photovoltaic(PV) generators, fuel cells, and batteries generate electric power in the form of DC power. The integration of the DC generators to AC electric power systems requires the power conversion circuits that may cause additional energy loss. This paper discusses the capability and feasibility of DC microgrids with regard to energy efficiency analysis through detailed dynamic simulation of DC and AC microgrids. The dynamic simulation models of DC and AC microgrids based on the Microgrid Test System in KEPCO Research Institute are described in detail. Through simulation studies on various conditions, this paper compares the energy efficiency and advantages of DC and AC microgrids.

• Journal of Power Electronics
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• 제3권4호
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• pp.230-238
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• 2003

Electric vehicles (EV) demands for greater acceleration, performance and vehicle range in pure electric vehicles plus mandated requirements to further reduce emissions in hybrid electric vehicles (HEV) increase the appeal for combined on-board energy storage systems and generators. And the power electronics plays an important role in providing an interface between fuel cells (FC) and loads. This paper deals with a multiple input DC-DC power converter devoted to combine the power flowing of multi-source on energy systems. The multi-source is composed of (i) FC system as a prime power demands, (ii) super capacitor banks as energy storage devices for high and intense power demands, (iii) superconducting magnetic energy storage system (SMES), (iv) multiple input DC-DC power converter and (v) a three phase inverter-fed permanent magnet synchronous motor as a drive. In this system, It is used super capacitor banks and superconducting magnetic energy replaces from the battery system. The modeling and transient performance simulation is effective for reducing transient influence caused by sudden charge of effective load. The main purpose of power electronic converters is to convert the DC power output from the fuel cell and other to a suitable AC voltage, which can be connected to electric loads directly (PMSM). The fuel cell and other output is connected to the DC-DC converter, which regulates the DC link voltage.

• 조명전기설비학회논문지
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• 제20권2호
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• pp.29-37
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• 2006

중화학 공업은 전해조를 포함한 비선형 부하를 가지고 있다. AC-DC 컨버터가 화학공장의 전해조에 널리 쓰이고 있고, 전해조는 DC에 연결된 구조이다. 컨버터는 고조파 전류를 발생시키고, 전력계통의 전압을 왜곡시킨다. 본 논문에서는 전해조 부하의 고조파 현장 측정과 국제 고조파 관리 기준인 IEC 61000-3-6과 IEEE 519-1992에 의한 고조파 평가를 심도있게 분석한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권3호
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• pp.300-312
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• 2014

A single-inductor multiple-output (SIMO) DC-DC converter providing buck and boost outputs with a new switching sequence is presented. In the proposed switching sequence, which does not require any additional blocks, input energy is delivered to outputs continuously by flowing current through the inductor, which leads to high conversion efficiency regardless of the balance between the buck and boost output loads. Furthermore, instead of multiple output loop compensation, only the freewheeling current feedback loop is compensated, which minimizes the number of off-chip components and nullifies the need for the equivalent series resistance (ESR) of the output capacitor for loop compensation. Therefore, power conversion efficiency and output voltage ripples can be improved and minimized, respectively. Implemented in a 0.35-${\mu}m$ CMOS, the proposed SIMO DC-DC converter achieves high conversion efficiency regardless of the load balance between the two outputs with maximum efficiency reaching up to 82% under heavy loads.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.786-794
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• 2015

In this paper, a new power control strategy for the bipolar-type low voltage direct current (LVDC) distribution system is being proposed. The dc distribution system is considered as an innovative system according to the increase of dc loads and dc output type distribution energy resources (DERs) such as photovoltaic (PV) systems and energy storage systems (ESS). Since the dc distribution system has many advantages such as feasible connection of DERs, reduction of conversion losses between dc output sources and loads, no reactive power issues, it is very suitable solution for new type buildings and residences interfaced with DERs and ESSs. In the bipolar-type, if it has each grid-interfaced converter, both sides (upper, lower-side) can be operated individually or collectively. A complementary power control strategy using two ESSs in both sides for effective and reliable operation is proposed in this paper. Detailed power control methods of the host controller and local controllers are described. To verify the performances of the proposed control strategy, simulation analysis using PSCAD/EMTDC is being performed where the results show that the proposed strategy provides efficient operations and can be applied to the bipolar-type dc distribution system.

• 전력전자학회논문지
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• 제17권1호
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• pp.27-33
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• 2012

Internet Data Centers (IDC), as essential facilities for modern IT industry, typically have scores of MW of concentrated electric loads. Uninterruptible Power Supplies (UPS) are necessary for the power feed system of IDCs because of stable power requirement. Thus, conventional AC power feed systems of IDCs have three cascaded power conversion stages such as (AC-DC), (DC-AC), and (AC-DC), which results in very low conversion efficiency. On the contrary, DC power feed systems need just a single power conversion stage (AC-DC) supplying AC mains power to DC server loads, which gives comparatively high conversion efficiency and reliability. This paper compares the efficiencies between 220V AC power feed system and 300V DC power feed system on equal load conditions which were established in Mok-Dong IDC of Korea Telecom company (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is around 15% higher than that of the 220V AC power feed system.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.379-384
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• 2000

The reactive and harmonic current components of dc loads can be compensated by the three-phase hybrid power filter (HPF) system. After compensation, the resulting current has sinusoidal and in-phase components with the source voltage. The HPF system is constructed by an active filter and passive filters. The passive filter reduce the 5th and 7th harmonic of the load current. The active filter compensates the remainder of the load current. Using the HPF system, a low cost harmonic compensator can be made. Performance of the HPF system is verified through simulation,