• 조명전기설비학회논문지
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• 제15권1호
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• pp.51-58
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• 2001

현재의 DC-DC 컨버터는 스위칭 주파수를 높임에 따라 전체 손실이 현저히 증가하고 있다. 스위칭 손실을 줄이기 위해 사용한 예전의 soft 스위칭기술은 심지어 전압/전류 부담(stress)을 가중시켰다. 이에 대한 대책으로 soft 스위칭을 위한 공진회로를 주전력선에 병렬로 연결하고 보조 스위치를 이용하여 주 스위치의 turn-on 직전에만 공진회로를 동작시키는 유사공진 컨버터(QRC)기술이 발전되었다. 그러나 이 기술을 사용하는 컨버터에서도 손실은 여전히 발생하며 효율에 대한 전체적인 손실량은 알 수 있지만 각 소자에 대한 손실량은 알아볼 수 없었다. 따라서 본 논문에서는 컨버터의 주전력단에 사용되는 반도체 소자들의 선형화 된 손실등가 모델을 만들고 스위칭 시의 전압/전류 파형을 바탕으로 선형 특성을 고려하여 전체 손실에 대한 각 소자의 손실과 스위칭 손실을 분석하였다.

• Journal of Power Electronics
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• 제17권5호
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• pp.1363-1371
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• 2017

In this paper, an improved Direct Power Control (DPC) algorithm is presented for grid connected three phase PWM rectifiers. The new DPC approach is based on two main tasks. First the optimization of the look-up table, which is well-known in conventional DPC, is outlined for selecting the optimum converter output voltage vectors. Secondly a very simple and effective method is used to directly calculate their duty cycles from the power errors. Therefore, the measured active and reactive powers are made to track their references using hysteresis controllers. Then two vectors are selected and applied during one control cycle to minimize both the active and reactive power ripples. The main advantages of this method are that there is no need of linear current controllers, coordinates transformations or modulators. In addition, the control strategy is able to operate at constant switching frequencies to ease the design of the power converter and the AC harmonic filter. The control exhibits a good steady state performance and improves the dynamic response without any overshoot in the line current. Theoretical principles of the proposed method are discussed. Both simulation and experimental results are presented to verify the performance and effectiveness of this control scheme.

• Journal of Power Electronics
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• 제14권3호
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• pp.478-487
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• 2014

This study presents a new interleaved three-level zero-voltage switching (ZVS) converter for high-voltage and high-current applications. Two circuit cells are operated with interleaved pulse-width modulation in the proposed converter to reduce the current ripple at the input and output sides, as well as to decrease the current rating of output inductors for high-load-current applications. Each circuit cell includes one half-bridge converter and one three-level converter at the primary side. At the secondary side, the transformer windings of two converters are connected in series to reduce the size of the output inductor or switching current in the output capacitor. Based on the three-level circuit topology, the voltage stress of power switches is clamped at $V_{in}/2$. Thus, MOSFETs with 500 V voltage rating can be used at 800 V input voltage converters. The output capacitance of the power switch and the leakage inductance (or external inductance) are resonant at the transition interval. Therefore, power switches can be turned on under ZVS. Finally, experiments verify the effectiveness of the proposed converter.

• Journal of Power Electronics
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• 제14권6호
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• pp.1109-1118
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• 2014

A Fundamental Frequency Sorting Algorithm (FFSA) is proposed in this paper to balance the voltages of floating dc capacitors for Modular Multilevel Converters (MMCs). The main idea is to change the sequences of the CPS-PWM carriers according to the capacitor voltage increments during the previous fundamental period. Excessive frequent sorting is avoided and many calculating resources are saved for the controller. As a result, more sub-modules can be dealt with. Furthermore, it does not need to measure the arm currents. Therefore, the communication between the controllers can be simplified and the number of current sensors can be reduced. Moreover, the proposed balancing method guarantees that all of the switching frequencies of the sub-modules are equal to each other. This is quite beneficial for the thermal design of the sub-modules and the lifetime of the power switches. Simulation and experimental results acquired from a 9-level prototype verify the viability of the proposed balancing method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(5)
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• pp.143-146
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• 2001

Servomotors, especially linear brushless servomotors have numerous advantages over ball screws, timing belts, rack/pinion drives and friction drives compared wi th rotary servomotors This paper proposes an linear regression method as the estimated ion of unknown parameters from the linear brushless DC motor The estimated parameters are used to tune the gain of controller. In order to agree with this purpose, Digital Signal Processor (TMS320F240), developed for implementation of the motor control, is adopted in this study. The processor playing an important role in controller has A/D converters, PWM generators, riched I/O ports internally.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.6-8
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• 2002

Generally in solar air conditioning system, the diode rectifier is used to build up DC link voltage from AC source. The diode rectifier is simple and cheap but it brings out the problems of low power factor and plentiful harmonics at the AC source. Also It can degrade the utilization rate of solar energy because the reverse of power flow cannot be made. Hence, in this paper to overcome the peak power problems in summer and to endure good AC input characteristics, solar air conditioning system using the PWM converter is proposed. A high input power factor of 97[%] and an efficiency of 98[%] are also obtained. The harmonic guide lines of proposed rectifier is no interfered with inverter switching, resulting in a simple, reliable and low cost ac to dc converters in comparison with the boost type current improving circuits.

• Journal of Power Electronics
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• 제9권1호
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• pp.26-35
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• 2009

A high efficiency active clamp sepic-flyback converter is presented for fuel cell generation systems. The proposed converter is a superposition of a sepic converter mode and. flyback converter mode. The output voltages of the sepic converter mode and flyback converter mode can be regulated by the same PWM technique with constant frequency. By merging the sepic and flyback topologies, they can share the transformer, power MOSFET and active clamp circuit. The result has outstanding advantages over conventional active clamp DC-DC converters: high efficiency, high power density, and component utilization. Simulation results and experimental results are presented to verify the principles of operation for the proposed converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.217-219
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• 2005

This paper presents an improved ZCT (Zero-Current-Transition) PWM DC/DC Boost Converter without additional current stress and conduction loss on the main switch during the resonance period of the auxiliary cell. The auxiliary cell consists of a resonance inductor, a resonant capacitor, an auxiliary switch and the Zero-Current-Switching ranges of the main and the auxiliary switch of the proposed converters are entirely achieved by operating the auxiliary cell. Then Improved ZCT soft switching converter will be discussed. Therefore, the proposed converter has a high efficiency. To show the superiority of this converter is verified through the experiment with a 640W, 50kHz prototype converter.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.619-625
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• 2008

Electrical Power supply System conditions of korea high speed train consists of main transformer, four AC-DC PWM converter of Auxiliary Block, Battery Charger in Power Car and Trailer Car, Trailer Inverter, Auxiliary inverter. Main transformer, at nominal voltage of 25kv supplied to secondary winding nominal output Voltage 383Vac, The Auxiliary block consists of AC-DC converters for generating 670VDC power, Auxiliary inverters for ventilation and air compressor, Trailer car inverter provide three phase power supplies at 440Vac for air conditioning and heating. The Battery charger Trailer and Power car supplies 72VDC all necessary equipment to energize the trainset equipment and suppy essential control. This Paper introduces the combined test results of the power supply system for korea high speed train. The main purpose of this combined test is to verify the performance of the power supply system that is designed to operate up to full load test.

• Journal of Power Electronics
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• 제3권1호
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• pp.62-67
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• 2003

Recently, photovoltaic system has been studied widely as a renewable energy system, because it does not produce environmental pollution and it has infinity energy source from the sun. A study on photovoltaic system has a lot of problems like as reappearance and repetition of some situation in the laboratory experiment for development of MPPT algorithm and islanding detection algorithm. because output characteristics of solar cell are varied by irradiation and surface temperature of solar cell. Therefore, the assistant equipment which emulates the solar cell characteristics which can be controlled arbitrarily by researcher is require to the researchers for reliable experimental data. In this paper, the virtual implement of solar cell (VISC) system is proposed to solve these problems and to achieve reliable experimental result on photovoltaic system. VISC system emulates the solar cell output characteristics, and this system can substitute solar cell in laboratory experiment system. To realize the VISC, mathematical model of solar cell is studied for driving converter and the DC/DC converters are compared in viewpoint of tracking error using computer simulation. Output dynamic characteristic of PV array is varied by irradiation and PWM converter performance is studied using PSIM simulator.