• 전기학회논문지
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• 제62권10호
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• pp.1383-1389
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• 2013

There were telecommunication noise and malfunctions of the electronic devices occurred over a wide area due to the high harmonic voltage and/or current levels of the Back-to-back converter in the DFIG wind power system even though the magnitude of all harmonics is within the international standards. The triangular carrier signals of the PWM used in the power converter system is related to the telecommunication noise because they are in the range of audible frequencies and amplified by a variety of the standing waves that were excited by harmonic voltage sources in the weak grid system such as a long distance distribution transmission lines. This paper describes the characteristics of the harmonics in the wind turbine-generator, numerical analysis and simulation of the harmonics resonance phenomena in the distribution lines as well as measuring induced voltage of the telecommunication lines in parallel with power lines in order to verify the root cause of the telecommunication noise. These noise problems can occur in a wind turbine power system with a non-linear converter at any time, as well as photovoltaic power system. So, the preliminary review of suitable filter devices and switching frequencies of the PWM have to be required by considering the stability of the controller at the design stage but as part of the measures the effect of the telecommunication cable shields was analyzed by comparing the measured data between multi-conductor with/without shields so as to attenuate the sources of the harmonics voltage induced into the telecommunication lines and to apply the most cost-effective measures in the field.

• 조명전기설비학회논문지
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• 제18권5호
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• pp.61-68
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• 2004

최근, 연료전지는 새로운 발전시스템으로 주목받고 있다. 연료전지는 저전압/대전류의 전기적 특성을 가진다. 그러므로 일반 상용부하에 적용하기 위해서는 승압용 컨버터와 인버터가 필요하다. 제안된 시스템은 연료전지의 전압을 380[Vdc]로 승압하기 위한 절연형 DC-DC 컨버터와 단상 220[Vac]로 변환하기 위한 LC 필터를 가진 PWM 인버터로 구성된다. 또한, 연료전지 발전시스템용 양방향 DC-DC 컨버터는 부하 응답 특성을 개선시키기 위하여 구성하였다. 본 논문에서는 풀 브리지 컨버터와 단상 인버터를 설계하고 제작하였으며, 시뮬레이션과 실험을 통해 연료전지 발전 시스템이 분산전원에 적용이 가능함을 보여준다.

• 한국산학기술학회논문지
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• 제11권2호
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• pp.497-507
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• 2010

본 논문은 상이한 누설인덕턴스를 가진 두 개의 변압기를 이용하여 전류불균형을 개선한 하프브리지 LLC 공진형 컨버터를 제안한다. 제안된 컨버터는 변압기의 누설인덕턴스와 자화인덕턴스 및 공진커패시턴스를 이용하여 공진하고, 넓은 부하영역을 가지며, 경부하에서도 영전압스위칭 조건을 만족한다. 직/병렬로 연결된 두 개의 변압기는 동작모드에 따라 변압기 또는 공진인덕턴스로써 교대로 동작하고, 변압기 2차측에는 누설인덕턴스를 이용하므로 별도의 출력 필터인덕턴스가 필요하지 않다. 또한 제안된 컨버터는 두 변압기의 상이한 누설인덕턴스와 하프브리지 스위치의 비대칭 펄스폭변조를 이용하여 2차측 정류다이오드의 전류불균형 문제를 개선한다. 본 논문에서는 제안된 컨버터의 동작원리를 모드별로 설명하고 프로토타입 컨버터의 설계 예를 제시한다. 제안된 컨버터의 우수한 성능을 입증하기 위하여 설계된 프로토타입의 회로파라미터로써 프로토타입 컨버터를 제작하고 실험하였다. 제안된 컨버터의 우수한 성능을 실험결과를 통하여 보인다.

• 대한전자공학회논문지SD
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• 제45권3호
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• pp.44-53
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• 2008

본 논문에서는 휴대용 오디고 제품의 헤드폰 구동을 위한 델타-시그마 변조기법 기반의 D급 증폭기를 제안한다. 제안된 D급 증폭기는 고성능 단일 비트 4차 델타-시그마 변조기를 이용하여 펄스폭 변조 신호를 발생시킨다. 높은 신호 대 잡음비를 얻는 것과 동시에 시스템의 안정성 확보를 위하여 시뮬레이션을 통해 변조기 루프필터의 폴과 제로를 최적화하였다. 테스트 칩은 $0.18{\mu}m$ CMOS 공정으로 제작되었다. 칩 면적은 $1.6mm^2$ 이며, 20Hz 부터 20kHz까지의 신호대역을 대상으로 동작한다. 3V 전원전압과 32옴의 로드를 사용하여 측정된 출력은 0.03% 이하의 전고조파 왜율을 갖는다.

• Journal of Power Electronics
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• 제18권1호
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• pp.70-80
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• 2018

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

• Journal of Power Electronics
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• 제16권5호
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• pp.1904-1917
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• 2016

The moving average filter (MAF) is widely utilized to improve the disturbance rejection capability of phase-locked loops (PLLs). This is of vital significance for the grid-integration and stable operation of power electronic converters to electric power systems. However, the open-loop bandwidth is drastically reduced after incorporating a MAF into the PLL structure, which makes the dynamic response sluggish. To overcome this shortcoming, some new techniques have recently been proposed to improve the transient response of MAF-based PLLs. In this paper, a comprehensive performance comparison of advanced MAF-based PLL algorithms is presented. This comparison includes HPLL, MPLC-PLL, QT1-PLL, and DMAF-PLL. Various disturbances, such as grid voltage sag, voltage flicker, harmonics distortion, phase-angle and frequency jumps, DC offsets and noise, are considered to experimentally test the dynamic performances of these PLL algorithms. Finally, an improved positive sequence extraction method for a HPLL under the frequency jumps scenario is presented to compensate for the steady-state error caused by non-frequency adaptive DSC, and a satisfactory performance has been achieved.

• 전력전자학회논문지
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• 제7권2호
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• pp.158-164
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• 2002

본 논문은 기존의 1차 예측 기법과 반복 제어기법을 이용하여 LC 필터와 정류 부하 등의 비선형 부하를 가지는 UPS 인버터의 출력전압 파형의 개선에 관한 연구이다. 기존의 1차 예측 기법은 정류부하에 대하여 우수한 특성을 가지므로 출력전류의 예측에 적합하나 정류 부하와 같은 비선형적인 부하의 정상 상태 오차를 보상하기에는 충분하지 못한 단점을 가진다. 따라서, 정상상태 오차를 최소화 할 수 있는 반복제어 기법을 적용하여 UPS 출력전압을 개선시키고자 한다. 제안된 제어기법에 대한 타당성을 시뮬레이션으로 검증하고, 이를 바탕으로 LC 필터를 가지는 3 kVA, 60 Hz UPS시스템을 제작하여 실험으로 검증한다

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.195-204
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• 2015

In this paper, the development of a cost-effective active power filter/uninterruptible power supply (APF/UPS) system with seamless mode transfer is described. The proposed scheme employs a pulse-width-modulation (PWM) voltage-source inverter and has two operational modes. First, when the source voltage is normal, the system operates as an APF, which compensates for the harmonics and power factor while boosting the DC-link voltage to be ready for the disturbance, without an additional DC charging circuit. A simple algorithm to detect the load current harmonics is also proposed. Second, when the source voltage is out of the normal range (owing to sag, swell, or outage), it operates a UPS, which controls the output voltage constantly by discharging the DC-link capacitor. Furthermore, a seamless transfer method for the single-phase inverter between the APF mode and the UPS mode is also proposed, in which an IGBT switch with diodes is used as a static bypass switch. Dissimilar to a conventional SCR switch, the IGBT switch can implement a seamless mode transfer. During the UPS operation, when the source voltage returns to the normal range, the system operates as an APF. The proposed system has good transient and steady-state response characteristics. The APF, charging circuit, and UPS systems are implemented in one inverter system. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype APF/UPS system rated at 3 kVA.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.905-908
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• 2005

본 논문에서는 class AB opamp 를 채용한 384kHz differential PWM 신호를 입력으로 하는 2-channel stereo audio amplifier 블록을 공급전압 3.3V 조건에서 SMIC 0.18um thick oxide 기술을 이용하여 설계한다. 여기서 class AB opamp 는 공정 변화에 따른 quiescent current가 변하는 것을 최소화하기 위하여 adaptive load 를 사용하며, 전체적으로는 3 차 Butterworth lowpass filter 와 differential-to-single converter 로 구성된 2 개의 audio amplifier 와 출력전압이 ${\frac{1}{2}}Vdd$ 인 common output 블록으로 구성된다. 이러한 설계를 통하여 32ohm 의 저항 load 를 구동할 수 있는 -60dB THD, 전체 quiescent current 2mA 대인 CMOS class AB stereo audio amplifier 를 구현하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.317-322
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• 2003

A novel three-level DC/DC converter (TLC)for high power applications operating from high input voltage Is proposed. Its switch voltage stress can be ensured to be only one-half of the Input voltage. Nevertheless, since all input voltage is applied to the transformer primary side, it has good turns ratio. The driving method of each module is same as those of the conventional phase-shifted ZVS full bridge PWM converter (PSFB) and the zero-voltage-switching (ZVS) of the leading leg are achieved exactly in the same manner as that of the PSFB. Moreover, its three-level operation can considerably reduce the current ripple through the output inductor and it has no problems of the DC-link voltage unbalance. Therefore, it features a low voltage stress, high efficiency, low EMI, high power density, and small sized filter. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 200W, 600V/DC-48V/DC prototype are presented.