• Journal of Power Electronics
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• 제15권3호
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• pp.660-669
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• 2015

This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.

• 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.

• 에너지공학
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• 제22권4호
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• pp.394-398
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• 2013

최근들어 자동차에어콘 콤프레셔의 전기마그네트식 콘트롤밸브는 내부형 스워시 프레이트형을 사용하고 있다. 이 시스템은 외부로부터 공급되는 전류량(신호)에 의하여 작동되며 동시에 스워시판 작동에 의한 압력은 냉매가 흐르는 비율에 의하여 결정된다. 본 논문에서는 압축기의 크랭크케이스 압력이 전기마그네트 콘트롤 밸브 전기 흐름량에 따른 유량의 값을 측정하여 엔진의 효율을 향상시키고자 한다.

• 한국산학기술학회논문지
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• 제13권11호
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• pp.5409-5415
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• 2012

압전 세라믹 액추에이터는 스프레이, 디스펜서, 밸브제어와 같은 다양한 산업제품들에 응용된다. 압전 세라믹 소자의 기계적인 변위의 크기는 인가 전압의 크기에 의해 정해지므로, 압전 세라믹 액추에이터 구동을 위해서는 고전압 전원장치와 함께 전력증폭기가 필요하다. 본 논문에서는 간단하고 크기가 작은 H-브리지 형태의 전력증폭기와 플라이백 고전압 스위칭 모드 전원장치를 개발하였다. H-브리지 형태의 전력증폭기는 펄스폭 변조를 이용하여 압전 세라믹 액추에이터에 대한 에너지 입력의 크기를 쉽게 조절할 수 있다는 장점이 있다.

• 전자공학회논문지T
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• 제36T권1호
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• pp.41-50
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• 1999

브러시리스 직류전동기는 보수 유지의 용이성과 가제어성의 특성으로 인하여 자동화 공장에서 많이 활용되고 있다. 본 논문에서는 산업현장에서 고성능과 유용성을 가지는 정현파형 브러시리스 직류전동기의 속도제어 서보시스템을 설계하였다. 이 서보시스템은 전동기의 구동에 필요한 제어장치와 새로운 자동동조 PI제어 알고리즘에 의해서 구현되어진다. 주 제어기와 센서 신호처리부는 고속연산의 필요성과 설계의 적절성 때문에 DSP를 사용하였고, DSP에서 출력되는 속도지령을 정확히 추종하기 위해 하드웨어 PWM 전류제어기를 구현하였다. 실험 결과 지령치에 대한 빠른 응답과 지령치 변화에 따른 정상상태 응답이 오버슈트 없이 잘 수렴함을 확인 할 수 있었다.

• 한국분무공학회지
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• 제13권3호
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• pp.126-133
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• 2008

The atomization characteristics of the dual air supplying two-fluid nozzle were investigated experimentally using PIV and PDA systems. The twin-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air, and the main nozzle to produce sprays. The main nozzle has the swirler with four equally spaced tangential slots, which gives the injecting fluid an angular momentum. The swirl angle in the swirler varied with $0^{\circ}$, $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$. The ratios of carrier air to assist air and ALR (total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the AMD and SMD distributions of the sprays were measured using PDA system. As a result, the SMD distribution increases along the radial distance, and it decreases with the increase of swirl angle in swirler.

• Journal of Power Electronics
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• 제16권4호
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• pp.1469-1482
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• 2016

In hybrid energy storage systems, supercapacitors are usually connected in series to meet the required voltage levels. Equalizers are effective in prolonging the life of hybrid energy storage systems because they eliminate the voltage imbalance on cells. This study proposes a modularized equalizer, which is based on a combination of a half-bridge inverter, an inductor, and two auxiliary capacitors. The proposed equalizer inherits the advantages of inductor-based equalization systems, but it also offers unique merits, such as low switching losses and an easy-to-use control algorithm. The zero-voltage switching scheme is analyzed, and the power model is established. A fixed-frequency operation strategy is proposed to simplify the control and lower the cost. The switching patterns and conditions for zero-voltage switching are discussed. Simulation results based on PSIM are presented to verify the validity of the proposed equalizer. An equalization test for two supercapacitor cells is performed. An experimental hybrid energy storage system, which consists of batteries and supercapacitors, is established to verify the performance of the proposed equalizer. The analysis, simulation results, and experimental results are in good agreement, thus indicating that the circuit is practical.

• 전력전자학회논문지
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• 제17권4호
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• pp.298-305
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• 2012

This paper proposes a soft switching boost converter with an auxiliary resonant circuit. The auxiliary resonant circuit is added to a general boost converter and that is composed of one switch, one diode, one inductor and two capacitors. The resonant network helps the main switch to operate with a zero voltage switching(ZVS) and auxiliary switch also operates under the zero voltage and zero current conditions. The soft switching range is extended by the auxiliary switch and it is possible to control the proposed converter with a pulse width modulation(PWM). The ZVS and ZCS techniques make switching losses decreased and efficiency of the system improved. A theoretical analysis is verified through the simulation and experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2221_2222
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• 2009

본 논문에서는 BLDC 운전 중 각 상의 결상 사고에 따른 토크 및 속도의 최적화에 대해 연구하였다. BLDC 모터의 구동을 위하여 ATmega16이 사용되었으며 제어기법으로는 PWM(Pulse Width Modulation) 기법이 사용된다. 속도 제어는 Hall Sensor의 검출 속도에 따라 Duty비를 제어하여 이루어지며 회전자 위치는 Hall Sensor 검출 방식을 통하여 이루어진다. 이러한 BLDC 모터를 이용하여 예기치 못한 결상 상황의 발생 시 토크의 감소로 인한 급제동에 대비하여 부하에 상응하는 토크를 최대한 낼 수 있도록 알고리즘을 구현하였다.

• 조명전기설비학회논문지
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• 제26권9호
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• pp.1-7
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• 2012

In this paper, we present a new lighting control method considering ambient light in addition to the required lighting illumination for efficient energy saving of a LED stand. We estimate accurate environmental illuminance using a cheap illuminance sensor by modeling measured- and actual-illuminance using quadratic polynomial approximation. The relation between PWM(Pulse Width Modulation) duty ratio and illuminance intensity is modeled by a linear model. Illumination of the LED stand is controlled by estimating the difference of required illumination and the estimated ambient illumination. The developed LED stand has reduced electric energy consumption compared with a conventional manually controlled LED stand with the same lighting source. In addition, human subject evaluation shows that the LED stand, which is applied the proposed method, is more satisfactory than conventional ones since the proposed automatic controlled illumination produce more accurately required lighting and it is convenient.