• 조명전기설비학회논문지
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• 제15권2호
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• pp.73-79
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• 2001

본 논문은 심플한 단상 에어컨의 역률 개선회로에 관해 설명한다. 정류기에 역률제어회로를 적용함에 의해서 전원선으로의 고조파 삽입을 줄일 수 있고, 효율을 향상시킬 수 있으며, 기존의 인버터와 비교해서 전체 시스템 가격을 낮출 수 있다. 또한 역률제어회로의 출력전압을 안정화함에 의해서 시스템 성능을 향상시킨다. 다이오드 정류기의 전류 파형을 향상시키기 위해 전압 다이오드 정류기에 대한 새로운 원리를 제안한다. 제안한 회로의 설계방법은 시뮬레이션과 실험에 의해 확인하였다. 그리고 기존의 펄스폭변조 인버터와 반펄스폭변조 인버터를 비교하였으며, 제안된 HPWM 인버터에 의해서 낮은 스위칭 손실과 오버슈팅을 제어할 수 있다.

• 전력전자학회논문지
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• 제10권1호
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• pp.38-44
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• 2005

전압형 인버터에서 데드 타임은 직류단 단락을 방지하기 위하여 필요하다. 데드 타임 효과는 출력 전압, 출력 전류의 왜곡으로 나타난다. 최근 많은 논문에서 데드 타임 보상 방법에 대한 연구가 이루어졌다. 본 논문에서는 데드타임을 보상하는 것이 아니라 데드 타임이 없는 인버터를 제안한다. 부하전류를 측정할 필요도 없으며 데드 타임보상을 위한 계산도 필요 없다. 이는 인버터의 각 레그에 트랜스포머를 추가함으로써 가능하다. 제안된 방법의 각 모드 해석이 선행되고 타당성을 위한 시뮬레이션 결과가 제시된다.

• Journal of Power Electronics
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• 제15권1호
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• pp.202-215
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• 2015

This paper investigates the stability and performance of model predictive controlled active-front-end (AFE) rectifiers for energy storage systems, which has been increasingly applied in power distribution sectors and in renewable energy sources to ensure an uninterruptable power supply. The model predictive control (MPC) algorithm utilizes the discrete behavior of power converters to determine appropriate switching states by defining a cost function. The stability of the MPC algorithm is analyzed with the discrete z-domain response and the nonlinear simulation model. The results confirms that the control method of the active-front-end (AFE) rectifier is stable, and that is operates with an infinite gain margin and a very fast dynamic response. Moreover, the performance of the MPC controlled AFE rectifier is verified with a 3.0 kW experimental system. This shows that the MPC controlled AFE rectifier operates with a unity power factor, an acceptable THD (4.0 %) level for the input current and a very low DC voltage ripple. Finally, an efficiency comparison is performed between the MPC and the VOC-based PWM controllers for AFE rectifiers. This comparison demonstrates the effectiveness of the MPC controller.

• Journal of Electrical Engineering and Technology
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• 제6권5호
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• pp.595-604
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• 2011

A three-phase three-level shunt active filter controlled by fuzzy logic current controller which can compensate current harmonics generated by nonlinear loads is presented. Three-level inverters and fuzzy controllers have been successfully employed in several power electronic applications these past years. To improve the conventional pwm controller performance, a new control scheme based on fuzzy current controller is adopted for three-level (NPC) shunt active filter. The scheme is designed to improve compensation capability of APF by adjusting the current error using a fuzzy rule. The inverter current reference signals required to compensate harmonic currents use the synchronous reference detection method. This technique is easy to implement and achieves good results. To maintain the dc voltage across capacitor constant and reduce inverter losses, a proportional integral voltage controller is used. The simulation of global system control and power circuits is performed using Matlab-Simulink and SimPowerSystem toolbox. The results obtained in transient and steady states under various operating conditions show the effectiveness of the proposed shunt active filter based on fuzzy current controller compared to the conventional scheme.

• Journal of Power Electronics
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• 제10권6호
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• pp.673-679
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• 2010

Input-series-output-parallel (ISOP) connected DC-DC converters enable low voltage rating switches to be used in high voltage input applications. In this paper, a DSP is adopted to generate digital phase-shifted PWM signals and to fulfill the closed-loop control function for ISOP connected two full-bridge DC-DC converters. Moreover, a stable output current sharing control strategy is proposed for the system, with which equal sharing of the input voltage and the load current can be achieved without any input voltage control loops. Based on small signal analysis with the state space average method, a loop gain design with the proposed scheme is made. Compared with the conventional IVS scheme, the proposed strategy leads to simplification of the output voltage regulator design and better static and dynamic responses. The effectiveness of the proposed control strategy is verified by the simulation and experimental results of an ISOP system made up of two full-bridge DC-DC converters.

• 전력전자학회논문지
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• 제19권1호
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• pp.71-79
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• 2014

In this paper, a new grid voltage estimation algorithm without voltage sensors is proposed for the three-phase vienna rectifier. Generally, input voltage sensor circuits increase size and cost of the PWM rectifier In order to reduce the cost and size and in order to increase reliability from the electrical noise, grid voltage estimation scheme without input voltage sensor is highly required. In this paper, the grid voltage estimation algorithm is proposed by a simple MRAS(Model Reference Adaptive System) observer without input voltage sensors. The validity of the proposed method is proven by simulation and experiment on the three-phase vienna rectifier system.

• 전력전자학회논문지
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• 제17권5호
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• pp.409-415
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• 2012

This paper presents a new software-based on-line dead-time compensation technique for a single-phase grid-connected photovoltaic (PV) inverter system. To prevent a short circuit in the inverter arms, a switching delay time must be inserted in the pulse width modulation (PWM) signals. This causes the dead-time effect, which degrades the system performance around zero-crossing point of the output current. To reduce the dead-time effect around the zero-crossing point of grid current, a harmonic mitigation of grid current is used as an additional part of the synchronous frame current control scheme. This additional task mitigates the harmonic components caused by the dead-time from the grid current. Simulation and experimental results are shown to verify the effectiveness of the proposed dead-time compensation method in the single-phase grid-connected inverter system.

• 전력전자학회논문지
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• 제16권1호
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• pp.20-29
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• 2011

본 논문에서는 동특성이 느린 용융탄산염 연료전지 (Molten Carbonate Fuel Cell, MCFC) 스택을 사용하여 계통사고 시 추가적인 UPS (Uninterruptible Power Supply) 없이 비상부하 (Critical Load)로 전력 공급이 가능하고, 사고 발생 후에도 정격전력으로 발전 가능한 비상부하 추종형 백업 시스템을 제안한다. 제안된 MCFC 발전 시스템용 비상부하 추종형 백업 시스템은 3상 인버터로 구성된 PCS (Power Conditioning System) 출력단에 3상 PWM 컨버터를 연결한 구조이고, 비상부하 추종이 가능한 추가적인 제어 알고리즘을 가지는 Load Leveler를 제어한다. 제안된 비상부하 추종형 백업 시스템의 회로와 제어 알고리즘의 타당성을 5kW 기반의 컴퓨터 시뮬레이션을 통하여 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.26-28
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• 2005

Induction generator is the most common generator in wind energy systems because of its simplicity, ruggedness, little maintenance, price and etc. But the main drawbacks in induction generator is its need of reactive power means to build up the terminal voltage. This drawback is not an obstacle today where PWM inverters can accurately supplies the induction generator with its need from reactive power. For a insurance of three-phase induction generator requires capacitive reactance of the terminal. Most of previous work uses numerical iterative method to determine this minimum capacitor. But the numerical iteration takes long time and divergence may be occurs. In this paper is presented the design methods of the minimum self-excited capacitor required for induction generator operation. And a new formula from the equivalent circuit for stable generation operation of self-excited induction generator calculates the proper capacity to obtain the terminal voltage of the load stage. The validity of proposed design methods is confirmed by experimental and computed results.

• 한국정밀공학회지
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• 제16권9호
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• pp.34-40
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• 1999

In order to establish the design technique of the robust current controller in d.c series wound motor driver system, this paper proposes a method of the compensated Bang-Bang current control using d.c series wound motor driver system under the improperly variable load to get minimum time for the torque control. The compensated Bang-Bang current controller structure is simpler than that of PID plus Bang-Bang controller. This paper shows that a general 16 bits microprocessor is efficiently used to implement such an algorithm. The calculation time of software is extremely small when compared with that of conventional PID plus Bang-Bang controller. Both nonlinear operating characteristics of digital switching elements and describing function methods are used for the analysis and synthesis. Real-time implementation of the compensated Bang-Bang current controller is achieved. The concept of design strategy of the control and the PWM waveform generation algorithms are presented in this paper.