• 전기전자학회논문지
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• 제12권3호
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• pp.176-183
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• 2008

본 논문에서는 DTMOS(Dynamic Threshold voltage MOSFET) 스위칭 소자를 사용한 고 효율 전원 제어 장치 (PMIC)를 제안하였다. 높은 출력 전류에서 고 전력 효율을 얻기 위하여 PWM(Pulse Width Modulation) 제어 방식을 사용하여 PMIC를 구현하였으며, 낮은 온 저항을 갖는 DTMOS를 설계하여 도통 손실을 감소시켰다. 벅 컨버터(Buck converter) 제어 회로는 PWM 제어회로로 되어 있으며, 삼각파 발생기(Saw-tooth generator), 밴드갭기준 전압 회로(Band-gap reference circuit), 오차 증폭기(Error amplifier), 비교기(Comparator circuit)가 하나의 블록으로 구성되어 있다. 삼각파 발생기는 그라운드부터 전원 전압(Vdd:3.3V)까지 출력 진폭 범위를 갖는 1.2MHz 발진 주파수를 가지며, 비교기는 2단 연산 증폭기로 설계되었다. 그리고 오차 증폭기는 70dB의 DC gain과 $64^{\circ}$ 위상 여유를 갖도록 설계하였다. Voltage-mode PWM 제어 회로와 낮은 온 저항을 스위칭 소자로 사용하여 구현한 DC-DC converter는 100mA 출력 전류에서 95%의 효율을 구현하였으며, 1mA이하의 대기모드에서도 높은 효율을 구현하기 위하여 LDO를 설계하였다.

• 융합신호처리학회논문지
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• 제14권1호
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• pp.39-44
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• 2013

본 논문에서는 멀티암(multi-arm) 스파이럴 안테나용 디지털 위상천이기(digital phase-shifter)를 힐버트 변환(Hillbert transform)을 이용하여 설계하였다. 힐버트 변환은 입력신호에 포함된 모든 주파수 성분을 $90^{\circ}$ 위상천이 시키며, 퓨리에 변환(Fourier transform)과 역퓨리에 변환(Inverse FIT)을 통해 구현된다. 디지털 위상천이기는 ADC(Analog-digital converter)로 샘플링된 입력신호에 힐버트 변환을 적용하여 위상차가 $90^{\circ}$인 두 신호를 생성하고, 이 두 신호를 이용하여 입력신호의 위상을 천이위상만큼 천이시키게 한다. 힐버트 변환 기반의 디지털 위상천이기는 Xilinx사의 System generator로 설계되었고, 입력 잡음, FFT 포인트 수, 샘플링 주기, 입력신호의 초기위상 및 천이 위상각 등에 따른 위상천이 성능을 시뮬레이션 하였으며, Matlab 결과와 비교하여 일치함을 확인하였다.

• 조명전기설비학회논문지
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• 제25권7호
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• pp.97-104
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• 2011

This paper presents modeling and control for the emerging IGBT converter-based high-voltage direct-current system (IGBT-HVDC). This paper adds to the representation of the IGBT-HVDC system in the dq-synchronous reference frame and its decoupled control scheme. Additionally, since the IGBT-HVDC is able to actively support the grid due to its capacity to control independently active and reactive power production, a reactive power control scheme is presented in order to regulate/contribute to the voltage at a remote location by taking into account its operational state and limits. The ability of the control scheme is assessed and discussed by means of simulations using ahybrid power system, which consists of a permanent magnetic synchronous-generator (PMSG) based wind turbine, an IGBT-HVDC, and a local load.

• Journal of Power Electronics
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• 제17권1호
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• pp.232-241
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• 2017

Advanced control algorithms must be used to make wind power generation truly cost effective and reliable. In this study, we develop a new and simple control scheme that employs model predictive control (MPC), which is used in permanent magnet synchronous generators and grid-connected inverters. The proposed control law is based on two points, namely, MPC-based torque-current control loop is used for the generator-side converter to reach the maximum power point of the wind turbine, and MPC-based direct power control loop is used for the grid-side converter to satisfy the grid code and help improve system stability. Moreover, a simple prediction scheme is developed for the direct-drive wind energy conversion system (WECS) to reduce the computation burden for real-time applications. A small-scale WECS laboratory prototype is built and evaluated to verify the validity of the developed control methods. Acceptable results are obtained from the real-time implementation of the proposed MPC methods for WECS.

• 신재생에너지
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• 제8권3호
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• pp.14-22
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• 2012

Performance of photovoltaic (PV) generator systems relies on its operating conditions. Maximum power extracted from PV generators depends strongly on solar irradiation, load impedance, and ambient temperature. A most maximum power point tracking (MPPT) algorithm is based on a perturb and observe method and an incremental conductance method. It is well known the latter is better in terms of dynamics and tracking characteristics under condition of rapidly changing solar irradiation. However, in case of digital implementation, the latter has some error for determining a maximum power point. This paper presents a PID based MPPT algorithm for such PV systems. We use neural network technique for determining PID parameters by online learning approach. And we construct a boost converter to regulate the output voltage from PV generator system. Computer simulation is carried out to evaluate the proposed MPPT method and we accomplish comparative study with a perturb and observe based MPPT method to prove its superiority.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.171-171
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• 2010

An innovative design of a floating-buoy wave energy converter (WEC) using hydrostatic transmission (HST), named HSTWEC, is presented in this paper. The system is designed to convert ocean wave fluctuation into electricity by using the HST circuit and an electric generator. Based on the floating-buoy concept, the wave forces the sub-buoy to move up and down. Consequently, the electric power can be obtained from the generator in both the moving directions of the sub-buoy through the HST circuit as shown in Fig. 1. In order to investigate the HSTWEC operations, a mathematical model of the system is indispensible. In addition, the method to control the HSTWEC, including: pump displacement control, tension adjustment control and ballast weight control, is also discussed in this paper. Finally, the design concept as well as simulation results indicated that this HSTWEC design is an effective solution and possible to fabricate for wave energy generation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.261-264
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• 2006

In this paper, doubly-fed induction-type wind power generation system simulation model for grid connection is developed. The simulation model is based on PSCAD/EMTDC and consists of rotor-blade, blade controller, generator power converter and generator controller Blade controller controls the blade pitch angle for starting, peak power limiting and emergency condition. Generator controller controls the generator output power to maximize the system efficiency. Simulation results are shown for the variable wind speed conditions. The simulation model can be utilized for study of actual interaction between wind turbine and grid for reliable operation and protection of power system.

• Journal of Power Electronics
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• 제6권1호
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• pp.52-66
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• 2006

This paper proposes a wind energy conversion system connected to a grid using a self-excited induction generator (SEIG) based on the maximum power point tracking (MPPT) control scheme. The induction generator (IG) is controlled by the MPPT below the base speed and the maximum energy can be captured from the wind turbine. Therefore, the stator currents of the IG are optimally controlled using the indirect field orientation control (IFOC) according to the generator speed in order to maximize the generated power from the wind turbine. The SEIG feeds a (CRPWM) converter which regulates the DC-link voltage at a constant value where the speed of the IG is varied. Based on the IG d-q axes dynamic model in the synchronous reference frame at field orientation, high-performance synchronous current controllers with satisfactory performance are designed and analyzed. Utilizing these current controllers and IFOC, a fast dynamic response and low current harmonic distortion are attained. The regulated DC-link voltage feeds a grid connected CRPWM inverter. By using the virtual flux orientation control and the synchronous frame current regulators for the grid connected CRPWM inverter, a fast current response, low harmonic distortion and unity power factor are achieved. The complete system has been simulated with different wind velocities. The simulation results are presented to illustrate the effectiveness of the proposed MPPT control scheme for a wind energy system. In the simulation results, the d-q axes current controllers and DC-link voltage controller give prominent dynamic response in command tracking and load regulation characteristics.

• Journal of Power Electronics
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• 제16권3호
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• pp.1176-1189
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• 2016

In this paper, a novel quasi-direct power control (Q-DPC) scheme based on a resonant frequency adaptive proportional-resonant (PR) current controller with a variable frequency resonant phase locked loop (RPLL) is proposed, which can achieve a fast power response with a unity power factor. It can also adapt to variations of the generator frequency in T-type Three-level shaft synchronous generator (SSG) converters. The PR controller under the static α-β frame is designed to track ac signals and to avert the strong cross coupling under the rotating d-q frame. The fundamental frequency can be precisely acquired by a RPLL from the generator terminal voltage which is distorted by harmonics. Thus, the resonant frequency of the PR controller can be confirmed exactly with optimized performance. Based on an instantaneous power balance, the load power feed-forward is added to the power command to improve the anti-disturbance performance of the dc-link. Simulations based on MATLAB/Simulink and experimental results obtained from a 75kW prototype validate the correctness and effectiveness of the proposed control scheme.

• 정보처리학회논문지B
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• 제12B권6호
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• pp.647-654
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• 2005

본 논문은 디지털방송 서비스의 필수 기술 요소이고 디지털방송 전환과 밀접하게 관련 있는 PSIP 응용 기술인 디지털방송 표준 인터페이스로 표준화된 PMCP(Program Metadata Control Protocol) 인터페이스 규격과, 이를 이용하여 구현된 지상파/케이블 데이터방송 재전송 서비스를 위한 PSIP 변환기의 구조 및 주요 기능에 대해서 기술한다. 본 논문의 PSIP 변환기는 지상파/케이블 데이터방송 재전송 서비스 환경하에서 디지털 지상파 데이터방송 콘텐츠를 디지털 케이블 데이터방송에 재사용하여 데이터방송 콘텐츠 활용도를 높일 뿐만 아니라 실시간 채널 정보 변경 및 방송 프로그램 이벤트 정보 변경만으로 지상파 방송프로그램 안내 정보를 쉽게 재활용/관리할 수 있다. 또한 저장/관리된 방송프로그램 안내 정보를 ATSC T3/Sl에서 표준화한 PMCP 규격을 이용하여 XML형태로 케이블 시스템(OOB SI, Out Of Band Service Information)으로 전송하거나, MPEG-2 전송스트림 형태로 전송할 수도 있다.