• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.494_495
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• 2009

This paper presents a study of DFIG wind power generation system for real-time simulation. For real-time simulation, the real-time digital simulator (RTDS) and its user friendly interface simulation software (RSCAD) are used. 2.2MW grid-connected variable speed DFIG wind power generation system is modeled and analyzed in this study. Stator-flux oriented vector control scheme is applied to stator, rotor side converter control, and back-to-back PWM converters are implemented for the decoupled control. The real-wind speed signal extracted by an anemometer is used for realistic and accurate simulation analysis. Block diagrams for DFIG and control scheme of stator, rotor-side are introduced. Real-time simulation cases are carried out and analyzed for the validity of this work.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.205-212
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• 2012

This paper proposes the fuzzy logic based variable step-size MPPT (Maximum Power Point Tracking) method for the stability at the steady state and the improvement of the transient response in the wind power system. If the change value of duty ratio is set on stability of the steady state, MPPT control traces to maximum power point slowly. And if the change value is set on improvement of the transient response, the system output oscillates at the maximum power point. By adjusting the step size with fuzzy logic, it can be improved the MPPT response speed and stability at steady state when MPPT control is performed to track the maximum power point. The effectiveness of the proposed method has been verified by simulations and experimental results.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.11-12
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• 2012

최근 풍력 발전이 시스템이 전체 전력망에서 차지하는 비중이 커짐에 따라 세계 각국에서는 LVRT(Low Voltage Ride Through) 규정을 제정하여 계통 연계된 풍력 발전 시스템이 전력망의 안정화에 부정적 영향을 미치지 않도록 하고 있다. 계통 전압 사고 상황에서 LVRT 규정을 만족 시키게 되면 발전기에서 발생된 유효전력과 계통으로 전달되는 유효전력 사이의 불균형으로 직류 링크전압이 상승하게 된다. 본 논문은 이러한 상황에서 계통연계 컨버터의 직류 링크전압을 일정하게 제어하는 알고리즘을 제안한다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1064-1065
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• 2015

단상 계통 연계형 전력 변환기에서 계통과 연계하기 위해서는 계통의 위상 정보를 정확히 측정하여 전력 변환기의 출력 주파수와 위상이 동일한 상태로 전류가 공급 되도록 해야 한다. 본 논문에서는 단상 d-q 좌표 변환 기법을 통한 위상 동기화 기법을 적용하여 왜곡된 계통전압이 d축 전압에 야기 되는 에러 성분을 최소화 하는 보상 기법을 제안한다. 제안된 기법은 동기 d축 전압을 일정한 주기로 적분하여 에러 성분을 최소화 한 후, PI제어를 통해 d축 전압을 0으로 수렴하게 하는 기법이다. 제안된 기법은 추가적인 하드웨어를 요구하지 않는다. 본 논문의 타당성을 검증하기 위해 3[kW]급 단상 계통 연계형 전력변환기 시작품을 제작하고 실험을 통해 증명하였다.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.551-554
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• 2002

This paper describes a new interactive inverter between a photovoltaic(PV) array and single-phase utility that avoid the bulky input (60Hz) transformer on the AC side. The interface employs a pwm boost converter on the DC side followed by a pwm current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly in phase at all time. The circuit also has the advantage of requiring fewer switching device than high-frequency link system. This paper describes modeling of PV array and new system topology. Simulation results on the performance of the connection are also presented.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.555-558
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• 2002

The general ways of the anti-islanding can be classified into the active method and passive method. The passive method which use only the voltage information when power failure occurs has much possibility of the wrong detection. And the active method detects the change of the voltage frequency as instantaneously changing the frequency of the inverter output current. Therefore, in this paper, the method to inject arbitrary order harmonics into controlled current is proposed. In this method islanding can be detected by measuring the amount of load voltage of injected harmonics order. And as a current control method predictive control method is used, which make actual current accurately to track reference current by Instantaneously computing converter output voltage and has fast response in transient state. This parer proposed method was verified by simulation.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.385-386
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• 2010

최근 국내 외의 태양광 발전 시스템은 산업화 대용량화 되어가는 추세이다. 태양광 시스템의 인버터에는 태양전지 모듈의 조합에 따라 MIC(Module-Integrated Converter), 스트링, 멀티 스트링, 센트럴, 멀티 센트럴 인버터로 분류된다. 제한하는 멀티 센트럴 방식의 인버터는 상황에 따른 특정 인버터만 구동하거나, 인버터를 개별적으로 운전하여 태양광 발전설비에 대한 시스템의 효율을 높일 수 있다. 또한 인버터의 가동 시간을 동일하게 운전하여 인버터의 사용 수명을 연장하고, 하나의 인버터 고장이나 유지 보수 시 다른 인버터를 높은 에너지로 발전할 수 있어 에너지 손실을 줄일 수 있다는 장점을 갖는다. 본 논문은 PV 어레이와 인버터를 모델링하였고, 제안하는 멀티 센트럴 인버터의 상황별 동작 모드에 따른 시퀀스 제어 기법을 적용하여 시뮬레이션과 실험을 통하여 그 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.291-292
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• 2010

The main purpose of this study is to design and develop the grid connected 4kW photovoltatic PCS(Power Conditioning System) targeting for Japanese market. To make this task, the development of DC to DC converter, one phase inverter and EMI filters, and the research on connection between inverter and utility line are made. The developed 4kW PCS has fully carried out performance verifications and evaluation works and acquired the JET(Japan Electrical Safety & Environment Technology Laboratories) certification for safety and performance.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.326-332
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• 2018

In this paper, the design process and the control method of the power conversion system (PCS) that consists of a bidirectional DC-DC converter and a 3-level T-type inverter for an energy storage system is presented. Especially the design method of the output LCL filter for a 3-lvel T-type inverter without complex mathematical process are proposed. The validity of the control method and design process in this paper are verified through simulation and experimental analysis.

• Journal of Power Electronics
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• v.7 no.3
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• pp.203-212
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• 2007

In this paper, a proposed approach to improve the power factor of three-phase rectifiers and to stabilize the output voltage against load change is presented. The elements of the given control strategy are small size, low cost, high performance, and simplicity. The proposed control strategy of switches is based on a prototype of three bi-directional switched consisting of four diodes and one IGBT. A control technique and operational procedure are also developed, both theoretically and experimentally. The experimental results clearly verify the theoretical analysis from the prototype connected to grid unity.