• 한국산업정보학회논문지
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• 제21권3호
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• pp.29-33
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• 2016

청정에너지 발전설비의 요구가 늘면서 태양광, 풍력, 연료 전지 등의 분산전원 개발이 급속도로 증가하고 있다. 반면에 이러한 증가로 인하여 배전시스템은 복잡해지고 있으며 무효전력으로 인한 역률 저감, 불평형 부하에 의한 불평형 전류 등의 문제점을 가지고 있다. 이러한 문제점들을 해결하기 위하여 본 논문에서는 태양광용 3상 4선 타입의 전력변환장치에 무효전력, 불평형 전류를 보상하는 알고리즘을 적용하였다. 제안한 태양광 전력변환장치는 기본 출력동작 뿐만 아니라 계통 전력 품질의 저해요소들에 대해서 보상이 가능하며 PSCAD/EMTDC를 이용한 시뮬레이션을 통하여 그 성능을 검증하였다.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2227-2236
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• 2017

In order to solve the neutral-point voltage fluctuation problem of three-phase three-level T-type inverters (TPTLTIs), the unbalance characteristics of capacitor voltages under different switching states and the mechanism of neutral-point voltage fluctuation are revealed. Based on the mathematical model of a TPTLTI, a feed-forward voltage balancing control strategy of DC-link capacitor voltages error is proposed. The strategy generates a DC bias voltage using a capacitor voltage loop with a proportional integral (PI) controller. The proposed strategy can suppress the neutral-point voltage fluctuation effectively and improve the quality of output currents. The correctness of the theoretical analysis is verified through simulations. An experimental prototype of a TPTLTI based on Digital Signal Processor (DSP) is built. The feasibility and effectiveness of the proposed strategy is verified through experiment. The results from simulations and experiment match very well.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.375-376
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• 2020

계통의 전류 불평형은 고장 또는 단상 부하에 의해 발생한다. 불평형 전류는 계통의 손실을 증대시키고, 전압 불평형으로 나타날 수 있어 계통의 안정성 문제로 이어진다. 본 논문은 계통 연계형 PCS를 통해 계통 불평형 전류를 보상하여 계통의 손실을 낮추고 안정성을 높이는 불평형 전류제어 알고리즘을 제안한다. 제안한 방법은 시뮬레이션을 통해 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2801-2803
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• 1999

An unified controller for emergency generator is presented to control AVR and Governor and l00kVA power conditioner. This controller is operated to compensate current harmonics and asymmetries caused by nonlinear load and unbalance loads. The power conditioner shapes the source current sinusoidal in phase with source voltage and allows the generator to maximum power even to the single phase load. Also this power conditioner allows that three phase generator synchronizes with single phase main source and load sharing. An l00kVA generator system was built and the unified controller is realized with DSP(TMS320C32PCMA). Experimental results for many load conditions are presented to verify the performance of the unified controller.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.345-351
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• 1997

In this paper, controller for PWM converter considering unsymetrical input voltage is designed and current controller using LQ controller with conditional integrator is proposed. And the proposed current controller is compared with other current controller-predictive controller, decoupling PI controller. As simulation results, LQ controller with Conditional Integrator shows the improved performance for DC link voltage regulation through transient test of load variation. And when unsymeritrical input voltage is applied to converter with conventional current controller considering only symetrical input voltage, input current is distorted but it is showed that current controller considering unsymetrical input has robust control characteristics under phase voltage unbalance.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.524-526
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• 2011

This paper focuses on study on PWM converter control under unbalanced network condition. Voltage unbalance in a three-phase system causes the performance deterioration by producing 120 Hz voltage ripples in the DC link and 120 Hz ripple in reactive power. To eliminate the ripples, both positive and negative sequence currents should be controlled simultaneously. In this paper four PI controllers on synchronous reference frame is implemented to control D and Q currents in both positive and negative sequence. Positive and negative sequence signal extraction is done using delay signal cancellation method. Simulation results show satisfactory performance in suppressing 120 Hz ripples.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.1649-1654
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• 2009

Induction motors widely use in industry because structure is simple and hard and cost is generally cheap and they are easy to control. In recently, because of saving steel, ventilation and benefit of frame fixing, rectangular core type induction motors use in industry more and more. This paper presents current characteristic according to stator core cutting degree in three-phase induction motor (IM) with rectangular stator core. According to stator cutting degree, magnetic saturation and paths of flux are changed. Because of these situations, phase currents are unbalance and are produced harmonic components and they cause decrease of efficiency. We analyze each $10^{\circ}$ from $0^{\circ}$ to $30^{\circ}$ using 2-D finite element analysis (FEA). Optimal stator cutting core degree selection supplies stable currents and efficiency improvement. In this paper, loss separation test was executed by IEEE Std. 112-98 Method B and we compare with the result of loss separation by Simulation using FEM and by Experiment.

• Journal of Power Electronics
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• 제13권3호
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• pp.469-478
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• 2013

This paper proposes a novel scheme for the current controller for the grid-side converter (GSC) of permanent-magnet synchronous generator (PMSG) wind turbines to eliminate the high-order harmonics in the grid currents under grid voltage disturbances. The voltage unbalance and harmonics in three-phase systems cause grid current distortions. In order to mitigate the input current distortions, multi-loop current controllers are applied, where the positive-sequence component is regulated by proportional-integral (PI) controllers, and the negative-sequence and high-order harmonic components are regulated by proportional-resonance (PR) controllers. For extracting the positive/negative-sequence and harmonic components of the grid voltages and currents without a phase delay or magnitude reduction, composite observers are applied, which give faster and more precise estimation results. In addition, an active damping method using PR controllers to damp the grid current component of the resonant frequency is employed to improve the operating stability of VSCs with inductor-capacitor-inductor (LCL) filters. The validity of the proposed method is verified by simulation and experimental results.

• 전력전자학회논문지
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• 제6권6호
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• pp.514-524
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• 2001

종전의 평균전력이론은 3상 불평형과 같은 전원전압 조건에 따라 능동전력필터의 보상기준전류가 결정적으로 영향을 받는 문제점이 있다. 이와 같은 불평형된 능동전력 필터의 보상전류는 결과적으로 불평형이 되는 원인이 된다. 본 연구에서는 불평형 전원 하에서도 유효전력과 기본파 무효전력의 동기 검출법에 입각하여 비선형 부하전류의 유효성분과 기본파 무효성분 그리고 왜형 성분을 각각 독립적으로 분해가 가능한 평균전력 이론을 제시하였다. 제안된 이론은 간단한 평균전력 이론을 기반으로 하고 잇기 때문에 우선 이해사기 쉽고 구현이 간단하다는 장점이 있다. 본 연구 에서는 고속의 DSP(digital signal processor)에 의하여 이와 같은 문제을 어느정 도 해결할 수있었다. 제안된 방법의 타당성을 입증하기 위해서 TMS320C31-DSP기반의 전력분석 시스템을 제작하였다. b상 전압이 15% 불평형된 3상 3전 전원하에서 시뮬레이션 및 실험을 수행한 결과 종전의 방법에 비하여 제안된 알고리즘의 유용성을 입증할수 있었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.316-317
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• 2018

This paper propse the DC link capacitor voltage balancing control for three level neutral point clamped converter with harmonic component injection method. The injcetion voltage consists of harmonic component and DC link capacitor voltage difference. Theoretical analysis is provided to balance the DC link voltage, and it shows that harmonic component compensates the unbalanced condition between the capacitors. Both simulations and experiments are carried out to show that the voltage unbalance have been decreased by the proposed method.