• 한국산학기술학회논문지
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• 제19권4호
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• pp.117-122
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• 2018

대용량 3상 시스템 에어컨은 최근 들어 소비 전력 저감을 위해 인버터 회로를 포함하고 있다. 인버터 회로는 교류를 다이오드를 통해 정류하고 DC-link 전원부 콘덴서에 의해 평활된 직류를 사용한다. 이 때 평활에 사용되는 DC-link 전원부 콘덴서는 전압 리플, 전류 리플 조건을 만족하기 위해 전해 콘덴서가 일반적으로 사용된다. 콘덴서의 용량을 줄이게 되면 회로부의 크기 및 무게, 비용을 줄일 수 있게 된다. 본 논문에서는 최소점 추정 PPL(Phase Locked Loop) 위상 제어와 평균 전압 d축 전류제어 기법을 조합하여 입력 리플 전류를 약 90% 저감하는 알고리즘을 제안한다. 입력 리플 전류의 감소로 인해 DC-link 콘덴서의 전류 리플도 감소하므로 콘덴서의 용량을 줄일 수 있지만 전해 콘덴서의 경우 등가 직렬 저항(ESR : Equivalent Series Resistance)이 크기 때문에 발열로 인한 수명이 한계를 가진다. 본 논문에서는 전해 콘덴서 대신 DC-link 단에 전류 리플을 고려한 필름 콘덴서를 선정하는 방법을 제안한다. 필름 콘데서의 정전 용량 선정, 내압 선정, RMS(Root Mean Square) 전류 용량, RMS 전류 주파수 해석을 고려해 콘덴서의 용량을 선정할 경우 1680uF의 전해 콘덴서를 20uF로 용량을 낮추어 설계함으로써 전원부 콘덴서의 크기 및 무게, 비용을 줄였으며 전동기 구동을 통해 동작을 확인하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권10호
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• pp.544-554
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• 1999

Multi-level inverters are now receiving widespread interest form the industrial drives for high power variable speed applications. Especially, for the high power variable speed applications, a diode clamped multi-level inverter has been widely used. However, it has the inherent problem that the voltage of the link capacitors fluctuates. This paper describes a voltage control scheme effectively to suppress the DC-link potential fluctuation for a diode clamped four-level inverter. The current to flow from/into the each link capacitor is analyzed and the operation limit is obtained when a conventional SVPWM is used. To overcome the operation limit, a modified carrier-based SVPWM is proposed. Various simulation and experiment results are presented to verify the proposed voltage control scheme for DC-link voltage balancing.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.159-164
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• 1998

This paper proposes a SVPWM (space vector pulse width modulation) strategy for a multi-level voltage source inverter. This strategy is easily implemented as SPWM (sinusoidal pulse width modulation) and has the same DC-link voltage utilization as general SVPWM. The method to keep the voltage balancing of DC-link also is proposed by the analysis model of DC-link voltage fluctuation. The usefulness of the proposed SVPWM is verified through the simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1092-1093
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• 2007

본 논문은 DC-Link 전압가변에 의한 전구형 무전극 램프의 조광제어 특성을 분석한 결과 전력이 $20%{\sim}100%$ 제어 가능함을 실험적으로 밝혔다. DC-Link 전압가변은 벅 컨버터의 듀티를 제어하였으며, 전구형 무전극 램프의 조광제어 특성을 분석하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.71-72
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• 2016

전동기의 운전 영역을 확대하기 위해 부스트 컨버터를 이용하여 가변 DC link를 합성한다. 가변 DC link 구간에서는 스위칭 손실이 증가하기 때문에 스위칭 횟수를 줄이는 전략이 필요하다. 제안하는 Edge-Cutting Pulse Width Modulation(ECPWM)을 통해 스위칭 손실을 1/3로 절감하고, 최적의 고조파 특성을 갖는 직류단 전압의 크기를 결정한다. 이를 이용해 가변 직류단 전압 구간에서 인버터 손실을 감소시키며, Bolognani 과변조 방법을 적용해 안정적인 6-스텝으로의 절환까지 고려한다.

• 전력전자학회논문지
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• 제25권2호
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• pp.73-78
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• 2020

In this study, a novel reactive power control scheme is proposed to supply stable reactive power to the distribution line by compensating a ripple voltage of DC link. In a single-phase system, a magnitude of second harmonic is inevitably generated in the DC link voltage, and this phenomenon is further increased when the capacity of DC link capacitor decreases. Reactive power control was performed by controlling the d-axis current in the virtual synchronous reference frame, and the voltage control for maintaining the DC link voltage was implemented through the q-axis current control. The proposed method for compensating the ripple voltage was classified into three parts, which consist of the extraction unit of DC link voltage, high pass filter (HPF), and time delay unit. HPF removes an offset component of DC link voltage extracted from integral, and a time delay unit compensates the phase leading effect due to the HPF. The compensated DC voltage is used as feedback component of voltage control loop to supply stable reactive power. The performance of the proposed algorithm was verified through simulation and experiments. At DC link capacitance of 375 uF, the magnitude of ripple voltage decreased to 8 Vpp from 74 Vpp in the voltage control loop, and the total harmonic distortion of the current was improved.

• 전력전자학회논문지
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• 제7권3호
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• pp.244-252
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• 2002

본 논문에서는 가변속 교류 전동기 구동에 많이 사용되는 3상 ac/dc/ac PWM 컨버터 시스템에서의 직류링크 리플전류를 주파수 영역에서 해석하고자 한다. 고조파 전류는 컨버터의 스위칭함수와 지수함수 형태의 퓨리에 급수 전개를 이용하여 분석된다. 전원측 컨버터와 부하측 인버터의 스위칭 주기간의 변위각과 비동기 PW이 리플전류에 미치는 영향도 고찰된다. 해석 결과가 PSIM을 이용한 시뮬레이션으로부터 나온 고조파 스펙트럼과 잘 일치함을 확인한다 제시된 해석기법은 PWM의 원리에 대한 이해를 돕고, 해석 결과는 직류링크 커패시터의 고주파 등가 모델링에 이용된다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2335-2343
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• 2018

This paper proposes an optimal damping control algorithm of the DTI (Direct Two-level Inverter) to miniaturize and reduce the weight of auxiliary power supply for railway vehicles. The conventional auxiliary power supply for railway vehicles uses a DC-DC converter to maintain the inverter input power from the line voltage smoothly. The proposed topology does not use a DC-DC converter for reducing of manufacturing and maintenance costs. It also proposes a DTI topology removed damping resistors that generate ground signal noise in a certain period. At this time, a resonance phenomenon of DC-link voltage occurs due to variation of the inductive load, and a method of controlling the resonance phenomenon of DC-link voltage is required. In order to suppress the resonance phenomenon of the DC-link voltage, at a point before resonance occurs, this paper introduces an algorithm to suppress the resonance phenomenon of DC-link voltage by compensating the resonance component of the q axis voltage of the synchronous reference frame. The proposed algorithm verifies the effect through simulation and experiment.

• 전기학회논문지
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• 제64권3호
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• pp.399-404
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• 2015

This paper presents the DC voltage control method in DC link of High Voltage Direct Current(HVDC) for an offshore wind farm in Low Voltage Ride Through(LVRT) situation. Wind generators in an offshore wind farm are connected to onshore network via HVDC transmission. Due to LVRT control of grid side inverter in HVDC, power imbalancing in DC link is generated and this consequentially causes rising of DC voltage. A de-loading scheme is one of the method to protect the wind power system DC link capacitors from over voltage. But the flaw of this method is slow control response time and that it needs long recovery time to pre-fault condition after fault clear. Thus, this paper proposes improved de-loading method and we analyze control performance for DC voltage in LVRT control of HVDC for an offshore wind farm.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.560-564
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• 2003

This paper proposes a simple control strategy based on the discontinuous PWM(DPWM) to balance the DC-link voltage of three-level Neutral-Point-Clamped(WPC) inverters at low modulation index. New DPWM methods in multi-level inverter are also introduced. The proposed DPWM method changes the path and duration to flow the neutral point current out of or into neutral point of the DC-link and it makes the overall fluctuation of the DC-link voltage zero during a sampling time of reference voltage vector. Therefore, the voltage of the DC-link can be balanced fairly well and also the voltage ripple of the DC-link is reduced significantly. Moreover, comparing with conventional methods, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by experiment