• 조명전기설비학회논문지
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• 제22권12호
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• pp.29-35
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• 2008

본 논문에서는 부하전류의 급격한 변화에도 안정적인 출력진압을 얻기 위하여 강압쵸퍼의 전압제어 기를 개선하는 방법으로 부하전류 전향보상기를 제시하였다. 제시된 부하전류 전향보상기의 특성을 확인하기 위해 메이슨(Mason)의 이득공식을 이용하여 기존의 전압제어기가 포함된 전체 시스템의 전달함수와 부하전류 전향보상기가 추가된 전체 시스템의 전달함수를 각각 근궤적선도와 보드선도 상에서 비교하였다. 그 결과 시스템의 극점이 개선되고, 공진주파수에서의 첨두값의 크기 및 절점주파수의 위상여유가 양호한 것을 확인하였다. 따라서, 제시된 제어기법이 강압쵸퍼의 정상상태 및 동특성을 향상시키고 출력에 나타나는 외란에 의한 영향을 감소시킨 것을 확인할 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.240-249
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• 2018

Individual DC voltage balance problem is an inherent issue for cascaded H-bridge (CHB) based converter. When the CHB-based static synchronous compensator (STATCOM) is operating at zero current mode, the software-based individual DC voltage balancing control techniques may not work because of the infinitesimal output current. However, the different power losses of each cell would lead to the individual DC voltages unbalance. The uneven power losses on the local supplied cell-controllers (including the control circuit and drive circuit) would especially cause the divergence of individual DC voltages, due to their characteristic as constant power loads. To solve this problem, this paper proposes an adaptive voltage balancing module which is designed in the cell-controller board with small size and low cost circuits. It is controlled to make the power loss of the cell a constant resistance load, thus the DC voltages are balanced in zero current mode. Field test in a 10kV STATCOM confirms the performance of the proposed method.

• Journal of Power Electronics
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• 제19권4호
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• pp.869-880
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• 2019

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 학술대회 논문집 전문대학교육위원
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• pp.108-111
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• 2007

A novel voltage sag compensator with hi-directional DC/DC converter of Electric double layer capacitor is proposed. Recently, the double-layer capacitor which is drawn attention as a new energy storage element has a lot of advantage such as no maintenance, long lifetime and quick charge/discharge characteristics with large current. This DC/DC converter is used to control the charging current to the double-layer capacitor and also used to keep the DC link voltage constant for discharge of the double-layer capacitor. Therefore, the proposed DC/DC converter has the high-efficiency controller, dynamic compensator of voltage sag is driven by this converter. Finally, experimental results show the validity of the control scheme and the ability of the dynamic voltage compensator.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권3호
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• pp.204-210
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• 2000

This paper proposes a new reactive-power compensator composed of a soft-switching current-source inverter. The compensator consists of 3-Phase IGBT bridge, dc reactor, and a resonant circuit. The resonant circuit offers the IGBT bridge to have PWM operation with minimal switching losses. A theoretical analysis and computer simulation with Is-Spice were done to verify the operation of the proposed system. Also a acaled-model of the system was built and tested for verifying the feasibility of proposed system.

• 전력전자학회논문지
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• 제4권4호
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• pp.368-376
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• 1999

본 논문은, 대표적인 FACTS기기중의 하나인 싸이리스터제어 병렬보상기의 특성 연구를 수행한다. 이를 위하여 푸리에 공간에서 전력조류 조건을 만족하는 싸이리스터 점호각을 수치해석적으로 구하고, 그 계산 결과를 이용하여 정상상태 및 고조파 특성을 해석하였다. 그리고, Poincare Mapping 이론을 이용한 스위칭 주파수영역에서 안정도 해석과 EMTP 시뮬레이션을 이용한 시평면상에서 해석결과의 검증 및 여러 운전점에서 과도응답특성의 비교연구를 수행하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.351-353
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• 2004

In recent years, customers and power supplies are interested in power quality. Demands of customers are change from standard quality of distribution power system to various high quality of distribution power system. so, it is necessary to apply power quality compensator. in our project, we develop the UPQC(Unfied Power Quality Compensator of 45kVA which compensates power factor and voltage sag, interruption. it is very frequently occurred power quality $problems^{[1-3]}$ As a series and shunt compensator, UPQC consists of two inverters with common do link capacitor bank. It compensates the current quality in the shunt part and the voltage quality in the series part. In this paper, we present the design and control algorithm for 4SkVA UPQC system. As a control algorithm is implemented by digital controller, we consider sample-and-hold of signals. In this simulation, we use EMTDC/PSCAD V3.0 software which can simulate instantaneous voltage and current.

• 한국태양에너지학회 논문집
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• 제35권3호
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• pp.49-56
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• 2015

This paper presents a comparative operating characteristics of static var compensator(SVC) and static synchronous compensator(STATCOM) for compensating the reactive power in the Jeju power system. There are two kinds of reactive power compensating systems, which are active and passive system in the applications of the line commutated converter type high voltage direct current (LCC-HVDC). In the Jeju power system, two STATCOMs as active compensating system have been operating. Even though STATCOM has good performance compared with SVC, economical efficiency of former system is not good to the latter system. So, it is necessary to examine the performance and economical efficiency depend on the intention before appling the system. To compare the operating characteristics of two systems in the Jeju power system, simulations have been carried out for case studies that both of the HVDC system have transient state by using PSCAD/EMTDC program.

• 전기전자학회논문지
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• 제23권1호
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• pp.99-106
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• 2019

본 논문에서는 UPQC 시스템과 SVC를 결합한 새로운 형태의 보상장치를 제안하고자 한다. 기존의 UPQC는 직렬형 인버터, 병렬형 인버터, DC 링크로 구성되어 있어있으며 우수한 전력품질 보상 성능을 보이지만 높은 인버터 정격을 요구한다. 제안된 방식은 직렬형 인버터, 병렬형 인버터와 DC 링크 그리고 병렬형 인버터의 출력단에 결합된 SVC로 구성되어 있으며, 기존 UPQC에 비해 넓은 무효전력 보상 범위와 낮은 DC 링크 전압의 장점을 가지고 있다. 또한, SVC가 결합된 새로운 UPQC의 구성은 Matlab 시뮬레이션을 통해 성능을 검증하였다.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.270-279
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• 2018

This paper elucidates a hysteresis current controller for enhancing the performance of static synchronous compensator (STATCOM) using cascaded H-bridge multilevel inverter. Due to the rising power demand and growing conventional generation costs a new alternative in renewable energy source is gaining popularity and recognition. A five level single phase cascaded multilevel inverter with two separated dc sources, which is energized by photovoltaic - wind hybrid energy source. The voltages across the each dc source is balanced and standardized by the proposed hysteresis current controller. The performance of STATCOM is analyzed by connecting with grid connected system, under the steady state & dynamic state. To reduce the Total Harmonic Distortion (THD) and to improve the output voltage, closed loop hysteresis current control is achieved using PLL and PI controller. The performance of the proposed system is scrutinized through various simulation results using matlab/simulink and hardware results are also verified with simulation results.