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이택기,박현식 안성산업대학교 2000 論文集 Vol.32 No.-
This paper presents the performance of a active power filter(APF) system in unbalanced load. The unbalanced load leads to negative sequence of current, and this makes 120㎐ ripple in dc-link voltage and increase the rating of APF. Thus, the separation of negative sequence was performed in synchronous reference frame and it was controlled to flow into supply network. The validity of this scheme is investigated through experimental results for a prototype APF system rated 10kVA.
이택기,김한정 안성산업대학교 1997 論文集 Vol.29 No.2
This paper describes the Instantaneous Voltage Drop Compensator for instantaneous voltage drop. Instantaneous Voltage Drop Compensator has a capacitor bank as a compensation energy source. A serial type compensator has a shortage voltage compensation method. At a normal state, commercial voltage is supplied to a load. As voltage drops instantaneously the serial type compensator generates the shortage voltage by an inverter using the energy in capacitor bank and adds serially it to the input voltage. So, The load voltage remains constant. A 3Φ 20kva serial type Instantaneous Voltage Drop Compensator is made and also its controller is designed. The performance of the compensator is verified in experiments.
VOLTAGE COMPENSATOR PREPARING FOR INSTANTANEOUS POWER FAILURE
Taeck-Kie Lee,Soon-Bong Cho,Dong-Seok Hyun,Yong-Ha Hwang 전력전자학회 1992 ICPE(ISPE)논문집 Vol.1992 No.4
This paper discusses the principle and characteristics of the instantaneous voltage drop compensator, which protects damage from instantaneous voltage drop in systems such as a computer, a variable speed drive, a high voltage discharge-lamp, a magnet switch. When instantaneous voltage drop occurs, the control circuits rapidly detect it and then produce the output voltage the same as normal utility voltage. The instantaneous voltage drop compensator has the condenser- bank as energy storage component, so sysbem can be made small, ligth weight compared with UPS.<br/>
New Control Scheme for a Unified Power-Quality Compensator-Q With Minimum Active Power Injection
Woo Cheol Lee,Dong Myung Lee,Taeck Kie Lee IEEE 2010 IEEE transactions on power delivery Vol.25 No.2
<P>Voltage sags are one of the most frequently occurring power-quality problems challenging power systems today. The unified power-quality conditioner (UPQCs) is one of the major custom power solutions capable of mitigating the effect of supply voltage sags at the point of common coupling (PCC) or load. A UPQC-Q employs a control method in which the series compensator injects a voltage that leads the supply current by 90° so that the series compensator at steady state consumes no active power. However, the UPQC-Q has some disadvantages. First, there are limitations in rating when using UPQC-Q for series compensation. Second, there is a phase difference between the input and output voltage in proportion to the severity of voltage sags. As a result, it cannot offer effective compensation for voltage drops. This paper proposes a new control scheme for the UPQC-Q that offers minimum active power injection. The proposed power injection method takes into consideration the limitations of the rated voltage capacity of the series compensator, and the phase difference during voltage sag events. The validity of the proposed control scheme has been investigated by simulation and experimental results for less than 50% voltage sag conditions.</P>
288㎾급 중성 입자 빔용 Arc Power Supply 설계
이승교(Seung kyo Lee),이희준(Hee Jun Lee),신수철(Su Chul Shin),원충연(Chung Yuen Won),이택기(Taeck kie Lee),박선순(Sun Soon Park) 전력전자학회 2011 전력전자학술대회 논문집 Vol.2011 No.7
본 논문에서는 중성 입자 빔 장치용 아크 전원장치를 제안 하였다. 제안된 아크 전원장치는 저전압, 대전류의 특성을 가지고 있기 때문에 이를 고려하여 전력변환기가 설계되어야 하고, 시스템이 안정성이 보장되어야지만 사용할 수 있다. 따라서 본 시스템에서는 288㎾급 아크 전원장치를 설계하고 실험을 통하여 검증하였다.
Over Current Protection Schemes for Active Filters with Series Compensators
Lee, Woo-Cheol,Lee, Taeck-Kie The Korean Institute of Electrical Engineers 2004 KIEE International Transactions on Electrical Mach Vol.b4 No.3
This paper presents and analyses protection schemes for a series active compensator, which consists of a Unified Power Quality Conditioner (UPQC) or a hybrid active power filter. The proposed series active compensator operates as a high impedance "k(D)" for the fundamental components of the power frequency during over current conditions in the distribution system. Two control strategies are proposed in this paper. The first strategy detects the fundamental source current using the p-q theory. The second strategy detects the fundamental component of the load current in the Synchronous Reference Frame (SRF). When over currents occur in the power distribution system momentarily, the proposed schemes protect the series active compensator without the need for additional protection circuits, and achieves excellent transient response. The validity of the proposed protection schemes is investigated through simulation and compared with experimental results using a hybrid active power filter systems.
Lee, Woo-Cheol,Sung, Kook-Nam,Lee, Taeck-Kie The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.1
In this paper, a new sag and peak voltage detector is proposed for a single-phase inverter using delta square operation. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on d-q transformations using an all-pass filter (APF). The d-q transformation is typically used in the three-phase coordinate system. The APF generates a virtual q-axis voltage component with a 90° phase delay, but this virtual phase cannot reflect a sudden change in the grid voltage at the instant the voltage sag occurs. As a result, the peak value is drastically distorted, and it settles down slowly. A modified APF generates the virtual q-axis voltage component from the difference between the current and the previous values of the d-axis voltage component in the stationary reference frame. However, the modified APF cannot detect the voltage sag and peak value when the sag occurs around the zero crossing points such as 0° and 180°, because the difference voltage is not sufficient to detect the voltage sag. The proposed algorithm detects the sag voltage through all regions including the zero crossing voltage. Moreover, the exact voltage drop can be acquired by calculating the q-axis component that is proportional to the d-axis component. To verify the feasibility of the proposed system, the conventional and proposed methods are compared using simulations and experimental results.
Lee, Woo-Cheol,Lee, Taeck-Kie,Hyun, Dong-Seok The Korean Institute of Power Electronics 2001 JOURNAL OF POWER ELECTRONICS Vol.1 No.1
The performance analysis of a three-phase parallel active power filter that compensates PCC voltage and the unbalanced loads is presented in this paper. The proposed scheme in this paper employs a PWM voltage-source inverter and has two operation modes. Firstly, it operates as a conventional active filter with reactive power compensation when PCC voltage is within the 15% voltage drop range. Secondly, it operates as a voltage compensator when PCC voltage is not within the 15% voltage drop range. And both APF and voltage compensator compensate asymmetries caused by nonlinear loads. Finally, two methods of detecting the negative sequence are reviewed, and the validity of this scheme is investigated through analysis of simulation and experimental results for a prototype active power filter system rate at 10KVA.