• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1096-1098
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• 2003

In this paper, the control algorithm and control methods for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the 3-phase 4-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and odd multiples of $3^{rd}$($9^{th}$, $15^{th}$, etc.) are termed as triple and zero sequence components that do not cancel each other in the system neutral. As a result, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control scheme for a series hybrid active system. This series active power filter acts not only as a harmonic compensator but also as a harmonic isolator. Hence the required rating of the series active filter is much smaller than that of a conventional shunt active filter. However, the performance of the combined system is greatly influenced by the filtering algorithm employed in the active power filter. This paper proposes a series active power filter scheme based on performance function. Some experiments was executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.735-738
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• 2000

In this paper we propose a series active power filter and a simple calculation method acquiring the reference voltage. A series active power filter is suitable to suppress harmonics produced by voltage type harmonic source such as a diode rectifier with filter capacitor on the DC side The proposed series active power filter system is applied to 3-phase 3-wire power system including the voltage type harmonic source. Experimental result obtained from a laboratory model are shown to verify the viability and effectiveness of the proposed system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.716-723
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• 2007

This paper suggests of a 3-phase 3-wire unified active power filter. The system is composed of a series active power filter and a parallel active power filter. The proposed series active power filter compensating unbalance source voltage and current harmonics of the parallel active power filter improves power factor. The proposed algorithm which improves for power factor and harmonic reduction are calculated by the performance function, and which compensates for the unbalanced source voltage is calculated based on the symmetrical component analysis. We composed a combined system of the series active power filter and parallel active power filter to confirm a validity of the proposed control methods. The effectiveness of the proposed algorithm is confirmed by the experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.5
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• pp.221-228
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• 2001

In this paper, a new control algorithm of series active power filter is proposed to reduce harmonic generated from nonlinear load in power system. In conventional control algorithm, harmonic current must be calculated firstly, and then compensation voltage was calculated by using the results but the proposed control algorithm can calculate compensation voltage directly. Compensating principle of proposed control algorithm is presented in detail. A combined system of series active filter and passive filter is composed in order to experiment. Experiment was carried out to verify proposed control algorithm of series active filter and experimental results are analyzed.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.3
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• pp.258-264
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• 2001

In this paper, a new control strategy of a series active power filter suing direct compensating voltage extraction method is proposed. The proposed series active power filter and shunt passive filters are used 3-phase 3-wire power system with nonlinear load. The series active power filter complements drawbacks of the shunt passive filter and contributes to a source side harmonic reduction. We can extract the compensating voltage of the series active power filter using performance function without phase transformations. Therefore, the calculating time is short and the control method is simple compared with conventional methods. Experimental results verify that the system using the proposed method appears a good performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.88-93
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• 2016

LCL filters are widely used in high-order harmonics attenuation of output currents in grid-connected inverters. However, output currents of grid-connected inverters with LCL filters can become unstable because of the resonance of the filters. Given that the characteristics of output currents in inverters mostly depend on filter performance, the exact analysis of filters by considering parasitic components is necessary for both harmonics attenuation and current control. LCL filters have three or four parasitic components: the series and/or parallel resistance of the filter capacitor and the series resistance of the two filter inductors. Most studies on LCL filters have focused on the parasitic components of the filter capacitor. Although several studies have addressed the parasitic components of the filter inductor at the inverter side, no study has yet investigated the concurrent effects of series resistance in both filter inductors in detail. This paper analyzes LCL filters by considering series resistance in both filter inductors; it proposes an active damping method based on the virtual series resistance of LCL filters. The performance of the proposed active damping is then verified through both simulation and experiment using Hardware-in-the-Loop Simulator(HILS).

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.196-199
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• 2001

This paper deals with current harmonics and unbalanced source voltages compensation using combined filter system. Filter system consists of a series active filter and parallel passive filters. Passive filters were a traditional method to compensate current harmonics, so those were installed in power system widely. The active filter can be a substitution to improve filtering characteristics and complement drawbacks of the passive filter. The combined system of the active power filter and passive filter can has a better compensation performances and economical goods. The series type active power filter injects compensation voltage into power system by transformers. It's compensation principle is able to applicate for voltage compensation. A new control algorithm for series active filter to compensate current harmonics and unbalanced source voltages is proposed. In the proposed algorithm, a compensation voltage for harmonic reduction is calculated directly by instantaneous reactive power theory, and a compensation voltage for unbalanced source voltage is calculated in based on a synchronous reference frame. By experiments, we show validity of proposed compensation method.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.571-575
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• 2001

A protection scheme for hybrid active power filters, which is combined shunt passive filter and small rated series active filter, is presented and analyzed in this paper. The proposed series active power filter operated as a high impedance 'k($\Omega$)' to the fundamental component when over current occurs in the power distribution system, and three control strategies are proposed in this paper. The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame (SRF) and the third is the method by detecting the input voltage. When the over current occurs in the power distribution system, the proposed scheme protects the series active power filter without additional protection circuits. The validity of proposed protection scheme is investigated through experimental result for the prototype hybrid active power filter system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.12
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• pp.714-722
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• 2002

This paper presents a control algorithm for a 3-phase 4-wire series active Power filter. This control algorithm compensates harmonics, input power factor and neutral line currents which are generated by balanced or unbalanced nonlinear loads. The advantage of this control algorithm is direct extraction of compensation voltage references. Therefore, the calculation time is shortened and the performance of the series active power filter is improved. The compensation principle of the proposed control algorithm is presented in detail. A 3KVA laboratory prototype of the three-phase four-wire series active power filter was built and experiments have been carried out. Experimental results are shown to verify the effectiveness of the proposed control algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.78-89
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• 2015

Conventional EMI filters have tried to use an active EMI filter as a series by the series connection of two EMI filters for CM and DM noise. However, the proposed filter is formed into one circuit by using the active EMI filter which is able to filter CM and DM noise components together. As a result, the active EMI filter showed the outstanding quality in mass and volume under 50% and electric characteristics have been compared to the passive EMI filter in approximately 150kHz~10MHz. Furthermore, the proposed circuit has simple circuit components by comparing with the series EMI filters, and electrical characteristics are similar. The noise have been attenuated to maximum 20dBuV.