• Journal of Power Electronics
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• 제15권4호
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• pp.1093-1104
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• 2015

A standard repetitive controller (RC) is theoretically able to replace a bank of resonant controllers in harmonic signals tracking applications. However, the traditional RC has some drawbacks such as a poor dynamic response and a complex structure to compensate grid frequency deviations for an effective unified power quality conditioner (UPQC) control scheme. In order to solve these problems, an improved RC with an outstanding dynamic response and a simplified grid frequency adaptive scheme is proposed for UPQC control systems in this paper. The control strategy developed for the UPQC has delay time, i.e., one-sixth of a fundamental period (T_p/6), repetitive controllers. As a result, the UPQC system can provide a fast dynamic response along with good compensation performance under both nonlinear and unbalanced loads. Furthermore, to guarantee the excellent performance of the UPQC under grid frequency deviations, a grid frequency adaptive scheme was developed for the RC using a simple first order Padé's approximation. When compared with other approaches, the proposed control method is simpler in structure and requires little computing time. Moreover, the entire control strategy can be easily implemented with a low-cost DSP. The effectiveness of the proposed control method is verified through various experimental tests.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.305-307
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• 2001

This paper deals with single-phase unified power quality conditioner(UPQC), which aims at the integration of series-active and shunt-active filter. The series filter is used to compensate for the voltage distortions and the shunt filter is used to provide reactive power and counteract the harmonic current injected by the load. Also, the voltage of the DC link capacitor is controlled to a desired value by the shunt active filter. The performance of UPQC under load nonlinearities conditions is investigated using simulation as well as experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 추계학술대회
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• pp.142-143
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• 2019

본 논문은 계통과 연계하여 운전하거나 계통사고시나 의도적인 단독 운전이 필요한 경우 계통과 분리하여 운전하기 위한 UPQC(Unified Power Quality Conditioner)를 기반으로 하는 인버터를 제안한다. UPQC 기반의 인버터는 계통 연계시에 과전압, 저전압 등의 계통 전압의 변동이 발생 했을 시 이를 보상하여 부하에 전달되는 전력의 품질을 유지 할수 있다. UPQC의 개념에 대하여 설명하고, 계통 연계시의 전압 보상, 단독 운전시의 시퀀스에 대하여 설명하고, 이를 시뮬레이션을 통해 검증한다.

• 조명전기설비학회논문지
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• 제16권5호
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• pp.22-28
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• 2002

본 논문에서는 직렬형, 병렬형 능동전력필터로 구성되어 있는 통합전력품질 제어기(UPQC)의 과전류에 대한 보호기법이 제시되며, 해석된다. 제안된 과전류 보호기법은 직렬형 능동전력필터에 과전류의 기본파 성분에 대해서고 임피던스를 갖는 기능을 부여함으로써 구현하였으며, 세 가지 방법을 제시하였다. 첫 번째 방법은 p-q이론을 이용하여 기본파 전원전류를 검출하여 보호하는 방법, 두 번째 방법은 동기 좌표계에서 부하전류의 기본파 성분을 검출하여 보호하는 방법, 세 번째 방법은 입력전압을 검출하여 보호하는 방법이다. 전원계통에서 과전류가 흘렀을 경우 제안된 방법들은 UPQC에 부가적인 회로 없이 보호해 줄 수 있다. 제안된 방법의 타당성은 시뮬레이션 결과를 통하여 입증된다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권4호
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• pp.374-381
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• 2005

The ability to provide quality power has become a significant issue in power systems. The main causes of poor power quality are harmonic currents, poor power factor, supply-voltage variations, etc. A technique of achieving both active current distortion compensation, power factor correction and also mitigating the supply-voltage variation (sag or swell) at the load side is presented in this paper. The operation and rating issues of the proposed Single-phase Unified Power Quality Conditioner are also highlighted. To reduce the total cost while simultaneously increasing the performance, the system is fully digitally controlled using the fixed-point TMS320F240 digital signal processor. The performances of the UPQC, which is composed by shunt and series PWM controlled-converters, have been verified on a laboratory prototype.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1352-1364
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• 2013

This paper describes a novel structure for single phase Unified Power Quality Conditioner-Distributed Generation (UPQC-DG) with direct grid connected DC-AC converter for low DC output DG systems which can be used not only for compensation of power quality problems but also for supplying of load power partly. This converter has been composed of one full-bridge inverter, one three winding high frequency transformer with galvanic isolation and two cycloconverters. Proper control based on Input Output feedback Linearization is used to tracking the reference signals. The simulation and experimental results are presented to confirm the validity of the proposed approach.

• Journal of Power Electronics
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• 제19권2호
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• pp.519-528
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• 2019

The unified power quality conditioner (UPQC) is an effective custom power device that is used at the point of common coupling to protect loads from voltage and current-related PQ issues. Currently, most researchers have studied series unit and parallel unit models and an idealized transformer model. However, the interactions of the series and parallel converters in AC-link are difficult to analyze. This study utilizes an equivalent transformer model to accomplish an electric connection of series and parallel converters in the AC-link and to establishes a precise unified mathematical model of the UPQC. The strong coupling interactions of series and parallel units are analyzed, and they show a remarkable dependence on the excitation impedance of transformers. Afterward, a feed-forward decoupling method based on a unified model that contains the uncertainty components of the load impedance is applied. Thus, this study presents an adaptive method to estimate load impedance. Furthermore, simulation and experimental results verify the accuracy of the proposed modeling and decoupling algorithm.

• 한국철도학회논문집
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• 제12권5호
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• pp.694-699
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• 2009

교류 전기철도 급전시스템의 전압, 전류의 왜곡 및 전압 sag과 무효전력을 보상하기 위한 단상 UPQC의 동기좌표계를 이용한 제어 방법을 제안한다. 단상 UPQC의 동기좌표계를 이용한 제어를 통해 단상인버터 형태인 UPQC의 직렬보상기와 병렬보상기를 순시적으로 제어한다. 시뮬레이션을 통해 단상 UPQC를 이용하여 비선형 단상 부하인 차량으로 인해 급전시스템에 생길 수 있는 전압, 전류의 왜곡 및 전압 sag과 무효전력의 보상이 가능함을 증명하고, 단상 UPQC의 동기좌표계를 이용한 제어 방법이 타당함을 확인한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.543-547
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• 2001

A protection scheme for Unified Power Quality Conditioner (UPQC) is presented and analyzed in this paper. The proposed UPQC has the series active power filter operated as a high impedance k($\Omega$) to the fundamentals when short-circuit faults occur 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 short-circuit fault occur in the power distribution system, the proposed scheme protects the UPQC without additional protection circuits. The validity of proposed protection scheme is investigated through simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 전문대학교육위원
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• pp.93-96
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• 2005

This paper describes experimental analysis of UPQC, which is composed of cascaded H-bridges and single-phase multi-winding transformers. The operational characteristic was analyzed through experimental works with a scaled model, and simulations with PSCAD/EMTDC. The UPQC proposed in this paper can be directly connected to the distribution line without series injection transformers. It has flexibility to expand the operation voltage by increasing the number of H-bridge modules. The analysis results can be utilized to design the actual UPQC system applicable for the actual distribution system.