• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.808-815
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• 2001

The three-phase diode rectifier with a capacitive filter is highly sensitive to line voltage unbalance, and may cause significantly unbalanced line currents even under slightly unbalanced voltage condition. This paper presents an analysis of this 'unbalance amplification' effect for an ideal rectifier circuit without ac-and dc-side inductors. The voltage unbalance is modeled by introducing a deviation voltage superimposed on balanced three-phase line voltages. With proper approximations, closed-form expressions for symmetrical components of the line current and current unbalance factor are derived in terms of the voltage unbalance factor, filter reactance, and load current. The validity of analytical predictions is confirmed by simulation.

• Journal of Power Electronics
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• 제12권4호
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• pp.587-594
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• 2012

When a PWM rectifier has a low DC-link voltage during startup, the output voltage vector cannot be high enough to regulate the input current. This lack of a PWM rectifier output voltage vector can cause an unregulated inrush current when the rectifier operation starts. This paper presents a PWM rectifier start-up current control algorithm for when it starts operation with a lower DC-link voltage than unloaded condition case. To avoid the unregulated inrush current caused by a lack of DC-link voltage, the proposed control scheme regulates the one phase current with one switch chopping and it generates the current command considering the uncontrolled current magnitude information, which is calculated in advance. Simulation and experiment results support the validity of the proposed method.

• 전력전자학회논문지
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• 제6권4호
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• pp.38-38
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• 2001

The three-phase diode rectifier with capacitive filter is highly sensitive to line voltage unbalance. Because of its inherent nonlinear characteristics, small line voltage unbalance may cause highly unbalanced line current, causing detrimental effects on power quality. This paper presents a theoretical basis on this ′unbalance amplification effect′ and derives an analytical model of line current characteristics under unbalanced line voltage condition for various modes of operation. The results provide a basic guideline for optimal design of a three-phase diode rectifier with capacitive filter that is most commonly used for interfacing various power conversion equipments to power lines.

• 전력전자학회논문지
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• 제6권4호
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• pp.348-361
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• 2001

커패시터 필터를 갖는 3 상 다이오드 정류회로는 입력전압의 불평형에 매우 민감한 특성을 가지고 있다. 이러한 정류회로는 그 동작의 비선형성으로 인해 작은 전압의 불평형에도 입력전류에는 큰 불평형이 나타날 수 있으며 이로 인해 전원품질에 악영향을 미친다. 본 논문에서는 이러한 불평형 증폭특성을 이론적으로 규명하고 불평형 정도에 따른 정류회로의 동작모드에 따라 재반 입력전류의 특성에 대한 모델을 도출하였다. 본 논문의 결과는 각종 전력변환 장치의 입력부로서 널리 사용되는 커패시터 필터형 3상 다이오드 정류회로를 최적 설계하는 데에 중요한 해석적 기초를 제공하고 있다.

• Journal of Power Electronics
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• 제19권1호
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• pp.288-295
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• 2019

Rectifiers are widely used in industrial applications. Although detailed models of rectifiers are usually used to evaluate their performance, they are complex and time-consuming. Therefore, the Average Value Model (AVM) has been introduced to meet the demand for a simple and accurate model. This type of rectifier modeling can be used to simplify the simulations of large systems. The AVM of diode rectifiers has been an area of interest for many electrical engineers. However, healthy diode rectifiers are only considered for average value modeling. By contrast, faults occur frequently on diodes, which eventually cause the diodes to open-circuit. Therefore, it is essential to model bridge rectifiers under this faulty condition. Indeed, conventional AVMs are not appropriate or accurate for faulty rectifiers. In addition, they are significantly different in modeling. In this paper, a novel application of the parametric average value of a three-phase line-commutated rectifier is proposed in which one diode of the rectifier is considered open-circuited. In order to evaluate the proposed AVM, it is compared with experimental and simulation results for the application of a brushless synchronous generator field. The results clearly demonstrate the accuracy of the proposed model.

• 전력전자학회논문지
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• 제4권3호
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• pp.304-309
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• 1999

본 논문에서는 새로운 24펄스 다이오드 정류기 시스템을 제안한다. 제안하는 다이오드 정류기 시스템은 기존의 직렬형 12펄스 다이오드 정류기에 수동의 보조회로를 추가함으로서 구성되어지고, 입력전류는 제 22차까지의 고조파가 제거되어 거의 정현파에 가까운 전류 파형을 얻는다. 또한, 출력 전압은 n=24k, k=1,2,3... 의 고조파 성분을 갖는 24펄스 특성를 나타낸다. 더욱이, 이 보조회로의 용량은 출력용량에 비하여 매우 작으며, 능동 스위칭소자를 사용하지 않으므로 외란에 강하고 구현이 간단하다. 따라서, 본 방식은 중·대용량급의 고전압 비제어(uncontrolled) 직류전원이 필요한 인버터나 무정전 전원장치등의 앞단에서 입력고조파의 저감에 경제적이고 효율적이다. 220V, 3KVA 정류기 시스템의 실험을 통하여 제안한 시스템의 타당성을 검증하였다.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.822-828
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• 2018

AC-DC conversion is a necessary for the systems that require DC source. This conversion has been done via rectifiers based on controlled or uncontrolled semiconductor switches. Advances in the power electronics and microprocessor technologies allowed the use of Pulse Width Modulation (PWM) rectifiers. In this paper, dq-axis current and DC link voltage of three-phase PWM rectifier are controlled by using type-2 fuzzy neural network (T2FNN) controller. For this aim, a simulation model is built by MATLAB/Simulink software. The model is tested under three different operating conditions. The parameters of T2FNN is updated online by using back-propagation algorithm. The results obtained from both T2FNN and Proportional + Integral + Derivate (PID) controller are given for three operating conditions. The results show that three-phase PWM rectifier using T2FNN provides a superior performance under all operating conditions when compared with PID controller.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.529-538
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• 2015

Due to the high efficiency and compact mechanical structure, direct drive variable speed generators are used for power conversion in wind turbines. The wind energy conversion system (WECS) considered in this paper consists of a permanent magnet synchronous generator (PMSG), uncontrolled rectifier, dc-dc boost converter controlled with maximum power point tracking (MPPT) and adaptive hysteresis controlled voltage source inverter (VSI). For high utilization of the converter's power capability and stabilizing voltage and power flow, constant DC-link voltage is essential. Step and search MPPT algorithm which senses the rectified voltage ($V_{DC}$) alone and controls the same is used to effectively maximize the output power. The adaptive hysteresis band current control is characterized by fast dynamic response and constant switching frequency. With MPPT and adaptive hysteresis band current control in VSI, the DC link voltage is maintained constant under variable wind speeds and transient grid currents respectively.

• Journal of Power Electronics
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• 제11권6호
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• pp.931-937
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• 2011

This paper presents a method for the performance improvement of a shunt active power filter (SAPF) using the indirect current control (ICC) scheme. Compared to the conventional direct current control (DCC) scheme, the ICC gives better performance with a lower number of sensors. A simplified and efficient control algorithm using a low cost Intel 80C196KC microcontroller is implemented using only two current sensors for the source current and one voltage sensor for the DC-link voltage of the SAPF circuit. The objective is to eliminate harmonics and to compensate the reactive power produced by non-linear loads such as an uncontrolled rectifier feeding an inductive load. The APF is realized using a three phase voltage source inverter (VSI) with a dc bus capacitor. Experimental results are presented to prove the better performance of the ICC method over the DCC one.

• Journal of Power Electronics
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• 제10권4호
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• pp.419-427
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• 2010

A parallel control strategy in capacity proportion frequency allocation mode for shunt active power filters (APFs) is proposed to overcome some of the difficulties in high power applications. To improve the compensation accuracy and overall system stability, an improved selective harmonic current control based on multiple synchronous rotating reference coordinates is presented in a single APF unit, which approximately implements zero steady-state error compensation. The combined decoupling strategy is proposed and theoretically analyzed to simplify selective harmonic current control. Improved selective harmonic current control forms the basis for multi-APF parallel operation. Therefore, a parallel control strategy is proposed to realize a proper optimization so that the APFs with a larger capacity compensate more harmonic current and the ones with a smaller capacity compensate less harmonic current, which is very practical for accurate harmonic current compensation and stable grid operation in high power applications. This is verified by experimental results. The total harmonic distortion (THD) is reduced from 29% to 2.7% for a typical uncontrolled rectifier load with a resistor and an inductor in a laboratory platform.