• 한국소음진동공학회논문집
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• 제23권6호
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• pp.527-536
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• 2013

In order to predict structural vibration and radiated noise of high-voltage transformer in operation, it is necessary to precisely find the excitation force generated by the coils and core. However, finding the excitation force through experiments of high voltage transformer in operation is not possible. Therefore, this paper deals with identifying the excitation force by using the acceleration data measured through experiments and the transfer function estimated through finite element model. A method to predict structural vibration and radiated noise was also proposed. Three-phase windings and the core are the source of high-voltage transformer. The excitation forces were identified using the acceleration data and the transfer function of the surface of the tank. Structural vibration and radiated noise from the surface of the tank was predicted by using the identified excitation force. As a result of the interpretation of the experimental and computational analysis of structural vibration from the surface of the tank and radiated noise from the field point, the interpretation of the computational analysis showed relatively good accordance with the experiment.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.75-82
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• 2015

This paper presents a new technique for enhancing power quality by reducing harmonics in the neutral conductor. Three-Phase Four-Wire (3P4W) system is commonly used where single and three phase loads are connected to Point of Common Coupling (PCC). Due to unbalance loads, the 3P4W distribution system becomes unbalance and current flows in the neutral conductor. If loads are non-linear, then the harmonic content of current will flow in neutral conductor. The neutral current that may flow towards transformer neutral point is compensated by using a series active filter. In order to reduce the harmonic content, the series active filter is connected in series with the neutral conductor by which neutral and phase current harmonics are reduced significantly. In this paper, solar PV based inverter circuit is proposed for compensating neutral current harmonics. The simulation is carried out in MATLAB/SIMULINK and also an experimental setup is developed to verify the effectiveness of the proposed method.

• 전력전자학회논문지
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• 제7권6호
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• pp.596-603
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• 2002

본 논문에서는 영상고조파 주입법을 사용하여 3상 다이오드 정류기의 입력전류를 개선하는 새로운 방식의 고조파 저감기술을 제안한다. 3고조파 주입을 근간으로 하는 본 방식은 다이오드 정류기의 상측과 하측의 전류를 독립적으로 제어하기 위하여 두 대의 단상 반파 인버터와 두 대의 단상 변압기로 구성되어져 있다. 이렇게 만들어진 영상전류는 zigzag 변압기에 의해서 다이오드 정류기의 상측과 하측으로 주입이 되어진다. 이 결과 3상 다이오드 정류기의 입력전류는 순수한 정현파 전류가 된다. 본 방식의 타당성을 1.5kVA 시작품의 실험을 통하여 입증하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제16권4호
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• pp.102-112
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• 1992

The three-phase full(6-pulse) bridge controlled rectifier is one of the most widely used types of solid-state converters in DC drive applications for higher performance. In most of the previous designs, the gate control circuits of the converter have been designed with analog method which can be easily affected by noise. Nowdays with advances of microelectronics and power electronics, microprocessor and pheripal LSIs are increasingly used for eliminating this problems. In this paper, a novel general-purpose microprocessor -based firing system and control scheme for a three-phase controlled rectifier bridge has been developed and tested. Using the phase relations between ${\Delta}$-Y transformer in power operation part, gate pulse of the converter is generated with real time process so that microprocessor may share its time to control algorithms efficiently. The firing angle of the converter is smoothly controlled in the range of 0 $^{\dirc}$ to 180$^{\dirc}$ with a fast respone and a constant open loop gain, even for the case where the converter is fed by a weak AC system of unregulated frequency. The hardware and software control circuit implementation built around a 80286 microprocessor is discussed, and the experimental results are given. This scheme uses less hardware components and has higher dynamic performance in variable speed DC drive applications.

• 전력전자학회논문지
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• 제26권5호
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• pp.372-375
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• 2021

A three-leg inverter-type isolated DC-DC Converter that can use 220 and 440 V grid input voltages is introduced. The secondary circuit structure of the proposed topology is center-tap, which is the same as the conventional phase-shifted full-bridge converter. However, the primary circuit structure is composed of a three-leg inverter structure and a transformer, in which two primary windings are connected in series. The proposed circuit structure has a wider input voltage range than the conventional phase-shifted full-bridge converter, and the circulating-current on the primary-side is reduced. In addition, the voltage stress at the secondary rectifier is greatly improved, and high efficiency can be achieved at a high input voltage by removing the snubber circuit added to the conventional converter. Prototype converters with input DC of 311 V, output of 622 V, and 50 V and 6 kW class specifications were designed and manufactured to verify the validity of the proposed topology; the experimental results are presented.

• 전력전자학회논문지
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• 제16권3호
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• pp.209-218
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• 2011

연료전지와 같은 저전압 대전류 응용에는 입력전류 리플이 작고 변압기의 턴비가 작은 전류원 DC-DC 컨버터가 더 효과적이다. 5kW급 이상의 응용에서는 기존의 단상을 기본으로 하는 전류원 풀브리지, 하프브리지 또는 푸시풀 의 토폴로지로는 스위치등 소자의 전류부담이 크고 소자의 선정 및 최적설계가 용이하지 않다. 본 논문에서는 대전력 고승압 응용에 적합한 능동 클램프방식의 3상 전류원 푸쉬풀 DC-DC 컨버터를 제안한다. 제안한 컨버터는 소자의 전류부담이 작고 전 영역(0～1)의 듀티 사용으로 입력전압 변동이 큰 응용에 적합하다. 3상 고주파변압기를 비롯한 주요부품의 설계방법을 제시하고 5kW급의 시작품으로부터 제안한 컨버터의 타당성 및 성능을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.598-602
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• 2002

This paper presents the 3-phase hybrid series active power filter with dynamic voltage restorer(DVR) which serve as an energy buffer and current harmonics blocking resistor connected to sensitive loads, such as, to compensate voltage dips and current harmonics in power distribution system. The DVR is to inject a dynamically controlled voltage generated by a forced commutated converter in series to the bus voltage by means of a booster transformer. The momentary amplitudes of the three injected phase voltages are controlled such as to eliminate any detrimental effects of a bus fault to the load voltage. The proposed system is able to simultaneously compensate current harmonics, voltage fluctuating and voltage unbalance in power distribution systems. The reference phase angle detected by synchronized with the positive sequence component of the unbalanced source by using symmetrical component transformation. The effectiveness of proposed system is verified by the computer simulation.

• Journal of Power Electronics
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• 제9권6호
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• pp.874-883
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• 2009

This paper deals with an integrated voltage and frequency (VF) controller for isolated asynchronous generators (IAG) driven by a constant power pico-hydro uncontrolled turbine feeding three-phase four-wire loads. The proposed VF controller is used to control the frequency and voltage of an IAG with load leveling. Such a VF controller is also known as an integrated electronic load controller (IELC) which is realized using an isolated star/polygon transformer with a voltage source converter (VSC) and a battery at its DC bus. The proposed generating system with a VFC is modeled and simulated in MATLAB along with Simulink and Simpower system (SPS) toolboxes. The simulated results are presented to demonstrate the performance of an isolated asynchronous generator feeding three-phase four-wire loads with neutral current compensation.

• 전력전자학회논문지
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• 제8권2호
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• pp.192-198
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• 2003

본 논문에서는 의료 진단용 40kw(125kV, 80mA)급 X-선 전원 장치에 대하여 연구하였다. 의료 X-선용 고전압 발생 장치의 구성과 X-선 관전압과 관전류 그리고 피폭량 제어에 대하여 기존 제어 방식과 비교 설명하였고 제어기 설계시 고려할 사항에 대하여 언급하였다. 또한, 본 시스템의 핵심이라 할 수 있는 고주파 고전압 변압기의 등가회로를 통한 기생 성분에 대하여 기술하였으며 본 연구에서 제작된 의료 X-선용 HFG 시스템의 출력특성의 우수성을 X-전관 부하 변동에 따른 X-선 관전류와 관전압 파형을 통하여 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전력기술부문
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• pp.363-365
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• 2006

This paper proposes an estimation method for a circulating current of a Y-${\Delta}$ Transformer. The delta winding current can be decomposed into the two components i.e. a non-circulating component and a circulating component. The former can be estimated using the line currents. However, the latter can not be estimated directly using the line currents. A first order differential equation for the circulating current is derived by applying the Kirchhoff's voltage law on the loop of the delta side. The circulating current can be estimated by the solving the differential equation. The performance of the proposed algorithm is investigated under various conditions including magnetic inrush and over-excitation. The algorithm can estimate the circulating current very accurately even under magnetic inrush and over-excitation.