• Journal of Power Electronics
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• 제17권1호
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• pp.56-66
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• 2017

Fast and accurate fault detection is the primary step and one of the most important tasks in fault tolerant converters. In this paper, a fast and simple method is proposed to detect and diagnosis the faulty cell in a cascaded H-bridge multilevel inverter under a short circuit fault. In this method, the reference voltage is calculated using switching control pulses and DC-Link voltages. The comparison result of the output voltage and the reference voltage is used in conjunction with active cell pulses to detect the faulty cell. To achieve this goal, the cell which is active when the Fault signal turns to "0" is detected as the faulty cell. Furthermore, consideration of generating the active cell pulses is completely described. Since the main advantage of this method is its simplicity, it can be easily implemented in a programmable digital device. Experimental results obtained with an 11-level inverter prototype confirm the effectiveness of the proposed fault detection technique. In addition, they show that the diagnosis method is unaffected by variations of the modulation index.

• 전기전자학회논문지
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• 제24권3호
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• pp.867-876
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• 2020

본 논문에서는 3레벨 인버터로 구동되는 IPMSM의 고주파 주입 센서리스 운전에서 중성점 전압 리플 저감을 제안한다. 고주파 전압 주입 기반의 센서리스 제어는 IPMSM의 저속 영역에서 일반적으로 사용하는 센서리스 제어 기법이다. 고주파 전압 주입을 이용한 IPMSM의 센서리스 제어 과정에서 중성점에서의 전압 리플이 증가하는 문제가 발생한다. 중성점에서의 큰 전압 리플은 출력 전류를 왜곡시킬 뿐만 아니라 직류단 커패시터의 수명을 단축시키므로 저감되어야 한다. 본 논문에서 제안하는 기법은 지령 전압에 적절한 값을 보상하여 중성점 전압 리플을 저감하며, 보상값은 지령 전압과 전류를 이용하여 간단히 계산한다. 제안하는 중성점 전압 리플 저감 기법의 타당성은 시뮬레이션을 통해 검증한다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.379-387
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• 2015

A custom power device provides an integrated solution to the present problems that are faced by the utilities and power distribution. In this paper, a new controller is designed which is connected to a multiconverter unified power quality conditioner (MC-UPQC) for improving the power quality issues adopted modified synchronous reference frame (MSRF) theory with Fuzzy logic control (FLC) technique. This newly designed controller is connected to a source in order to compensate voltage and current in two feeders. The expanded concept of UPQC is multi converter-UPQC; this system has a two-series voltage source inverter and one shunt voltage source inverter connected back to back. This configuration will helps mitigate any type of voltage / current fluctuations and power factor correction in power distribution network to improve power quality issues. In the proposed system the power can be conveyed from one feeder to another in order to mitigate the voltage sag, swell, interruption and transient response of the system. The control strategies of multi converter- UPQC are designed based on the modified synchronous reference frame theory with fuzzy logic controller. The fast dynamics response of dc link capacitor is achieved with the help of Fuzzy logic controller. Different types of fault conditions are taken and simulated for the analysis and the results are compared with the conventional method. The relevant simulation and compensation performance analysis of the proposed multi converter-UPQC with fuzzy logic controller is performed.

• 전력전자학회논문지
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• 제25권4호
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• pp.293-302
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• 2020

This study proposes a triple-loop current control method for the auxiliary power unit of fuel cell trains. The auxiliary power unit of fuel cell trains has a grid-connected function when power is supplied to the utility grid. Moreover, the auxiliary power unit of trains has a 1500 V DC link voltage; thus, PWM frequency cannot be increased to a high frequency. Owing to this low PWM frequency condition, creating a triple-loop design is difficult. In this study, a triple-loop controller is developed for a capacitor voltage controller in standalone mode that operates as an auxiliary power supply for trains and for a grid current controller in grid control mode with an inner capacitor voltage controller. The voltage controller employs an inductor current controller inner loop. To overcome low PWM frequency, a design method for the bandwidth of the capacitor voltage controller considering the bandwidth of the inner inductor current controller is described. The effectiveness of the proposed method is proven using PSIM simulation.

• 전력전자학회논문지
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• 제2권1호
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• pp.33-38
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• 1997

전기자동차용 배터리 충전회로에는 일반적으로 다양한 전력용 반도체 스위칭 소자들이 사용되고 있다. 따라서 사용소자의 비선형성에 기인하는 고조파 발생과 큰 피크전류, 낮은 역률 등으로 부근에 있는 전력시스템에 과도기전류나 파형 왜곡 현상을 발생한다. 그리하여 최근에는 기존의 정류회로에서 무시되었던 역율제어, 선 전류의 피크치 억제, 고조파 발생문제 등이 보다 중요하게 되었다. 따라서 본 연구에서는 기존의 문제점들을 해결하기 위해 전압 상승특성을 개선하고 역율이 0.97이상인 고역율 배터리 충전기용 콘버어터 회로를 제안하고자 한다. 제안된 시스템은 정류된 직류전압을 고주파 인버어터에서 교류 공진파로 변환하고, 고주파 트랜스를 통과한 전압을 다시 정류하여 직류전압으로 변환한다. 특히, 이러한 콘버어터의 사용효과는 역율제어에 의해서 크게 개선될 수 있는데, 납축전지를 이용한 실험을 통해 그 타당성을 입증하고자 한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.271-272
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• 2016

본 논문에서는 ESS 구성을 위한 고효율 3-레벨 양방향 인버터를 제안한다. 제안된 인버터는 저주파 레그와 고주파 레그로 구성되어, dc-link 전압과 계통간의 양방향 전력 변환을 수행한다. 제안된 인버터는 3-레벨의 전압을 제공하며 기존 풀브리지 타입의 2-레벨 인버터에 비해 고조파 성분이 적고 필터의 크기를 줄일 수 있다. 또한, 소자들에 걸리는 전압 스트레스가 낮고 동작 중에 스위칭 소자의 바디 다이오드를 사용하지 않기 때문에 도통 손실과 스위칭 손실을 최소화 할 수 있다. 따라서 제안하는 양방향 인버터는 기존 2-레벨 인버터 대비 높은 계통 전류 품질과 높은 효율을 제공한다. 최종적으로 시제품을 제작하여 제안하는 양방향 인버터의 타당성을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.220-221
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• 2006

This paper presents a single-phase parallel active power filter with an analog control circuit to eliminate for harmonic source currents generated by nonlinear loads. The proposed system removes the harmonic source currents by injecting a compensation current that is 180' out of phase with the load harmonic current. The detection of the load harmonics is realized by a simple new structure, referred to the Notch Filter with GIC (Generalized Impedance Converter), which has higher Q than existing harmonic detecters and a simpler structure. The compensation current is obtained using the proposed harmonic detection circuit, DC-Link voltage, and output current of the full-bridge inverter controlled current mode PWM controller. The operation of the proposed system is verified experimentally.

• 한국철도학회논문집
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• 제10권2호
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• pp.96-102
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• 2007

This paper presents a study on the control of a power quality compensating equipment of electrical railway built in small-scaled to preliminary research. Because this compensating equipment is very complicated power electronics system, consisting of a scott transformer as a power source, four single phase inverters interconnected with DC-link capacitors and various electrical apparatuses, multiple controllers and control algorithms with high performance and reliability are needed. The major function of the compensating equipment is to manage reactive and active powers by using the four single phase inverters, so, the main control effort is focused on the power flow control which realized through the decoupling current control of the four inverters. Overall control system is designed with object oriented and analyzed on a Simulink window. The simulation results show that the design scheme is very effective for a complicated control system and the proposed controller has good performance.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.153-159
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• 2012

In photovoltaic system, the characteristic of photovoltaic module such as open circuit voltage and short circuit current will be changed because of cell temperature and solar radiation. Therefore, a boost converter of the PV system connects between the output of photovoltaic system and DC link capacitor of grid connected inverter as controlling duty ratio for maximum power point tracking(MPPT). This paper shows the dynamic characteristic of the boost converter by comparing single-loop control algorithm and two-loop control algorithm using both analog and digital control. The proposed both compensation method has been verified with computer simulation and simulation results obtained demonstrate the validity of the proposed control schemes.

• 한국태양에너지학회 논문집
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• 제37권6호
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• pp.1-12
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• 2017

The DC link of Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS (PV-PCS) consists of two series connected capacitors for using their neutral voltage. The mismatch between two capacitor characteristics and transient states happened in load change cause the imbalance of neutral voltage. As a result, PV-PCS performance is degraded and the system becomes unstable. In this paper, a mathematical model for analyzing the imbalance of neutral voltage is derived and a compensation method using offset voltage is proposed, where offset voltage adjusts the applying time of P-type and N-type small vectors. The validity of the proposed methods is verified by simulation and experiment.