• 조명전기설비학회논문지
• /
• 제27권9호
• /
• pp.36-43
• /
• 2013

The prevalence of electronic devices in our modern life is accompanied with the generation of harmonics caused by the nonlinear characteristic load. Especially, the employment of LED have brought the rapid use of SMPS. SMPS is used for supplying the constant DC electric power to the LED display board, but it has a big problem which gives birth of harmonics causing by its high-speed switching. measurement HIOKI 3196 equipment to solve these harmonics were measured. In this study, we are LED Display Board Load Measuring the impedance response with $X_L$ changes for removing harmonics in the measured. And we adopted the suitable passive filter by the impedance response characteristic obtained in the $X_L$ variation experiments. We are trying to deeply the application of passive harmonic filter characteristics that generation in the LED Display Board through EDSA LED simulation.

• 전기학회논문지P
• /
• 제64권2호
• /
• pp.79-84
• /
• 2015

Voltage sags are considered the dominant disturbances affecting power quality. Dynamic voltage restorers(DVRs) are mainly used to protect sensitive loads from the electrical network voltage disturbances such as sags or swells and could be used to reduce harmonic distortion of ac voltages. The typical DVR topology essentially contains a PWM inverter with LC Filter, an injection transformer connected between the ac voltage line and the sensitive load, and a DC energy storage device. For injecting series voltage, the PWM inverter is used and the passive filter consist of inductor(L) and capacitor(C) for harmonics elimination of the inverter. However there are voltage pulsation responses by the characteristic of the LC passive filter that eliminate the harmonics of the PWM output waveform of the inverter. Therefore, this paper presented design and feedback performance of LC filter used in the DVRs. The voltage control by LC filter should be connected in the line side since this feedback method allows a relatively faster dynamic response, enabling the elimination of voltage notches or spikes in the beginning and in the end of sags and strong load voltage THD reduction. Illustrative examples are also included.

• Journal of Power Electronics
• /
• 제14권2호
• /
• pp.257-264
• /
• 2014

A novel converter-free AC LED driver that is highly resistant to the fluctuation of AC voltage is proposed in this study. By removing large passive components, such as the bulky capacitor and the large-value inductor, the integration of the driver circuit is enhanced while the driving current remains stable. The proposed circuit provides LED lamps with a driving current that can follow the sinusoid waveform to obtain a very high power factor (PF) and low total harmonic distortion (THD). The LED input current produced by this driving current is insensitive to fluctuations in the AC voltage. Users will thus not feel that LED lamps are flashing during the fluctuation. Experiment results indicate that the proposed system can obtain PF of 0.999 and THD as low as 3.3% for a five-string 6 W LED load under 220 V at 50 Hz.

• 한국정보통신학회논문지
• /
• 제17권1호
• /
• pp.127-136
• /
• 2013

계통연계형 인버터의 중요 성능 중 단독운전 검출기능 및 방지기능은 계통을 유지보수하기 위한 작업자의 안전을 위하여 고려되어야 할 필수 사항이다. 본 논문에서는 태양광을 이용한 계통연계형 태양광발전시스템에서의 AFS(Active Frequency Shake) 단독운전 검출기법을 제안하고자 한다. 먼저 AFS 단독운전 검출 알고리즘을 제안하기 위하여 기존의 능동 주파수 변이기법 알고리즘에 대해 기술한다. 그리고 단독운전 불검출영역을 줄이고, THD(Total Harmonic Distortion)를 개선하며, 기존 알고리즘 보다 검출 속도 또한 향상 시킬 수 있는 알고리즘을 제시하였다. 아울러 제안된 단독운전방지 기법을 3kW 계통연계형 태양광 인버터에 적용하고 시뮬레이션 및 실험을 통하여 제안하는 알고리즘의 타당성을 검증하였다.

• 한국산학기술학회논문지
• /
• 제20권3호
• /
• pp.465-469
• /
• 2019

본 논문에서는 콘크리트 바이브레이터에 Slotless BLDC (Brush Less Direct Current) 모터를 적용하기 위해 BLDC 모터의 토크 및 역기전력 식을 기반으로 하여 설계를 한다. 모터의 길이와 직경의 사이즈가 주어져 있으므로 중요한 파라미터는 공극자속밀도이다. 자기회로의 간략화를 통하여 공극자속밀도를 계산 하였으며, 토크, 역기전력 및 공극자속밀도 식을 기반으로 기초설계를 진행하여 모터의 형상을 결정 하였다. 이후 모터의 고정자의 외경 및 내경, 스택 길이, 속도를 고정값으로 설정한 후 모터의 직경 및 두께를 변수로 지정하여 유한요소법을 이용한 시뮬레이션을 통해 상세설계를 진행하였으며, THD(Total Harmonic Distortion)값이 작으면서 목표 토크 값 이상의 형상을 설계 및 시뮬레이션을 진행하였다.

• 한국컴퓨터정보학회논문지
• /
• 제28권12호
• /
• pp.231-238
• /
• 2023

부스트 PFC (Power Factor Correction)컨버터는 AC 입력 전류의 단일 역률과 낮은 THD (Total Harmonic Distortion)를 달성하기 위해 다양한 제어기법들이 연구되고 있다. 그중 인덕터 전류의 평균값을 전류지령에 추종하도록 제어하는 평균전류 모드 제어가 있으며 가장 널리 사용되고 있다. 하지만, 오늘날 디지털 프로세서의 발달로 고도화된 디지털 제어가 가능해지면서 부스트 PFC 컨버터의 예측제어가 관심을 받고 있다. 예측제어에는 예측 알고리즘으로 듀티를 미리 생성하는 예측전류 모드 제어 및 모델을 기반으로 한 비용함수를 선정하여 스위칭 동작을 하는 모델예측제어로 분류된다. 따라서 본 논문에서는 부스트 PFC 컨버터의 평균전류 모드 제어, 예측전류 모드 제어, 모델예측 전류 제어를 간단히 설명한다. 또한, 시뮬레이션을 통해 전체 부하 및 다양한 외란 조건에서의 전류 제어를 비교 분석한다.

• 전력전자학회논문지
• /
• 제25권5호
• /
• pp.358-368
• /
• 2020

Grid-connected inverters (GCIs) based on renewable energy sources play an important role in enhancing the sustainability of a society. Harmonic standards, such as IEEE 519 and P1547, which require the total harmonic distortion (THD) of the output current to be less than 5%, should be satisfied when GCIs are connected to a grid. However, achieving a current THD of less than 5% is difficult for GCIs with an output filter under a distorted grid condition. In this study, a novel harmonic compensation method that uses a digital lock-in amplifier (DLA) is proposed to eliminate harmonics effectively at the output of GCIs. Accurate information regarding harmonics can be obtained due to the outstanding performance of DLA, and such information is used to eliminate harmonics with a simple proportional-integral controller in a feedforward manner. The validity of the proposed method is verified through experiments with a 5 kW single-phase GCI connected to a real grid.

• 전력전자학회논문지
• /
• 제15권4호
• /
• pp.266-273
• /
• 2010

태양광 인버터(PCS)는 태양전지에서 발생된 전력을 계통에 연계시키는 장치이다. IEEE 1547 규격에 따르면 PCS에서 발생되는 고조파왜곡은 5% 이내여야만 한다. 일반적으로 PCS에서 계통으로 유입되는 고조파 검출은 전용 계측장치에 의해서 측정된다. 초기에 규격에 맞게 설계된 PCS의 고조파가 소자들의 노화나 제어기 고장에 의해 증가하게 될 경우 발전을 중지하거나 경보를 발생시켜야 한다. 기존의 상용화된 시스템에는 이러한 기능이 존재하지 않는다. 본 연구에서는 PCS 내부에 고조파왜곡을 실시간으로 측정하는 알고리즘을 내장시키는 방법에 대해 연구한다. 고성능 32-bit 부동소수점 DSP를 이용한 PCS를 제작하고 256-point DFT(Discrete Fourier Transform) 알고리즘을 이용하여 1[ms] 이내에 하모닉 계수를 계산하였다. 제어기 제작에 대한 설명과 실험 결과로서 연구의 타당성을 입증하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제52권2호
• /
• pp.68-79
• /
• 2003

We estimated harmonics on power system of AC railway based on quantitatively measured harmonics and investigated the need of facilities for harmonics reduction. In order to analysis harmonics which inflow into power system due to increase in collector voltages and harmonic currents generated from the train when the railway is in operation, the railway system Is sectioned into power supply, railway line, AT, sectioning Post and subsectioning post. For analysis of extension of currents resulting from the railway loads, PWM converter, VVVF inverter and the feeder system are modeled based on the dynamic node technique(DNT). In order to test the usefulness of the DNT for analysis of harmonic effects, the measured harmonic currents and harmonic magnification ratios at the S/K substation are compared with simulation results using DNT modelling, which include the results for two cases with and without filters for suppression of harmonic currents. When 8 cars(4M4T) are in operation, the total sum of harmonic currents resulting from the train at M and T phases, which inflow into the substation along with the railway line, is calculated. Using the harmonics analysis program for railway feeder system with these data, the total harmonic distortion factor(710) at the outgoing point of KEPCO substation is computed. The calculation shows that when the maximum THD at the receiving point of H/K substation was 0.0443% which is much lower than 1.5% which is the allowable value of KEPCO at 154kV as well as IEEE-519 above 132kV This result indicates that any measure for harmonics reduction in Incheon International Airport Railway is not needed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.147-148
• /
• 2006

Recently, due to increasing the application of power electronic equipment, harmonics generated from the non-liner load are fairly produced. Harmonics can cause a variety of problems such as the overheating of distribution transformer, the breakdown of device and communication interference. Interest about power quality decline of power system is very increased. In this paper, we are measured the harmonic voltage and current o( power system to analyze harmonic characteristics, and it is analyzed Total Harmonic Distortion(THD). Also, we Ere modeled power system using PSCAD/EMTDC. And it is analyzed harmonic voltage and current in steady-state. The study results have been indicated the utility about harmonics analysis and modelling for power system.