• Journal of Power Electronics
• /
• 제13권5호
• /
• pp.909-918
• /
• 2013

This paper proposes a coordinated control of the reactive power between the STATCOMs (static synchronous compensators) and the grid-side converters (GSC) of wind farms equipped with PMSGs (permanent-magnet synchronous generators), by which the voltage fluctuations at the PCC (point of common coupling) are mitigated in the steady state. In addition, the level of voltage sags is reduced during grid faults. To do this, the GSC and the STATCOM supply reactive power to the grid coordinately, where the GSCs are fully utilized to provide the reactive power for the grid prior to the STATCOM operation. For this, the GSC capability of delivering active and reactive power under variable wind speed conditions is analyzed in detail. In addition, the PCC voltage regulation of the power systems integrated with large wind farms are analyzed for short-term and long-term operations. With this coordinated control scheme, the low power capacity of STATCOMs can be used to achieve the low-voltage ride-through (LVRT) capability of the wind farms during grid faults. The effectiveness of the proposed strategy has been verified by PSCAD/EMTDC simulation results.

• Journal of Advanced Marine Engineering and Technology
• /
• 제36권7호
• /
• pp.935-941
• /
• 2012

This paper describes a study of conventional electrical rig and simulated application of Flywheel Energy Storage system on the power system of the offshore plants with dynamic positioning system with the following aims: improve fuel consumption on engines, prevent blackout and mitigate voltage sags due to pulsed load and fault. Fuel consumption has been analyzed for the generators of the typical drilling rigs compared with the power plant with Flywheel Storage Unit which has an important aid in avoiding power interruption during DP (Dynamic Positioning) operation. The FES (Fly wheel Energy storage System) releases energy very quickly and efficiently to ensure continuity of the power supply to essential consumers such as auxiliary machinery and thrusters upon main power failure. It will run until the standby diesel generator can start and supply the electric power to the facilities to keep the vessel in correct position under DP operation. The proposed backup method to utilize the quick and large energy storage Flywheel system can be optimized in any power system design on offshore plant.

• Journal of Electrical Engineering and Technology
• /
• 제8권3호
• /
• pp.544-558
• /
• 2013

This paper proposes a simplified and efficient control scheme for Unified Power Quality Conditioner (UPQC) based on three-level (NPC) inverter capable to mitigate source current harmonics and compensate all voltage disturbances perturbations such us, voltage sags, swells, unbalances and harmonics. The UPQC is designed by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. The shunt and series AF are designed using a three-phase three-level (NPC) inverter. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt and the power reactive theory (PQ) for a series APFs. The reference signals for the shunt and series APF are derived from the control algorithm and sensed signals are injected in tow controllers to generate switching signals for series and shunt APFs. The performance of proposed UPQC system is evaluated in terms of power factor correction and mitigation of voltage, current harmonics and all voltage disturbances compensation in three-phase, three-wire power system using MATLAB-Simulink software and SimPowerSystem Toolbox. The simulation results demonstrate that the proposed UPQC system can improve the power quality at the common connection point of the non-linear load.

• 조명전기설비학회논문지
• /
• 제21권4호
• /
• pp.36-44
• /
• 2007

This study researched the mutual relationship between elevator emergencies(sudden stops, entrapment) and power quality such as voltage interruptions or sags. To analyze the power quality at the elevator switchboard of an apartment, the on-line power quality(sag, swell, and interruption, etc.) were measured and error messages(under voltage error, etc.) in the elevator control room were researched. Also the performance and susceptibility for stops were evaluated and stated through the testing of three pieces of simulated test equipment with an EN12016(2004) standard setting and the magnitude and duration data of the measured sag or interruption. This paper will use these data in the analysis of the mutual relationship between power quality and elevator emergencies.

• Molecules and Cells
• /
• 제25권3호
• /
• pp.438-445
• /
• 2008

Leaf senescence is a highly regulated genetic process that constitutes the last stage of plant development and provides adaptive fitness by relocating metabolites from senescing leaves to reproducing seeds. Characterization of various senescence mutants, mostly in Arabidopsis, and genome-wide analyses of gene expression, have identified a wide array of regulatory components, including transcription factors and enzymes as well as signaling molecules mediating growth hormones and environmental stress responses. In this work we demonstrate that a membrane-associated NAC transcription factor, NTL9, mediates osmotic stress signaling in leaf senescence. The NTL9 gene is induced by osmotic stress. Furthermore, activation of the dormant, membrane-associated NTL9 is elevated under the same conditions. A series of senescence-associated genes (SAGs) were upregulated in transgenic plants overexpressing an activated form of NTL9, and some of them were slightly but reproducibly downregulated in a T-DNA insertional NTL9 knockout mutant. These observations indicate that NTL9 mediates osmotic stress responses that affect leaf senescence, providing a genetic link between intrinsic genetic programs and external signals in the control of leaf senescence.

• 대한전기학회논문지:전력기술부문A
• /
• 제50권12호
• /
• pp.575-583
• /
• 2001

Dynamic Voltage Restorer(DVR) which is installed between the supply and a critical load can restore voltage disturbances in distribution system. The restoration is based on injecting the same voltages as voltage sags. The ideal restoration is compensation to make the load voltages be unchanged. But voltage restoration involves real power or energy injection and the capability of energy storage is limited. So it must be considered how injection energy can be minimized and voltages can be made close to the voltages before fault. This paper describes conventional restoration techniques, which draw minimum energy from the DVR in order to correct a given voltage sag or swell. And this paper proposes a new concept of restoration technique to inject minimum energy. The proposed method is based on the definition of voltage tolerance in load side. Hence using the proposed method a particular disturbance can be corrected with less amount of storage energy compared to those of conventional methods.

• Journal of Power Electronics
• /
• 제18권6호
• /
• pp.1830-1843
• /
• 2018

In this paper, the generation of a reference current and voltage signal based on a Kalman filter is offered for a 3-phase 4wire UPQC (Unified Power Quality Conditioner). The performance of the UPQC is improved with source voltages that are distorted due to harmonic components. Despite harmonic and frequency variations, the Kalman filter is capable enough to determine the amplitude and the phase angle of load currents and source voltages. The calculation of the first state is sufficient to identify the fundamental components of the current, voltage and angle. Therefore, the Kalman state estimator is fast and simple. A Kalman based control strategy is proposed and implemented for a UPQC in a distribution system. The performance of the proposed control strategy is assessed for all possible source conditions with varying nonlinear and linear loads. The functioning of the proposed control algorithm with a UPQC is scrutinized and validated through simulations employing MATLAB/Simulink software. Using a FPGA SPATRAN 3A DSP board, the proposed algorithm is developed and implemented. A small-scale laboratory prototype is built to verify the simulation results. The stated control scheme for the UPQC reduces the following issues, voltage sags, voltage swells, harmonic distortions (voltage and current), unbalanced supply voltage and unbalanced power factor under dynamic and steady-state operating conditions.

• 한국전자통신학회논문지
• /
• 제16권2호
• /
• pp.293-300
• /
• 2021

본 연구에서는 SCDF를 사용하여 전력공급의 가치를 산정하고, 부하점별 중요도를 다면적인 평가를 하는 방법을 제시한다. 이의 방법으로 지속정전, 순간정전, 전압 Sag/Swell에 대응할 수 있는 SCDF를 제공하고, 이 SCDF를 사용하여 정전과 관련하여 어느 부하점에 어느 정도의 비용이 발생하는지를 계산하였으며, 이들 비용을 다면평가를 통해 어느 부분이 어느정도 취약한지를 평가하고 어느 부분의 확장이 필요한 지를 수치적으로 설명할 수 있도록 하였다. 본 연구를 우리나라의 실배전계통에 적용하여 평가하고 유용성을 검증하였다.

• Nuclear Engineering and Technology
• /
• 제51권5호
• /
• pp.1314-1321
• /
• 2019

In case of multiple failure scenario, such as LOCA with ECCS failure, the decay heat continues to raise the reactor core temperature, eventually leading to the core voiding. In such scenario the convective heat transfer becomes poor and the majority of the heat transfer from fuel bundle takes place by radiation mode. During this abnormal working condition, if the channel pressure is less than 1 MPa, the PT sags and come in contact with the CT. This results in high rate of heat transfer from contact location to moderator. The present paper aims to capture the temperature profile over a simulated nuclear channel during such scenario at a steady state temperature of $600^{\circ}C$ (Centre pin) at two different configurations of PT i.e. PT concentric with CT and PT contact with CT. The results showed that the bottom nodes of all the components (Fuel bundle, PT and CT) of the simulated channel was greatly influenced by the PT/CT contact. Moreover, higher temperature were observed at top nodes of the PT and outer pins of the fuel bundle. However, no significant variation in temperatures were obtained in fuel bundle and CT in concentric condition.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2021년도 추계학술대회
• /
• pp.290-291
• /
• 2021

플라스틱 소재 자동차 부품의 도장 공정에서 불량은 다양한 원인과 현상으로 기인하는데, 온도, 습도, 미세먼지 등 기상환경 조건의 변화에 따라 불량률이 변화하는 연관성을 분석하였다. 실제 도장업체에서 1년 동안 수집한 종류별, 원인별 불량률과 기상환경의 상관성을 머신러닝 기법에 의해 학습하고 시험하여 특정의 기상환경에서 불량률을 예측하였다. 그 결과 실먼지로 인한 불량은 98%, 흐름에 대한 불량은 90%의 불량을 예측하여 모델의 성능을 입증하였다.