Protection for a Wind Turbine Generator in a Large Wind Farm

Tai-Ying Zheng,Yeon-Hee Kim,Yong-Cheol Kang 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.4

This paper proposes a protection algorithm for a wind turbine generator (WTG) in a large wind farm. To minimize the outage section, a protection relay for a WTG should operate instantaneously for an internal fault or a connected feeder fault, whereas the relay should not operate for an internal fault of another WTG connected to the same feeder or an adjacent feeder fault. In addition, the relay should operate with a delay for an inter-tie fault or a grid fault. An internal fault of another WTG connected to the same feeder or an adjacent feeder fault, where the relay should not operate, is determined based on the magnitude of the positive sequence current. To differentiate an internal fault or a connected feeder fault from an inter-tie fault or a grid fault, the phase angle of the negative sequence current is used to distinguish a fault type. The magnitude of the positive sequence current is then used to decide either instantaneous operation or delayed operation. The performance of the proposed algorithm is verified under various fault conditions with EMTP-RV generated data. The results indicate that the algorithm can successfully distinguish instantaneous operation, delayed operation, or non-operation depending on fault positions and types.

Protection for a Wind Turbine Generator in a Large Wind Farm

Zheng, Tai-Ying,Kim, Yeon-Hee,Kang, Yong-Cheol The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.4

This paper proposes a protection algorithm for a wind turbine generator (WTG) in a large wind farm. To minimize the outage section, a protection relay for a WTG should operate instantaneously for an internal fault or a connected feeder fault, whereas the relay should not operate for an internal fault of another WTG connected to the same feeder or an adjacent feeder fault. In addition, the relay should operate with a delay for an inter-tie fault or a grid fault. An internal fault of another WTG connected to the same feeder or an adjacent feeder fault, where the relay should not operate, is determined based on the magnitude of the positive sequence current. To differentiate an internal fault or a connected feeder fault from an inter-tie fault or a grid fault, the phase angle of the negative sequence current is used to distinguish a fault type. The magnitude of the positive sequence current is then used to decide either instantaneous operation or delayed operation. The performance of the proposed algorithm is verified under various fault conditions with EMTP-RV generated data. The results indicate that the algorithm can successfully distinguish instantaneous operation, delayed operation, or non-operation depending on fault positions and types.

The Establishment of Tumor Necrosis Factor Receptor-associated Protein1 (TRAP1) Transgenic Mice and Severe Fat Accumulation in the Liver of TRAP1 Mice during Liver Regeneration

Im, Chang-Nim,Zheng, Ying,Kim, Sun Hye,Huang, Tai-Qin,Cho, Du-Hyong,Seo, Jeong-Sun Korean Society for Bioinformatics 2013 Interdisciplinary Bio Central (IBC) Vol.5 No.4

Introduction: Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a mitochondrial heat shock protein (HSP), which belongs to HSP90 family. It plays important roles in regulating mitochondrial integrity, protecting against oxidative stress, and inhibiting cell death. Recent studies suggest that TRAP1 is linked to mitochondria and its metabolism. In this study, we established TRAP1 transgenic mice and performed partial hepatectomy (PH) on wild-type (WT) and TRAP1 transgenic mice to investigate the function of TRAP1 during liver regeneration. Results and Discussion: We found that TRAP1 was highly expressed in liver as well as kidney. In addition, liver regeneration slightly decreased together with increased fatty liver and inflammation at 72 hr after PH in TRAP1 transgenic mice compared with WT control group mice. Concomitantly, we observed decreased levels of p38 protein in TRAP1 transgenic mice compared with WT control group mice. These results suggest that TRAP1 plays a critical role in liver energy balance by regulating lipid accumulation during liver regeneration. Conclusions and Prospects: To our knowledge, we reported, for the first time, that liver regeneration slightly reduced together with increased fat accumulations after PH in TRAP1 transgenic mice compared with WT control group mice. Concomitantly, we observed decreased levels of p38 protein in TRAP1 transgenic mice compared with WT control group mice. Overexpression of TRAP1 might affect liver regeneration via disturbing mitochondrial function leading to fatty liver in vivo.

Analysis of Response of a Wind Farm during Grid/Inter-tie Fault Conditions

Lee, Hye-Won,Kim, Yeon-Hee,Zheng, Tai-Ying,Lee, Sang-Cheol,Kang, Yong-Cheol 대한전기학회 2012 The Journal of International Council on Electrical Vol.2 No.3

A wind farm consists of a large number of small wind turbine generators (WTGs) whilst a thermal power plant consists of a small number of large generators. To maintain high quality and high reliability of electrical energy, the wind farm should have the same performance as the thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid or at an inter-tie. This gives significant effects on both the operation of a wind farm and the power system stability. This paper describes an analysis of response of a wind farm during grid/inter-tie fault conditions. During fault conditions, each WTG might produce different frequencies in the voltage. These result in the non-fundamental frequencies in the voltage and the current of a point of common coupling, which is called by "beats". This phenomenon requires careful attention on control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement. Moreover, it may cause difficulties in protection relays of a wind farm. The response of a wind farm for various fault and wind conditions of each WTG was analyzed using a PSCAD/EMTDC simulator.

후류 효과를 고려한 풍력발전단지 출력 변동률 분석

김연희(Yeon-Hee Kim),정태영(Tai-Ying Zheng),이혜원(Hye-Won Lee),이진식(Jin-Shik Lee),강용철(Yong Cheol Kang) 대한전기학회 2012 대한전기학회 학술대회 논문집 Vol.2012 No.10

자속-자화 전류 곡선과 전압-철손 전류 곡선을 이용한 측정용 철심 변류기의 보상 알고리즘 개발

강용철(Yong-Cheol kang),정태영(Tai-Ying Zheng),강해권(Hae-Gweon Kang),이병은(Byung-Eun Lee),김용균(Yong-Gyun Kim) 대한전기학회 2009 전기학회논문지 Vol.58 No.10

This paper describes the design, evaluation and implementation of a compensating algorithm for an iron-cored measurement current transformer (CT) that removes the effects of the hysteresis characteristics of the iron-core. The exciting current resulting from the hysteresis characteristics of the core causes an error of the CT. The proposed algorithm decomposes the exciting current into the core loss current and the magnetizing current and each of them is estimated. The core loss current is calculated from the secondary voltage and the voltage-core loss current curve. The core flux linkage is calculated and then inserted into the flux-magnetizing current curve to estimate the magnetizing current. The exciting current at every sampling interval is obtained by summing the core loss and magnetizing currents and then added to the measured current to obtain the correct secondary current. The voltage-core loss current curve and flux-magnetizing current curves, which are different from the conventional curves, are derived in this paper. The performance of the proposed algorithm is validated under various conditions using EMTP generated data. The experimental test results of an iron-core type electronic CT, which consists of the iron-core and the compensation board, are also included. The results indicate that the proposed algorithm can improve the accuracy of the measurement CT significantly, and thus reduce the size and the cost of the CT.

거센 강풍 시 해상풍력단지 강제종료 방법

김연희(Yeon-Hee Kim),정태영(Tai-Ying Zheng),이진식(Jin-Shik Lee),강용철(Yong-Cheol Kang) 대한전기학회 2011 대한전기학회 학술대회 논문집 Vol.2011 No.10

This paper assumes that a wind mast (WM) is installed several kilometers from a wind power plant (WPP) to collect the direction and the speed of wind. The distance between the WM and the WPP is determined based on the expected storm speed to meet the ramp rate requirement of a grid code. This paper proposes a supervised shutdown algorithm of a large off-shore WPP in a heavy storm situation. Based on the information on the direction and the speed of wind measured at a WM, a sequence of wind generator group is generated. Each group is shut down with the required maximum ramp-down rate in the order of wind arriving time. The shutdown start/end times of each group may be re-scheduled to avoid superposition between adjacent two groups. If the wind speed exceeds the expected speed, the ramp rate is unable to meet the required grid code. In this case, the minimum number of the wind generator groups rate is decided, which are shut down with the twice the required ramp rate. The performance of the proposed supervised shutdown algorithm is verified considering various heavy storm scenarios. The results show that the proposed algorithm can protect the large WPP from various heavy storm situations, generating energy as much as possible with the minimal adverse effects on the power system stability.

역상 전류를 이용한 풍력발전기 보호 방법

강용철(Yong-Cheol Kang),정태영(Tai-Ying Zheng),국경수(Kyung-Soo Kook),강해권(Hae-Gweon Kang),이병은(Byung-Eun Lee),김연희(Yeon-Hee Kim) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7

This paper proposes a wind turbine protection method using the negative sequence current flowing through the wind turbine. The feasibility of the proposed method is proved by applying the symmetrical analysis to the power system integrated with a large scale wind farm. The performance of the proposed method is verified based on the EMTP-RV simulation. The results show that the negative sequence currents flowing through the wind turbines connected to the faulted feeder, where a single-phase-to-ground fault occurs, is much larger than those flowing through the wind turbines connected to the healthy feeder, and thus the magnitude of the negative sequence current can be used to easily detect whether there is a single-phase-to-ground fault occurring in the connected feeder.

CT와 CCVT의 오차를 고려한 거리 계전기의 응동 분석

강용철(Yong-Cheol Kang),정태영(Tai-Ying Zheng),최재선(Jae-Sun Choi),강해권(Hae-Gweon Kang),김광무(Kwang-Moo Kim),장성일(Sung-Il Jang),김용균(Yong-Gyun Kim) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.11

A distance relay has been widely used for transmission line protection. The distance relay detects a fault based on the calculated impedance i.e. the ratio of the voltage to the current measured from a current transformer (CT) and a coupling capacitor voltage transformer (CCVT), respectively. When a fault occurs and a C saturates due to the magnitude of fault current, dc component, primary time constant, and the remanent flux of the iron core, the secondary current of a CT is distorted. On the other hand, non-fundamental components generated during a fault can increase the error of a CCVT, particularly when a fault distance is short. The distortion of the current and voltage can cause mal-operation or the operating time delay of a distance relay. This paper describes the response of a distance relay considering the errors of a CT and a CCVT. The results indicate that the severe distortion of a CT and a CCVT have noticeable effect to a distance relay.

그리드/연계선 사고 시 풍력발전단지의 응동 분석

이혜원(Hye-Won Lee),김연희(Yeon-Hee Kim),정태영(Tai-Ying Zheng),이상철(Sang-Cheol Lee),강용철(Yong-Cheol Kang) 대한전기학회 2011 전기학회논문지 Vol.60 No.6

In a wind farm, a large number of small wind turbine generators (WTGs) operate whilst a small number of a large generator do in a conventional power plant. To maintain high quality and reliability of electrical energy, a wind farm should have equal performance to a thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid, which gives significant effects on the operation of a wind farm and the power system stability. This paper presents an analysis of response of a wind farm during grid fault conditions. During fault conditions, each WTG might produce different frequency components in the voltage. The different frequency components result in the non-fundamental frequencies in the voltage and the current of a wind farm, which is called by “beats”. This phenomenon requires considerable changes of control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement of a wind farm. Moreover, it may cause difficulties in protection relays of a wind farm. This paper analyzes the response of a wind farm for various fault conditions using a PSCAD/EMTDC simulator.