• Title/Summary/Keyword: load margin

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A Study for Evaluating of Voltage Stability Margin Considering Shunt Capacitor (조상설비를 고려한 전압안정성 여유전력의 평가에 관한 연구)

  • 김세영
    • Journal of Energy Engineering
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    • v.7 no.1
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    • pp.65-72
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    • 1998
  • This paper presents a fast calculation method for evaluating of voltage stability margin (MW) using the line flow equation in polar form. Here, Line flow equations $(P_{ij},\;Q_{ij}$ are comprised of state variable, $V_i,\;{\Delta}_i,\;V_j$ and ${Delta}_j$, and line parameter, r and x. using the feature of polar coordinate, these becomes one equation with two variables, $V_j,;V_j$. Moreover, if bus j is slack or generator bus, which is specified voltage magnitude in load flow calculation, it becomes one equation with one variable $V_ i $ that is, may be formulated with the second-order equation for $V^2_i$. Therefore, multiple load flow solutions may be obtained with simple computation. The obtained load flow multiple solutions are used for evaluating of voltage stability through sensitivity analysis or its closeness. Also, the method is proposed to calculate for voltage stability margin considering shunt capacitor, which is important element for evaluating of voltage stability. The proposed method was validated to sample systems.

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On Control Strategies for BTB Converters for Enhancement of Interface Flow Margins (융통전력 여유 향상을 위한 BTB 컨버터 제어 전략 수립)

  • Ohn, Sung-Min;Song, Hwa-Chang;Jang, Byong-Hoon
    • Proceedings of the KIEE Conference
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    • 2011.07a
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    • pp.374-375
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    • 2011
  • This paper presents a method to determine parameters of BTB (back-to-back) converters in terms of the enhancement of interface flow margins. Interface flow margin is by definition a measure of how much active power can be transferred from the external areas to the study area with the fixed load demand, and it is mainly constrained by system voltage stability. BTB converters are controllable equipments with the active power flow through them, and its DC link in fact can divide the AC systems at the location and hence can reduce the fault current level. This paper first cals margin sensitivities at the nose point of F-V curves and formulates an optimization problem to update the BTB parameters to improve the margins. This procedure is repeated performed until the required margin enhancement is achieved.

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Securing Operation Margin Capacity as Coordination Control among the Power Compensation Equipments (전력보상설비의 상호 협조제어에 따른 운영여유용량의 확보)

  • Lee, Sang-Deok;Baek, Young-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.6
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    • pp.1011-1016
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    • 2010
  • It is an important issue to electric power system operations that it can reliably supply large-capacity power to consumption area as due to increasing power demand growth. For this purpose, The FACTS equipment based on Power IT technology with the existing mechanical compensators has been applied to power system. Therefore we suggest on this paper that a plan for coordination control of multiple power compensation equipment in order to increase the utilization of each facility and secure operation margin capacity. As the result of simulation, it is possible to cope actively with a suddenly changed power system. This helps greatly for the voltage stability and supply reliability in a suddenly changed power system.

초 저 소비전력 및 저 전압 동작용 FULL CMOS SRAM CELL에 관한 연구

  • 이태정
    • The Magazine of the IEIE
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    • v.24 no.6
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    • pp.38-49
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    • 1997
  • 0.4mm Resign Rule의 Super Low Power Dissipation, Low Voltage. Operation-5- Full CMOS SRAM Cell을 개발하였다. Retrograde Well과 PSL(Poly Spacer LOCOS) Isolation 공정을 사용하여 1.76mm의 n+/p+ Isolation을 구현하였으며 Ti/TiN Local Interconnection을 사용하여 Polycide수준의 Rs와 작은 Contact저항을 확보하였다. p-well내의 Boron이 Field oxide에 침적되어 n+/n-well Isolation이 취약해짐을 Simulation을 통해 확인할 수 있었으며, 기생 Lateral NPN Bipolar Transistor의 Latch Up 특성이 취약해 지는 n+/n-wellslze는 0.57mm이고, 기생 Vertical PNP Bipolar Transistor는 p+/p-well size 0.52mm까지 안정적인 Current Gain을 유지함을 알 수 있었다. Ti/TiN Local Interconnection의 Rs를 Polycide 수준으로 낮추는 것은 TiN deco시 Power를 증가시키고 Pressure를 감소시킴으로써 실현할 수 있었다. Static Noise Margin분석을 통해 Vcc 0.6V에서도 Cell의 동작 Margin이 있음을 확인할 수 있었으며, Load Device의 큰 전류로 Soft Error를 개선할수 있었다. 본 공정으로 제조한 1M Full CMOS SRAM에서 Low Vcc margin 1.0V, Stand-by current 1mA이하(Vcc=3.7V, 85℃기준) 를 얻을 수 있었다.

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A Study of TRM and ATC Determination for Electricity Market Restructuring (전력산업 구조개편에 대비한 적정 TRM 및 ATC 결정에 관한 연구)

  • 이효상;최진규;신동준;김진오
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.53 no.3
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    • pp.129-134
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    • 2004
  • The Available Transfer Capability (ATC) is defined as the measure of the transfer capability remaining in the physical transmission network for further commercial activity above already committed uses. The ATC determination s related with Total Transfer Capability (TTC) and two reliability margins-Transmission Reliability Capability (TRM) and Capacity Benefit Margin(CBM) The TRM is the component of ATC that accounts for uncertainties and safety margins. Also the TRM is the amount of transmission capability necessary to ensure that the interconnected network is secure under a reasonable range of uncertainties in system conditions. The CBM is the translation of generator capacity reserve margin determined by the Load Serving Entities. This paper describes a method for determining the TTC and TRM to calculate the ATC in the Bulk power system (HL II). TTC and TRM are calculated using Power Transfer Distribution Factor (PTDF). PTDF is implemented to find generation quantifies without violating system security and to identify the most limiting facilities in determining the network’s TTC. Reactive power is also considered to more accurate TTC calculation. TRM is calculated by alternative cases. CBM is calculated by LOLE. This paper compares ATC and TRM using suggested PTDF with using CPF. The method is illustrated using the IEEE 24 bus RTS (MRTS) in case study.

A Study on Multi Level Load Shedding Control Scheme Strategy for Stabilization of the Korean Power System (국내 전력계통 안정화를 위한 다단계 부하차단 제어전략 수립에 관한 연구)

  • Lee, Yun-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.65 no.4
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    • pp.255-261
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    • 2016
  • Korean Power System are operating a load shedding system to prevent voltage instability phenomenon caused by severe line contingencies. In order to apply the load shedding scheme should be selected a location, amount, delay time. Current load shedding system is load shedding amount that has been calculated in the steady-state analysis to load shed the total amount in first level, load shedding amount calculated in advance, it is possible to perform an unnecessary load shedding. In this paper, set a multi-level load shedding control strategy step-by-step selection of load shedding amount for the prevention of excessive load shedding. In addition, through a voltage resilience analysis of the power system by applying motor load ratio and sensitivity parameter to selection the multi level load shedding ratio and delay time. For this reason, to take advantage of the limit data of interchange power, by utilizing interface power flow data to set a multi-level load shedding control strategy for the stabilization of the Korean Power System.

A Downlink Load Control Scheme with a Dynamic Load Threshold and Virtual Coverage Management for Two-Tier Femtocell Networks

  • Kang, Chang Soon;Nguyen, Tien Dung;Kim, Junsu;Cigno, Renato Lo
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.11
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    • pp.2597-2615
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    • 2013
  • This paper proposes a dynamic downlink load control scheme that jointly employs dynamic load threshold management and virtual coverage management schemes to reduce the degree of performance degradation due to traffic overload in two-tier femtocell networks. With the proposed scheme, the downlink load in a serving macrocell is controlled with a load threshold which is adjusted dynamically depending on the varying downlink load conditions of neighboring macrocells. In addition, traffic overloading is alleviated by virtually adjusting the coverage of the overloaded serving macrocell, based on the adjusted load threshold of the serving macrocell. Simulation results show that the proposed scheme improves the performance of two-tier femtocell networks in terms of the outage probability and sum throughput. This improvement is significantly increased with appropriate values of load thresholds and with an intermediate-level adjustment of the virtual coverage area (i.e., handover hysteresis margin: HOM). Furthermore, the proposed scheme outperforms both a previously proposed load control scheme with a static load threshold and the LTE system without a HOM adjustment.

A An Experimental Study for Load Capacity and Dip Characteristic in Overhead Transmission Lines (가공송전선의 부하용량과 이도 특성에 관한 실험적 연구)

  • Kim, Sung-Duck
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.12
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    • pp.177-183
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    • 2010
  • Overhead transmission lines in domestic area have been built by several different design standards of dip and ground clearance. This paper describes an experimental study for evaluating load capacity and dip margin in overhead transmission lines. Such design standards for selection of overhead transmission conductors, dip and ground clearance, as well as electrical equipment technical standard are discussed. Based on daily load and weather data, several characteristics such as line utilization factor, load factor, conductor temperature and dip, etc. are analyzed, and compared with the specified levels of design standards. As a result, it is verified that DLR method can be a clue of the solving of the problem, for occurring in old transmission conductors which may be rarely operating below standards.

An Experimental Study on Seismic Performance of Reinforced Concrete Bridge Columns under Lateral Cyclic Load (반복 횡하중을 받는 철근콘크리트 교각의 내진성능에 관한 실험적 연구)

  • 이진옥;윤현도;황선경;류효진;나홍성;이경준
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.161-164
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    • 2003
  • This experimental investigation was conducted to examine the seismic performance of reinforced concrete bridge columns. The columns were subjected to a constant axial load and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement ($P_s$ =0.96, 1.44 per cent) and axial load ratio (0.05, 0.1, 0.2 P/$P_o$). Test results show that bridge columns with 50 per cent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behaviour. For bridge columns with axial load ratio(P/$P_o$) less than 0.2, the ratio of $M_{max}$ over $M_{aci}$, nominal moment capacity predicted by ACI 318-02 provisions, is consistently greater than 1 with approximately a 20 percent margin of safty.

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Dynamic Characteristics Control of a Step-down Chopper Using Load current Feed-forward Compensator (부하전류 전향보상기를 이용한 강압쵸퍼의 동특성 제어)

  • Chung, Chun-Byung;Chun, Ji-Yong;Jeon, Kee-Young;Han, Kyung-Hee
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2008.05a
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    • pp.66-69
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    • 2008
  • In this paper, The author present a load current feed-forward compensator by method that improve voltage controller of Step-down Chopper to get stable output voltage to sudden change of load current. To confirm the characteristicsof a presented load current feed -forward compensator compared each transfer function of whole system that load current feed-forward compensator is added with transfer function of whole system that existent voltage controller is included using Mason gains formula in Root locus and Bode diagram. As a result the pole of system is improved, extreme point of the wave and system improves, and size of peak value and phase margin of break frequency in resonance frequency confirmed that is good. Therefore, presented control technique could confirm that reduce influence by perturbation and improves stationary state and dynamic characteristics in output of Step-down Chopper.

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