Journal articles: 'Voltage stability limit'

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Anichebe, I. B., and A. O. Ekwue. "Improvement of bus voltage profiles of Nigerian power network in the presence of Static Synchronous Compensator (STATCOM) and Doubly Fed Induction Generator (DFIG)." Nigerian Journal of Technology 39, no. 1 (April 3, 2020): 228–37. http://dx.doi.org/10.4314/njt.v39i1.26.

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Frequent blackouts and unstable supply of electricity show that the voltage instability problem has been one of the major challenges facing the power system network in Nigeria. This study investigates the voltage stability analysis of the Nigerian power network in the presence of renewable energy sources; FACTS device is used as a voltage controller. A 330kV, 28-bus power system network was studied using the PSS/E software-based Newton-Raphson load-flow technique. The results show that 10 out of the 28 buses had voltages lying below the statutory limit of 0.95 ≤ 1.05 p.u. The application of STATCOM and DFIG devices on two of the weakest buses restored the voltages to acceptable statutory limits. The total active and reactive power losses were reduced to 18.76% and 18.82% respectively. Keywords: Voltage stability analysis; Integration of renewable energy sources; FACTS controllers, Reactive Power, Power Flow.

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Sundaravazhuthi*, V., Dr A. Alli Rani, and M. Manoj Kumar. "Raise Voltage Stability Limit of a Power System using Reactive Power Compensation Technique." International Journal of Innovative Technology and Exploring Engineering 8, no. 12 (October 30, 2019): 2931–34. http://dx.doi.org/10.35940/ijitee.k1752.1081219.

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In recent years, voltage stability problems have been increasing since power systems operate close to stability limits. The voltage stability problem of a power system is associated with a rapid voltage drop due to heavy system load and it occurs because of inadequate reactive power support at some critical bus. One of the serious consequences of the voltage stability is a system blackout, and this has received more attention in recent years. Accurate determination of stability limit and amount of reactive power injection to stabilize is important.This paper proposes to determine voltage stability margin of a critical bus and also provide amount of reactive power injection to the bus particularly during overload, a simple two bus equivalent model of the power system is used to determine the maximum apparent power for different power factors. Any required apparent power can directly obtained by correcting the reactive power at critical bus. Experimental results support our theoretical findings.

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Toyoda, Junichi, Be-fei Fang, and Hiroumi Saitoh. "Bifurcation of Voltage Stability Limit in Direct Computational Approach." IEEJ Transactions on Power and Energy 115, no. 6 (1995): 576–81. http://dx.doi.org/10.1541/ieejpes1990.115.6_576.

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Obadina, O. O., and G. J. Berg. "Determination of voltage stability limit in multimachine power systems." IEEE Transactions on Power Systems 3, no. 4 (1988): 1545–54. http://dx.doi.org/10.1109/59.192964.

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Liu, Bing, Ying Wang, Zhen Yang, Yun Wei Li, Hua Zhi Xie, Yan Zhang, Wen Chao Zhang, Xiang Yang Deng, and Cheng Ming He. "Evaluation Method of Voltage Stability Based on Minimum Singular Value." Applied Mechanics and Materials 511-512 (February 2014): 1128–32. http://dx.doi.org/10.4028/www.scientific.net/amm.511-512.1128.

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When the system reaches the static voltage stability limit point, Jacobian matrix is singular. By checking if minimum singular value is zero, its very easy to determine whether or not Jacobian matrix is singular. So the minimum singular value of Jacobian matrix can reflects the degree of system voltage stability effectively. Firstly this paper introduces singular value decomposition, analyses load characteristic and excitation limits involved in this method and examples on PSD-FDS are demonstrated. At last, suggestion on voltage stability monitoring by minimum singular value is proposed.

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Saeed, Wafaa, and Layth Tawfeeq. "Voltage Collapse Optimization for the Iraqi Extra High Voltage 400 kV Grid based on Particle Swarm Optimization." Iraqi Journal for Electrical and Electronic Engineering 13, no. 1 (June 1, 2017): 17–31. http://dx.doi.org/10.37917/ijeee.13.1.3.

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The continuously ever-growing demand for the electrical power causing the continuous expansion and complexity of power systems, environmental and economic factors forcing the system to work near the critical limits of stability, so research's stability have become research areas worthy of attention in the resent day. The present work includes two phases: The first one is to determine the Voltage Stability Index for the more insensitive load bus to the voltage collapse in an interconnected power system using fast analyzed method based on separate voltage and current for PQ buses from these of PV buses, while the second phase is to suggested a simulated optimization technique for optimal voltage stability profile all around the power system. The optimization technique is used to adjust the control variables elements: Generator voltage magnitude, active power of PV buses, VAR of shunt capacitor banks and the position of transformers tap with satisfied the limit of the state variables (load voltages, generator reactive power and the active power of the slack bus). These control variables are main effect on the voltage stability profile to reach the peak prospect voltage stable loading with acceptable voltage profile. An optimized voltage collapse based on Particle Swarm Optimization has been tested on both of the IEEE 6 bus system and the Iraqi Extra High Voltage 400 kV Grid 28 bus. To ensure the effectiveness of the optimization technique a comparison between the stability indexes for load buses before and after technical application are presented. Simulation results have been executed using Matlab software.

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Kumar, Praveen. "Alternative Criteria of Voltage Stability Margin for the Purpose of Load Shedding." International Journal for Research in Applied Science and Engineering Technology 9, no. 10 (October 31, 2021): 201–6. http://dx.doi.org/10.22214/ijraset.2021.38194.

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Abstract: Voltage instability takes on the form of a dramatic drop of transmission system voltages, which may lead to system disruption. During the past two decades it has become a major threat for the operation of many systems and, in the prevailing open access environment, it is a factor leading to limit power transfers. The objective of this paper is to present new method of under voltage protection with maximum utilization of system capabilities.

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Ezeruigbo, E. N., A. O. Ekwue, and L. U. Anih. "Voltage Stability Analysis of Nigerian 330kV Power Grid using Static P-V Plots." Nigerian Journal of Technology 40, no. 1 (March 23, 2021): 70–80. http://dx.doi.org/10.4314/njt.v40i1.11.

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Nigeria power system has been experiencing total or partial system failures in recent times and voltage instability is a strong factor. The paper seeks to perform the voltage stability analysis, based on static P-V plots, on buses located around and within the South East zone of Nigeria. An injection group containing generators to serve as the source and a sink group as loads to be monitored are created. The generators are assumed to be within their min/max MW limits. The load is increased in the sink group as well as in the source group to maintain the same generation/load balance. Load power and bus voltages (P-V) curves are plotted on the load busbars and the first busbar to reach the voltage collapse and MW transfer limit are determined. From the results obtained, at a load of 100 MW, Makurdi bus recorded a voltage of 0.9301 pu which is already below the regulatory standards of ±5% of the nominal line voltage. It entered the region of instability at a load of 245 MW. This created a situation of system instability and a possible partial system collapse. Subsequently, at a load of 260 MW, the system clearly entered unstable region giving rise to partial system collapse of the network.

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Xing, Da Peng, Jia Li, and Da Qiang Qiu. "A New Estimation Method of Transient Voltage Stability Limit Clearing Time." Advanced Materials Research 971-973 (June 2014): 1051–54. http://dx.doi.org/10.4028/www.scientific.net/amr.971-973.1051.

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Critical clearing time index is one of the indices to assess transient voltage stability. At present it is mainly calculated based on the instantaneous value after transient voltage instability or the steady state valueafer fault clearing time. So a new method to estimate the critical clearing time is presented which is correspongding to the induction motor minimum slipvalue in the fault. It can forecasttransient voltage instability,and has higher precision comparing whithquik criterion and analytical method. The simulation results of IEEE 30-bus system verify the effectiveness of the stated method. .CLC number: TM 73 Document code: A Article ID: 000-3673(2013)00-0000-00

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Wondie, Tebeje Tesfaw, and Teshome Goa Tella. "Voltage Stability Assessments and Their Improvement Using Optimal Placed Static Synchronous Compensator (STATCOM)." Journal of Electrical and Computer Engineering 2022 (August 23, 2022): 1–12. http://dx.doi.org/10.1155/2022/2071454.

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In this paper, static voltage stability assessments and their improvement using analytical and optimization techniques with different loading scenarios are described. In this study, the 400 kV, 230 kV, and 132 kV Ethiopian electric power networks are modeled using Power System Analysis Toolbox (PSAT), and the load flow analysis is carried out using MATLAB source code. Then, different voltage stability indices, such as the user-defined advanced voltage stability index (AVSI), modified voltage stability index (MVSI), and fast voltage stability index (FVSI), are used to identify the voltage unstable buses. Besides this, particle swarm optimization (PSO) is also used to find the optimal size and placement of the Static Synchronous Compensator (STATCOM) for the most severe buses identified by voltage stability indices. The result presents three special arguments: whether the most severe buses that are ranked at the top based on the voltage stability indices are optimal buses for compensation placement or not, the voltage stability improvement, and power loss reduction with the introduction of STATCOM. Accordingly, it is observed that the weakest bus that is identified through the stability indices may not be the optimal placement of the compensation device. It is also indicated that, with the introduction of STATCOM to the optimal selected bus, the network power loss is reduced from 46.65 MW to 33.32 MW and its voltage magnitude in all buses is also improved. All bus voltages are within the IEEE standard acceptable limit.

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Suzuki, Mamoru, and Ken Masegi. "Direct Calculation of Voltage Stability Limit of Electric Power Systems." IEEJ Transactions on Power and Energy 110, no. 11 (1990): 895–902. http://dx.doi.org/10.1541/ieejpes1990.110.11_895.

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Lee, Byongjun, Hwachang Song, and Hae-Kon Nam. "Strategies to Increase Transfer Limit in Terms of Voltage Stability." IFAC Proceedings Volumes 36, no. 20 (September 2003): 33–37. http://dx.doi.org/10.1016/s1474-6670(17)34438-5.

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Suzuki, Mamoru, and Ken Masegi. "Direct calculation of voltage-stability limit of electric power systems." Electrical Engineering in Japan 111, no. 7 (1991): 40–49. http://dx.doi.org/10.1002/eej.4391110705.

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14

Trinh, Chuong Trong. "VOLTAGE STABILITY INVESTIGATION OF GRID CONNECTED WIND FARM." Science and Technology Development Journal 12, no. 8 (April 28, 2009): 38–46. http://dx.doi.org/10.32508/stdj.v12i8.2273.

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At present, it is very common to find renewable energy resources, especially wind power, connected to distribution systems. The impact of this wind power on voltage distribution levels has been addressed in the literature. The majority of this works deals with the determination of the maximum active and reactive power that is possible to be connected on a system load bus, until the voltage at that bus reaches the voltage collapse point. It is done by the traditional methods of P-V curves reported in many references. Theoretical expression of maximum power limited by voltage stability transfer through a grid is formulated using an exact representation of distribution line with ABCD parameters. The expression is used to plot PV curves at various power factors of a radial system. Limited values of reactive power can be obtained. This paper presents a method to study the relationship between the active power and voltage (PV) at the load bus to identify the voltage stability limit. It is a foundation to build a permitted working operation region in complying with the voltage stability limit at the point of common coupling (PCC) connected wind farm.

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15

Bhargavi, R. Naveena, and R. Anurup Bhargavi. "Optimal Location and Sizing of Reactive Power Compensation Devices for Voltage Stability Improvement of Radial Power Systems." ECS Transactions 107, no. 1 (April 24, 2022): 367–75. http://dx.doi.org/10.1149/10701.0367ecst.

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With the advancement in technology, the electricity demand is increasing day by day. Power supply utilities are facing the problem to expand their network owing to the problems like availability of land in urban areas and Right of Way (ROW). Due to these problems, many of the existing lines are operating nearer to their thermal stability limit. Maintaining the voltage within the limits will be a challenging task for the utilities. Increased loading of the lines is making the power system to the verge of voltage stability. Many indices are proposed in the literature for predicting the voltage stability of the system. In this paper, L-Index is used for voltage stability analysis of the radial distribution system. L-Index sensitivity method is used to the locate and size the reactive power compensation devices. The effectiveness of L-Index sensitivity method on the larger power system like IEEE-33 bus system is presented in this paper and simulation studies are performed using MATLAB/SIMULINK.

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Kim, Ryu, Ko, and Kim. "Optimal Operation Strategy of ESS for EV Charging Infrastructure for Voltage Stabilization in a Secondary Feeder of a Distribution System." Energies 13, no. 1 (January 1, 2020): 179. http://dx.doi.org/10.3390/en13010179.

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The introduction of electrical vehicle charging infrastructure including electric vehicle (EV) charger renewable energy resource at the secondary feeder in a distribution system has been increased as one of countermeasure for global environmental issues. However, the electric vehicle charging (EVC) infrastructure may act as the peak load in the distribution system, which can adversely impact on the voltage stability when the electric vehicle is quickly charged. Therefore, to keep within the limit capacity of a secondary feeder and allowable limit for the feeder voltage, this paper proposes a stabilization method by an energy storage system (ESS) control strategy at the secondary feeder to not exceed the upper limit or fall below the lower limit. In addition, this paper presents an estimation method to keep the proper standard value of the state of charge (SOC). From the simulation results, the voltage stabilization operation by the ESS should make the feeder voltages of the distribution system (secondary feeder) introduced EVC infrastructure keep better voltage conditions. In addition, the estimation method was able to keep the proper standard value confirming that the SOC of the ESS when it is in standby can be kept within the proper reference range. Therefore, it is confirmed that this strategy is an effective tool to solve the voltage problems by ESS.

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Haque, M. H. "Determination of Steady-State Voltage Stability Limit Using P-Q Curve." IEEE Power Engineering Review 22, no. 4 (April 2002): 71–72. http://dx.doi.org/10.1109/mper.2002.4312118.

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CHEN, JIANNFUH, and WEI-MING WANG. "STABILITY LIMIT AND UNIQUENESS OF VOLTAGE SOLUTIONS FOR RADIAL POWER NETWORKS." Electric Machines & Power Systems 25, no. 3 (March 1997): 247–61. http://dx.doi.org/10.1080/07313569708955736.

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Haque, M. H. "Power flow control and voltage stability limit: regulating transformer versus UPFC." IEE Proceedings - Generation, Transmission and Distribution 151, no. 3 (2004): 299. http://dx.doi.org/10.1049/ip-gtd:20040379.

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Fu, Hong Jun, Jian Hua Sun, Jing Gang Wang, and Yang Yu Hu. "The Static Voltage Stability Limit Calculation of AC/DC Hybrid Power System Based on Improved Continuation Power Flow Algorithm." Applied Mechanics and Materials 347-350 (August 2013): 1450–54. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.1450.

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With the HVDC system interconnected to power grid, the voltage stability problem of power grid has become increasingly prominent. This paper establishes the mathematical model of AC/DC hybrid power system and proposed an improved Continuation Power Flow (CPF) algorithm to calculate the static voltage stability limit of AC/DC hybrid system, the characteristics of this algorithm are as following: PQ decoupled power flow algorithm is used; Lagrange quadric interpolation is used in the process of predictor and step control; local parameter method is used in the correction. The iterations of AC/DC calculation alternate to solve power flow equations and select the step control near the critical power limit points to ensure the convergence of power flow solution. In order to verify the correctness of the proposed algorithm, this paper compares the calculation results by the improved algorithm and Matpower on the IEEE 14 bus-system. This paper calculates the static voltage stability limit of AC/DC hybrid power system under different DC control patterns of modified IEEE 14 bus-system and analyzes the impacts of different DC control pattern to the system voltage stability.

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E. Mubeen, Samina, Baseem Khan, and R. K. Nema. "Application of Unified Power Flow Controller to Improve Steady State Voltage Limit." IAES International Journal of Robotics and Automation (IJRA) 6, no. 4 (December 1, 2017): 277. http://dx.doi.org/10.11591/ijra.v6i4.pp277-285.

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<span>This paper utilizes the voltage source model of Unified Power Flow Controller (UPFC) and examines its abilities in mitigating the steady state stability margins of electric power system. It analyzes its behavior for different controls strategies and proposes the most efficient mode of controlling the controller for voltage stability enhancement. A systematic analytical methodology based on the concept of modal analysis of the modified load flow equations is employed to identify the area in a power system which is most prone voltage instability. Also to identify the most effective point of placement for the UPFC, a computer program has been developed using MATLAB. The results of analysis on 14 bus system is presented here as a case study.</span>

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Chattopadhyay, Tapan Kumar, Sumit Banerjee, and Chandan Kumar Chanda. "Voltage Stability Index of Radial Distribution Networks by Considering Distributed Generator for Different Types of Loads." International Journal of Energy Optimization and Engineering 5, no. 1 (January 2016): 1–22. http://dx.doi.org/10.4018/ijeoe.2016010101.

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The paper presents an approach on voltage stability analysis of distribution networks for loads of different types. A voltage stability index is proposed for identifying the node, which is most sensitive to voltage collapse. It is shown that the node, at which the value of voltage stability index is maximum, is more sensitive to voltage collapse. For the purpose of voltage stability analysis, constant power, constant current, constant impedance and composite load modeling are considered. Distributed generation can be integrated into distribution systems to meet the increasing load demand. It is seen that with the insertion of distributed generator (DG), load capability limit of the feeder has increased for all types of loads. By using this voltage stability index, one can measure the level of voltage stability of radial distribution systems and thereby appropriate action may be taken if the index indicates a poor level of stability. The effectiveness of the proposed method is demonstrated through two examples.

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Mbunwe, M. J., and A. O. Ekwue. "Voltage stability analysis of the Nigerian Power System using annealing optimization technique." Nigerian Journal of Technology 39, no. 2 (July 16, 2020): 562–71. http://dx.doi.org/10.4314/njt.v39i2.27.

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The paper addresses the means of overcoming the challenge posed by voltage collapse to the stability of the Nigerian electric power system. The technique applied is based on time identification algorithm elaborating, at a given grid bus, the local phasor measurements at fast sampling rate. Elements such as adjustable shunt compensation devices, generator reactive generation, transformer tap settings are optimally adjusted at each operating point to reach the objective of minimizing the voltage stability index at each individual bus as well as minimizing the global voltage stability indicator. The control elements setting were optimized and the maximum possible MVA voltage stable loading has been achieved and a best voltage profile was obtained. Results of tests conducted on a 6-bus IEEE system and a typical 28-bus Nigerian power distribution network are presented and discussed. Keywords: Special protection systems, voltage stability analysis, voltage stability limit, voltage collapse mechanism, system security

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Nappu, Muhammad Bachtiar, Ardiaty Arief, and Ainun Maulidah. "Voltage Stability Analysis of an Interconnected Power System Considering Varied Output of Wind Power Plants." Journal of Southwest Jiaotong University 56, no. 3 (June 30, 2021): 111–23. http://dx.doi.org/10.35741/issn.0258-2724.56.3.10.

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A sound power system must have voltage values at all buses that do not exceed the tolerance limit of ± 5% with small power losses. Voltage instability can be caused by interference or sudden power generation outage from the system. Indonesia's Southern Sulawesi power system has been interconnected with wind power plants located in Sidrap Regency and Jeneponto Regency. Wind speed energy used by wind power plants to generate electricity vary and not always constant. Hence, this can cause fluctuations and produce varied outputs that will affect the voltage profile and stability of the Southern Sulawesi interconnection system. Therefore, it is essential to assess the voltage stability of the Southern Sulawesi power system after the integration of Sidrap and Jeneponto WPPs. First, this study analyzes the voltage profile of the Southern Sulawesi interconnection system voltage after integrating the Sidrap wind power plants and Jeneponto Wind Power Plant during the peak day load and peak night load. Second, the study assesses the voltage stability with a varied output power of both Sidrap and Jeneponto Wind Power Plant. After integrating Sidrap and Jeneponto Wind Power Plants, the results showed that the voltage values at all system buses are stable and within the IEEE standard (between 0.95 p.u. and 1.05 p.u.). In addition, the voltages of the Southern Sulawesi power system with various outputs of both WPPs are still stable and within the IEEE standard.

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Li, Fang, and Xing Lei Chen. "Research on Impacts of FACTS on Static Voltage Stability Characteristics of AC/DC Power System." Applied Mechanics and Materials 347-350 (August 2013): 1440–44. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.1440.

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Based on the improved Continuation Power Flow algorithm, this paper investigates the impacts of FACTS on static voltage stability characteristics of AC/DC hybrid power system. This paper introduces the steady-state model of different FACTS devices, and the power flow mathematical model is established about AC/DC power system with FACTS devices. The impacts of FACTS devices with various capacities in different locations on static voltage stability are compared and analyzed. The calculation results of a four-machine two regions AC/DC power system show that FACTS are able to improve the voltage stability and the installation of SVC shunt compensation can possess a better effect to improve the system static voltage stability limit than TCSC series compensation.

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Liu, Wen Ying, and Cai Liang. "A Criticality Assessment Method for Power Transmission Lines in Power System." Applied Mechanics and Materials 446-447 (November 2013): 817–22. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.817.

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Analytic Hierarchy Process (AHP) is presented in this paper to measure the relative criticality for transmission lines, considering the changes of power system’s status about transmission lines overload, central buses voltage over-limit and transient stability. At first hierarchy structure is modeled, and then indexes of criteria Layer including transmission line overload index, central buses voltage over-limit index and transient stability index were presented. The simulation results show that, the AHP assessment method can give a full consideration to transmission lines’ function, which of huge significance for identifying critical lines and increasing the security of power system.

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Mustapha, Musa, B. U. Musa, and U. A. Beniskeikh. "Application of Differential Evolution Algorithm for Optimal Placement of UPFC for Improved Voltage Stability." European Journal of Engineering and Technology Research 1, no. 2 (July 27, 2018): 36–39. http://dx.doi.org/10.24018/ejeng.2016.1.2.156.

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The Unified Power Flow Controller (UPFC) is one of the versatile and most effective Flexible AC transmission System (FACTS) devices which can provide full dynamic control of a transmission line parameters, bus voltage, line impedance and phase angle for improved system security. However, the extent that performance of UPFC can be brought out; it’s greatly dependents upon the location of the device in the system. The present work is a Differential Evolution (DE) based algorithm for optimal placement of the UPFC device under steady state (normal, moderate and critical) conditions and is aimed at voltage profile enhancement of an interconnected power system. The proposed method is applied on an IEEE 14-bus power system which is demonstrated through MATPOWER simulation tool. The results obtained indicate that DE is robust based on the facts that the voltage profile was kept within the acceptable limit. Installing UPFC in the optimal location determined by DE can significantly enhance the security of power system through improvement of bus voltage limit violations.

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Mangaiyarkarasi, S. P., and T. Sree Renga Raja. "PSO Based Optimal Location and Sizing of SVC for Novel Multiobjective Voltage Stability Analysis during N – 2 Line Contingency." Archives of Electrical Engineering 63, no. 4 (December 11, 2014): 535–50. http://dx.doi.org/10.2478/aee-2014-0037.

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Abstract In this paper voltage stability is analysed based not only on the voltage deviations from the nominal values but also on the number of limit violating buses and severity of voltage limit violations. The expression of the actual state of the system as a numerical index like severity, aids the system operator in taking better security related decisions at control centres both during a period of contingency and also at a highly stressed operating condition. In contrary to conventional N – 1 contingency analysis, Northern Electric Reliability Council (NERC) recommends N – 2 line contingency analysis. The decision of the system operator to overcome the present contingency state of the system must blend harmoniously with the stability of the system. Hence the work presents a novel N – 2 contingency analysis based on the continuous severity function of the system. The study is performed on 4005 possible combinations of N – 2 contingency states for the practical Indian Utility 62 bus system. Static VAr Compensator is used to improve voltage profile during line contingencies. A multi- objective optimization with the objective of minimizing the voltage deviation and also the number of limit violating bus with optimal location and optimal sizing of SVC is achieved by Particle Swarm Optimization algorithm.

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Badrudeen, Tayo Uthman, Funso Kehinde Ariyo, Ayodeji Olalekan Salau, and Sepiribo Lucky Braide. "Analysis of a new voltage stability pointer for line contingency ranking in a power network." Bulletin of Electrical Engineering and Informatics 11, no. 6 (December 1, 2022): 3033–41. http://dx.doi.org/10.11591/eei.v11i6.4266.

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Improper management of reactive power in a power network could lead to voltage instability. This paper presents a well-detailed study on voltage instability due to violation of power equilibrium in a power network and introduces a new voltage stability pointer (NVSP). The proposed NVSP is developed from a reduced 2-bus interconnected network to predict the sensistivity of voltage stability to reactive power variation. The simulation results from MATLAB were evaluated on IEEE 14-bus test system. The contingency ranking was achieved by varying the reactive power on the load buses to its maximum loading limit. The maximum reactive power point was taken at each load bus and the critical lines were ranked according to their vulnerability to voltage collapse. The results were compared with other notable voltage stability indices. The results prove that the NVSP is an essential tool in predicting voltage collapse.

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Hossain, M. J., H. R. Pota, M. A. Mahmud, and R. A. Ramos. "Excitation control for improving transient stability limit and voltage regulation with dynamic loads." IFAC Proceedings Volumes 44, no. 1 (January 2011): 4971–76. http://dx.doi.org/10.3182/20110828-6-it-1002.00991.

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Kataoka, Yoshihiko, and Yukio Shinoda. "Voltage Stability Limit of Electric Power System with Reactive Power Constraints on Generators." IEEJ Transactions on Power and Energy 123, no. 6 (2003): 704–17. http://dx.doi.org/10.1541/ieejpes.123.704.

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Haque, M. H. "A fast method for determining the voltage stability limit of a power system." Electric Power Systems Research 32, no. 1 (January 1995): 35–43. http://dx.doi.org/10.1016/0378-7796(94)00893-9.

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Kataoka, Y., and Y. Shinoda. "Voltage Stability Limit of Electric Power Systems With Generator Reactive Power Constraints Considered." IEEE Transactions on Power Systems 20, no. 2 (May 2005): 951–62. http://dx.doi.org/10.1109/tpwrs.2005.846080.

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M, Sinan, Sivakumar W M, and Anguraja R. "Power System Voltage Stability analysis with Renewable power Integration." International Journal of Innovative Technology and Exploring Engineering 10, no. 6 (April 30, 2021): 114–17. http://dx.doi.org/10.35940/ijitee.f8828.0410621.

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The purpose of this research is to find the loading limit of a power system before hitting voltage instability and to assess the margin to voltage instability of a system consisting of a wind farm. An index called Bus Apparent Power Difference Criterion (BSDC) is used to find maximum loadable point. The measure depends on the way that in the region of the voltage collapse no extra apparent power can be delivered to the affected bus. The analysis is performed combination of wind power injection at different wind speeds and line outages in the network. In the feasibility and siting studies of wind farms the steady state analysis with network contingencies give the utility or the developer a sense of network condition upon the injection of power in the network. However, the extent of voltage stability impacted due to load growth in the system is not assessed. The research paper makes way to assess the impact on voltage stability margin with obtaining the maximum loadable point of the system and assessing the best suited bus to integrate a wind farm into the system.

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Innah, Herbert, and Takashi Hiyama. "A New Method for Online Assessment of Voltage Stability." Advanced Materials Research 433-440 (January 2012): 7170–74. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.7170.

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In this paper we proposed a new technique for identifying system stress due to the loading in wide area of power system based on the phasor angle difference behavior. The difference of voltage phasor angle between busses can be transferred in to a simple conversion and trigonometric wave signal during load increasing. Using Discrete Fourier Transform (DFT), the signal will be transformed into the spectral frequency. The proposed technique will analyzed current condition by visualized the level of stress and proximity to voltage stability limit in the system based on the change of spectral frequency . This method also can be used to monitor such loss of generators or transmission line outages. The result shown that the proposed technique is simple, fast and reliable, requiring minimum data measurement and be suitable for Wide Area Monitoring System.

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Adni Binti Mat Le, Nor, W. Mohd Nazmi bin W Musa, Nurlida Binti Ismail, Nurul Huda binti Ishak, and Nur Ashida binti Salim. "The Modeling of SVC for the Voltage Control in Power System." Indonesian Journal of Electrical Engineering and Computer Science 6, no. 3 (June 1, 2017): 513. http://dx.doi.org/10.11591/ijeecs.v6.i3.pp513-519.

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One of the major causes of voltage instability in power system is the reactive power limit. Therefore, this paper aims to analyze the effect of Static Var Compensator (SVC) on voltage stability of a power system. There are many ways to control the voltage, but in this paper only focus on the SVC and IEEE-9 buses. The SVC circuit and IEEE-9 buses were designed and modelled in Power World. The Newton Raphson method was applied to compute the load flow solution. Then, the reactive power (Q) was injected to SVC and the effect of SVC on IEEE 9-buses were studied. The analysis of voltage control was considered the conditions of fault occurred at the bus. The simulation results obtained in Power World demonstrate that the improvement voltage in the IEEE 9-buses when the Q was injected into SVC circuit. Besides, the QV curve was plotted to show the sensitivity and variation bus voltages with respect to the Q injection.

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Dada, J. P., J. C. Chedjou, and S. Domngang. "Amplitude and Frequency Control: Stability of Limit Cycles in Phase-Shift and Twin-T Oscillators." Active and Passive Electronic Components 2008 (2008): 1–6. http://dx.doi.org/10.1155/2008/539618.

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We show a technique for external direct current (DC) control of the amplitudes of limit cycles both in the Phase-shift and Twin-T oscillators. We have found that amplitudes of the oscillator output voltage depend on the DC control voltage. By varying the total impedance of each oscillator oscillatory network, frequencies of oscillations are controlled using potentiometers. The main advantage of the proposed circuits is that both the amplitude and frequency of the waveforms generated can be independently controlled. Analytical, numerical, and experimental methods are used to determine the boundaries of the states of the oscillators. Equilibrium points, stable limit cycles, and divergent states are found. Analytical results are compared with the numerical and experimental solutions, and a good agreement is obtained.

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Jebaraj, Luke, Charles Christober Asir Rajan, and Kumar Sriram. "Application of Firefly Algorithm in Voltage Stability Environment Incorporating Circuit Element Model of SSSC with Variable Susceptance Model of SVC." Advances in Electrical Engineering 2014 (April 24, 2014): 1–11. http://dx.doi.org/10.1155/2014/349787.

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This paper proposes an application of firefly algorithm (FA) based extended voltage stability margin and minimization of active (or) real power loss incorporating Series-Shunt flexible AC transmission system (FACTS) controller named as static synchronous series compensator (SSSC) combined with static var compensator (SVC). A circuit model of SSSC and variable susceptance model of SVC are utilized to control the line power flows and bus voltage magnitudes, respectively, for real power loss minimization and voltage stability limit improvement. The line quality proximity index (LQP) is used to assess the voltage stability of a power system. The values of voltage profile improvement, real power loss minimization, and the location and size of FACTS devices were optimized by FA. The results are obtained from the IEEE 14- and 30-bus test case systems under different operating conditions and compared with other leading evolutionary techniques such as shuffled frog leaping algorithm (SFLA), differential evolution (DE) and particle swarm optimization (PSO).

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Kaneyama, T., M. Kawasaki, T. Tomita, T. Honda, and M. Kersker. "The information limit of a 200kv field emission TEM." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 586–87. http://dx.doi.org/10.1017/s0424820100139305.

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The Point resolution of a transmission electron microscope is normally defined by the reciprocal of the spatial frequency of the first zero in the phase contrast transfer function at the Scherzer defocus condition. When a field emission gun (FEG) is used as the electron source, the information limit, that point at which the contrast beyond the first zero goes to zero contrast, becomes equally important. We have investigated the primary microscope parameters that affect the information limit.A 200kV FE-TEM (JEM-2010F) equipped with a ZrO/W shottkey emitter and Gatan Parallel EELS (PEELS) was used for the experiments. The aberration coefficients of the objective lens are Cs = 1mm and Cc = 1.4mm. The specimen used is an evaporated amorphous Ge thin film with small gold islands.The resolution performance of the microscope depends not only on the performance of the objective lens, the high voltage stability, stability of the lens and deflector power supplies, operating parameters of the FEG, and the overall mechanical stability of the microscopes.

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Lindvall, T., K. J. Hanhijärvi, T. Fordell, and A. E. Wallin. "High-accuracy determination of Paul-trap stability parameters for electric-quadrupole-shift prediction." Journal of Applied Physics 132, no. 12 (September 28, 2022): 124401. http://dx.doi.org/10.1063/5.0106633.

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The motion of an ion in a radiofrequency (rf) Paul trap is described by the Mathieu equation and the associated stability parameters that are proportional to the rf and dc electric field gradients. Here, a higher-order, iterative method to accurately solve the stability parameters from measured secular frequencies is presented. It is then used to characterize an endcap trap by showing that the trap’s radial asymmetry is dominated by the dc field gradients and by measuring the relation between the applied voltages and the gradients. The results are shown to be in good agreement with an electrostatic finite-element-method simulation of the trap. Furthermore, a method to determine the direction of the radial trap axes using a “tickler” voltage is presented, and the temperature dependence of the rf voltage is discussed. As an application for optical ion clocks, the method is used to predict and minimize the electric quadrupole shift (EQS) using the applied dc voltages. Finally, a lower limit of 1070 for the cancellation factor of the Zeeman-averaging EQS cancellation method is determined in an interleaved low-/high-EQS clock measurement. This reduces the EQS uncertainty of our [Formula: see text]Sr[Formula: see text] optical clock to [Formula: see text] in fractional frequency units.

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Clarke-Hannaford, Jonathan, Michael Breedon, Thomas Rüther, and Michelle J. S. Spencer. "Fluorinated Boron-Based Anions for Higher Voltage Li Metal Battery Electrolytes." Nanomaterials 11, no. 9 (September 14, 2021): 2391. http://dx.doi.org/10.3390/nano11092391.

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Lithium metal batteries (LMBs) require an electrolyte with high ionic conductivity as well as high thermal and electrochemical stability that can maintain a stable solid electrolyte interphase (SEI) layer on the lithium metal anode surface. The borate anions tetrakis(trifluoromethyl)borate ([B(CF3)4]−), pentafluoroethyltrifluoroborate ([(C2F5)BF3]−), and pentafluoroethyldifluorocyanoborate ([(C2F5)BF2(CN)]−) have shown excellent physicochemical properties and electrochemical stability windows; however, the suitability of these anions as high-voltage LMB electrolytes components that can stabilise the Li anode is yet to be determined. In this work, density functional theory calculations show high reductive stability limits and low anion–cation interaction strengths for Li[B(CF3)4], Li[(C2F5)BF3], and Li[(C2F5)BF2(CN)] that surpass popular sulfonamide salts. Specifically, Li[B(CF3)4] has a calculated oxidative stability limit of 7.12 V vs. Li+/Li0 which is significantly higher than the other borate and sulfonamide salts (≤6.41 V vs. Li+/Li0). Using ab initio molecular dynamics simulations, this study is the first to show that these borate anions can form an advantageous LiF-rich SEI layer on the Li anode at room (298 K) and elevated (358 K) temperatures. The interaction of the borate anions, particularly [B(CF3)4]−, with the Li+ and Li anode, suggests they are suitable inclusions in high-voltage LMB electrolytes that can stabilise the Li anode surface and provide enhanced ionic conductivity.

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Omi, Shota, and Yasuyuki Shirai. "Modified tangent vector-based voltage stability constrained optimal power flow considering limit-induced bifurcation." IET Generation, Transmission & Distribution 14, no. 21 (November 2, 2020): 4918–26. http://dx.doi.org/10.1049/iet-gtd.2020.0784.

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Tripathy, M., and S. Mishra. "Bacteria Foraging-Based Solution to Optimize Both Real Power Loss and Voltage Stability Limit." IEEE Transactions on Power Systems 22, no. 1 (February 2007): 240–48. http://dx.doi.org/10.1109/tpwrs.2006.887968.

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Raikwal, P., V. Neema, and A. Verma. "A New 8T SRAM Circuit with Low Leakage and High Data Stability Idle Mode at 70nm Technology." Oriental journal of computer science and technology 10, no. 1 (March 22, 2017): 86–93. http://dx.doi.org/10.13005/ojcst/10.01.12.

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Memory has been facing several problems in which the leakage current is the most severe. Many techniques have been proposed to withstand leakage control such as power gating and ground gating. In this paper a new 8T SRAM cell, which adopts a single bit line scheme has been proposed to limit the leakage current as well as to gain high hold static noise margin. The proposed cell with low threshold voltage, high threshold voltage and dual threshold voltage are used to effectively reduce leakage current, and delay. Additionally, the comparison has been performed between conventional 6T SRAM cell and the new 8T SRAM cell. The proposed circuit consumes 671.22 pA leakage current during idle state of the circuit which is very less as compare to conventional 6T SRAM cell with sleep and hold transistors and with different β ratio. The proposed new 8T SRAM cell shows highest noise immunity 0.329mv during hold state. Furthermore, the proposed new 8T SRAM circuit represents minimum read and write access delays 114.13ps and 38.56ps respectively as compare to conventional 6T SRAM cell with different threshold voltages and β ratio.

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Aman, M. A., S. Ahmad, B. Noor, and F. W. Karam. "Mitigating the Adverse Impact of Un-Deterministic Distributed Generation on a Distribution System Considering Voltage Profile." Engineering, Technology & Applied Science Research 8, no. 3 (June 19, 2018): 2998–3003. http://dx.doi.org/10.48084/etasr.2033.

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Electric power systems are enforced to operate near to their stability limit due to the fast increase in power demand. Therefore, voltage stability has become a primary concern. The main cause of voltage variations is the imbalance between generation and consumption. In order to mitigate variations in voltage profile, most of the modern electric power systems are adopting new emerging technologies such as distributed generation. Validation of standard voltage optimization is a difficult task when distributed generation is integrated to medium and low voltage networks. Integration of distributed generation (DG) will have diverse impacts on voltage levels when connected un-deterministically to the electric distribution system. This paper analyzes both the impacts of un-deterministic large and small size DG on voltage profile. Feasible solutions by incorporating reactors and increasing cross sectional area of cables, variation in voltage profile were mitigated. Detailed simulations were performed in ETAP by modeling and evaluating Kohat road grid station situated in Peshawar, Pakistan. The results anticipated that this approach can be useful to ensure standard voltage profile and better utilization of un-deterministic DG units.

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Hossain, Jahangir, Apel Mahmud, Naruttam K. Roy, and Hemanshu R. Pota. "Enhancement of Transient Stability Limit and Voltage Regulation with Dynamic Loads Using Robust Excitation Control." International Journal of Emerging Electric Power Systems 14, no. 6 (October 23, 2013): 561–70. http://dx.doi.org/10.1515/ijeeps-2013-0037.

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Abstract In stressed power systems with large induction machine component, there exist undamped electromechanical modes and unstable monotonic voltage modes. This article proposes a sequential design of an excitation controller and a power system stabiliser (PSS) to stabilise the system. The operating region, with induction machines in stressed power systems, is often not captured using a linearisation around an operating point, and to alleviate this situation a robust controller is designed which guarantees stable operation in a large region of operation. A minimax linear quadratic Gaussian design is used for the design of the supplementary control to automatic voltage regulators, and a classical PSS structure is used to damp electromechanical oscillations. The novelty of this work is in proposing a method to capture the unmodelled nonlinear dynamics as uncertainty in the design of the robust controller. Tight bounds on the uncertainty are obtained using this method which enables high-performance controllers. An IEEE benchmark test system has been used to demonstrate the performance of the designed controller.

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Kumar, M., and P. Renuga. "Application of UPFC for enhancement of voltage profile and minimization of losses using Fast Voltage Stability Index (FVSI)." Archives of Electrical Engineering 61, no. 2 (June 1, 2012): 239–50. http://dx.doi.org/10.2478/v10171-012-0020-4.

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Application of UPFC for enhancement of voltage profile and minimization of losses using Fast Voltage Stability Index (FVSI)Transmission line loss minimization in a power system is an important research issue and it can be achieved by means of reactive power compensation. The unscheduled increment of load in a power system has driven the system to experience stressed conditions. This phenomenon has also led to voltage profile depreciation below the acceptable secure limit. The significance and use of Flexible AC Transmission System (FACTS) devices and capacitor placement is in order to alleviate the voltage profile decay problem. The optimal value of compensating devices requires proper optimization technique, able to search the optimal solution with less computational burden. This paper presents a technique to provide simultaneous or individual controls of basic system parameter like transmission voltage, impedance and phase angle, thereby controlling the transmitted power using Unified Power Flow Controller (UPFC) based on Bacterial Foraging (BF) algorithm. Voltage stability level of the system is defined on the Fast Voltage Stability Index (FVSI) of the lines. The IEEE 14-bus system is used as the test system to demonstrate the applicability and efficiency of the proposed system. The test result showed that the location of UPFC improves the voltage profile and also minimize the real power loss.

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Matsukawa, Watanabe, Wahab, and Othman. "Voltage Stability Index Calculation by Hybrid State Estimation based on Multi Objective Optimal Phasor Measurement Unit Placement." Energies 12, no. 14 (July 12, 2019): 2688. http://dx.doi.org/10.3390/en12142688.

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Operation of a power system close to the voltage stability limit due to increasing of load demand and limited power sources may result in disastrous economic loss with voltage collapse of the entire power system. A system operator has to understand how far the system is from the critical boundary of the voltage collapse. This paper investigated the influence of State Estimation (SE) in the calculation of the Critical Boundary Index (CBI) as a voltage stability index. For SE, Hybrid State Estimation (HSE), including the measurement set of both Remote Terminal Unit (RTU) in Supervisory Control and Data Acquisition (SCADA) and Phasor Measurement Unit (PMU), is employed. Concurrently, the CBI is estimated using voltage phasor estimated by HSE based on optimal PMU location, which is selected from a Pareto optimal front obtained by the Non-dominated Sorting Genetic Algorithm II (NSGA-II). As a result of CBI estimation, HSE using PMU is relatively accurate in voltage stability index estimation compared to SCADA SE, which uses the RTU alone. However, when a mixed measurement condition in some lines affects the CBI estimation, it is suggested that it may be necessary to discard PMU measurements in some cases.

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Allen, Scott, Vipindas Pala, E. VanBrunt, Brett Hull, Lin Cheng, S. Ryu, Jim Richmond, M. O’Loughlin, Al Burk, and J. Palmour. "Next-Generation Planar SiC MOSFETs from 900 V to 15 kV." Materials Science Forum 821-823 (June 2015): 701–4. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.701.

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A family of planar MOSFETs with voltage ratings from 900 V to 15 kV are demonstrated. This family of planar MOSFETs represents Cree’s next generation MOSFET design and process, in which we continue to refine and evolve device design and processing to further shrink die sizes and enhance device performance. At voltage ratings of 3.3 kV and above, the specific on-resistance of the MOSFETs is approaching the theoretical limit. MOSFET switching performance in a clamped inductive switching circuit for the full range of voltage ratings is also demonstrated. Finally, improved threshold voltage and body diode stability under long-term stresses are presented.

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Kang, Jin-Wook, Ki-Woong Shin, Hoon Lee, Kyung-Min Kang, Jintae Kim, and Chung-Yuen Won. "A Study on Stability Control of Grid Connected DC Distribution System Based on Second Order Generalized Integrator-Frequency Locked Loop (SOGI-FLL)." Applied Sciences 8, no. 8 (August 16, 2018): 1387. http://dx.doi.org/10.3390/app8081387.

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This paper studies a second order generalized integrator-frequency locked loop (SOGI-FLL) control scheme applicable for 3-phase alternating current/direct current (AC/DC) pulse width modulation (PWM) converters used in DC distribution systems. The 3-phase AC/DC PWM converter is the most important power conversion system of DC distribution, since it can boost 380 Vrms 3-phase line-to-line AC voltage to 700 Vdc DC output with various DC load devices and grid voltages. The direct-quadrature (d-q) transformation, positive sequence voltage extraction, proportional integral (PI) voltage/current control, and phase locked loop (PLL) are necessary to control the 3-phase AC/DC PWM converter. Besides, a digital filter, such as low pass filter and all pass filter, are essential in the conventional synchronous reference frame-phase locked loop (SRF-PLL) method to eliminate the low order harmonics of input. However, they limit the bandwidth of the controller, which directly affects the output voltage and load of 3-phase AC/DC PWM converter when sever voltage fluctuation, such as sag, swell, etc. occurred in the grid. On the other hand, the proposed control method using SOGI-FLL is able to do phase angle detection, positive sequence voltage extraction, and harmonic filtering without additional digital filters, so that more stable and fast transient control is achieved in the DC distribution system. To verify the improvement of the characteristics in the unbalanced voltage and frequency fluctuation of the grid, a simulation and experiment are implemented with 50 kW 3-phase AC/DC PWM converter used in DC distribution.

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Journal articles on the topic 'Voltage stability limit'

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