scholarly journals Three-Phase Short-Circuit Current Calculation of Power Systems with High Penetration of VSC-Based Renewable Energy

Energies ◽  
2018 ◽  
Vol 11 (3) ◽  
pp. 537 ◽  
Author(s):  
◽  
◽  
Keyword(s):  
Renewable Energy ◽  
Steady State ◽  
Power Systems ◽  
Short Circuit ◽  
Power Grid ◽  
Current Source ◽  
Transient State ◽  
Experimental Tests ◽  
Short Circuit Current ◽  
High Penetration

Short-circuit current level of power grid will be increased with high penetration of VSC-based renewable energy, and a strong coupling between transient fault process and control strategy will change the fault features. The full current expression of VSC-based renewable energy was obtained according to transient characteristics of short-circuit current. Furtherly, by analyzing the closed-loop transfer function model of controller and current source characteristics presented in steady state during a fault, equivalent circuits of VSC-based renewable energy of fault transient state and steady state were proposed, respectively. Then the correctness of the theory was verified by experimental tests. In addition, for power grid with VSC-based renewable energy, superposition theorem was used to calculate AC component and DC component of short-circuit current, respectively, then the peak value of short-circuit current was evaluated effectively. The calculated results could be used for grid planning and design, short-circuit current management as well as adjustment of relay protection. Based on comparing calculation and simulation results of 6-node 500 kV Huainan power grid and 35-node 220 kV Huaisu power grid, the effectiveness of the proposed method was verified.

scholarly journals Control Method of Buses and Lines Using Reinforcement Learning for Short Circuit Current Reduction

2020 ◽  
Vol 12 (22) ◽  
pp. 9333
Author(s):  
Sangwook Han
Keyword(s):  
Reinforcement Learning ◽  
Power Systems ◽  
Large Scale ◽  
Control Method ◽  
Short Circuit ◽  
Power Grid ◽  
Short Circuit Current ◽  
Control Methods ◽  
Grid Operation ◽  
Short Circuit Currents

This paper proposes a reinforcement learning-based approach that optimises bus and line control methods to solve the problem of short circuit currents in power systems. Expansion of power grids leads to concentrated power output and more lines for large-scale transmission, thereby increasing short circuit currents. The short circuit currents must be managed systematically by controlling the buses and lines such as separating, merging, and moving a bus, line, or transformer. However, there are countless possible control schemes in an actual grid. Moreover, to ensure compliance with power system reliability standards, no bus should exceed breaker capacity nor should lines or transformers be overloaded. For this reason, examining and selecting a plan requires extensive time and effort. To solve these problems, this paper introduces reinforcement learning to optimise control methods. By providing appropriate rewards for each control action, a policy is set, and the optimal control method is obtained through a maximising value method. In addition, a technique is presented that systematically defines the bus and line separation measures, limits the range of measures to those with actual power grid applicability, and reduces the optimisation time while increasing the convergence probability and enabling use in actual power grid operation. In the future, this technique will contribute significantly to establishing power grid operation plans based on short circuit currents.

scholarly journals Voltage Stability of Power Systems with Renewable-Energy Inverter-Based Generators: A Review

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 115
Author(s):  
Nasser Hosseinzadeh ◽  
Asma Aziz ◽  
Apel Mahmud ◽  
Ameen Gargoom ◽  
Mahbub Rabbani
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
Voltage Stability ◽  
Reactive Power ◽  
Power Grid ◽  
Renewable Energy Sources ◽  
Electrical Power ◽  
System Stability ◽  
Special Issue ◽  
Synchronous Generators

The main purpose of developing microgrids (MGs) is to facilitate the integration of renewable energy sources (RESs) into the power grid. RESs are normally connected to the grid via power electronic inverters. As various types of RESs are increasingly being connected to the electrical power grid, power systems of the near future will have more inverter-based generators (IBGs) instead of synchronous machines. Since IBGs have significant differences in their characteristics compared to synchronous generators (SGs), particularly concerning their inertia and capability to provide reactive power, their impacts on the system dynamics are different compared to SGs. In particular, system stability analysis will require new approaches. As such, research is currently being conducted on the stability of power systems with the inclusion of IBGs. This review article is intended to be a preface to the Special Issue on Voltage Stability of Microgrids in Power Systems. It presents a comprehensive review of the literature on voltage stability of power systems with a relatively high percentage of IBGs in the generation mix of the system. As the research is developing rapidly in this field, it is understood that by the time that this article is published, and further in the future, there will be many more new developments in this area. Certainly, other articles in this special issue will highlight some other important aspects of the voltage stability of microgrids.

Active transport of magnesium across the isolated midgut of Hyalophora cecropia

1975 ◽  
Vol 63 (2) ◽  
pp. 313-320
Author(s):  
J. L. Wood ◽  
A. M. Jungreis ◽  
W. R. Harvey
Keyword(s):  
Steady State ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Potassium Transport ◽  
Magnesium Concentration ◽  
Magnesium Transport ◽  
Wet Weight ◽  
Net Flux ◽  
Burk Plot

1. The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 +/− 0.28 mu-equiv cm(−2) /(−1) in 8 mM-Mg2+. 2. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 mu-equiv/g wet weight of midgut tissue. 3. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. 4. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 mu-equiv cm(−1) /(−1). 5. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.

scholarly journals Barium and calcium block Bacillus thuringiensis subspecies Kurstaki delta-endotoxin inhibition of potassium current across isolated midgut of larval Manduca sexta

1988 ◽  
Vol 137 (1) ◽  
pp. 277-286 ◽  
Author(s):  
D. N. Crawford ◽  
W. R. Harvey
Keyword(s):  
Steady State ◽  
Manduca Sexta ◽  
Potassium Current ◽  
Short Circuit ◽  
Short Circuit Current ◽  
K Channel ◽  
Midgut Cell ◽  
Bt Toxin ◽  
Steady State Model ◽  
Delta Endotoxin

Ba2+ and Ca2+ prevent and reverse the Btk delta-endotoxin inhibition of the short-circuit current in isolated lepidopteran midgut. These findings support the K+ pump-leak steady-state model for midgut K+ homeostasis and the K+ channel mechanism of Bt toxin action. They provide a new tool with which to study the interactions between Bt toxin and midgut cell membranes.

scholarly journals Operating Performance of Power Systems Integrated HVDC Solution: KonTum-GiaLai Transmission System Case Considering Penetration of Renewable Energy

2020 ◽  
Vol 18 (4.2) ◽  
pp. 32
Author(s):  
Kim Hung Le ◽  
Ngoc Thien Nam Tran ◽  
Viet Tri Nguyen ◽  
The Khanh Truong ◽  
Minh Quan Duong
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
High Voltage ◽  
Short Circuit ◽  
Renewable Energy Sources ◽  
Transmission Efficiency ◽  
Transmission System ◽  
Large Power ◽  
Hvdc System ◽  
Hvdc Transmission

The increasing demand for electricity along with the development of distributed generators showed that improving transmission efficiency and reliability is an indispensable requirement in the operation of the power system. Advanced technologies need to be applied to modern power systems for purposes of conveying large power flows, mitigating the risk of faults. High-voltage direct current (HVDC) transmission is now considered an effective solution for investment in large-length power lines, replacing the conventional high-voltage alternative current (HVAC) transmission system, especially in period of increasing generation capacity due to the penetration of renewable energy sources. This study assesses the performance of the HVDC system on an actual power grid based on planning and improvement demands. The calculation results of power flows, power losses and short-circuit faults were investigated using ETAP software X  

Online Decision Support Index System Suite for Limiting Short Circuit Current

2013 ◽  
Vol 860-863 ◽  
pp. 1857-1861
Author(s):  
Li Wen Wang ◽  
Bi Qiang Tang ◽  
Ling Ling Pan ◽  
Fei Shi ◽  
Jun Liu
Keyword(s):  
Decision Support ◽  
Index System ◽  
Short Circuit ◽  
Power Grid ◽  
Short Circuit Current ◽  
Indicator System ◽  
Current Level ◽  
System Operation ◽  
On Line ◽  
The Index System

Topology adjustment is a main measure to limit short circuit current, but changes of power grid structure might bring deep impact on power system operation. Measures to limit short circuit current are difficult to apply online due to unable to completely evaluate its safety and feasibility. This paper presents an on-line decision support indicator system, which applied to evaluate online short circuit current level of power grid. Based on practical power grid model and typical cross-section, short circuit current level under the current and future maintenance mode is analyzed, decision support to limit short circuit current is given, and the effectiveness and feasibility of limiting measures are evaluated. Analysis results show that the index system is reasonable.

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