Allowing vanishing stability margins in preservation of (i)ISS dissipation inequalities by scaling

2016 ◽  
Author(s):  
Hiroshi Ito
Keyword(s):  
Stability Margins ◽  
Dissipation Inequalities

scholarly journals Electric Vehicles in Jordan: Challenges and Limitations

2021 ◽  
Vol 13 (6) ◽  
pp. 3199
Author(s):  
Laith Shalalfeh ◽  
Ashraf AlShalalfeh ◽  
Khaled Alkaradsheh ◽  
Mahmoud Alhamarneh ◽  
Ahmad Bashaireh
Keyword(s):  
Electric Vehicles ◽  
Distribution System ◽  
Distribution Systems ◽  
Environmental Benefits ◽  
System Stability ◽  
Loading Conditions ◽  
Stability Margins ◽  
High Penetration ◽  
Node Distribution ◽  
The Impact

An increasing number of electric vehicles (EVs) are replacing gasoline vehicles in the automobile market due to the economic and environmental benefits. The high penetration of EVs is one of the main challenges in the future smart grid. As a result of EV charging, an excessive overloading is expected in different elements of the power system, especially at the distribution level. In this paper, we evaluate the impact of EVs on the distribution system under three loading conditions (light, intermediate, and full). For each case, we estimate the maximum number of EVs that can be charged simultaneously before reaching different system limitations, including the undervoltage, overcurrent, and transformer capacity limit. Finally, we use the 19-node distribution system to study these limitations under different loading conditions. The 19-node system is one of the typical distribution systems in Jordan. Our work estimates the upper limit of the possible EV penetration before reaching the system stability margins.

Structural Optimization of Cantilever Mechanical Elements

1986 ◽  
Vol 108 (4) ◽  
pp. 427-433 ◽  
Author(s):  
Eugene I. Rivin
Keyword(s):  
Structural Optimization ◽  
Natural Frequencies ◽  
Superior Performance ◽  
Vibration Absorbers ◽  
Stability Margins ◽  
Dynamic Vibration ◽  
Robot Arms ◽  
Limited Effectiveness ◽  
Mass Ratios ◽  
Dynamic Vibration Absorbers

Naturally limited stiffness of cantilever elements due to lack of constraint from other structural components, together with low structural damping, causes intensive and slow-decaying transient vibrations as well as low stability margins for self-excited vibrations. In cases of dimensional limitations (e.g., boring bars), such common antivibration means as dynamic vibration absorbers have limited effectiveness due to low mass ratios. This paper describes novel concepts of structural optimization of cantilever components by using combinations of rigid and light materials for their design. Two examples are given: tool holders (boring bars) and robot arms. Optimized boring bars demonstrate substantially increased natural frequencies, together with the possibility of greatly enhanced mass ratios for dynamic vibration absorbers. Machining tests with combination boring bars have been performed in comparison with conventional boring bars showing superior performance of the former. Computer optimization of combination-type robot arms has shown a potential of 10–60 percent reduction in tip-of-arm deflection, together with a commensurate reduction of driving torque for a given acceleration, and a higher natural frequencies (i.e., shorter transients). Optimization has been performed for various ratios of bending and joint compliance and various payloads.

Optimization Method of the Multistage Axial Compressors Using CFD Simulation

2021 ◽  
pp. 2141006
Author(s):  
Grigorii Popov ◽  
Igor Egorov ◽  
Evgenii Goriachkin ◽  
Oleg Baturin ◽  
Daria Kolmakova ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Optimization Problems ◽  
Search Algorithm ◽  
Pressure Ratio ◽  
Optimization Method ◽  
Cfd Modeling ◽  
Turbine Engines ◽  
Stability Margins ◽  
Axial Compressors ◽  
Cfd Models

The current level of numerical methods of gas dynamics makes it possible to optimize compressors using 3D CFD models. However, the methods and means are not sufficiently developed for their wide application. This paper describes a new method for the optimization of multistage axial compressors based on 3D CFD modeling and summarizes the experience of its application. The developed method is a complex system of interconnected components (an effective mathematical model, a parameterizer, and an optimum search algorithm). The use of the method makes it possible to improve or provide the necessary values of the main gas-dynamic parameters of the compressor by changing the shape of the blades and their relative position. The method was tested in solving optimization problems for multistage axial compressors of gas turbine engines (the number of stages from 3 to 15). As a result, an increase in efficiency, pressure ratio, and stability margins was achieved. The presented work is a summary of a long-years investigation of the research team and aims at creating a complete picture of the obtained results for the reader. A brief description of the results of industrial compresses optimization contained in the paper is given as an illustration of the effectiveness of the developed methods.

In-Circuit Characterization of Low-Frequency Stability Margins in Power Amplifiers

2019 ◽  
Vol 67 (2) ◽  
pp. 822-833
Author(s):  
Jose Manuel Gonzalez ◽  
Nerea Otegi ◽  
Aitziber Anakabe ◽  
Libe Mori ◽  
Asier Barcenilla ◽  
...  
Keyword(s):  
Power Amplifiers ◽  
Low Frequency ◽  
Frequency Stability ◽  
Stability Margins

scholarly journals SOCP Relaxations of Optimal Power Flow Problem Considering Current Margins in Radial Networks

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3164 ◽  
Author(s):  
Yuwei Chen ◽  
Ji Xiang ◽  
Yanjun Li
Keyword(s):  
Power Systems ◽  
Power Flow ◽  
Optimal Power Flow ◽  
Additional Term ◽  
Transmission Losses ◽  
Stability Margins ◽  
Optimal Power ◽  
Second Order Cone ◽  
Convex Problem ◽  
Generation Costs

Optimal power flow (OPF) is a non-linear and non-convex problem that seeks the optimization of a power system operation point to minimize the total generation costs or transmission losses. This study proposes an OPF model considering current margins in radial networks. The objective function of this OPF model has an additional term of current margins of the line besides the traditional transmission losses and generations costs, which contributes to thermal stability margins of power systems. The model is a reformulated bus injection model with clear physical meanings. Second order cone program (SOCP) relaxations for the proposed OPF are made, followed by the over-satisfaction condition guaranteeing the exactness of the SOCP relaxations. A simple 6-node case and several IEEE benchmark systems are studied to illustrate the efficiency of the developed results.

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