scholarly journals Multiparameter Stability Analysis of Systems with Induction Motor Loads, Weak Interconnections and Series Compensation

2021 ◽  
Vol 20 ◽  
pp. 128-137
Author(s):  
JOATHAN DEVADASON ◽  
PAUL S. MOSES ◽  
MOHAMMAD A.S. MASOUM
Keyword(s):  
Induction Motor ◽  
Time Domain ◽  
Synchronous Generator ◽  
Stability Domain ◽  
Eigenvalue Analysis ◽  
Measurement Transducer ◽  
Series Compensation ◽  
System Parameters ◽  
The Stability ◽  
The Impact

Dynamic modeling and stability domain analysis of a system consisting of a synchronous generator sup-plying an induction motor load through a series compensated weak network has been carried out in this paper. The impact of X/Rratio of the feeder and generation control system parameters on the stability domain with respect to series compensation has been examined through eigenvalue calculations and time domain simulations. From the studies conducted, it was observed that the stability domain of the system with respect to series compensation depends on the grid strength in addition to the excitation system parameters. Eigenvalue analysis shows that there is a strong correlation between the exciter gain, time constants of the measurement transducer and exciter, and the series compensation level. The main contribution of this work is to reveal new bifurcations which arise in these systems which has been studied through eigenvalue analysis and time domain simulations for various combinations of system parameters.

scholarly journals Method to Evaluate the Impact of Integration of PMSG on Stability of Synchronous Generator Shaft Under Weak Grid Connection

2021 ◽  
Vol 9 ◽  
Author(s):  
Tianyi Zhang ◽  
Haifeng Wang
Keyword(s):  
Power System ◽  
Wind Power ◽  
Synchronous Generator ◽  
Connection Strength ◽  
Continuous Growth ◽  
Grid Connection ◽  
Shaft System ◽  
Ac Power ◽  
The Stability ◽  
The Impact

With the continuous growth in the amount of wind power accessed by the AC grid, the impact of the grid connection of wind-power generators with the power system has gradually increased. In this study, the subsynchronous oscillation of a synchronous generator (SG) shaft caused by the integration of direct-drive permanent-magnet synchronous generators (PMSGs) was investigated. The mechanism governing the effect of the connection strength between the PMSG and AC power system on the stability of the generator shaft system was analyzed based on the complex torque coefficient method. When the connection strength between the PMSG and AC power system weakens, the same voltage variation that occurs at the point of common coupling of the PMSG stimulates more intense power fluctuations in the PMSG, and the electrical damping injected by the PMSG into the SG increases considerably. This may cause the oscillation mode dominated by the generator shaft system to move to the right half of the complex plane, thereby reducing the stability of the generator shaft system. In addition, the evaluation process of the influence of the PMSG on the SG shaft system was summarized, and the proposed method can determine the stability of the AC power system after the integration of the PMSG. Finally, the effectiveness of the proposed method was validated via study cases, and conclusions were drawn. This method is expected to serve as a useful tool for the risk assessment of subsynchronous oscillations in wind farms.

scholarly journals Analysis of Subsynchronous Resonance Characteristics and Influence Factors in a Series Compensated Transmission System

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3282 ◽  
Author(s):  
Chengbing He ◽  
Dakang Sun ◽  
Lei Song ◽  
Li Ma
Keyword(s):  
Power Systems ◽  
Influence Factors ◽  
Eigenvalue Analysis ◽  
Analysis Method ◽  
Series Compensation ◽  
Excitation System ◽  
Torsional Mode ◽  
Subsynchronous Resonance ◽  
System Parameters ◽  
Governing System

Series capacitor compensation is used to improve the utilization of existing power systems. Subsynchronous resonance (SSR) can be caused by series compensated lines, which would lead to turbogenerator shaft breakdown. A novel approach was presented in this paper to analyze the characteristics and influence factors of SSR in a series compensated transmission system. The system model of SSR, including the various modules of the electromechanical network, was established, and the eigenvalue results under 70% series compensation level were analyzed by eigenvalue analysis method for the the institute of electrical and electronics engineers (IEEE) first benchmark model (FBM). Compared with the results of the power systems computer-aided design (PSCAD) modeling and simulation, the effectiveness of eigenvalue analysis method was proven. After that, the eigenvalue analysis method was used to study, in detail, the effects of system series compensation levels, synchronous generator parameters, speed governing system parameters, and excitation system parameters on SSR characteristics. The research results show that the series compensation level has the greatest influence on the torsional mode damping of the system. The parameters of generator reactance, speed governing system, and excitation system have some effect on the torsional mode damping. The parameters of excitation system significantly affect the low-frequency oscillation damping.

scholarly journals Stability Domain Analysis and Enhancement of Squirrel Cage Induction Generator Wind Turbines in Weak Grids

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4786
Author(s):  
Jonathan Devadason ◽  
Paul S. Moses ◽  
Mohammad A. S. Masoum
Keyword(s):  
Stability Domain ◽  
Power Grids ◽  
Induction Generator ◽  
Series Compensation ◽  
Induction Generators ◽  
Squirrel Cage ◽  
R Ratio ◽  
Space Modeling ◽  
Wide Range ◽  
The Stability

There are significant concerns regarding the stability of increased wind power generation in weak power grids. This paper investigates and improves the stability of Wind Turbine Squirrel Cage Induction Generators (WT-SCIGs) with series compensation and weak interconnections to the power grid. Detailed time-domain and state-space modeling have revealed new bifurcations and oscillatory modes for a WT-SCIG connected radially to a weak grid through a series compensated line. The stability domain analyses are carried out by computing bifurcations in the system by analyzing eigenvalues of the linearized system. The analyses demonstrate for the first time how the degree of compensation at which the Hopf bifurcation occurs depends on the X/R ratio of the line, operating slip of the induction generator, and voltage regulator parameters as well as the time delays in measurements. A new damping controller is proposed, which greatly improves the dynamic stability of the WT-SCIG and eliminates destructive Hopf bifurcations in weak grids for a wide range of series compensation. This allows for a much larger percentage of series compensation than what is usually possible, while avoiding instabilities, thereby maximizing the power transfer capability.

Using Cross-Coupling Effects for Suppression of Contact Severity

2014 ◽  
Vol 614 ◽  
pp. 48-52 ◽  
Author(s):  
Zhi Yong Shang ◽  
Talgar Shaymurat ◽  
Li Jun Xu
Keyword(s):  
Contact Surface ◽  
Cross Coupling ◽  
Stability Domain ◽  
Coupling Effects ◽  
System Parameters ◽  
The Cross ◽  
The Stability ◽  
Rotor Stiffness

In this paper the influence of cross-coupling effects on the rubbing-related dynamics of rotor/stator systems is investigated. The model considered in this paper is a 4-dof rotor/stator system which takes into account the dynamics of the stator and the deformation on the contact surface as well as the cross-coupling effects. The stability of the synchronous full annular rub solution of the model is first analyzed. Then, the cross-coupling effects on the stability of the system at different system parameters are studied. It is found that the cross-coupling effects of the rotor stiffness as well as those of the stator damping and stiffness will benefit the synchronous full annular rubs while the cross-coupling damping of the rotor will reduced the stability domain of the response and lead the system to a response with a heavier rubbing

scholarly journals Impact-Angle and Terminal-Maneuvering-Acceleration Constrained Guidance against Maneuvering Target

Aerospace ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 22
Author(s):  
Wanqing Zhang ◽  
Wanchun Chen ◽  
Wenbin Yu
Keyword(s):  
Closed Form ◽  
Linear Time ◽  
Stability Domain ◽  
Impact Angle ◽  
Generalized Solutions ◽  
Time Varying ◽  
Closed Form Solutions ◽  
Maneuvering Target ◽  
The Stability ◽  
The Impact

A new, highly constrained guidance law is proposed against a maneuvering target while satisfying both impact angle and terminal acceleration constraints. Here, the impact angle constraint is addressed by solving an optimal guidance problem in which the target’s maneuvering acceleration is time-varying. To deal with the terminal acceleration constraint, the closed-form solutions of the new guidance are needed. Thus, a novel engagement system based on the guidance considering the target maneuvers is put forward by choosing two angles associated with the relative velocity vector and line of sight (LOS) as the state variables, and then the system is linearized using small angle assumptions, which yields a special linear time-varying (LTV) system that can be solved analytically by the spectral-decomposition-based method. For the general case where the closing speed, which is the speed of approach of the missile and target, is allowed to change with time arbitrarily, the solutions obtained are semi-analytical. In particular, when the closing speed changes linearly with time, the completely closed-form solutions are derived successfully. By analyzing the generalized solutions, the stability domain of the guidance coefficients is obtained, in which the maneuvering acceleration of the missile can converge to zero finally. Here, the key to investigating the stability domain is to find the limits of some complicated integral terms of the generalized solutions by skillfully using the squeeze theorem. The advantages of the proposed guidance are demonstrated by conducting trajectory simulations.

scholarly journals Modelling and Analysis of the Epidemic Model under Pulse Charging in Wireless Rechargeable Sensor Networks

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 927
Author(s):  
Guiyun Liu ◽  
Ziyi Huang ◽  
Xilai Wu ◽  
Zhongwei Liang ◽  
Fenghuo Hong ◽  
...  
Keyword(s):  
Sensor Networks ◽  
Wireless Sensor ◽  
Threshold Values ◽  
System Parameters ◽  
Pulse Charging ◽  
Wireless Rechargeable Sensor Networks ◽  
The Stability ◽  
The Impact ◽  
The Relationship ◽  
Floquet Theorem

With the development of wireless sensor networks (WSNs), energy constraints and network security have become the main problems. This paper discusses the dynamic of the Susceptible, Infected, Low-energy, Susceptible model under pulse charging (SILS-P) in wireless rechargeable sensor networks. After the construction of the model, the local stability and global stability of the malware-free T-period solution of the model are analyzed, and the threshold R0 is obtained. Then, using the comparison theorem and Floquet theorem, we obtain the relationship between R0 and the stability. In order to make the conclusion more intuitive, we use simulation to reveal the impact of parameters on R0. In addition, the paper discusses the continuous charging model, and reveals its dynamic by simulation. Finally, the paper compares three charging strategies: pulse charging, continuous charging and non-charging and obtains the relationship between their threshold values and system parameters.

Dietary Vitamin and Stability of Oral Anticoagulation: Proposal of a Diet with Constant Vitamin K1 Content

1997 ◽  
Vol 77 (03) ◽  
pp. 504-509 ◽  
Author(s):  
Sarah L Booth ◽  
Jacqueline M Charnley ◽  
James A Sadowski ◽  
Edward Saltzman ◽  
Edwin G Bovill ◽  
...  
Keyword(s):  
Dietary Intake ◽  
Vitamin K ◽  
High Performance ◽  
Case Reports ◽  
Food Composition ◽  
Dietary Guidelines ◽  
Dietary Vitamin ◽  
Vitamin K1 ◽  
The Stability ◽  
The Impact

SummaryCase reports cited in Medline or Biological Abstracts (1966-1996) were reviewed to evaluate the impact of vitamin K1 dietary intake on the stability of anticoagulant control in patients using coumarin derivatives. Reported nutrient-drug interactions cannot always be explained by the vitamin K1 content of the food items. However, metabolic data indicate that a consistent dietary intake of vitamin K is important to attain a daily equilibrium in vitamin K status. We report a diet that provides a stable intake of vitamin K1, equivalent to the current U.S. Recommended Dietary Allowance, using food composition data derived from high-performance liquid chromatography. Inconsistencies in the published literature indicate that prospective clinical studies should be undertaken to clarify the putative dietary vitamin K1-coumarin interaction. The dietary guidelines reported here may be used in such studies.

IMPACT OF GOVERNMENT DEBT ON FINANCIAL SECURITY OF UKRAINE

2017 ◽  
Author(s):  
Olena Pikaliuk ◽  
◽  
Dmitry Kovalenko ◽  
Keyword(s):  
Economic Development ◽  
Public Debt ◽  
Positive Impact ◽  
The State ◽  
Financial Security ◽  
State Budget ◽  
The Public ◽  
Debt Security ◽  
The Stability ◽  
The Impact

One of the main criteria for economic development is the size of the public debt and its dynamics. The article considers the impact of public debt on the financial security of Ukraine. The views of scientists on the essence of public debt and financial security of the state are substantiated. An analysis of the dynamics and structure of public debt of Ukraine for 2014-2019. It is proved that one of the main criteria for economic development is the size of public debt and its dynamics. State budget deficit, attracting and using loans to cover it have led to the formation and significant growth of public debt in Ukraine. The volume of public debt indicates an increase in the debt security of the state, which is a component of financial security. Therefore, the issue of the impact of public debt on the financial security of Ukraine is becoming increasingly relevant. The constant growth and large amounts of debt make it necessary to study it, which will have a positive impact on economic processes that will ensure the stability of the financial system and enhance its security.

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