scholarly journals Analyzing the Impact of Loop Parameter Variations on the Transient Response of Second Order Voltage-Switched CP-PLL

2021 ◽  
Vol 11 (1) ◽  
pp. 6687-6690
Author(s):  
E. Ali ◽  
D. Narwani ◽  
A. M. Bughio ◽  
N. Nizamani ◽  
S. H. Siyal ◽  
...  
Keyword(s):  
Transient Response ◽  
Transient Behavior ◽  
Phase Locked Loop ◽  
Stable Operation ◽  
Loop Filter ◽  
Mixed Signal ◽  
Target Frequency ◽  
Parameter Variations ◽  
The Stability ◽  
The Impact

The analysis of the behavior of Charge Pump Phase-Locked Loop (CP-PLL) is a challenging task due to its mixed-signal architecture. Out of its two types, i.e. Current Switched CP-PLL (CSCP-PLL) and Voltage Switched CP-PLL (VSCP-PLL), the prior produces symmetrical pump currents, resulting in an appropriate transient performance to be analyzed. The loop parameters are important to set the gain, target frequency, and assure the stability of the system. The more important is the bandwidth of the loop, which is dependent on the loop filter parameters to perform stable operation and locking time. In this paper, the impact of loop parameter variations on the overall transient behavior of the system is investigated. It has been shown that loop parameters play an important role to ease the design of mixed-signal PLLs.

scholarly journals Establishing the approach to sustainability assessment of a coal mining company’s activity

2020 ◽  
Vol 13 (4) ◽  
pp. 541-549
Author(s):  
A. V. Velikoselskiy ◽  
Yu. A. Kluchnikova
Keyword(s):  
Coal Mining ◽  
Sustainability Assessment ◽  
Stable Operation ◽  
Main Task ◽  
Stability Coefficient ◽  
Assessment Index ◽  
Complex Approach ◽  
Set Up ◽  
The Stability ◽  
The Impact

High competition in the existing coal mining market has set up new landmarks in companies’ performance. Maintaining steady development of a coal mining business is the main task at all managerial levels and is supported by high sustainability level. A company’s ability to preserve stability is one of the key factors revealing stable development of a coal mining business. The need for establishing a system of a company’s sustainability indicators is determined by the necessity to estimate the company’s performance more accurately and in accordance with the objectives set. The authors of the article suggest a new complex approach to estimating a coal mining company’s sustainability. It is based on preserving stable operation under the influence of outer and inner risks. The authors explain the impact of various technical and economic indexes on a company’s activity, suggest formulas for calculating the assessment index – stability coefficient, define the limits for three areas by the value of the stability coefficient and the degree of risk elimination, calculate the sustainability of the company’s operation basing on the indicators’ actual values and the actions taken to eliminate risks per year. The approach suggested can become one of universal tools for analysis and assessment of current operation as well as for the medium-term planning. It can also be used in any coal mining company. The novelty of the approach is determined by the combination of traditional financial and economic analysis and the approach based on application of risk management system.

Statistical Analysis of Damper Seal Clearance Divergence and Impact Upon Rotordynamic Stability

2004 ◽  
Author(s):  
Joseph Tecza ◽  
Thomas Soulas ◽  
Thomas Eldridge
Keyword(s):  
Response Surface ◽  
High Speed ◽  
Statistical Technique ◽  
Design Parameters ◽  
Stable Operation ◽  
Worst Case ◽  
Compressor Design ◽  
Design Values ◽  
The Stability ◽  
The Impact

Rotordynamic stability in a high-speed, high-pressure centrifugal compressor is achieved through introducing stabilizing forces and managing destabilizing forces. It becomes the original equipment manufacturer’s (OEM) responsibility to provide sufficient stabilizing influence to ensure acceptable operational behavior. A variety of mechanisms exist to provide stability: damper bearings, de-swirl elements on seals, shunt holes and damper seals are commonly provided by the compressor manufacturer to combat instability. The application of damper seals provides a significant increase in rotordynamic stability if designed properly. A previous case study (Camatti, et. al. [1]) presented the detrimental effect of damper seal clearance divergence and seal gas pre-swirl upon predicted stability. Accurate prediction of rotordynamic stability requires knowledge of the destabilizing influences, and evaluation of the variation possible in the stability promoting elements. In particular, the damper seal can be strongly influenced by the presence of divergence in the seal-to-rotor clearance and can result in unexpected at-load behavior. One approach to ensure stable operation is to perform a “worst case” evaluation. However, this often results in excessive compromise (large seal clearance and impact on aerodynamic performance) to “eliminate” the possibility of unstable operation. A different and new approach is to define an acceptable envelope of probability. This study presents a statistical evaluation of the impact of damper seal clearance divergence, along with other compressor design parameters, and provides a method for ensuring stable operation regardless of manufacturing or operational variation. The logarithmic decrement is evaluated as a function of compressor design values and a statistical response surface is created. From the response surface and defined variation in design values, a measure of probability for instability can be obtained. Allowable parameter variation can be restricted to ensure stable operation. Three case studies will be presented where the potential for instability exists and the risk quantified using this statistical technique. Additionally, in one of these cases, test results are presented to support the analytical work.

Effect of the Thermostatic Expansion Valve Characteristics on the Stability of a Refrigeration System: Part II

2003 ◽  
Author(s):  
Amit Kulkarni ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Load Condition ◽  
Transient Behavior ◽  
System Stability ◽  
Stable Operation ◽  
Refrigeration System ◽  
Expansion Valve ◽  
System Part ◽  
Suction Line ◽  
The Stability ◽  
Experimental Bench

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge has been to limit the rise in chip temperature. In the past virtually all-commercial computers were designed to operate at temperatures above the ambient. However researchers have identified the advantages of operating electronics at low temperatures. The current research focuses on IBM’s mainframe, which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. An experimental bench was built to study the effect of variation of evaporator outlet superheat on system performance. Three different types of thermostatic expansion valves were tested in order to verify that the bulb size and bulb location have significant effect on the transient behavior of the system. Bulbs of each of the three thermostatic expansion valves were mounted at five different locations on the suction line. It was observed that the overall system stability increases as we move closer to the evaporator exit. It was also observed that there exists a region in the suction line at which the superheat variation is the least and placing the bulb at this region gives maximum stable operation of the system. This region can be defined as the minimum stable superheat point. Tests were conducted at five different load conditions 1000W, 750W, 500W, 250W and no load condition. It was observed that the system was the most stable at full load condition for all three types of valves and system stability consistently decreased as the load was decreased.

scholarly journals Research on voltage stability and control strategy of power system considering grid connected charging of electric vehicles

2021 ◽  
Vol 2121 (1) ◽  
pp. 012020
Author(s):  
Weidong Fang ◽  
Hao Lv ◽  
Yiting Jiang ◽  
Lingzhi Li
Keyword(s):  
Electric Vehicles ◽  
Energy Demand ◽  
Large Scale ◽  
Voltage Stability ◽  
Power Grid ◽  
Stable Operation ◽  
Charging Station ◽  
New Energy ◽  
The Stability ◽  
The Impact

Abstract The development of new energy vehicles is an important measure to deal with the growing energy demand and climate change. Especially in recent years, with the support of national policies and the maturity of electric vehicles(EVs) related technologies, the number of EVs has increased explosively, and the situation is very good. However, it also means that a large number of charging loads will be connected to the power grid, which will put great pressure on the safe and stable operation of the power grid. Although there have been many studies on the impact of EVs integration into modern power grid, most of the EVs load models are based on probability function and lack accuracy. Therefore, starting with the actual operation data of EVs charging station, this paper studies the influence of a large number of EVs charging loads on the static voltage stability of power grid. It is found that the charging load of large-scale EVs is added to the power grid, which significantly reduces the stability of power grid voltage, especially at the place connected to the EVs load and far away from the balance node. In addition, when the charging station adopts the time-of-use(TOU) price strategy, it can effectively improve the voltage stability of the whole network.

Mechanism and Impact of Damper Seal Clearance Divergence on the Rotordynamics of Centrifugal Compressors

2005 ◽  
Author(s):  
Thom M. Eldridge ◽  
Thomas A. Soulas
Keyword(s):  
Practical Experience ◽  
Logarithmic Decrement ◽  
Stable Operation ◽  
Recent Experience ◽  
Centrifugal Compressors ◽  
Rotor Bearing ◽  
The Subject ◽  
The Stability ◽  
Definition Of ◽  
The Impact

Damper seals (such as honeycomb and hole pattern seals) have been widely used in the turbomachinery industry to counterbalance destabilizing aerodynamic forces acting on the rotor system and to provide the necessary amount of damping for stable operation of the machine. Recent experience and research developments have focused the interest of the turbomachinery community on the dynamic characteristics of the divergent-taper damper seal. In addition to offering a review of the current literature on the subject of interest (in order to provide a comprehensive vision of the overall phenomenon), this paper extends the discussion for a better understanding of the mechanism and impact of damper seal clearance divergence on the rotordynamics of a rotor-bearing-seal system (as applied to centrifugal compressors). The analysis of a damper seal alone is insufficient to assess the influence of this component on the rotordynamic stability of a turbocompressor. This paper will show the variation of a complete rotor-bearing-seal system’s logarithmic decrement as a function of the hole pattern seal clearance divergence for a sample centrifugal compressor application, as analyzed with the proprietary, state-of-the-art rotordynamic software suite from the author’s company. This divergence-based transition of system logarithmic decrement from positive to zero (thereby implying the onset of instability) leads to the definition of a “damper seal divergence stability threshold.” Divergence in a damper seal can originate from numerous sources, including taper produced during manufacture, and pressure or thermal-driven distortion of the seal under operation. While small damper seal divergence may first produce an increase of the system logarithmic decrement, additional seal divergence has a dramatic effect on the first forward whirling mode natural frequency, as well as on the logarithmic decrement of that mode. This paper describes the analytical methods used to derive the stability of the rotor-bearing-seal system. It also presents a practical experience that stresses the necessity for a sound approach to properly evaluate the impact of a divergent damper seal on the stability of centrifugal compressors.

Impact Severity in Drive Line Systems With Backlash

2009 ◽  
Author(s):  
Stijn Boere ◽  
Amit Shukla ◽  
Rob Fey ◽  
Henk Nijmeijer
Keyword(s):  
Linear System ◽  
Numerical Simulations ◽  
Transient Response ◽  
Piecewise Linear ◽  
Transient Behavior ◽  
Degree Of Freedom ◽  
Peak Acceleration ◽  
Step Input ◽  
Piecewise Linear System ◽  
The Impact

Numerical simulations are used to study the transient behavior of a four degree-of-freedom, rotational piecewise linear system. This study focusses on the impact between bodies in a system with backlash as a result of a sudden step input and the associated transient response. The subsequent Single Sided Impacts and Double Sided Impacts are studied as a function of the amplitude of the step input and the size of the backlash. Transitions have been observed between Double Sided Impact regions and Single Sided Impact regions which agree with earlier findings. However, in this paper a more complete overview of the boundaries is given. The severity of the impacts is quantified with the peak-to-peak acceleration of the impacting bodies. Increasing the size of the step input increases the severity of the impacts. However, increasing backlash size leads to an extremum in impact severity. This is a possible explanation for seeming contradictions in literature.

Severity of Tip-Out Induced Impacts in Drive Line Systems With Backlash

2010 ◽  
Vol 5 (2) ◽  
Author(s):  
S. W. Boere ◽  
A. Shukla ◽  
R. H. B. Fey ◽  
H. Nijmeijer
Keyword(s):  
Linear System ◽  
Numerical Simulations ◽  
Transient Response ◽  
Piecewise Linear ◽  
Transient Behavior ◽  
Degree Of Freedom ◽  
Peak Acceleration ◽  
Step Input ◽  
Piecewise Linear System ◽  
The Impact

Numerical simulations are used to study the transient behavior of a four degree-of-freedom, rotational piecewise linear system. This study focuses on the impact between bodies in a system with backlash as a result of a sudden step input and the associated transient response. The subsequent single sided impacts and double sided impacts are studied as a function of the amplitude of the step input and the size of the backlash. Transitions have been observed between double sided impact regions and single sided impact regions, which agree with earlier findings. However, in this paper a more complete overview of the boundaries is given. The severity of the impacts is quantified with the peak-to-peak acceleration of the impacting bodies. The increase in the size of step input increases the severity of the impacts. However, the increase in backlash size leads to an extremum in impact severity. This is a possible explanation for seeming contradictions in literature.

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.

Financial Risks of the Bank: Assessment and Mechanism of Neutralization

2020 ◽  
Vol 22 (1) ◽  
pp. 6-12
Author(s):  
Nelia Volkova ◽  
◽  
Alina Mukhina ◽  
Keyword(s):  
Risk Assessment ◽  
Financial Stability ◽  
Financial Risk ◽  
Stable Operation ◽  
Financial Risks ◽  
Negative Consequences ◽  
Conceptual Approach ◽  
Relevant Today ◽  
Banking Institution ◽  
The Impact

Abstract. Introduction. The issue of financial risk management of commercial banks is quite relevant today, because the activity of banks is the most risky of all. The presence of risks in banking can lead to unexpected losses, namely the loss of own resources. That’s why for the stable operation of the bank without loss the priority is to assess the financial risks, which is the basis for their further neutralization. Purpose. The purpose of the article is to develop conceptual provisions for assessment financial risks and justifying the need to neutralize them. Results. The article analyzes the impact of risks on the financial stability of a banking institution. The main methods of bank risk assessment are considered. All these include the statistical method, the analytical method, the expert method, the analogue method and the combined method. The necessity of neutralization of financial risks in order to avoid negative consequences is substantiated. Also the methods of bank risks neutralization are considered. It should be noted that these methods of neutralization can not only be used, but also supplement the list with new methods must be done, which in the future will protect the bank from the influence of undesirable factors. A conceptual approach to the assessment and neutralization of financial risks is proposed. This conceptual approach aims to ensure effective assessment of the level of risk with their subsequent neutralization Conclusions. Use of a conceptual approach will allow an effective risk assessment and decision-making to avoid or accept risk. Thanks to using this approach, the banking institution will be able to react swiftly to the presence of financial risks and to prevent the occurrence of negative consequences, which may lead to a violation of the financial stability of the bank.

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