scholarly journals Principal Component Analysis (PCA)-Supported Underfrequency Load Shedding Algorithm

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5896
Author(s):  
Tadej Skrjanc ◽  
Rafael Mihalic ◽  
Urban Rudez
Keyword(s):  
Principal Component ◽  
Operating Conditions ◽  
Load Shedding ◽  
Fine Tuning ◽  
System Stability ◽  
Degree Of Certainty ◽  
Conceptual Shift ◽  
Available Information ◽  
High Degree ◽  
System Frequency

This research represents a conceptual shift in the process of introducing flexibility into power system frequency stability-related protection. The existing underfrequency load shedding (UFLS) solution, although robust and fast, has often proved to be incapable of adjusting to different operating conditions. It triggers upon detection of frequency threshold violations, and functions by interrupting the electricity supply to a certain number of consumers, both of which values are decided upon beforehand. Consequently, it often does not comply with its main purpose, i.e., bringing frequency decay to a halt. Instead, the power imbalance is often reversed, resulting in equally undesirable frequency overshoots. Researchers have sought a solution to this shortcoming either by increasing the amount of available information (by means of wide-area communication) or through complex changes to all involved protection relays. In this research, we retain the existing concept of UFLS that performs so well for fast-occurring frequency events. The flexible rebalancing of power is achieved by a small and specialized group of intelligent electronic devices (IEDs) with machine learning functionalities. These IEDs interrupt consumers only when the need to do so is detected with a high degree of certainty. Their small number assures the fine-tuning of power rebalancing and, at the same time, poses no serious threat to system stability in cases of malfunction.

Under Frequency Load Shedding Techniques for Future Smart Power Systems

2019 ◽  
pp. 188-202
Author(s):  
H. H. Alhelou
Keyword(s):  
Power Systems ◽  
Power System ◽  
Active Power ◽  
Load Shedding ◽  
System Stability ◽  
Special Focus ◽  
Power Demand ◽  
Synchronous Generators ◽  
Smart Power ◽  
System Frequency

It is critical for today's power system to remain in a state of equilibrium under normal conditions and severe disturbances. Power imbalance between the load and the generation can severely affect system stability. Therefore, it is necessary that these imbalance conditions be addressed in the minimum time possible. It is well known that power system frequency is directly proportional to the speed of rotation of synchronous machines and is also a function of the active power demand. As a consequence, when active power demand is greater than the generation, synchronous generators tends to slow down and the frequency decreases to even below threshold if not quickly addressed. One of the most common methods of restoring frequency is the use of under frequency load shedding (UFLS) techniques. In this chapter, load shedding techniques are presented in general but with special focus on UFLS.

scholarly journals An approach for a multi-stage under-frequency based load shedding scheme for a power system network

2020 ◽  
Vol 10 (6) ◽  
pp. 6071
Author(s):  
Mkhululi Elvis Siyanda Mnguni ◽  
Yohan Darcy Mfoumboulou
Keyword(s):  
Decision Making ◽  
Power Systems ◽  
Power System ◽  
New England ◽  
Operating Conditions ◽  
Load Shedding ◽  
Power Network ◽  
Load Demand ◽  
Multi Stage ◽  
System Frequency

The integration of load shedding schemes with mainstream protection in power system networks is vital. The traditional power system network incorporates different protection schemes to protect its components. Once the power network reaches its maximum limits, and the load demand continue to increase the whole system will experience power system instability. The system frequency usually drops due to the loss of substantial generation creating imbalance. The best method to recover the system from instability is by introducing an under-frequency load shedding (UFLS) scheme in parallel with the protection schemes. This paper proposed a new UFLS scheme used in power systems and industry to maintain stability. Three case studies were implemented in this paper. Multi-stage decision-making algorithms load shedding in the environment of the DIgSILENT power factory platform is developed. The proposed algorithm speeds-up the operation of the UFLS scheme. The load shedding algorithm of the proposed scheme is implemented as a systematic process to achieve stability of the power network which is exposed to different operating conditions. The flexibility of the proposed scheme is validated with the modified IEEE 39-bus New England model. The application of the proposed novel UFLS schemes will contribute further to the development of new types of engineers.

scholarly journals WAMS-Based Online Disturbance Estimation in Interconnected Power Systems Using Disturbance Observer

2019 ◽  
Vol 9 (5) ◽  
pp. 990 ◽  
Author(s):  
Hassan Haes Alhelou ◽  
Mohamad Hamedani Golshan ◽  
Takawira Njenda ◽  
Pierluigi Siano
Keyword(s):  
Power Systems ◽  
Power System ◽  
Disturbance Observer ◽  
Load Shedding ◽  
System Stability ◽  
Main Stage ◽  
Estimation Errors ◽  
Disturbance Estimation ◽  
System Frequency ◽  
Swing Equation

In the event of a generator loss or disturbance, the power system frequency declines quickly and overall system stability is at risk. During these scenarios, under frequency load shedding is triggered to restore the power system frequency. The main stage of modern adaptive under frequency load shedding techniques is disturbance estimation. However, the swing equation is widely used in disturbance estimation but has some critical estimation errors. In this paper, instead of using the swing equation we proposed the use of a disturbance observer to estimate the curtailed power. By making use of wide area measurements, a system frequency response model, which is a representative of the whole power system, can be realized in real time. Using different power system states of the developed model, a disturbance observer can be designed as well. The main advantage of the disturbance observer is that it can accurately estimate the disturbance magnitude and its location in a very short time. Further investigations show that by using the disturbance observer disturbances, which occur at the same time or at different times in different areas regardless of the magnitude or size, accurate estimations can be made. To ascertain the efficiency of the proposed scheme, simulations are done for a four-area power system using Matlab/Simulink.

scholarly journals WAMS-Supported Power Mismatch Optimization for Secure Intentional Islanding

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2790
Author(s):  
Jovancho Grozdanovski ◽  
Rafael Mihalic ◽  
Urban Rudez
Keyword(s):  
Power System ◽  
Real World ◽  
Electric Power System ◽  
Load Shedding ◽  
Fine Tuning ◽  
System Stability ◽  
Mixed Integer ◽  
Programming Approach ◽  
Controlled Islanding ◽  
System Integrity

It is expected that a coordinated operation of several system integrity protection schemes will become a necessity in the future. This research represents an innovative strategy for coordinating under-frequency load shedding and intentional controlled islanding schemes for improving electric power system stability and resilience. In the great majority of real-world cases, both approaches follow conventional tactics, i.e., disconnecting a fixed number of feeders at predefined frequency thresholds and isolating a predefined area of a power system regardless of the actual conditions. Under the newly arisen network conditions in which weather-dependent distributed energy sources introduce a significant level of intermittency, conventional approaches need to be upgraded in order to retain a high level of power system operation security. In this paper, a mixed-integer linear programming approach is used to adjust the island size, including/excluding additional substations according to the available amount of generation in the region. The fine-tuning of the power rebalancing is achieved by potentially blocking selected load shedding stages. This minimizes the power imbalance of the newly formed islands, which helps to reduce the number of partial or even total blackouts and also accelerates the power system’s restoration process. The optimization approach was tested on a generic IEEE 39-bus network and shows promising results along with the capability of coping with real-world applications using wide-area monitoring systems as a source of real-time measurements. The results also indicated the importance of appropriate load modelling since both voltage and frequency dependence are recognized to have a significant effect on intentional controlled islanding.

Analysis of Under-frequency Load Shedding (UFLS) Relay Setting during Disturbances

2020 ◽  
Vol 3 (2) ◽  
pp. 132-135
Author(s):  
Irrine Budi Sulistiawati ◽  
Angga Budi Prastyo ◽  
Abraham Lomi ◽  
Ardyono Priyadi
Keyword(s):  
System Performance ◽  
Load Shedding ◽  
System Stability ◽  
Load Demand ◽  
On Line ◽  
System Frequency

Load changes on the system will affect the system stability itself.  Load demand that exceeds the generated power will cause the system frequency to decline. Therefore, a load shedding procedure is required to improve the frequency. This research focuses on how to design a load shedding scheme that is activated by the operation of under frequency relay. There are two scenarios to analyze the system performance with a simulation, which are losing power on line about 128 MVA and generator loss power about 192 MVA. Those scenarios result in a decrease in the system frequency to 47.48 Hz and 47.90, respectively. After the load shedding scenario is performed, the frequency became an increase in the range of 51.54 Hz and 49 Hz within a few seconds.

Investigation of Au SAMs Photoclick Derivatization by PM-IRRAS

2019 ◽  
Author(s):  
Mark Workentin ◽  
François Lagugné-Labarthet ◽  
Sidney Legge
Keyword(s):  
Cell Adhesion ◽  
Self Assembly ◽  
Materials Science ◽  
Fibroblast Cell ◽  
Fine Tuning ◽  
Chemical System ◽  
Infrared Reflection ◽  
Assembled Monolayers ◽  
One Step ◽  
High Degree

In this work we present a clean one-step process for modifying headgroups of self-assembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenone-caged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initiated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strain-promoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Furthermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irradiated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the “photoclick” methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.<br>

A psychologically-inspired fuzzy-based approach for user personality prediction in rumor propagation across social networks

2021 ◽  
pp. 1-15
Author(s):  
V. Indu ◽  
Sabu M. Thampi
Keyword(s):  
Social Networks ◽  
Factor Model ◽  
Five Factor Model ◽  
Principal Component ◽  
Common People ◽  
Rumor Propagation ◽  
Usage Patterns ◽  
User Personality ◽  
Personality Prediction ◽  
High Degree

Social networks have emerged as a fertile ground for the spread of rumors and misinformation in recent times. The increased rate of social networking owes to the popularity of social networks among the common people and user personality has been considered as a principal component in predicting individuals’ social media usage patterns. Several studies have been conducted to study the psychological factors influencing the social network usage of people but only a few works have explored the relationship between the user’s personality and their orientation to spread rumors. This research aims to investigate the effect of personality on rumor spread on social networks. In this work, we propose a psychologically-inspired fuzzy-based approach grounded on the Five-Factor Model of behavioral theory to analyze the behavior of people who are highly involved in rumor diffusion and categorize users into the susceptible and resistant group, based on their inclination towards rumor sharing. We conducted our experiments in almost 825 individuals who shared rumor tweets on Twitter related to five different events. Our study ratifies the truth that the personality traits of individuals play a significant role in rumor dissemination and the experimental results prove that users exhibiting a high degree of agreeableness trait are more engaged in rumor sharing activities and the users high in extraversion and openness trait restrain themselves from rumor propagation.

Stability of Ring-Type MEMS Gyroscopes Subjected to Stochastic Angular Speed Fluctuation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Samuel F. Asokanthan ◽  
Soroush Arghavan ◽  
Mohamed Bognash
Keyword(s):  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Microelectromechanical Systems ◽  
Damping Ratio ◽  
Operating Conditions ◽  
System Stability ◽  
System Response ◽  
Ring Type ◽  
Mems Gyroscopes ◽  
The Stability

Effect of stochastic fluctuations in angular velocity on the stability of two degrees-of-freedom ring-type microelectromechanical systems (MEMS) gyroscopes is investigated. The governing stochastic differential equations (SDEs) are discretized using the higher-order Milstein scheme in order to numerically predict the system response assuming the fluctuations to be white noise. Simulations via Euler scheme as well as a measure of largest Lyapunov exponents (LLEs) are employed for validation purposes due to lack of similar analytical or experimental data. The response of the gyroscope under different noise fluctuation magnitudes has been computed to ascertain the stability behavior of the system. External noise that affect the gyroscope dynamic behavior typically results from environment factors and the nature of the system operation can be exerted on the system at any frequency range depending on the source. Hence, a parametric study is performed to assess the noise intensity stability threshold for a number of damping ratio values. The stability investigation predicts the form of threshold fluctuation intensity dependence on damping ratio. Under typical gyroscope operating conditions, nominal input angular velocity magnitude and mass mismatch appear to have minimal influence on system stability.

Cybersecurity Standards in the Context of Operating System

2021 ◽  
Vol 54 (3) ◽  
pp. 1-36
Author(s):  
Syed Wasif Abbas Hamdani ◽  
Haider Abbas ◽  
Abdul Rehman Janjua ◽  
Waleed Bin Shahid ◽  
Muhammad Faisal Amjad ◽  
...  
Keyword(s):  
Organizational Context ◽  
Cyber Attacks ◽  
Fine Tuning ◽  
Security Vulnerabilities ◽  
Compliance Testing ◽  
Depth Analysis ◽  
Minimum Requirements ◽  
Security Standards ◽  
High Degree ◽  
Selection Of

Cyber threats have been growing tremendously in recent years. There are significant advancements in the threat space that have led towards an essential need for the strengthening of digital infrastructure security. Better security can be achieved by fine-tuning system parameters to the best and optimized security levels. For the protection of infrastructure and information systems, several guidelines have been provided by well-known organizations in the form of cybersecurity standards. Since security vulnerabilities incur a very high degree of financial, reputational, informational, and organizational security compromise, it is imperative that a baseline for standard compliance be established. The selection of security standards and extracting requirements from those standards in an organizational context is a tedious task. This article presents a detailed literature review, a comprehensive analysis of various cybersecurity standards, and statistics of cyber-attacks related to operating systems (OS). In addition to that, an explicit comparison between the frameworks, tools, and software available for OS compliance testing is provided. An in-depth analysis of the most common software solutions ensuring compliance with certain cybersecurity standards is also presented. Finally, based on the cybersecurity standards under consideration, a comprehensive set of minimum requirements is proposed for OS hardening and a few open research challenges are discussed.

scholarly journals Effect of transient processes on the switching stability of dc machines

2018 ◽  
Vol 239 ◽  
pp. 01036 ◽  
Author(s):  
Viktor Kharlamov ◽  
Pavel Shkodun ◽  
Andrey Ognevsky
Keyword(s):  
Magnetic System ◽  
Significant Proportion ◽  
Electrical Energy ◽  
Operating Conditions ◽  
Fine Tuning ◽  
Transient Processes ◽  
Rolling Stock ◽  
Electric Motors ◽  
Electric Rolling Stock ◽  
Switching Stability

Effective use of fuel and energy resources is one of the main tasks in modern industry and transport. The main directions of increasing the energy efficiency of the electric rolling stock of railways are considered in the paper. For the electric rolling stock of railways, a significant proportion of electric power consumption falls on traction needs. The consumption of electrical energy and its recovery directly depends on the proper operation and fine-tuning of the magnetic system and switching of traction electric motors of the rolling stock. The methods of testing traction electric motors currently used in railway transport do not fully correspond to their operating modes during operation. For more reliable control of their condition, a methodology for estimating the nature of the operation of traction electric motors in conditions close to real ones was proposed. Studies of the influence of transient processes on the quality of switching of traction electric motors taking into account operating conditions are carried out. Based on the results of the study, the analysis of the data obtained is carried out, and a criterion for estimating the switching stability of traction electric motors in transient operation modes is proposed. The proposed criterion allows carrying out quality control of the tuning of the magnetic system and switching of the traction electric motor, and also estimating the nature of its operation in various modes, taking into account the operating conditions.

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