Mahmoud A. Attia

Optimal Location of Thyristor-controlled Series Compensators in Power Systems for Increasing Loadability by Genetic Algorithm

Abstract This article presents an approach to find the optimal location of thyristor-controlled series compensators in a power system to improve the loadability of its lines and minimize its total loss. Also the proposed approach aims to find the optimal number of devices and their optimal compensation levels by using a genetic algorithm taking into consideration the thermal and voltage limits. Examination of the proposed approach is carried out on a modified IEEE 30-bus system.

Genetic algorithm based approach for optimal allocation of TCSC for power system loadability enhancement

This paper presents an approach to find the optimal location of thyristor controlled series compensators (TCSC) in a power system to improve the loadability of its lines and minimize its total loss. Also the proposed approach aims to find the optimal number of devices and their optimal compensation levels by using genetic algorithm (GA) based approach with taking into consideration the thermal and voltage limits. Examination of the proposed approach is carried out on a modified IEEE 30-bus system.

Optimal location of series FACTS to improve the performance of power system with wind penetration

Wind generation connection to power system affects steady state and transient stability. Furthermore, this effect increases with the increase of wind penetration in generation capacity. In this paper, optimal location of series FACTS devices is carried out to solve the steady state problems of wind penetration. Two case studies are carried out on the modified IEEE39 bus system, one with wind reduction to 20% and the second with wind penetration increase by 50% in the two cases system suffers from outage of one generator with load in one of system buses decreased by 15%. The system suffers from minimum voltage reduction, total loss increase and violation of power and power angle limits. This paper found that series FACTS devices in certain range are able to solve these problems associated with wind penetration in power systems.

Optimal Location of Thyristor-Controlled Series Compensation and Static VAR Compensator to Enhance Steady-state Performance of Power System with Wind Penetration

Abstract Wind generation connection to power system affects steady-state and transient stability. Furthermore, this effect increases with the increase of wind penetration in generation capacity. In this article, optimal location of flexible AC transmission system devices is carried out to solve the steady-state problems of wind penetration using a genetic algorithm. Case study is carried out on modified IEEE 39-bus system with wind penetration increases by 50%; the system suffers from outage of one generator with load decrease in one of system buses by 15%. The system suffers from minimum voltage reduction, total loss increase, and violation of power and power angle limits. Series and shunt flexible AC transmission system devices are used in this article. Results showed that series flexible AC transmission system devices in certain range are able to solve these problems associated with wind penetration in power systems with acceptable cost saving.

Comprehensive Survey on Dynamic Graph Models

Most of the critical real-world networks are con-tinuously changing and evolving with time. Motivated by the growing importance and widespread impact of this type of networks, the dynamic nature of these networks have gained a lot of attention. Because of their intrinsic and special characteristics, these networks are best represented by dynamic graph models. To cope with their evolving nature, the representation model must keep the historical information of the network along with its temporal time. Storing such amount of data, poses many problems from the perspective of dynamic graph data management. This survey provides an in-depth overview on dynamic graph related problems. Novel categorization and classification of the state of the art dynamic graph models are also presented in a systematic and comprehensive way. Finally, we discuss dynamic graph processing including the output representation of its algorithms.

Impact of load models on the static and dynamic performances of grid-connected wind power plants: A comparative analysis

Abstract The integration of renewable energy technologies in power systems causes a significant change in the electromechanical, and electromagnetic properties of the hosting systems. Consequently, the overall steady state, and dynamic performances of power systems are altered due to the presence of these technologies. Therefore, the conclusions derived from the conventional system structures need to be updated. Recently, wind energy presented a worldwide major source of renewable energy. The performance of the generating subsystem is not only affected by the technologies of the generators, but also by the dynamics of the network and load components. Since the majority of network components is passive elements, the loads present the most impacting subsystems on the performance of power systems. Investigation of the impact of load models on the performance of power systems hosting wind energy is the main objective of this paper. This paper presents a detailed analysis of the steady state and dynamic performances of power systems as affected by popular WECTs, and composite load structures and models. The results are compared with the performances of the conventional synchronous generators. The results presented in the paper provide evidences of the strengths and weaknesses in power systems caused by the presence of various WECTs. In addition, the results show the levels of capability of various WECTs to match the classical distinct performances of conventional synchronous generators.

Application of Different Optimization Techniques to Load Frequency Control with WECS in a Multi-Area System

Abstract This article presents a load frequency control in a two-area interconnected system under wave energy disturbance. At steady state, the system frequency is maintained at the nominal value so there is no frequency deviation. Also, there is no deviation in the tie line power from the value at steady state. But increasing and decreasing of load in any of the two areas may affect the system frequency. Renewable energy variation also can affect the frequency deviation. In this article, first two controllers are used to enhance the system stability during the load change. These controllers are proportional-integral-derivative (PID) and proportional-integral-derivative and acceleration (PIDA). Three optimization techniques are presented in this article to tune the controllers’ parameters. The optimization techniques are teaching-learning-based-optimization (TLBO), harmony search algorithm (HS) and sine-cosine algorithm (SCA). PIDA and TLBO have been proved the best performance during the transient period. The system is then subjected to a disturbance in the form of wave energy conversion system (WECS) when it is equipped with PIDA and using TLBO technique.AbstractThis article presents a load frequency control in a two-area interconnected system under wave energy disturbance. At steady state, the system frequency is maintained at the nominal value so...

Modeling Sequence of Snapshots in Dynamic Graph

There is a significant research interest in representing evolving networks in the form of graph models. Most of the existing models use data structures to store sequence of snapshots, which are either historical or retrieved for processing purposes. Despite consuming minimal update time, these data structures induce storage redundancy, since consecutive snapshots share most of their nodes and edges in common. Compressed variants reduce this redundancy, but at the cost of increasing the update time, required to insert a new snapshot into the structure. So there is a tradeoff between storage and update time. In this paper we address the problem of storing sequence of snapshots in a compact manner while maintaining a very low update overhead. We minimize the update time by limiting the size of data that will undergo the update process. This is accomplished by separating the parts susceptible to change, from the other parts. Our experiments show that the proposed data structure achieves a compression, which is comparable to the state of the art methods, while offering an unprecedented low update overhead.

A Parallel Snapshot Retrieval Technique for MG

Retrieving historical information in a short time is a crucial objective in dynamic graphs. Some of the existing dynamic graph models use log-files to store the graph evolution history. These log-files store the history as a set of events sorted by their occurrence time. For answering a historical query on these models, the snapshot at the given historic time instant must be constructed first. Since the log-file events are sorted by time, the construction of a historical snapshot mandates that all events must be parsed and applied till the target time. Thus, the snapshot construction consumes a lot of time. However, these models provide accurate results. That is why, it is of a significant importance to provide accurate and fast results. In this paper, we present a log-file structure that is able to efficiently handle both accuracy and performance.