Improve System Security Research Articles

Market-clearing for pricing system security based on voltage stability criteria

This paper presents a novel technique for representing system security in the operation of decentralized electricity markets, with special emphasis on voltage stability. The market-clearing algorithm is modeled as voltage stability constrained-optimal power flow (VSC-OPF) problem for providing market solutions by means of a function of complying with the required voltage stability criteria. Benders’ decomposition is applied for solving the VSC-OPF incorporating post-contingency control actions, which is motivated by the improvement of computational efficiency using parallel processing. The proposed VSC-OPF framework also takes into consideration the bilateral contract information, which is integrated into the market-clearing process and, at the same time, the optimal pricing expressions through computing local marginal prices (LMPs) with respect to ensuring voltage stability are derived. VSC-OPF is tested on the IEEE 14-bus benchmark system and the results obtained, when compared to those obtained by means of a conventional OPF, show that the proposed technique is able to improve system security while yielding better market solutions and total transaction levels.

User security management based on trust constraint

It is very difficult to identify the malicious acts of users and to control the future acts of users for the existing static certificate-based user management in an open grid environment because of the dynamics and uncertainty of user behavior. To address the problem, a method for user security management based on trust constraints was proposed. In this method, according to the result of trust computation, the trust black-list and white-list were established by monitoring the change of trust level of users, and trust policies that stated the relationship between user trust and asset value were set. The testing results show that, as a dynamic trust constraint of access control mechanism, the trust black-list, white-list and trust policies strengthen the constraints on the system authorization, and effectively control the user behaviors by associating user's capacity accessing to resources with his or her history behaviors, which improves system security.

All shapes contiguous submesh allocation for 2D mesh multicomputers

Although contiguous allocation is known to suffer from high processor fragmentation, it is a viable allocation approach as it isolates jobs from one another, which can improve system security. Most recent contiguous allocation schemes proposed for two-dimensional meshes switch the orientation of allocation requests when allocation fails for the initial request orientation. This transformation was found to reduce processor fragmentation and improve system performance. In this paper, we propose to generalise this restricted transformation by permitting all request shapes. Using simulations, we show that this generalisation when combined with giving priority to allocating peripheral submeshes can result in significant system performance gains.

Design of a Real-Time Security Assessment Tool for Situational Awareness Enhancement in Modern Power Systems

Detailed security analysis for N-k contingencies (k = 1, 2, 3, ...) in a real-time setting is still a great challenge due to the significant computational burden. This paper takes advantage of phasor measurement units (PMUs) and decision trees (DTs) to develop a real-time security assessment tool to assess four important post-contingency security issues, including voltage magnitude violation (VMV), thermal limit violation (TV), voltage stability (VS) and transient stability (TS). The proposed scheme is tested on the Salt River Project (SRP) power system represented by a series of operating conditions (OCs) during a representative day. The properly trained DTs demonstrate excellent prediction performance. Robustness tests for the offline trained DTs are performed on a group of changed OCs that were not included for training the DTs and the idea of tuning critical system attributes for preventive controls is also presented to improve system security.

Potential benefits of implementing load management to improve power system security

This paper investigates the potential benefits provided by demand-side management programs applied in power system congested areas to improve voltage security. Congested areas are indicated by expanded modal analysis technique from a new perspective of active power variations. The study simulates the relocation of the demand from congested areas during peak periods in response to price signals. A contingency analysis is also presented. All simulations are tested in a real-life Brazilian system. The results show that this can be an efficient strategy to improve system security and prevent possible blackouts, making more efficient usage of system resources.

The Problems and Ways of Improving System Security Industry

The Problems and Ways of Improving System Security Industry

Optimal wind–battery coordination in a power system using evolutionary iteration particle swarm optimisation

An evolutionary iteration particle swarm optimisation (EIPSO) approach for optimal wind–battery coordination in a power system is proposed. The up-spinning reserve and down-spinning reserve are introduced into the wind–battery coordination problem to improve system security and the wind utilisation factor. The optimal operating schedule for a battery energy storage system (BESS) and thermal unit was reached while minimising the total operating cost. Taiwan Power Company System is used as a numerical example to test the new algorithm. The feasibility of the new algorithm is demonstrated by the numerical example, and the EIPSO solution quality and computation efficiency are compared with those of other algorithms. The results are used to evaluate the effects of the wind turbine generator and BESS on power system operations.

Attack Distribution Modeling and Its Applications in Sensor Network Security

Defending against attack is the key successful factor for sensor network security. There are many approaches that can be used to detect and defend against attacks, yet few are focused on modeling attack distribution. Knowing the distribution models of attacks can help system estimate the attack probability and thus defend against them effectively and efficiently. In this paper, we use probability theory to develop a basic uniform model, a basic gradient model, an intelligent uniform model and an intelligent gradient model of attack distribution in order to adapt to different application environments. These models allow systems to estimate the attack probability of each node under a given position and time. Applying these models in system security designs can improve system security performance and decrease the overheads in nearly every security area. Based on these models, we describe a novel probability secure routing algorithm that is effective to defend against attacks whether they are detected or not. Besides this application, we also introduce some other applications, such as secure routing that can save systems available energy and resources while still providing enough security, detecting attack, and key management.

An OPF based approach for assessing the minimal reactive power support for generators in deregulated power systems

Reactive power support is an important ancillary service for secure and reliable operation in power markets. It has recently been recognized that the reactive power support for a generator has two components: one for supporting its own real power transmission and the other for supplying reactive demand, improving system security, and controlling system voltage; and that only the second part should receive financial compensation in competitive power markets. This makes the problem of separating these two components a new focus of current research. An OPF based reactive power optimization model along with a power flow tracing based method is proposed in this paper to tackle this problem. The methodology is tested on four test systems. Detailed analysis of the results of the 39-bus test system is reported.

Valuation of reactive power support services based on sensitivity and risk analysis

In deregulated power market environment system operators need to procure adequate reactive power support services to facilitate real power transactions and improve system security. However, reactive power produced by suppliers at different locations may have different effects on the economics and operating security of the system. Thus, the assessment of the value of these reactive power support services is an important issue to be dealt with. With this objective an evaluation methodology based on voltage sensitivity and risk analysis is proposed from the perspective of voltage regulation. The IEEE 14-node test system is used to illustrate and examine the features of the proposed methodology. Some interesting results are observed and discussed.

Mobility in Distributed Systems

Mobility in Distributed Systems

An onion ring framework for developing and assessing mobile commerce security

A five-layer 'onion ring' framework for analysing mobile commerce security requirements and for improving system security performance is presented in this research. Two quantifiable approaches, based on weighted scores applied to either a spider diagram or a decision solution matrix, are used to demonstrate how the security level can actually be objectively measured and evaluated in addition to the technical discussions on the framework's architecture.

Improvement of system security with unified-power-flow controller at suitable locations under network contingencies of interconnected systems

The operation and planning of large interconnected power systems are becoming increasingly complex. To maintain security of such systems, it is desirable to estimate the effect of contingencies and plan suitable measures to improve system security/stability. The paper presents an approach for selection of unified-power-flow-controller (UPFC-) suitable locations considering normal and network contingencies after evaluating the degree of severity of the contingencies. The ranking is evaluated using composite-criteria-based fuzzy logic for eliminating masking effects. The fuzzy approach, in addition to real-power loadings and bus-voltage violations, also used voltage-stability indexes at the load buses as the post-contingent quantities to evaluate the network-contingency ranking. The selection of UPFC-suitable locations uses the criteria on the basis of improved system security/stability. The proposed approach for selection of UPFC-suitable locations has been tested under simulated conditions on a few power systems and the results for a 205-node real-life equivalent regional-power-grid system of three interconnected utility systems are presented for illustration purposes.

05/00156 Application of UPFC for system security improvement under normal and network contingencies: Visakha, K. et al. Electric Power Systems Research, 2004, 70, (1), 46–55

05/00156 Application of UPFC for system security improvement under normal and network contingencies: Visakha, K. et al. Electric Power Systems Research, 2004, 70, (1), 46–55

Application of UPFC for system security improvement under normal and network contingencies

Electric power systems are exposed to various contingencies. Network contingencies often contribute to over-loading of network branches, unsatisfactory voltages and also leading to problems of stability/voltage collapse. To maintain security of the systems, it is desirable to estimate the effect of contingencies and plan suitable measures to improve system security/stability. This paper presents an approach for selection of unified power flow controller (UPFC) suitable locations considering normal and network contingencies after evaluating the degree of severity of the contingencies. The ranking is evaluated using composite criteria based fuzzy logic for eliminating masking effect. The fuzzy approach, in addition to real power loadings and bus voltage violations, voltage stability indices at the load buses also used as the post-contingent quantities to evaluate the network contingency ranking. The selection of UPFC suitable locations uses the criteria on the basis of improved system security/stability. The proposed approach for selection of UPFC suitable locations has been tested under simulated conditions on a few power systems and the results for a 24-node real-life equivalent EHV power network and 39-node New England (modified) test system are presented for illustration purposes.

Multiobjective optimization for pricing system security in electricity markets

This paper proposes a novel technique for representing system security in the operations of decentralized electricity markets, with special emphasis on voltage stability. An interior point method is used to solve the optimal power flow problem with a multiobjective function for maximizing both social benefit and the distance to maximum loading conditions. A six-bus system with both supply and demand-side bidding is used to illustrate the proposed technique for both elastic and inelastic demand, and a 129-bus test system that models the Italian HV transmission network is used for testing the practical applicability of the proposed method. The results obtained show that the proposed technique is able to improve system security while yielding better market conditions through increased transaction levels and improved locational marginal prices throughout the system.

Application of impulsive synchronization to communication security

In this paper, criteria on uniform equi-boundedness and equi-Lagrange stability for impulsive systems are derived. These criteria are used to synchronize two nonidentical chaotic systems by impulsively controlling a nonautonomous second order system, which leads to the development of an induced-message scheme for communication system security. With the scheme, message signals are not transmitted across public channels, but induced at the receiver end. The scheme overcomes the transmission time-frame congestion in impulsive cryptosystems discussed in the literature and improves system security. Simulation results are given to demonstrate the performance of the proposed scheme.

Cyberspace security: Securing cyberspace — new laws and developing strategies

This article examines the changes proposed by EU and international initiatives to improve system security. It further considers the theme of public-private partnership underpinning emerging strategies for tackling IT security threats.

Does open source improve system security?

The current climate of functionality and performance-driven markets has created enormous code bases, which have helped drive growth in the US gross domestic product. However, these code bases have also created an information infrastructure whose vulnerabilities are so striking as to endanger national and economic security. Distributed denial of service attacks have demonstrated that such vulnerabilities can degrade the Internet's aggregate performance, and recurrent virus outbreaks have inflicted substantial repair and recovery costs on businesses worldwide. An attacker could examine public source code to find flaws in a system. So, is source code access a net gain or loss for security? The authors consider this question from several perspectives and tentatively conclude that having source code available should work in favor of system security.

Assessing the value of generator reactive power support for transmission access

The new electricity markets consider reactive power support as an essential system support service. In order to procure reactive support competitively from the markets, one needs to quantify the value of the various VAr sources available in the system. Research results are presented on the development of concepts and methodologies for equitable reactive power support valuation. Contribution to system security improvement is the main consideration for assessing the relative values of the VAr sources. The dynamic VAr support from generators is of much greater importance in the value assessment. A simple system is used first to demonstrate and define the problem. A solution method is proposed along with case study results on a large-scale power system.