Sharif Digital Repository

In this paper, a robust sliding mode control for a flexible transmission system is presented. This system has two very oscillatory vibration modes subject to large load variation which makes the control of it be difficult. A set of design specification in time domain is to be met by a single controller on each of the three main plant models. Furthermore the tracking problem in the presence of disturbance and load variation is investigated. Results show good performance of the proposed controller. In this approach, in order to estimate the hidden states of the flexible transmission system, an observer based on sliding mode control is used. © 2004 IEEE  

This paper focuses on the sliding mode control which incorporates a fuzzy tuning technique. In this scheme, first, a control input based on classical sliding mode control is designed. Then, for performance enhancement and chattering elimination, an additional fuzzy control term is used together with the control signal. Furthermore the Lyapunov stability method is used to prove the asymptotic convergence of control strategies. To illustrate the usefulness of the proposed approach, classical and fuzzy sliding mode control are both applied to a flexible transmission system. The results verify the validity of the proposed control scheme. © 2004 IEEE  

Under new reregulation environment an open access to transmission system is desired. Transmission system operators (TSOs) are encouraged to use the existing facilities more efficiently. This paper focuses on the evaluation of the impact of FACTS devices on Available Transfer Capability (ATC) and its enhancement. Genetic algorithm is used for optimisation process of the best location of SVC as a FACTS device. Improvement of voltage profile as well as TTC enhancement is achieved by applying a proposed methodology through some case studies  

We introduce a 'high probability' framework for repeated games with incomplete information. In our non-equilibrium setting, players aim to guarantee a certain payoff with high probability, rather than in expected value. We provide a high probability counterpart of the classical result of Mertens and Zamir for the zero-sum repeated games. Any payoff that can be guaranteed with high probability can be guaranteed in expectation, but the reverse is not true. Hence, unlike the average payoff case where the payoff guaranteed by each player is the negative of the payoff by the other player, the two guaranteed payoffs would differ in the high probability framework. One motivation for this framework... 

Distributed static series compensator (DSSC) is a member of the family of distributed flexible AC transmission system devices that can be attached directly to conductors of transmission lines. DSSCs are able to compensate for and adjust the line reactance; thus, they could be widely used in stability-limited transmission systems. Owing to economic matters, the optimal placement of DSSCs is of a great interest from practical viewpoints. This study presents an approach to find the optimal locations of DSSCs to enhance the system loadability and reliability using the DC load flow model. The optimisation problem is solved using the mixed-integer linear programming. A compromise between improving... 

The present context of the electric industry, characterized by competitive markets, privatization, and regulatory of technical requirements forces the power utilities to optimize their asset management practices and develop the requisite decision plans techno-economically. Practically approaching, this paper devises a new support tool based on a multiattribute decision making (MADM) framework in combination with analytical hierarchical process (AHP) to determine the most critical components of power transmission systems. Measure of system-wide reliability performance, outage cost, marginal clearing prices demonstrative of market fairness, and network losses are among the attributes... 

In this study, a novel network reinforcement model incorporating optimal wind farms (WFs) integration to power systems is proposed. Based on the reinforcement model, new transmission lines are added to the network for eliminating the transmission network congestion. In addition, a methodology for determining the WFs optimal capacities, the economical WF lines transfer rates and the appropriate reinforcement plan, whereas maximising the total benefit using cost-reliability analysis is presented. In this way, the objective of the proposed optimisation problem has been divided into a master problem and two subproblems. Benders decomposition is employed to connect the master and subproblems of... 

A system scheme is presented, which allows non-reciprocal wave transmission or directional amplification of electromagnetic signals, using a boxed four-node method. Edges represent strong hopping interactions and diagonals stand for weak parametric interactions. Using careful optimization of values for design parameters, we are able to obtain non-reciprocity in excess of 12 and 130 dB for intrinsic and extrinsic configurations at identical input/output frequencies. For the directional amplification, an isolation as high as 40 dB is demonstrated with the forward/backward gains of ±20 dB. Cascading two such systems potentially can offer high isolations at high gains. © 1965-2012 IEEE  

We introduce a 'high-probability' framework for repeated games with incomplete information. In our non-equilibrium setting, players aim to guarantee a certain payoff with high probability, rather than in expected value. We provide a high-probability counterpart of the classical result of Mertens and Zamir for the zero-sum repeated games. Any payoff that can be guaranteed with high probability can be guaranteed in expectation, but the reverse is not true. Hence, unlike the average payoff case where the payoff guaranteed by each player is the negative of the payoff by the other player, the two guaranteed payoffs would differ in the high-probability framework. One motivation for this framework... 

The impact of an interline power-flow controller (IPFC) on composite system delivery point and overall system reliability indices is examined in this paper. In this application, the IPFC with dc transmission lines is employed in a system for coordinated control of line impedances of two, distance away, transmission lines with the objective of managing power flows on the two lines. It is also used to balance the real power being transferred between the compensated lines. For this purpose, the reliability model associated with a converter station has been developed and incorporated in an IPFC reliability model. A number of reliability indices are calculated at both the loadpoint and system... 

An adaptive fuzzy sliding mode control scheme is presented in this article. Despite the advantages of sliding mode control design for uncertain dynamic systems, classical sliding mode control has a major problem in the form of chattering, produced by the rapid switching used to conduct the state trajectories toward the sliding surfaces. A variety of methods are used to achieve chattering-free motion by smoothing out the switching functions; a fuzzy method is introduced in this article. In the proposed approach, the switching functions are replaced by adaptive fuzzy control signals such that the Lyapunov stability conditions are satisfied. This adaptive fuzzy controller can improve the... 

The concept of a nonlinear transfer function of a fibre-optic communication link is reviewed. Also an approximation of the nonlinear transfer function is introduced, which allows to define an equivalent single-span model of a dispersion-managed multi-span system. In this paper we will show its limits of validity and try to extent these limits by enhancing the theoretical model. In this respect we will discuss the impact of dispersion precompensation and show the influence of residual dispersion per span, number of spans and local dispersion on transmission systems with on-off keying and differential phase-shift keying modulation formats. This approach allows fast assessment of the... 

In this paper, a Static Synchronous Series Compensator (SSSC) is used to avoid torsional mode instability in a series compensated transmission system. The power system used in this study is the IEEE first benchmark model for Sub-Synchronous Resonance (SSR) analysis. Simulation results in time domain using PSCAD/EMTDC presented and discussed. ©2006 IEEE  

The response of large-scale building structures can be actively reduced using an appropriate control algorithm and a number of actuators and sensors located within the building. This paper presents a decentralized control approach for controlling the response of tall buildings. The proposed method aims to divide the structural model into several substructures, each one performing on its own controller algorithm. This approach has already been used in controlling large-scale systems such as power transmission systems and space structures. An instantaneous optimal control scheme is used as the control algorithm with different control feedbacks such as velocity feedback alone and displacement...