Sharif Digital Repository

This paper presents a priority based dynamic programming approach for long term maintenance scheduling of overhead distribution networks. The proposed approach is based on risk management approach and utilizes the model of decoupled risk factors. Two heuristic factors are defined and utilized in order to establish a maintenance priority list and to curtail the dynamic programming search space. The proposed methodology yields a significant computational saving compare to the previously reported dynamic programming. Risk management approach enables the asset managers to consider the actual condition of electrical equipments and expected consequence of their failures. Furthermore, the decoupled... 

This paper proposes a stochastic mixed-integer programming (SMIP) model for the reliability-constrained unit commitment (RCUC) problem. The major objective of the paper is to examine both features of accuracy and efficiency of the proposed SMIP model of RCUC. The spinning reserve of generating units is considered as the only available reserve provision resource; however, the proposed formulation can be readily extended to comprise the other kind of reserve facilities. Expected load not served (ELNS) and loss of load probability (LOLP) are accommodated as the reliability constraints. Binding either or both reliability indices ensures the security of operation incorporating the stochastic... 

This paper proposes a stochastic mixed-integer programming (SMIP) model for the reliability-constrained unit commitment (RCUC) problem. The major objective of the paper is to examine both features of accuracy and efficiency of the proposed SMIP model of RCUC. The spinning reserve of generating units is considered as the only available reserve provision resource; however, the proposed formulation can be readily extended to comprise the other kind of reserve facilities. Expected load not served (ELNS) and loss of load probability (LOLP) are accommodated as the reliability constraints. Binding either or both reliability indices ensures the security of operation incorporating the stochastic... 

This paper addresses the midterm preventive maintenance outage scheduling problem of thermal generating units which is becoming increasingly important due to the aging of power generation fleet. In this context, a novel midterm preventive maintenance outage scheduler is proposed based on decision tree and mixed integer linear formation which explicitly considers the thermal units aging momentum in terms of failure rate. This allows the system operators to determine the thermal units' maintenance outage window based on the cost/benefit analysis of preventive maintenance tasks while optimizing the time interval between consecutive maintenance tasks. Additionally, the division of the year-long... 

This paper addresses the midterm preventive maintenance outage scheduling problem of thermal generating units which is becoming increasingly important due to the aging of power generation fleet. In this context, a novel midterm preventive maintenance outage scheduler is proposed based on decision tree and mixed integer linear formation which explicitly considers the thermal units aging momentum in terms of failure rate. This allows the system operators to determine the thermal units' maintenance outage window based on the cost/benefit analysis of preventive maintenance tasks while optimizing the time interval between consecutive maintenance tasks. Additionally, the division of the year-long... 

This paper presents an efficient mixed-integer linear formulation for long term maintenance schedule of overhead lines. The proposed formulation is based on risk management approach and utilizes the model of decoupled risk factors. The proposed methodology yields a significant computational saving comparing to the previously reported dynamic programming. Risk management approach enables the asset managers to consider the actual condition of electrical equipment and expected consequence of their failures. Furthermore, the decoupled risk strategy in conjunction with the mixed-integer linear programming formulation establishes a precise description of time-dependent deterioration failure rate... 

A two-stage framework for transformer maintenance management is introduced and formulated in Part I of this two-part paper in the context of transmission asset management strategies (TAMS). The proposed model optimizes maintenance outage schedule over a predefined period of time by taking into account the actual and expected transformer assets' condition dynamics in terms of failure rate and resource limitations in midterm horizons, as well as operating constraints, economic considerations and N-1 reliability in the shorter term. In Part II, a small six-bus system is first used to demonstrate how the two-stage maintenance framework works using a step-by-step procedure. Then, IEEE-RTS is used... 

Automation is acknowledged by distribution utilities as a successful investment strategy to enhance reliability and operation efficiency. However, practical approaches that can handle the complex decision-making process faced by decision makers to justify the long-term financial effects of distribution automation have remained scarce. An automated and remote-controlled sectionalizing switch play a fundamental role in an automated distribution network. This paper introduces a new optimization approach for distribution automation in terms of automated and remotely controlled sectionalizing switch placement. Mixed-integer linear programming (MILP) is utilized to model the problem. The proposed... 

Automation is acknowledged by distribution utilities as a successful investment strategy to enhance reliability and operation efficiency. However, practical approaches that can handle the complex decision-making process faced by decision makers to justify the long-term financial effects of distribution automation have remained scarce. An automated and remote-controlled sectionalizing switch play a fundamental role in an automated distribution network. This paper introduces a new optimization approach for distribution automation in terms of automated and remotely controlled sectionalizing switch placement. Mixed-integer linear programming (MILP) is utilized to model the problem. The proposed... 

The emergence of smart grid technologies in terms of advanced communication infrastructure, embedded intelligence, diagnostics and monitoring capabilities offers new opportunities for improved transmission asset management strategies (TAMS). Accordingly, power system operators are currently looking for analytics that can make use of transmission asset condition monitors and data already available to make better-informed decisions. This two-part paper introduces a two-stage maintenance scheduler for power transmission assets. Part I begins with the motivation for TAMS and then continues with a two-stage maintenance management model that incorporates joint midterm and short-term maintenance.... 

Redundancy technique is considered as a way to enhance the reliability and availability of a system. This paper models availability of a repairable system with multiple subsystems in which the involved components follow the load sharing strategy. In redundancy allocation problems, the redundancy level is just considered, whereas, in this paper, the number of repair facility (repairman) is added to the decision variables. The goal is to find the optimal number of repairmen and redundant components in each subsystem for optimization of availability subject to weight, cost and volume constraints. The main contribution of this study is to present a straightforward model for availability... 

A novel BiCMOS voltage-to-voltage converter with logarithmic characteristics and very high accuracy is presented. The relationship between the emitter current and the base-emitter voltage in bipolar transistors is used to realize the logarithmic function. With 1.8 supply voltage, the total power consumption is less than 15.75 mW and a Log error of < -36dB is shown in the ADS simulations. Compared to the other method in the literature, very better accuracy in logarithm calculation is achieved. The proposed method can be used in arithmetical operation circuits like analog processors  

A novel semi-active control system for suspension systems of passenger car using Magnetorheological (MR) damper is introduced. The suspension system is considered as a mass-spring model with an eight-degrees-of-freedom, a passive damper and an active damper. The semi-active vibration control is designed to reduce the amplitude of automotive vibration caused by the alteration of road profile. The control mechanism is designed based on the optimal control algorithm, Linear Quadratic Regulator (LQR). In this system, the damping coefficient of the shock absorber changes actively trough inducing magnetic field. It is observed that utilizing the present control algorithm may significantly reduce... 

We use the topological entanglement entropy (TEE) as an efficient tool to fully characterize the Abelian phase of a Z2 ×Z2 spin liquid emerging as the ground state of topological color code (TCC), which is a class of stabilizer states on the honeycomb lattice. We provide the fusion rules of the quasiparticle (QP) excitations of the model by introducing single- or two-body operators on physical spins for each fusion process which justify the corresponding fusion outcome. Besides this, we extract the TEE from Renyi entanglement entropy (EE) of the TCC, analytically and numerically by finite size exact diagonalization on the disk shape regions with contractible boundaries. We obtain that the EE... 

In discussions related to reliability optimization using redundancy allocation, one of the structures that has attracted the attention of many researchers, is series-parallel structure. In models previously presented for reliability optimization of series-parallel systems, there is a restricting assumption based on which all components of a subsystem must be homogeneous. This constraint limits system designers in selecting components and prevents achieving higher levels of reliability. In this paper, a new model is proposed for reliability optimization of series-parallel systems, which makes possible the use of non-homogeneous components in each subsystem. As a result of this flexibility,... 

A new optimal waveform for Ultra-wideband (UWB) radios is proposed in this paper. This new waveform extracted through mathematical analysis for achieving high spectral utilization under the restrictions imposed by the U.S. Federal Communications Commission (FCC) spectral masks. Exploiting Inverse Fourier Transform (IFT) of FCC mask, the required analog signals are extracted through robust calculation and the optimum realizable analog signal for FCC mask is constructed while the simulations confirmed the analytical approach. Normalized effective signal power (NESP) of the proposed method is 95.27% which shows better efficiency compared to the other methods in the literature  

An electric power supply is the backbone of development in advanced as well as in developing economies. An integral part of ensuring a secure power supply system is a power communication system. Due to the high and sustained performance requirements of power communication systems, electric companies prefer to construct their own communication networks privately rather than relying solely on a public communication system. The focus of this paper is on the optimal topological design of a power communication network. Based on advanced optimization models in public communication networks, and taking into account the specific Quality of Service, as demanded by various applications, such as... 

Interaction of the DNA thymine base with Cu+ and Zn3+ was studied to explore: a) The metal binding energy (MIA) of thymine with Cu+ and Zn2+ and b) The possible correlation between charge transfer and MIAs. The gas-phase Cu+ and Zn2+ affinities of thymine, as well as the Mulliken charges, on the complexed metal cations were both determined at the same computational level, including the density functional level and employing the hybrid B3LYP exchange correlation potential in connection with the 6-311++G (d,p) basis set. All the molecular complexes were obtained by interaction between the most stable tautomer of thymine and two transition mono and divalent (Cu+, Zn2+) metal ions. To probe all... 

A new approach is presented in this paper to determine the degree of system well-being in the form of healthy, marginal and at risk state indices using the fuzzy logic concepts. Conventional well-being method uses a crisp deterministic criterion to divide power system comfort zone into the healthy and marginal states. In this regard, the main drawback is associated with categorising the system performance in the comfort zone into the healthy and marginal states. To overcome this problem, a new approach is developed that categorises the states as healthy or marginal using fuzzy logic. The technique together with the effects on the system risk and the system health and margin probabilities of... 

A novel semi active control system for eleven Degrees of Freedom passenger car's suspension system using Magneto rheological damper is presented. The considered suspension system is modeled using mass spring damper model. The semi active vibration control is designed to reduce the amplitude of vehicle's vibration due to by road profile. The applied control strategies are based on a Linear Quadratic Gaussian optimal control algorithm to obtain desired damping forces of MR dampers. In considered system, the damping coefficient of the shock absorber changes actively through inducing magnetic field. The necessary input voltage to MR dampers to generate desired damping forces are derived using...