Sharif Digital Repository

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... 

While the importance of wide area measurement system (WAMS) consisting of phasor measurement units (PMUs) is recognized, there are still unidentified applications that can be addressed with the advance of technology. Traditionally, power system operators diagnosed the fault point through the status of protective relays and circuit breakers of the protection system. In large blackouts, however, the malfunction of protection system has itself often been among the suspects of the disaster. This paper proposes an alternative fault diagnosis approach independent of the function of protection system, utilizing PMU data and bus impedance matrix (Zbus). First, the proposed method diagnoses the fault... 

This paper introduces a novel approach for power system fault diagnosis based on synchronized phasor measurements during the fault. The synchronized measurements are obtained in real time from Phasor Measurement Units (PMUs) and compared with offline thresholds determined by decision trees (DTs) to diagnose the fault. The DTs have already been trained offline using detailed power system analysis for different fault cases. While the traditional methods for fault diagnosis use the status of protective relays (PRs) and circuit breakers (CBs) to infer the fault section in the power system, the proposed method uses the available signals following the fault and thus can be trusted even in case of... 

This paper presents a novel heuristic algorithm for solving economic dispatch (ED) problems, by employing iteration particle swarm optimization with time varying acceleration coefficients (IPSO-TVAC) method. Due to the effect of valve-points and prohibited operation zones (POZs) in the generating units' cost functions, ED problem is a non-linear and non-convex optimization problem. The problem even may be more complicated if transmission losses are taken into account. The effectiveness of the proposed method is examined and validated by carrying out extensive tests on three different test systems. Valve-point effects, POZs, ramp-rate constraints and transmission losses are modeled. Numerical... 

The objective of the dynamic economic dispatch (DED) problem is to schedule power generation for the online units for a given time horizon economically, satisfying various operational constraints. Due to the effect of valve-point effects and prohibited operating zones (POZs) in the generating units cost functions, DED problem is a highly non-linear and non-convex optimization problem. The DED problem even may be more complicated if transmission losses and ramp-rate constraints are taken into account. This paper presents a novel and heuristic algorithm to solve DED problem of generating units, by employing time varying acceleration coefficients iteration particle swarm optimization... 

Mass-transfer rates to and from drops in liquid-liquid extraction processes are often reduced by the presence of contaminants. To design an industrial extractor, it is essential to consider this contamination effect in a quantitative manner. To achieve this goal, an experimental investigation was conducted on the mass transfer into single drops for n-butanol-succinic acid-water, as the recommended test system by the European Federation of Chemical Engineering (EFCE). The effects of anionic (sodium dodecyl sulfate, SDS), cationic (dodecyl trimethyl ammonium chloride, DTMAC), and nonionic (octylphenol decaethylene glycol ether, Triton X-100) surfactants on the hydrodynamic and mass-transfer... 

Distribution systems management is becoming an increasingly complicated issue due to the introduction of new technologies, new energy trading strategies and new deregulated environment. In the new deregulated energy market and considering the incentives coming from the technical and economical fields, it is reasonable to consider distributed generation (DG) as a viable option to solve the lacking electric power supply problem. This paper presents a mathematical distribution system planning model considering three planning options to system expansion and to meet the load growth requirements with a reasonable price as well as the system power quality problems. DG is introduced as an attractive... 

Transmission line congestion in electricity market is lead to increase the energy cost and change in local marginal prices. So, it is probable that the market power is manifested. Market power may prevent the full competition in Electricity Market. Moreover, in this condition, with operating of power system in its boundary conditions, the system may be damaged and the security of the system may be disturbed. On the other hand, decreasing the line flows from their optimal value, cost and consequently, price of energy are increased. So, there is need to have a compromise between the line flow decrease and the cost those impose. In this paper, a framework for compromising between social cost... 

Distribution systems management is becoming an increasingly complicated issue due to the introduction of new technologies, new energy trading strategies and new deregulated environment. In the new deregulated energy market and considering the incentives coming from the technical and economical fields, it is reasonable to consider Distributed Generation (DG) as a viable option to solve the lacking electric power supply problem. This paper presents a mathematical distribution system planning model considering three planning options to system expansion and to meet the load growth requirements with a reasonable price as well as the system power quality problems. DG is introduced as an attractive... 

This paper discusses various aspects of unified power flow controller (UPFC) control modes and settings and evaluates their impacts on the power system reliability. UPFC is the most versatile flexible ac transmission system device ever applied to improve the power system operation and delivery. It can control various power system parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the power system reliability has not been addressed sufficiently yet. A power injection model is used to represent UPFC and a comprehensive method is proposed to select the optimal UPFC control mode and settings. The proposed method applies the results of a contingency... 

Considerable developments in the real-time telemetry of demand-side systems allow independent system operators (ISOs) to use reserves provided by demand response (DR) in ancillary service markets. Currently, many ISOs have designed programs to utilize the reserve provided by DR in electricity markets. This paper presents a stochastic model to schedule reserves provided by DR in the wholesale electricity markets. Demand-side reserve is supplied by demand response providers (DRPs), which have the responsibility of aggregating and managing customer responses. A mixed-integer representation of reserve provided by DRPs and its associated cost function are used in the proposed stochastic model.... 

Reliability of energy supply is one of the most important issues of service quality. On one hand, customers usually have different expectations for service reliability and price. On the other hand, providing different level of reliability at load points is a challenge for system operators. In order to take reasonable decisions and obviate reliability implementation difficulties, market players need to know impacts of their assets on system and load-point reliabilities. One tool to specify reliability impacts of assets is the criticality or reliability importance measure by which system components can be ranked based on their effect on reliability. Conventional methods for determination of... 

Voltage stability is the ability of a power system to maintain acceptable voltages at all buses in the system under normal conditions and after being subjected to a disturbance. This paper employs the management of reactive power generation to improve the voltage stability margin (VSM), in the framework of optimal reactive power dispatch (ORD) problem. Scheduling of VAR sources is performed using the concept of relative value of VAR sources. The proposed methodology has been tested on the IEEE 14-bus test system. Simulation results show that after the optimal reactive power scheduling, VSM of the systems is increased considerably. In addition, it is observed that reactive power reserve is... 

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... 

Load flow problems have always been an important issue in power system analysis and require proper modeling of system components. In this regard Flexible AC Transmission System (FACTS) controllers are modern devices that their modeling specially the series type is a challenging topic. This paper describes a three-phase model for Distributed Static Series Compensator (DSSC) based on extending the Static Synchronous Series Compensator (SSSC) model in Newton power flow. To extend the SSSC model the following two differences must be considered; three completely independent phases and the existence of several modules in a DSSC system. Simulation results on the IEEE 30-bus system and a five bus... 

With the introduction of restructuring concepts to traditional power systems, a great deal of attention is given to the utilization of distributed generation. Since the integration of DG units has been known as an alternative for main grid as a resource for energy supply, the determination of optimal sizing and sitting is an important issue in the planning procedure of DG. This work presents a comprehensive multi-objective model for integration of distributed generations into a distribution network, regarding various technical, economical and environmental issues such as reduction of carbon dioxide emissions and investment & running costs while the bus voltages shall be kept within... 

In this paper we investigate the effects of superconducting shielded core reactor (SSCR) on the operation of induction generators. Large number of induction generators used in wind power plants generally increase the short circuit current level of the system. The reason is that they provide parallel reduced-impedance paths for the fault currents. Taking advantage of SSCR in wind power plants allows for using these generating units in large numbers with no concerns about the system fault current increments. The study is performed on a test system using the conventional model of an induction generator and a new effective model for SSCR based on its shielding behavior. Mathematical equations... 

A reasonable amount of spinning reserve is essential to satisfy system security constraints when the power system encounters a contingency. Most ofthe methods previously developed for spinning reserve assessment ignore the probabilistic aspects of system components. This paper presents the design of a market for energy and spinning reserve services. This dispatching method has been developed to minimize the cost associated with theses services while maintaining the system security. Particle swarm optimization (PSO) is used for determining the global optimal solution for this dispatch problem. The effectiveness of the proposed approach is examined by application to the IEEE Reliability Test... 

This paper presents an optimal phasor measurement units (PMUs) placement algorithm for the purpose of power system observability and also increasing the performance of secondary voltage control scheme. The optimal placement problem (OPP) is formulated such that to minimize the number of PMU installations subject to full network observability and monitoring pilot buses of the system to improve secondary voltage control performance. The branch and bound optimization method is adopted to solve the OPP problem which is suitable for problems with integer and boolean variables. Topology-based algorithm is used for observability analysis. Constraint functions considering adjacent zero-injection... 

Distribution systems management is becoming an increasingly complicated issue due to the introduction of new technologies, new energy trading strategies, and new deregulated environment. In the new deregulated energy market and considering the incentives coming from the technical and economical fields, it is reasonable to consider Distributed Generation (DG) as a viable option to solve the lacking electric power supply problem. This paper presents a mathematical distribution system planning model considering three planning options to system expansion and to meet the load growth requirements with a reasonable price as well as the system power quality problems. DG is introduced as an...