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This paper deals with the load behavior of pulp and paper industries after planned or forced outages. Real data of the power consumption following outages have been collected for most of the industries in Sweden. Based on these data load models have been proposed. The economical consequences of disturbances have been evaluated and a method of estimating the costs following a disturbance is presented. The possibility to disconnect parts of the load in a pulp and paper industry is discussed and can result in a reduction of the number of gas turbines necessary for the disturbance power reserve. Index Terms--Pulp and paper industry, outage, cold load pick up, load recovery.

Times are changing in the utility industry and public groups are taking a more active role in the Integrated Resource Planning Process by presenting their advice and consultation on matters of public concerns as evidenced by the following abstracts that summarize the panel session held during the 1994 Summer Power Meeting in San Francisco, California. Carol Fisher, ABB Systems Control, Automated Distribution Division, chaired the session; while Nancy Esteb of Pacificorp, Earl Greene, Jr. of Florida Power Corporation and Benjamin Hobbs of Case Western Reserve University were the panelists. Each panelist presented a different perspective on public participation in the IRP process with examples of how their companies developed and implemented this process. The following papers summarize the individual presentations and discussions.

There is an increasing interest in Demand-Side Management (DSM) by utilities and regulators throughout the country. With this interest, there is an increasing need for DSM evaluation. Regulators expect utility engineers to use least cost planning and integrated resource planning approaches to adjust their generation capacity plans to reflect DSM. Increasingly, utilities are considering DSM to affect their T&D capacity plans. One utility CEO recently commented that no major distribution enhancements will be made until all DSM options have been exhausted. However, major utility DSM programs are less than a decade old. This leaves many utility engineers uneasy. How do they know that DSM will be there when they really need it? To verify and improve the contribution of DSM programs, utility analysts have developed a set of methodologies and procedures for evaluating DSM. The purpose of this panel session was to review these state of the art evaluations and the lessons learned from them so far. We explore the differences inherent in evaluating DSM at the T&D level versus the generation level, and we review DSM's persistence and reliability in the residential, commercial, and industrial sectors.

This paper proposes to adopt the emerging Professional Science Master (PSM) program as a model for enriching power engineering education. PSM programs provide comprehensive training in an academic and technical specialty along with the appropriate professional skills needed for a professional career. The paper outlines the new PSM program—MS in Electric Power Systems Engineering. The program encompasses engineering, management, and other professional skills needed for a successful career in the power engineering industry, and includes both in-depth core power engineering topics as wells as new cross-disciplinary technical topics relevant to the clean-energy Smart Grid. [ABSTRACT FROM PUBLISHER]

In this paper we investigate whether considering the fine structure of half-hourly electricity prices, the market closing prices of fundamentals (natural gas, coal and CO2) and the system-wide demand can lead to significantly more accurate short- and mid-term forecasts of APX U.K. baseload prices. We evaluate the predictive accuracy of a number of univariate and multivariate time series models over a three-year out-of-sample forecasting period and compare it against that of a benchmark autoregressive model. We find that in the short-term, up to a few business days ahead, a disaggregated model which independently predicts the intra-day prices and then takes their average to yield baseload price forecasts is the best performer. However, in the mid-term, factor models which explore the correlation structure of intra-day prices lead to significantly (as measured by the Diebold-Mariano test) better baseload price forecasts. At the same time, we observe that the inclusion of fundamental variables—especially natural gas prices (in the short-term) and coal prices (in the mid-term)—provides significant gains. The CO2 prices, on the other hand, generally do not improve the price forecasts at all, at least in the time period considered in this study (April 2009–December 2013). [ABSTRACT FROM PUBLISHER]

This paper proposes a two-stage auction-based local market mechanism to allocate physical storage rights (PSRs). As a market product, PSRs are provided by a storage owner and enable the local market participants (including renewable producers, consumers and prosumers) to access the storage. That is, they can book storage in the form of PSRs and dispatch it at a given time aiming to maximize their utility function. The business options we examine to evaluate the position of storage in the market range from storage owner entirely participating in day-ahead (DA) and real-time (RT) markets as an inter-temporal arbitrager, to exclusively acting as a PSR provider in DA only – this way, the storage owner is fully paid upfront in DA. Considering the context above, we propose an equilibrium model where each player optimizes its operational objective. We prove that the equilibrium model can be substituted with an equivalent optimization formulation which clears the proposed market ensuring the same desirable market properties, such as efficiency and revenue adequacy. Results suggest that the certain revenues earned by the storage owner in DA when acting as a PSR provider is equal to its expected profit as a regular market participant, mitigating however its payoff uncertainty and resulting in the same economic return. [ABSTRACT FROM AUTHOR]

Common information model (CIM) in vogue represents transmission and distribution components, and market operations in the perspective of electrical system, as unified modeling language (UML) objects. UML is object centric. CIM can offer interoperability and facilitate model exchange for large systems and is being adopted by many utilities. However, dealing effectively with multiple business processes is the backbone of the restructured power systems. Since CIM lacks chronological process sense, this has to be superimposed on CIM models, which is not easy due to inherent limitations of UML. To overcome this, this paper proposes to utilize business process modeling notation (BPMN) standards as a kind of pre-processor. BPMN is used to represent process centric interoperability requirements as business objects. UML object representation in CIM model is derived subsequently from it. The proposal is illustrated with an application use case—deriving CIM model of day-ahead market (DAM) transaction of distribution company, from its business process representation. Semantic model of DAM transaction using CIM IEC 62325 (Markets) and extensions required are presented with a sample Indian system. DAM models in BPMN and CIM can be utilized to build an efficient software application. [ABSTRACT FROM PUBLISHER]

The development of the smart grid calls for enhanced power system application interoperability and knowledge management. The IEC Common Information Model (CIM) supports semantic interoperability but multiple identities attributed to common power system resources present challenges to unambiguous metadata model merging within a repository. This paper describes an original methodology for the building of a novel metadata model repository that concentrates our knowledge of enterprise power system resources. We leverage the value of model namespaces and resource description framework (RDF) technology in providing contexts for multiple identities referring to common power system resources. This novel approach aims to develop a more realistic understanding of network reality than repositories depending on a single CIM XML namespace and contributes to engineering an “enterprise ontology” supporting interoperability and business intelligence. We demonstrate this novel approach with reference to National Grid use cases for network operation and planning model management roles. [ABSTRACT FROM PUBLISHER]

For a successful rollout of electric vehicles (EVs), it is required to establish an adequate charging infrastructure. The adequate access to such infrastructure would help to mitigate concerns associated with limited EV range and long charging times. Battery swapping stations are poised as effective means of eliminating the long waiting times associated with charging the EV batteries. These stations are mediators between the power system and their customers. In order to successfully deploy this type of stations, a business and operating model is required, that will allow it to generate profits while offering a fast and reliable alternative to charging batteries. This paper proposes an optimization framework for the operating model of battery swapping stations. The proposed model considers the day-ahead scheduling process. Battery demand uncertainty is modeled using inventory robust optimization, while multi-band robust optimization is employed to model electricity price uncertainty. The results show the viability of the proposed model as a business case, as well as the effectiveness of the model to provide the required service. [ABSTRACT FROM PUBLISHER]

Information visualization appears to be a promising technique for improving the business practices in today's electric power industry. The legacy power system visualization tools, however, restrict the visualization process to follow a limited number of pre-defined patterns created by human designers, thus hindering users' ability to discover. This paper proposes a data-driven approach to interactive visualization of power systems. The proposed approach relies on developing powerful data manipulation algorithms to create visualizations based on the characteristics of empirically or mathematically derived data. Based on this approach, a data-driven model exploratory tool has been developed to enable users to visualize the power system's physical/electrical configurations at various levels and from different perspectives. The conducted case studies have demonstrated that the data-driven approach could result in an interactive and user-driven power system visualization tool that fosters scientific understanding and insight, therefore unleashing the power of visualization. [ABSTRACT FROM PUBLISHER]

Boosted by U.K. governmental targets of securing 10% of electricity generation from renewable resources by 2010 and 20% by 2020 and widespread public support for renewable energy, distributed generators (DGs) are rapidly increasing in electrical power systems. Among the renewable DGs, wind energy is emerging as the popular choice due to its mature technology and low operation and maintenance costs. This paper utilizes the reliability aspects of electrical power systems to provide a probabilistic approach to determine the capacity credit (CC) of distributed generators. Monte Carlo simulations are employed to cater for the stochastic nature of the simulations and each trial is validated using the Newton-Raphson optimal load flow solution. Bernoulli trials are used to simulate the availability of network components. An algorithm to evaluate the capacity credit due to distributed generation (DG) connected in the network is shown. Hence, the amount of conventional generation which can be backed off from the bulk supply point (BSP) of the distribution network can be quantified. Wind energy production is known to depend on the wind regime experienced by the wind turbines, as well as the geographical landscape and the presence of wind obstacles, which in turn determines capacity credit. Having verified that adding a specific DG at each node does not violate any operating constraints, it was assumed that thermal constraints would not affect CC in this particular system. In a more in-depth study, it is shown in this paper that capacity credit also varies with the different voltage levels at which the wind turbine generators are connected and the loading level of the distribution network. Moreover, it is shown that CC does not vary with the base case reliability, but rather with wind penetration levels. Index Terms--Capacity credit, distribution systems, Monte Carlo simulation, power system planning, wind energy.

Large scale distribution system planning is a relatively complex and reasonably difficult problem. This paper proposes the application of improved genetic algorithm (GA) for the optimal design of large scale distribution systems in order to provide optimal sizing and locating of the high and medium voltage (HV and MV) substations, as well as medium voltage (MV) feeders routing, using their corresponding fixed and variable costs associated with operational and optimization constraints. The novel approach presented in the paper solves hard satisfactory optimization problems with different constraints in large scale distribution networks. This paper presents a new concept based on loss characteristic matrix introduced for optimal locating of MV substations, followed by new methodology based on graph theory and GA for optimal locating of the HV substations and MV feeders routing in a real size distribution network. Minimum spanning tree algorithm is employed to generate set of feasible initial population. In the present article to reduce computational burden and avoid huge search space leading to infeasible solutions, special coding methods are generated for GA operators to solve optimal feeders routing. The proposed coding methods guarantee the validity of the solution during the progress of the genetic algorithm toward the global optimal solution. The developed GA-based software is tested in a real size large scale distribution system and the well satisfactory results are presented. Index Terms--Distribution system planning (DSP), genetic algorithm (GA), graph theory, long-term load forecasting.

Phasor measurement units (PMUs) are considered as a promising tool for future monitoring, protection and control of power systems. In this paper, a unified approach is proposed in order to determine the optimal number and locations of PMUs to make the system measurement model observable and thereby can be used for power system state estimation. The PMU placement problem is formulated as a binary integer linear programming (BILP), in which the binary decision variables (0, 1) determine whether to install a PMU at each bus, while preserving the system observability and lowest system metering economy. The proposed approach integrates the impacts of both existing conventional power injection/flow measurements (if any) and the possibility of single or multiple PMU loss into the decision strategy of the optimal PMU allocation. Unlike other available techniques, the network topology remains unaltered for the inclusion of conventional measurements, and therefore the network connectivity matrix is built only once based on the original network topology. The mathematical formulation of the problem maintains the original bus ordering of the system under study, and therefore the solution directly points at the optimal PMU locations. Simulations using Matlab are conducted on a simple testing seven-bus system, as well as on different IEEE systems (14-bus, 30-bus, 57-bus, and 118-bus) to prove the validity of the proposed method. The results obtained in this paper are compared with those published before in literature. Index Terms--Integer programming, optimal location, PMUs, state estimation.

This paper is the first of two and presents a planning methodology for low-voltage distribution networks. Combined optimization of transformers and associated networks is performed, considering the street layout which connects the different consumers. In this first part, micro-optimization, the planning zone is divided into small zones, mini-zones, which are optimized independently. A repetitive procedure is used in order to locate transformers using clustering techniques. Optimum capacity, customers to be satisfied, the optimum network to be used and losses associated to this network are determined for each location. The methodology is applied over an area of 12.9 [km.sup.2] with nearly 20 215 consumers. In the second paper, two macro-optimization methodologies are discussed based on the planning results for each mini-zone, one based on the Voronoi polygons in order to improve load grouping into mini-zones and the other based on the combination of neighboring networks into a single transformer by means of a Tabu search. Finally, the methodology is applied to a zone with a surface of 2118 [km.sup.2] and approximately 1 300 000 customers. Index Terms--Cluster, low voltage, network planning, power distribution planning.

The positive feedback-based anti-islanding scheme has become a common anti-islanding protection technique for inverter-based distributed generators (DGs). This paper investigates the scheme's impact on the small-signal stability of multiple inverter-based DGs installed in power distribution systems during grid-connected operation. The interactions among multiple-DGs due to the anti-islanding scheme are also addressed. An index is proposed to quantify the destabilizing effect of the aggregated positive feedback activities of multiple DGs. This paper further introduces a DG power transfer limit versus islanding detection time curve to reveal the conflicting requirements of anti-islanding protection speed and the maximum power transfer of multi-DG systems. Index Terms--Distributed generator, inverter, islanding, positive feedback, small-signal model.

Due to the recent price spike of the international oil and the concern of global warming, the development and deployment of renewable energy become one of the most important energy policies around the globe. Currently, there are different capacities and hub heights for commercial wind turbine generators (WTGs). To fully capture wind energy, different wind farms (WFs) should select adequate capacity of WTGs to effectively harvest wind energy and maximize their economic benefit. To establish selection criterion, this paper first derives the equations for capacity factor (CF) and pairing performance (PP) of WTGs using Weibull and Rayleigh distribution functions. Five commercial WFs in Taiwan are used as sample systems for comparative analyses. This paper combines Weibull function, cubic mean wind speed, and four existing economic-analysis methods to study different values of capacity and hub height for WTGs that have been installed in Taiwan. Important outcomes affecting wind cost of energy in comparison with economic results using the proposed economic-analysis methods for different WFs are also presented. Index Terms--Capacity factor (CF), economic benefit, pairing performance (PP), Rayleigh distribution, Weibull distribution, wind farms (WFs), wind turbine generators (WTGs).

In order to guard forward contracts from the locational marginal price (LMP) volatility, financial transmission rights (FTRs) are issued in the centralized power markets. However, the current FTR system can provide hedge only against the congestion components of LMP differentials. Consequently, the loss components remain unhedged. To bridge the gap, a framework is developed in this paper to implement an FTR system that will provide hedge against the loss prices. The availability of loss-hedging FTRs in addition to the congestion hedging FTRs further reduces the exposure of the forward market participants to the LMP volatility. The loss-hedging framework developed is carefully designed to fit the practical environment. All the primary issues for the implementation of loss-hedging FTRs, such as the revenue adequacy test, auction, and auction revenue rights, are carefully addressed. Revenue adequacy of loss-hedging FTRs can be ensured by means of a test called as the offset capacity test. Some efficient policies are also designed for the successful functioning of loss-hedging FTRs. At the end of the paper, a case study is carried out to assess the effectiveness of the methodology developed. Index Terms--Auction, auction revenue right, congestion hedging, financial transmission rights, locational marginal price, loss hedging, revenue adequacy.

This paper proposes the planning method for capacitor installation in a distribution system to reduce the installation costs and minimize the loss of electrical energy. The expected lifetime of devices with moving parts depends on the total number of operations, which affects the replacement period and replacement decisions for aging equipment under a limited budget. In this paper, the expected device lifetimes are included in the formulation, and the optimal operation status of the devices is determined using a genetic algorithm. The optimal numbers and locations for capacitor installation are determined based on the optimal operation status. Simulation results in a 69-bus distribution system show that the proposed technique performs better than conventional methods. Index Terms--Distribution system, genetic algorithm, operation cost, planning, shunt capacitor, under-load tap changer.

This paper demonstrates how a probabilistic criterion could be explicitly integrated in the unit commitment (UC) formulation. Both spinning reserve and interruptible load are taken into account as the operating reserve facilities. Incorporating the interruption notice time of interruptible load involves some complexities in the evaluation procedure and problem formulation which is considered in this paper. The expected energy not supplied (EENS) is considered as a probabilistic criterion and a new method is proposed to calculate this index in the presence of interruptible load. The reliability-constrained unit commitment (RCUC) problem is formulated based on the mixed-integer programming (MIP) method that can be solved using large-scale commercial solvers. The effectiveness of the proposed formulation is examined using the IEEE-RTS. Numerical results are presented and the implementation issues are discussed. A number of analyses are examined to evaluate the impact of some important factors on the problem solution. Index Terms--Interruptible load, mixed-integer programming (MIP), reliability-constrained unit commitment (RCUC), spinning reserve.

This paper describes and analyzes the Spanish AGC system. The differences with respect to a standard hierarchical structure are explained. A simple model useful for simulation is proposed. Using this model, the performance of the system and the influence of several parameters in system response is evaluated. The paper also suggests some changes in the configuration and parameter settings of the system to improve its performance. Index Terms--Automatic generation control (AGC), frequency domain analysis, transfer function identification.

This paper describes a method of developing wide-band multi-port system equivalents for use with real-time digital power system simulators. The proposed equivalent combines a frequency dependent network equivalent (FDNE) for the high frequency electromagnetic transients and a transient stability analysis (TSA) type simulation block for the electromechanical transients. The frequency dependent characteristic for FDNE is obtained by curve-fitting frequency domain admittance characteristics using the vector fitting method. The paper also introduces an approach for approximating the frequency dependent characteristic of large power networks from readily available typical power-flow data. The paper shows how the TSA algorithm can be adapted to a real-time platform. The validity of this method is confirmed with examples, including the study of a multi in-feed HVDC system based network. Index Terms--Dynamic equivalent, electromagnetic transient, frequency dependent network equivalent, power system simulation, real-time digital simulator, transient stability.

Traditional online security assessment determines whether the system is secure or not, but how secure or insecure is not explicitly indicated. This paper develops probabilistic indices, risk, to assess real-time power system security level. Risk captures not only event likelihood, but also consequence. System security level associated with low voltage and overload can be optimally controlled, using the NSGA multiobjective optimization method. A security diagram is used to visualize operating conditions in a way that enables both risk-based and traditional deterministic views. An index for cascading overloads is used to evaluate the Pareto optimal solutions. This paper shows that the multiobjective approach results in less risky and less costly operating conditions, and it provides a practical algorithm for implementation. The IEEE 24-bus RTS-1996 system is analyzed to show that risk-based system security control results in lower risk, lower cost, and less exposure to cascading outages. Index Terms--Decision making, evolutionary algorithm, nonlinear multiobjective optimization, reliability, risk, security.

This paper describes the application of the continuous Newton's method to the power flow problem. This method basically consists in formulating the power flow problem as a set of autonomous ordinary differential equations. Based on this formal analogy, we propose an entire family of numerically efficient algorithms for solving ill-conditioned or badly-initialized power flow cases. The paper also shows that the classical Newton--Raphson's method and most robust power flow techniques proposed in the literature are particular cases of the proposed formulation. An example based on a 1254-bus model of the UCTE system is presented and discussed. Index Terms--Continuous Newton's method, ill-conditioned power flow, Newton--Raphson's method, optimal multiplier, robust power flow, Runge--Kutta formulas.

This paper discusses the use of state diagrams in maintenance modeling. These diagrams frequently illustrate deterioration, inspections and maintenance. Mathematically, the state diagram can be represented by a Markov process. The paper discusses the properties of such a Markov process. They are compared with the maintenance situation in the real world. It is shown that some properties make the model inconsistent with reality especially in cases where a maintenance policy with non-periodic inspections is modeled. A numerical example is provided that shows that these model properties result in modeling errors. The presented results make it clear that the common practice of using Markov processes based on state diagrams must be judged critically when they are used for modeling certain maintenance strategies. Index Terms--Deterioration, inspection, maintenance, Markov processes, Monte Carlo methods, state diagrams.

Laboratory experiences are an important component of the education of engineering students. Rotating machinery laboratories assist with the visualization of the three-dimensional and rotating equipment. Contemporary use of rotating machines in industry often includes adjustable speed drives and digital controllers. Additionally, instrumentation is used to feedback electrical and mechanical variables to the drives and controls. Using an equipment grant from an industrial automation manufacturer, cost-effective laboratory workstations have been developed. Industrial-grade equipment is not designed for student experimentation but was adapted for this use. The workstations described in this paper incorporate modern power electronic-based drives and motors, electrical and mechanical sensors, and a computer-based control system with data acquisition. The advantages of these workstations include cost-effectiveness and the use of actual industrial devices that students might encounter in industry. Additionally, the workstations can be accessed by remote users, enabling off-campus students to also perform experiments on the workstations. The paper includes details of the workstation and its components, the data acquisition and control system, and sample experimental results. Index Terms--Ac motor drives, ac motors, dc motor drives, dc motors, electric machines, energy conversion, engineering education, laboratories, workstations.

This paper presents a new approach to security coordinated maintenance scheduling in deregulation wherein the independent system operator (ISO) does not generate a maintenance schedule by itself, but calls for maintenance scheduling plans from individual gencos. The maintenance scheduling plans, when incorporated in a medium-term security constrained production scheduling program, can result in unserved energy at one or more buses. Based on the information on bus-wise unserved energy, the ISO generates corrective signals for the genco(s), and directs them to alter their maintenance plans in specific periods and resubmit. The proposed scheme exploits the concept of commons and domains to derive a novel factor to allocate the unserved energy at a bus to a set of generators responsible. Iterations between the gencos and ISO continue until the coordination program has converged, and there is no unserved energy at any period in the system. A case-study for a large-scale power system, which is a representative reduction of the Ontario power system, is presented in the paper with insight on the coordination process. The proposed scheme is computationally simple, efficient, and can be applied to real-sized power systems. Index Terms--Maintenance scheduling, medium-term operations, production scheduling, restructured power systems.

This paper presents a stochastic midterm risk-constrained hydrothermal scheduling algorithm in a generation company (GENCO). The objective of a GENCO is to maximize payoffs and minimize financial risks when scheduling its midterm generation of thermal, cascaded hydro, and pumped-storage units. The proposed schedule will be used by the GENCO for bidding purposes to the ISO. The optimization model is based on stochastic price-based unit commitment. The proposed GENCO solution may be used to schedule midterm fuel and natural water inflow resources for a few months to a year. The proposed stochastic mixed-integer programming solution considers random market prices for energy and ancillary services, as well as the availability of natural water inflows and generators in Monte Carlo scenarios. Financial risks associated with uncertainties are considered by applying expected downside risks which are incorporated explicitly as constraints. Variable time-steps are adopted to avoid the exponential growth in solution time and memory requirements when considering midterm constraints. A single water-to-power conversion function is used instead of several curves for representing water head and discharge parameters. Piecewise linearized head-dependant water-to-power conversion functions are used for computational efficiency. Illustrative examples examine GENCOs' midterm generation schedules, risk levels, fuel and water usage, and hourly generation dispatches for bidding in energy and ancillary services markets. The paper shows that GENCOs could decrease their financial risks by adjusting expected payoffs. Index Terms--Financial and physical risks, generating companies, midterm operation, mixed integer programming, Monte Carlo simulation, stochastic price-based unit commitment, variable time step.

In this paper, an inaccuracy of the method for induction motor parameter determination used in EMTP type simulation programs (ATP, EMTP96, EMTDC) is discussed. The paper presents a numerical method for the estimation of induction motor double-cage model parameters from standard manufacturer data, i.e., full load mechanical power (rated power), full load power factor, maximum torque, starting torque, starting current and full load efficiency. The nonlinear equations to obtain the motor parameters have been solved with a modified Newton method that always converges if the problem is well defined (that is, a solution exists). The method has been tested with 608 motors from different manufacturers. The manufacturer parameters that have a greater influence on convergence are the maximum torque and the starting current. The cases where the method does not converge have been studied and the range of variation of the maximum torque or starting current which determines where the data are well defined (that is, a solution exists) has been calculated. Index Terms--Double-cage model, induction motor, manufacturer data, parameters estimation.

Financial transmission rights (FTRs) are complementary to the locational marginal pricing of energy. The basic aim of the FTR mechanism is to guard forward contracts from uncertain congestion charges. FTRs are also useful to individual generators and loads for selling and buying power, respectively, at the prices of other locations. The concept has evolved, encompassing many features such as a simultaneous feasibility test, various ways to conduct auctions and allocations and secondary trading. FTRs also have a close relation to market power and transmission investment. This paper reviews most of the landmark research papers on the evolution of the FTR concept. It reports a comprehensive assessment of various facets of FTRs and allied issues. Financial transmission rights and flowgate rights (FGRs) are compared. The concept of long-term FTRs is discussed. The paper also touches upon future proposals in this area. Index Terms--Allocation, auction, auction revenue right, financial transmission right, flowgate right, market power, obligation, option, revenue adequacy, secondary trading, transmission investment.

In order to be able to successfully apply interline power flow controllers (IPFCs) for power-system transient-stability improvement and for the damping of oscillations, proper control strategies should be applied to these devices. The basis for the implementation of such a strategy that is proposed in this paper is to know the energy function of a power system that includes IPFCs. Already-known energy functions that proved to be suitable for an electric-power system do not include such a device. Therefore, in this paper an energy function that considers the IPFC's action in the form of a supplement to the already-known structure-preserving energy functions was constructed. Furthermore, the strategy for implementing the newly developed IPFC energy functions in order to ensure a globally optimum control strategy in the Lyapunov sense is presented. The results of the numerical examples show that the magnitudes of the IPFC's series-injected voltages remain set to their maximum values and that only the angles of these voltages change, similar to the 'bang-bang' control strategies proposed for some other FACTS devices. Index Terms--FACTS devices, interline power flow controller (IPFC), Lyapunov energy function, power system control, power system dynamic stability.

In electricity markets, a pool trading model with a power exchange pool is a typical market organization that attracts much more attention than a bilateral trading model. To date, quite a few papers have focused on bilateral trading models, particularly those under network constraints. This trend is due to the model's complexity in terms of the various trading patterns, reflecting the self-interested behavior of the market participants striving to find potentially profitable transactions. In this paper, we propose a new approach based on complex networks suitable for assessing different aspects of bilateral market. This work strives to analyze the bilateral trading patterns in the electricity markets where physical network constraints need to be considered for the feasible and secure operation of the power systems. The goal of the work is to find the stable network structures that can be used to anticipate possible bilateral transactions in the real market place and to provide a novel and applicable approach to studying the bilateral model in electricity markets. The proposed approach has been tested on several test systems in which the transmission network structure of the market that accommodates the transactions is considered. The proposed model is illustrated with examples using a four-bus test system, the IEEE 30-bus, and the IEEE 118-bus test systems. Index Terms--Bilateral model, complex network, electricity markets, network constraints.

This paper presents an evolutionary algorithm based on quantum computation for bid-based optimal real and reactive power (P-Q) dispatch. The proposed quantum-inspired evolutionary algorithm (QEA) has applications in various combinatorial optimization problems in power systems and elsewhere. In this paper, the QEA determines the settings of control variables, such as generator outputs, generator voltages, transformer taps and shunt VAR compensation devices for optimal P-Q dispatch considering the bid-offered cost. The algorithm is tested on the IEEE 30-bus system, and the results obtained by the QEA are compared with those obtained by other modern heuristic techniques: ant colony system (ACS), enhanced GA and simulated annealing (SA) as well as the original QEA. Furthermore, in order to demonstrate the applicability of the proposed QEA, it is also implemented in a different problem, which is to minimize the real power losses in the IEEE 118-bus transmission system. The comparisons demonstrate an improved performance of the proposed QEA. Index Terms--Bid-based dispatch, economic dispatch, evolutionary computation, quantum computation, real and reactive power operational planning.

A novel strategy for optimal scheduling of short-term electric power generation of cascaded hydroelectric plants based on particle swarm optimization (PSO) and chance-constrained programming is presented to maximize the expected profit at a given risk level in this paper. Based on chance-constrained programming, in which some specified probability are given to simulate some uncertainties, such as water inflows, electricity prices, unit status, and so on. This paper proposes a model for short-term scheduling optimization of cascaded hydro plants, which includes uncertainties, spatial-temporal constraints among cascaded reservoirs, etc. A hybrid particle swarm optimization (HPSO), which is embedded with evolutionary algorithms, is presented to use for the solution of global optimization problems. Catastrophe theory, which is concerned with natural evolutionary or survival-of-the-fittest, is utilized as an indication of the premature converge of PSO, and the positions of particles are further adjusted in the search space according to chaos optimization. In this way, each particle competes and cooperates with its neighbors. The proof shows that HPSO is guaranteed to converge to the global optimization solution with probability one. The model presented is solved by a combination method of HPSO and Monte Carlo simulation. Finally, a numerical example is served for demonstrating the feasibility of the method developed. Index Terms--Cascaded hydroelectric plants, chance-constrained programming, optimal scheduling, particle swarm optimization, short-term electric power generation.

Power system congestion is a major problem that the system operator (SO) would face in the post-deregulated era. Therefore, investigation of techniques for congestion-free wheeling of power is of paramount interest. One of the most practiced and an obvious technique of congestion management is rescheduling the power outputs of generators in the system. However, all generators in the system need not take part in congestion management. Development of sound formulation and appropriate solution technique for this problem is aimed in this paper. Contributions made in the present paper are twofold. Firstly a technique for optimum selection of participating generators has been introduced using generator sensitivities to the power flow on congested lines. Secondly this paper proposes an algorithm based on particle swarm optimization (PSO) which minimizes the deviations of rescheduled values of generator power outputs from scheduled levels. The PSO algorithm, reported in this paper, handles the binding constraints by a technique different from the traditional penalty function method. The effectiveness of the proposed methodology has been analyzed on IEEE 30-bus and 118-bus systems and the 39-bus New England system. Index Terms--Constraints, generator sensitivities, gradient methods, optimal rescheduling, optimization techniques, particle swarm optimization, transmission congestion management.

This paper studies the minimum load cutting problem existing in the process of transmission network expansion planning when load is uncertain and expressed in interval number. The interval most minimum load cutting model is established and can be solved to get the maximum value of the minimum load cutting number when load is interval uncertain. The solution can be used to evaluate the safety of the planning schemes under interval uncertainty and guide the new plans' making under interval load. The load values in the optimal solution of this problem have been proved to be at their lower or upper limits. Two different algorithms are proposed to solve this model. One is better in being capable of getting global optimal solution, while the other is better in calculation speed. Both of them are compared with two traditional methods that are generally used to evaluate the system's safety under uncertainty in aspects of precision and speed. This evaluation method is applied to the greedy randomized adaptive search procedure algorithm to solve the transmission expansion planning problem under interval load. The case results show the rightness and validity of the model and algorithms proposed in this paper. Index Terms--Branch-and-bound algorithm, interval load, minimum load cutting problem, transmission network expansion planning, uncertainty in demand.

In this paper, we continue to analyze optimal dispatch of generation and transmission topology to meet load as a mixed integer program (MIP) with binary variables representing the state of the transmission element (line or transformer). Previous research showed a 25% savings by dispatching the IEEE 118-bus test case. This paper is an extension of that work. It presents how changing the topology affects nodal prices, load payment, generation revenues, cost, and rents, congestion rents, and flowgate prices. Results indicate that changing the topology to cut costs typically results in lower load payments and higher generation rents for this network. Computational issues are also discussed. Index Terms--Mixed integer programming, power generation dispatch, power system economics, power transmission control, power transmission economics.

This paper presents a new approach to design reactive power capacity markets. Under this approach annual auctions to procure reactive power capacity are conducted by the system operator. Two products are defined, reactive power generation and absorption capacity, which can be supplied by different independent VAR sources, such as generators, SVCs, capacitor banks and shunt reactors. Reactive power capacity is allocated using an optimization algorithm that matches capacity bids and system reactive power needs, for peak and low demand hours. The reactive power requirements are calculated taking into account system contingencies and the dynamic performance of the VAR sources under these situations. Another key proposal of the paper is the distribution of costs of the reactive power capacity market to the agents responsible for contingencies according to the use of the service by each market participant. This remuneration approach provides fair and efficient economic signals to all market participants. The applicability of the approach is illustrated with two case studies. Index Terms--Ancillary services, Aumann-Shapley value, capacity markets, reactive power pricing, voltage control.

This paper proposes a new voltage instability risk indicator based on local phasor measurements at fast sampling rate. The effectiveness of the indicator is analyzed at EHV load and 'transit' buses. The risk criterion is based on the real-time computation of the Thevenin equivalent impedance of the classic electrical circuit given by an equivalent generator connected to an equivalent load impedance through an equivalent connecting impedance. The main contribution of the paper is the innovating algorithm utilized on the real-time adaptive identification of the Thevenin voltage and impedance equivalents. The algorithm performance is shown through a detailed sensitivity analysis. The paper presents important numerical results from the actual Italian EHV network. Index Terms--Dynamic simulation, long-term voltage stability, online VSA, phasor measurement unit (PMU), Thevenin equivalent, voltage stability.

This paper presents a model for evaluating small hydro power plants (SHPP) generation availability that can be applied to generation systems reliability and to generation planning studies. The model considers the uncertainties of rivers inflows and generation units operation. The river inflow is modeled as a stationary stochastic process by a multiple states Markov chain and the generator unit by a two states Markov model. The large number of different inflow values is reduced by the application of the statistical clustering techniques K-means in two different approaches: inflow clustering and power clustering. The steady state probabilities of each power generation value of the SHPP are calculated by the solution of the stochastic system. The expected value of the annual power generation of the SHPP, the duration curve, and several reliability indices are then calculated in a more accurate way than conventional approaches, since the model considers both the river inflow variation and the generation unit operation. Results obtained with actual Brazilian rivers inflows used for SHPP generation are reported in the paper and demonstrate the accuracy and applicability of the presented method for reliability evaluation. Index Terms--Energy availability, generation systems, inflow time series, reliability evaluation, small hydro power plants, statistical clustering technique.

The locational marginal pricing (LMP)-based settlement results in a surplus collected by the system operator from the consumers. The nonlinear transmission losses and the constrained operation of the power system due to operating limits, such as power flow limits on transmission lines, cause the accumulation of this surplus. This accumulated revenue, referred to as the network rental in this paper, has two main components: loss rental and constraint rental. This paper develops a method to calculate these different rental components paid by each consumer, by combining the power flow tracing and KKT optimality conditions. This yields quantitative determination of how each consumer has overpaid in the form of loss rental and constraint rental, which in turn can be used to get a better insight of how the rental is accumulated. Simple three-and four-bus systems are used to demonstrate the proposed method. Index Terms--Independent system operator, locational marginal price, network rental, optimal power flow program.

Based on the integer linear programming formulation proposed for optimal PMU placement, this paper presents a generalized integer linear programming formulation for cases including redundant PMU placement, full observability and incomplete observability. Due to accurate voltage phasor measurement and current phasor measurements provided by PUM units, the accuracy, redundancy and thus the robustness of state estimation will be enhanced with the integration of PMU measurements. The problem of optimal placement of PMU for the redundant PMU placement, full observability and incomplete observability analysis needs to be studied, for various purposes and considerations. The proposed modeling approach by the author in another paper, which models PMU placement as an integer linear programming problem, is extended and generalized to satisfy different needs. Cases with and without zero injection measurements are considered. Simulation results on different power systems show that the proposed algorithm can be used in practice. Index Terms--Integer linear programming, observability analysis, phasor measurement units.

This paper presents a new approach to nontechnical loss (NTL) analysis for utilities using the modern computational technique extreme learning machine (ELM). Nontechnical losses represent a significant proportion of electricity losses in both developing and developed countries. The ELM-based approach presented here uses customer load-profile information to expose abnormal behavior that is known to be highly correlated with NTL activities. This approach provides a method of data mining for this purpose, and it involves extracting patterns of customer behavior from historical kWh consumption data. The results yield classification classes that are used to reveal whether any significant behavior that emerges is due to irregularities in consumption. In this paper, ELM and online sequential-ELM (OS-ELM) algorithms are both used to achieve an improved classification performance and to increase accuracy of results. A comparison of this approach with other classification techniques, such as the support vector machine (SVM) algorithm, is also undertaken and the ELM performance and accuracy in NTL analysis is shown to be superior. Index Terms--Classification techniques, extreme machine learning (ELM), nontechnical losses (NTL), support vector machine (SVM).

This paper develops a representation of the Northeastern U.S. bulk electric power system, with an emphasis on New York and New England. The representation has two parts: a 36-bus electrical model in PTI-23 format and market data in the form of generator bids and load demands. The market data are distilled from historical data on public web sites. Since the historical data are available on an hourly basis over many years, the representation is quite rich. In addition, this paper includes the mix of generation at each bus in the model so that generation cost (fuel and emissions) and unit commitment constraints can be deduced. The representation is intended to be a test-bed for formulating, simulating and analyzing the combined technical and economic objectives of the changing electric power industry. It is further intended to be a test-bed for comparing methods of simulating electric power systems and electricity markets operating under engineering constraints. It can, for example, be used for power flow, optimal power flow, reliability, market clearing, and other economic studies. The representation as described is intended only for steady-state equilibrium studies and does not account for inter-temporal effects such as unit commitment constraints. It can, however, be extended to account for those effects. Index Terms--Electric power test systems, electricity markets, engineering and economics of electric power systems, power systems economics.

The Swedish energy agency (STEM) has developed a regulatory model to supervise the revenues of the distribution system operators (DSO). The model is referred to as the network performance assessment model (NPAM). The NPAM calculates customer values for a fictive electrical distribution system, with a total cost referred to as the network performance assessment (NPA). The debiting rate for a DSO is defined by the quotient of the revenue and the NPA. If the debiting rate is higher than a certain value, the DSO is placed under review and could be forced to pay back revenue to customers. A lawsuit is currently in progress on this use of the NPAM. This paper shows results from a comprehensive sensitiveness study of the NPAM investigating the robustness of the model. The investigation shows that the model is not robust, since small stochastic variations in input data could lead to larger differences in the results than those from the model. For example, it is shown that a five-meter difference in the coordinates of the nodes in the reference system could result in a difference of 5 million Euros, i.e., approximately US $6.5 million. The understanding of weaknesses in the NPAM presented in this paper provides an important means for future developments of regulatory models in the world. Index Terms--Customer value, electrical distribution system, network performance assessment model (NPAM), outage cost, performance-based regulation, probability, redundancy, reference networks, regulatory model, robustness and reliability.

This paper investigates the issues of reactive power must-run capacity in power system operations, hence in electricity markets. A must-run index-based method is proposed in the paper to measure the market power held by reactive power suppliers. The Nordic 32-bus system and the IEEE 118-bus system are used to test the proposed method. The market power holders of reactive power found using the proposed method are in accord with that found in the realistic Nordic system operation and in the existing analysis of IEEE 118-bus system. The paper identifies through must-run indices possible conditions that could lead to market power in the case of applying a bid structure within a market framework. Furthermore, market structure drawbacks can cause the appearance of market power even in a topologically ideal system. Index Terms--Electricity market, market power, must-run index, reactive power.

This paper analyzes the implementability of locational marginal price (LMP) and financial transmission right (FTR) mechanisms in the presence of high voltage dc (HVDC) lines in the regulated (i.e., under the control of system operator) network. The established framework of LMP-FTR mechanism assumes that the system under regulation is fully ac. Unregulated (or private) HVDC lines are taken into account within this framework through proxy-transaction bids from the line owners. However, as the flow over a regulated HVDC line has to be controlled by the system operator himself, the existing LMP-FTR framework becomes insufficient if the system contains or is expanded with regulated HVDC lines. The augmentation that should be made to the existing framework to include regulated HVDC lines is explained in this paper. It is shown that the flow over a regulated HVDC line can be modeled as a non-chargeable bilateral transaction without causing any threat of negative congestion surplus. For this power dispatch model, revenue adequacy of FTRs can be still ensured by means of the conventional simultaneous feasibility test (SFT) model. By utilizing the capacities of dc lines, a more general SFT model is further developed. The modified auction problem is discussed and tested for the non-negativity of net auction collection. The process of revenue adequate issuance of auction revenue rights is explained. Finally, the relative merit of a regulated HVDC line over a private HVDC line is discussed through a case study. Index Terms--Congestion management, financial transmission right, high voltage dc transmission, locational marginal price.

Analytical description of the design of individual load-shedding schemes against voltage collapse in the Hellenic System is presented in this paper. Analysis and simulation results that validate the efficiency of these protection schemes are provided. This information may prove helpful for the design of similar load-shedding schemes in the future. Two event-driven load-shedding schemes based on design strategies proposed in this paper have been already implemented in the Hellenic System. Index Terms--Emergency control, load shedding, security assessment, system protection schemes, voltage stability.

This paper quantifies the capability of providing a short-term excess active power support of a commercial multi-megawatt variable speed wind turbine (VSWT) and generalizes the findings by considering different wind turbine (WT) physical parameters in a wider range from the example case. The paper also identifies some possible applications of it, in particular, in a hydro dominated system. To be able to quantify the system characteristic, a delay model of the studied hydro system is developed. Due to the fact that the initial power surge of a hydro turbine is opposite to that desired, the short-term extra active power support from a wind farm (WF) could be beneficial for a hydro dominated system in arresting the initial frequency fall, which corresponds to an improvement in the system temporary minimum frequency (TMF). The improvements in the TMF are calculated by using both the developed delay model and a detailed model, and the results show good agreement. It is shown that the WT under consideration can provide a 0.1 pu extra active power support for 10 s quite easily which is twice the Hydro-Quebec requirement. Index Terms--Delay model, hydro turbine, inertia, load frequency control (LFC), non-minimum phase system, primary frequency control, rotational energy, steam turbine, variable speed wind turbine, wind turbine modeling.

There has been a fast growing demand for the application of doubly fed induction generators (DFIG) in wind power plants in recent years. They have in particular dominated the market in last two years. DFIG is an ideal candidate to satisfy the requirements of the recently proposed challenging grid codes. However, many uncertainties still exist or at least there are no published reports regarding validated comprehensive DFIG models. This paper attempts to clarify the existing ambiguities in modelling of DFIG under various operating conditions using the power system analysis package DIgSILENT PowerFactory. This paper uses available DFIG models and investigates/demonstrates the influence of various model parameters and simplifications (for both mechanical and electrical subsystems) on DFIG-based wind plant transient responses. It further explores and compares the performance of different crowbar protection and rotor side converter restart schemes. Realistic operational limits, such as current margins and PWM modulation limits, are taken into account in all simulations. Index Terms--Doubly fed induction generators (DFIG) modelling, transient operation, wind plants.

This paper proposes a mixed-integer stochastic programming approach to the solution of generation and transmission line expansion planning problem including consideration of system reliability. Favorable system reliability and cost trade off is achieved by the optimal solution. The problem is formulated as a two-stage recourse model where random uncertainties in area generation, transmission lines, and area loads are considered. Reliability index used in this problem is expected cost of load loss as this index incorporates duration and magnitude of load loss. The objective is to minimize the expansion cost in the first stage and the operation and expected cost of load loss in the second stage. Due to exponentially large number of system states (scenarios) in large power systems, direct application of the L-shaped algorithm seems impractical. The expected cost of load loss is therefore approximated by considering only sampled scenarios and evaluated in the optimization. The estimated objective value is called sample-average approximation (SAA) of the actual expected value. In this paper, Monte Carlo sampling and Latin hypercube sampling techniques are implemented. Confidence intervals of upper and lower bound are discussed. The method is implemented to an actual 12-area power system for generation expansion planning and transmission line expansion planning. Index Terms--Latin hypercube sampling, Monte Carlo sampling, multi-area power system, power system optimization, reliability, sample-average approximation, stochastic programming, two-stage recourse model.