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IEEE Standard 1366 offers a method for segmenting reliability performance data to isolate the effects of major events from the underlying year-to-year trends in reliability. Recent analysis by the IEEE Distribution Reliability Working Group (DRWG) has found that reliability performance of some utilities differs from the expectations that helped guide the development of the Standard 1366 method. This paper proposes quantitative metrics to evaluate the performance of the Standard 1366 method in identifying major events and in reducing year-to-year variability in utility reliability. The metrics are applied to a large sample of utility-reported reliability data to assess performance of the method with alternative specifications that have been considered by the DRWG. We find that none of the alternatives perform uniformly “better” than the current Standard 1366 method. That is, none of the modifications uniformly lowers the year-to-year variability in System Average Interruption Duration Index without major events. Instead, for any given alternative, while it may lower the value of this metric for some utilities, it also increases it for other utilities (sometimes dramatically). Thus, we illustrate some of the trade-offs that must be considered in using the Standard 1366 method and highlight the usefulness of the metrics we have proposed in conducting these evaluations. [ABSTRACT FROM AUTHOR]

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 se- cure 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. [ABSTRACT FROM AUTHOR]

This paper presents linear models of the most common components in the value chain for CO2 capture and storage. The optimal investment planning of new gas power plants traditionally includes the cost of fuel versus sales of electricity and heat from the plant. If a new power plant also causes additional in- vestments in gas infrastructure, these should be included in the optimization. With the increasing focus on global CO2 emissions, yet another aspect is introduced in theform of technology and infrastructure for capture, transport, and storage of CO2. To be able to include all these aspects in the planning of new power plants, linear models for CO2 capture and storage are formulated consistent with current models for gas, electricity, and heat infrastructures. This paper presents models for the following CO2 infrastructure: source, combined cycle gas turbine producing electricity, heat and exhaust, capture plant, pipeline, liquefaction plant, storage, ship transport, injection pump, and demand/market. [ABSTRACT FROM AUTHOR]

This is the second part of a two-part paper that has arisen from the work of the IEEE Power Engineering Society's Multi-Agent Systems (MAS) Working Group. Part I of this paper examined the potential value of MAS technology to the power industry, described fundamental concepts and approaches within the field of multi-agent systems that are appropriate to power engineering applications, and presented a comprehensive review of the power engineering applications for which MAS are being investigated. It also defined the technical issues which must be addressed in order to accelerate and facilitate the uptake of the technology within the power and energy sector. Part II of this paper explores the decisions inherent in engineering multi-agent systems for applications in the power and energy sector and offers guidance and recommendations on how MAS can be designed and implemented. Given the significant and growing interest in this field, it is imperative that the power engineering community considers the standards, tools, supporting technologies, and design methodologies available to those wishing to implement a MAS solution for a power engineering problem. This paper describes the various options available and makes recommendations on best practice. It also describes the problem of interoperability between different multi-agent systems and proposes how this may be tackled. [ABSTRACT FROM AUTHOR]

This is the first part of a two-part paper that has arisen from the work of the IEEE Power Engineering Society's Multi-Agent Systems (MAS) Working Group. Part I of this paper examines the potential value of MAS technology to the power industry. In terms of contribution, it describes fundamental concepts and approaches within the field of multi-agent systems that are appropriate to power engineering applications. As well as presenting a comprehensive review of the meaningful power engineering applications for which MAS are being investigated, it also defines the technical issues which must be addressed in order to accelerate and facilitate the uptake of the technology within the power and energy sector. Part II of this paper explores the decisions inherent in engineering multi-agent systems for applications in the power and energy sector and offers guidance and recommendations on how MAS can be designed and implemented. [ABSTRACT FROM AUTHOR]

A majority of states has taken steps to regulate the reliability of electricity service, and there is a current regulatory trend focusing on worst-performing feeders (WPFs). This paper performs a comprehensive assessment of worst-performing feeders at Midwest Energy by examining nine years of historical interruption data and validating statistical results with predictive modeling. The paper shows that historical data are able to reflect expected performance but are less able to reflect the risk of worse-than-expected performance. These results raise serious questions as to the usefulness of WPF lists in their present incarnation, and this paper provides recommendations on how utilities can better identify and manage poor-performing feeders. [ABSTRACT FROM AUTHOR]

This paper simulates a pool-based electricity market and identifies equilibrium patterns. A multiperiod framework that requires the use of continuous and binary variables is considered. Producers can be either price-takers or price-makers, although price-makers and their behavior characterize the market. The elasticity of the loads is modeled through piecewise constant price-demand curves. The market operator uses a detailed network-constrained market-clearing auction that results in hourly market-clearing prices. The behavior of the market participants and the market itself are characterized through a repetitive simulation procedure. The tool presented in this paper is particularly useful for the market regulator that may use it to monitor the market and to identify the exercise of market power by producers. Results from a realistic case study arc presented and discussed. [ABSTRACT FROM AUTHOR]

This paper presents an economic model, based on a field-validated load model, for the assessment of impact of conservation voltage reduction (CVR) implemented continuously during both on-peak and off-peak hours. The model evaluates the impact on individual customers and the utility, taking into account the different billing structures, including service class, monthly rates, and reactive power billing. The model considers as well the impact of the utility's revenue decoupling mechanism. The hourly operation of three New York City networks of the Consolidated Edison Company of New York (ConEd) for an entire year has been simulated for the purpose of this study. The results presented for voltage reductions between 2.25% and 8% indicate that for individual customers, the larger the original bill, the greater the relative savings in percentage of the original bill. For the utility, the main advantages are the reduction in aggregated energy consumption and peak power demand with corresponding avoided investment and operating costs. The study and results presented are the first of their kind for a meshed power system. In addition, the economic model presented can be used for any utility system where distribution is separated from generation ownership. [ABSTRACT FROM AUTHOR]

Automotive electrification in the past decade was accompanied by infrastructural changes in the electric power industry. The dual fuel (gasoline and electricity) and dual operation (vehicle to grid (V2G) and grid to vehicle) modes of plug-in hybrid electric vehicles (PHEVs) make them attractive to the automotive and the electric power industries. The value proposition of PHEVs from consumer and automotive perspectives depends on a number of key indicators, such as fuel economy, emissions, battery lifetime, and incremental premium over a hybrid electric (HEV) or a conventional vehicle (CV). In addition, the value proposition of a PHEV from a utility perspective can diverge or even conflict with the consumer or automotive industry perspective. The traditional distance-based utility factor (UF) is primarily used to estimate the vehicle miles that are electrifiable. In this paper, a novel energy-based electrification potential factor (EPF) is proposed to differentiate between travel miles that are electrified and electrifiable. The EPF also acts as a coupling factor that can be also used to assess the overall benefits and impacts of PHEVs from consumer, automotive industry, and utility perspectives. The EPF is developed using existing transportation survey data and detailed simulations using the Powertrain System Analysis Toolkit (PSAT). For different driving profiles and control strategies (charge sustaining, charge depleting, blended, and all electric), the tradeoffs between driving cost and battery lifetime are analyzed. Specific battery lifetime targets are set, and a baseline HEV is used to compare the driving cost savings of the PHEV before determining the EPF. The viability and usefulness of the proposed EPF is demonstrated through comprehensive vehicular simulations and tradeoff analyses. [ABSTRACT FROM PUBLISHER]

In electrical power engineering, reinforcement learning algorithms can be used to model the strategies of electricity market participants. However, traditional value function based reinforcement learning algorithms suffer from convergence issues when used with value function approximators. Function approximation is required in this domain to capture the characteristics of the complex and continuous multivariate problem space. The contribution of this paper is the comparison of policy gradient reinforcement learning methods, using artificial neural networks for policy function approximation, with traditional value function based methods in simulations of electricity trade. The methods are compared using an AC optimal power flow based power exchange auction market model and a reference electric power system model. [ABSTRACT FROM PUBLISHER]

In this paper, an integrated simulation—optimization approach is proposed for annual planning of power restoration workforce related to an electricity distribution company in a province of Canada. Internal and external workforces are employed to perform maintenance actions and restore power after interruptions throughout the province. According to the electricity distribution network, the province is divided into a number of work locations (WL), each having local crews to perform maintenance actions and fix power interruptions. However, determining the size of the crew in each WL over the year is challenging because of high fluctuation in interruption frequency and consequently in projected demand during the year. The frequency of interruptions is affected by various factors such as geographical location, time calendar, and particularly weather conditions. The objective is to determine the optimal combination of internal and external workforce over the year to cover the interruptions across the province with minimum cost and minimum customer interruption duration. [ABSTRACT FROM PUBLISHER]

Generation expansion planning (GEP) is the problem of finding the optimal strategy to plan the construction of new generation plants while satisfying technical and economical constraints. It is a challenging problem due to its nonlinearity, large-scale, and to the discrete nature of the variables describing unit size and allocation. Originally, GEP was faced by vertically integrated utilities with the aim of minimizing production and capital costs. After deregulation, generation companies were forced to consider GEP from the viewpoint of market shares and financial risk. In recent years, increasing concern for environmental protection has driven lots of countries all over the world to promote energy generation from renewable sources. Different incentive systems have been introduced to support the growth of the investments in generation plants exploiting renewable energy. In the present paper, the impact of some of the most popular incentive systems (namely feed-in tariffs, quota obligation, emission trade, and carbon tax) on generation planning is considered, thus obtaining a comprehensive GEP model with a suitably modified objective function and additional constraints. The resulting problem is solved by resorting to the generalized Benders decomposition (GBD) approach and implemented in the Matlab programming language. Tests are presented with reference to the Italian system. [ABSTRACT FROM PUBLISHER]

Plug-in electric vehicles (PEVs) present environmental and energy security advantages versus conventional gasoline vehicles. In the near future, the number of plug-in electric vehicles will likely grow significantly in the world. Despite the aforementioned advantages, the connection of PEV to the power grid poses a series of new challenges for electric utilities. This paper proposes a comprehensive approach for evaluating the impact of different levels of PEV penetration on distribution network investment and incremental energy losses. The proposed approach is based on the use of a large-scale distribution planning model which is used to analyze two real distribution areas. Obtained results show that depending on the charging strategies, investment costs can increase up to 15% of total actual distribution network investment costs, and energy losses can increase up to 40% in off-peak hours for a scenario with 60% of total vehicles being PEV. [ABSTRACT FROM AUTHOR]

It is widely agreed that an increased participation of the demand side in the electricity markets would produce benefits not only for the individual consumers but also for the market as a whole. This paper proposes a method for quantifying rigorously the effect that such an increase would have on the various categories of market participants. A new centralized complex-bid market-clearing mechanism has been devised to take into consideration the load shifting behavior of consumers who do submit price-sensitive bids. The effects of the proportion of demand response on the market are illustrated using a test system with ten generating units scheduled over 24 periods. [ABSTRACT FROM AUTHOR]

This paper focuses on the energy storage system and the power electronic interface included in microsources of the CERTS microgrid. CERTS stands for the Consortium for Electric Reliability Technology Solutions. The consortium was formed in 1999 to research, develop, and disseminate new methods, tools, and technologies to protect and enhance the reliability of the U.S. electric power system and efficiency of competitive electricity markets. To provide the plug-and-play feature and the power quality requirements of the CERTS microgrid, all microsources regardless of their prime mover type must have a unified dynamic performance. This necessitates attaching an energy storage module to some or all of the microsources. The storage module is attached to the prime mover through a power electronic interface that couples the microsource to the microgrid. Details of the energy storage module, the power electronic interface and the corresponding controls are described. Performance of an example microsource, which includes a synchronous generator, a storage module and an electronic interface, is studied. Dynamic performance of the example microsource when operating in the CERTS microgrid is evaluated based on digital time-domain simulations in the EMTP-RV software environment. Effectiveness of the storage module, the electronic interface and the corresponding controls in enhancing the microsource performance is verified. [ABSTRACT FROM AUTHOR]

This paper proposes a practical and effective model for the generation forecasting of a wind farm with an emphasis on its scheduling and trading in a wholesale electricity market. A novel forecasting model is developed based on indepth investigations of meteorological information. This model adopts a two-stage hybrid network with Bayesian clustering by dynamics and support vector regression. The proposed structure is robust with different input data types and can deal with the nonstationarity of wind speed and generation series well. Once the network is trained, we can straightforward predict the 48-h ahead wind power generation. To demonstrate the effectiveness, the model is applied and tested on a 74-MW wind farm located in the southwest Oklahoma of the United States. [ABSTRACT FROM AUTHOR]

This paper presents a loss allocation method based on the circuit theories and the concept of orthogonal projection for pool-based electricity markets. The method first defines the current projection component to determine the share of a generator or load on the current through a branch. Then the power flow through each branch is decomposed and the branch loss allocation is obtained. One feature of the method is that it gives intuitively clear explanation of the obtained loss allocation. The two equivalence modes of bus power injections are also discussed. The analysis shows that the equivalence that loads (generators) are converted into equivalent admittances when generators (loads) are converted into current injections reflects the practical situation and thus it is more reasonable and preferable. Comparisons with other methods and validation tests of the proposed method are provided by using several numerical examples. [ABSTRACT FROM AUTHOR]

This paper proposes an approach coupling security-constrained optimal power flow with time-domain simulation to determine an optimal combination of preventive and corrective controls ensuring a voltage stable transition of the system towards a feasible long-term equilibrium, if any of a set of postulated contingencies occurs. A security-constrained optimal power flow is used to adjust the respective contribution of preventive and corrective actions. Furthermore, information is extracted from (quasi steady-state) time-domain simulations to iteratively adjust the set of coupling constraints used by a corrective security-constrained optimal power flow until its solution is found dynamically secure and viable. Numerical results are provided on a realistic 55-bus test system. [ABSTRACT FROM AUTHOR]

The paper addresses the problem of decentralized optimization for a power system partitioned into several areas controlled by different transmission system operators (TSOs). The optimization variables are the settings for taps, generators' voltages and compensators', and the objective function is either based on the minimization of reactive power support, the minimization of active power losses, or a combination of both criteria. We suppose that each TSO assumes an external network equivalent for its neighboring areas and optimizes without concern for the neighboring systems' objectives its own optimization function. We study, in the context where every TSO adopts the same type of objective function, the performance of an iterative scheme, where every TSO refreshes at each iteration the parameters of its external network equivalents depending on its past internal observations, solves its local optimization problem, and then, applies its "optimal actions" to the power system. In the context of voltage optimization, we find out that this decentralized control scheme can converge to nearly optimal global performance for relatively simple equivalents and simple procedures for fitting their parameters. [ABSTRACT FROM AUTHOR]

Available transfer capability (ATC) is a key index of the remaining capability of a transmission system for future transactions. To calculate the ATC between two areas in an interconnected power system, capacity benefit margin (CBM) is one of the indexes that need to be assessed. CBM ensures security of system operation when the system faces generation deficiency in some areas. In this paper, three new methods are introduced which reflect different objectives for CBM assessment. This provides more flexibility of choices for market participants. In the proposed methods, CBM determination is formulated as an optimization problem and particle swarm optimization (PSO) method is used to solve the problem. The numerical results for modified IEEE reliability test system are presented to demonstrate the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]

Keen interest in the development and utilization of wind-based distributed generations (DGs) has been currently observed worldwide for several reasons. Among those is controlling the emission of environmentally harmful substances, limiting the growth in energy costs associated with the use of conventional energy sources and encouraging the independent power producers for participation in the electricity market system. One of the most important issues is to quantitatively assess the impact of such type of DGs on the distribution system reliability. This paper presents a probabilistic technique to evaluate the distribution system reliability utilizing segmentation concept and a novel constrained Grey predictor technique for wind speed profile estimation. [ABSTRACT FROM AUTHOR]

A recurrent functional-link (FL)-based fuzzy-neural-network (FNN) controller with improved particle swarm optimization (IPSO) is proposed in this paper to control a three-phase induction-generator (IG) system for stand-alone power application. First, an indirect field-oriented mechanism is implemented for the control of the IG. Then, an ac/dc power converter and a dc/ac power inverter are developed to convert the electric power generated by a three-phase IG from variable frequency and variable voltage to constant frequency and constant voltage, respectively. Moreover, two online-trained recurrent FL-based FNNs are introduced as the regulating controllers for both the dc-link voltage of the ac/dc power converter and the ac line voltage of the dc/ac power inverter. Furthermore, IPSO is adopted to adjust the learning rates to improve the online learning capability of the recurrent FL-based FNNs. Finally, some experimental results are provided to demonstrate the effectiveness of the proposed recurrent FL-based FNN-controlled IG system. [ABSTRACT FROM AUTHOR]

Abstract-This paper presents a direct current-space-vector control of an active power filter (APF) based on a three-level neutral-point-clamped (NPC) voltage-source inverter. The proposed method indirectly generates the compensation current reference by using an equivalent conductance of the fundamental component using APF's dc-link voltage control. The proposed control can selectively choose harmonic current components by realtime fast Fourier transform to generate the compensation current. The compensation current is represented in a rotating coordinate system with chosen switching states from a switching table implemented in a field-programmable gate array. In addition, a threephase four-wire APF based on a three-level neutral-point-clamped inverter is also presented. The proposed APF eliminates harmonics in all three phases as well as the neutral current. A three-phase three-wire NPC inverter system can be used as a three-phase fourwire system since the split dc capacitors provide a neutral connection. To regulate and balance the split dc-capacitor voltages, a new control method using a sign cubical hysteresis controller is proposed. The characteristics of the APF system with an LCL-ripple filter are investigated and compared with traditional current control strategies to evaluate the inherent advantages. The simulation and experimental results validated the feasibility of the proposed APF. [ABSTRACT FROM AUTHOR]

A generation planning framework is developed for a competitive, energy-only electricity market. The framework developed combines decentralized merchant investment plans stemming from market signals and technological preferences, with centralized resource planning concepts to decide optimal time-ordered investment decisions. The investment decisions maximize the new entrants' net surpluses and minimize the consumer interruption cost, accounting for many uncertain variables and technical details. The optimal plan given by the main centralized framework represents the system planner's solution derived from the set of decentralized plans. An illustrative case study is given in the paper, applying the proposed framework to the Queensland region of the National Electricity Market of Australia. [ABSTRACT FROM AUTHOR]

The rise in temperatures induced by climate change may have important implications for Thailand's electricity demand. This paper investigates how changing climate will affect Thailand's daily, seasonal, and long-term electricity demand. Regression models are applied to capture daily load patterns across each month in the year. Temperature projections from the UK Hadley Centre climate model are then used to assess hourly sensitivity to changes in mean temperatures and diurnal temperature range. These are combined with four representative socioeconomic scenarios from the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios to project absolute changes in Thailand's electricity demand. The specific climate and socioeconomic scenarios considered here indicate that mean annual temperatures in Thailand will rise by 1.74 to 3.43° C by 2080, implying increases in Thai peak electricity demand of 1.5%-3.1% in the 2020s, 3.7%-8.3% in the 2050s, and 6.6%-15.3% in the 2080s. [ABSTRACT FROM AUTHOR]

Power processing systems will be a key factor of future photovoltaic (PV) applications. They will play a central role in transferring, to the load and/or to the grid, the electric power produced by the high-efficiency PV cells of the next generation. In order to come up the expectations related to the use of solar energy for producing electrical energy, such systems must ensure high efficiency, modularity, and, particularly, high reliability. The goal of this paper is to provide an overview of the open problems related to PV power processing systems and to focus the attention of researchers and industries on present and future challenges in this field. [ABSTRACT FROM AUTHOR]

This paper presents a transformerless three-phase inverter designed for the integration into a special type of a photovoltaic (PV) module, which is capable of providing an output voltage of several hundred volts. The chosen topology, a current-source inverter, features a single-stage power conversion system that directly feeds into the grid. The principle operation and control is described, and a modified modulation strategy is proposed to attenuate common-mode currents. A robust and highly efficient laboratory prototype of a 250-W module integrated converter has been implemented and tested. Its compact and flat design allows the direct attachment to the PV module. [ABSTRACT FROM AUTHOR]

This paper presents a high-performance maximum power point tracker (MPPT) optimized for fast cloudy conditions, e.g., rapidly changing irradiation on the photovoltaic panels. The rapidly changing conditions are tracked by an optimized hill-climbing MPPT method called dP-P&O. This algorithm separates the effects of the irradiation change from the effect of the tracker's perturbation and uses this information to optimize the tracking according to the irradiation change. The knowledge of the direction of the irradiation change enables the MPPT to use different optimized tracking schemes for the different cases of increasing, decreasing, or steady irradiance. When the irradiance is changing rapidly this strategy leads to faster and better tracking, while in steady-state conditions it leads to lower oscillations around the MPP. The simulations and experimental results show that the proposed dP-P&O MPPT provides a quick and accurate tracking even in very fast changing environmental conditions. [ABSTRACT FROM AUTHOR]

One of the major drawbacks of photovoltaic (PV) systems is represented by the effect of module mismatching and of partial shading of the PV field. Distributed maximum power point tracking (DMPPT) is a very promising technique that allows the increase of efficiency and reliability of such systems. Modeling and designing a PV system with DMPPT is remarkably more complex than implementing a standard MPPT technique. In this paper, a DMPPT system for PV arrays is proposed and analyzed. A dc and small-signal ac model is derived to analyze steady-state behavior, as well as dynamics and stability, of the whole system. Finally, simulation results are reported and discussed. [ABSTRACT FROM AUTHOR]

Maximum power point tracking (MPPT) techniques are employed in photovoltaic (PV) systems to make full utilization of PV array output power which depends on solar irradiation and ambient temperature. Among all the MPPT strategies, the incremental conductance (INC) algorithm is widely used due to the high tracking accuracy at steady state and good adaptability to the rapidly changing atmospheric conditions. In this paper, a modified variable step size INC MPPT algorithm is proposed, which automatically adjusts the step size to track the PV array maximum power point. Compared with the conventional fixed step size method, the proposed approach can effectively improve the MPPT speed and accuracy simultaneously. Furthermore, it is simple and can be easily implemented in digital signal processors. A theoretical analysis and the design principle of the proposed method are provided and its feasibility is also verified by simulation and experimental results [ABSTRACT FROM AUTHOR]

This paper presents a power inverter tailored for low-power photovoltaic (PV) systems. The inverter features high reliability, thanks to a circuit topology that obviates aluminum electrolytic capacitors from the circuit. Moreover, all components, including logic and control, have been designed to exhibit high reliability at high temperatures. Three conversion stages form the power topology. First, a full bridge connected to a high-frequency transformer and a full-bridge rectifier amplifies the voltage of the PV panel to approximately 475 V. This stage is controlled by using a phase-shift pulsewidth-modulation controller that permits zero-voltage switching, thereby minimizing losses. Second, a buck converter is connected in series with the rectifier and is controlled by using current mode in order to shape the current injection into a rectified sine wave. Last, a full bridge is operated at line frequency to unfold the current injection. The amplification stage has a proportional compensator that maintains the voltage at the PV terminals constant. The current injection stage has a proportional-derivative compensator that controls the amplitude of the grid current so that the dc-link average voltage is maintained constant. Experimental results show that the peak efficiency of the system is 89%, and the total current harmonic distortion is below 5%. Finally, analyses show a designed lifetime of approximately ten years. [ABSTRACT FROM AUTHOR]

In evaluating the energy-generation potential of a photovoltaic (PV) energy system, the system is usually assumed to work without interruptions over its entire life. PV energy systems are fairly reliable, but as any complex system, they may fail. In PV systems, the inverter is responsible for the majority of failures, and most inverter failures are blamed on the aluminum electrolytic capacitors typically used in the dc bus. This paper investigates the effects of common failure modes on the reliability of PV inverters and suggests a model framework for decomposing the inverter into subsystems for more detailed study. The challenges of statistical analysis based on small data sets are discussed, and simulations are performed to illustrate the proposed model using a simple decomposition into subsystems of the inverter used in the 342-kW PV system at the Georgia Tech Aquatic Center. [ABSTRACT FROM AUTHOR]

A recently proposed concept of simultaneous ac-dc power transmission enables the long extra high-voltage ac lines to be loaded close to their thermal limits. The conductors are allowed to carry a certain amount of dc current superimposed on usual ac. This paper presents the feasibility of small power tapping from composite ac-dc power transmission lines which would pass over relatively small communities/rural areas having no access to a major power transmission network. The proposed scheme is digitally simulated with the help of a PSCAD/EMTDC software package. Simulation results clearly indicate that the tapping of a small amount of ac power from the composite ac-dc transmission line has a negligible impact on the normal functioning of the composite ac-dc power transmission system. [ABSTRACT FROM AUTHOR]

The introduction of new energy carriers, such as natural gas and district heating, to energy systems dominated by electrical power will certainly relieve stress on the power system. Some of the end uses initially served by the power system will be gradually decoupled and served by alternative energy carriers. As a result, the specific customer interruption costs and load profiles will change. In this paper, we analyze how the optimal level of switchgear in electric power distribution systems is affected by such changes. The proposed optimization method is based on a genetic algorithm and takes into account the constrained network capacity. [ABSTRACT FROM AUTHOR]

Optimal pricing in electricity markets has emerged as a multifunctional task for the grid managers as well as a major concern for the electricity providers and users. In this paper an optimal power flow problem is developed to take into account wider dimensions of the task by linking short-term and long-term performances of power systems via security pricing. The emphasis here is on the voltage stability phenomena as a security cost. The stochastic nature of power systems is taken into account to overcome the conservativeness associated with the severest single contingency approaches. This is done by inserting the approximated discrete processed risk data into the problem as a spline function to avoid lengthy iterative solutions. An effective combined offline and online procedure is then proposed to solve the optimization problem via the interior point method, preserving both the swiftness and precision of the solution. The effectiveness of the proposed problem definition and solution is confirmed through calculating locational marginal prices for a benchmark power system. [ABSTRACT FROM AUTHOR]

One of the main characteristics of wind power is the inherent variability and unpredictability of the generation source, even in the short-term. To cope with this drawback, hydro pumped-storage units have been proposed in the literature as a good complement to wind generation due to their ability to manage positive and negative energy imbalances over time. This paper investigates the combined optimization of a wind farm and a pumped-storage facility from the point of view of a generation company in a market environment. The optimization model is formulated as a two-stage stochastic programming problem with two random parameters: market prices and wind generation. The optimal bids for the day-ahead spot market are the "here and now" decisions while the optimal operation of the facilities are the recourse variables. A joint configuration is modeled and compared with an uncoordinated operation. A realistic example case is presented where the developed models are tested with satisfactory results. [ABSTRACT FROM AUTHOR]

EIectroIytic process, employed for manufacturing basic chemicals like caustic soda and chlorine, is highly energy intensive. Due to escalating costs of fossil fuels and capacity addition, the electricity cost has been increasing for the last few decades. Electricity intensive industries find it very difficult to cope up with higher electricity charges particularly with time-of-use (TOU) tariffs implemented by the utilities with the objective of flattening the load curve. Load management programs focusing on reduced electricity use at the time of utility's peak demand, by strategic load shifting, is a viable option for industries to reduce their electricity cost. This paper presents an optimization model and formulation for load management for electrolytic process industries. The formulation utilizes mixed integer nonlinear programming (MINLP) technique for minimizing the electricity cost and reducing the peak demand, by rescheduling the loads, satisfying the industry constraints. The case study of a typical caustic—chlorine plant shows that a reduction of about 19% in the peak demand with a corresponding saving of about 3.9% in the electricity cost is possible with the optimal load scheduling under TOU tariff. [ABSTRACT FROM AUTHOR]

Ancillary service markets are a very important part of the Standard Market Design and are under development or implementation on a centralized basis in major U.S. electricity markets. This paper presents the market clearing framework for the co-optimized real-time energy-reserve market that has been developed and implemented in the ISO New England (ISO NE). In this co-optimized market clearing model, reserve, products are procured on a zonal basis to satisfy the first and the second contingency protection criteria required by the ISO NE's real-time operations for both the entire area and typical import-constrained areas. The proposed zonal reserve model is derived from simulating each contingency event in the predefined reserve zones. Differing from standard industrial practices, the proposed zonal reserve model recognizes reserve deliverability for nested reserve zones and allocates the zonal total transfer capability between energy and reserves in an economic way. Numerical examples for a two-zone system are presented to demonstrate the validity of this modeling technique. [ABSTRACT FROM AUTHOR]

In sinusoidal situations, power factor definition is unique and expressive. However in nonsinusoidal situations and/or nonlinear load different power factors are proposed to express these situations. In this paper a new fuzzy based Representative Quality Power Factor is introduced to represent these power factors. The proposed Representative Quality Power Factor (RQPF) was applied to different cases, linear, nonlinear, sinusoidal, nonsinusoidal considering lagging and leading power factor. It is shown that the new RQPF is expressive and accurately represents the existing power factors in all cases and in all situations. Taking into consideration the advantages of the fuzzy systems such as simplicity, ease of application, flexibility, speed and ability to deal with imprecision and uncertainties, this factor can be useful for power quality evaluation, cost-effective analysis of PQ mitigation techniques, as well as billing purposes, in these situations. [ABSTRACT FROM AUTHOR]

This paper proposes a technique for partitioning a large power system into a number of coherent electric areas for possible application to dynamic vulnerability assessment. The coherency concept and a fuzzy clustering algorithm grouping of buses are combined to achieve this goal. The clusters are obtained by selecting representative buses from the data set in such a way that the total fuzzy dissimilarity within each cluster is minimized. The initialization problem of the conventional Fuzzy c-means algorithm, which usually leads to multiple solutions, is suitably tackled by incorporating the maximum-dissimilarity based sequential Phasor Measurement Unit (PMU) placement technique. Results of bus grouping for two test systems of three and nine areas demonstrate the potential of the approach. It is observed that such an approach to bus grouping results in a PMU configuration with minimum number of devices and fast data aggregation for a wide-area measurement system. [ABSTRACT FROM AUTHOR]

Competitive electricity markets have been operating in various countries for more than a decade, with every single electricity market presenting its own unique characteristics and features. This paper provides a comprehensive overview of the operational aspects of the Ontario electricity market, its unique features, and its outcomes for the first four years of operation. Several programs implemented in the Ontario market to improve efficiency, transparency, and competitiveness are analyzed, and the effectiveness of these programs are discussed. [ABSTRACT FROM AUTHOR]

The risk of blackouts is inherent in complex power systems, despite all efforts to prevent their occurrence. To mitigate the consequences of major blackouts, better restoration plans have been demanded. Commonly, these plans consist of a set of actions textually described. In order to enhance the operating staff comprehension about the restoration plan, this paper proposes a methodology, based on CPM/PERT graph theory, that allows power system restoration plans to be graphically visualized. This approach permits to clearly see the precedence relations among activities and to graphically follow the restoration process during its execution. The methodology can also take advantage of calculations involved with CPM/PERT methods to evaluate the restoration duration and the plan critical path. The application of the proposed approach is illustrated using the IEEE 30-bus network and the restoration plan developed for a portion of the Brazilian interconnected power system. [ABSTRACT FROM AUTHOR]

This paper describes a new Fourier-based sliding window method for estimating the damping of exponentially decaying modes that occur in power networks as a result of electric disturbances. The key innovation in the new method is the use of multiple orthogonal sliding windows rather than just a single pair of sliding windows. The use of these multiple orthogonal windows allows least-squares averaging strategies to be used, enabling lower variance estimates to be obtained as a result. A statistical analysis is provided, and simulations are presented to illustrate the effectiveness of the new method. The technique is also applied to real power system data. [ABSTRACT FROM AUTHOR]

Increasing numbers of very small generators are being connected to electricity distribution systems around the world. Examples include photovoltaics (PV) and gas-fired domestic-scale combined heat and power (micro-CHP) systems, with electrical outputs in the region of 1 to 2 kW. These generators are normally installed within consumers' premises and connected to the domestic electricity supply network (230 V single-phase in Europe, 120 V in North America). There is a growing need to understand and quantify the technical impact that high penetrations of such generators may have on the operation of distribution systems. This paper presents an approach to analyzing this impact together with results indicating that considerable penetrations of micro-generation can be accommodated in a typical distribution system. [ABSTRACT FROM AUTHOR]

In a competitive electricity market, a generation company (Genco) can manage its trading risk through trading electricity among multiple markets such as spot markets and contract markets. The question is how to decide the trading proportion of each market in order to maximize the Genco's profit and minimize the associated risk. Based on the mean-variance portfolio theory, this paper proposes a sequential optimization approach to electric energy allocation between spot and contract markets, taking into consideration the risks of electricity price, congestion charge, and fuel price. Especially, the impact of the fuel market on electric energy allocation is analyzed and simulated with historical data in respect of the electricity market and other fuel markets in the U.S. Simulation results confirm that the proposed analytic approach is consistent with intuition and therefore reasonable and feasible for a Genco to make a trading plan involving risks in an electricity market. [ABSTRACT FROM AUTHOR]

Due to dispersed locations and various capacities, emerging Distributed Resources (DR's) have diverse and highly nonlinear impact (Contribution Factor, CF) on transmission operation constraints, thereafter on congestion management in electricity markets. From the perspective of Independent System Operators (ISO's) and Distribution Companies (DISCO's), it is crucial to address such impacts in order to identify the "desirable" and "undesirable" DR's. This paper introduces a straightforward-partitioning space, ITDA, developed by a fuzzy c-means clustering approach based on accurate CF's derived from AC power flow. Case studies with 6-bus and 30-bus test systems demonstrate that the proposed technique is simple and applicable. [ABSTRACT FROM AUTHOR]

This paper proposes a novel technique to forecast day-ahead electricity prices based on the wavelet transform and ARIMA models. The historical and usually ill-behaved price series is decomposed using the wavelet transform in a set of better-behaved constitutive series. Then, the future values of these constitutive series are forecast using properly filled ARIMA models. In turn, the ARIMA forecasts allow, through the inverse wavelet transform, reconstructing the future behavior of the price series and therefore to forecast prices. Results from the electricity market of mainland Spain in year 2002 are reported. [ABSTRACT FROM AUTHOR]

A common approximation used in the derivation of the Transient Energy Functions (TEFs) for AC/DC power systems is the omission of HVDC dynamics. The differential equations that represent HVDC dynamics are used to find the fault-on trajectory but not to derive the TEE This leads to an error in TEF-based stability prediction. In this paper, a method is presented to derive the TEF with HVDC dynamics included. By using this improved TEF, the accuracy of the stability prediction in AC/DC systems is improved. In addition, due to the inclusion of differential equations that represent HVDC dynamics in the TEF, the calculation of the post-fault Stable Equilibrium Point (SEP) must be done only once. This reduces the CPU time required to find the Transient Energy Margin (TEM). The method is validated using several test systems by comparing results with those obtained from time simulation. The new transient energy function is used in a number of studies to establish its usefulness. [ABSTRACT FROM AUTHOR]

Price forecasting is becoming increasingly relevant to producers and consumers in the new competitive electric power markets. Both for spot markets and long-term contracts, price forecasts are necessary to develop bidding strategies or negotiation skills in order to maximize profits. This paper provides an approach to predict next-day electricity prices based on the Generalized Autoregressive Conditional Heteroskedastic (GARCH) methodology that is already being used to analyze time series data in general. A detailed explanation of GARCH models is presented and empirical results from the mainland Spain and California deregulated electricity-markets are discussed. [ABSTRACT FROM AUTHOR]

For the past century the autotransformer, or "Korndorfer" starter, has been a standard in the electrical industry. How- ever, for more than the past 30 years the autotransformer starter has been experiencing unexplained "high-voltage stress" failures in typical applications. These failures have been reported on 2400-V starters from South America to 11000-V starters in the North Sea. In most cases, the zero tap or the turns close to the zero tap are involved in the failure. This paper discusses the failure mode and the corrective action that prevents "high-voltage stress" failures. [ABSTRACT FROM AUTHOR]