Search

This paper addresses the problem of a multiyear security constrained hybrid generation-transmission expansion planning. It is assumed that the overall generation requirements of a network are known along the planning horizon, but their allocations are unknown. Moreover the fuel cost throughout the net- work is not uniform. By allocating the overall generation capacity among the grid nodes, and determining the new transmission element additions along the planning horizon, the overall cost of the system is minimized. The problem is formulated as a mixed integer nonlinear programming problem, which for a large-scale system is very difficult to solve. In this paper a new constructive heuristic approach is proposed, so that the problem can be readily solved. To assess the capabilities of the proposed approach, two networks are studied: the Garver test grid as a small grid and the Iranian power grid as a large-scale grid. [ABSTRACT FROM AUTHOR]

This paper proposes a chance constrained formulation to tackle the uncertainties of load and wind turbine generator in transmission network expansion planning. A combined Monte Carlo simulation/analytical probabilistic power flow analysis method is first presented to obtain the probability density function of wind turbine generator output. The paper then shows the development of the chance constrained formulation with the inclusion of the wind turbine generator probability density function and probabilistic power flow in the formulation. The proposed formulation is more computationally efficient and can deal with uncertainties in transmission network expansion planning. The power of the new method is shown through the application of the formulation to two test systems. [ABSTRACT FROM AUTHOR]

Conventional measurement and verification for non-interval metered, direct load control (DLC) programs bidding into wholesale electricity markets usually requires a PURPA-compliant load research study. This requirement con- tributes to high operating costs and has been a factor in recent reductions in the amount of emergency demand response available to regional transmission system operators. This paper describes. a collaborative effort by PJM members to determine whether regional modeling using pooled historical data could satisfy DLC measurement and verification (M&V) requirements without sacrificing estimation accuracy. This paper also describes how PJM incorporated the regional "deemed savings estimates" into its Load Data Systems Manual. This paper concludes that regional approaches to MଦV could yield large cost savings for DLC resource providers around the country. [ABSTRACT FROM AUTHOR]

In a restructured power market, the independent system operator (ISO) executes the security-constrained unit commitment (SCUC) program to plan a secure and economical hourly generation schedule for the day-ahead market. This paper introduces an efficient SCUC approach with ac constraints that obtains the minimum system operating cost while maintaining the security of power systems. The proposed approach applies the Benders decomposition for separating the unit commitment (UC) in the master problem from the network security check in sub- problems. The master problem applies the augmented Lagrangian relaxation (LR) method and dynamic programming (LW) to solve UC. The subproblem checks ac network security constraints for the UC solution to determine whether a converged and secure ac power flow can be obtained. If any network violations arise, corresponding Benders cuts will be formed and added to the master problem for solving the next iteration of UC. The iterative process will continue until ac violations are eliminated and a converged optimal solution is found. In this paper, a six-bus system and the IEEE 118-bus system with 54 units are analyzed to exhibit the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a method to determine optimal operating strategy for distributed generation (DG) incorporating-reliability worth evaluation of a distribution system. The use of DG for peak shaving could reduce the overall system operating cost and its use as standby power could reduce the customer interruption cost. If the DG operating cost is less than the utility power cost at peak time, DG should be employed to reduce the overall system operating cost. However, when customer interruption cost is also an important concern, standby power strategy for DG may be better peak shaving. The reliability worth and the power cost evaluations are needed to determine whether DG should be operated peak shaving or as standby power. The hourly reliability worth is incorporated in the strategy proposed in this paper to determine the optimal operating decision for the DG. Using the approach proposed in this paper, the distribution companies could determine the optimal operating strategy for their DG. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology to achieve integrated planning and projects for secondary distribution circuits. The planning model is formulated as a mixed integer nonlinear programming problem (MINLP). In order to resolve this problem, a tabu search (TS) algorithm is used, with a neighborhood structure developed to explore the physical characteristics of specific geographies included in the planning and expansion of secondary networks, thus obtaining effective solutions as well as low operating costs and investments. The project stage of secondary circuits consists of calculating the mechanical efforts to determine the support structures of the primary and secondary distribution systems and determining the types of structures that should be used in the system according to topological and electrical parameters of the network and, therefore, accurately assessing the costs involved in the construction and/or reform of secondary systems. A constructive heuristic based on information of the electrical and topological conditions between the medium voltage and low voltage systems is used to connect the primary systems and secondary circuits. The results obtained from planning and design simulations of a real secondary system of electric energy distribution are presented. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the N-i reliable dc optimal dispatch with transmission switching. The model is a mixed integer program (MIP) with binary variables representing the state of the transmission element (line or transformer) and the model can be used for planning and/or operations. We then attempt to find solutions to this problem using the IEEE 118-bus and the RTS 96 system test cases. The IEEE 118-bus test case is analyzed at varying load levels. Using simple heuristics, we demonstrate that these networks can be operated to satisfy N-1 standards while cutting costs by incorporating transmission switching into the dispatch. In some cases, the percent savings from transmission switching was higher with an N-1 DCOPF formulation than with a DCOPF formulation. [ABSTRACT FROM AUTHOR]

This paper presents a stochastic coordination of generation and transmission expansion planning model in a competitive electricity market. The Monte Carlo simulation method is applied to consider random outages of generating units and transmission lines as well as inaccuracies in the long-term load forecasting. The scenario reduction technique is introduced for reducing the computational burden of a large number of planning scenarios. The proposed model assumes a capacity payment mechanism and a joint energy and transmission market for investors' costs recovery. The proposed approach simulates the decision making behavior of individual market participants and the ISO. It is an iterative process for simulating the interactions among GENCOs, TRANSCOs and ISO. The iterative process might be terminated by the ISO based on a pre-specified stopping criterion. The case studies illustrate the applications of proposed stochastic method in a coordinated generation and transmission planning problem when considering uncertainties. [ABSTRACT FROM AUTHOR]

This paper presents an original and effective application of support vector clustering (SVC) to electrical load pattern classification. The proposed SVC-based approach combines the calculation of the support vectors, carried out by using a classical procedure adopting a Gaussian kernel, with a specifically developed deterministic algorithm to form the clusters. This algorithm exploits the meaningful location of the bounded support vectors (BSVs) to define the outliers, identifying the clusters in function of the distance of the non-BSVs to the BSVs. Its implementation is less computationally intensive than other existing approaches and the cluster formation is driven by a single user-defined threshold. Extended comparison to other clustering methods is included to show the effectiveness of the proposed approach in grouping multidimensional load pattern data into non-overlapping clusters. This effectiveness is confirmed by the calculation of various cluster validity indicators. In particular, the most successful tasks are the identification of the outliers and the more effective formation of small numbers of clusters with respect to other methods. [ABSTRACT FROM AUTHOR]

In this paper, the parameters of Rowen's model for heavy duty gas turbines in dynamic studies are estimated by use of available operational and performance data. The work is aimed to create insight into various parts of the model and to introduce a simple and comprehensive procedure to derive the parameters out of simple physical laws, focusing especially on trainers and students who are interested in dynamic models and simulations. A 172-MW simple cycle, single shaft heavy duty gas turbine and its available operational data are also presented and studied for deriving the parameters of the model. Gas turbine parameters are approximated by using simple thermodynamic assumptions, resulting in good correspondence with typical values. The step response of the model is also simulated for few scenarios and is presented. [ABSTRACT FROM AUTHOR]

This paper discusses the impact of utilizing the capability curve of a doubly fed induction generator (DFIG) based wind park on steady state and dynamic power system operation. The interconnection requirements set forth by FERC in order 661-A mandate the operation of wind parks within a power factor range of 0.95 leading and lagging. This operation drastically underutilized the reactive output of the machine. The results presented demonstrate that committing the full reactive capability of a DFIG park for generation dispatch produce a significant reduction in system losses. This additional reactive support was also found to improve post-fault voltage profiles by damping oscillations and preventing overshoots immediately after being subjected to a disturbance. This utilization of extended reactive limits in voltage control may prevent system collapse. [ABSTRACT FROM AUTHOR]

Recently, the authors proposed a clustering approach based on the Fuzzy C-medoid algorithm (FCMdd), for segregating large power systems into coherent electric areas centered around a representative so-called medoid-bus. This bus was shown to be a natural location for PMU in the context of wide-area measurement system (WAMS) configuration for of dynamic vulnerability assessment (DVA). The method was demonstrated on two test systems. The goal of this companion paper is to extend the approach to an actual grid (Hydro-Québec) with more realistic characteristics in terms of geography and system dynamics. We start by developing a formulation of the coherency matrix that is recursive in time to enable online grid partitioning. The FCMdd is then implemented and compared with other statistical learning techniques. It is observed that only FCMdd is able to provide an intuitively appealing 7-clusters solution for 429-bus system. It is further demonstrated that medoids-based system-wise indices can forecast the contingencies severity under varying network configurations and loadings. [ABSTRACT FROM AUTHOR]

Optimal power flow (OPF) belongs to the nonlinear optimization problem with discrete variables. The interior point cutting plane method (IPCPM), which possesses the advantages of both the interior point method and the cutting plane method, becomes a very promising approach to the large-scale OPF. It employs a successive linearization process and iteratively solves the mixed integer linear programming problem. However, case studies have shown that: if the problem has multiple solutions, the optimal solutions will converge to the interior of the optimal face, and the cutting planes cannot be generated due to the failure to identify the optimal base. This paper presents a new general optimal base identification method for solving the problem. The new approach significantly improves the robustness and efficiency of IPCPM. Simulation results on IEEE test systems indicate that the algorithm proposed can not only properly deal with various types of optimal solutions but also greatly enlarge the application area of IPCPM. [ABSTRACT FROM AUTHOR]

This paper introduces a stochastic programming model that integrates strategic bids or offers for electricity (in quantities and prices) in a deregulated electricity market. The model is designed to maximize the profits of a producer of electricity who manages a series of power plants along a river. The model is compared with a previously reported stochastic model where the bidding process is disregarded. The superiority of the new model is empirically demonstrated on historical data. [ABSTRACT FROM AUTHOR]

High penetration of distributed generation (DG) resources is increasingly observed worldwide. The evolution of this process in each country highly depends on the cost of traditional technologies, market design, and promotion programs and subsidies. Nevertheless, as this trend accelerates, higher levels of penetration will be achieved and, in turn, a competitive market integration of DG will be needed for an adequate development of the power sector. This paper proposes a competitive market integration mechanism for DG in a pool-based system. The mechanism encompasses both energy and capacity payment procedures in the wholesale market with DG units located at the distribution level. The proposed model is validated for the current Chilean regulation framework and extended to more general market structures. The model can be considered a novel development on the design of competitive markets for DG resources, which are still dominated by subsidies/compensation schemes. [ABSTRACT FROM AUTHOR]

In restructured power systems, independent system operators (ISOs) or regional transmission organizations (RTOs) execute the security-constrained unit commitment (SCUC) program to plan a secure and economical hourly generation schedule for the daily/weekly-ahead market. As the size of ISO/RTO increases, the current SCUC algorithms could face critical challenges ranging from modeling accuracy to calculation complexity. This paper introduces an efficient fast SCUC (F-SCUC) for large-scale power systems. Main components used in the proposed approach include single-hour unit commitment with network security, single-hour unit commitment adjustment, unit commitment, economic dispatch, and hourly network security check. A reasonable and operational strategy for fixing and unlocking the generating units is explored. The iterative SCUC solution is controlled efficiently to accelerate the execution. Finally, the quality of F-SCUC solution is improved by executing a quick MIP-based SCUC solution according to the F-SCUC results. A 1168-bus system with 169 thermal units, a 4672-bus system with 676 thermal units, and two large systems with 1352 and 2704 thermal units are analyzed to exhibit the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, a novel fast straightforward method for thermal generating units scheduling is presented. The new method decomposes the solution of the unit commitment (UC) problem into three subproblems. In the first subproblem, the quadratic cost functions of units are linearized and hourly optimum solution of UC is obtained considering all constraints except the minimum up/down time constraints. In the second subproblem, the minimum up/down times are enforced through a novel optimization process by modifying the schedule obtained in the first step. Finally, in the third subproblem, the extra reserve is minimized using a new de-commitment algorithm. For testing the proposed method, the conventional ten-unit test system and its multiples with 24-h scheduling horizon have been solved. Comparison of results with those of other methods justifies the effectiveness of the proposed method with regards to minimizing both the total operation cost and execution time. Also, the IEEE 118-bus system with 54 units and a practical large-scale system including 358 units have been analyzed to exhibit the superiority of the proposed approach. [ABSTRACT FROM AUTHOR]

-A power supplier in a pool-based market needs to allocate his generation capacities to participate in contract and spot markets. In this paper, the optimal portfolio selection theory is introduced for this purpose. A model applying this theory is proposed to solve the supplier asset allocation problem. Real market data are used in a numerical study to test the proposed model. The results show that different asset allocation solutions can yield very different risk-return tradeoffs for a supplier, and the proposed method can be potentially useful in suppliers' decision making. [ABSTRACT FROM AUTHOR]

The homogenous earth representation of two-layer earth structures for earth return impedance calculations is investigated in this paper. This representation is based on equivalent resistivity, which takes properly into account the electromagnetic and the geometrical properties of the two earth layers. The equivalent resistivity can be used in the relatively simpler formulas for the earth return calculations for the case of homogenous earth. The new expression is implemented for six actual cases of two-layer earth structures involving combinations of overhead and underground conductors. Results show that the equivalent resistivity approach can lead to significant simplifications in most cases of switching transient simulations in the presence of two-layer earth structures. [ABSTRACT FROM AUTHOR]

Outsourcing of maintenance activities from the core distribution operator business prompted the reorganization of the operations sequence of activities and affects, to some extent, the reliability of the distribution network. Repair times, a major component in the reliability calculations, arrive to a new understanding from operations point of view and the adequacy of established probabilistic representations has to be assessed. This paper proposes a mechanism to identify the layout of the sequence of activities for distribution component repair, resulting from reorganization, and revises the adequate representation of the times associated with various stages of the derived repair process. Statistical-based techniques employing estimates of distribution parameters and hypothesis testing serve to determine probabilistic distributions. The validity of the independence assumption for the random variables associated with individual times which compose the repair time is checked via statistical methods in order to confirm applicability of probabilistic-based calculations. By means of such a mechanism, an objective analysis of the time components of the repair time can be conducted, such as areas of improvement, and can be outlined. The results obtained for a large real power distribution system are presented. [ABSTRACT FROM AUTHOR]

In competitive power systems, investment in generation capacity is left to market participants. As a consequence, due to the special characteristics of electricity, power systems may become unacceptably unreliable during peak demand. One way to solve this problem is self-rationing, a variant of priority service, adapted to a competitive environment. With this concept, consumers subscribe to their anticipated demand for capacity during system peak conditions. When these conditions occur, the individual consumer's demand is limited to subscribed capacity. This paper proposes capacity subscription, self-rationing in a competitive market, as a solution to the challenge of matching generation to peak demand. It is shown that this can be economically efficient. Some illustrations are given, and a framework for market implementation is outlined. With capacity subscription, consumers pay for their individual preferences for uninterrupted supply, thus making the generation adequacy aspect of reliability a private instead of a public good. [ABSTRACT FROM AUTHOR]

In a restructured power system, it is the responsibility of the independent system operator (ISO) to control the power transactions and avoid overloading of the transmission lines beyond their thermal loading megavolt-ampere (MVA) limits. For this, ISO has to update periodically a real-time index termed avail- able transfer capability (ATC). The methods reported to date for ATC determination are unable to cater to either the accuracy or the online CPU time requirements when the system is a large one. This paper proposes a novel method with the full details for determining ATC in a large power system from only three input variables through fuzzy modeling. The method is validated through extensive simulation tests on the standard IEEE 24-bus reliability test system (RTS), and comparison with an ac load flow-based conventional method using the same array of transactions, base cases, and generation/line outages. [ABSTRACT FROM AUTHOR]

The electricity markets are changing the power system operation. The increasing power exchanges make it necessary to operate the transmission grids closer and closer to security limits. A problem posed to power system engineers is therefore to find a suitable methodology to combine the results of both steady-state and dynamic tools: this can reduce the overall computational effort and the difficulty in the interpretation of results. The paper presents a detailed comparison of the computations that can be performed through steady-state and dynamic procedures regarding the power system security. In particular, the analysis of the loadability margins available on the corridor between the Italian power system and the Union for the Coordination of the Transmission of Electricity (UCTE) grids is carried out using both steady-state and dynamic tools; the results are compared, pointing out also the security enhancement given by a hierarchical voltage control. [ABSTRACT FROM AUTHOR]

This paper discusses the pricing of marginal transmission network losses in the locational marginal pricing approach recently deployed in the ISO New England (ISO-NE) standard market design (SMD) project implemented by ALSIOM's T&D Energy Automation and Information (EAI) Business. The traditional loss model is studied and a new model is proposed. The new model achieves more defendable and predictable market-clearing results by introducing loss distribution factors to explicitly balance the consumed losses in the loss!ess dc power system model. The distributed market slack reference is also introduced and discussed. The LMP components produced by the two models are studied and compared under changes in slack reference. Numerical examples are presented to further compare the two models. [ABSTRACT FROM AUTHOR]

An unprecedented process of reforms has shaken the power industry during the last two decades. In order to sell the energy produced by their plants, many generation companies are now forced to prepare and submit daily offers to an electricity market under uncertainty about the offers submitted by their rivals. In this paper, we describe a methodology to prepare optimal offers for a generation company operating in a day-ahead market organized as a series of 24 hourly uniform-price multiunit double auctions. We explicitly consider the ability of the company to affect the price of electricity as well as the company's uncertainty about rival's behavior. [ABSTRACT FROM AUTHOR]

This paper portrays a novel approach based on Lp norms to estimate the unscheduled flows occurring in a wide area interconnected system. Contribution factors for the utilities toward the loop flow scenario are designed based on the participation. This may be used as an effective market tool to establish equitable charge or compensation to utilities. [ABSTRACT FROM AUTHOR]