1,721,166 research outputs found
A Monte Carlo approach to advanced load dispatching in multi-area deregulated systems
No full textProbabilistic methods have been largely employed in the past by vertically integrated utilities for the adequacy assessment of power systems, especially for planning purposes. In the last twenty years, with the introduction of deregulated structures, the security assessment of the working point defined by the energy markets has become one of the main tasks of any System Operator (SO), in the framework of the so-called "day-ahead operational planning". The experience previously gathered in the use of probabilistic methods has proved to be very useful, so an increasing number of SOs is reinforcing, with probabilistic tools, the traditional deterministic criteria employed to validate the ex-ante dispatching. Very challenging, promising and discussed, but not yet well-established, is the use of probabilistic tools for real-time decision-support and advanced dispatching; the computational complexity of many time-consuming algorithms has constituted for years a crucial barrier, but nowadays the availability of cheap and fast computers discloses new opportunities also for the on-line security assessment. In this field, the demand for robust and quick decision-making tools, able to support the activities of control rooms, is significant. In fact, the separation of supply, transmission and system supervision has not yet resulted in more stressed operating conditions, but also compelled the SO to justify the real-time selection of balancing resources both from a technical and an economical point of view. That consideration results in a strong need for formalizing in open procedures the skills previously condensed in the experience of operators. In the present paper, a probabilistic technique for real-time security assessment and operational decision-making is proposed and described. The use of a power system simulator, based on a sequential Monte Carlo technique, is applied to advance dispatching purposes, in order to alert the SO if the system reliability is about to decrease, thus anticipating critical contingencies and supporting the control room to find the most cost-effective corrective action. More in detail, starting from the present behaviour of the power system, provided by a state estimator, the simulator investigates what could happen in the following hours if no significant amendment is applied to the dispatching resulting from the market, as corrected by the contingencies already occurred in the previous hours. The software calculates the risk indices associated to this baseline simulation and indicates to the SO the main weakness points of the power system, assessing the operational security both of transmission network and generating park. Then the tool proposes to the SO quick redispatching procedures able to enhance the system reliability, preventing cascadings and load shedding events; the operator is free to start new simulations, in order to investigate the effectiveness and the cost of the actions suggested by the software, as well as the outcome of corrections recommended by his experience. Furthermore, the tool can help the SO to size the additional spinning reserve to be acquired in the very next infra-daily session of the balancing market. A case study relevant to the IEEE Reliability Test System (RTS96) is shown and discussed
Optimized thermal and electrical scheduling of a Large Scale Virtual Power Plant in the presence of energy storages
No full textSmart Grids are often analysed using a top-down approach, i.e. starting from communication and control technologies evolution, to then focus on their effects on active and passive users, in terms of new services, higher efficiency and quality of supply. However, with their bottom-up approach, Virtual Power Plants (VPP) are very promising instruments for promoting an effective integration of Distributed Generation (DG) and energy storage devices as well as valid means for enabling consumers to respond to load management signals, when operated under the supervision of a Scheduling Coordinator. These aggregation factors can be very profitable for the Distributed Energy Resources (DERs) economy and for the energy network itself.
This paper presents a new algorithm to optimize the day-ahead thermal and electrical scheduling of a Large Scale VPP (LSVPP) which contains: a) many small-scale producers and consumers (“prosumers”) distributed over a large territory and b) energy storage and cogeneration processes. The algorithm also takes into account the actual location of each DER in the public network and their specific capability. Thermal and electrical generator models, load and storage devices are very detailed and flexible, as are the rates and incentives framework. Several novelties, with respect to the previous literature, are proposed. A case study results are also described and discussed
On the possible use of probabilistic techniques for purposes of short-term load dispatching
No full textThe security assessment of the working point set by the energy markets is one of the main tasks of any System Operator (SO). The experience of vertically-integrated utilities in the use of probabilistic methods has proved to be very useful also in the new deregulated environment: an increasing number of SOs is presently enforcing with probabilistic tools the deterministic criteria traditionally employed to validate the ex-ante dispatching.
Very challenging, promising and discussed, but not yet well-established, is conversely the use of probabilistic tools also for real-time decision-support and very short-term dispatching. The computational complexity of many time-consuming algorithms has constituted for years a crucial barrier; nowadays, the availability of cheap and fast computers discloses new opportunities for probabilistic techniques also for purposes of on-line security assessment.
In this paper a probabilistic technique for real-time security assessment and operational decisionmaking is proposed and described. The use of a novel power system simulator, based on a Sequential Monte Carlo technique, is applied to very short-term dispatching, in order to alert the SO if the system reliability is about to decrease in the next few hours, thus anticipating critical contingencies and supporting the control room to find the most cost-effective corrective action.
A case study relevant to the IEEE Reliability Test System RTS-96 is shown and discussed
A novel mixed-integer linear algorithm to generate Unit Commitment and dispatching scenarios for reliability test grids
No full textReliability test grids are often used by the analysts to simulate the effect of new possible operational procedures regarding the power system. One of the main problems affecting the use of test grids for reliability studies is that the result of the simulations is strongly dependent not only on the new procedure under investigation, but also on the working point preselected for the simulated grid, in particular in terms of dispatching scenario. In this paper, the use of a sensitivity analysis to separate the two effects is discussed; hence a novel Mixed-Integer Linear Programming (MILP) method is proposed and implemented for providing, with a single Optimal Power Flow, the Unit Commitment and the day-ahead production schedules of a hydro-thermal generating park, as a first stage to perform reliability studies on a given test grid. Operational requirements, like reserve margins and transmission constraints, can be easily tuned to perform sensitivity analyses. The dispatching scenarios are generated assuming a deregulated framework and implementing inside the OPF the rules of day-ahead markets for energy and ancillary services. A mixed deterministic-probabilistic tool for generating bidding strategies is used to simulate the behavior of market players
The influence of wind generation on power system reliability and the possible use of hydrogen storages
No full textThe aim of this study is to simulate the impact of non-programmable generation sources, in particular wind farms, on the reliability of an electric power system. A probabilistic model has been implemented, to evaluate the influence of wind generation on the amount of secondary/tertiary generating reserve, required in a hydro-thermoelectric system to maintain a certain level of reliability.
A case study, calibrated on the electric system of one of the largest Italian islands, shows the critical issues associated with over-generation events, basically due to an underestimation of wind production. Three possible policies, to be adopted during real time by the Independent System Operator in order to face such events, are simulated and discussed in terms of system reliability and costs for balancing operation.
The use of hydrogen storages, managed by the ISO to cope with over-generation contingencies, is proposed and analysed in different scenarios of wind penetration, assessing the payback time of the storage devices also considering the economic implications of system reliability
A probabilistic nodal analysis for helping the System Operator to validate the results of the day-ahead electricity market
No full textThe operating reserve margins of the generating park of an electric power system have been traditionally set up by the System Operator (SO) with deterministic considerations, mainly using the so-called “first contingency security criterion” (N-1). As an alternative, this paper presents a simulation method, based on a probabilistic approach, which uses a sequential Monte Carlo technique to take into account the failure rates of all generating units and transmission power lines. Starting from the production and consumption power profiles just scheduled by the day-ahead energy markets, the real time operation of the power system for the following day can be simulated by the SO, considering normal and contingency conditions.
A daily case study, calibrated on an IEEE test grid, is carried out and discussed, focusing how this technique can be suitably used to evaluate the system reliability as a function of generation reserve margins, load shedding capacity, dispatching rules and emergency procedures
Clearing procedures for day-ahead Italian electricity market: are complex bids really required?
No full textMany technical debates discussed in the last years the market structure that can be considered as optimal for electricity in a deregulated environment. Simplicity and market transparency do not always comply with the intrinsic complexity of the electrical system, due to technical constraints and security requirements. The mechanism for bid selection in the day-ahead market is one of the most discussed topics, because it strongly influences both the economical revenues of operators and the physical feasibility of the dispatching schedules set by the market.
Usual production bids, only detailing hourly prices and quantities (“simple bids”), do not transfer to the clearing mechanism important technical-economical integral constraints, like the minimum daily revenue required by the operator or the power ramp limitation of generating units; in this case, adjustment sessions follow the primary energy market, to correct undesired or unfeasible outcomes.
In some markets, such additional constraints are already expressed in the so-called “complex bids”, thus avoiding or minimizing the need for adjustment sessions. Nevertheless, the clearing mechanism of the day-ahead market results strongly complicated and the system transparency decreases; the effectiveness of this solution must be then carefully assessed.
In this paper, we present an analysis of the possible quantitative impact of complex bids in the Italian electricity day-ahead market, in order to evaluate possible benefits and drawbacks
Fundamentals of Electric Power Engineering: From Electromagnetics to Power Systems
No full textThis book serves as a tool for any engineer who wants to learn about circuits, electrical machines and drives, power electronics, and power systems basics
From time to time, engineers find they need to brush up on certain fundamentals within electrical engineering. This clear and concise book is the ideal learning tool for them to quickly learn the basics or develop an understanding of newer topics.
Fundamentals of Electric Power Engineering: From Electromagnetics to Power Systems helps nonelectrical engineers amass power system information quickly by imparting tools and trade tricks for remembering basic concepts and grasping new developments. Created to provide more in-depth knowledge of fundamentals—rather than a broad range of applications only—this comprehensive and up-to-date book:
Covers topics such as circuits, electrical machines and drives, power electronics, and power system basics as well as new generation technologies
Allows nonelectrical engineers to build their electrical knowledge quickly
Includes exercises with worked solutions to assist readers in grasping concepts found in the book
Contains “in-depth” side bars throughout which pique the reader’s curiosity
Fundamentals of Electric Power Engineering is an ideal refresher course for those involved in this interdisciplinary branch
Security assessment of the results of the day-ahead electricity market, using a Monte Carlo power system simulator
No full textMany variables are involved in the power system’s reliability assessment, often affected by random events, such as load levels, wind speed and accidental failures of generating units or transmission lines. Furthermore, the presence of a competitive market, which schedules the hourly working point of the electric system, has to be considered and an effective calculation of the reliability level associated to the dispatching schedule defined by the market must be operated by the System Operator (SO) before the actual energy delivery. For this kind of problems, a probabilistic approach, based on sequential Monte Carlo techniques, can be more powerful than analytical methods. In the present paper, a simulation tool for calibrating the amount of generation reserve for the following day is described and analyzed, also discussing the results of a case study based on the IEEE RTS-96 test grid
Analysis of the possible impact of complex bids in the Italian electricity spot market
No full textThe liberalization of the electricity market, already affirmed in many European and worldwide countries, has originated many technical debates over the definition of the market model that can be considered as optimal for electricity. The required simplicity and transparency of market rules often contrast with the intrinsic complexity of the electrical system, due to physical and security requirements. For these reasons, issues related to the mechanism for bid selection in the energy market are one of the most debated during the phase of market rules definition.
In this paper, we present an analysis of the possible quantitative impact of complex bids in the Italian electricity day-ahead market, in order to evaluate benefits and drawbacks
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