A. Monticelli

Electric power system state estimation

This paper discusses the state of the art in electric power system state estimation. Within energy management systems, state estimation is a key function for building a network real-time model. A real-time model is a quasi-static mathematical representation of the current conditions in an interconnected power network. This model is extracted at intervals from snapshots of real-time measurements (both analog and status). The new modeling needs associated with the introduction of new control devices and the changes induced by emerging energy markets are making state estimation and its related functions more important than ever.

State Estimation in Electric Power Systems

The first € price and the £ and

A hierarchical decomposition approach for transmission network expansion planning

price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for Germany, the €(A) includes 10% for Austria. Prices indicated with ** include VAT for electronic products; 19% for Germany, 20% for Austria. All prices exclusive of carriage charges. Prices and other details are subject to change without notice. All errors and omissions excepted. A. Monticelli State Estimation in Electric Power Systems

Network Observability: Theory

This paper presents a hierarchical decomposition approach for optimal transmission network expansion planning. A major difficulty in obtaining global optimal solutions for complex, real-life networks is due to the nonconvexity of the problem. Hierarchical decomposition has proved to be an efficient heuristic for coping with nonconvexity, as illustrated in the test results section of the paper. Significant reductions in investment costs have been obtained in some practical cases for which results are available in the literature. The current implementation of the hierarchical decomposition approach utilizes three different levels of network modeling: transportation models, hybrid models, and linearized power flow models. An initial solution is obtained for the simplest model (transportation model) and as one moves towards the final solution the algorithm successively switches to more accurate models. >

Generalized state estimation

A complete theory of network observability is presented. Starting from a fundamental notion of the observability of a network, a number of basic facts relating to network observability, unobservable states, unobservable branches, observable islands, relevancy of measurements, etc. are derived. Simple and efficient algorithms can be developed based on these basic facts to (i) test network observability, (ii) identify observable islands and (iii) place measurements for observability.

Reliable Bad Data Processing for Real-Time State Estimation

Power system state estimation derives a real-time network model by extracting information from a redundant data set consisting of telemetered, predicted and static data items. This paper describes a generalized, fully developed, estimation approach that fundamentally improves the information extraction process. Its main contribution is the successful inclusion of topology and parameters in the estimation and bad data analysis processes. This is valuable both in the initial commissioning of a state estimator, and in its routine real-time and study mode application. The approach involves a variety of novel concepts and methods. It is usable in weighted least squares (WLS) and other estimation approaches.

Heuristic search approach to distribution system restoration

The weighted least squares performance index test (J(x?) test) conventionally used in power system static state estimation has poor reliability for detecting the presence of measurement errors in the range 3 to 20 standard deviations. This paper describes a very simple alternative method, with considerably improved bad data detection properties, based on evaluating the coherency between the measurement with the largest normalized residual and the remainder of the measurement system. In fact, the detection and identification phases of bad data processing become combined. Inanexistent state estimator using normalized residuals, the cost of implementation of the new method is negligible. The new method has been tested extensively on several power systems, and compared with the J(x?) test.

Studies on Power System Load Flow Equivalencing

Service restoration, service reconfiguration, and other related problems are formulated and solved by heuristic search, which is a search strategy (e.g. depth-first search) armed with practical rules (e.g. based on operator experience) to guide the search. The method is based on operator procedures and usually generates the same solutions as operators would do. However, it is also possible to investigate alternatives that normally would not be considered by system operators, which can be very helpful under certain critical operating conditions. Moreover, the proposed framework makes it possible to investigate the effect of practical rules on the optimality of the final solution and so can be a useful tool in designing new algorithms. Test results are presented, and an illustrative example is given. The preliminary results indicate that the proposed technique is very promising. >

A zero-one implicit enumeration method for optimizing investments in transmission expansion planning

This paper reviews the principles and main methods for load-flow equivalencing, with due emphasis given to on-line applications. Unreduced Load Flow, Ward, REI, Linearization, and Identification methods are covered, introducing a number of new ideas and versions. A critical analysis of the properties of the different methods is made, to assist in choosing the most suitable ones for practical application.

Real-Time External Equivalents for Static Security Analysis

This paper presents a zero-one implicit enumeration method applied to an integer programming subproblem which has to be solved as part of a more general process of obtaining an optimal solution for a transmission expansion planning problem by hierarchical Benders decomposition. The proposed algorithm has been successfully implemented and tested in a real-life system. The reasons why the implicit enumeration approach is particularly suited for the static expansion planning problem are fully discussed in the paper. >