Osvaldo R. Saavedra

Fast decoupled load flow: hypothesis, derivations, and testing

A framework is presented that allows systematic studies on the hypothesis underlying a variety of versions of the fast decoupled load flow method, and their derivation. Decoupling is not seen as merely zeroing coupling submatrices of a full Newton Jacobian matrix. Instead, it is treated as an intelligent two-step procedure that solves the full Newton iteration equations without extra approximations. A new derivation of the standard fast decoupled method is presented, and the mechanisms governing the good performance of the general-purpose version of the method are clarified. Test results and illustrative examples supporting the basic theory are reported. Testing includes studies on very difficult real-life systems, e.g. a 1138 bus transmission system and a 308 bus low-voltage underground distribution system. >

Detection and Identification of Abnormalities in Customer Consumptions in Power Distribution Systems

This paper proposes a computational technique for the classification of electricity consumption profiles. The methodology is comprised of two steps. In the first one, a C-means-based fuzzy clustering is performed in order to find consumers with similar consumption profiles. Afterwards, a fuzzy classification is performed using a fuzzy membership matrix and the Euclidean distance to the cluster centers. Then, the distance measures are normalized and ordered, yielding a unitary index score, where the potential fraudsters or users with irregular patterns of consumption have the highest scores. The approach was tested and validated on a real database, showing good performance in tasks of fraud and measurement defect detection.

Asynchronous programming model for the concurrent solution of the security constrained optimal power flow problem

This paper presents an algorithm for the parallel solution of the security constrained optimal-power flow (SCOPF) problem using an asynchronous programming model. In addition to the increased efficiency, the proposed model allows for the development of applications that can be ported among different parallel computer architectures in a nearly transparent way and without significant loss of computing efficiency. The initial implementation of the approach was made on a 9-processor shared-memory parallel computer; subsequently, the system has been ported to a 64-processor distributed-memory parallel machine. The paper summarizes the results obtained in tests performed with two real-life systems: a network formed by 735 buses, 1212 branches and 76 adjustable power generators (900 contingencies); and a network with 1663 buses, 2349 branches and 99 adjustable generators (1555 contingencies). >

A Cauchy-based evolution strategy for solving the reactive power dispatch problem

Abstract In this work is presented a new proposal for solving the reactive power dispatch. The approach is based on the (μ+λ)-ES paradigm improved by the control of mutations and by using of Cauchy-based mutation rather than the classical Gaussian Mutations (GMs). Others variants are also implemented and a comparative study are performed. Good and reliable performance have been achieved and validation tests using the standard IEEE118 system are reported.

The extension principle and a decomposition of fuzzy sets

We give an algorithm to decompose a fuzzy interval u. Using this decomposition and the multilinearization of a univariate function f, we obtain an approximation of the fuzzy interval , where is obtained from f by applying the extension principle. We provide approximation bounds. Some numeric illustration is provided.

Transmission loss unbundling and allocation under pool electricity markets

This paper presents a methodology based on the circuit theories for unbundling and allocation of transmission losses among the participants of a pool-based electricity market. Starting from a known operation point and using the basic network equations without additional assumptions, an expression of the branch losses based on nodal current injections is derived. Since the power flow equations and circuit theories are satisfied, the methodology turns explicit, in a natural way, separating the losses at each system branch and assigning the responsibility to the respective market participants. It means that the loss allocation of each branch, which is produced by each generator and consumer, is obtained. Extensions and strategies considering unsubsidized and predefined proportion-based loss allocation as well as issues related with the allocation fairness and transparency are also included. Comparisons with previous methods and validation tests of the proposed method are reported by using the IEEE Reliability Test System.

Transmission Network Cost Allocation Based on Circuit Theory and the Aumann-Shapley Method

This paper presents a new method to allocate the costs of the transmission system among generators and loads. The allocation is calculated for each branch of the transmission system to identify and quantify the individual responsibility of generators and loads. A two-step method based on the perfect coupling of the circuit theory with the Aumann-Shapley method is proposed here. First: to determine the participation of the generators in the costs of the transmission network, the generators are modeled as current injections and the loads as impedances. Second: to determine the participation of the loads in the cost of the transmission network, the loads are modeled as current sources and the generators as impedances. The Aumann-Shapley method and the circuit theory are used to calculate the participation of each real and imaginary current component in the “Allocation of the costs of the transmission system” game by considering them as independent agents. The properties of the Aumann-Shapley method ensure equitable allocation and recovery of the total costs. Numerical results are presented and discussed to demonstrate the applicability of the proposed method.

Comparative studies on transmission loss allocation methods for competitive electricity markets

Transmission losses are a significant component of the amount of power to be generated in order to meet the power demand. Today, in competitive operating under pool-based, bilateral contracts or hybrid model, transmission losses must be allocated among the market participants. This process should take in account the buyer and seller spatial locations on the network as well as the non-linear interaction among simultaneous transactions in order to reflect the real market operation and adequate economic efficiencies. In this paper, six recent and relevant methods for transmission loss allocation in power systems operating in a deregulated competitive environment are discussed and compared. Test results using the IEEE14-bus and the standard WSCC 9 bus system are presented. Relevant conclusions, comments and suggestions are also included.

Allocation of transmission loss cost using game theory

This paper presents a novel procedure for the allocation of active and reactive power losses among generators and loads in the transmission grid. The procedure considers the grid as a block, making it unnecessary to analyze the elements within that block. The method allocates the active and reactive power losses jointly by using the circuit theory combined with the game theory (Aumann-Shapley). Arbitrarily, half the losses are allocated to the loads and half to the generators. The method was tested on a 5-bus sample system and on the IEEE 30-bus system. The results show that the method provides a consistent assignment of responsibilities, reflecting the generator and load locations in the grid and in agreement with the circuit laws.

Solution of non-linear fuzzy systems by decomposition of incremental fuzzy numbers

This paper presents a proposal for decomposing large uncertainties associated with fuzzy numbers, which can be useful for solving non-linear fuzzy problems with crisp coefficients. The proposed procedure is based on a property of incremental fuzzy numbers and improves the quality of solution of the linearization process. The methodology is illustrated by some numeric studies.