A survey is presented of publications in the fields of optimal power flow and dispatching. It suggests a classification of methods based on the choice of optimization techniques. The survey is summarized in a single flow-chart-type figure, which indicates the relationship between methods, their chronology, and their popularity. This figure is based on a compilation of over three hundred publications. >

A survey of the optimal power flow literature

In this paper, we formulate the problem of finding an optimal generation dispatch and transmission topology to meet a specific inflexible load as a mixed integer program. Our model is a mixed-integer linear program because it employs binary variables to represent the state of the equipment and linear relationships to describe the physical system. We find that on the standard 118-bus IEEE test case a savings of 25% in system dispatch cost can be achieved.

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Optimal Transmission Switching

State-of-the-art, challenges, and future trends in security constrained optimal power flow

In this paper, we analyze the N-1 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

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Optimal Transmission Switching With Contingency Analysis

Currently, there is a national push for a smarter electric grid, one that is more controllable and flexible. The full control of transmission assets are not currently built into electric network optimization models. Optimal transmission switching is a straightforward way to leverage grid controllability: to make better use of the existing system and meet growing demand with existing infrastructure. Previous papers have shown that optimizing the network topology improves the dispatch of electrical networks. Such optimal topology dispatch can be categorized as a smart grid application where there is a co-optimization of both generators and transmission topology. In this paper we present a co-optimization formulation of the generation unit commitment and transmission switching problem while ensuring N-1 reliability. We show that the optimal topology of the network can vary from hour to hour. We also show that optimizing the topology can change the optimal unit commitment schedule. This problem is large and computationally complex even for medium sized systems. We present decomposition and computational approaches to solving this problem. Results are presented for the IEEE RTS 96 test case.

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Co-Optimization of Generation Unit Commitment and Transmission Switching With N-1 Reliability

The method presented allows the determination of the optimal and n-1 secure power system state by switching operations. A linear switching model is applied in an active way to model the control actions and in a more passive way to set up contingency constraints. Using the switching model in a dual role permits the integration of contingencies and control actions into one optimization algorithm. Thus, with exactly one optimization step the power system can be improved considering various security levels. A comparison is made between preventive conservative and postcontingency rescheduling. The main difference lies in the time-dependent performance of the topology changes in establishing a normal undisturbed system state if any contingency occurs. The preventive way of rescheduling has the advantage that there are no limit violations produced by a contingency. In postcontingency rescheduling short-term overloads are tolerated. This system state has the advantage of lower production costs. The performance of the algorithm is shown in a test case. >

G. Schnyder

Papers

Security enhancement using an optimal switching power flow