H. Glavitsch

Bio: H. Glavitsch is an academic researcher from ETH Zurich. The author has contributed to research in topics: Electric power system & Optimization problem. The author has an hindex of 5, co-authored 5 publications receiving 271 citations.

Security enhancement using an optimal switching power flow

Abstract: 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. >

Loss reduction by network switching

Abstract: Systematic and fast switching for the purposes of reducing losses in power transmission networks is treated as an optimization problem whereby switching is to be understood in a general and comprehensive way. Injected currents applied to a base network are used to model the switching operation. These currents are used as variables in a linear programming (LP) problem formulation. The objective function, i.e. the change in losses, can be expressed by the injected currents, taking into account that all nodes are constrained by constant active powers except for the slack node. The change of power of the slack node is the change in losses, which is obtained by a two-step approximation. Each single optimal switching operation is obtained by an LP-like operation followed by a load-flow update. The interaction between LP and AC load-flow leads to a sequence of optimal switching operations whereby losses are reduced to a minimum subject to the given constraints. >

Combined Use of Linear Programming and Load Flow Techniques in Determining Optimal Switching Sequences

Abstract: By appropriately defining a model for the switching operation in a power system the problem of security enhancement is presented as one of optimization. In a first step linear programming with special features is introduced. Thereby optimal switching sequences can be determined. In a second phase load flow techniques are added to achieve a result which is comparable to an ordinary load flow. The proposed method uses the impedance matrix which is not modified by switching operations. Current sources are attached instead. The convergence of the load flow iterations is comparable to Stott's method.

Stabilizing switching

Abstract: A new idea of using switching to enhance the transient stability of a transmission network is outlined conceptually and illustrated by means of a simple example where the technical implications are given. A realistic system is used to show the benefit of stabilizing switching for a long distance transmission scheme. Depending on the type of fault, where the most severe is the three phase short circuit, an increase of the maximum transmissible power of about 10 percent can be achieved by the switching scheme. The additional benefits of this scheme include reduced fault currents and minimized effects of unsuccessful line reclosure. This scheme also provides a possibility for applying other control devices in stability control, e.g. surge arresters, current limiters and MOS controlled thyristors in the future. >

Features of a hybrid expert system for security enhancement

Abstract: Progress in combining analytical and rule-based programs for the purpose of power system security enhancement is reported. The emphasis is on the illustration of the details of the search process, the interaction between programs, and the role of heuristics. Security enhancement is an optimization problem. The concept for a hybrid expert system that performs a search through the space of the feasible operating states is developed. With the combination of a standard search algorithm with a production system a sophisticated search process is built up. This allows integrated analytical programs to provide the knowledge base with quantitative information about the network state and about the effects of control actions on the network state. An example is given of the application of the expert system. The results are presented, followed by a discussion of the effects of the variation of heuristic parameters on the search process. >

A survey of the optimal power flow literature

Abstract: 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. >

Optimal Transmission Switching

Abstract: 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.

Optimal Transmission Switching With Contingency Analysis

Abstract: 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

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

Abstract: 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.