The paper presents a review of literature on optimal power flow tracing progress in this area over from 1962-93. Part I deals with the application of nonlinear and quadratic programming.

A review of selected optimal power flow literature to 1993. I. Nonlinear and quadratic programming approaches

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

A survey is presented of papers and reports that address various aspects of economic dispatch. The time period considered is 1977-88. Four related areas of economic dispatch are identified and papers published in the general areas of economic dispatch are classified into these. These areas are: optimal power flow, economic dispatch in relation to AGC, dynamic dispatch, and economic dispatch with nonconventional generation sources. >

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A review of recent advances in economic dispatch

The authors recommend standard load models for power flow and dynamic simulation programs. The goal of this paper is to promote better load modeling and advanced load modeling, and to facilitate data exchange among users of various production-grade simulation programs. Flexibility of modeling is an important consideration. For transient stability, longer-term dynamics, and small-disturbance stability programs, the authors recommend the structure of multiple load types connected to a load bus. Load types are static including discharge lighting, induction motors, synchronous motors, and transformer saturation. For each load type, multiple models may be connected to the bus. For longer-term dynamics programs, a model for LTC transformers is also recommended.

Standard load models for power flow and dynamic performance simulation

The paper reviews literature which addresses the application of Flexible AC Transmission System (FACTS) concepts to the improvement of Power System utilisation and performance. It summarises literature on using high speed thyristor based control of HVAC power system elements to enhance the power carrying capacity of existing transmission circuits without compromising reliability. It describes a study system representative of existing power systems that has been developed to evaluate the economic and technical issues of loading transmission lines to their thermal limits. Considered are two scenarios, a multi-line corridor and a long radial interconnection, where the issues addressed are transient and dynamic stability, power flow control, reactive support and voltage stability. A benchmark system is developed to validate performance of die more simple devices. It is concluded that FACTS devices have the potential to significantly increase system stability margins thereby increasing loading capabil...

Flexible AC transmission systems (FACTS)

A novel method is presented for preparing load models for power flow and stability studies. The LOADSYN load model synthesis software package transforms data on load class mix, composition, and characteristics into the form required for commonly used flow and transient stability simulation programs. Typical default data have been developed for load composition and characteristics. The load-modeling techniques used in this software and results of initial testing are described. Significant improvements in simulation accuracy are demonstrated. >

Load modeling for power flow and transient stability computer studies

This paper presents a practical and efficient method to incorporate energy analysis into conventional power system time domain transient stability simulation for producing a first swing stability index. The proposed method is a variation of the potential energy boundary source approach, utilizing a numerical transient energy function and a pseudo-fault-on trajectory starting from the dominant potential energy peak point of the postfault system trajectory. The transient stability index not only provides additional insight into the stability studies, but also has the potential of speeding up the stability limit derivation process by reducing the number of program runs. >

Transient stability index from conventional time domain simulation

This paper presents applications of an efficient computerized technique for power system dynamic system security assessment using the transient energy function (TEF) method. The technique exploits the sensitivities of the unnormalized transient energy margin with respect to operating indices and critical interface flows in order to arrive at the stability limits for various system outage states and operating conditions, that would be required for on-line application. The paper describes the sensitivity technique and demonstrates a practical application to the dynamic security problem in one portion of the Ontario Hydro system including results of the validation and accuracy tests of the technique.

Dynamic Security Assessment Utilizing the Transient Energy Function Method

This paper reports the results of a detailed study of on-line voltage/var control performed on the Ontario Hydro system. The first part of the study is an assessment of active transmission loss savings obtained by optimizing generator voltages and transformer taps with an Optimal Power Flow program using data from a state estimator. In the second part of the study, the question is addressed of how frequently the generator voltages and transformer tape should be optimized in order to achieve a large percentage of the loss savings indentified in the first part. The study showed that the reduction in active losses is sufficient to justify further effort toward implementing voltage control. The results of the second part showed that for the load curve studied, most of the savings could be achieved with voltage control cycle times of about one hour. A new quadratic programming-based optimal power flow algorithm is also presented which exhibits execution times suitable for real-time applications. Sample execution times are given for various systems which confirm that exact optimal power flow solutions can be obtained in a fraction of the control cycle times suggested in the second part of the study.

Assessment of Real-Time Optimal Voltage Control

This paper deals with the demonstration of the Transient Energy Function (TEF) method in large, realistic power networks. Documented examples of application in power system operation and associated software development for systems up to 228-generators and 1644-buses are given. An overview of the analytical and computational problems encountered in the large scale application of the TEF method is presented. Approaches used to overcome the problems are provided, and the relevant improvements and modifications to the TEF software are discussed.

M. A. El-Kady

Papers

Load modeling for power flow and transient stability computer studies

Transient stability index from conventional time domain simulation

Dynamic Security Assessment Utilizing the Transient Energy Function Method

Assessment of Real-Time Optimal Voltage Control

Direct Transient Stability Analysis Using Energy Functions Application to Large Power Networks