K.A. Wirgau

Bio: K.A. Wirgau is an academic researcher from General Electric. The author has contributed to research in topics: Iterative design & AC power. The author has an hindex of 3, co-authored 3 publications receiving 328 citations.

Load modeling for power flow and transient stability computer studies

Abstract: 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. >

Multiple time-scale power system dynamic simulation

Abstract: A new program, EXSTAB (extended time-scale stability) has been developed for representing a wide variety of power system performance problems, from transient stability through long-term dynamics and voltage instability. The capability of the program includes multiple execution modes and automatic step size selection to address conflicting goals of accuracy and efficiency. The modeling includes a broad range of apparatus to provide the needed time-scale representation (four orders of magnitude). Models for automatic generation control, plant characteristics and control, voltage and reactive power control, static and dynamic loads, and protective relaying for apparatus and system connections are provided. Technologies were developed to perform analysis of voltage stability and prediction of peak power transfer to avoid voltage collapse. >

Transient stability expert system

Abstract: Expert system concepts are developed for use with power system stability studies, and proof of the concepts is provided in a prototype computer program. An analysis of the transient stability problem-solving process indicates that it is an iterative design procedure. Portions of this procedure are analogous to a closed-loop feedback control system. Expert system procedures are used to provide the user with guidance in conducting stability studies and with the formation of conclusions. >

Standard load models for power flow and dynamic performance simulation

Abstract: 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.

Flexible AC transmission systems (FACTS)

Abstract: 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...

Sensitivity of the loading margin to voltage collapse with respect to arbitrary parameters

Abstract: Power system loading margin is a fundamental measure of a system's proximity to voltage collapse. Linear and quadratic estimates to the variation of the loading margin with respect to any power system parameter or control are derived. Tests with a 118-bus system indicate that the estimates accurately predict the quantitative effect on the loading margin of altering the system loading, reactive power support, wheeling, load model parameters, line susceptance and generator dispatch. The accuracy of the estimates over a useful range and the ease of obtaining the linear estimate suggest that this method will be of practical value in avoiding power system voltage collapse.

Voltage instability: phenomena, countermeasures, and analysis methods

Abstract: A power system may be subject to (rotor) angle, frequency or voltage instability. Voltage instability takes on the form of a dramatic drop of transmission system voltages, which may lead to system disruption. During the past two decades it has become a major threat for the operation of many systems and, in the prevailing open access environment, it is a factor leading to limit power transfer. The objective of this paper is to describe voltage instability phenomena, to enumerate preventive and curative countermeasures, and to present in a unified and coherent way various computer analysis methods used or proposed.

Composite load modeling via measurement approach

Abstract: The accuracy of the load model has great effects on power system stability analysis and control. Based on our practice in China on modeling load from field measurements, this paper systematically develops a measurement-based composite load model. Principles guiding the load modeling practice are discussed based on detailed analysis on stochastic characteristics of the modeling procedure. The structure of the measurement-based composite load model is presented. A multicurve identification technique is described to derive parameters. The generalization capability of this built load model is also investigated in this paper. Two cases are studied to illustrate the accuracy of the developed load model on describing the load dynamic characteristics in the actual power system.