Existing methods for transient stability equivalents all lack a means of drawing a consistent boundary between the equivalized area and the area represented in detail. In most methods, it is assumed that the generators equivalized are coherent. However, no simple method to identify them has been offered, which does not require a transient stability study of the entire system. A method using distance measures to draw boundaries and pattern recognition concepts to identify coherency is presented. Computation required is minimal. The method is incorporated in a computer program which is a useful tool for transient stability studies in power system planning.

Distance Measures and Coherency Recognition for Transient Stability Equivalents

This paper describes the development of dynamic power system equivalents for use in stability studies of interconnected systems. The problem of electromechanical equivalencing is formulated, and a method of constructing electromechanical equivalents is described. The performance of these equivalents has been evaluated by a series of computational tests. Theoretical material pertaining to electromechanical equivalencing is presented in a companion paper.

Electromechanical Equivalent for Use in Power System Stability Studies

This paper describes verification of five conjectures related to power system controlled separation. It attempts to verify that the location of uncontrolled separation (loss of synchronism or out-of-step operation) is independent of the location and severity (short-circuit duty or duration) of the initial faults, that the location depends on the prevailing network configuration and load level, and that it takes place one operation at a time (cascades). Verification of these conjectures would allow controlled separation during a disturbance in real-time, using the present communication and protection systems, and results in a minimal load and generation imbalance. Two actual power systems were used, a 50-bus system to establish the procedure for controlled separation and a 640-bus interconnection to apply the procedure. Data representing static and dynamic behavior of the two power systems were obtained from the operating utilities, and the many required simulations were conducted using EPRI Power System Analysis Package (including IPFLOW and ETMSP programs)

On Power System Controlled Separation

Dynamic equivalents (DE) can reduce the computing effort and emphasise the main characters of a power system. A DE model has been developed in which identifiability is studied. Identifiability has not only a theoretical meaning, but also practical value. It is shown that some parameters of the model are unidentifiable when using only the steady-state data before disturbance and during disturbance, but identifiable when using only the steady-state data before disturbance and during disturbance, but identifiable when using only the data before and during disturbance, but identifiable when utilising the data after disturbance.

Dynamic equivalents of power systems with online measurements. Part 1: Theory

This paper is concerned with an investigation of a methodology using intelligent learning techniques based on system measurements to construct power system load models alongside with distribution network reduction. A comprehensive load model is proposed to represent the loads in an area of a power system. A population diversity-based genetic algorithm (GA) is developed to obtain the structure and parameters of the load model. Simulation results on a five-bus power system and an IEEE 30-bus power system are given to show the potential of this new methodology of power system modeling.

Power system load modeling by learning based on system measurements

This paper describes a method for determining a simplified equivalent mathematical representation of portions of a power system for transient stability analysis The method leads to equations that do not correspond directly to a system composed of normal power system components Conditions under which it is possible to obtain such an equivalent are given, and the results of applying the method to the 118-bus IEEE test system are reported

Mahmood M. Adibi

Papers

Power System Dynamic Equivalents