Transient Stability Of Multi-machine System Research Articles

Lyapunov Stability Based Wide Area Control Systems for Excitation Boosters in Synchronous Generators

Excitation boosters (EBs) are aimed to improve fault ride through capability of synchronous generators equipped with bus fed static excitation systems by means of adding a supplementary voltage or current source to the rectifier. However, this paper shows that EBs governed by local on–off controls may result in adverse effects in case of remote faults from generators that may occur in multi-machine systems. To sort this problem out, a novel EB Wide Area Control System (WACS) that modulates the EB voltage using the generator speed deviation with respect to the speed of the center of inertia (COI) is proposed. The speed of the COI is obtained using a Wide Area Measurement System (WAMS), whereas the control laws are deduced from the Lyapunov stability theory. Results show that transient stability of multi-machine systems can be enhanced using EB WACS.

Enhancement of Power System Stability Using Self−Organized Neuro−Fuzzy Based HVDC Controls

This paper presents an affective neuro – fuzzy controller (NFC) to improve the transient stability of multi-machine system with HVDC link. Fuzzy rules are used as neurons in artificial neural network (ANN) model. Excellent learning capability of ANN and heuristic fuzzy rules and input/output membership functions of fuzzy logic technique are optimally tuned from training examples by back propagation algorithm (BPA). Considerable time required for fuzzy inference system to match rules is saved using NFC. To illustrate the performance of NFC, transient stability study is carried out on a multi machine system and results are compared with conventional controller as well as fuzzy logic controller.

Application of Lyapunov Theory and Fuzzy Logic to Control Shunt FACTS Devices for Enhancing Transient Stability in Multimachine System

This paper proposes the control strategy of the shunt Flexible AC Transmission System (FACTS) devices to improve transient stability in multimachine power system. The multimachine power system has high nonlinear response after severe disturbance. The concept of Lyapunov energy function is applied to derive nonlinear control strategy and it was found that the time derivative of line voltage is not only can apply to control the shunt FACTS devices in multimachine system but also is locally measurable signal. The fuzzy logic control is also applied to overcome the uncertainty of various disturbances in multimachine power system. This paper presents the method of investigating the effect of the shunt FACTS devices on transient stability improvement. The proposed control strategy and the method of simulation are tested on the new England power system. It was found that the shunt FACTS devices based on the proposed nonlinear control strategy can improve transient stability of multimachine power system.

Practical and Flexible Incorporation of AVR into Extended Equal Area Criterion

Automatic voltage regulator (AVR) models, additions to transient salicncy, are incorporated into extended equal area criterion (EEAC) for transient stability assessment of power systems in this paper. This is a further development of a previous paper where the EEAC has been successfully extended to constant Eq' models to consider transient saliency. The present paper further defines two equivalent machines with equivalent AVRs, which arc likely responsible for the possible separation. The transient stability of multimachine systems of any size, where machines may have various AVR parameters or no AVRs, can always be represented by only six first order differential equations. To these, instead of to multimachine state equations of high dimension, implicit integration is applied. With parametrizing AVR's effects on transient stability, renewed parameters of a one—machine infinite—bus system arc applied to the energy function with classical models, which contains only two items, i.e. kinetic and potential energy. Un-like in other literature, angle diffcrcncc between E' and Eq' and that between Vtand Eq' are neither neglected nor treated as constant in this study. Besides, transient saliency of individual machine, being usually excluded in the literature on direct methods with AVRs, is preserved here. Extensive test results on several practical power systems, concerning the accuracy and robustness with respect to various faults, transient saliency and AVR profiles, are reported in this paper. These fully confirm the significance of this extension and validate the feasibility of its practical applications.

A Direct Method for Transient Stability Analysis of Power Systems with Detailed Models

This paper presents a direct method for studying transient stability of multimachine systems with detailed models. The method uses a differential equation to define a general energy function. An algorithm is given for using the method with detailed models that contain fast dynamics.

Transient stability of multimachine systems with saturable exciters

Transient stability of multimachine systems with saturable exciters