Stability Of Multi-machine System Research Articles

Transient Stability Enhancement by Optimal Location and Tuning of STATCOM using Biogeography based Optimization Technique

In this paper, transient stability of a multi machine system is evaluated when the system is experienced a three phase fault and the stability of multi machine system is recovered via optimal placement and tuning of STATCOM. Here, the parameters of the STATCOM are tuned by Biogeography based optimization and the STATCOM is positioned optimally in the system. The performance of the tuned system is compared with various operational conditions like without STATCOM, with STATCOM (untuned) and with two STATCOM (untuned). The time domain simulations and the analysis of the multi machine system are done by PSAT (Power System Analysis Toolbox). When the multi machine system is subjected to a three phase fault, voltage stability of the system is collapsed. The multi machine system with STATCOM (tuned by Biogeography based optimization) regains the stability and gives better voltage profile than the system with STATCOM (untuned), with two STATCOM (untuned) and the system without STATCOM. The results are evaluated with the other operational conditions of the system and it proves that the system has the transient stability when the STATCOM (tuned by Biogeography based optimization) is applied.

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.

Tuning fuzzy power-system stabilizers in multi-machine systems by global optimization algorithms based on efficient domain partitions

In this paper, the problem of global tuning of fuzzy power-system stabilizers (FPSSs) present in a multi-machine power system in order to damp the power system oscillations is considered. In particular, it is formulated as a problem of global minimization of a multiextremal black-box function over a multidimensional hyperinterval. A global optimization technique, recently proposed, is used for solving the stated problem: the search hyperinterval is partitioned into smaller hyperintervals and the objective function is evaluated only at two vertices corresponding to the main diagonal of the generated hyperintervals, thus avoiding unnecessary ponderous simulations. Then, the performances of this technique are numerically compared with ones of a genetic algorithm (GA).

Global tuning of power-system stabilizers in multi-machine systems

Abstract This paper presents a global tuning procedure for conventional PSSs in a multi-machine power system using a non-linear optimization algorithm implemented in a simulation program. The main objective of this procedure is to simultaneously optimize pre-selected parameters of those PSSs having fixed parameters in coping with the complex non-linear natures of the power system. By minimizing a non-explicit target function in which the oscillatory rotor modes of the generators involved and swing characteristics between areas are included, overall power oscillations at transient conditions in the multi-machine system are improved. A four-machine power system is applied to demonstrate the efficiency and robustness of the presented tuning procedure. The results obtained from simulations validate the improvement in damping of overall power oscillations in the system. The simulation also shows that the optimized PSSs are robust in providing adequate damping for a range of conditions on the system.

Interactions between, and effectiveness of, power system stabilizers and FACTS device stabilizers in multimachine systems

In this paper it is shown that interactions occur between stabilizers in multimachine power systems, the stabilizers being power system stabilizers (PSSs), FACTS device stabilizers (FDSs) or both. The interactions, which are identified and quantified, may enhance or degrade the damping of certain modes of rotor oscillation. In particular, interactions between PSSs are found to adversely affect the damping of inter-area modes. The analysis of interactions also provides a practical means for quantifying and assessing simultaneously the relative effectiveness of both PSSs and FDS in damping the rotor modes of oscillation. This is achieved using a stabilizer damping contribution diagram. A theoretical basis is given for the analysis of interactions and the effectiveness of stabilizers; the practical significance and applications are illustrated using a case study on a 3-area, 400 state system having 28 generator groups and a number of FDSs. For systems of more than 600-700 states the modified Arnoldi method is used for eigenanalysis-based calculations.

99/00487 Tuning of power system stabilizers in multi-machine systems using ise technique

99/00487 Tuning of power system stabilizers in multi-machine systems using ise technique

Tuning of power system stabilizers in multi-machine systems using ise technique

The paper presents an approach based on integral of squared error (ISE) technique for tuning of the parameters of power system stabilizers (PSS) in a multi-machine power system. The PSS are tuned sequentially, depending on which machine needs stabilization most. However, later it has been establishes that if the tuning algorithm is iterated twice or more, no particular tuning sequence is necessary. Dynamic performance with PSS tuned by the proposed method is compared with a previously reported approach in which all the stabilizers are tuned simultaneously. The proposed approach provides satisfactory system dynamic performance and the method is computationally much simpler.

Stabilization of multimodal electromechanical oscillations by coordinated application of power system stabilizers

The author presents a hybrid methodology which utilizes modal sensitivity and frequency-domain analysis to coordinate power system stabilizers in multimachine systems. The approach permits robust stabilization of multimodal electromechanical oscillations by the minimal number of coordinated stabilizers. For the monitoring of nonlinear system response, a spectral technique is proposed which provides an insight into the time-frequency distribution of energy of electromechanical oscillations. This monitoring technique is used for the fast examination of the damping efficiency and robustness of coordinated stabilizers in the well-known ten-machine test system. >

Influence of Superconducting Generators on Steady-State Stability of Multi-Machine Power Systems

This paper deals mainly with how steady state-stability of interconnected power systems is influenced by introducing a superconducting alternator unit. A linearized model for a multi-machine system containing four generating units, one of whih is superconducting, is obtained. Results are presented which bring out the significant influences of a superconducting alternator on the steady-state stability of power systems. These indicate the directions in which improved performance may be achieved. A quantitative comparison between the influence of the superconducing generator and its conventional counterpart on the stability of multi-machine systems is also provided.

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.

Using Decoupled Characteristic in the Synthesis of Stabilizers in Multimachine Systems

Using Decoupled Characteristic in the Synthesis of Stabilizers in Multimachine Systems

Using Decoupled Characteristic in the Synthesis of Stabilizers in Multimachine Systems

A decoupled characteristic between the damping of a specific swing mode and the stabilizer gain of the corresponding machine in multimachine power systems is identified. Using this decoupled characteristic a power system stabilizer (PSS) synthesis approach which is based on the phase compensation concept is verified on a 9-machine system and the dynamic performance of this system is significantly improved. This method is proved to be effective, simple and it can provide useful guidances for the PSS field tuning.

Dynamic Stability and Excitation Control of Directly-Coupled Multimachine System

This paper introduces an efficient and accurate stabilization method for the design of linear optimal controllers which can stabilize a directly- coupled multimachine system via excitation control. A systematic modeling method is first developed to formulate a directly-coupled multimachine system into state space form with directly-measurable state variables. With this form, the stabilization of the multimachine system is converted into a linear-quadratic- Gaussian (LQG) problem. Next, a model reduction algorithm which can deal with any system with real and/or complex poles is developed. Incorporating this algorithm with Solheim's pole-assignment technique as an example provides a new efficient and numerically accurate stabilization method. With this method, a feedback controller able to improve the dynamic stability of a directly-coupled multimachine system under wide-range operation via excitation control is developed. The design is verified by simulated results. The use of directly-measurable state variables also renders a physically implementable feedback controller design.

Coordinated Application of Stabilizers in Multimachine Power Systems

This paper addresses the problem of the most effective selection of generating units to be equipped with excitation system stabilizers in multimachine systems which exhibit dynamic instability and poor damping of several inter-machine modes of oscillation. Practical means have been developed using eigenvalue analysis techniques to guide the selection process. The linear state space matrix is derived directly from perturbation of the states of a large scale power system dynamic simulation and a subset of this matrix is used to yield the sensitivity of damping ratios of eigenvalues to stabilization measures in individual machines.

Transient stability of multimachine systems with saturable exciters

Transient stability of multimachine systems with saturable exciters