Sergio Gomes

Modal analysis of industrial system harmonics using the s-domain approach

This paper describes the use of modal analysis of s-domain network models in the solution of harmonic distortion problems of industrial systems. Modal analysis involves the computation of the system poles, transfer function zeros as well as their sensitivities to changes in network parameters. A new modal sensitivity coefficient and a new modal observability index are introduced. These new coefficient and index are used to solve harmonic problems in a practical industrial system having multiple harmonic sources. The results obtained are believed to demonstrate the practical value of the proposed method.

Modal analysis of electromagnetic transients in ac networks having long transmission lines

This paper describes the use of modal analysis in electromagnetic transient studies of ac networks having long transmission lines. Modal analysis provides structural information on the system and nicely complements the results from conventional time and frequency response simulations. Results of energization studies on a small test system, having a long transmission line, are included. The simulations obtained from modal analysis were compared with those produced by a conventional electromagnetic transients program, showing good agreement. The modal analysis methodology may lead to more efficient computation in parametric studies, as shown in the paper.

s-Domain approach to reduce harmonic voltage distortions using sensitivity analysis

This paper describes a Newton-Raphson method that shifts a set of electrical network poles and transfer function zeros to specify positions in the complex plane. These shifts aim at the improvement of the system harmonic voltage performance. The method is based on the calculations of poles, zeros and their sensitivities to changes in system parameters. These calculations are carried out in the s-domain using the nodal admittance matrix Y(s) and its derivative with respect to the complex frequency s. A comparison is made between the proposed method and a recent one based on descriptor system approach. As is shown in the paper, the proposed method combines the advantages of the conventional admittance matrix method and modal analysis.

Sequential Computation of Transfer Function Dominant Poles of s-Domain System Models

This paper describes an algorithm for the sequential computation of transfer function dominant poles of s-domain system models. The algorithm is suited for the modal analysis of high-frequency dynamics of electrical networks having distributed parameter transmission lines. Results on a 39-bus electrical network containing 34 transmission lines are described to show the potential application of the proposed algorithm to infinite systems. The results clearly demonstrate the computational efficiency and numerical robustness of the algorithm, which is quite general and may be applied to s-domain system models that appear in other areas of engineering.

Some recent developments in small-signal stability and control

This paper describes recent work on power system small-signal stability, control applications and harmonic analysis carried out by CEPEL, Brazil. It describes developments carried out in CEPEL and related to the modal analysis of power system models.

Linear Techniques Applied to Small-Signal Electromechanical Stability, Model Order Reduction and Harmonic Studies

Abstract This paper describes recent work on small-signal stability, model order reduction and power system harmonic analysis carried out in CEPEL, the Brazilian Electrical Energy Research Center. CEPEL has developed, along the last three decades, a suite of power system analysis tools that are in current use by most of the Brazilian electrical utilities.

Integrating solution engines under a distributed processing environment: An alternative approach for static and dynamic security assessment of large scale power systems

This panel paper describes the initiative underway led by the Brazilian Electric Energy Research Center (CEPEL) in collaboration with Brazilian Universities aiming to the development of a static and dynamic security assessment (SDSA) tool for both operational planning and real time applications. The SDSA tool under development is based on the solution engines of two software tools largely used in the Brazilian power industry for load flow (Anarede) and dynamic simulation (Anatem).

Study on the influence of TCSC structure and control on SSR damping using an improved s-domain model

This paper investigates the influence of basic TCSC main circuit structure and control on subsynchronous torsional damping of a nearby turbine-generator. An improved s-domain model based on dynamic phasor approach was used to obtain the results presented in the paper. The study is conducted on the System-1 of the IEEE Second Benchmark Model. Detailed eigenvalue analyses are carried out in order to evaluate the effect of the proportion of TCSC to FSC, Boost Factor and size of TCSC reactor on subsynchronous damping. The influence of constant current controller and synchronization system (PLL) parameters is also investigated. Finally, a simple Subsynchronous Damping Controller (SSDC) is added to the TCSC main control in order to demonstrate that the SSR damping capability of TCSC may be enhanced by proper modulation of firing angle. The results obtained in the time domain simulations are validated through PSCAD/EMTDC simulations.

Sequential computation of transfer function dominant poles of s-domain system models

This paper describes an algorithm for the sequential computation of transfer function dominant poles of s-domain system models. The algorithm is suited for the modal analysis of high frequency dynamics of electrical networks having distributed parameter transmission lines. Results on a 39-bus electrical network containing 34 transmission lines are described to show the potential application of the proposed algorithm to infinite systems. The results clearly demonstrate the computational efficiency and numerical robustness of the algorithm, which is quite general and may be applied to s-domain system models that appear in other areas of engineering.

FLOCOS: Sistema Colaborativo à Construção de Objetos de Aprendizagem Funcionais

This work presents FLOCOS - Functional Learning Objects Collaborative System, a collaborative system for learning objects development that has it focus on a LO category not dealt with by other works: functional learning objects. This system was conceived based on 3C collaboration model and in this context its functionalities have been described.