Rosa E. Correa

Voltage compensation for common disturbances at the distribution level

The first dynamic voltage restorer (DVR) was introduced in 1994 as a result of collaborative effort between Westinghouse (presently Siemens), EPRI, and Duke Power. The dynamic voltage restorers application has been already demonstrated and is extensively reported, much of the research on DVRs has focused on dc link-based voltage source converters (VSC). These converters have evolved rapidly in the field of industrial AC motor drives. Thus, the importance of the DVR is well recognized. This paper deals with applications related to voltage compensation in order to satisfy the future smart grids standards.

Natural strategy for dynamic equivalencing

In this paper a power systems reduced order model is presented which is evaluated by simple calculations through data taken out from the steady state analysis. This type of equivalent is useful, especially where preserving a portion of an electrical region is relevant. The external network is reduced to a few boundary buses where equivalent generators are located. From the internal network point of view, preserving voltages at buses connected to the boundary ones help to improve the precision of the electromechanical transient. Results on a power system of the open literature are exhibited under different operating conditions, showing approximate response between the full and the reduced system.

Operación Descentralizada en Grandes Sistemas de Potencia usando Algoritmos Genéticos

Este articulo propone una metodologia para la coordinacion y operacion de grandes sistemas de potencia de forma descentralizada, simplificando la optimizacion y reduciendo los tiempos de computo. La busqueda optima del voltaje de los generadores, cambiador de tomas, y compensacion, se logra utilizando una tecnica evolutiva, planteandola como un problema de optimizacion multiobjetivo. Se considera la descomposicion tanto de la red como el problema de optimizacion y se valida con dos casos de prueba (39 y 190 nodos). Los resultados muestran una operacion optima global preservando la estabilidad de voltaje y la gestion de intercambios entre areas, con minima informacion operativa, simplicidad en los equivalentes y reduccion en tiempos de computo. Los resultados son similares a los obtenidos mediante una estrategia de optimizacion centralizada.

Fuzzy Inference Systems Applied to the Analysis of Vibrations in Electrical Machines

Within industry, the concept of maintenance can be handled in different ways. It can be done periodically at predefined times, according to the type of machine, and according to the manufacturers’ recommendations. In this case, it is referred to as scheduled preventive maintenance. Maintenance done when there is faulty equipment is commonly called corrective maintenance. Employing electrical machines’ operating signals may be useful for diagnosis purposes.

A comparison of Kalman-based schemes for localization and tracking in sensor systems

The challenge of target tracking is one of the most important applications of WSNs (Wireless Sensor Networks). Traditionally, Kalman filter and its derivatives are some of the most popular algorithms for solving the signal tracking problem. In a WSNs tracking application, the target motion and state update dynamics might be modelled by linear or non-linear structures depending on the specific scenario. This paper compares extended Kalman Filters with the P, PV and PVA dynamics models for object tracking in sensor networks.

Statistical estimation of power system vulnerability

This proposal exploits the main aspects of design and analysis of experiments. The goal is to find an early vulnerability estimation, which allows that operators make decisions before a collapse occurs. The method is based on variables that can be measured on-line using PMU technologies, specifically bus voltages. Voltage Collapse Proximity Index (VCPI) is one of the most popular indices. Vulnerability indicator, defined by a relation between bus voltages and admittance values is calculated using historical and simulated data. A multi-variable statistical model is built, which is validated and tested to assess its robustness. The proposed method is tested on the IEEE 14-bus test system. Results show effective performance for power system vulnerability estimation.

A new 84-pulse VSC configuration using multi-level DC voltage reinjection for especial applications

This paper analyzes the structure of an 84-pulse voltage source converter (VSC), assembled by combining one twelve-pulse VSC, in conjunction with an asymmetric singlephase seven-level converter plus an injection transformer. With this arrangement, the VSC outputs total harmonic distortion in voltages is reduced, allowing it to be used in especial applications or as the basement of flexible A.C. transmission systems (FACTS) devices. The proposed strategy allows savings in the number of employed switches. Simulations and experimental results are provided to show the proposal appropriateness.

Inestabilidad de Voltaje en Sistemas de Potencia

El objetivo de este trabajo es aprovechar la naturaleza periodica de los voltajes y corrientes y considerar cargas desbalanceadas para realizar un mejor analisis dinamico de voltaje en sistemas de potencia. El analisis dinamico de la estabilidad de voltaje se ha fundamentado en modelos reducidos que utilizan la transformacion de Park. El resultado es un modelo bifasico del generador sincronico en el que se supone carga balanceada y senales de naturaleza no periodica. En este trabajo se selecciono un modelo periodico de un generador sincronico. Este modelo permite experimentar con cargas mas naturales como resistencias, inductores e inductores conmutados que representan los controladores de los motores modernos. Con apoyo de las curvas V-P, se detecto resonancia en presencia de cargas conmutadas y se mostro los efectos adversos en el sistema de potencia cuando se tienen cargas desbalanceadas.