Conmutación simétrica de un rectificador trifásico versus convertidor AC/AC para la mejora del factor de potencia en microcentrales hidroeléctricas

En el presente artículo se realiza el análisis de un rectificador trifásico tipo puente con un interruptor en serie con la carga conmutado con ángulo simétrico. Para dicho análisis se trabajan con una serie de índices como son la corriente eficaz, las potencias activa, reactiva, aparente y de distorsión, y el factor de potencia. El objetivo es aplicar este rectificador conmutado con ángulo simétrico para la mejora del factor de potencia en microcentrales hidroeléctricas que operan en régimen autónomo, y en las que se regulan la frecuencia variando la potencia disipadas en cargas balastros mediante convertidores de corriente alterna/corriente alterna (AC-AC). Las expresiones matemáticas de los índices previos para el convertidor AC-AC son resumidas. Sin embargo, un caso de estudio es desarrollado y se demuestra la ventaja del circuito rectificador en cuanto al factor de potencia del sistema eléctrico.Peer ReviewedPostprint (published version

Symmetrical angle switched single-phase and three-phase rectifiers: application to micro hydro power plants

Micro-size hydro power plants are commonly used at remote areas to supply islanded AC microgrids. A typical way to control grid frequency is to manipulate active power dissipated in ballast loads by AC/AC converters. However, these asymmetrically switched thyristor controlled converters consume reactive power degrading the power factor at the generator output. In this paper the operation of a symmetric angle switched, bridged three-phase rectifier and three single-phase rectifiers connected in series with ballast load, are studied to improve the power factor of the system. As a consequence, the objective is to evaluated the use of the three and single-phase rectifiers switched with symmetrical angle to improve the power factor, by reactive power compensation, at the output terminal of the electric generator of µHPPs that use ballast load to regulate frequency.Postprint (published version

Conmutación simétrica del rectificador aplicado a microcentrales hidroeléctricas

En el presente trabajo se analizó un rectificador trifásico tipo puente con un interruptor en serie con la carga conmutado con ángulo simétrico, con respecto a los índices corriente eficaz, potencia activa, reactiva, aparente, de distorsión y factor de potencia. El objetivo es aplicar este rectificador conmutado con ángulo simétrico para el mejoramiento del factor de potencia en microcentrales hidroeléctricas que operan en régimen autónomo (aisladas del sistema eléctrico), en las que se regulan la frecuencia variando la potencia disipada en cargas lastres mediante convertidores de corriente alterna en corriente alterna (CA-CA). Las expresiones de los índices anteriores del convertidor de CA-CA son resumidos. Se calculó un ejemplo en el cual es desarrollado un caso de estudio donde ambos convertidores son comparados para un punto de operación, luego mediante los resultados de simulación se obtiene que con el circuito rectificador trifásico conmutando el interruptor con ángulo simétrico, se logra una mejora del factor de potencia a la salida del generador en el 94,5% del intervalo de variación de la potencia activa consumida por los usuarios, demostrando la ventaja del circuito rectificador con respecto al factor de potencia del sistema eléctrico.Postprint (published version

Symmetrical angle switched single-phase and three-phase rectifiers: application to micro hydro power plants

Micro-size hydro power plants are commonly used at remote areas to supply islanded AC microgrids. A typical way to control grid frequency is to manipulate active power dissipated in ballast loads by AC/AC converters. However, conventional asymmetrically switched thyristor controlled converters consume reactive power degrading the power factor at the generator output and transmission efficiency. In this paper the operation of a symmetric angle switched, bridged three-phase rectifier and three single-phase rectifiers connected in series with ballast load, are studied to improve the power factor of the system. The objective is to evaluate the characteristics of these two configurations to improve the power factor of the system.Peer ReviewedPostprint (published version

Evaluation of the symmetrically-switched converter structures on the frequency regulation of standalone micro hydro power plants

Micro hydro power plants (¿HPP) are typically used to supply electric energy to microgrids outside the national power grids taking care of the frequency control of the isolated system. A conventional way to maintain the load balance in the system is to use thyristor switched AC-AC converters controlled dump loads. A disadvantage of the AC-AC converters is their reactive power consumption decreasing the power factor at the generator output. To avoid this problem the authors have earlier proposed two converter topologies utilizing symmetrical switching scheme resulting to zero reactive power consumption. The objective of this paper is to evaluate the frequency regulation loop performance of the dump load controlled single generator system by using the symmetrically switched converter structures. Evaluation is carried out by analyzing the performances of different converter structures in a simulator representing the operation of a Cuban ¿HPP “Los Gallegos”. The results showed that the frequency regulation loop performance using each proposed converter structure satisfied the Cuban standard of frequency regulation, but with the symmetrically switched structures reactive power consumption was reduced resulting to reduced losses and improved effective current delivery capacity of the generator.Postprint (published version

Evaluation of the symmetrically switched converter structures on the frequency regulation of standalone micro hydro power plants

Micro hydro power plants (µHPP) are typically used to supply electric energy to microgrids outside the national power grids taking care of the frequency control of the isolated system. A conventional way to maintain the load balance in the system is to use thyristor switched AC-AC converters controlled dump loads. A disadvantage of the AC-AC converters is their reactive power consumption decreasing the power factor at the generator output. To avoid this problem the authors have earlier proposed two converter topologies utilizing symmetrical switching scheme resulting to zero reactive power consumption. The objective of this paper is to evaluate the frequency regulation loop performance of the dump load controlled single generator system by using the symmetrically switched converter structures. Evaluation is carried out by analyzing the performances of different converter structures in a simulator representing the operation of a Cuban µHPP “Los Gallegos”. The results showed that the frequency regulation loop performance using each proposed converter structure satisfied the Cuban standard of frequency regulation, but with the symmetrically switched structures reactive power consumption was reduced resulting to reduced losses and improved effective current delivery capacity of the generator.Postprint (published version

Comparison of Single-Phase Rectifier with Symmetrical Switching and AC-AC Converter for the Power Factor Improvement in Hydroelectric Micro-Plants

[EN] In a previous paper the authors compared the AC-AC converters, useful for the frequency regulation in hydroelectric microplants varying the power dissipated in ballasts loads, with the new proposal consisting in a bridge three-phase rectifier using diodes with a serial switch with the load that is switched with symmetric angle. The paper showed that the aforementioned rectifier accomplishes to improve the power factor at the generator output, except for low power consumed by users, near to its minimal value. A way to solve this problem consists in to use three bridge single-phase rectifier using diodes with a serial switch with the load that is switched with symmetric angle. As a consequence, the objective of this article is to carry out a comparison between the aforementioned single-phase rectifier and the AC-AC converter, regarding the power factor at the output of the electric generator of hydroelectric micro-plants that regulate frequency by means of the ballast-load method.[ES] En un trabajo anterior se compararon los convertidores de corriente alterna/corriente alterna (AC-AC), típicamente utilizados para la regulación de frecuencia en microcentrales hidroeléctricas variando la potencia disipada en cargas lastres, con un rectificador trifásico a diodos tipo puente con un interruptor, en serie con la carga, conmutado con ángulo simétrico. En el mismo, se demostró que, con dicho rectificador, se logra mejorar el factor de potencia a la salida del generador eléctrico, excepto para potencias consumidas por los usuarios cercanas a su valor mínimo. Una vía para solucionar este problema consiste en emplear una terna de rectificadores monofásicos a diodos tipo puente con un interruptor, en serie con la carga, conmutado con ángulo simétrico. Así, el objetivo del presente artículo es comparar al rectificador monofásico mencionado y el convertidor de AC-AC, esquema empleado actualmente, respecto a parámetros de interés como es el factor de potencia a la salida del generador eléctrico de las microcentrales hidroeléctricas que regulan frecuencia por el método de carga lastre.Bory Prevez, H.; Martínez García, H.; Vázquez Seisdedos, L. (2018). Comparación entre Rectificador Monofásico con Conmutación Simétrica y Convertidor AC/AC para la Mejora del Factor de Potencia en Microcentrales Hidroeléctricas. Revista Iberoamericana de Automática e Informática. 16(1):79-88. doi:10.4995/riai.2018.9313SWORD798816

The use of symmetrical angle switched single- & 3-phase rectifiers in micro hydro power plants

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Micro-size hydro power plants (µHPPs) are commonly used at remote areas to supply islanded AC microgrids. A typical way to control grid frequency is to manipulate active power dissipated in ballast loads by AC/AC converters. However, these asymmetrically switched thyristor controlled converters consume reactive power degrading the power factor at the generator output. In this paper the operation of a symmetric angle switched, bridged three-phase rectifier and three single-phase rectifiers connected in series with ballast load, are studied to improve the power factor of the system. As a consequence, the objective is to evaluated the use of the three and single-phase rectifiers switched with symmetrical angle to improve the power factor, by reactive power compensation, at the output terminal of the electric generator of µHPPs that use ballast load to regulate frequency.Postprint (published version