Publication: Diseño y validación del control digital de un inversor de potencia en ejes de referencia síncronos conectado a red
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2011-10
Defense date
2011-10-25
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Abstract
El aumento de los sistemas electrónicos de potencia conectados a la red eléctrica puede causar un impacto negativo en la misma, debido entre otras cosas a los armónicos de tensión que producen. Habitualmente, se emplean convertidores de potencia que consiguen eliminar los armónicos de alta frecuencia, logrando una tensión con baja distorsión armónica a su salida. No obstante, la tensión de salida de estos convertidores puede tener armónicos de baja frecuencia debido a diferencias entre los interruptores de los convertidores o los tiempos muertos necesarios para evitar cortocircuitos. Con el fin de eliminar estos armónicos, se pueden usar esquemas de control en lazo cerrado para disminuir aún más la distorsión de la tensión a la salida. En este proyecto se realiza un estudio del diseño de control de corriente en lazo cerrado, utilizando un sistema de referencia síncrono, en el que los ejes giran con la pulsación del sistema, obteniendo variables de control contínuas. De esta forma, la acción de control queda simplificada al ser todas las variables magnitudes continuas en régimen permanente. Aunque la implantación de estos controles resulta complicada, se pueden diseñar controles PI para anular el error en régimen permanente entre la referencia y la salida. El control de los convertidores de potencia se ha llevado a cabo tradicionalmente usando técnicas analógicas, no obstante, actualmente existe una tendencia a sustituir dichos controladores analógicos por otros digitales que precisan un previo muestreo de las señales mediante dispositivos de conversión analógico-digital. A lo largo de este Proyecto Final de Carrera se abordará el diseño y la validación del control digital de convertidores, realizando el desarrollo del circuito en un lenguaje de descripción hardware, de forma que se aúnen las ventajas de portabilidad y optimización del diseño en la aplicación propuesta. El proceso de validación del circuito de control digital implica una cosimulación analógico-digital que se apoya en dos de los simuladores más extendidos actualmente en el campo del diseño hardware. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
The increase of power electronic systems connected to grid can have a negative impact on it, due to the voltage harmonics produced. Typically, power converters are used in order to manage the cancelation of high-frequency harmonics, achieving a voltage with low harmonic distortion at the output of the converters. However, the output voltage of these inverters can have low frequency harmonics due to differences between switches or due to the dead time needed to avoid short-circuits. In order to cancel these harmonics, closed loop control schemes can be used, getting a decrease on the output voltage distortion. In this project, a closed loop current control design is done, by using a synchronous reference system where the axis rotates with the system, getting continuous control variables. Thus, the control action is simplified due to each variable in steady state takes continuous magnitude. Although the implantation of these controls is difficult, PI controls can be designed to override the error in steady state between the reference and the output. Control of power converters has been traditionally carried out using analog techniques, however, nowadays there is a tendency to replace them by digital ones, that requires a previous digital sampling of the signals by using analog-digital conversion devices. Along this Final Project will be developed the design and validation of digital control converters, and subsequently, the circuit will be developed in a hardware description language, to unify the advantages of portability and design optimization in the proposed application. The validation process of the digital control circuit implies an analog-digital cosimulation supported by two of more extended simulators on the hardware design frame.
The increase of power electronic systems connected to grid can have a negative impact on it, due to the voltage harmonics produced. Typically, power converters are used in order to manage the cancelation of high-frequency harmonics, achieving a voltage with low harmonic distortion at the output of the converters. However, the output voltage of these inverters can have low frequency harmonics due to differences between switches or due to the dead time needed to avoid short-circuits. In order to cancel these harmonics, closed loop control schemes can be used, getting a decrease on the output voltage distortion. In this project, a closed loop current control design is done, by using a synchronous reference system where the axis rotates with the system, getting continuous control variables. Thus, the control action is simplified due to each variable in steady state takes continuous magnitude. Although the implantation of these controls is difficult, PI controls can be designed to override the error in steady state between the reference and the output. Control of power converters has been traditionally carried out using analog techniques, however, nowadays there is a tendency to replace them by digital ones, that requires a previous digital sampling of the signals by using analog-digital conversion devices. Along this Final Project will be developed the design and validation of digital control converters, and subsequently, the circuit will be developed in a hardware description language, to unify the advantages of portability and design optimization in the proposed application. The validation process of the digital control circuit implies an analog-digital cosimulation supported by two of more extended simulators on the hardware design frame.
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Keywords
Inversores de potencia, Eliminación selectiva de armónicos, Control en lazo cerrado, Tensión de salida de un inversor, Conversión analógico-digital, Diseño digital, Lenguaje de descripción hardware, Validación mixta