Plantas de generación solar operando en paralelo para un sistema en isla.
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Date
2024
Authors
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Publisher
Universidad de Concepción
Abstract
El trabajo tiene como objetivo principal la sincronización en varios parámetros de los convertidores DC/AC alimentados cada uno por un arreglo de paneles fotovoltaicos, diseñados para una potencia en específico y no equitativas entre sí. El principal problema es la ausencia de una red como tal que conecte a las plantas fotovoltaicas, pues se trata de un sistema en isla. Consecuentemente, la ausencia de esta red dificulta la sincronización en frecuencia, voltaje y despacho de potencia.
Para lo anterior, se obtuvieron en primer lugar las ecuaciones diferenciales que modelan el circuito de generación de potencia, en donde se obtuvo valores de potencia activa y reactiva inyectada por cada planta fotovoltaica. La suma directa de ambas potencias inyectadas por las plantas fotovoltaicas es 1 [p.u.], lo que muestra que el modelo matemático responde de manera correcta a valores de potencia requeridos por la carga en común. Luego, obtenida las entradas para el punto de operación requerido, se utilizó el software PLECS para validar el modelo encontrado, en donde se obtuvo una respuesta del circuito como la esperada. Posteriormente y utilizando las ecuaciones circuitales encontradas, se propusieron lazos de control para cada planta fotovoltaica, buscando alcanzar los objetivos iniciales. En estos lazos de control, la propuesta se enfoca en mantener mediante una planta fotovoltaica denominada “maestra” un voltaje constante en la red. Es decir, esta planta regula el voltaje y la frecuencia de la red para que se mantenga constante ante impactos tanto de entrada como de cargas y de nuevas plantas fotovoltaicas en paralelo. A su vez, las plantas fotovoltaicas que se conecten en paralelo se deben sincronizar a esta, lo cual se realizó mediante el diseño de un lazo de control de corriente. Así, los demás convertidores estarían operando como fuentes de corriente, de forma de no provocar diferencias instantáneas de voltaje entre los convertidores en paralelo, pues resultaría en presencia de corrientes circulantes que afectarían la forma de onda y la calidad de la potencia en la carga.
Utilizando esta estrategia de control, se obtiene corrientes casi sinusoidales en la carga, además de una rápida sincronización de la planta fotovoltaica esclava a la red en isla en voltaje y frecuencia, lo que conlleva a una entrega de potencia limpia de ambas plantas fotovoltaicas. Además, se obtienen resultados de simulación que muestran que la planta fotovoltaica maestra amortigua de manera correcta la entrada de plantas fotovoltaicas en paralelo y entrada/salida de cargas AC.
The main objective of the work is the synchronization of various parameters of the DC/AC converters each fed by an array of photovoltaic panels, designed for a specific power and not equal to each other. The main problem is the absence of a network as such that connects the photovoltaic plants, since it is an island system. Consequently, the absence of this network makes synchronization in frequency, voltage and power dispatch difficult. For the above, the differential equations that model the power generation circuit were first obtained, where values of active and reactive power injected by each photovoltaic plant were obtained. The direct sum of both powers injected by the photovoltaic plants is 1 [p.u.], which shows that the mathematical model responds correctly to power values required by the common load. Then, having obtained the inputs for the required operating point, the PLECS software was used to validate the model found, where a circuit response as expected was obtained. Subsequently and using the circuit equations found, control loops were proposed for each photovoltaic plant, seeking to achieve the initial objectives. In these control loops, the proposal focuses on maintaining a constant voltage in the network through a photovoltaic plant called “master”. That is, this plant regulates the voltage and frequency of the network so that it remains constant in the face of impacts from both input and loads and from new photovoltaic plants in parallel. In turn, the photovoltaic plants that are connected in parallel must be synchronized to it, which was done through the design of a current control loop. Thus, the other converters would be operating as current sources, so as not to cause instantaneous voltage differences between the converters in parallel, as this would result in the presence of circulating currents that would affect the waveform and the quality of the power in the load. Using this control strategy, almost sinusoidal currents are obtained in the load, in addition to rapid synchronization of the slave photovoltaic plant to the island grid in voltage and frequency, which leads to clean power delivery from both photovoltaic plants. In addition, simulation results are obtained that show that the master photovoltaic plant correctly buffers the input of parallel photovoltaic plants and input/output of AC loads.
The main objective of the work is the synchronization of various parameters of the DC/AC converters each fed by an array of photovoltaic panels, designed for a specific power and not equal to each other. The main problem is the absence of a network as such that connects the photovoltaic plants, since it is an island system. Consequently, the absence of this network makes synchronization in frequency, voltage and power dispatch difficult. For the above, the differential equations that model the power generation circuit were first obtained, where values of active and reactive power injected by each photovoltaic plant were obtained. The direct sum of both powers injected by the photovoltaic plants is 1 [p.u.], which shows that the mathematical model responds correctly to power values required by the common load. Then, having obtained the inputs for the required operating point, the PLECS software was used to validate the model found, where a circuit response as expected was obtained. Subsequently and using the circuit equations found, control loops were proposed for each photovoltaic plant, seeking to achieve the initial objectives. In these control loops, the proposal focuses on maintaining a constant voltage in the network through a photovoltaic plant called “master”. That is, this plant regulates the voltage and frequency of the network so that it remains constant in the face of impacts from both input and loads and from new photovoltaic plants in parallel. In turn, the photovoltaic plants that are connected in parallel must be synchronized to it, which was done through the design of a current control loop. Thus, the other converters would be operating as current sources, so as not to cause instantaneous voltage differences between the converters in parallel, as this would result in the presence of circulating currents that would affect the waveform and the quality of the power in the load. Using this control strategy, almost sinusoidal currents are obtained in the load, in addition to rapid synchronization of the slave photovoltaic plant to the island grid in voltage and frequency, which leads to clean power delivery from both photovoltaic plants. In addition, simulation results are obtained that show that the master photovoltaic plant correctly buffers the input of parallel photovoltaic plants and input/output of AC loads.
Description
Tesis presentada para optar al Título de Ingeniero Civil Electrónico
Keywords
Paneles fotovoltaicos, Convertidores de corriente eléctrica, Energía solar