A energia solar fotovoltaica é a forma de produção de eletricidade que mais cresce no mundo. A potência instalada mundial, até o ano de 2010, era de cerca de 40 GWP e a previsão é de que, somente em 2011, este cifra seja aumentada em mais 24 GWP. O inversor é o elemento central dos sistemas fotovoltaicos. Além de executar a conversão da energia elétrica em corrente contínua para corrente alternada, ele também é responsável pelo gerenciamento da energia entregue à rede e pelo seguimento do ponto de máxima potência. O seguimento do ponto de máxima potência (MPPT) é um processo de controle no qual o inversor procura manter o gerador fotovoltaico operando em uma região da sua curva característica na qual o produto corrente × tensão tenha o seu valor máximo, de forma a otimizar a extração de potência do gerador fotovoltaico. A eficiência de MPPT é um número que indica o grau de precisão, tanto em termos de rapidez como de magnitude, com que o seguidor do ponto de máxima potência atinge o seu objetivo. Assim podem ser definidas duas eficiências de MPPT: a eficiência estática, associada a situações em que a irradiância solar permanece constante durante o intervalo considerado, e a eficiência dinâmica de MPPT, que considera os momentos de variação na intensidade da irradiância, resultantes, por exemplo, da passagem de nuvens. As eficiências de MPPT (especialmente a dinâmica) são de difícil determinação, porém a tarefa fica muito facilitada com a utilização de um simulador de arranjos fotovoltaicos. A norma européia EN 50530:2010 Overall Efficiency of Photovoltaic Inverters propôs uma metodologia para a determinação da eficiência dinâmica de MPPT utilizando perfis variáveis de irradiância a serem programados no simulador de arranjos fotovoltaicos. O objetivo central da tese é fazer uma análise experimental da eficiência dinâmica do seguimento de máxima potência de inversores conectados à rede através da comparação dos resultados de eficiência obtidos seguindo a metodologia definida na norma citada com resultados obtidos a partir de medições em tempo real ao longo de um dia, verificando a adequação da norma às situações de campo. Para a obtenção dos dados de entrada do simulador foram medidas, por diversos dias, a irradiância e temperatura de uma célula de referência. Os inversores foram conectados à saída do simulador de arranjos fotovoltaicos e foram reproduzidas as condições de irradiância e temperatura de três dias selecionados em função do grau de nebulosidade, com comportamento dinâmico semelhante aos perfis de irradiância da norma. Os resultados foram, na maioria dos casos, discordantes. Uma análise dos resultados parciais de eficiência dinâmica indicou como causa desta discrepância a dependência que a eficiência dinâmica de MPPT tem com a taxa de variação da irradiância. Conclui-se que, embora as seqüências de irradiância propostas pela norma constituam uma eficiente ferramenta para o diagnóstico de eventuais deficiências no comportamento do seguidor de máxima potência de inversores, a média dos valores de eficiência de MPPT calculados a partir delas não pode, em princípio, ser considerada como representativa de valores diários. / Photovoltaic solar energy is the fastest growing electricity source in the world. The worldwide capacity until 2010 was about 40 GWP and, by the end of 2011, this figure will be increased by another 24 GWP. The inverter is the pivotal element of PV systems. In addition to performing the conversion of electrical energy from direct current to alternating current, the inverter is also responsible for the management of the energy delivered to the grid and for performing the maximum power point tracking. The maximum power point tracking (MPPT) is a control process by which the inverter tries to keep the PV generator operating in a region of its characteristic curve where the product current × voltage reaches its maximum value. The MPPT efficiency is a figure that indicates the degree of precision, both in terms of speed and magnitude, that the MPPT reaches its goal. Thus, two MPPT efficiencies can be defined: the static efficiency, associated to situations in which the solar irradiance does not vary during the considered interval, and also the dynamic MPPT efficiency, which considers the variation of the irradiance intensity as a result, for example, of the passage of clouds. MPPT efficiencies (especially the dynamic) are hard to determine, but the task becomes much easier with the use of a photovoltaic array simulator. The European standard EN 50530:2010 Overall Efficiency of Photovoltaic Inverters proposes a methodology for determining the dynamic efficiency of MPPT using variable irradiance profiles to be programmed into the photovoltaic array simulator. The main objective of this thesis is to make an experimental analysis of the dynamic MPPT efficiency of grid connected inverters by comparing the efficiency results obtained by following the methodology defined in the referred standard with results obtained from real time measurements in the course of a day, checking the adequacy of the standard when applied to field situations. In order to obtain the input data for the simulator, the irradiance and temperature of a reference cell were measured for several days. The inverters were connected to the output of the array simulator, which reproduced the conditions of irradiance and temperature for three days selected according to the degree of cloudiness, having a dynamic behavior similar to the standard irradiance profiles. The results, in most cases, disagree. An analysis of partial results of dynamic efficiency indicated the dependence of the dynamic MPPT efficiency to the rate of irradiance change as the cause of this discrepancy. As a conclusion, it can be stated that, although the sequences of irradiance proposed by the standard are an efficient tool for the diagnosis of deficiencies in the behavior of the MPP tracker, the average efficiency of MPPT calculated from the sequences cannot, in principle, to be considered as representative of the daily values of dynamic MPPT efficiency.

abstract: Photovoltaic (PV) systems are affected by converter losses, partial shading and other mismatches in the panels. This dissertation introduces a sub-panel maximum power point tracking (MPPT) architecture together with an integrated CMOS current sensor circuit on a chip to reduce the mismatch effects, losses and increase the efficiency of the PV system. The sub-panel MPPT increases the efficiency of the PV during the shading and replaces the bypass diodes in the panels with an integrated MPPT and DC-DC regulator. For the integrated MPPT and regulator, the research developed an integrated standard CMOS low power and high common mode range Current-to-Digital Converter (IDC) circuit and its application for DC-DC regulator and MPPT. The proposed charge based CMOS switched-capacitor circuit directly digitizes the output current of the DC-DC regulator without an analog-to-digital converter (ADC) and the need for high-voltage process technology. Compared to the resistor based current-sensing methods that requires current-to-voltage circuit, gain block and ADC, the proposed CMOS IDC is a low-power efficient integrated circuit that achieves high resolution, lower complexity, and lower power consumption. The IDC circuit is fabricated on a 0.7 um CMOS process, occupies 2mm x 2mm and consumes less than 27mW. The IDC circuit has been tested and used for boost DC-DC regulator and MPPT for photo-voltaic system. The DC-DC converter has an efficiency of 95%. The sub-module level power optimization improves the output power of a shaded panel by up to 20%, compared to panel MPPT with bypass diodes. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2014

A energia solar fotovoltaica é a forma de produção de eletricidade que mais cresce no mundo. A potência instalada mundial, até o ano de 2010, era de cerca de 40 GWP e a previsão é de que, somente em 2011, este cifra seja aumentada em mais 24 GWP. O inversor é o elemento central dos sistemas fotovoltaicos. Além de executar a conversão da energia elétrica em corrente contínua para corrente alternada, ele também é responsável pelo gerenciamento da energia entregue à rede e pelo seguimento do ponto de máxima potência. O seguimento do ponto de máxima potência (MPPT) é um processo de controle no qual o inversor procura manter o gerador fotovoltaico operando em uma região da sua curva característica na qual o produto corrente × tensão tenha o seu valor máximo, de forma a otimizar a extração de potência do gerador fotovoltaico. A eficiência de MPPT é um número que indica o grau de precisão, tanto em termos de rapidez como de magnitude, com que o seguidor do ponto de máxima potência atinge o seu objetivo. Assim podem ser definidas duas eficiências de MPPT: a eficiência estática, associada a situações em que a irradiância solar permanece constante durante o intervalo considerado, e a eficiência dinâmica de MPPT, que considera os momentos de variação na intensidade da irradiância, resultantes, por exemplo, da passagem de nuvens. As eficiências de MPPT (especialmente a dinâmica) são de difícil determinação, porém a tarefa fica muito facilitada com a utilização de um simulador de arranjos fotovoltaicos. A norma européia EN 50530:2010 Overall Efficiency of Photovoltaic Inverters propôs uma metodologia para a determinação da eficiência dinâmica de MPPT utilizando perfis variáveis de irradiância a serem programados no simulador de arranjos fotovoltaicos. O objetivo central da tese é fazer uma análise experimental da eficiência dinâmica do seguimento de máxima potência de inversores conectados à rede através da comparação dos resultados de eficiência obtidos seguindo a metodologia definida na norma citada com resultados obtidos a partir de medições em tempo real ao longo de um dia, verificando a adequação da norma às situações de campo. Para a obtenção dos dados de entrada do simulador foram medidas, por diversos dias, a irradiância e temperatura de uma célula de referência. Os inversores foram conectados à saída do simulador de arranjos fotovoltaicos e foram reproduzidas as condições de irradiância e temperatura de três dias selecionados em função do grau de nebulosidade, com comportamento dinâmico semelhante aos perfis de irradiância da norma. Os resultados foram, na maioria dos casos, discordantes. Uma análise dos resultados parciais de eficiência dinâmica indicou como causa desta discrepância a dependência que a eficiência dinâmica de MPPT tem com a taxa de variação da irradiância. Conclui-se que, embora as seqüências de irradiância propostas pela norma constituam uma eficiente ferramenta para o diagnóstico de eventuais deficiências no comportamento do seguidor de máxima potência de inversores, a média dos valores de eficiência de MPPT calculados a partir delas não pode, em princípio, ser considerada como representativa de valores diários. / Photovoltaic solar energy is the fastest growing electricity source in the world. The worldwide capacity until 2010 was about 40 GWP and, by the end of 2011, this figure will be increased by another 24 GWP. The inverter is the pivotal element of PV systems. In addition to performing the conversion of electrical energy from direct current to alternating current, the inverter is also responsible for the management of the energy delivered to the grid and for performing the maximum power point tracking. The maximum power point tracking (MPPT) is a control process by which the inverter tries to keep the PV generator operating in a region of its characteristic curve where the product current × voltage reaches its maximum value. The MPPT efficiency is a figure that indicates the degree of precision, both in terms of speed and magnitude, that the MPPT reaches its goal. Thus, two MPPT efficiencies can be defined: the static efficiency, associated to situations in which the solar irradiance does not vary during the considered interval, and also the dynamic MPPT efficiency, which considers the variation of the irradiance intensity as a result, for example, of the passage of clouds. MPPT efficiencies (especially the dynamic) are hard to determine, but the task becomes much easier with the use of a photovoltaic array simulator. The European standard EN 50530:2010 Overall Efficiency of Photovoltaic Inverters proposes a methodology for determining the dynamic efficiency of MPPT using variable irradiance profiles to be programmed into the photovoltaic array simulator. The main objective of this thesis is to make an experimental analysis of the dynamic MPPT efficiency of grid connected inverters by comparing the efficiency results obtained by following the methodology defined in the referred standard with results obtained from real time measurements in the course of a day, checking the adequacy of the standard when applied to field situations. In order to obtain the input data for the simulator, the irradiance and temperature of a reference cell were measured for several days. The inverters were connected to the output of the array simulator, which reproduced the conditions of irradiance and temperature for three days selected according to the degree of cloudiness, having a dynamic behavior similar to the standard irradiance profiles. The results, in most cases, disagree. An analysis of partial results of dynamic efficiency indicated the dependence of the dynamic MPPT efficiency to the rate of irradiance change as the cause of this discrepancy. As a conclusion, it can be stated that, although the sequences of irradiance proposed by the standard are an efficient tool for the diagnosis of deficiencies in the behavior of the MPP tracker, the average efficiency of MPPT calculated from the sequences cannot, in principle, to be considered as representative of the daily values of dynamic MPPT efficiency.

Ce mémoire présente le travail de recherche qui consiste à développer et à mettre au point un dispositif capable d'alimenter en électricité un habitat isolé et le rendre autonome en utilisant des sources d'énergie renouvelable. Le système multi-sources considéré comprend une éolienne et des panneaux photovoltaïques comme sources principales, des batteries de type Lithium-Ion pour le stockage ainsi qu'un générateur Diesel comme source de secours. Dans le but d'apporter une contribution face aux problèmes de gestion d'énergie pour systèmes hybride et la commande des chaînes de conversion d'énergie renouvelable, nous proposons dans ce travail une stratégie de gestion des flux de puissances basée sur la prédiction des potentiels énergétiques sur un horizon très-court pour générer des références optimales pour assurer l'autonomie de la charge. Pour cela, nous présentons dans un premier temps, un dimensionnement des différents modules du système multi-sources ainsi que la modélisation de chacune des chaînes de conversion d'énergie. Par la suite, cette modélisation nous a permis de développer des lois de commande en utilisant les techniques LMI pour le placement de pôles dans le but d'augmenter les performances transitoires du suivi de références. L'algorithme de gestion proposé ainsi que les stratégies de commande développées pour le suivi de références et la maximisation de puissance ont été validées en simulation en utilisant des données issues de mesures réelles. Après avoir obtenu des résultats en simulation avec Matlab/Simulink, nous avons validé ces travaux expérimentalement en réalisant des tests sur la plateforme multi-sources équipée de cartes dSPACE du laboratoire / This dissertation presents a research project that consists of the development of a device that is able to supply an isolated house with electricity and to make it autonomous by using renewable energy sources. The multi-source system considered in this thesis includes a wind turbine and photovoltaic panels as main sources, Lithium-Ion batteries for storage and Diesel generator as emergency source. In order to make a contribution considering problems of energy management for hybrid systems as well as problems in controlling energy conversion chains, we are suggesting a power flow management strategy which is based on the prediction of the potential energy available on the veryshort-term. That strategy aims at generating optimal references in order to insure the electrical autonomy of the house. For this, we present firstly, a sizing and modelingof the different modules of the multi-source system. This modelling allowed us subsequently to develop a static and dynamic state feedback control strategies by using LMI techniques for pole placement in order to increase the transition performancesfor reference monitoring. The proposed management algorithm as well as the developed control strategies for tracking and maximizing power is validated in simulation using data obtained through real measurements. After having results in simulationusing Matlab/Simulink, we have validated them experimentally by conducting tests via a multi-source platform equipped with dSPACE cards of our laboratory

La naturaleza no ideal de los procesos de conversión de energía se manifiesta en la aparición de distintos puntos de operación, para los cuales la eficiencia de la transformación difiere apreciablemente. Dentro de ellos, los mecanismos a través de los cuales se genera la electricidad plantean la necesidad de abordar el asunto de la generación eficiente hasta el máximo grado económicamente justificable. En esta misma línea, los actuales niveles de precios de la energía eléctrica han despertado el interés por aprovechar fuentes que hasta hace poco no parecían competitivas, impulsando así el perfeccionamiento de sus tecnologías de explotación asociadas. Los sistemas fotovoltaicos (FV) destacan por presentar mínimos costos de operación y elevadas inversiones, quedando su viabilidad económica fuertemente asociada a la capacidad de maximizar la energía generada usando equipos de bajo costo. Este trabajo busca diseñar y construir un equipo capaz de manejar la curva de carga de los sistemas FV igualando la impedancia aparente de la carga a la impedancia interna de la fuente, asegurando así alcanzar la máxima tasa de transferencia de energía. Actualmente se observa un aumento en la presencia de estos dispositivos, conocidos en la literatura como “seguidores del punto de máxima potencia” (MPPT, por sus siglas en inglés), gracias a que los avances en equipos electrónicos de potencia permiten contar con ellos a un precio razonable. Se presenta el desarrollo de un MPPT para aplicaciones móviles y estacionarias consistente en un conversor CC/CC de tipo elevador con rectificación sincrónica, realimentado por un lazo de maximización de la corriente entregada a la carga. El control hace uso de un algoritmo capaz de detectar máximos en dominios no convexos y hacer un seguimiento dinámico de ellos, manteniendo un punto de operación en el panel solar cercano al de máxima potencia. La topología del convertidor CC/CC permite transferir energía entre distintos niveles de tensión en ambos sentidos y su eficiencia se beneficia de la introducción de un MOSFET rectificador. Además, la operación en paralelo de varias de estas unidades es directa y la migración hacia su uso en otras fuentes de corriente continua se puede llevar a cabo con mínimas modificaciones en el algoritmo. El diseñoo y la construcción del convertidor CC/CC es descrita en detalle haciendo especial énfasis en la elección de los transistores de potencia, su sistema de disparo y el cálculo del núcleo del inductor. Se discuten los algoritmos para condiciones de operación normal y ante paneles dañados, desarrollándose un cálculo teórico del rendimiento del sistema que explica el 99,96% de las pérdidas medidas. Las pruebas empíricas se realizan para el caso de un panel fotovoltaico de 200 [W] nominales, obteniéndose una eficiencia del 94,87% en el conversor ante una potencia de entrada de 100 [W] y una pérdida de eficiencia del 1,07% asociada al comportamiento del algoritmo de mantención del punto de máxima potencia. Se propone como trabajo futuro mejorar el rendimiento del dispositivo mediante el uso de convertidores resonantes y algoritmos basados en la respuesta dinámica de las celdas FV.

Dans les nombreuses études actuelles sur le photovoltaïque, on assiste à de grands progrès tant dans le domaine des cellules à haut rendement énergétique, que sur les structures liées à l'exploitation. Afin de tirer parti de toute l'énergie produite, il a paru de tout premier ordre d'orienter les recherches sur les architectures parallèles en bus haute tension. Pour la génération de hautes tensions il est impératif d'utiliser des convertisseurs spécialement adaptés. En effet, si on utilise des convertisseurs classiques on se heurte à la problématique des pertes dans les composants de puissance, et notamment le transistor MOSFET de commutation utilisé pour le découpage. Une première étude a permis de vérifier que les contraintes de tension entraînent pour le transistor des pertes importantes aux tensions élevées. Cette première étude montre que seuls les transistors de faible tension inférieure à 100V ont des caractéristiques intéressantes pour notre application. Une recherche systématique a abouti à l'élaboration d'un convertisseur Boost à couplage magnétique. Grâce au recyclage des énergies parasites, les essais montrent que ce montage est bien adapté à notre application permettant d'obtenir des rendements de plus de 90%. Parmi les différentes stratégies d'extraction de puissance, le MPPT à incrément de conductance a été choisi pour ses qualités de précision et de facilité de mise en œuvre. Chaque panneau équipé d'un convertisseur envoie la puissance recueillie sur le bus haute tension, lui même relié à un onduleur de type SMA / In various studies on photovoltaic, major progresses have been observed, both concerning the cells and also in the field of their use. In order to take advantage of the energy it has been paramount to focus on parallel High Voltage bus. This High Voltage generation requires dedicated converters. In fact, using classical converters implicates important losses in the MOSFET used for switching. In a prior study we could ascertain important losses on transistors when submitted to high voltages as we assumed. It was shown then that only the transistors supporting a voltage less than 100V can be used for our application. A systematic investigation led to the Magnetically Coupled Boost converters. Thanks to the recycling of parasitic losses, our tests show an efficiency superior than 90%. Among the different power extraction strategies, the incremental conductance MPPT was used because of its top of the arts performances and convenience. Every DC/DC implemented panel converter supplies the HVDC bus which, itself, is connected to the SMA inverter

The advancement in solar panel and battery technology makes them useful for energy supply and storage. This thesis involves the modeling and charging control of a lithium ion battery system for solar panels. The proposed model is based on the parameters and characteristics of a realistic battery and solar panel system; and the hybrid control approach combines the advantages of the adaptive incremental conductance method and the perturb and observe method to track the maximum power point of the solar panel for charging the battery unit. Computer simulation results demonstrate that this proposed approach offers a faster convergence rate than the adaptive incremental conductance method, and less steady-state error than the perturb and observe method.

No description available.

Recent research and industrial accomplishment has revealed the advantages of cascaded smart converter PV system over traditional centralized and string PV system. However, even by adopting the cascaded smart converter, it is not always possible to track maximum power point (MPP) for all the panels under heavy shading condition, and a central converter is still required to track the peak power point of PV array. Based on the analysis of system configurations for smart converter PV system, an alternative PV system configuration is introduced which can extract peak power from all the panels under different mismatch condition and connect PV array to 380V DC bus without central converter. Based on this alternative PV system configuration, a multi-phase smart converter with single controller is proposed as a low cost panel-level MPPT solution. This proposal can largely reduce cost by saving MPPT controllers, current and voltage sensors without sacrificing energy production. The effectiveness of the proposal has been verified by both simulation and experiment results. / Master of Science

In order to avoid the accidents like Fukushima Disaster and monitor the operation status of nuclear power plant, a wireless sensor system which is powered by the Thermoelectric Generator (TEG) Energy Harvester is designed and built. Meanwhile, a power converter circuit has also been designed to converter the output voltage of TEG Energy Harvester to a DC voltage to charge the battery or power the application systems. Several prototypes based on this power converter circuit have been built for Thermoelectric Generator (TEG) energy harvester and tested in both working and laboratory conditions. The reliability of the TEG Energy Harvester system in the gamma radiation environment has been examined in the experiments. Based on the experiments results, the design was optimized. And an optimized Maximum Power Point Tracking algorithm has also been applied in the prototype to extract the maximum power from the TEG Energy Harvester in all conditions. The TEG Energy Harvester system would be greatly simplified as a new type of sensor will be applied. The design of the signal conditioning circuit for this sensor has also been presented. / Master of Science