Modelado y metodología analítica de diseño de transformadores de potencia y alta frecuencia: análisis de los devanados, optimización de eficiencia y densidad de potencia e integración en el diseño de convertidores electrónicos

Esta tesis se centra en el estudio y análisis del diseño de transformadores de potencia y alta frecuencia. Los principales temas tratados en esta tesis se resumen a continuación: - Realización del estado del arte y síntesis del modelado de transformadores de potencia y alta frecuencia, haciendo especial hincapié en el estudio de los materiales magnéticos, los fenómenos de alta frecuencia en los devanados, el cálculo de pérdidas en el núcleo y en el cobre y las técnicas que permiten su atenuación. - Tratamiento específico de formas de onda no senoidales de tensión y corriente. - Realización del estado del arte de los métodos de diseño existentes. Evaluación de la bondad de las reglas de oro, rules of thumb, en el diseño de transformadores. - Análisis teórico del problema de diseño y definición del concepto de diseño óptimo en términos de densidad de potencia y eficiencia para un rango de frecuencias de 1 a 150 kHz y de potencias de 500 W a 25 kW. - Desarrollo de una metodología analítica de diseño que conduce al diseño óptimo en términos de selección del material magnético, proporciones y tamaño del núcleo magnético, disposición de los devanados (reparto de ventana e intercalado), tipo de cable y su dimensionado, y nivel de inducción magnética. - Ejemplos de diseño: inversor fotovoltaico y convertidor forward. Realización de diseños prácticos y verificación experimental. Tratamiento de la problemática de la medida de pérdidas en estas aplicaciones. - Estudio de las tendencias presentes en la densidad de potencia y la eficiencia de los diseños óptimos en función de la potencia y la frecuencia de la aplicación. - Proposición de diversas fórmulas para posibilitar la integración del diseño de transformadores en el proceso de diseño y dimensionado de los convertidores electrónicos de potencia.Programa Oficial de Doctorado en Energías Renovables (RD 1393/2007)Energia Berriztagarrietako Doktoretza Programa Ofiziala (ED 1393/2007

The generalized bode criterion: application to the dc voltage control of a three-phase photovoltaic grid-tied inverter

As renewable energies are becoming more important in the electrical generation system, power electronic converters are facing new design issues related not only to their components but also to their control loops. In this context, the Generalized Bode Criterion (GBC) appears as a good tool to correctly determine stability and to help the controller design. In order to show the potential of the GBC and how it can be applied, this paper studies a dc voltage regulation with compensation of the photovoltaic power in a three-phase photovoltaic grid-tied inverter.info:eu-repo/semantics/embargoedAcces

Winding resistance measurement in power inductors - understanding the impact of the winding mutual resistance

Inductors are cornerstone components in power electronics converters. Since winding loss is the dominant loss mechanism in these components, its accurate measurement is fundamental for the validation of the inductor's operation and design. The techniques for the winding resistance R_{w} measurement in power inductors can be classified into two groups, indirect and direct. Both techniques use coupled inductors to separate winding and core power losses. If coupled inductors with non-zero winding mutual resistances R_{w,m} are used, invalid results are obtained with these techniques. Understanding the meaning of R_{w,m} in coupled inductors is complex. In this paper, the impact of R_{w,m} on the inductor R_{w} measurement techniques is demonstrated and practical guidelines for the design of the zero R_{w,m} coupled inductors are given. Particularly, the location of the auxiliary winding for the direct technique is investigated. In order to compare the R_{w} measurement techniques and to validate the coupled inductor's R_{w,m} impact, two different inductors are built and tested. The results are compared with the values for R_{w} calculated by FEA simulation. It is found that only the direct technique with an auxiliary winding carefully designed and located following the guidelines given in this paper makes the accurate measurement of R_{w} in power inductors possible.This work was supported in part by the Spanish State Research Agency (AEI) and the FEDER-UE under Grant PID2019-110956RB-I00/AEI/10.13039/501100011033, and in part by the Ingeteam Power Technology

Novel three-phase topology for cascaded multilevel medium-voltage conversion systems in large-scale PV plants

Solar photovoltaic renewable energy systems are expanding in the power sector thanks to its increasingly competitive prices. Traditionally, large-scale PV plants have reduced their cost by increasing the power ratings of the inverters and the line-frequency transformers. However, cost-reduction limits of large-scale PV plants are being reached. Cascaded converters have appeared as a solution to continue reducing the cost of large PV plants as they reduce the wiring cost. In this paper, a novel three-phase topology for cascaded conversion structures is proposed. It only has 2 conversion steps, one without switching losses. Hence, it increases the efficiency and reduces the cost of the previously proposed cascaded conversion systems. The topology is patent pending.The authors acknowledge the financial and continuous support of INGETEAM POWER TECHNOLOGY

Medium-voltage cascaded sequential topology for large-scale PV plants

Photovoltaic (PV) conversion systems are in continuous development due to their increasingly competitive prices. The traditional configuration of large-scale PV plants is based on high-power central inverters, which have reduced their cost by increasing their power rating. However, this cost reduction is expected to saturate in the near future, mainly due to an increase in the cost of the dc wiring. Cascaded conversion systems have appeared as potential solutions to continue reducing the PV plant cost. They consist of several conversion units whose ac outputs are connected in series. This enables the power-rating reduction of each individual conversion unit, while maintaining the power rating of the conversion structure. Thus, the conversion units are placed closer to the PV panels, reducing the dc wiring cost. In this paper, a novel three-phase topology for medium-voltage cascaded conversion systems is presented. The proposed topology is formed of several conversion units, each one with a reduced number of conversion stages, namely, dc/ac, medium-frequency isolation and ac/ac. Moreover, thanks to its sequential operation and modulation technique, zero-voltage switching and zero-current switching are achieved in all conversion stages. In this way, with respect to the configuration with central inverters, the proposed topology has the advantages of cascaded conversion systems. In comparison to previously investigated cascaded topologies, the proposed topology also presents promising characteristics, representing a potential cost reduction and efficiency increase. An experimental validation of the topology is carried out in a laboratory prototype consisting of three conversion units.This work was supported in part by the Spanish State Research Agency (AEI) under Grant PID2019-110956RB-I00 /AEI/10.13039/501100011033, and in part by the Public University of Navarre through a Ph.D. Scholarship

Active control for medium-frequency transformers flux-balancing in a novel three-phase topology for cascaded conversion structures

Efficiency and power density are important parameters in the design of power electronics converters. In many applications, low-frequency transformers are being substituted for medium-frequency and high-frequency transformers in order to reduce the volume and therefore the cost of the transformer. However, preventing their saturation is a complex task. This paper studies the medium-frequency transformers' flux balancing in a novel three-phase topology for cascaded conversion structures.Based on the modulation technique of the converter, a method to directly measure the magnetizing current of the medium-frequency transformers is proposed in this paper. A control loop to regulate the dc value of the magnetizing current is also designed and developed. Simulation results validate the correct operation of the control loop, which prevents the transformer saturation.This work was supported by the Spanish State Research Agency (AEI) under grants PID2019-110956RB-I00 /AEI/ 10.13039/501100011033 and DPI-2016-80641-R, and by the Public University of Navarre through a doctoral scolarship