Role of wide bandgap materials in power electronics for smart grids applications

At present, the energy transition is leading to the replacement of large thermal power plants by distributed renewable generation and the introduction of different assets. Consequently, a massive deployment of power electronics is expected. A particular case will be the devices destined for urban environments and smart grids. Indeed, such applications have some features that make wide bandgap (WBG) materials particularly relevant. This paper analyzes the most important features expected by future smart applications from which the characteristics that their power semiconductors must perform can be deduced. Following, not only the characteristics and theoretical limits of wide bandgap materials already available on the market (SiC and GaN) have been analyzed, but also those currently being researched as promising future alternatives (Ga2O3, AlN, etc.). Finally, wide bandgap materials are compared under the needs determined by the smart applications, determining the best suited to them. We conclude that, although SiC and GaN are currently the only WBG materials available on the semiconductor portfolio, they may be displaced by others such as Ga2O3 in the near futur

Fault location in low-voltage distribution networks based on reflectometry - a case study

Fault location can help transport and distribution system operators in their effort of minimizing supply interruption times. Nowadays, fault location devices are widely extended in the transport grid. However, the application of these solutions to distribution networks is not a feasible option due to the high cost of this equipment. Therefore, current research is focussed on costeffective fault location techniques which are adapted to electrical distribution networks. This paper presents results of a case study, conducted with detailed simulation models of two actual low-voltage (LV) distribution grids, using PSCAD software. One is a typical rural grid with long aerial lines, while the other is a typical urban grid with shorter line lengths which are mostly installed underground. The analysis is focussed on fault location based on travelling wave theory and reflectometry methods. The simulations include distributed parameter line models and a signal injector, in order to analyse the singular effects in the waveform which are caused by the special features of the LV network. It is shown that LV networks have some unique features which are not present in medium and highvoltage grids, which makes effective fault location more challenging. Observed issues are discussed and future work is proposed in order to overcome some of them.This research was funded by the “Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación” grant number “RTC-2017-6782-3” and the European Union FEDER funds with name “LOcalización de averías, monitorización de estado y Control en redes de bAja TEnsión—LOCATE”

Novel utility-scale photovoltaic plant electroluminescence maintenance technique by means of bidirectional power inverter controller

Producción CientíficaNowadays, photovoltaic (PV) silicon plants dominate the growth in renewable energies generation. Utility-scale photovoltaic plants (USPVPs) have increased exponentially in size and power in the last decade and, therefore, it is crucial to develop optimum maintenance techniques. One of the most promising maintenance techniques is the study of electroluminescence (EL) images as a complement of infrared thermography (IRT) analysis. However, its high cost has prevented its use regularly up to date. This paper proposes a maintenance methodology to perform on-site EL inspections as efficiently as possible. First, current USPVP characteristics and the requirements to apply EL on them are studied. Next, an increase over the automation level by means of adding automatic elements in the current PV plant design is studied. The new elements and their configuration are explained, and a control strategy for applying this technique on large photovoltaic plants is developed. With the aim of getting on-site EL images on a real plant, a PV inverter has been developed to validate the proposed methodology on a small-scale solar plant. Both the electrical parameters measured during the tests and the images taken have been analysed. Finally, the implementation cost of the solution has been calculated and optimised. The results conclude the technical viability to perform on-site EL inspections on PV plants without the need to measure and analyse the panel defects out of the PV installation.Ministerio de Industria, Economía y Competitividad (grant number RTC-2017-6712-3)Junta de Castilla y León (grant VA283P18

Mejora de sistemas de electrónica de potencia para el despliegue masivo de recursos energéticos distribuidos y vehículo eléctrico en redes de distribución de baja tensión

Con el objetivo de reducir los gases contaminantes un 55 % para el año 2030, la Comisión Europea ha establecido como objetivos prioritarios un aumento de la generación renovable hasta el 32 % de la generación energética total y un incremento de la eficiencia energética del 32,5 %. El cumplimiento de estos objetivos acarrea una serie de desafíos para el sistema eléctrico que deben ser considerados durante este proceso de transformación. El cierre de los grandes generadores síncronos, fuente de estabilidad para la red, y su reemplazo por fuentes renovables, de gran variabilidad y escasa o nula aportación inercial, están centrando gran parte del esfuerzo de la comunidad investigadora en el sector.En este contexto, los convertidores de electrónica de potencia están despertando un gran interés debido a dos factores determinantes. En primer lugar, el gran número de convertidores que se espera sean instalados en los próximos años. Desde los grandes inversores fotovoltaicos a dispositivos más pequeños, pero mucho más numerosos, como equipos de climatización o cargadores de vehículo eléctrico. Por otro lado, la gran controlabilidad de estos sistemas incrementa la posibilidad de implementar técnicas que contribuyan a asegurar la estabilidad de la red eléctrica durante el proceso de cierre de las centrales térmicas.La presente tesis doctoral contribuye al estado del arte del sector por medio de las aportaciones en el estudio de los convertidores de electrónica de potencia, los nuevos materiales que prometen ampliar las capacidades de estos dispositivos y la implementación de técnicas para la prestación de servicios auxiliares a la red. Debido al creciente protagonismo de la red distribución, así como el interés despertado por la creación de comunidades energéticas y las redes inteligentes, más conocidas como Smart Grids, este trabajo se centra en la aplicación de servicios orientados a la casuística de las redes de distribución en baja tensión.En este documento se presta especial atención al problema de los desequilibrios, un problema frecuente en las redes de distribución. Este evento tiene lugar cuando la tensión o la corriente diverge entre las tres fases, ocasionando perjuicios en los usuarios de la red, así como posibles daños en distintos elementos del sistema, como los conductores y transformadores.A continuación, se realiza el diseño y fabricación de un convertidor D-STATCOM de 30 kVA para la atenuación de desequilibrios en la red de baja tensión. El prototipo ha sido validado en un entorno real perteneciente a una línea de la red de distribución. De los resultados obtenidos durante el periodo de evaluación se han cuantificando los beneficios de la mitigación de desequilibrios, tales como la mejora de la calidad de red y la reducción de las pérdidas técnicas en la línea.Posteriormente, se propone la aplicación de esta solución a diferentes convertidores comerciales tales como cargadores de vehículo eléctrico, inversores fotovoltaicos y sistemas de baterías. El trabajo concluye con el desarrollo de un cargador de vehículo eléctrico de 50 kW con la capacidad de proveer los servicios auxiliares propuestos en el estudio.<br /

Role of Wide Bandgap Materials in Power Electronics for Smart Grids Applications

At present, the energy transition is leading to the replacement of large thermal power plants by distributed renewable generation and the introduction of different assets. Consequently, a massive deployment of power electronics is expected. A particular case will be the devices destined for urban environments and smart grids. Indeed, such applications have some features that make wide bandgap (WBG) materials particularly relevant. This paper analyzes the most important features expected by future smart applications from which the characteristics that their power semiconductors must perform can be deduced. Following, not only the characteristics and theoretical limits of wide bandgap materials already available on the market (SiC and GaN) have been analyzed, but also those currently being researched as promising future alternatives (Ga2O3, AlN, etc.). Finally, wide bandgap materials are compared under the needs determined by the smart applications, determining the best suited to them. We conclude that, although SiC and GaN are currently the only WBG materials available on the semiconductor portfolio, they may be displaced by others such as Ga2O3 in the near future

A Novel Charging Station on Overhead Power Lines for Autonomous Unmanned Drones

Innovative drone-based technologies provide novel techniques to guarantee the safety and quality of power supply and to perform these tasks more efficiently. Electric multirotor drones, which are at the forefront of technology, face significant flight time limitations due to battery capacity and weight constraints that limit their autonomous operation. This paper presents a novel drone charging station that harvests energy from the magnetic field present in power lines to charge the drone’s battery. This approach relies on a charging station that is easy to install by the drone on an overhead AC power line without modifying the electrical infrastructure. This paper analyses the inductive coupling between the energy harvester and the power line, electrical protection, the power electronics required for maximum power point tracking and the mechanical design of the charging station. A drone that perches on a cable, an end effector for installation procedures and the charging maneuver are described, along with discussion of the robotic and electrical tests performed in a relevant environment. Finally, a lightweight drone charging station capable of harvesting 145 W of power from a 600 A line current is reported