BUSCADOR RECOLECTA

Póster presentado a la 17th European Conference on Power Electronics and Applications, EPE-ECCE Europe. Ginebra (Suiza), 2015., This paper describes a tool developed for the performance evaluation and failure detection in a 45.6 MWp PV plant installed by the company Acciona in Amareleja (Portugal). The paper describes the PV plant configuration and its SCADA (Supervisory Control And Data Acquisition), the measured variables and the main functionalities of the software. Some of these functionalities are the automatic and accurate PSTC (Power under standard test conditions1) calculation for each generator and for the whole PV Plant, the reference production that would be delivered by the PV plant assuming a 100% availability, the hierarchy of SCADA alarms, the detection of long-term trends and degradation in PV generators, possible hidden problems in the different equipment and systems composing the PV plant, etc. This tool entered into operation in 2011 and is working properly since then., This work has been partially financed by the Seventh Framework Programme of the European Commission with the project PVCROPS (Photovoltaic Cost Reduction, Reliability, Operational Performance, Prediction and Simulation – Grant Agreement no: 308468) and by the Spanish Ministry of Economy and Competitiveness under Grant DPI2013-42853-R.

El primer objetivo concreto de la tesis consiste en estudiar los perfiles de potencia de los diferentes elementos de la microrred y su interacción, ya sea directa, en el caso de flujos de potencia confluyentes, o indirecta, en el caso de la posible interacción de distintos sistemas (sistema eléctrico y térmico). Este análisis se realiza en el Capítulo 2.
El segundo objetivo es el diseño de estrategias de gestión energética para la microrred y evaluación comparativa en base a criterios específicos de calidad. Este objetivo se desarrolla en los Capítulos 3 a 7.
En los Capítulos 3 y 4, se desarrollan y analizan estrategias de gestión sin datos de predicción. Las estrategias del Capítulo 3 basan su gestión en el control de la batería en función del balance de potencias instantáneo, mientras que en el Capítulo 4 se desarrollan estrategias de similar estructura, pero basándose en el balance energético diario en la microrred.
Consecuencia del análisis de estas primeras estrategias, se verá la necesidad de utilizar predicción de la potencia. Para ello, se analiza en el Capítulo 5 la predicción del consumo y de la generación estudiando por separado los datos medidos por los vatímetros y la estación meteorológica de la microrred, los datos de predicción meteorológica ofrecidos por el servidor utilizado y los modelos físicos que ayudan a transformar los datos de variables ambientales en datos de potencia generada.
Posteriormente, en el Capítulo 6 se analizan las ventajas de la utilización de los datos de predicción y cómo utilizarlos, poniéndose en práctica su uso. La estructura del control propuesto es similar a la vista en el Capítulo 4, pero, debido a la naturaleza de los datos de predicción, se desarrolla un nuevo control de la batería basado en el error de la predicción. Este control mejora notablemente los resultados en comparación con los obtenidos en las estrategias previas. No obstante, del análisis de esta estrategia, queda patente la influencia que tiene el sistema térmico sobre el eléctrico, que puede ser negativa si se deja que evolucione de forma independiente. Por el contrario, el sistema térmico puede ser muy beneficioso si la estrategia toma el control del mismo. Así, en el Capítulo 7, se hace uso de una caldera eléctrica gestionable, que hace de nexo entre el sistema eléctrico y el térmico, y un depósito de agua caliente que sirve de almacén de energía térmica. De esta forma, se fusiona la gestión de ambos sistemas creando un único sistema energético, denominado microrred electrotérmica.
El tercer objetivo de la tesis es la validación experimental de los resultados obtenidos. Así, realizados los análisis de las distintas estrategias mediante simulación, se prueba su funcionamiento en la microrred instalada en el Laboratorio de Energías Renovables de la UPNA. Su implementación y los resultados obtenidos se detallan en el Capítulo 8.
Finalmente, en el Capítulo 9 se repasan las principales conclusiones y se presentan las líneas futuras., Esta tesis ha sido financiada por el Gobierno de Navarra y los fondos FEDER bajo el proyecto “Diseño, desarrollo e implantación de microrredes en Navarra” (2009024085 y 2012024132), por el Gobierno de España a través del Ministerio de Economía y Competitividad bajo el proyecto “Tecnologías para la integración en la red de energías renovables: electrónica de potencia, almacenamiento, gestión energética e interacción con la red” (DPI2013-42853-R) así como por la Comisión Europea bajo el proyecto “PVCROPS-Photovoltaic Cost reduction, reliability, operational performance, prediction and simulation” (FP7-308468)., Programa Oficial de Doctorado en Energías Renovables (RD 1393/2007), Energia Berriztagarrietako Doktoretza Programa Ofiziala (ED 1393/2007)

Foil conductors and primary and secondary interleaving are normally used to minimize winding losses in high frequency transformers used for high-current power applications. However, winding interleaving complicates the transformer assembly, since taps are required to connect the winding sections, and also complicates the transformer design, since it introduces a new tradeoff between minimizing losses and reducing the construction difficulty. This paper presents a novel interleaving technique, named maximum interleaving, that makes it possible to minimize the winding losses as well as the construction difficulty. An analytical design methodology is also proposed in order to obtain free cooled transformers with a high efficiency, low volume and, therefore, a high power density. For the purpose of evaluating the advantages of the proposed maximum interleaving technique, the methodology is applied to design a transformer positioned in the 5 kW 50 kHz intermediate high frequency resonant stage of a commercial PV inverter. The proposed design achieves a transformer power density of 28 W/cm3 with an efficiency of 99.8%. Finally, a prototype of the maximum-interleaved transformer is assembled and validated satisfactorily through experimental tests., This work
was supported in part by the Spanish Ministry of Economy and Competitiveness
under Grants DPI2010-21671-C02-01 and DPI2013-42853-R and by the Public
University of Navarre.

Los inconvenientes medioambientales, sociales y económicos que presentan
los combustibles fósiles y nucleares están propiciando un uso cada vez mayor
de fuentes de energía renovables. El fuerte desarrollo tecnológico de los sistemas
de generación basados en estas fuentes de energía, especialmente de
los sistemas eólicos y fotovoltaicos, ha abaratado enormemente sus costes de
producción, resultando ya tecnologías competitivas en relación con las plantas
convencionales. Actualmente, el principal obstáculo que limita su integración
masiva en la red eléctrica es su gestionabilidad, dada la naturaleza intermitente
del recurso renovable. Los sistemas de almacenamiento energético distribuidos,
y en particular las baterías de litio y los supercondensadores, surgen como una
de las mejores alternativas para mejorar la gestión de esta energía y facilitar
la operación de una red el ectrica cada vez más basada en sistemas renovables.
Esta tesis analiza en profundidad ambas tecnologías de almacenamiento,
especialmente cuando funcionan en entornos de generación renovable. Las
principales líneas de trabajo de la tesis son: Análisis del estado actual de las tecnologías; Estudio de la influencia de los fenómenos termodinámicos, electroquímicos y térmicos en el funcionamiento de estos sistemas de almacenamiento; Modelado electroquímico y térmico de ambas tecnologías de almacenamiento; Estimación del estado de carga y del envejecimiento en baterías de litio; Validación experimental de los modelos propuestos ante diferentes condiciones de funcionamiento; Desarrollo de metodologías para el diseño y funcionamiento óptimo de sistemas de almacenamiento basados en baterías de litio en entornos renovables y particularización para centrales fotovoltaicas., Environmental, social and economic drawbacks of fossil and nuclear fuels are
leading to an increased use of renewable energy sources. The strong technological
development of renewable-based generation systems during the last years,
especially in the case of wind and photovoltaic systems, has led to an impressive
reduction of production costs and made these technologies competitive
with conventional power plants. At present, the main barrier that limits their
massive integration into the electrical grid is their reduced manageability due
to the intermittent nature of renewable resources. Distributed energy storage
systems, particularly lithium-ion batteries and supercapacitors, arise as one of
the best options to provide manageability to these systems and help operate
an electrical grid increasingly based and dependent on renewable power plants.
This thesis analyses in depth both energy storage technologies, in particular
when they operate in renewable generation systems. The main research
lines of the thesis are: Analysis of the state of the art of lithium-ion battery and supercapacitor
technologies; Study of the infuence of thermodynamic, electrochemical and thermal phenomena on the operation of these storage technologies; Electrochemical and thermal modelling of both technologies; Estimation of the state of charge and ageing of lithium-ion batteries; Experimental validation of the proposed models under different operating conditions; Development of methodologies for the optimal design and operation of storage systems based on lithium-ion batteries in renewable environments,
and implementation in photovoltaic power plants., This thesis has been subsidised by the FPU Program of the Spanish
Ministry of Education, Culture and Sport with the scholarship FPU
13/00542. Moreover, funding from the Spanish Ministry of Economy,
Industry and Competitiveness has been used under the research and development
projects DPI2016-80641-R, DPI2016-80642-R and DPI2013-42853-R and from the Government of Navarre under the research and
development project "Integration of renewable energy in the electricity
grid by means of advance energy storage systems"., Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011), Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa (ED 99/2011)

In photovoltaic-battery systems, more attention is usually paid to the MPPT control while the battery management is put aside. This paper proposes two control strategies for an integrated PV-battery system, both of them making it possible to perform MPPT or regulate the battery voltage to its maximum value in order to prevent it from overcharging. Simulation results prove the feasibility of both controls., This work was supported by the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2013-42853-R and DPI2016-80641-R.

El aumento de penetración eólica producido a escala mundial está propiciando la conexión
de una gran cantidad de parques eólicos a redes débiles. Esto supone un reto para los
operadores de la red y de los propios parques eólicos, al surgir problemas de estabilidad que
anteriormente no existían. A la hora de afrontar los problemas derivados de la integración en
red de estos parques, resulta de gran importancia disponer de modelos precisos de la realidad.
Existen en la literatura modelos completos de parques y turbinas eólicas que permiten
detectar estos problemas con precisión razonable. Estos modelos, sin embargo, suelen ser
complejos y computacionalmente muy costosos, por lo que se utilizan más como un
instrumento de validación que de diseño. En la fase de diseño suelen emplearse modelos
lineales muy sencillos que permiten simular el sistema rápidamente y, por ende, realizar
grandes series de simulaciones para, por ejemplo, analizar un amplio rango de escenarios o
para optimizar los parámetros de control. Estos modelos, sin embargo, suelen adolecer de una
excesiva simplificación que provocan que, en muchas ocasiones, no reproduzcan con
suficiente precisión la dinámica o, lo que es peor, no permitan detectar casos de inestabilidad.
En este contexto, el objetivo de la tesis realizada es la obtención de modelos lineales
precisos de parques eólicos y, en particular, de lazos de control de corriente. Para ello, se han
abordado las siguientes líneas de trabajo: Recopilación de las principales opciones de modelización lineal de aerogeneradores y
redes eléctricas; Desarrollo de una metodología de modelización lineal que sea aplicable a una gran variedad de sistemas de generación renovable; Obtención de un modelo lineal que recoja de manera precisa el comportamiento y las
dinámicas más importantes de un convertidor conectado a una red débil; Modelización de parques eólicos de turbinas Full‐Converter (FC) y Doblemente Alimentadas (DFIG) conectados a una red débil., Esta tesis ha recibido financiación de la Agencia Española de Investigación (AEI) y el Fondo Europeo de Desarrollo Regional
(FEDER-UE) a través de los proyectos de investigación y
desarrollo DPI2013-42853-R y DPI2016-80641-R., Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011), Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa (ED 99/2011)

La energía eólica es una de las principales fuentes de generación renovable, una tecnología que continúa expandiéndose gracias a la reducción de costes y a la mayor concienciación ambiental de la sociedad. Esta expansión a nivel mundial está provocando que las turbinas eólicas se conecten a redes débiles, que plantean nuevos problemas de estabilidad. Asimismo, para continuar avanzando en la reducción del coste de la energía generada, la eficiencia de los sistemas de generación eólica, y consecuentemente del convertidor de potencia, se convierte en un aspecto clave. Por ultimo, existe una tendencia entre los principales fabricantes de aerogeneradores a incrementar el tamaño de las turbinas, aprovechando las economías de escala existentes. Esta tendencia está forzando a buscar nuevas estructuras de conversión para estas turbinas que alcanzan hoy en día los 9 MW. Dentro de este contexto general, en esta tesis se abordan las siguientes líneas de investigación:
- Modelo detallado de los lazos de control de un convertidor de conexión a red.
- Mejora de la respuesta din amica del convertidor.
- Mejora de la estabilidad y de la eficiencia de convertidores de conexión a red al amortiguar el filtro de salida mediante el control.
- Incremento de la eficiencia gracias a la utilización de modulaciones específicas para convertidores eólicos.
- Análisis de las estructuras de conversión para turbinas eólicas de gran potencia y extensión a estos sistemas de las técnicas anteriores., Wind power is one of the most extensive renewable energies, which continues to grow, powered by the cost reduction of the technology and a greater societal environmental awareness. This worldwide expansion brings new challenges, such as the connection of wind turbines to weak grids, raising new stability issues. In addition, the e ciency of wind energy conversion systems, and consequently, of the power converter, becomes a key aspect to keep reducing the cost of energy. The last challenge to be highlighted is the increase of the rated power of the agship wind turbines among the main manufacturers. This tendency is behind the interest of developing new conversion structures for modern wind turbines, which already reach 9 MW. In this general context, the general research lines are:
- Detailed modeling of the control loops of a grid connected power converter.
- Improvement of the converter's dynamic response.
- Enhancement of the stability and e ciency of grid-connected power converters by damping the output lter through control techniques.
- Increasing the system e ciency by using speci c modulations for power converters used in wind energy conversion systems.
- Analysis of the conversion structures for high power wind turbines and extension of the previous techniques to these systems., This thesis has been funded by the Public University of Navarre through a doctoral scholarship. The company Ingeteam Power Technology has supported this investigation under contracts OTRI 2016 024 004 and OTRI 2014 024 084. Moreover, the Spanish State Research Agency (AEI) and FEDER-UE have supported the investigation under grants DPI2013-42853-R and DPI2016-80641-R., Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011), Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa (ED 99/2011)

This paper presents the design of a low complexity fuzzy logic controller of only 25-rules to be embedded in an energy management system for a residential grid-connected microgrid including renewable energy sources and storage capability. The system assumes that neither the renewable generation nor the load demand is controllable. The main goal of the design is to minimize the grid power profile fluctuations while keeping the battery state of charge within secure limits. Instead of using forecasting-based methods, the proposed approach use both the microgrid energy rate-of-change and the battery state of charge to increase, decrease, or maintain the power delivered/absorbed by the mains. The controller design parameters (membership functions and rule-base) are adjusted to optimize a pre-defined set of quality criteria of the microgrid behavior. A comparison with other proposals seeking the same goal is presented at simulation level, whereas the features of the proposed design are experimentally tested on a real residential microgrid implemented at the Public University of Navarre., This work was supported in part by the Secretaría Nacional de Educación Superior, Ciencia, Tecnología e Innovación SENESCYT and the Instituto de Fomento al Talento Humano del Ecuador under Grant 2013-AR2Q4081; in part by the Government of Navarra and the European Regional Development Fund under the Microgrids in Navarra: Design, Development, and Implementation Project; in part by the Spanish Ministry of Economy and Competitiveness under Grant DPI2013-42853-R; in part by the European Union under Project FP7-308468; in part by PVCROPS—Photovoltaic Cost Reduction, Reliability, Operational Performance, Prediction, and Simulation under Grant RUE CSD2009-00046; in part by the Consolider-Ingenio 2010 Programme; in part by the Spanish Ministry of Science and Innovation; and in part by the Spanish Ministry of Economy and Knowledge under Grant DPI2013-41224-P and Grant DPI2012-31580. Paper no. TSG-00712-2015.

The droop method is an advantageous technique for stand-alone AC supply systems, allowing for power sharing among various inverters with no need for communication cables. However, in stand-alone systems with multiple distributed energy storage units, the conventional droop methods are unable to control the storage unit state-of-charge (SOC) in order to change simultaneously. Existing techniques endeavor to solve this problem by changing the slope of the P – f curve however this solution compromises the power response performance. As an alternative, this paper proposes a new SOC-based droop control, whereby the P – f curve is shifted either upwards or downwards according to the battery SOC. The proposed technique makes it possible to select the time constant for the battery SOC convergence and, at the same time, to optimize the power response performance. The paper also shows how the SOC changes when the ratios between the battery capacity and the inverter rated power are different and how the proposed technique can limit the SOC imbalance. Simulation and experimental results corroborate the theoretical analysis., This work was supported in part by the Spanish Ministry of
Economy and Competitiveness under Grant DPI2013-42853-R,
and by the Public University of Navarre through a doctoral
scholarship.

Parallel interleaved converters for high power renewable energy systems present stability issues at the LCL resonance frequency. A multisampled measurement and filtering strategy is proposed to stabilize the system based on the capacitor voltage derivative active damping, overcoming its limitations for low switching power converters. The effects of the delays on the stability of the active damping strategy would be analysed. The solution developed is robust against grid inductance variations, ensuring the fulfilment of the stringent harmonic grid codes., The authors gratefully acknowledge Ingeteam Power Technology and the Spanish Ministry of Economy and Competitiveness under grant DPI2013-42853-R and DPI2016-80641-R for its financial and ongoing support. This work was partially funded by the Public University of Navarre through a doctoral scholarship.

Incluye póster., One of the most typical distributed generation systems are electrical microgrid, which consist on small electrical
grids, generally connected to the main grid, with a decentralized management structure. Electrical microgrids allow
higher renewable energy integration in the grid, achieving a cost decrease and improving the grid quality [1]. These mi-
crogrids incorporate renewable generation systems and energy consumers. Moreover, they have storage systems to
balance generation and consumption as well as the exchanged power with the main grid. Traditionally, lead-acid batter-
ies have been used in microgrids. However, these batteries have some drawbacks, being the most important its poor
performance in partial state of charge, which is critical for a microgrid. A suitable option for the storage system is hy-
drogen technology. These systems have high energy density, which makes the storage system able to assume seasonal
variability of renewable resources.
This paper proposes a sizing methodology for storage systems based on hydrogen for grid-tied electrical microgrids.
This methodology optimizes the relationship between the storage system size and the consumption of grid power., Spanish Ministry of Economy and Competitiveness under grant DPI2013-42853-R; 2015 Annual Grants for Research and Development of Fundación Bancaria Caja Navarra (supporting project 70276); FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

La energía fotovoltaica ha experimentado un gran crecimiento en el mundo en los ultimos años, motivado principalmente por el descenso de su
precio durante la ultima década. Esta reducción de costes ha hecho que se
convierta en una tecnología de generación eléctrica muy atractiva en países en desarrollo, donde la demanda eléctrica es cada vez mayor, y en sistemas
insulares, en los que permite mejorar la independencia energética de los mismos. El sistema eléctrico de potencia en esos lugares está muy poco mallado
en comparación con los lugares en los que habitualmente se situaban las plantas fotovoltaicas, por lo que presentan una impedancia de red mucho mayor que
lo habitual. Esto, unido al tamaño cada vez mayor de las plantas instaladas, hace que el ratio de la potencia de cortocircuito (SCR) disminuya hasta valores
cercanos a la unidad. En este nuevo escenario, la integración de inversores fotovoltaicos plantea nuevos problemas relacionados con la estabilidad de los
lazos de control.
Dentro de este contexto, en esta tesis se abordan las siguientes líneas de investigación:
Modelo el lazo de control de corriente, incluyendo la PLL utilizada para
sincronizarse con la red; Estudio del efecto de la impedancia de red en la estabilidad del lazo de
control; Mejora de la estabilidad del lazo de control de corriente en redes débiles; Mejora de la estabilidad de la PLL en redes débiles; Análisis de las técnicas de control basadas en la emulación del generador síncrono y aplicación al caso de redes débiles., Esta tesis ha sido subvencionada por el programa de Formación de
Personal Investigador (FPI) de la Universidad Pública de Navarra, a
través de una beca predoctoral. Además, se ha recibido financiación de la
Agencia Española de Investigación (AEI) y el Fondo Europeo de Desarrollo
Regional (FEDER-UE) a través de los proyectos de investigación y
desarrollo DPI2013-42853-R y DPI2016-80641-R., Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011), Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa (ED 99/2011)

In the last quarter of a century, high-frequency
(HF) transformer design has been one of the major concerns to power electronics designers in order to increase
converter power densities and efficiencies. Conventional
design methodologies are based on iterative processes
and rules of thumb founded more on expertise than on
theoretical developments. This paper presents an analytical design methodology for litz-wired HF power transformers that provides a deep insight into the transformer
design problem making it a powerful tool for converter
designers. The most suitable models for the calculation
of core and winding losses and the transformer thermal
resistance are first selected and then validated with a
5-kW 50-kHz commercial transformer for a photovoltaic
application. Based on these models, the design methodology is finally proposed, reducing the design issue to
directly solve a five-variable nonlinear optimization problem. The methodology is illustrated with a detailed design in terms of magnetic material, core geometry, and
primary and secondary litz-wire sizing. The optimal design
achieves a 46.5% power density increase and a higher
efficiency of 99.70% when compared with the commercial one., This work was supported in part by the Spanish Ministry of Economy and Competitiveness under Grant DPI2010-21671-C02-01 and Grant DPI2013-42853-R, in part by the
Public University of Navarra, and in part by Ingeteam Power Technology.

The growing interest in e-mobility and the increasing installation of renewable energy-based systems are leading to rapid improvements in lithium-ion batteries. In this context, battery manufacturers and engineers require advanced models in order to study battery performance accurately. A number of Li-ion battery models are based on the representation of physical phenomena by electrochemical equations. Although providing detailed physics-based information, these models cannot take into account all the phenomena for a whole battery, given the high complexity of the equations. Other models are based on equivalent circuits and are easier to design and use. However, they fail to relate these circuit parameters to physical properties. In order to take the best of both modeling techniques, we propose an equivalent circuit model which keeps a straight correlation between its parameters and the battery electrochemical principles. Consequently, this model has the required simplicity to be used in the simulation of a whole battery, while providing the depth of detail needed to identify physical phenomena. Moreover, due to its high accuracy, it can be used in a wide range of environments, as shown in the experimental validations carried out in the final section of this paper., The authors acknowledge the support of the Spanish State Research Agency (AEI) and FEDER UE under grants DPI2013 42853 R, DPI2016 80641 R and DPI2016 80642 R; of Government of Navarra through research project PI038 INTEGRA-RENOVABLES; and the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

The use of LC and LCL filters and grid impedance variations are creating new challenges on the controller design for current control loops of photovoltaic and wind turbine inverters. In the design process, stability criteria such as Bode and revised Bode are commonly used. This paper analyses the limitations of Bode and revised Bode criteria to reliably determine stability and proposes a sufficient and necessary stability criterion, based on the Nyquist criterion, but that makes use of the Bode diagram. The proposed criterion, named generalized Bode criterion, is always reliable and helps the controller design. Relative stability in complex control loops is also studied and a relative stability analysis is proposed. Finally, the generalized Bode criterion and the proposed relative stability analysis are illustrated with a practical example in which a PI is designed in order to guarantee stability and achieve relative stability., This work has been supported by the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2013-42853-R, DPI2016-80641-R and by the company Ingeteam Power Technology.

Over the last few years, the considerable increase in the number of multi-MW PV plants has led transmission system operators (TSO) to express concern over potential PV power fluctuations caused by transient clouds. As a result, new grid codes are being issued in order to include new criteria which make it easier for the TSO to react appropriately to harmful short-term power fluctuations. It si precisely these new regulations the origin of this thesis, which is a pioneering study attempting to face with this situation. Herein, the main results in order to smooth out these fluctuations and comply with the regulations are presented., This thesis has been partially financed by the Seventh Framework Programme of the
European Commission with the project PVCROPS (Photovoltaic Cost R€duction,
Reliability, Operational Performance, Prediction and Simulation – Grant Agreement no:
308468) and by the Spanish Ministry of Economy and Competitiveness under Grant
DPI2013-42853-R.

Lithium-ion batteries are gaining importance for a variety of applications due to their improving characteristics and decreasing price. An accurate knowledge of their aging is required for a successful use of these ESSs. The vast number of models that has been proposed to predict these phenomena raise doubts about the suitability of a model for a particular battery application. The performance of three models published for a Sanyo 18650 cylindrical cell in a self-consumption system are compared in this work. Measured photovoltaic production and home consumption with a sampling frequency of 15 minutes are used for this comparison. The different aging predictions calculated by these three models are analyzed, compared and discussed. These comparison is particularized for two management strategies. The first of them maximizes the self-consumption PV energy, while the second reduces the maximum power peak demanded from the grid., The authors would like to acknowledge the support of the Spanish State Research Agency (AEI) and FEDER-UE under grants DPI2013-42853-R, DPI2016-80641-R and DPI2016-80642-R; of Government of Navarra through research project PI038 INTEGRA-RENOVABLES; and the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

An accurate monitoring of the State of Charge (SoC) is mandatory for an efficient management of a Lithium-ion battery. Batteries of stationary systems barely have long resting periods when the cumulative errors can be reset. These special requirements make a robust and accurate SoC estimation algorithm necessary. A real stationary system including an experimental microgrid with renewable energy generation, home consumption and a 5.3 kWh Li-ion storage system is analyzed in this paper. Three representative SoC monitoring algorithms are applied and compared in terms of accuracy and robustness to battery aging and current measurement offset. A closed-loop method consisting of an adaptive filter and a state observer achieves best results while having a reasonable computational complexity., Spanish Ministry of Economy and Competitiveness under grant DPI2013-42853-R, FPU Program of the Spanish Ministry of Education, Culture and Sport (FPUI3/00542) and 2015 Annual Grants for Research and Development of Fundación Bancaria Caja Navarra (supporting project 70276).

Incluye póster, In this paper, we present APERNA, a recently-created student association at Public University of Navarre (UPNA) with the aim of promotion of renewable energies., The authors would like to acknowledge the support of the Spanish Ministry of Economy and Competitiveness under grant DPI2013-42853-R, the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542) and the 2015 Annual Grants for Research and Development of Fundación Bancaria Caja Navarra (supporting project 70276).

This paper presents the design of an energy management strategy based on a low complexity Fuzzy Logic Control (FLC) for grid power profile smoothing of a residential grid-connected microgrid including Renewable Energy Sources (RES) and battery Energy Storage System (ESS). The proposed energy management strategy uses generation and demand forecasting to anticipate the future behavior of the microgrid. Accordingly to the microgrid power forecast error and the Battery State-of-Charge (SOC) the proposed strategy performs the suitable control of the grid power. A simulation comparison with previous energy management strategies highlights the advantages of the proposed work minimizing fluctuations and power peaks in the power profile exchanged with the grid while keeping the energy stored in the battery between secure limits. Finally, the experimental validation in a real residential microgrid implemented at Public University of Navarre (UPNA, Spain) demonstrates the proper operation of the proposed strategy achieving a smooth grid power profile and a battery SOC center close to the 75% of the rated battery capacity., This work is part of the project 2016-PIC-044 from the Universidad de las Fuerzas Armadas ESPE. This work was partially supported by the Spanish State Research Agency (AEI) and FEDER-UE under grants: DPI2015-67292, DPI2013-41224-P, DPI2013-42853-R and DPI2016-80641-R.

This paper proposes a methodology for sizing stand-alone hybrid photovoltaic-wind power generation systems. This methodology makes it possible to optimise the overall performance of the stand-alone system components, based on the premise of guaranteeing the power supply throughout the useful life of the installation at a minimum cost. The sizing is performed in two stages. Firstly, the components of the wind and photovoltaic power generation subsystem are obtained and, secondly, the size of the storage subsystem is determined. For the storage subsystem sizing, account is taken of the variation in efficiency according to the operating point and also the deterioration of the subsystem due to aging and, therefore, the loss of available energy during the useful life of the installation. This methodology is applied to a stand-alone traffic control system located on a secondary road in the Autonomous Community of Valencia (Spain). This system comprises wind and photovoltaic power generation components, a lithium battery bank and various traffic management components. Finally, an analysis of the proposed sizing is made. Satisfactory results are obtained, showing how the proposed methodology makes it possible to optimise the sizing of stand-alone systems with regard to the size of its components, cost and operation., This work has been supported by the Spanish State Research Agency (AEI) and FEDER-UE under grant DPI2013-42853-R, DPI2016-80642-R and DPI2016-80641-R; and by the Government of Navarre under project PIO38 INTEGRA-RENOVABLES.

Póster presentado a la 33rd European Photovoltaic Solar Energy Conference and Exhibition. Amsterdam (Países Bajos), 2017., The properly in-field characterization of the power at Standard Test Conditions, PSTC, of PV generators is becoming increasingly important in order to evaluate their performance and its evolution in time. Within the state of art, the PSTC characterization procedures of PV arrays are mainly based on I-V curve measurements or PDC measurements performed by precision wattmeters. Those characterizations are usually carried out during discrete measurement campaigns, which does not allow a continuous tracking of the PSTC evolution. In this paper a new PSTC characterization procedure is proposed which is based on the DC power measurements performed by the own PV inverters connected to the PV arrays. This procedure enables an automatic and continuous calculation of the PSTC, which allows to observe its evolution and to detect possible anomalous trends, premature degradations, etc. The procedure has been validated in several PV generators of the large-scale Amareleja PV Plant (45.6 MWp). As showed in this paper, by using several day data and applying the adequate filters, a high accuracy in the PSTC calculation can be achieved, a similar accuracy to that obtained by using precision wattmeter measurements., This work has been partially financed by the Seventh Framework Programme of the European Commission with the project PVCROPS (Photovoltaic Cost Reduction, Reliability, Operational Performance, Prediction and Simulation – Grant Agreement no: 308468) and by the Spanish Ministry of Economy and Competitiveness under Grant DPI2013-42853-R.

Póster presentado a la 31st European Photovoltaic Solar Energy Conference and Exhibition. Hamburgo (Alemania), 2015., Nowadays, accurate AC power output forecast of PV plants can play a significant role for both the system operators and PV plant owners. The first group has to program the dispatch of the electric system and the second one needs to plan their energy commercialization schedule up front. Therefore, after analyzing the existing commercial services of PV production forecast, it has been identified the potential to improve the models used to calculate the AC power output from irradiance and ambient temperature forecasts. Then, in this paper, a parametric model is proposed in order to improve the forecast performance. This model provides the AC power at the output of the PV plan using as input variables predicted ambient temperature and predicted global horizontal irradiance, both obtained from open sources. It has been evaluated and validated using historical production data of a fixed generator (2,24kWp) and a large PV power plant (45MWp) and historical forecast data from the open source Meteogalicia In addition, a toolbox to implement this parametric methodology has been built upon the Matlab environment. The toolbox has been developed to provide the PV plant production one day in advance., This work has been partially financed by the Seventh Framework Programme of the European Commission with the project PVCROPS (Photovoltaic Cost Reduction, Reliability, Operational Performance, Prediction and Simulation – Grant Agreement no: 308468) and by the Spanish Ministry of Economy and Competitiveness under Grant DPI2013-42853-R.

Grid-connected pulse-width modulation converters with LCL filters are widely extended as an interface for renewable energy generating systems. Those filters arise stability issues due to the filter resonance, which, must be damped, preferably by active damping methods, to avoid additional power losses. In some applications, such as offshore wind energy conversion systems, where high power converters are connected to low voltage networks, the commutation frequency is limited to low values to reduce the power losses and the resulting filter components are bulky. For this reason, in addition to its higher current handling capabilities, the use of power converters in parallel with the application of advanced modulation strategies, such as interleaving, is gaining importance. In this structure the filter components can be reduced, setting the filter resonance frequency at a higher value. As a consequence, the filter resonance frequency is close to the Nyquist frequency, complicating the implementation of some of the existing active damping solutions. In this work, an active damping approach based on a third order digital filter is proposed to stabilize the system. The robustness of the solution is investigated against grid inductance variations and the grid current harmonic content will be tested to comply with the most demanding grid codes. The proposed active damping strategy does not require extra sensors and can be easily designed by examining the open loop Bode plots. It is suitable to stabilize the LCL filter with a resonance frequency close to the Nyquist frequency, where some of the existing active damping approaches are unable to damp the system. The proposed method can be also an appropriate solution for existing grid connected power converters with stability issues due to changes in the effective grid impedance at which they are connected., The authors gratefully acknowledge Ingeteam Power Technology and the Spanish Ministry of Economy and Competitiveness under grant DPI2013-42853-R for its financial and ongoing support. This work was partially funded by the Public University of Navarre through a doctoral scholarship.

Distributed generation is an attractive solution for stand-alone AC supply systems. In such systems, the installation of two or more energy-storage units is recommended for system redundancy and may also be required when there is a consumption increase following installation. However, energy management with multiple energy-storage units has been but vaguely analyzed in the literature and the few studies made are based on communication cables with a central supervisor. This paper proposes an energy management strategy for a multiple-battery system which makes it possible to avoid the use of communication cables, rendering the system more cost-effective and reliable. The strategy modifies the conventional droop method so that the power becomes unbalanced, allowing for the regulation of one or more battery voltages or currents, as required. Furthermore, whenever the frequency is high, the PV inverters reduce their power in order to prevent the battery from overcharge or high charging currents. On the other hand, whenever the frequency is low, then either the non-critical loads are regulated or the system stops in order to prevent the battery from over-discharge or high discharging currents. Simulation and experimental validation are performed for a system with two battery inverters, two PV inverters and a number of loads., This work was supported in part by the Spanish Ministry of Economy and Competitiveness under Grant DPI2013-42853-R, and by the Public University of Navarre through a doctoral scholarship.