Modeling and control of stand-alone AC microgrids: centralized and distributed storage, energy management and distributed photovoltaic and wind generation

El aumento de la penetración de energías renovables en la red eléctrica es necesario para el desarrollo de un sistema sostenible. Para hacerlo posible técnicamente, se ha planteado el uso de microrredes, definidas como una combinación de cargas, generadores distribuidos y elementos de almacenamiento controlados gracias a una estrategia global de gestión energética. Además, las microrredes aumentan la fiabilidad del sistema puesto que pueden funcionar en modo aislado en caso de fallo de red. Esta tesis se centra en el desarrollo de microrredes AC en funcionamiento aislado. El objetivo principal es el diseño y la implementación de estrategias de gestión energéticas sin utilizar cables de comunicación entre los distintos elementos, lo que permite reducir los costes del sistema y aumentar su fiabilidad. Para ello, se abordan los siguientes aspectos: • Gestión energética de una microrred AC con generador diesel, almacenamiento centralizado y generación renovable distribuida • Diseño de técnicas de control “droop” para repartir la corriente entre inversores conectados en paralelo • Gestión energética de una microrred AC con almacenamiento distribuido y generación renovable distribuida • Control de la etapa DC/DC de inversores fotovoltaicos con pequeño condensador de entrada en el seno de una microrred • Control de extracción de máxima potencia sin sensores mecánicos para sistemas minieólicos en el seno de una microrred.The introduction of distributed renewable generators into the electrical grid is required for a sustainable system. In order to increase the penetration of renewable energies, microgrids are usually proposed as one of the most promising technologies. A microgrid is a combination of loads, distributed generators and storage elements which behaves as a single controllable unit for the grid operator. Furthermore, microgrids make it possible to improve the system reliability because they are capable of standalone operation in case of grid failure. This thesis is focused on the development of AC microgrids under stand-alone operation. Its main objective is to design and implement overall control strategies which do not require the use of communication cables, thereby reducing costs and improving reliability. For this purpose, the following aspects are tackled: • Energy management of an AC microgrid with diesel generator, centralized storage and distributed renewable generation • Design of droop methods so that the current is shared among parallel-connected inverters • Energy management of an AC microgrid with distributed storage and distributed renewable generation • Control of the DC/DC stage in photovoltaic inverters with small input capacitors within a microgrid • Sensorless MPPT control for small wind turbines within a microgrid.Programa Oficial de Doctorado en Energías Renovables (RD 1393/2007)Energia Berriztagarrietako Doktoretza Programa Ofiziala (ED 1393/2007

Dual-mode soft-transition control for single-phase grid-connected photovoltaic inverters

Póster presentado al 19th IEEE Workshop on Control and Modeling for Power Electronics COMPEL). Padua (Italia), 2018.Single-phase grid-connected inverters for photovoltaic power generation have been strongly analysed for improvement. Dual-mode control for two-stage inverters makes it possible to improve the efficiency by alternating between switching the dc/dc boost and the dc/ac buck stages, depending on the grid voltage value. However, according to the literature, the transition from one mode to the other is abrupt, which harms the grid current quality. This paper proposes a dual-mode control method which achieves high efficiency and a soft-transition in the grid current. Applying suitable feed-forward compensations, this control method improves the grid current quality, as demonstrated by the presented simulation results.Spanish State Research Agency (AEI) and FEDER-UE under grant DPI2016-80641-

Analysis of the multiple sclerosis susceptibility gene IL22RA2

347 p.Multiple sclerosis (MS) is a chronic inflammatory neurological disease whose underlying cause remains uncertain and can be influenced by different environmental and genetic factors. We have studied two MS-susceptibility genes, IL22RA2 and IL12A, to better understand their regulation and relationship to MS. We demonstrated that the IL22RA2 gene gives rise to three isoforms in monocyte-derived dendritic cells (moDCs).. We also found that CD14++/CD16+ intermediate monocytes produced higher levels of IL22RA2 mRNA than classical and non-classical monocytes. Using transfected human cell lines, we demonstrated that the protein product of IL22RA2 variant 1 (IL22RA2v1), the IL-22BP isoform 1 (IL-22BPi1), was poorly secreted and largely retained in the endoplasmic reticulum (ER). We performed interactome analysis to uncover the mechanism underlying the ER retention of IL-22BPi1 and identified ER chaperones GRP78, GRP94, GRP170 and calnexin as main interactors. Structure-function analysis revealed that, like IL-22BPi2, IL-22BPi1 binds to the substrate-binding domain of GRP78 as well as to the middle domain of GRP94, and thus, we have demonstrated the domain of interaction of IL-22BPi1 and IL-22BPi2 with GRP78 and GRP94. Upon silencing of IL22RA2 expression in moDC, GRP78 levels were significantly reduced, suggesting that native IL22RA2 expression naturally contributes to upregulated GRP78 levels in these cells. Finally, we demonstrated that another variant apart from the canonical IL12A was expressed in moDCs and in different immune and epithelial cells lines. Altogether, our work highlights the relevance of the study of splicing variants of MS susceptibility genes for a better understanding of the effect of the genetic factors in the disease

Effect of the inner current loop on the voltage regulation for three-phase photovoltaic inverters

In three-phase grid-connected PV inverters, regulating the input voltage is a fundamental requirement. In order to reduce the influence of the PV non-linear behavior and ensure stability in the whole operating range, the input capacitance is currently oversized. This paper reveals the important effect of the inner current loop in the voltage stability and proposes to use a Proportional (P) controller instead of a PI controller. If tuned following the guidelines provided in this paper, the P controller makes it possible to design a stable voltage loop without increasing the input capacitance, thus reducing the converter cost.This work was supported by the Spanish State Research Agency (AEI) under grant PID2019-110956RB-I00/AEI/10.13039 and grant DPI-201680641-R

Single feedback regulation of the AC voltage for high-power inverters under stand-alone operation

Energy-storage inverters under stand-alone operation must control the output voltage. However, existing methods for instantaneous voltage regulation are not suitable for high-power inverters due to their limited sampling frequency. To avoid this problem, a single feedback voltage loop with feedforward compensation is proposed in this paper, making it possible to actively damp the LCL filter resonance and thus facilitating the controller design. Simulation results demonstrate the fast reference tracking and the high-quality voltage obtained with non-linear loads.This work was supported by the Spanish State Research Agency (AEI) and FEDER-UE under grant DPI2016-80641-R and by the Public University of Navarre through a doctoral scholarship. The authors acknowledge the financial and continuous support of Ingeteam Power Technology

Parameter-independent battery control based on series and parallel impedance emulation

Appropriate voltage control is essential in order to extend the useful life of a battery. However, when universal chargers are used, the design of this control becomes more complicated, given the fact that the battery impedance value may vary considerably, depending not only on the operating point but also on the type, size and aging level of the battery. This paper firstly shows how the voltage regulation can become extremely variable or even unstable when the controller is designed according to the proposals in the literature. We then go on to propose the emulation of a series and parallel impedance with the battery, which is easy to implement and achieves a control that is completely independent of the battery connected. The simulation results obtained for batteries with resistances ranging from 10 mO to 1 O, show the problems with existing controls and confirm that the proposed control response is similar for all the possible range of battery resistances.Peer ReviewedPostprint (published version