• Energy Research

Sensorless control of Electric Vehicle (EV) drives is considered to be an effective approach to improve system reliability and to reduce component costs. In this paper, relevant aspects relating to the sensorless operation of EVs are reported. As an initial contribution, a hybrid sensorless control algorithm is presented that is suitable for a variety of synchronous machines. The proposed method is simple to implement and its relatively low computational cost is a desirable feature for automotive microprocessors with limited computational capabilities. An experimental validation of the proposal is performed on a full-scale automotive grade platform housing a 51¿kW Permanent Magnet assisted Synchronous Reluctance Machine (PM-assisted SynRM). Due to the operational requirements of EVs, both the strategy presented in this paper and other hybrid sensorless control strategies rely on High Frequency Injection (HFI) techniques, to determine the rotor position at standstill and at low speeds. The introduction of additional high frequency perturbations increases the power losses, thereby reducing the overall efficiency of the drive. Hence, a second contribution of this work is a simulation platform for the characterization of power losses in both synchronous machines and a Voltage Source Inverters (VSI). Finally, as a third contribution and considering the central concerns of efficiency and autonomy in EV applications, the impact of power losses are analyzed. The operational requirements of High Frequency Injection (HFI) are experimentally obtained and, using state-of-the-art digital simulation, a detailed loss analysis is performed during real automotive driving cycles. Based on the results, practical considerations are presented in the conclusions relating to EV sensorless control. Peer Reviewed

Abstract The wave energy is having more and more interest and support as a promising renewable resource to replace part of the energy supply, although it is still immature compared to other renewable technologies. This work presents a complete analysis of the wave energy technology, starting with the characterisation of this global resource in which the most suitable places to be exploited are showed, and the classification of the different types of wave energy converters in according to several features. It is also described in detail each of the stages that are part in the energy conversion, that is, from the capture of the energy from the waves to the extraction of a proper electrical signal to be injected to the grid. Likewise, existing offshore energy transmission alternatives and possible layouts are described.

The oceans represent a huge energy reservoir. Although today all of the marine power projects are very near from the shore and they are rated at low power, the huge potential of the seas may in a not very distant future bring marine power further into the sea. Also offshore oil and gas exploration is moving into deeper waters and at longer distances from land. New carbon sequestration projects under the seabed are on the way which require a vast amount of electric power consumption. The substitution of offshore power generators by power provided from the grid may have environmental benefits, but the deployment of offshore transmission of bulk electrical power to or from offshore platforms to the electrical grid onshore is a mayor challenge. The main objective of this paper is to focus on trends that can lead to a feasible transmission system in offshore energy systems far from land, and to introduce the technological alternatives which could help to reach that goal. The paper describes the main alternatives and the technical and economical aspects of the transmission of electrical power offshore.

DC nanogrid architectures with Photovoltaic (PV) modules are expected to grow significantly in the next decades. Therefore, the integration of multi-port power converters and high-frequency isolation links are of increasing interest. The Triple Active Bridge (TAB) topology shows interesting advantages in terms of isolation, Zero Voltage Switching (ZVS) over wide load and input voltage ranges and high frequency operation capability. Thus, controlling PV modules is not an easy task due to the complexity and control stability of the system. In fact, the TAB power transfer function has many degrees of freedom, and the relationship between any of two ports is always dependent on the third one. In this paper we analyze the interfacing of photovoltaic arrays to the TAB with different solar conditions. A simple but effective control solution is proposed, which can be implemented through general purpose microcontrollers. The TAB is applied to an islanded DC nanogrid, which can be useful and readily implemented in locations where the utility grid is not available or reliable, and applications where isolation is required as for example More Electric Aircraft (MEA). Different conditions have been simulated and the control loops are proved for a reliable bus voltage control on the load side and a good maximum power point tracking (MPPT).

Economical optimization of hybrid systems is usually performed by means of LCoE (levelized cost of energy) calculation. Previous works deal with the LCoE calculation of the whole hybrid system disregarding an important issue: the stochastic component of the system units must be jointly considered. This paper deals with this issue and proposes a new fast optimal policy that properly calculates the LCoE of a hybrid system and finds the lowest LCoE. This proposed policy also considers the implied competition among power sources when variability of gas and electricity prices are taken into account. Additionally, it presents a comparative between the LCoE of the hybrid system and its individual technologies of generation by means of a fast and robust algorithm based on vector logical computation. Numerical case analyses based on realistic data are presented that valuate the contribution of technologies in a hybrid power system to the joint LCoE This work has been carried out inside the Research and Education Unit UFI11/16 of the UPV/EHU and supported by the Department of Education, Universities and Research of the Basque Government within the fund for research groups of the Basque university system through: IT394-10, IE14-389 and DPI2014-53685-C2-2-R.

In recent decades, several factors such as environmental protection, fossil fuel scarcity, climate change and pollution have driven the research and development of a more clean and sustainable transport. In this context, several agencies and associations, such as the European Union H2020, the United States Council for Automotive Research (USCAR) and the United Nations Economic and Social Commission for Asia (UN ESCAP) have defined a set of quantitative and qualitative goals in terms of efficiency, reliability, power losses, power density and economical costs to be met by next generation hybrid and full electric vehicle (HEV/EV) drive systems. As a consequence, the automotive electric drives (which consists of the electric machine, power converter and their cooling systems) of future vehicles have to overcome a number of technological challenges in order to comply with the aforementioned technical objectives. In this context, this paper presents, for each component of the electric drive, a comprehensive review of the state of the art, current technologies, future trends and enabling technologies that will make possible next generation HEV/EVs. This work has been partially supported by the Department of Education, Linguistic Policy and Culture of the Basque Government within the fund for research groups of the Basque university system IT978-16, by the Ministerio de Economía y Competitividad of Spain within the project DPI2014-53685-C2-2-R and FEDER funds and by the Government of the Basque Country within the research program ELKARTEK as the project KT4TRANS (KK-2015/00047 and KK-2016/00061), as well as by the program to support the specialization of Ph.D researchers at UPV/EHU ESPDOC16/25.

Un nouveau contrôleur prédictif basé sur un modèle (MPC), spécialement orienté pour faciliter sa mise en œuvre pratique, est présenté. Ce contrôleur est dédié à la réduction de la charge structurelle dans le groupe motopropulseur et/ou le rotor d'une éolienne. Il maintient sa complexité et sa charge de calcul faibles, en utilisant un seul modèle interne linéaire sur toute la gamme d'utilisation. Pour valider la nouvelle approche, les performances de deux versions d'un tel contrôleur sont comparées au cas de référence. Plus précisément, les contrôleurs mis en œuvre se concentrent sur l'atténuation des vibrations de torsion qui apparaissent dans la transmission pendant le fonctionnement de la turbine pour des vitesses de vent supérieures à la vitesse nominale. Tout d'abord, des simulations numériques sont utilisées pour étudier la performance potentielle. Ensuite, la méthodologie proposée est mise en pratique en utilisant des prototypes rapides des contrôleurs en temps réel appliqués à un simulateur Hardware-in-the-Loop (HiL) spécialement conçu pour les éoliennes. Ce simulateur HiL reproduit de manière réaliste les performances de l'éolienne de 5 MW du National Renewable Energy Laboratory (NREL). Afin de confirmer l'applicabilité pratique de tels algorithmes MPC, la plate-forme électronique montée sur le système de prototypage rapide a une puissance de calcul similaire - ou inférieure - aux plates-formes de contrôle industrielles utilisées dans les éoliennes réelles. Quoi qu'il en soit, la charge de calcul est analysée en détail. Se presenta un nuevo controlador predictivo basado en modelos (MPC), especialmente orientado a facilitar su implementación práctica. Este controlador está dedicado a reducir la carga estructural en el tren de transmisión y/o el rotor de un aerogenerador. Mantiene su complejidad y carga computacional bajas, mediante el uso de un único modelo interno lineal en toda la gama de uso. Para validar el nuevo enfoque, se compara el rendimiento de dos versiones de dicho controlador con el caso de referencia. Específicamente, los controladores implementados se centran en mitigar las vibraciones torsionales que aparecen en el tren de transmisión durante el funcionamiento de la turbina para velocidades de viento superiores a las nominales. En primer lugar, se utilizan simulaciones numéricas para estudiar el rendimiento potencial. Luego, la metodología propuesta se pone en práctica mediante el uso de prototipos rápidos de los controladores en tiempo real aplicados a un simulador de Hardware-in-the-Loop (HiL) de aerogeneradores diseñado específicamente. Este simulador HiL reproduce de forma realista el rendimiento del aerogenerador de 5 MW del Laboratorio Nacional de Energías Renovables (NREL). Para confirmar la aplicabilidad práctica de dichos algoritmos MPC, la plataforma electrónica montada en el sistema de prototipado rápido tiene una potencia computacional similar o inferior a las plataformas de control industrial utilizadas en los aerogeneradores reales. De todos modos, la carga computacional se analiza en detalle. A new model-based predictive controller (MPC), specially oriented to facilitate its practical implementation, is presented. This controller is devoted to reduce the structural load in the drive train or/and the rotor of a wind turbine. It keeps its complexity and computational load low, by using a single linear internal model throughout the full range of use. To validate the new approach, the performance of two versions of such a controller is compared to the baseline case. Specifically, the implemented controllers are focused on mitigating the torsional vibrations that appear in the drive-train during turbine operation for wind speeds above rated. First, numerical simulations are used to study the potential performance. Then, the proposed methodology is put into practice by using rapid prototypes of the real-time controllers applied to a specifically designed Hardware-in-the-Loop (HiL) simulator of wind turbines. This HiL simulator realistically reproduces the performance of the National Renewable Energy Laboratory (NREL) 5 MW wind turbine. In order to confirm the practical applicability of such MPC algorithms, the electronic platform mounted on the rapid-prototyping system has a similar -or inferior- computational power than the industrial control platforms used in the actual wind turbines. Anyway, the computational burden is analyzed in detail. يتم تقديم وحدة تحكم تنبؤية جديدة قائمة على النموذج (MPC)، موجهة خصيصًا لتسهيل تنفيذها العملي. تم تخصيص وحدة التحكم هذه لتقليل الحمل الهيكلي في مجموعة الدفع و/أو دوار توربين الرياح. يحافظ على تعقيده وحمله الحسابي منخفضين، باستخدام نموذج داخلي خطي واحد في جميع أنحاء النطاق الكامل للاستخدام. للتحقق من صحة النهج الجديد، تتم مقارنة أداء نسختين من وحدة التحكم هذه بالحالة الأساسية. على وجه التحديد، تركز وحدات التحكم المنفذة على التخفيف من الاهتزازات الالتوائية التي تظهر في مجموعة الدفع أثناء تشغيل التوربين لسرعات الرياح أعلى من التصنيف. أولاً، يتم استخدام المحاكاة العددية لدراسة الأداء المحتمل. بعد ذلك، يتم وضع المنهجية المقترحة موضع التنفيذ باستخدام نماذج أولية سريعة لوحدات التحكم في الوقت الفعلي المطبقة على محاكي الأجهزة في الحلقة (HiL) المصمم خصيصًا لتوربينات الرياح. يقوم جهاز محاكاة HiL هذا بإعادة إنتاج أداء توربينات الرياح من المختبر الوطني للطاقة المتجددة (NREL) بقدرة 5 ميجاوات بشكل واقعي. من أجل تأكيد التطبيق العملي لخوارزميات MPC هذه، فإن المنصة الإلكترونية المثبتة على نظام النماذج الأولية السريعة لديها قوة حسابية مماثلة - أو أقل - من منصات التحكم الصناعية المستخدمة في توربينات الرياح الفعلية. على أي حال، يتم تحليل العبء الحسابي بالتفصيل.

Distributed generation is emerging as a new technology for supplying the increasing demand for electricity. Microgrids are attracting a great deal of attention since they integrate distributed generation in the main grid reliably and cleanly. When designing the control system of a microgrid, several functions must be considered, such as the management of electrical and thermal energy, load management, synchronisation with the main grid, etc. Both companies and institutions have carried out research into the control of microgrids over recent years and many proposals can be found in the literature. Thus, the design of the control system of a microgrid is a complex task due to its multiple functions and the large number of proposed solutions. This paper presents a complete description of the main features of a microgrid and describes the characteristics of the control systems used. Details are provided of the control tasks involved and of the main types of controls proposed in the literature. In addition, this paper describes the controls used in existing microgrids all over the world and proposes future areas for research. This work has been carried out inside de Research and Education Unit UFI11/16 of the UPV/EHU and supported by the Department of Education, Universities and Research of the Basque Government within the fund for research groups of the Basque university system IT394-10 and by the University of the Basque Country.