• 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

Microgrids are a suitable, reliable and clean solution to integrate distributed generation into the mains grid. Microgrids can present both AC and DC distribution lines. The type of distribution conditions the performance of distribution line and implies different features, advantages and disadvantages in each case. This article analyses, in detail, all this parameters for AC and DC microgrids in order to identify and describe the available alternatives for building and configuring a microgrid. Elements and issues involved in the implementation and development, such as protections, power converters, economic analysis, availability, etc. are discussed and described. This analysis constitutes a tool for selecting a suitable configuration of a microgrid adapted to the needs in each situation. In addition, the article provides a picture of the current situation of microgrids, and identifies and proposes future research lines This workhasbeencarriedoutinsidetheResearchand Education UnitUFI11/16oftheUPV/EHUandsupportedbythe Department ofEducation,UniversitiesandResearchoftheBasque GovernmentwithinthefundforresearchgroupsoftheBasque universitysystemIT394-10andbytheGovernmentoftheBasque Country withintheresearchprogramETORTEKastheproject ENERGIGUNE12(IE12-335). 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 IT394-10 and by the Government of the Basque Country within the research program ETORTEK as the project ENERGIGUNE12 (IE12-335).

AbstractThis paper employs the Conditional Value‐at Risk, largely used in financial risk management, to specify the power reserve capacity of a wind power plant (WPP) under a risk metric. Evidences are shown here that other popular, simpler measure, the Value‐at Risk, is inappropriate for that specification. Under this risk‐based reserve metric, two programs are approached to optimally distribute a reserve request in a WPP subject to a given confidence level in the commitment. The most exhaustive of the two is a two‐level formulation including a solution to the load power flow (LPF) in the WPP. By solving these two programs, for comparison with interior‐point and heuristic solvers, conclusions are drawn. Notably, that a Pareto optimality occurs for stringent reserve requests; that putting off‐line generators is financially more profitable than partial curtailments to respond to low reserve requests; and that in these cases accounting for losses through LPF‐based optimization seems unnecessary. Copyright © 2016 John Wiley & Sons, Ltd.

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 demand for more reliable and efficient electric machines and drives is constantly growing in the renewable energy and transport electrification sectors. Such drive systems are usually fed by semiconductor switch-based inverters, which, unlike balanced pure sine-wave AC sources, produce large-amplitude, high-frequency common-mode voltage (CMV) waveforms, as a result of the application of pulse-width modulation (PWM). This can lead to a number of issues, such as high electromagnetic interference, deterioration of stator winding insulation, and leakage current flow through motor bearings, which dramatically reduce the life-cycle of machines and drives. Thus, this topic has been extensively investigated in the scientific literature, where either corrective or preventive mitigation approaches have been proposed. The former attempt to relieve the damage produced, whereas the latter tackle the problem at its root, by minimizing or eliminating the CMV produced by the inverter. This work provides a comprehensive review of the major CMV mitigation/elimination solutions, with emphasis on preventive actions, in the form of inverter topology variants and/or advanced modulation techniques. A wide picture of this subject is provided to researchers and field engineers, with valuable information and practical hints for the design and development of high-performance electric drive systems. Indeed, an in-depth analysis of the most recent literature clearly shows that best results are obtained by conveniently combining alternative topologies and modulation techniques, which, in some cases, make it possible to completely suppress the CMV component. This work has been supported in part by the Government of the Basque Country, Spain within the fund for research groups of the Basque University system IT978-16 and in part by the Government of the Basque Country, Spain within the research program ELKARTEK as the project ENSOL 2 (KK-2020/00077).

A large number of factors such as the increasingly stringent pollutant emission policies, fossil fuel scarcity and their price volatility have increased the interest towards the partial or total electrification of current vehicular technologies. These transition of the vehicle fleet into electric is being carried out progressively. In the last decades, several technological milestones have been achieved, which range from the development of basic components to the current integrated electric drives made of silicon (Si) based power modules. In this context, the automotive industry and political and social agents are forcing the current technology of electric drives to its limits. For example, the U.S Department of Energy’s goals for 2020 include the development of power converter technologies with power densities higher than 14.1 kW/kg and efficiencies greater than 98%. Additionally, target price of power converters has been set below $3.3/kW. Thus, these goals could be only achieved by using advanced semiconductor technologies. Wide-bandgap (WBG) semiconductors, and, most notably, silicon carbide (SiC) based power electronic devices, have been proposed as the most promising alternative to Si devices due to their superior material properties. As the power module is one of the most significant component of the traction power converter, this work focuses on an in-deep review of the state of the art concerning such element, identifying the electrical requirements for the modules and the power conversion topologies that will best suit future drives. Additionally, current WBG technology is reviewed and, after a market analysis, the most suitable power semiconductor devices are highlighted. Finally, this work focuses on practical design aspects of the module, such as the layout of the module and optimum WBG based die parallelization, placement and Direct Bonded Copper (DBC) routing. This work has been 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, and by the Government of the Basque Country within the research program ELKARTEK as the project ENSOL (KK-2018/00040) and the Generalitat de Catalunya under AGAUR Grant 2017-SGR-1384. As well as, the program to support the education of researches of the Basque Country PRE_2017_2_0008.

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.

La topología matricial en los convertidores de potencia AC/AC presenta una serie de ventajas interesantes: entre ellas destacan la disminución de precio, peso y tamaño con respecto a otras topologías. Sin embargo, a pesar de éstas, existen numerosas causas por las que este tipo de convertidores aún no se han producido a escala industrial. Algunas de estas causas se relacionan con la complejidad y la carga computacional del algoritmo de modulación que han de ejecutar los convertidores matriciales (CM), otras se relacionan directamente con la complejidad de las tareas de protección adicionales que requiere. En este artículo, se describe una solución en base a una FPGA (Field Programmable Gate Array) que permite abordar esta problemática y describe la forma en la que proporcionar una solución eficaz y económica que permita, en un futuro, la comercialización industrial de los CM

Electric vehicles (EV) are gaining popularity due to current environmental concerns. The electric drive, which is constituted by a power converter and an electric machine, is one of the main elements of the EV. Such machines suffer from common mode voltage (CMV) effects. The CMV introduces leakage currents through the bearings, leading to premature failures and reducing the propulsion system life cycles. As future EV power converters will rely on wide bandgap semiconductors with high switching frequency operation, CMV problems will become more prevalent, making the research on CMV mitigation strategies more relevant. A variety of CMV reduction methods can be found in the scientific literature, such as the inclusion of dedicated filters and the implementation of specific modulation techniques. However, alternative power converter topologies can also be introduced for CMV mitigation. The majority of such power converters for CMV mitigation are single-phase topologies intended for photovoltaic applications; thus, solutions in the form of three-phase topologies that could be applied to EVs are very limited. Considering all these, this paper proposes alternative three-phase topologies that could be exploited in EV applications. Their performance is compared with other existing proposals, providing a clear picture of the available alternatives, emphasizing their merits and drawbacks. From this comprehensive study, the benefits of a novel AC-decoupling topology is demonstrated. Moreover, an adequate modulation technique is also investigated in order to exploit the benefits of this topology while considering a trade-off between CMV mitigation, efficiency, and total harmonic distortion (THD). In order to extend the results of the study close to the real application, the performance of the proposed AC-decoupling topology is simulated using a complete and accurate EV model (including vehicle dynamics and a detailed propulsion system model) by means of state-of-the-art digital real-time simulation.