E. Gubia

Operation and control of a high performance inverter consisting of a buck-boost and a zero switching losses H-bridge for photovoltaic systems

This paper analyses the control of a especial inverter topology consisting of a buck-boost and a H-bridge in which the first one generates a rectified output voltage and the second one inverts one of each two half cycles. As a consequence, the H-bridge commutates at twice the line frequency and, what is more important, at zero voltage. Switching losses are therefore zero, and global losses of the inverter topology are very small achieving thus a high performance. In addition, the AC output voltage can be lower or greater than the DC input voltage. Both properties make this topology very interesting for photovoltaic systems. The main drawback of the structure is that the buck-boost has to be controlled in a variable operating point condition. This paper proposes two new control loops for the inductor current and the output voltage that include different compensations and feed-forward loops. This control strategy makes possible a fast and accurate control of the inverter output voltage. In addition, it achieves a high immunity to external perturbations such as input voltage and output load disturbances. Simulation tests show the robust performance in these situations as well as in case of transient short circuits and nonlinear loads connection.

University-industry collaboration chairs: Initiatives at the Public University of Navarre

In the current context of economic crisis, the university Chairs funded by private companies emerge as useful tools to establish a steady and fruitful collaboration between universities and industry. The activities, configuration and management of the Chairs at the Public University of Navarre (UPNa) are described along the paper. The UPNa Chair for Renewable Energies is shown as a successful initiative, particularly concerning its Engineering Degree Final Project and Master Thesis Program.

EMI filter inductor size for transformerless PV systems based on the full bridge structure

This paper analyses the influence of the modulation technique on the size of the grid EMI filter inductor in a full bridge converter for photovoltaic systems. Additionally, the use of an alternative modulation technique is proposed which exhibits the best compromise concerning efficiency, current quality and EMI filter size.

“24 hours of innovation”: A trans-pyrenean challenge initiative

The goal of the 24 hours of innovation challenge is to encourage student teams from French and Spanish universities around the Pyrenees to find creative solutions to challenges put forward by participating companies. The initiative is presented and analyzed in this paper as an efficient way to promote creativity and innovation in the new engineering students.

Design of flexible cost-efficient international engineering curricula at Public University of Navarre

The need for stablishing International Programs at the universities is particularly relevant in the case of the Engineering Degrees. In a context of progressive industrial globalization, the new engineering students have to be not only competent in technical aspects but also exhibit good skills in terms of foreign languages and intercultural knowledge. In order to attract new students, and particularly the best of them, the Schools of Engineering propose every year an increasing number of International Curriculum Programs. However, the design of these Programs is not an easy task. The need for organizing both a specific enrolment and separate classes makes the design of these Programs very expensive and therefore difficult to implement in small and medium-size universities. In order to avoid these problems, specific cost-efficient International Curriculum Programs have been designed and set up in the School for Industrial and Telecommunications Engineering of the Public University of Navarre (UPNA). These programs do not imply an extra cost for the University and are highly flexible to changes in the number of students interested every year. The results since the Programs were implemented are very satisfactory and show their high effectiveness in terms of reduced costs, positive academic results and high interest of the students.

New organizational and assessment frameworks for company internship programs

Old company internship programs in the pre-Bologna degrees dealt mainly with helping the students find a suitable company to stay for a time interval outside the academic periods. No assessments were implemented to evaluate the acquired competences and no especial procedures were required since these internships were not included in the student academic curricula. The new requirements for company internships in emerging European Higher Education Area make it necessary to lay down new organizational frameworks and stablish clear and efficient assessment procedures. This paper describes the initiatives carried out within the Engineering Degrees of the Public University of Navarre. The Degree in Engineering in Industrial Technologies is shown as a good example of the program. Results achieved so far are very satisfactory for both the companies participating in the program and the students taking part in the internships.

Redefining best practices in company internships

Initiatives aimed to promote best practices in company internships in the emerging EHEA are presented. They have been implemented in the new curricula of the School of Industrial and Telecommunications Engineering of the Public University of Navarre. They imply a redefinition of the way these actions were formerly designed. The most salient features of the new approach are the key role played by the acquisition of competences, focus on learning objectives and a more comprehensive grading system.

A method for modeling the power flow in train auxiliaries fed by two inverters set in parallel

Nowadays trains offer a level of comfort and services that obviously imply a higher energy consumption to feed the auxiliary train power systems. Usually, the auxiliary power systems are fed by two power converters placed in opposite ends of the train. These power converters share the demanded power and depending on how over-dimensioned the system is, they offer a certain level of redundancy. The correct functioning of the converters set in parallel may only happen if the right synchronization of the voltage generated by each of them is guaranteed. Otherwise, there would be an inadequate flux of power flowing between them. There is an increasing interest on operating the converters set in parallel without the need of a communication line to transmit the signals to synchronize the converters so as to simplify the system and make it more robust. The Droop Control technique, based on the steady-state regime power flux analysis, enables such goal. This article analyzes the decisive impact of the supply line on the dynamics and the stability of the system based on the Droop Control technique. Furthermore, a simplified model that integrates the control loops of both converters and the line dynamics is proposed. This model accurately analyzes the train auxiliary system power flux behavior both during steady-state and transient regimes. Hence, the suggested model is an adequate tool to study control strategies.

Engineering international programs at the public university of Navarre: A satisfactory on-going experience in a context of industrial globalization

In a context of global industrialization, the engineers have to be not only competent and technically well-prepared but also show effective communication in other languages, preferably English, and intercultural skills. For an engineering degree to be competitive, their academic curriculum has to be designed taking into account this fact. This paper describes the Engineering International Programs at the School of Industrial and Telecommunications Engineering of the Public University of Navarre, and particularly how they are organized into two programs, namely the International Curriculum Program and the Student Mobility Program. Both Programs are described in terms of organization, management and admission requirements. Preliminary results of this work-in-progress experience, including number of students enrolled in the Programs and results of the students satisfaction surveys, are very satisfactory and show the growing interest of students and teachers in the Programs and, more generally, in the internationalization of the academic curricula of the Engineering Degrees of the School.