Luis C. Herrero

Project-Based Learning and Rubrics in the Teaching of Power Supplies and Photovoltaic Electricity

Project-based learning (PBL) and cooperative learning are, in various aspects, very superior education methodologies compared to other traditional ones. They are highly appropriate methodologies for elective courses, as they exert a strong attraction on the students, quite apart from their educational advantages. This paper describes how PBL and cooperative learning have been used to teach the topics of power supplies and photovoltaic electricity within two elective undergraduate courses. A project is carried out for each of the two topics. Moodle is used as the e-learning platform to provide the course materials and the wiki resource and to allow the submission of assignments. The simulation is done by means of Simulink. Work has been done to develop skills for project planning, group management of the work, technical document writing and presentations in public. The methodology has been seen to be successful, as all the students who have followed it over the last few years have passed the courses in which it was included, Design of Industrial Applications and Industrial Electronics. Examples of the rubrics for assessing the projects and examples of the projects themselves are also included.

A simpler and faster method for SVM implementation

Space vector modulation is perhaps the common technique mostly applied to drive three-phase voltage-source inverters. During every switching period it calculates three duty cycles in order to generate a suitable pulse sequence. This paper presents a new, faster and, most important, simpler method to compute these time values without using either trigonometric functions or even Clarke or Park transformations. The result is a light-weight algorithm easier to implement in small digital signal processors or microcontrollers. The relationship between SVM and PWM is also explained.

Comparative Analysis of the Techniques of Current Commutation in Matrix Converters

The devices of power used in matrix converters (M.C.) need some operation sequences to commute the current in a safe way. These operation sequences are what we denominate strategies of current commutation, being these more complex than in other converters. In this article a comparative analysis of the different strategies of current commutation will be carried out by means of simulation and they will be implemented in a experimental matrix converter to analyze its behaviour. As comparison criterion of the different strategies that have been used, the total harmonic distortion (THD), the efficiency of the converter, the maximum commutation frequency and the necessary hardware requirements for the implementation of the strategies.

IDENTIFICATION OF DIFFERENT PRODUCTS OBTAINED BY ELECTROCHEMICAL AND PHOTOCHEMICAL REDUCTION OF THE HERBICIDE METAMITRON

The electrochemical reduction of the herbicide Metamitron (4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazin-5-one) has been carried out at different pHs using a mercury pool cathode. The final product of these reductions depends both on the electrolysis potential and on the pH. All processes are irreversible and the reductions of the CN and the NNH2 (pH > 3) or NNH+3 bond (pH < 3) are inferred. An aqueous solution of Metamitron is also degraded by sunlight leading to 4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazin-5-one (deaminometamitron). This reaction can be monitored polarographically.

Emulation of an OWC Ocean Energy Plant With PMSG and Irregular Wave Model

Ocean energy is a promising resource for renewable electricity generation that presents many advantages, such as being more predictable than wind energy, but also some disadvantages such as large and slow amplitude variations in the generated power. This paper presents a hardware-in-the-loop prototype that allows the study of the electric power profile generated by a wave power plant based on the oscillating water column (OWC) principle. In particular, it facilitates the development of new solutions to improve the intermittent profile of the power fed into the grid or the test of the OWC behavior when facing a voltage dip. Also, to obtain a more realistic model behavior, statistical models of real waves have been implemented.

Repercusiones económicas y sociales de los festivales culturales: el caso del Festival Internacional de Cine de Valdivia

Hoy, y debido a sus repercusiones en los territorios, la cultura y los festivales culturales forman parte de las estrategias de desarrollo local y regional, y de las actuaciones de regeneracion urbana. Tales repercusiones pueden ser de caracter social, cultural, turistico o economico, ya que la cultura genera impactos en terminos de produccion, rentas y empleos. En este marco, el objetivo de este trabajo es analizar la contribucion economica del Festival Internacional de Cine de Valdivia a la ciudad y region donde se celebra. Para ello se utiliza la metodologia de los Estudios de Impacto Economico, basada en la definicion y medicion de tres tipos de efectos (directos, indirectos e inducidos). Los resultados muestran que el festival genera una repercusion significativa sobre la economia de la zona, beneficiando especialmente al sector turistico de la ciudad, y a los servicios a empresas. El trabajo pone tambien de manifiesto la importancia que los espectadores dan a las repercusiones culturales del festival, que constituyen, en realidad, la esencia del mismo.

Hexagon based algorithm for Space Vector Modulation on multilevel voltage source inverters

A simple algorithm has been developed to control small and large multilevel inverters using Space Vector Modulation. It looks for a suitable hexagon near the reference voltage rather than the usual three nearest vectors. Then, switching vectors and their duty cycles are computed using straightforward equations, independent of the number of levels and easy to use in digital microprocessors. Several simulations have validated this method, finding that these duty cycles are exactly the same than others, computed using more complex methods.

Emulador de Lazo Abierto para Turbinas Eólicas de Paso Fijo

A novel emulator for fixed pitch wind turbines that allows laboratory testing of the generator control systems associated with the turbines is presented. The novelty of the emulator is to be an open loop scheme. The emulator consists of the coupling in series of a source of DC voltage, a power resistance and a DC motor. The modification of the input DC voltage has the same effect as the variation of wind speed in a fixed pitch wind turbine. This article includes: 1) theoretical foundations of the emulator, 2) Excel and Simulink simulations, and 3) experimental results obtained in a bench of electrical machines. It is shown that the emulator can reproduce the mechanical power curves of a fixed pitch turbine, but with certain limitations at low speed.

STATCOM Control Strategies

This chapter reviews the control systems used to enable STATCOMs to carry out their most important task, which is to deliver reactive power to the electrical grid. Later on, other control systems designed for more advanced applications are discussed, such as compensating the nonlinear loads. Later, the design of the control system when STATCOMs are connected to unbalanced electrical networks is presented. Several strategies are presented for controlling the converter, either as a linear current source which is also known as controlled Voltage Source Converter (VSC) based on the use of Proportional-Integral (PI) controllers, or as nonlinear current source, based on the use of hysteresis bands. Other systems, such as the firing algorithm of the switches or system synchronization with the grid, are also discussed.

Encapsulating connections on SoC designs using ASM++ charts

This article presents a methodology to encapsulate, not only the functionality of several SoC modules, but also the connections between those modules. To achieve these results, the possibilities of Algorithmic State Machines (ASM charts) have been extended to develop a compiler. Using this approach, a SoC design becomes a set of chart boxes and links: several boxes describe parameterized modules in a hierarchical fashion, other boxes encapsulate their connections, and all boxes are linked together using simple lines. At last, a compiler processes all required files and generates the corresponding VHDL or Verilog code, valid for simulation and synthesis. A small SoC design with two DSP processors is shown as an example.