F. Yeves

Examples of distance learning projects in the European Community

The innovation brought by the introduction of new technologies in our modern society has also started to appear in education. The biggest efforts come from the institutions involved in distance education, partly due to the characteristics of the educational system they represent. In order to improve the technology development there are a large number of projects being developed inside the European Union. This paper discusses the current situation of distance learning and the technological resources available including e-mail, video conferencing, Internet and the World Wide Web and virtual teaching-learning environment. Some of the European Projects including new technologies in distance learning are also discussed.

Active power filters for line conditioning: a critical evaluation

This paper presents a critical analysis of various topologies for power circuits used in power line conditioners designed to attenuate or remove disturbances in the electric power system. By defining a series of merit figures, it becomes possible to appraise the desirable qualities shown by the technical and economical aspects in each configuration. There is also a description of the basic lines for designing practical equipment. Finally, experimental results of a novel topology which reconfigures to UPS operation in the case of a power line failure are shown to confirm the validity of the prospective method.

Universal and reconfigurable to UPS active power filter for line conditioning

This paper describes an improved universal active power line conditioner designed to attenuate every disturbance in the electric power system and critical loads, except frequency variations. The circuit has a series voltage filter and a parallel current filter interconnected through a shared dc bus. In case of a supply interruption, the current filter reconfigures to UPS and feeds a preselected 20% of load during 500 ms at the expenses of the dc bus. Over previous reconfigurable solutions, the input and output series static switches have been eliminated improving the reliability, efficiency and cost. Optional parallel LC tuned current filters have also been proved to be control compatible. The search has been guided by an iterative analysis-plus-synthesis cost comparative method initiated in previous works, showing the cost of the components involved in each explored topology. Experimental results on three laboratory models and a 400 kVA industrial prototype validate the topology and suggest improvement of some control loops.

Approaching hybrid wind-diesel systems and controller area network

High wind penetration hybrid wind-diesel systems have complex control requirements. The random nature of the wind, the cubic velocity to power relationship and the fast response of wind turbines make control goals like maintain system stability, and prescribed power quality levels, not easy to achieve. This paper deals with how to implement a distributed control system based on the controller area network (CAN) in hybrid wind diesel systems with high wind penetration. Firstly some introduction to hybrid wind-diesel systems is presented. Secondly two architectures for such hybrid systems are presented and studied mainly from the control point of view. This study concludes with a need of a distributed control, and the definition of some sensor and actuator nodes in the system. The CAN bus is used to close one of the several regulation loops presented. Some considerations about real time distributed control like clock synchronization among nodes when using CAN bus are presented. Finally some advantages of using CAN with such hybrid systems are outlined.

Well-known serial buses for distributed control of backup power plants. RS-485 versus controller area network (CAN) solutions

Networking is increasingly becoming a feature of industrial products such as those for medical devices, vending machines, machine tool, and, the example analyzed here, modular power plants. As many such systems depend on cheap microcontrollers, a common approach to networking has been based on the combination of the available standard serial communication controller (UART) normally included in such devices and RS-485 drivers. However UART-based network protocols do have some potential disadvantages. Controller area network (CAN) offers an attractive alternative due to the availability and low cost of CAN based devices. This paper compares these two approaches in the design of a serial bus, devoted to internal interconnection in a commercial range of modular power backup systems, and describes the migration process from the first to the second solution.

Simulation as an aided tool in the EE learning

Nowadays simulation has become one of the most used aided tools in all fields of science and technology in general. Professionals and researchers use it in their work as an essential tool. The analysis and design of actual systems, which are becoming increasingly complex, would be very complicated or impossible without simulation. So that, for the past five years the Electrical and Computer Engineering Department (DIEEC) of the Spanish University for Distance Education (UNED) have a research area of work which main objective is to promote the use of simulation as a tool to support the teaching of electronic engineering. Within this objective, guided exercises via simulation have been developed based on these principles. The project is also working on the application of multimedia tools within electronic engineering teaching allowing integrating it with simulation.

A New Technique In Drive And Control Circuits For Power Electronic Systems

This paper presents a new technique in microprocessor drive and control circuits for power electronic equipments. This technique uses the PWM programmed method and one DMA controller to generate the drive pulses to switches. With this solution we get high performance in aspects as angle resolution and real time response. It has been developed a simple modular hardware and a control software useful in a lot of power applications. After tests in prototypes, results and conclusions are presented.

Four Quadrant Speed Control Of Induction Motor By Unrestricted Frequency Changer

This speed control system uses an AC/AC direct converter as driver, featuring that its output frequency margin goes from 0 to 127 Hz. Four quadrant speed control is entirely done by a microcomputer and calculation of the time functions of each power circuit bidirectional static switches (PCBSS) is done in real time, obtaining a high flexibility, high resolution, very trustworthy and drive circuit least components system.