José A. Villarejo

Optimizing the Design of Single-Stage Power-Factor Correctors

This paper presents a new analytical method for the generalized study of a cluster of single-stage power-factor correctors (S2PFCs). Due to this generalized approach, new topologies have been obtained, and the study of other known topologies has been simplified. The new analytical method simplifies the design of S2 PFCs by making it possible to compare a large number of different designs from the same viewpoint in order to identify the best topology. Finally, this research has enabled us to reduce the total size of the additional inductors that are used by a factor of two to three with respect to previous implementations

A new approach for teaching power electronics converter experiments

This paper presents a new methodological approach to teaching power electronics converter experiments. This approach is based on a reconfigurable hardware-software platform for use in converter experiments in a basic power electronics course. This course is an optional subject, and, therefore, the experiments need to motivate the students. The platform is controlled by software (made in a LabVIEW environment) run on a PC. The student can control the fundamental parameters of the selected converter topology through the user interface and, with a little work, can compare the results with a real circuit. An example of use of the methodology in an inverter experiment is included.

Effect of the Output Impedance in Multiphase Active Clamp Buck Converters

Passive current sharing in multiphase converters, where resistive losses are not dominant, is a quite complex goal. In this paper, an averaged model of an active clamp buck converter was obtained. It has been checked that this topology presents high output impedance. This property is used like a lossless passive equalization. The principle of operation, theoretical analysis, simulation, and experimental results are presented, taken from a three-stage laboratory prototype.

Comparison of central vs distributed inverters: application to photovoltaic systems

This paper compares the performance ratio of Photovoltaic (PV) plants using central and distributed inverters. A Single Diode Model is selected to simulate the electric behavior of PV-modules, including the dependences with environmental conditions. With the aim of reducing computational costs and avoiding complex mathematical resolutions, a graphical method is developed by the authors to estimate the power generation under different solar irradiation and temperature conditions. A Spanish PV plant is used to assess the power differences generated by both central and distributed configurations. Results under a variety of situations are also included in the paper.

Effect of the Output Impedance of Active Clamp Topology in Multiphase Converters

Passive current sharing in multiphase converters, where resistive losses are not dominant, is a quite complex goal. In this paper an averaged model of an active clamp converter was obtained. It has been checked that these topologies present high output impedance. This property is used like a lossless passive equalization. Simulated results of the average model accuracy and current sharing are presented.

Multiphase ZVS Active Clamp Boost Converter: DC and Dynamic Current Sharing

The active clamp boost converter (ACBC) has been analyzed, and a complete model has been obtained. It has been checked that it behaves as a voltage source with high input impedance. Because of this feature, this topology is suitable for multiphase design, where different stages share the load in a passive way, without any extra mechanism or components. The design of multiphase converters is simplified, particularly for a big number of phases, as no extra information must be processed. Steady-state current sharing has been studied as well as how component tolerances affect the current distribution. A simple design guide to select different components has been detailed, and, moreover, the conditions to achieve soft switching have been revised. To test passive current sharing, a two-phase ACBC has been built. It has been tested in open loop to prove that without any control loop or extra components, the load sharing is achieved.

Multistage Active-Clamp High Power Factor Rectifier with passive lossless current sharing

A new method to design active power-factor-corrector for high-power applications is introduced in this paper. It consist in using the high input impedance of Active Clamp boost converters in order to make easier the parallel connection of power stages. Experimental results are presented, taken form a three stages laboratory prototype rated at 0.35×3 kW, input ac voltage of 230Vrms, output voltage of 400V, and 120 kHz switching operation. Due to the simplicity of the current share technique, the control can be done using analog control based on the Unitrodes UC3854 strategy.

Current sharing in multiphase ZVT boost converter

Paralleling converters is a good choice for designing high frequency and high power converters. Nevertheless there must be a mechanism to share the load among phases to achieve all the benefits of parallel operation. A simple method to achieve current sharing is paralleling converters with high impedance. The ZVT Boost converter has interesting properties: Zero Voltage Transition, less semiconductors stress and high input impedance, what can be used as a passive lossless current sharing method. It has been analyzed in this paper, getting a complete model, where the impedance has been studied. A 2-stages 600 W prototype has been designed to test the current sharing.

Automatic Inspection System for Quality Evaluation of Fresh Tuna Meat

This paper describes an automated visual inspection system SIVATUNtrade for quality control of tuna meat which automate manual inspection operation. Depending on whether tuna are reared in cages or in the open sea and depending on the method of capture (electroslaughtering, shooting, etc.), differences are observed and changes take place in the organic nature of blue fin tuna (Thunnus Thynnus) meat, affecting appearance and quality. These changes are caused by an increase and accumulation of lactate, which negatively affects the quality. This drop in quality translates into loss of value of the meat in Japanese tuna markets (tsukiji market and sashimi market are the main destinations of tuna captured off the southeast coast of Spain). In order to evaluate these changes, Japanese experts are employed to carry out visual inspections, which therefore constitute a subjective assessment. This paper describes the development of an automated visual inspection system that can analyze, model and detect these changes. The ultimate aim is to establish quality indicators and classifiers that will accompany tuna meat from the time of capture and so make it possible to track this product in the main tuna meat export markets. In this way we can establish a connection between variation of tuna meat quality and the feeding and slaughtering methods used, thus providing feedback to the fattening and slaughtering processes so as to improve the global quality of blue fin tuna catches.

New Programmable Electrofishing Device for Use in Aquaculture

Abstract The new equipment described here was developed in response to a shortcoming in the technology available for electrofishing marine species. The system supplies a need that exists in commercial operations, and also allows research into the effect of the waveform on the quality of the meat. The equipment is capable of generating any kind of waveform, identifying the environment the electrodes are in, and logging the voltage and current values that are applied to kill the fish. Although it has been designed in the context of electrofishing for tuna, it is perfectly compatible with electrofishing in freshwater. The system is composed of two interacting parts: a software section and a hardware section. The software is capable of determining the relationship of each of the electrical wave parameters with the final quality of the meat. The electrical hardware main constituent is a full bridge with an inductor-capacitor (LC) filter. The effectiveness of two different types of control for this kind of conv...