Luis Fontan

A Step-Up Bidirectional Series Resonant DC/DC Converter Using a Continuous Current Mode

This paper presents the analysis and design of a novel technique that allows the conventional series resonant dc/dc converter (SRC) to work as a step-up and step-down converter. This is useful in bidirectional dc/dc converters where one port is attached to a fixed voltage dc line, e.g., a 360-V dc line, and the other port is attached to an energy storage device such as a bank of supercapacitors or batteries. Every converter that works in this scenario requires step-up and step-down modes to transfer energy from one port to the other. The paper presents the SRC as an alternative to the well-known dual active bridge (DAB). The dc analysis is detailed to demonstrate the step-up capability. In addition, the ac analysis is presented. Experimental results from a 6-kW prototype validate the theoretical analysis. The results indicate that this technique achieves better efficiency compared to the phase-shift DAB in a wide power range, from heavy to light loads. The main reason for this is that the converter works with smaller currents than the DAB at light loads.

Analytical Calculation of the Slot Leakage Inductance in Fractional-Slot Concentrated-Winding Machines

This paper obtains analytical expressions for the calculation of the slot leakage inductance for fractional-slot concentrated-winding (FCSW) machines with one-, two-, or four-layer windings. The formulas are derived from solving the 2-D Poisson problem associated with the slot region, making them more accurate than classically used expressions that assume a leakage flux path parallel to the placement of the conductors in the slot. Explicit formulas are given in the case of one- and two-layer FSCWs with a number of phases ranging from 3 to 7. The obtained analytical expressions are validated by a finite-element analysis, showing excellent agreement between both calculation methods, even for large slot-opening-to-slot-pitch ratios. A brief comment with regard to the fault-tolerant capability of permanent-magnet FSCW machines with respect to the number of layers is also given.

Design methodology of a balancing network for supercapacitors

This paper presents and analyzes a non-dissipative balancing system for supercapacitors. The circuit design is carried out by means of a controlled buck-boost converter in order to have the same voltage in each supercapacitor. The paper presents an energy loss analysis in two cases: a dissipative and a non-dissipative balancing circuit. It also develops a probabilistic analysis in order to estimate the efficiency of the balancing system during a constant current charge for a 10-, 30- and 45-supercapacitor series stack. Finally, simulations and measurements are carried out to verify efficiency in a supercapacitor stack with the buck-boost topology. The prototype on which the balancing analysis is performed consists of 45 3000F supercapacitors, and stacks of up to 60 devices are simulated.

Comparison between pole-placement control and sliding mode control for 3-pole radial magnetic bearings

This paper presents two control techniques for a radial active magnetic bearing (AMB) system in a kinetic energy storage flywheel: Pole placement control and Sliding mode control. Both control methods are based on a previous feedback linearization of the nonlinear 3-pole magnetic bearing configuration. The whole system is modelled and simulated in MATLAB/Simulink so that both controls can be compared taking into consideration the transitory and stationary responses. Experimental results are presented and compared to the simulations in order to verify the proposed simulation models and to analyze the most suitable version to be implemented in the prototype.

Modeling and simulation of a direct space vector modulated Matrix Converter using different switching strategies

This paper presents a MATLAB/Simulink simulation model for a direct space vector modulated matrix converter (MC). The power circuit model, consisting of an input filter, a matrix of bidirectional switches and an RL load, is completely implemented using the power library in Simulink, contributing to the simplicity and clearness of the whole model. Two switching strategies are modeled, simulated and analyzed together with the direct space vector modulation (DSVM): symmetrical SVM and asymmetrical SVM. Two sets of rules are proposed for these techniques in order to simplify the model implementation. Principal input and output converter variables are presented in simulations so that MCspsila characteristics and advantages can be observed. Moreover, this model is also very flexible about changing the modulation technique, the load, or removing the input filter, making it suitable for an introduction of this kind of converters in an educational environment.

Modelling and simulation of indirect space vector modulated matrix converter using MATLAB®/Simulink®

This article describes a MATLAB®/Simulink® simulation model which analyses the fundamentals about a direct AC–AC power converter with an important research interest at the moment: the matrix converter (MC). The article is focused on space vector modulation modelling applied to this particular converter. The power circuit model is completely implemented using the power library in Simulink, contributing to the simplicity and clearness of the whole model. MC is modulated using the Indirect Space Vector Modulation (ISVM) model which is implemented and explained step-by-step following the space vector basic theory. The model is flexible about changing the modulation technique, the load or removing the input filter, becoming an effective simulation tool in the first stage of a real implementation. It can also be used in an educational environment to present the basic space vector modulation theory applied to the MC.

Two coarse frequency acquisition algorithms for OFDM based IEEE 802.11 standards

A novel coarse carrier frequency estimation approach is proposed for the IEEE 802.11 OFDM family. This approach employs the properties of the preamble to reduce the carrier acquisition problem to single tone frequency estimation. Two low cost algorithms are proposed. Their main features and implementation details are analyzed. The first algorithm presents good performance in moderate and high SNR multipath environments. The second algorithm is very robust in low SNR multipath scenarios. Extensive simulation results are presented.

High-Current Rectifier Topology Applied to a 4-kW Bidirectional DC–DC Converter

This paper analyzes the benefits and drawbacks of using a modified center-tab rectifier in a high-current bidirectional dc-dc converter. In order to do this, an analytical model of the rectifier is proposed, and a design procedure based on this model is presented. Simulations and experimental data from a prototype validate this model. This topology is also optimized to reduce diode/switch reverse voltage stress. The prototype is designed to be attached to a supercapacitor stack in order to generate a regulated output power supply. Because one side of the converter (the supercapacitor side) has to transfer currents of up to 100 A at a low voltage (less than 50 V), the main reason for choosing this topology is the low conduction losses that it presents.

Anomalous step-up behavior in discontinuous series resonant converters

This paper presents the analysis of a bidirectional series resonant converter (SRC) for light loads working in a discontinuous mode. By using the discontinuous mode, the converters efficiency is increased because zero current switching is possible at both the turn-on and turn-off process. However, an anomalous step-up behavior was found when the converter is attached to light loads. A comprehensive analysis of this phenomenon is presented and a practical solution for keeping the voltage conversion ratio fixed was implemented in a 25 kW prototype. The converter prototype is used in a supercapacitor power chain to transfer energy to a 560VDC link in a smart grid.

In-service SNR estimation without symbol timing recovery for QPSK data transmission systems

In this paper we consider the problem of estimating the signal-to-noise ratio (SNR) of the received signal in a QPSK data transmission system. This estimation must be done in-service (non-data aided), without carrier phase knowledge and without symbol timing phase knowledge. New algorithms with these features are derived from the ratio of two moments. The performance of these algorithms is studied by means of simulations, and it is shown that they are robust against carrier and symbol timing frequency offsets as well. This makes them suitable for a wide range of applications.