Jose Martin Echeverria

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.

Analysis of the Results of Accelerated Aging Tests in Insulated Gate Bipolar Transistors

The introduction of fully electric vehicles (FEVs) into the mainstream has raised concerns about the reliability of their electronic components such as IGBT. The great variability in IGBT failure times caused by the very different operating conditions experienced and the stochasticity of their degradation processes suggests the adoption of condition-based maintenance approaches. Thus, the development of methods for assessing their healthy state and predicting their remaining useful life (RUL) is of key importance. In this paper, we investigate the results of performing accelerated aging tests. Our objective is to discuss the design and the results of accelerated aging tests performed on three different IGBT types within the electrical powertrain health monitoring for increased safety (HEMIS) of FEVs European Community project. During the tests, several electric signals were measured in different operating conditions. The results show that the case temperature (TC), the collector current (IC), and the collector-emitter voltage (VCE) are the failure precursor parameters that can be used for the development of a prognostic and health monitoring (PHM) system for FEV IGBTs and other medium-power switching supplies.

30kW DC-DC Converters with Regenerative Mode for Electric Cars

This paper presents a design of a 30kW 250V/530V bidirectional DC-DC converter to be used in an electrical car. A detailed explanation of the design is given. The system uses two phase shifted half bridge (boost and buck) topologies to reduce the ripple current in the output capacitor. The converter has an efficiency of 95% at nominal power. It works as a constant voltage in one direction and as a constant current in the other to charge the batteries. Simulations and measurement are done at high power to test the efficiency.

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.

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.

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.

Flat magnets in surface-mounted permanent magnet machines: Influence and design

The presented work analyzes the influence of using Flat Magnets (FM) instead of a Single Curved Magnet (SCM) in surface-mounted Permanent Magnet Machines (PMM). FMs distort the air gap flux density due to non- constant air gap height above magnets and air spaces between magnets. Consequently, the air gap flux density fundamental harmonic component is smaller than that produced by a SCM. The larger the number of FMs, the better the approach to a SCM configuration; but this trend is not lineal and, therefore, there is an optimal number of FMs which makes maximum the efficiency/cost ratio. This work makes also possible to implement reduction factors in analytical calculation algorithms of PMM in order to consider FMs with their respective air gap flux density reduction. The proposed method uses finite element method software and obtains accurate results with very low computation time.

State-Plane Analysis of Anomalous Step-Up Behavior in Series-Resonant Converters

This paper presents the analysis of a bidirectional series-resonant converter (SRC) for light loads working above or below resonance. In normal operation (heavy load), it is well known that the SRCs have a maximum voltage conversion ratio (m) equal to one. This occurs when the switching frequency (fS) equals the resonant frequency (f0) and power losses are neglected. This maximum can also be obtained for fS <; f0 when the switches are turned ON during a half-resonant period. Thus, zero-current switching can be achieved at both the turn-ON and turn-OFF processes. However, anomalous stepup behavior is found when the converter is attached to light loads. A comprehensive analysis of this phenomenon in the timedomain and in the state plane is presented. Based on the latter, an expression that estimates m and shows the influences of the parameters is obtained. With the aid of this expression, a solution that mitigates that effect is presented and implemented in a prototype, which is part of a bidirectional power chain for supercapacitors. This solution can be implemented for both fS > f0 and fS <; f0.