Federico Martin Ibanez

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.

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.

Online indirect measurement of ESR and capacity for PHM of capacitors

This paper shows a system to measure the Equivalent Series Resistance (ESR) and Capacitance (C) of capacitors. This system provides a cost effective solution for Prognostic Health Monitoring (PHM) of capacitors used in fully electric vehicles (FEV) and medium-power switching supplies. The system is based on a Hartley resonant topology formed by two inductors and a variable capacitor. This circuit is able to measure Metalized Thin Film Capacitors (MTFC) as well as electrolytic capacitors. The paper analyzes the circuit and compares the results of simulations and experiments.

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.

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.

100kW bidirectional DC/DC converter for a supercapacitor stack

This paper presents the design of a 100kW DC/DC converter that transfer energy from/to two 125V-supercapacitor stacks to/from a 560V DC line that is attached to a three-phase inverter. The converter provides galvanic isolation between the 560V DC line and the supercapacitors. In one power flow direction, it works as a step-up DC/DC converter that maintains the DC voltage at 560V by delivering energy from the supercapacitors, and in the other direction it works as a current source to charge the supercapacitors. The proposed design is a two-stage converter: a series resonant converter that raises the supercapacitor voltage by four and provides isolation, and a half-bridge converter that maintains the output voltage by adjusting the step-up process. Experimental results are presented. The efficiency of the whole converter is higher than 91% at input currents up to 500A.

5kW–100 kHz resonant converter prototype for a 40kW energy system unit on tramways

This project has been oriented to the development of an energy system unit for powering tramways during shorts periods of time. The aim of this work is to present the results obtained for a high frequency DC-DC converter which is included in the energy unit. The energy unit will consist on two type of energy storage devices: a battery stack and a supercapacitor stack. A comparison of the simulated model of the DC-DC converter and the real measurement on both topologies, resonant switching and hard switching, has been done. The system works at high frequencies to reduce the weight. In addition, the efficiency should be optimized to reduce the heat sink area and the volume of the whole system. In this case, a 5kW–100 kHz bidirectional DC-DC converter was developed and the results of the first stage are presented.