Wilmar Martinez

High power density interleaved DC-DC converter for a high performance electric vehicle

For designing a high performance electric vehicle capable to run a quarter of a mile in 10 seconds, it is necessary to use ultracapacitors because they have high power density and their shelf life is longer than other conventional storage elements. These elements will feed four PM motor with a higher voltage requirement, so it is important to increase the power density of the DC-DC converter which interfaces the ultracapacitors with the motor drivers. In these conditions, a novel high power DC-DC converter is studied looking for a high efficiency with a small size. This work shows the design of a high power density interleaved DC-DC converter using closed-coupled inductors and the development of a prototype.

Design a DC-DC Converter for a High Performance Electric Vehicle

Ultracapacitors are an alternative storage element to deal with the power requirements of autonomous electric vehicles. This is possible because ultracapacitors can deliver large amount of power in short periods of time and their shelf life is longer than other conventional storage elements. For designing a high performance electric vehicle capable to run a quarter of a mile in 10 seconds, it was decided to use several modular ultracapacitors that have lower voltage levels than motors requirements. In these conditions, it is needed an efficient DC-DC converter which can manage the required power and energy to be delivered to electric motors, assuring the needed voltage and current levels. This work shows a design of a DC-DC converter that interface ultracapacitors and motors in a high performance electric vehicle. This design was possible by performing a power loss analysis, a component calculation and a simulation validation.

Sizing of ultracapacitors and batteries for a high performance electric vehicle

One of the main problems in autonomous electric vehicles is the energy storage, because of the use of low capacity batteries with low power delivery. This work shows a way to deal with the energy storage problem on a high performance electric vehicle capable to run a quarter of a mile in 10 seconds. The concept design of the system combines different storage technologies, ensuring the appropriate power delivery to the motors during the short time needed. In order to achieve this goal, it is necessary to determine the optimum size of each storage element to guarantee the vehicle high performance. This work proposes a methodology for evaluating different characteristics of ultracapacitors and batteries, such as mass, volume and cost. After determining the amount of the storage technologies, it is possible to make an optimal power management in the vehicle, that combined with the control of the motors improves the performance of the electric vehicle.

Power loss analysis of multi-phase and modular interleaved boost DC-DC converters with coupled inductor for electric vehicles

Efficiency is one of the most important aspects to consider in the design of electric systems for mobility applications. In this study, the interface between the storage system and the inverter is considered. This interface is a step-up DC-DC converter aimed to boost the energy storage voltage to the inverter voltage. This paper introduces the analysis, design, and comparison of four topologies of the interleaved boost DC-DC converter evaluating the effect of magnetic four-phase coupled inductorcoupling in multi-phase and modular circuits. Additionally, a novel idea of a four-phase coupled inductor is presented. These power DC-DC converters are designed in order to find the suitable arrangement with the best efficiency.

A novel three-phase LLC resonant converter with integrated magnetics for lower turn-off losses and higher power density

The aim of this work is to present a novel topology of a three-phase LLC converter with integrated magnetics. The converter operation and the comprehensive theoretical analysis are presented; this analysis follows the first harmonic approximation (FHA) approach to simplify the system model. Usually, LLC converter achieves zero voltage switching (ZVS) as long as it working in the inductive region. Therefore, the turn off losses are considered as the main source of the switching losses in the converter. In this paper the design in optimized to minimize the switching losses. On the other hand, adapting three discrete transformer cores in this topology will definitely increase the size and volume of the converter. As a result, a novel magnetic integration concept is introduced where all magnetic components of the three-phases are advantageously combined into a single magnetic core to increase the converter power density. Finally, the experimental results are presented to verify the optimized design by showing a reduction in the turn-off losses and the effectiveness of adapting the proposed integrated transformer, in which an increment of 56% in the power density of the converter could be attained.

A Magnetic Design Method Considering DC-Biased Magnetization for Integrated Magnetic Components Used in Multiphase Boost Converters

High power density and high efficiency in dc/dc converters are required in various applications such as the automotive application. Interleaved multiphase circuits with integrated magnetic components can fulfill these requirements because passive components occupying significant space in power converters can be downsized without high-switching frequency driving of power devices. However, dc-biased magnetization is a drawback of integrated magnetic components because of unbalanced inductor average currents. This imbalance arises from the tolerance among the phase components. To overcome this problem, inductor average current control is implemented in interleaved multiphase dc/dc converters. Nevertheless, the imbalance cannot be completely eliminated because the current sensors inserted into each phase have gain errors. The purpose of this paper is to present a magnetic design method to improve the immunity to unbalanced currents. A comprehensive analysis is carried out with two main objectives: to prevent magnetic saturation, which may arise due to the current unbalance and to downsize the magnetic components by selecting the optimal coupling coefficient taking into consideration the maximum permissible percentage of unbalanced currents. Simulation case studies are presented to support the analysis. Finally, a 1-kW prototype of the interleaved boost converter is built to validate the accuracy of the design method.

Iron-loss characteristics using a 1MHz GaNFET PWM inverter

Next-Generation semiconductor devices like Silicon Carbide (SiC) or Gallium Nitride (GaN) have been introduced for many applications in power electronics due to their outstanding characteristics of high frequency and low loss operation [1].

Sampling frequency influence on magnetic characteristic evaluation under high frequency GaN inverter excitation

Nowadays, there is a great interest on new magnetic materials and their outstanding properties of low iron losses. However, when a magnetic material is experimentally characterized, it is important to select a suitable sampling frequency specially when the inverter is driven at a high carrier frequency. Nevertheless, iron losses of a magnetic material under inverter excitation are usually underestimated when the inverter is driven at an insufficient sampling frequency. This paper introduces the iron losses of a magnetic material at high carrier frequency excitation using a GANFET inverter. In addition, the experimental evaluation of iron losses at several sampling frequencies is presented. As a result of the measurements, at low sampling frequencies, minor loops of BH curves could not be well constructed, because the inverter waveforms are not measured properly. Finally, experimental tests at 100 kHz and 1 MHz of carrier frequency presented an underestimation of 21.4% and 25.1%, respectively. This measurement error is presented when the inverter is driven at a sampling frequency lower than the suitable one.

Iron Loss Characteristics Evaluation Using a High-Frequency GaN Inverter Excitation

Recently, novel magnetic materials have been developed for high-efficiency and high power density electric motors. In addition, next-generation semiconductor devices, like silicon carbide (SiC) or gallium nitride (GaN), have been introduced for power converters due to their high-frequency operation. Therefore, high-frequency operation of new magnetic materials is possible when they are driven by GaN or SiC inverters. Nevertheless, iron loss characterization of magnetic materials when they are excited by high-frequency signals have not been conducted yet. This paper introduces the iron losses characterization of a magnetic material at high carrier frequency excitation using a GANFET inverter. This characterization was carried out by the experimental evaluation of iron losses at carrier frequencies from 5 to 500 kHz at different deadtimes. As a result of the measurements, iron losses seem to have a trend to increase at high carrier frequencies and large deadtimes. In addition, filtering is introduced and it seems to be an effective technique for reducing iron losses.

Control techniques for interleaved DC/DC converters with magnetic coupling

The interleaved boost converter with magnetic coupling is a recent DC-DC converter topology that has drawn attention for its reduced size and good voltage gain. However, for its proper functioning, a real converter has to be controlled to deal with the unavoidable imbalance of the currents. This paper compares two control techniques applied on an interleaved boost converter with magnetic coupling. Therefore, the characteristics of the selected converter, the average current control and predictive control techniques are presented. As a result, it was found that the average current controller has the characteristic of zero steady state error, in contrast, the predictive controller allows an error in the estimated variables which causes the output voltage not to be equal to the reference value. The predictive controller considers and uses the discontinuous mode of operation, but controller has a higher computational cost than the average current controller.