Camilo A. Cortes

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.

Volume comparison of DC-DC converters for electric vehicles

One of the main problems in autonomous electric vehicles is the volume of the electrical systems, because bulky components carry additional mass and high cost to the total system. Consequently, Interleaving phases and magnetic coupling techniques have been reported as effective methods for increasing the power density of the DC-DC converters that interface the storage unit with the electric motor. However, there are several converter topologies that use these techniques. Therefore, a volume assessment of these topologies is required in order to have a complete understanding when an electric power train is designed. In this paper, a volume modeling methodology is introduced with the purpose of comparing four different DC-DC converter topologies: Single-Phase Boost, Two-Phase Interleaved with non-coupled inductor, Loosely Coupled Inductor (LCI) and Integrated Winding Coupled Inductor (IWCI). This analysis considers the volume of magnetic components, power devices (conventional and next-generation), cooling devices and capacitors. As a result, interleaving phases and magnetic coupling techniques were validated as effective to downsize power converters. In particular, it was found that LCI and IWCI converters offer lower volume in comparison with other topologies.

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.

Efficiency optimization of a single-phase boost DC-DC converter for electric vehicle applications

One of the main problems in autonomous electric vehicles is the energy storage, because a high autonomy and high power condition demand large mass, big volume and high cost of the storage unit. Consequently, in order to avoid power losses and to downsize the storage unit and the electric systems, the electric power train in the vehicle must be as efficient as possible. This paper proposes a methodology to optimize the efficiency of a DC-DC converter that interface the storage unit with the motors drive. In this way, with the purpose of increasing the efficiency, this methodology combines three techniques: 1) The use of low-loss components such as Si CoolMos, GaN and SiC diodes and Mosfets, and Multilayer Ceramic Capacitors, 2) a complete power loss analysis as a function of the switching frequency and a calculation method of core losses based on the approximation of Fourier Series, and 3) the Area Product Analysis of magnetic components. With this methodology, it is possible to achieve high efficiency and high power density, which is suitable for automotive applications. The methodology has been verified with a set of tests on a 1kW prototype. As a result of the proposed methodology, a power efficiency of 99% was experimentally obtained.

Efficiency optimization of a two-phase interleaved boost DC-DC converter for Electric Vehicle applications

Power losses and their consequences in the addition of storage cells have the negative effect of decreasing the power density and the efficiency in Electric Vehicles. For this reason, an efficiency optimization methodology is required to help reduce that problem. Specifically, in the power converters that interface the storage unit with the electric motors and their inverters, an efficiency optimization is essential to reduce the power losses and thereby downsize the cooling components and the storage unit. In this work, the topology under evaluation is the two-phase interleaved boost converter using different magnetic components such as coupled and non-coupled inductors, which are topologies known as effective for high power density applications. This paper presents a methodology that optimizes the efficiency of the chosen topologies through a complete power loss modeling of each component. Next generation components such as Super Junction Mosfets, GaN and SiC diodes and Mosfets are compared to obtain the most efficient and suitable material to be implemented to the topologies, especially to the converter with coupled-inductor. Moreover, a design procedure is proposed to integrate the loss model and the characteristics of the selected components as the base to obtain the objective function, which is later solved using analytical calculations. Finally, the optimization methodology is validated by experimental tests.

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.

Analysis of wavelet based denoising methods applied to measured lightning electric fields

This paper describes the results of a wavelet based noise reduction procedure applied to three lightning electric field signals recorded in Bogotá-Colombia, Colombo-Sri Lanka and Toronto-Canada. In general, the evaluated signals were affected by three different noise sources. These are the analog-to-digital converter (ADC), the electronic circuit and the environmental noise.

Denoising of lightning electric field signals using fractional Fourier transform

In recent years, several activities have been carried out by EMC-UNC (research group) to measure, study and classify the parameters of lightning electric fields signals in Bogotá, Colombia. However, measurements are distorted and exhibit significant noise levels caused by undesired signals from the electromagnetic environment together with other types of disturbances produced by the measuring system, which inevitably introduces noise in signal measurements. This paper shows the results of applying the fractional Fourier transform (FRFT) as an alternative technique to reduce the presence of noise and also of undesired signal components within a set of electric field signatures. Basic conditions to carry out the filtering process in the fractional Fourier domain (FRFd) are presented. Afterwards, some lightning electric field temporal characteristics are analyzed by using the processed signatures. Important differences between processed and measured waveforms are observed.

Microgrid Topology Planning for Enhancing the Reliability of Active Distribution Networks

Loop-based microgrids are signified by their high reliability in islanded and grid-connected operations. This paper proposes an iterative procedure for the optimal design of a microgrid topology in active distribution networks, which applies graph partitioning, integer programming, and performance index for the optimal design. The proposed approach avoids infeasible and non-optimal designs of microgrid structures and provides remedial solutions for enhancing our previous topology design method. The numerical results for a microgrid test system show that the proposed designated steps can optimize a loop-based microgrid structure in an active distribution network.