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Hybrid Go-KartUniversity of ConnecticutDepartment of Electrical

Engineering

Team Members: Jonathan Blake (EE), Nathan Butterfield (EE), Joshua Calkins (EE),

Anupam Ojha (EE)Advisor: Prof. Sung-Yeul Park

11/18/2013

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Outline• Introduction• Power Sources• Boost Converter Revisions• Flyback Converter• EIS Characteristics• Timeline/Next Steps

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What is Our Project?• Design a power electronics system to

combine three separate power sources in order to drive an electric go-kart.

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The Power Sources• We will use three power sources:oA 30V Lead Acid batteryoFour ultra-capacitors, wired in series, at 14V across bank

oPhotovoltaic Panel, 8->40V output, 200W

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System Overview

Boost Converter(30V Output)

Ultra-capacitorBank14V

PV Panel8->40V

FlybackConverter

(14V Output)

Battery Bank30V

Motor Controller

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Boost Converter Design

• The design of our boost converter has changed drastically.

• The driving factor of these changes has been the input current.

• All of the following topologies were designed for 1.2kW.

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Initial Design: 12V->36V

• Two boost converters in parallel, one for the ultra-capacitors, one for the battery.

• Input current of 100A.• Finding an inductor rated for this

current within out budget proved impossible.

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Parallel Current Paths• Placing multiple power stages in

parallel is one way to handle the current.

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Parallel Paths (cont.)• Again, the inductors caused

problems.

• 8 inductors were required• An integrated circuit controller

solution was found.

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Integrated Circuit Controller

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PCB Implementation• Some of the paths shown in the

previous diagram would have currents of 100 A.

• The cost of a PCB capable of handling these currents may be cost prohibitive.

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Boost Power-Stage Platform

• High-current sections of a boost converter placed on separate platform, connected by cables.

• Current and voltage sensor output to microcontroller.

• Gate switching would determined by microcontroller, sent through gate drive circuit.

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Boost Power-Stage Platform (cont.)

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Flyback Specifications• High current caused for multiple design

alterations.• 4:7 turns ratio• Voltage Primary 8V-40V. Secondary Voltage 14V.• 16.7% to 50% Duty cycle• Current max 5A in 14.3A• Inductance on primary 20μH

Flyback Schematic

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Flyback Transformer• Selection of core geometry and material.• Toroid, E I core with gap• Kool mμ, ferromagnetic material, MPP• Core loss due to eddy currents and hysteresis ,

where k,m and n are constants that pertain to specific core material, is frequency and is the maximum flux density.

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𝐵𝑀𝑎𝑥• Core saturation• Residual flux• Gauss• Units used for B and H

are not consistant

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Litz Wire• High frequency

increases wire loss due to skin effect.

• Multistrand Litz wire distributes current

• Small wire gauge allows signal to penetrate into the wire.

• Higher cost• Window fill

• Measure impedance at different frequencies• Different sources and loads have different

electrochemical characteristics that can change overtime

• Humidity, temperature, oxidation & electrode corrosion

• Diffusion creates impedance at low frequencies (Warburg) makes impedance difficult to determine

• Electron & ion transport, gas & solid phase reactant transport, heterogeneous reactions different characteristic time-constants exhibited at different AC frequencies.

EIS Testing

EIS Setup• The device under test (DUT) will be the

battery, PV panel and ultra-capacitor.

Block diagram required for FRA to preform tests and obtain data.

FRA & eLoad• FRA injects a range of

frequencies along with a perturbation into the test device & signals the programmable load

• Measures voltage and current; creates Bode and Nyquist Plots

• Programmable eLoad varies impedance throughout the test.

Programmable eLoad

Frequency Response Analyzer (FRA)

EIS Setup Phases• FRA Computer

interfaceo Manuals, Drivers, XP OS

• FRA out signalo Frequency sweep test

• Cooling T connectoro Battery, ultra-capacitors,

PV panel

• C2E2 EIS testing setupo Battery & ultra-capacitors

FRA Computer interface

Timeline Updated

•Blue = Original Plan•Yellow = Updated Plan

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Next Steps• PCB Design of Flyback and Gate Drivers

• Physical Layout of Boost Power-Stage Platform

• EIS of Battery and Ultra-Capacitors

• Software algorithm and MPPT

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Questions?