Transcript here - ECE Senior Design - University of Connecticut

Hybrid Go-Kart
University of Connecticut
Department 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
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Introduction
Power Sources
Boost Converter Revisions
Flyback Converter
EIS Characteristics
Timeline/Next Steps
2
What is Our Project?
• Design a power electronics system to
combine three separate power sources in
order to drive an electric go-kart.
3
The Power Sources
• We will use three power sources:
oA 30V Lead Acid battery
oFour ultra-capacitors, wired in
series, at 14V across bank
oPhotovoltaic Panel, 8->40V
output, 200W
4
System Overview
5
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.
7
Parallel Current Paths
• Placing multiple power stages in parallel
is one way to handle the current.
8
Parallel Paths (cont.)
• Again, the inductors caused problems.
•
1
𝐿1
+
1
𝐿2
+ ⋯+
1
𝐿𝑖
=
1
𝐿𝑒𝑞
• 8 inductors were required
• An integrated circuit controller solution
was found.
9
Integrated Circuit
Controller
10
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.
12
Boost Power-Stage
Platform (cont.)
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Flyback Specifications
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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
𝐿 = 𝑁 2 𝐴𝐿
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Flyback Schematic
Flyback Transformer
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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
𝑊𝑎𝑡𝑡
= 𝑘𝑓 𝑚 𝐵𝑀𝑎𝑥 𝑛 , where k,m and n are constants
𝑘𝑔
that pertain to specific core material, 𝑓 is frequency
and 𝐵𝑀𝑎𝑥 is the maximum flux density.
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𝐵𝑀𝑎𝑥
• Core saturation
• Residual flux
• 𝐵𝑀𝑎𝑥 =
𝑉𝑝𝑘 𝑡𝑜𝑛 𝑥108
𝑁𝐴𝑒
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
18
EIS Testing
•
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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
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Electron & ion transport, gas & solid phase reactant
transport, heterogeneous reactions  different
characteristic time-constants  exhibited at
different AC frequencies.
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
Frequency Response Analyzer (FRA)
Programmable 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.
EIS Setup Phases
• FRA  Computer
interface
o Manuals, Drivers, XP OS
• FRA out signal
o Frequency sweep test
• Cooling T connector
o Battery, ultra-capacitors, PV
panel
• C2E2 EIS testing setup
o Battery & ultra-capacitors
FRA  Computer interface
Timeline Updated
•Blue = Original Plan
•Yellow = Updated Plan
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
24
Questions?
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