
2/17

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Outline

DC-Link Challenges in Traction Motor Drives

Alternative DC-Link Approaches

Summary


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3

What is the Cost of Ripple Currents in a

Traction Drive?

Ripple effects the life and reduces the energy in

the DC source (Battery, Fuel Cell)

Ripple effects the performance/efficiency of the

motor drive (inconsistent Vin = inconsistentperformance)

The capacitor provides a low impedance path forharmonics/transients (ripple)


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Prime Drivers for Challenging Capacitor

Requirements in Traction Motor Drives

High inverter switching

frequency easy filtering

requirements.

Extended motor operation in

the constant power region

(six step) more difficultripple (fundamentals 6th

harmonic) requirements.

Highly transient load

also requires high

capacitance.


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5

FY04 Milestone

Objective:To assess subsystems capability to

meet DC-link capacitor performance, volume,

weight & cost targets.

Milestone: Evaluate the perform-

ance of active filters to reducethe size/cost of capacitors/

DC-link.


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Alternative DC-link Approaches

Active filter can significantly reduce capacitor requirements

Additional architecture based solutions could

reduce/eliminate capacitors

What solutions could be

used in the DC-link?


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7

Technological Approach

Active filters evaluation:

component sizing

perfomance potential

architectures

Active

Filter(AF)

Inverter

Active

Filter(AF)

Inverter

Active

Filter(AF)

Inverter

V-injection

Active

Filter(AF)

Inverter

I-injection

Why focus on this architecture?

Representative of

achievable performance

Non-proprietary (well known

architecture)


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Active Filter Component Sizing

Equivalent ripple circuit

used for sizing components

Inductor is 5.8mH for

supplying low frequency

ripple energy

Capacitor is only 20uF

This architecture requires

large V, I switch ratings

may be costly

E i l t Ri l Ci it


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9

Equivalent Ripple Circuit

Performance Comparison

Equivalent Voltage Ripple Performance

Capacitor-only: 100,000uF -versus- AF with 20uF Capacitor

Fi ld W k i


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10

Field Weakening

Inverter Square Wave Operation

fe=33.3Hz, fripple=200Hz

Cap-only: 2000uF -versus- AF w/ 20uF (fs = 50kHz)

versus

Fi ld W k i


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Field Weakening

Filter Capacitor 5% of Targeted

fe=33.3Hz, fripple=200Hz


Si ifi t DOE


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Significance to DOEs

FreedomCAR goals

Using active filters can

significantly reduce

passive componentrequirements in the DC-

link

AF solution should bemore fault tolerant,

reliable, and compact

Capacitor temperaturetolerance affects failure /

life more significantly than

with switches

?


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13

Summary of Work

AF passive components can be sized for lower

energy requirements.

AF architecture will be very important in

determining switch sizing/cost.

AF performance can be superior to capacitorsin the DC-link.

AF switches are already high density and

capable of 125-150C


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14

Future Work

Continue evaluating AF architectures.

Further evaluate price potential (architecturedependent).

Evaluate AF performance under dynamic drive

cycle conditions.

Plan to work with AF experts at Texas A&M,

Illinois Institute of Technology, and Colorado

School of Mines.


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15

Appendix: Transient Behavior

-110

-90

-70

-50

-30

-10

10

30

50

70

100 110 120 130 140 150 160 170 180 190 200

time (s)

Current(A)

I_hyb_total I_hyb_NiMHI_hyb_UC

Charge

DischargeUCap

Current Total Current

Battery Current

12

14

16

18

Voltage(V)

Filtered Voltage

Battery-only Voltage

Linear PWM Region


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Drive fs = 3 kHz

Linear PWM Region


Fripple>>200Hz


Linear PWM Region


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Drive fs = 19.8 kHzAF fs = 150 kHz

Linear PWM Region


Fripple>>200Hz


Documents

Program Review 6-7-04 Dc Link Cap