ARL/Northeastern UniversityARL/Northeastern UniversityProgress Report / Visit to ARLProgress Report / Visit to ARL

Brad Lehman (PI)

Visiting Grad Students: Rosa Ciprian, Florent Boico, Jennifer Savage

Dept. Elect. & Comp. Engin.

Northeastern University

Lehman@ece.neu.edu

(617)373-3052

Tuesday May 31, 2005

Project 1: Field Sustainment Power Conditioning (Wes Tipton)Project 1: Field Sustainment Power Conditioning (Wes Tipton) Project 2: High Temperature DC/DC Converter (Damian Urciuoli)Project 2: High Temperature DC/DC Converter (Damian Urciuoli)

ARL/Northeastern UniversityARL/Northeastern UniversityProgress Report / Visit to ARLProgress Report / Visit to ARL

Have we aged since October 27, 2004?

Overview of ProjectsOverview of Projects

• Field Sustainment Power Conditioning– Awarded Q4FY03– NU approximately $80k/year

• Model, design and build solar battery chargers for NiMH batteries

• Test solar arrays and batteries

• ARL funding for 1 grad student, but usually 2-3 work on the project (student projects, matching internal funds, etc.): Florent Boico, Jennifer Savage, Dung Nguyen

– Clark Atlanta University approximately $20k/year for simulation support

• High Temperature DC/DC Converters– Awarded Q4FY04 at approximately $190k/year

• Funded 2 students, but 3 grad students are actually working on project (matching funds): Rosa Ciprian, Ting Qian, Wei Song

– Results to date include• Prototype half-bridge: copper board prototype and pcb design for 2-stacked board

design, 1/2 –brick size (on order) of 2.4” x 2.3”x ~1”

• Simulations in Spice: evaluations of various topologies

• Thermal simulations: CFD and simplified electro-thermal models

• Invention of new two-stage topology for high voltage applications

Technical Challenges:• Problems reported by CERDEC of damaged batteries when charging with portable solar arrays;• Basic research: charging batteries in (relatively) high temperature with changing power source has not been investigated before;• Applied research: developing and building prototype chargers.

Field Sustainment Power ConditioningField Sustainment Power Conditioning

Major Accomplishments:

Team MembersBrad Lehman (NEU), Khalil Shujaee (CAU),Wes Tipton, (ARL)

Project Objective/Description1. Explain reasons for: Reduced battery

capacity, damaged batteries and reduced life-cycle;

2. Design, develop, and test solar battery charge controllers that: Fully charge batteries, maintain battery capacity and life-cycle.

Explained performance degradation of batteries when charging with solar array is due to high temperature overcharging ;

Designed, built, and tested solar array NiMH battery charger control algorithms;

-- New temperature differential charge control algorithm developed in 2005;-- Max. Power Point Tracker for charger (2005);-- Preliminary patent disclosure (2005);

2005 IEEE PESC paper to appear in June.

Note: 2005 Renewal funding received 5 months late: delayed research in solar charging of Li-ion batteries.

Charger

Technical Challenges:• High power density desired but…

• Large number transformer turns ratio• 85 degree Celsius Year 1 with no air flow

(increase to above 100 deg. Celsius in Y2)• 3000V input-output isolation• Primary switches are the source of

heat/power loss•Synchronous Rectification?

High Temperature DC/DC ConverterHigh Temperature DC/DC Converter

Some Year 1 Accomplishments:

Team Members: Brad Lehman, Northeastern University (NEU), Damian Damian UrciuoliUrciuoli, (ARL)

Project Objective/Description1. Design a high power density converter with

target size of ¼ brick (perhaps a little taller if place on two stacked boards)

2. Vin = 600 V; Vout = 28V, 1% load regulation

3. Year 1: Ambient temperature -10oC ~85oC

Simulations--- Spice analysis of candidate topologies: half-bridge, asymmetrical half bridge, invented topologies, …--- Thermal CFD and simplified steady state electro-thermal models

Prototype Half-bridge--- Open loop power efficiency above 89% --- Gerber files for ½ brick, two stacked board prototype have been shipped out for fabrication

Invented new two stage isolated DC-DC converter for high-voltage applications

Primary Turns 40 47 52

Secondary Turns 6 7 7

Vi(V) 618 623 614

Ii(A) 0.178 0.177 0.179

Vo(V) 28 28 28

Io(A) 3.5 3.506 3.506

Efficiency(%) 89.1 89.0 89.3

Prototype half-bridge