Transcript Cho`s Lab: Distributed Power System

Power Electronics Research
at Seoul National University
Bo-Hyung Cho
Department of Electrical Engineering & Computer Science
Seoul National University, Seoul, Korea
Presented at Nagasaki University
http://spec-e.snu.ac.kr
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Outline
Cho’s Lab
Research Interest:
- DC-DC Conversion
- AC-DC Conversion
- Distributed Power Systems
- Electrified Vehicles (EV) Systems
- Battery Management Systems
http://spec-e.snu.ac.kr
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Cho’s Lab: DC-DC Conversion
• DC-DC Conversion on EV Funded by
• project outline
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2.9 kW DC-DC converter development
power flow between high-voltage Li-ion battery to Pb battery
high efficiency: 94% with wide input/output voltage range
high power density: 550 W/Liter with 200 –A high current management
[ An Electric Vehicle Power and Drive System ]
[ Example of developed converter]
http://spec-e.snu.ac.kr
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Cho’s Lab: AC-DC Conversion
• labtop power adapter funded by
• project outline
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extremely low profile: 6.3mm
high mass-productivity using PCB winding
very high frequency switching: 1MHz
high efficiency: 85% @ half load, 89% @ full load
Multi Layer
[ Prototype [145mm X 80mm X 6.3mm] ]
http://spec-e.snu.ac.kr
[ Multi Layer PCB Windings ]
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Cho’s Lab: AC-DC Conversion
• lamp ballast for street light system funded by
• project outline
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ballast circuit for metal halide lamp to substitute Hg-Na lamp
digital control with communication and diagnostics
robust to extreme operation conditions such as lightening, humidity, temperature
high efficiency: 95% @ full load
[ circuit diagram ]
[ lamps and ballast circuit ]
http://spec-e.snu.ac.kr
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Cho’s Lab: Distributed Power System
AC Distribution
DC Distribution
•inefficient interface as renewable sources are wide spread
•Ineffective interface with storage (ac-dc)
•efficiency and reliability issues
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•streamlined conversion from renewable source to loads
•effective interface with storage
•improved efficiency and reliability expected
Issues
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DC system design and operation strategy
Efficient interface of DC to AC grid
Interface for renewable energy sources and storage devices
Standards for DC system: STD voltage, regulation
Safety issues: Grounding, Isolation, Islanding
Protection strategies for subsystems and their cooperation
http://spec-e.snu.ac.kr
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Cho’s Lab: Distributed Power System
• DC powered green building system funded by
• project outline
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renewable energy interface
high-efficiency power converters
system protections
smart meters with
wireless communications
– plug-in hybrid vehicle charger
[ DC Distribution Green Building ]
http://spec-e.snu.ac.kr
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Cho’s Lab: Distributed Power System
• building integrated photovoltaic (BIPV) panel funded by
• project outline
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power system for office building (testbed Seoul Nat’l Univ. Bld. #33)
36 kW roof-top PV and 20 kW BIPV
20 kW LED & various office loads
protection including arc detection and islanding
[ system architecture]
[ Building with PV panels ]
http://spec-e.snu.ac.kr
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Cho’s Lab: Distributed Power System
• PV interface power converter
• project outline
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high efficiency through ZVS and ZCS (higher than 98%)
electrolytic-cap-less design for reliability
Input Voltage (PV volt.)
Output Voltage (DC Line)
Fujitsu DC relay applied for protection
Maximum Power
arc fault protected Design
Cdc
Inductance, L
island detection guaranteed within 0.2s
0-145 V
380 V
120 W
Film, 10 μF
Core: RM14LP, 710 μH,
MOSFET, S
28NM50N, 500 V, 21A
Diode, D
SDT08S60, 600 V, 8A
[ system spec. ]
[ Prototype PV Converter ]
[ system architecture]
[ Anti-Islanding Algorithm ]
Cho’s Lab: Battery Management System
• battery screening funded by
• project outline
– selecting battery cells to improve voltage/SOC balancing of battery pack
– screening algorithm for multiple cells
[ capacity mismatch ]
[ State-of-charge mismatch ]
[ proposed algorithm for battery screening ]
Cho’s Lab: Battery Management System
• battery management system funded by
• project outline
– implementation of battery management circuits connected to individual battery
cells
– estimation of state of charge (SOC) using
Extended Kalman Filters
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SOC
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Power Supply 2
Ampere-Counting
EKF
Power Supply 1
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xˆ ,k 1
Electric Load 2
Controller 1
Electric Load 1
xˆk 1
x,ˆ k
uk 1
ˆk
Humidity Chamber
Time Update
EKFx
Dual Monitor
Battery (Load)
Controller 2
ˆk 1
0.55
Measurement
Update EKFx
Time Update
EKFx
ˆ,k 1
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x̂k
ˆ,k

uk
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yk
Measurement
Update EKFx
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Time[s]
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Computer 1
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[ cell SOC estimation ]
ˆk
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SOC
Electrochemical Impedance
Spectroscopy
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Ampere-Counting
EKF
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[ estimation algorithm for SOC
estimation ]
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Computer 2
Battery Group
(Cell, Pack)
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[ experimental setup for BMS test ]
http://spec-e.snu.ac.kr
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Time[s]
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[ pack SOC estimation ]
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