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

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

Cho’s Lab: DC-DC Conversion DC-DC Conversion on EV Funded by project outline 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

[ Prototype [145mm X 80mm X 6.3mm] ] [ Multi Layer PCB Windings ] Cho’s Lab: AC-DC Conversion labtop power adapter funded by project outline 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] ] [ Multi Layer PCB Windings ] http://spec-e.snu.ac.kr

[ lamps and ballast circuit ] Cho’s Lab: AC-DC Conversion lamp ballast for street light system funded by project outline 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

Cho’s Lab: Distributed Power System AC Distribution inefficient interface as renewable sources are wide spread Ineffective interface with storage (ac-dc) efficiency and reliability issues DC Distribution streamlined conversion from renewable source to loads effective interface with storage improved efficiency and reliability expected Issues 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

[ DC Distribution Green Building ] Cho’s Lab: Distributed Power System DC powered green building system funded by project outline 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

[ system architecture] [ Building with PV panels ] Cho’s Lab: Distributed Power System building integrated photovoltaic (BIPV) panel funded by project outline 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

Cho’s Lab: Distributed Power System PV interface power converter project outline high efficiency through ZVS and ZCS (higher than 98%) electrolytic-cap-less design for reliability Fujitsu DC relay applied for protection arc fault protected Design island detection guaranteed within 0.2s Input Voltage (PV volt.) 0-145 V Output Voltage (DC Line) 380 V Maximum Power 120 W Cdc Film, 10 μF Inductance, L 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 [ cell SOC estimation ] [ estimation algorithm for SOC estimation ] http://spec-e.snu.ac.kr [ experimental setup for BMS test ] [ pack SOC estimation ]