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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 1/32 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 2/32 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 3/32 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] ] http://spec-e.snu.ac.kr [ Multi Layer PCB Windings ] 4/32 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 5/32 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 • •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 6/32 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 7/32 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 8/32 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 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 0.9 0.85 0.8 SOC 0.75 0.7 0.65 Power Supply 2 Ampere-Counting EKF Power Supply 1 0.6 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 x̂k ˆ,k uk x̂k 0.5 0 1 yk Measurement Update EKFx 2 3 4 Time[s] 5 Computer 1 8 4 [ cell SOC estimation ] ˆk 0.9 0.8 0.7 SOC Electrochemical Impedance Spectroscopy 7 x 10 Ampere-Counting EKF 0.6 [ estimation algorithm for SOC estimation ] 6 0.5 0.4 0.3 Computer 2 Battery Group (Cell, Pack) 0.2 0.1 [ experimental setup for BMS test ] http://spec-e.snu.ac.kr 0 0 1 2 3 4 Time[s] 5 6 [ pack SOC estimation ] 7 8 4 x 10