Center for Power Electronics Systems The Bradley Department of Electrical and Computer Engineering College of Engineering Virginia Tech, Blacksburg, Virginia, USA DC Nanogrids Igor Cvetkovic Presentation at:
Electronic Power Distribution System: A Notebook PC Improved battery technology? High density packaging? Smaller electronic components? Better power management? 1
I/O Peripheral Supplies LDO Regulators Logic Electronic Power Distribution System: A Notebook PC Disk Drive Power Supervisor 3.3 V Bus 12 V Boost Converter Fan Controller Bus Converter Processor 0.7-1.7 V Voltage Regulator Memory 1.8 V Voltage Regulator 5 V Bus Bus Converter Backlight 800 V CCFL Inverter LCD Bias 8 V LCD Converter Battery Monitor Battery 12-16 V 19 V 90-260 V Charger / AC Adapter Discharger 50-60 Hz Load converters: Meet dynamic energy requirements of the loads Source converters: Meet ac line standards; improve battery utilization Power Distribution Converters: Increase peak-power efficiency Improve power density Increase light-load efficiency Improve energy efficiency REDUCE COST! 2
Patching-up the 20 th Century Technology Integration of grid, renewables, and storage saves money! SMART METER GRID SOLAR ARRAY WIND TURBINE ENERGY STORAGE PLUG-IN HYBRID VEH. Requires dc-ac inverters for every source. 120 V, 60 Hz All electrical appliances have front-end ac-dc rectifiers. EMI PFC EMI PFC EMI PFC M EMI PFC M EMI PFC EMI PFC EMI PFC Smart appliances save energy! Consumer Electronics - TV, Computer, Projector Appliances - Washer, Dryer Appliances Air Conditioner Appliances Stove/ Range/Oven LED CF Light (ceiling) CF H Lamp (floor) 3
kwh Bidirectional power conversion Separation of dynamics Islanded operation Integrated protection Benefits: Higher efficiency Lower Web-based cost GUI Higher Time reliability Attractiveness & convenience Wireless communication Load management DG management Data acquisition 21 st Century Electronic Power Distribution System: DC Nanogrid with Bus Architecture ECC GRID 380 V, DC bus 48 V, DC Consumer Electronics - TV, Computer, Projector SOLAR ARRAY WIND TURBINE Energy Control Center (ECC) Features: Bi-directional topology Bi-directional control system Bi-directional current limit M M ENERGY STORAGE Bi-directional decoupling due to dc-link Appliances - Washer, Appliances Air Appliances Stove/ LED light Bi-directional EMI compatibility Dryer Conditioner Range/Oven (ceilig) Low dc leakage current Low cost, high density PLUG-IN HYBRID CF light (floor) 4
Static Operation of the DC Nanogrid (DC bus signaling) * GRID SOLAR ARRAY WIND TURBINE ENERGY STORAGE PLUG-IN HYBRID ECC DC bus 380 V ± 5% Group 1: ECC(s) Group 2: Ren. Energy Sources Group 3: Energy Storage Group 4: Loads LOAD V max V Bus V=f 1 (I) V=f 2 (I) V=f 3 (I) V=f 4 (I) State 1 State 2 State 3 State 4 Renewables Utility V min V=f n (I) State n Emergency 0 I max I * Bryan, Duke, 2004 5
Communication Pre-programmed Static V-I Curves of the Nanogrid System Sources GRID SOLAR ARRAY WIND TURBINE ENERGY STORAGE PLUG-IN HYBRID ECC DC bus 360 400 V ECC(s) Ren. Energy Sources Energy Storage 400 V 390 V 380 V 370 V 360 V Power demand from utility V V P MPP P max_ PV V SOC I bc SOC I bd To Grid To Nanogrid -I max g 0 I max g 0 To Nanogrid I s max To Battery To Nanogrid max max -I b 0 I b 6
Communication Optimal Energy Utilization in the Nanogrid GRID SOLAR ARRAY WIND TURBINE ENERGY STORAGE PLUG-IN HYBRID ECC 400 390 380 370 360 DC bus Nanogrid Can 360 Operate 400 V Autonomously with Partial or Entire Converter rating Communication Failure! Load 1 Load 2 Load 3 Grid interface converter V [V] V [V] B A Converter rating B A Converter rating I B g I A g 0 I g I A b I b B 0 I b 7
CPES DC Nanogrid Testbed Grid ECC Li-ion Battery bank (45Ah) Energy Storage Converter Electronic Load 6kW PV Converter Solar Simulator (15kW) 8
Experiment Demonstrating One Case of DC Nanogrid Autonomous Operation Power (W) GRID SOLAR STORAGE 5k 3 4k ECC V Bus Ig 360 400 V I s I Load Load I b 3k 2 2k 1 1k 0:00 6:00 12:00 18:00 0:00 I g (4A/div) I L (4A/div) I s (4A/div) 2 Load: 1kW Constant. I b (4A/div) 1 Battery starts to charge 3 25kS/s 40s/div 9
ECC DC bus DC Interface load step Dynamic Interaction Example in dc-nanogrid (Minimum relevant system - two sources and two loads) GRID 5 kw Load 1 3.3 kw 360 400 V Z S (s) Y L (s) 100 20 μf μf Z w 6.6 kw To avoid instability, the return ratio: L Z S Z L Load 2 0.5 kw must stay away from 1! ENERGY STORAGE 7.5 kw Unstable Stable Imaginary axis Phase (deg) Magnitude (db) Voltage [V] 400 380 380 370 360 360 340 50 0-50 90 0-90 -180 0.2 3 1.5 0.1 0-1.5-0.1-0.2-3 Bus Voltage v g v s 0.09 0.1 0.11 Time [s] Z LL v g v s Z L ZZ S S 10 1 10 3 10 5 Frequency (Hz) -3-1 -2-1 0 Real axis axis = 1 Y L Z SS 10
Phase [deg] Mag.[dB] Output / Input Impedances of the DC Nanogrid System Sources / Loads GRID SOLAR ARRAY WIND TURBINE ENERGY STORAGE PLUG-IN HYBRID ECC Z o DC bus 360 400 V Load 1 Load 2 Z i 400 V 390 V 380 V 370 V 360 V V SOC I bc SOC I bd K b 40 20 0-20 -40 90 0 K b To Battery To Nanogrid max max -I b 0 I b -90-180 Freq. [Hz] 10 1 10 2 10 3 10 4 10 5 11
Plug-in Hybrid A house Electric (Nanogrid) Vehicle ( Picogrid ) Bidirectional Charger pecc 12
A house Microgrid (Nanogrid) House Energy Control Center necc 13
Microgrid Miligrid Microgrid Energy Control Center μecc 14
Miligrid Miligrid Energy Control Center mecc 15
Expanding DC Nanogrid Concept to: Consumption Distribution Transmission Generation G ES GECC G Hierarchical Network of Dynamically Decoupled Electronically Interconnected Sub-networks Intergrid DG DG DC Microgrid μecc AC Microgrid ES DG L L ES μecc L necc necc necc L DG ES ES DG ES DG AC Nanogrid L L L L L L L L DC Nanogrid DC Nanogrid 16
Center for Power Electronics Systems The Bradley Department of Electrical and Computer Engineering College of Engineering Virginia Tech, Blacksburg, Virginia, USA Thank you! Questions/ Comments / Suggestions?