DC Nanogrids Igor Cvetkovic

Transcription

1 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:

2 Electronic Power Distribution System: A Notebook PC Improved battery technology? High density packaging? Smaller electronic components? Better power management? 1

3 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 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 V 19 V V Charger / AC Adapter Discharger 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

4 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

5 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

6 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,

7 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 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

8 Communication Optimal Energy Utilization in the Nanogrid GRID SOLAR ARRAY WIND TURBINE ENERGY STORAGE PLUG-IN HYBRID ECC 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

9 CPES DC Nanogrid Testbed Grid ECC Li-ion Battery bank (45Ah) Energy Storage Converter Electronic Load 6kW PV Converter Solar Simulator (15kW) 8

10 Experiment Demonstrating One Case of DC Nanogrid Autonomous Operation Power (W) GRID SOLAR STORAGE 5k 3 4k ECC V Bus Ig 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

11 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 kw V Z S (s) Y L (s) μf μf Z w 6.6 kw To avoid instability, the return ratio: L Z S Z L Load kw must stay away from 1! ENERGY STORAGE 7.5 kw Unstable Stable Imaginary axis Phase (deg) Magnitude (db) Voltage [V] Bus Voltage v g v s Time [s] Z LL v g v s Z L ZZ S S Frequency (Hz) Real axis axis = 1 Y L Z SS 10

12 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 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 K b To Battery To Nanogrid max max -I b 0 I b Freq. [Hz]

13 Plug-in Hybrid A house Electric (Nanogrid) Vehicle ( Picogrid ) Bidirectional Charger pecc 12

14 A house Microgrid (Nanogrid) House Energy Control Center necc 13

15 Microgrid Miligrid Microgrid Energy Control Center μecc 14

16 Miligrid Miligrid Energy Control Center mecc 15

17 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

18 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?