Power Electronics for Grids Prof. Dr. Lothar Frey Fraunhofer Institute of Integrated Systems and Device Technology IISB Chair Electron Devices, Friedrich-Alexander-University Schottkystrasse 10 91058 Erlangen - Germany www.iisb.fraunhofer.de 1
Content Why grids? Known grids High-voltage transmission grids in vehicles Local grids (Micro grids) Summary 2
Why grids? Up to today: AC dominating because of AC power generation & transformers (Edison/Westinghouse) But: Regenerative energy promotes PV, fuel cells, CHP or wind provide directly and more cost-effective power Energy storages becomes important (increasing share of wind & PV) Batteries, electrolyzers (H 2 ) work on basis Reactive power increases losses and reduces transmission capacity in AC grids Problem does not exist in systems, HV Transmission Efficient power electronic converters available For grids, power electronics highly shrinkable /AC no active front end, / by increasing frequency 3
High Voltage Transmission Example: HV Transbay Cable Example MMC in HV application: Transbay Cable (2008-2010) ± 200kV P = 400MW Q = ±300MVAr 88 km submarine cable 1296 power electronic building blocks per converter station 1296 modules Source: Siemens Source: Transbay Cable Page 4 IISB / LES, 17.07.2013
High Voltage Transmission Example: HV Transbay Cable New Design: Modular Multilevel Converter (MMC / M²C) = Modular concept based on power electronic building blocks 5
High Voltage Transmission Example: HV Transbay Cable Power electronic issues (examples) Application of new devices and modules Design and experimental verification of fail safe Electrical and thermal behaviour Driver design for 3.3-4.5 kv IGBTs in modular multilevel environments Auxiliary components (power supply, sensor circuits, ) Source: Siemens 6
Grids in Vehicles 14 V Bordnetz Grid is the backbone of e-vehicles! Variety of power electronic converters Efficient, small & reliable: Driver for scaling! 7
Efficiency Power electronic scaling: new devices SiC and GaN Open New Horizons in Power Density and Efficiency Fraunhofer IISB GaN Reference Design 1) Buck/Boost converter GaN devices (600 V, normally-off) Output power: 1,5 kw (@380 V) Power density: >30 kw/dm 3 100% 99% 98% 97% 96% 95% 94% 93% 92% 200 300 400 500 600 700 800 900 1000 Switching frequency [khz] V HV Fraunhofer IISB SiC Reference Design 1) Buck/Boost converter SiC MOSFET, 1200 V, normally-off Switching frequency: 200 khz Efficiency: >98,5 % (760 V 670 V) Power density: 140 kw/dm 3 1) with Panasonic devices 8
Local Grids (Micro Grids) 9
Local Grids (Micro Grids) Power Supply of Electronic Equipment AC is responsible for 40...80% of power dissipation 50...95% of weight 50...95% of size in the line adapter or power supply of any electronic equipment! Power Supply Board of a flat screen TV 10
Local Grids (Micro Grids) Home installation and appliance technology today 98%... Efficiency (0) 85% 230 V AC 11
Local Grids (Micro Grids) Smart Local Grids Energy efficient and data networking 99% Stationary storages 95% 24 V Energy plus Data (LAN) 380 V 98% 230 V AC 12
24 V grid + Local Grids (Micro Grids) An Universal LV- Plug System Power socket insert Appliances +24 V / converter GND OUT FB alternativ + 5 24 V R x R x One plug for all low-power appliances 1) The socket provides the individual supply voltage requested from the appliance Electroless, arc-free (dis)connection by leading opening pilot contact 1) up to 100 Watt 13
Local Grids (Micro Grids) Size Comparison AC Line Adapter vs. LV-/ Converter 75 W 230 V AC 19 V 75 W 24 V 19 V Efficiency: 95 % Efficiency: 87 % 14
Local Grids (Micro Grids) Today Tomorrow AC Lighting Lighting 230/400 V AC AC AC ballast Refrigeration, Air Conditioning AC AC inverter +/- 380 V driver Refrigeration, Air Conditioning AC inverter IT IT Mains transformer L1 L2 L3 N PE AC adapter AC Appliances Mains transformer L1 L2 L3 N PE AC L+ M L- AC Appliances 15
Local Grids (Micro Grids) Center-fed Grid Topology Local power generation Public AC grid MPP tracking Grid Manager bidirectional AC grid connection AC Stationary batteries e.g. lighting Consumer 250 400 V 380 V Mobile batteries Prosumer fast charging 60 400(850) V 16
Local Grids (Micro Grids) offers many advantages, but open issues Efficient power electronics Grid control Central/Decentral Control Earthing and Protection Arcing 17
Local Grids (Micro Grids) -Grid Manager for small commercial buildings Local power generation Public AC grid MPP tracking 0 20 A -Grid Manager -22 +22 kw bidirectional AC grid connection Stationary batteries -40 +40 A -60 +60 A AC 0 +8 kw, 380 V -8 +8 kw e.g. lighting Consumer 250 400 V Mobile batteries Prosumer fast charging 250 400 V 8 channels à 20 A in one (!) 19 inch, 2U (HE) module 1) 380 V 1) i.e. 60 kw total power @ >98% efficiency 18
380 (+/-380) V Backbone Local Grids (Micro Grids) Decentral Grid Topology (or generally PE dominated grid) Local power generation Public AC grid AC Stationary batteries Consumer e.g. lighting Mobile batteries Prosumer 19
From local grids (Micro grids) to PE dominated grids! How to control a grid without a superordinated master? I dg,pv PV = f(mpp) I dg,pv I load,1 Droop Control The grid voltage (V dg ) serves as the central control variable 370 V 380 V 390 V V dg I load,2 All feed-in converters operate as voltage sources with internal resistance AC Battery AC grid I dg,bat I dg,ac I load,3 constant power 1) Intelligent Power units with interfaces for power and signal transmission I dg,x I max(+) R i 370 V 380 V 390 V I max(-) V dg See presentation Dr. Zeltner 1) typically negative differential input impedance, i.e., input current increases as line voltage drops 20
Summary For the Time being, AC grid will not be replaced by grids But power electronics enables The combination of and AC to a smart hybrid grid Which allows Cost reduction on device, infrastructure and system level Increase of comfort ( smaller, lighter ) and connectivity ( Internet of things ) Increase of design freedom (e.g. LED lighting) Easy integration of renewable energy sources and storages 21
Thank you for your attention! Fraunhofer IISB Your Partner in Power Electronics 22