E. F. Piene, "Grid Connected Vehicles Capabilities and Characteristics," in Electric Vehicle Integration Into Modern Power Networks, DTU, Copenhagen, 2010
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E. F. Piene, "Grid Connected Vehicles Capabilities and Characteristics," in Electric Vehicle Integration Into Modern Power Networks, DTU, Copenhagen, 2010

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  • 1. Course date 22 September 2010 Course place DTU Lyngby, Copenhagen EES-UETP Course title Grid connected vehicles Capabilities and characteristics Egil Falch Piene THINK Global AS Norway
  • 2. History • Founded 19 years ago in Norway • The first prototype predecessor to today’s modern THINK City was developed in 1991 • The first generation THINK City was produced from 1999-2003 • Ford Motor Company owned and invested heavily in THINK between 1999-2003 • In 2006 Norwegian investors bought THINK and have invested over $120 million to further develop the latest generation THINK City • Production moved to THINK’s strategic partner and shareholder, Valmet Automotive of Finland, in late 2009
  • 3. EV design requirements 1. Optimize for energy efficiency and range 2. Optimize for cost and driving performance 3. Optimize for basic and sneaky design 4. Optimize for grid conditions and battery life Think is doing "practical innovation"
  • 4. Scope of this presentation • Description of system in an electric car conductively connected to the grid, with AC transferred to an on-board charger • Highlight some specifics for systems integration, with focus on the modules involved in the charging process • Briefly discuss regulation services from a user and vehicle perspective
  • 5. Questions in mind • What will be needed to prepare for the charging infrastructure, so the grids can supply many simultaneously connected EVs? • Are the vehicles being designed well enough, so when many connected they do not aggravate conditions in the grids?
  • 6. Block diagram of modules AC-charging from a 1-phase or 3-phase source AC AC DC COM Charging On-board Traction Station Charger Battery L1 L2 L3 N PE Vehicle CAN COM Vehicle BMS Controller Grid side Vehicle side
  • 7. Plug-in vehicles today • Typical for plug-ins today, is that they charge with the power available, without taking care of other loads or even any other grid condition • The vehicle charger system and the user takes for granted that there are energy and grid capacity available
  • 8. Charging time versus interface Gain of 80% State of Charge Battery size: 25 kWh Total efficiency: 80% Courtesy of BRUSA www.brusa.biz
  • 9. Power x time = km km/charge-hour Source Transfer EV * PIHV Th!nk City • 230V 1ph 16A 3.6kW 18 7 17 (3,2kW) • 400V 3ph+N 16A 11kW 55 - 51 (9,6kW) • 400V 3ph+N 32A 22kW 110 - - • 400V 3ph+N 63A 44kW 220 - - • 690/400VAC ** DC 50kW 250 - TBD * Example: General EV with ca 200 Wh/km consumption, "Plug-to-Wheel" ** CHAdeMO >400 Wh/km 190 Wh/km
  • 10. Block diagram of modules DC-connected from an off-board charger, bypasses the AC on-board charger AC DC DC On-board DC Charger COM Traction L1 Off-board Battery Power relay L2 control unit L3 Charging N Station PE Vehicle CAN COM Vehicle BMS Controller Grid side Vehicle side
  • 11. Front - end • Charging station • Today's Li-ION – Provide energy traction batteries – Electrical safety – 90 - 130 Wh/kg – Forward available – 150 - 200 Wh/l maximum current – 450 - 600 $kWh – Link communication – Metering energy • Battery pack size for – Payment an usable EV – IEC/EN 61851-1 – 15 - 40 kWh with sub standards – 150 - 400 kg
  • 12. EV battery monitoring system • BMS is a highly integrated module with specific software • Protection for overload, overcurrents, overheat, overcharge • Doing measurements and calculations • Taking care of cell balancing • HV isolation monitoring towards chassis • Diagnostics and communication
  • 13. On-board Charger • The input voltage range shall without any configuration, cover the voltages available in all domestic power systems
  • 14. Input voltage range • Japan = 100 V to UK = 240 V ±10% • which give 90 - 264 V + margin • which give ≈ 85 - 275 V • @ 50 - 60 Hz
  • 15. Output voltage range • The output voltage range need to match the on board traction battery system • Li-ION cells may have voltages varying from 2.5 to 4.2V - depending its state of charge (SOC) • A modern EV will typically have (ca) 100 cells in series, which gives an operating voltage range of 250 to 420V
  • 16. - further properties • Efficiency as high as possible • Power output as linear as possible • Conducted noise as low as possible • Galvanic isolation (grid to traction battery) • Power factor correcting • Must respond to a control signal • Light weight • Automotive requirements *
  • 17. HE rectifier circuits DC out AC in Transistor Transistor drive signals drive signals Primary side Secondary side DSP CAN DSP SPI Courtesy of ELTEK VALERE www.eltekvalere.com
  • 18. HE rectifier efficiency 100% 98% 96% 94% Efficiency 92% 90% HE rectifier 88% 86% Standard rectifier 84% 82% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Load Courtesy of ELTEK VALERE www.eltekvalere.com
  • 19. Energy consumption and loss • Assumptions – 25 kWh battery with 5% internal system loss – 3 kW on-board charger – Average daily depth of discharge 60% – 240 commute days pr year • Energy delivered to battery – Per day: 25 kWh x 0.6 x 1.05 = 15.75 kWh – Per year: 15.75 kWh x 240 = 5 749 kWh • On-board charger conversion losses – 90% efficiency: 420 kWh per year – 95% efficiency: 199 kWh per year • Energy saved pr year: = 221 kWh
  • 20. Power factor correction & noise • Power supplies sold and used in Europe must be compliant to the below standard, which sets the limits for grid current harmonics (up to 2 kHz) • For power supplies larger than ca 250 W, active power factor correction is necessary to reduce feedback of harmonic currents EN 61000-3-2
  • 21. Grid current harmonics 16 Measurements from a 3 kW unit @ 230 V 14 12 1. Harmonic (50 Hz) 10 Ampere Measured harmonics 8 EN61000-3-2 limits 6 4 2 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Harmonic number Courtesy of ELTEK VALERE www.eltekvalere.com
  • 22. Automotive requirements • Vibration resistive and mechanical stability • Wide temperature range • Efficient cooling • Sealed enclosures and connectors • High voltage isolation
  • 23. Single loop charging regulation • In a traditional battery charger circuit, the regulation is based on the battery's need COM Charging On-board Traction Station Charger Battery L1 L2 L3 N PE Vehicle CAN COM Vehicle BMS Controller
  • 24. Effects of negative impedance • If the grid voltage drops, a connected charger with single loop regulation would increase the input current to maintain a constant current or power output • The increased input current will represent a heavier load that may even drop the voltage further down • The max current allowed from the charging station, must be registered by vehicle
  • 25. AC current regulation loop • An EV prepared for Smart Charging would need one additional regulation loop COM Charging On-board Traction Station Charger Battery L1 L2 L3 N PE Vehicle CAN COM Vehicle BMS Controller
  • 26. Coincidence factor • If standardization for protection against charger’s negative impedance is not solved in the vehicle systems, a smart grid signal could make control of distributed power • When dimensioning charging facilities for fleets or many vehicles, the coincidence factor would need to be carefully assessed
  • 27. Balancing 3-phase • Phase individual loads can by achieved by the use of three single charger units • Separate voltage measurement and control • Power 10 kW L1 ~/= L2 • Redundancy L3 ~/= DC • Single phase ~/= configurable N CAN
  • 28. Statement Ph.D. Lars Henrik Hansen
  • 29. Questions in mind 2 • How can plug-in vehicles develop from only being a load and become a medium for regulation services? • What alternatives are here now?
  • 30. Regulation capable or not • Dumb charging • V2G Plugging in whenever In control from the and wherever grid operator • Timer charging • Smart Charging Plug in, but no charge In control from the until assumed valley grid operator or other hours source
  • 31. The sceptics response to V2G • Uncertainty regarding the market for regulation • New regulation technologies are emerging • Which user incentives, "cash-back" only and how will it be influenced by the volume of cars? • User applicability, hence adaption, how combine grid regulation with the need for driving range?
  • 32. Smart charging scheduler • Smart phone apps, • Not only as the plan for the next drive control instrument for the user, • but as well a way of spreading the information towards modern times for greater concerns about energy consumption
  • 33. Automakers V2G response • Culture of designing machines for transportation, not for storing electricity • New technology, few standards • Long time for development and validation • Which battery life impact? • Warranty aspects with battery system • Safety for electrical hazards, liability issues • Extra cost on the vehicle • Different and new business models
  • 34. Capacity retention
  • 35. General impacts on Li-ION life • High temperatures (> ≈ 55 C) • Too heavy charge or discharge at low temp • Too heavy charge or discharge at low SOC • Too heavy charge or discharges • Full or deep discharge cycles • Storage empty (self discharge) • Time
  • 36. Charging efficiency, vehicle
  • 37. Full V2G, not yet... • Imperative that the owner of vehicle doesn’t suffer an economic loss due to accelerated retention of the battery • Economic incentive must cover battery system wear and degradation • Warranty and legal aspects must be transparent • Comprehensive ‘Cash Back’ model is needed for EVs and PHEVs
  • 38. For realisation now is V2G light • Providing regulation • The battery will not be up and down worn more than in a according to a regular operation scheduled middle • Less losses in both charge rate LV-grid and vehicle • Vehicle should be in • Setup will probably daily use, as require more vehicles regulation service in the pool, to provide would be possible only the same grade of while charging up regulation compared to real V2G
  • 39. Control through infrastructure • Local fleet servers for power or time share depending the local capacity and number of vehicles connected and counting energy • Control signal from metering data grid operator through a fixed line • Aggregation server to collect load data and • Wireless not regarded provide control signal suitable for faster response demands • Standardized protocol
  • 40. - more "V2G light" • The vehicles would • Target for charge rate need a small extra response time communication unit less than 3 sec • The charging station • Aggregator to control would need to be charging rate within connected "on-line" predefined limits • The user would need • Not only for fleets, the a scheduler via web system can possible or in a phone-app be general available
  • 41. Added autonomous regulation • In case the communication is lost, – the vehicle charger system could enter an autonomous mode, by providing regulation with a fraction of the scheduled charge rate with response to the line frequency – a preset charge rate according to the average daily/hourly load profile could work as a back up and make the control – The user would be notified via the phone-app scheduler and still have the option to override
  • 42. Local storage, regulation, solar, wind, and fast EV-charging Grid inverter 4 x,150kWpeak, bidirctional DCDC-converter Frequency 50Hz Bidirectional, no isolation Photovoltaic panel Switching frequency 24kHz Switching frequency 48kHz MPP-Voltage up to 300V with external prefilters 50kVA 20kWpeak LV Grid 3 x 400 VAC+N AC DC DC AC DC DC AC DC AC DC 350 V DC Direct connection to the vehicle Main battery 2nd life EV batteries 10 x Na-NiCl, Z36 2 to 3 charging spots 250A capability (87W) U-nominal = 370V DC P-nominal = 250 - 500kWh Courtesy of BRUSA P-peak = 500 - 1000kW www.brusa.biz