Joachim Skov Johansen Fast-Charging Electric Vehicles using AC Master’s Thesis, September 2013 Joachim Skov Johansen Fast-Charging Electric Vehicles using AC Master’s Thesis, September 2013 Fast-Charging Electric Vehicles using AC This report was prepared by Joachim Skov Johansen Supervisors Peter Bach Andersen Tonny Wederberg Rasmussen Chresten Træholt Release date: Date published Category: 1 (public) Edition: First Comments: This report is part of the requirements to achieve the Master of Science in Engineering (M.Sc.Eng.) at the Technical University of Denmark. This report represents 30 ECTS points. Rights: ©Joachim Skov Johansen, 2013 Department of Electrical Engineering Centre for Electric Technology (CET) Technical University of Denmark Elektrovej building 325 DK-2800 Kgs. Lyngby Denmark www.elektro.dtu.dk/cet Tel: (+45) 45 25 35 00 Fax: (+45) 45 88 61 11 E-mail: [email protected] Abstract Electric vehicles are here. Sales figures are approximately doubling each year, and the growth is projected to continue. The goal is to have 20 million electric vehicles on the roads by 2020. In order to reach this goal, it is now time to make intelligent choices for the next-generation electric drive technologies. One major challenge with electric vehicles is range anxiety. This project investigates AC fast-charging as a means of mitigating range anxiety while lowering total cost of electric vehicle roll-outs. The benefit of AC charging is that it allows vehicles to charge from an inexpensive AC charging station feeding power directly from the electric grid to the vehicle. Charge rates up to 43kW in Europe and 52kW in US are supported with standard AC cord sets. This power level matches that of the more expensive DC chargers. Hence, AC fast-charging technologies are an effective catalyst for considerably expanding fast-charging infrastructure. With AC fast-charging, high-power electronics are required on-board the vehicle. By reusing traction components for charging purposes, the on-board converter can be made inexpensive with only few additional components. The possible challenges with this high-power charger topology have been identified, and no inherent show- stoppers are found. Furthermore, these components allow bidirectional power flow, enabling vehicle-to-grid (V2G), vehicle-to-load (V2L) and grid-forming operation. This serves as an additional economical incentive for deploying AC fast-charging technologies. Regarding infrastructure, a unique 63A AC-only fast-charging station is developed. The all-electric Renault Zoe is charged at 43kW, proving AC fast-charging is indeed realizable. To support AC fast-charging at sites with limited grid power, a simple and practical load management algorithm is presented. Finally, high-level IP com- munication is enabled through the upcoming IEC 61851-1 Annex D standard, and EVs can be connected to the Internet or other IP networks. The project concludes that fast-charging using AC is feasible and practically re- alizable. If the recommendations presented are taken into account in future EVs and infrastructure implementations, it is expected that EV fast-charging will be easily accessible, range anxiety is minimized and costs related to increasing EV penetration are considerably reduced. i/xv Resumé Elbiler er kommet for at blive. Salgstallene fordobles hvert år, or væksten ser ud til at fortsætte. Målsætningen er at have 20 millioner elbiler på vejene i år 2020. For at opnå dette mål er det nødvendigt at træffe fornuftige valg i dag for teknologien i den næste generations elbiler. En af elbilens største udfordringer er bekymringen for en for kort rækkevidde og dermed at løbe tør for strøm. Dette projekt undersøger hvordan man ved hjælp af AC hurtigladning reducerer rækkeviddebekymringen, samtidig med at omkostnin- gen til fremtidig elbilsudrulning minimeres. Fordelen ved AC ladning er at elbiler kan lades fra billige AC ladestandere, hvor strømmen føres direkte fra elnettet til bilen. Det er muligt at opnå ladeeffekter op til 43kW i Europa og 52kW i USA med almindelige, standardiserede ladekabler. Dette effektniveau svarer til dét en noget dyrere DC-ladestander kan levere. På denne måde kan AC hurtigladning fungere som en katalysator til fremtidig udbygning af ladeinfrastruktur. Med AC hurtigladning er det nødvendigt at placere højeffektelektronik til oplad- ning af batteriet i bilen. Omkostningen ved dette i form af øget pris og vægt kan reduceres ved at anvende den eksisterende fremdrifts-elektronik, der driver elmo- toren, til også at bruges til opladning af batteriet. Udfordringer i forbindelse med denne metode identificeres, og der findes ingen direkte hindringer for praktisk an- vendelse. Med denne teknologi muliggøres også tilbageløbseffekt, hvilket omfatter at strøm kan løbe fra bil til elnet (V2G), fra bil til belastning (V2L) eller bilen kan spændingsstøtte elnettet (grid-forming). Dette udgør et yderligere økonomisk incitament for AC hurtigladning. En unik 63A AC hurtigladestander er udviklet. Elbilen Renault Zoe lades med 43kW, hvilket viser at AC-hurtigladning er praktisk muligt og realiserbart. I det tilfælde at et tilslutningspunkt i nettet ikke understøtter hurtigladning af mange biler samtidig, er der udviklet en simpel og praktisk algoritme til håndtering af denne type belastning. Derudover er højniveaukommunikation muliggjort ved hjælp af den nye IEC 61851-1 standard, og det vises hvordan elbiler kan kommunikere til Internettet eller andre IP netværk. Projektet konkluderer at hurtigladning med AC er muligt og realiserbart. Såfremt der tages hensyn til de præsenterede anbefalinger, er det forventet at hurtiglad- ning i fremtiden vil være let tilgængeligt, at rækkeviddebekymringen minimeres og omkostninger i forbindelse med udrulning af elbiler reduceres markant. iii/xv Acknowledgements v/xv vi/xv Contents Abstract i Resumé iii Contents vii List of Figures xi List of Tables xv Introduction 1 1 Technology overview 5 1.1 Why Electric Vehicles? . 5 1.2 EVs, connectors and charging power levels . 7 1.2.1 Charge level and average traction power . 10 1.3 AC versus DC fast-charging . 12 1.3.1 Flexibility . 13 1.3.2 Batteries and DC charging stations . 14 1.3.3 Charging station to EV ratio . 15 1.3.4 Onboard converter . 15 1.3.5 Comparing AC and DC power . 17 1.4 Why Fast Charging? . 17 1.4.1 Other range extending improvements . 19 1.5 Vehicle to grid . 20 1.6 AC versus DC conclusion . 23 vii/xv 2 Integrated motor drives and battery chargers 25 2.1 Introduction . 25 2.2 Motor drive power electronics . 26 2.3 Grid connected converters and power factor . 31 2.3.1 Power transfer through an inductor . 35 2.4 Implementation of the integrated motor drive . 38 2.4.1 Using motor leakage reactance . 38 2.4.2 Some IMD topologies . 39 2.4.3 Construction of discrete inductor . 42 2.4.4 Tests on Think City EV motor . 47 2.5 Converter topology challenges . 50 2.5.1 Galvanic isolation . 50 2.5.2 DC injection and leakage . 51 2.5.3 DC voltage requirement . 52 2.5.4 Efficiency ............................. 55 2.5.5 THD . 55 2.5.6 Challenges conclusion . 56 2.6 Three-phase converter control . 56 2.6.1 Two-dimensional space vector modulation . 56 2.6.2 Control of two-dimensional SVM . 59 2.6.3 Voltage sags . 61 2.6.4 Three-dimensional space vector modulation . 63 2.6.5 Control of three-dimensional SVM . 64 2.6.6 Three-phase converter control conclusion . 66 2.7 Simulations . 66 2.7.1 Electric component values . 67 2.7.2 Simulation 1: Three-leg single controller . 68 2.7.3 Simulation 2: Three-leg dual controller . 73 2.7.4 Simulation 3: Four-leg triple controller . 73 2.8 Conclusion . 76 3 AC charging infrastructure 79 3.1 Introduction . 79 viii/xv 3.2 Fast-charging AC cord sets . 79 3.3 Communications . 83 3.3.1 Annex D communication . 84 3.3.2 Communication test . 86 3.4 Construction of a three-phase 63A EVSE . 87 3.5 Charging station test . 89 3.5.1 Renault Zoe charging session . 89 3.5.2 AC Propulsion eBox charging session . 91 3.5.3 Test conclusion . 91 3.6 Load management . 91 3.7 Conclusion . 96 Conclusion 99 Bibliography 101 Appendix 107 A Inductor measurements 107 B Tests on Think Induction Motor 109 B.1 Stator resistance test . 109 B.2 Blocked rotor test . 110 B.3 No-load test . 112 B.4 Dynamic torque curve . 115 B.5 50Hz torque test . 116 B.6 Max torque test . 118 C Python script for amplifier measurements 121 D Example calculation on AC versus DC power transfer 123 E dq control in three-phase converter 125 F Industry terminology 129 G EV communication test 131 ix/xv x/xv List of Figures 1 Overview of EV components . 4 1.1 A typical three-phase IEC 61851 compliant type 2 connector (left) and a single-phase J1772 type 1 connector (right) . 8 1.2 Tesla Roadster power versus speed [62]................. 11 1.3 Cumulative driving distance . 18 2.1 Voltage, current and active power in AC motor for a single phase . 26 2.2 Four quadrant bidirectional single-phase converter . 27 2.3 Typical three-phase AC motor drive . 28 2.4 Switching scheme for generating three-phase voltages . 30 2.5 Single phase rectifier with waveforms . 32 2.6 Single phase rectifier with active PFC and waveforms . 33 2.7 Grid interfacing three-phase bridge . 34 2.8 Integrated motor drive and battery charger using discrete inductors 34 2.9 Integrated motor drive and battery charger using motor leakage in- ductance.................................. 34 2.10 Simplified single-line converter circuit . 35 2.11 Phasor diagram with grid, inductor and converter voltage phasor . 37 2.12 Multiple phasors with varying power factor angle . 37 2.13 Induction motor equivalent circuit diagram .