Interaction between charging infrastructure and the electricity grid The situation and challenges regarding the influence of electromobility on mainly low voltage networks Shimi Sudha Letha Tatiano Busatto Math Bollen Interaction between charging infrastructure and the electricity grid The situation and challenges regarding the influence of electromobility on mainly low voltage networks Shimi Sudha Letha Tatiano Busatto Math Bollen Luleå University of Technology Department of Department of Engineering Sciences and Mathematics Division of Energy Science ISSN 1402-1536 ISBN 978-91-7790-807-4 (pdf) Luleå 2021 www.ltu.se SUMMARY This report summarizes the situation with knowledge and challenges regarding the large- scale introduction of electromobility in the Swedish power grid. The content convers a range of systemic perspectives in terms of challenges and impacts that the fast-growing amount of charging associated with electromobility poses to the actual power system. From this, several important questions are addressed in order to predict the future positive and negative impacts of this. A description of electromobility in technological terms is given by presenting various configurations of electric vehicles, charging infrastructure and energy supply. The focus is placed on the possible impacts on the low-voltage networks, mainly exploring the power quality issues and grid hosting capacity. The following power quality issues are addressed: rms voltage (slow voltage variation, overvoltage, undervoltage, fast voltage variations), unbalance, waveform distortion (harmonics, interharmonics, and supraharmonics), and power system stability. The hosting capacity is examined to predict whether the charging demand from electromobility can be accommodated in the existing power system considering the involved challenges. Furthermore, the aspect related to the charging process and people’s travelling patterns under a stochastic point of view is analyzed. With the advantages that electromobility brings, it is noticeable that people will change the way they move around. Insights from this perspective make it possible to predict how the grid needs to change to accommodate the future needs. From the found evidences in this report, it is noticed that the harmonic content of the current injected from electric vehicles charging is not negligible, but it is low in relation to the harmonics produced by other connected loads in the low voltage network. The biggest impact is on the rms voltage, which might drop and exceed the limits set by standards if a charging management is not available. Additionally, interharmonics results have shown to be a potential issue due the charging process. Other evidences from this report provides additional support for future discussions and debates regarding the impacts of electromobility on the electrical system. ACRONYMS AND DEFINITIONS BEV Battery-powered Electric Vehicle CIGRE International Council on Large Electric Systems DSO Distribution System Operator EMC Electromagnetic Compatibility ERS Electric Road System EU European Union (Also referred as EU-28) EV Electric Vehicle (includes BEV and PHEV) HPC High-Power Charging station HV High Voltage ICE Internal Combustion Engine IEA International Energy Agency LV Low Voltage MV Medium Voltage PHEV Plug-in Hybrid Electric Vehicle PQ Power Quality PV Photovoltaic SOC Battery State-Of-Charge TEN-T Trans-European Transport Network (TEN-T) TOU Time-Of-Use TSO Transmission System Operator V2G Vehicle-To-Grid ii CONTENTS Summary .................................................................................................................................... i Acronyms and Definitions ........................................................................................................ ii 1. Introduction ...................................................................................................................... 1 2. Overview of Electro-Mobility .......................................................................................... 3 The move towards electric vehicles .......................................................................... 3 Swedish initiatives towards electro-mobility ............................................................ 4 Electro-mobility forecast in Sweden ......................................................................... 6 Charging infrastructure ............................................................................................. 6 2.4.1. Overview of electric vehicle charging ............................................................... 7 Power system challenges .......................................................................................... 9 2.5.1. Power consumption ........................................................................................... 9 2.5.2. Power quality ..................................................................................................... 9 2.5.3. Network planning ............................................................................................ 10 Electric road system ................................................................................................ 10 References ............................................................................................................... 11 3. Charging of Electric Vehicles ........................................................................................ 14 Battery types ........................................................................................................... 14 SAE charging levels ................................................................................................ 15 Types of charging ................................................................................................... 16 Charging standards.................................................................................................. 16 Types of charging systems ...................................................................................... 17 Different charging modes ....................................................................................... 17 Converter topologies for EV charger ...................................................................... 17 Ratio of average electric vehicle per public charging point ................................... 21 References ............................................................................................................... 21 4. Overloading .................................................................................................................... 23 Stochastic approach ................................................................................................ 23 Load profiles at subtransmission level .................................................................... 24 4.2.1. Historical load profile and electricity price analysis (Case Study 2016) ........ 25 4.2.2. Stochastic EV profile (Size and Numbers) generation .................................... 27 4.2.3. Available capacity of the network and stochastic EV profile comparison ...... 31 iii References ............................................................................................................... 31 5. Undervoltage .................................................................................................................. 32 Introduction ............................................................................................................. 32 Undervoltage ........................................................................................................... 32 5.2.1. EV customers future loading scenario ............................................................. 33 Impacts of electric vehicles ..................................................................................... 34 Risk of overvoltage ................................................................................................. 35 Research gap - Electrified roads and railways ........................................................ 35 References ............................................................................................................... 35 6. Fast Voltage fluctuations and Light Flicker ................................................................... 37 Some relevant standards ......................................................................................... 37 6.1.1. Sources and causes .......................................................................................... 37 6.1.2. Effects .............................................................................................................. 38 Real time electric vehicle measurement data .......................................................... 39 Voltage fluctuation mitigation techniques .............................................................. 41 Multiple individual rapid voltage changes .............................................................. 41 Flicker issues in EV charging ................................................................................. 42 Light flicker due to RVC (Voltage dips- emulating charging pulses) .................... 43 Light flicker due to supraharmonics ....................................................................... 47 References ............................................................................................................... 48 7. Voltage Unbalance ........................................................................................................