CODEN:LUTEDX/(TEIE-5397)/1-87/(2017) Current ripple simulation in DC traction voltage system of an electric bus: 2 Filip Gard Linda Nilsson Division of Industrial Electrical Engineering and Automation Industrial Electrical Engineering and Automation Faculty of Engineering, Lund University Lund Institute of Technology Master thesis in cooperation with Volvo Buses Current ripple simulation in DC traction voltage system of an electric bus: 2 Authored by: Filip Gard || [email protected] Linda Nilsson || [email protected] Supervisors: Per Widek || [email protected] Philip Abrahamsson || [email protected] June 12, 2017 Abstract Current ripple can cause a lot of problems as it spreads in the DC-side of the TVS of electric and electric hybrid vehicles. Fully knowing the properties of the TVS can be used to build a simulation model to determine the spreading of current ripple beforehand, which in turn is useful for calculating component placement, optimal filter sizes, and component lifetime. Being the second in line of an ongoing chain of thesis projects at Volvo buses, this master thesis proposes methods of measurement, simulation model adjustments, and usage of the finished model. Using an LCR meter, the impedance of several components was measured and modeled in LTSpice based on curve fitted parameters. Comparing the simulated properties to current and voltage levels measured in real vehicles, the accuracy of the models of different buses is presented and validated. 1 #VOLVO: Some information, such as figures and values marked with #VOLVO are of specific value to Volvo and not for public. Therefore the figures are replaced and the values are concealed. Acknowledgements A big thank you to our advisor Philip Abrahamsson at the Department of Industrial Electrical Engineering and Automation at Lund University’s Faculty of Engineering. Also a big thank you to the entire team at Volvo, especially to our supervisor Per Widek, Oskar Lingnert, and Jens Groot. For always lending their expertise and time, thank you to Getachew Darge and Lars Lindgren at the Department. A special thank you to Ville Akujärvi, without who the Power Amplifier measurements would never have been performed. Last but not least, thank you to our examiner Mats Alaküla, senior advisor at Volvo GTT and Professor at the Department of Industrial Electrical Engineering and Automation at Lund University. 2 #VOLVO: Some information, such as figures and values marked with #VOLVO are of specific value to Volvo and not for public. Therefore the figures are replaced and the values are concealed. Table of Contents Abstract ...................................................................................................................................... 1 Acknowledgements .................................................................................................................... 2 1. Introduction ......................................................................................................................... 6 1.1 Problem formulation .................................................................................................... 6 1.2 Purpose and aim ........................................................................................................... 6 1.3 Scope and limitations ................................................................................................... 7 1.4 Thesis outline ............................................................................................................... 7 1.5 Methods ....................................................................................................................... 8 2. Theory ................................................................................................................................. 9 2.1 Fundamental electrical and CM filter properties ......................................................... 9 2.1.1 Impedance ............................................................................................................ 9 2.1.2 Frequency and current dependency in passive components ............................... 12 2.1.3 Common mode noise .......................................................................................... 15 2.1.4 Differential mode noise ...................................................................................... 16 2.1.5 The CM choke .................................................................................................... 16 2.2 Measurement methods ............................................................................................... 17 2.2.1 LCR-measuring .................................................................................................. 17 2.2.2 Current transformer ............................................................................................ 18 2.2.3 Power Amplifier measurements ......................................................................... 19 2.2.4 Battery measurements using a current injection transformer ............................. 20 3. Traction Voltage System ................................................................................................... 21 3.1 Types of Traction Voltage Systems ........................................................................... 21 3.1.1 Electric hybrid .................................................................................................... 21 3.1.2 Electric ............................................................................................................... 21 3.1.3 TWIN MOTOR BUS1 ....................................................................................... 22 3.1.4 TWIN MOTOR BUS2 ....................................................................................... 23 3.2 Subsystem specification ............................................................................................ 24 3.2.1 MDS- Motor Drive System ................................................................................ 24 3.2.2 DCDC – Direct Current Converter ..................................................................... 25 3.2.3 Air compressor ................................................................................................... 25 3.2.4 HVAC - Heat Ventilation and Air Conditioning ............................................... 25 3 #VOLVO: Some information, such as figures and values marked with #VOLVO are of specific value to Volvo and not for public. Therefore the figures are replaced and the values are concealed. 3.2.5 Heater ................................................................................................................. 26 3.2.6 OnBC - On Board Charger ................................................................................. 26 3.2.7 Cable ................................................................................................................... 26 3.2.8 ESS - Energy Storage System ............................................................................ 26 3.2.9 HJB – Hybrid Junction Box ............................................................................... 26 3.2.10 CSU – Charging Switch Unit ............................................................................. 26 4. Component measurements and impedance analysis ......................................................... 27 4.1 Sensitivity analysis .................................................................................................... 27 4.2 LCR measurements .................................................................................................... 28 4.2.1 EMD type B ....................................................................................................... 28 4.2.2 EMD type C ....................................................................................................... 31 4.2.3 DCDC ................................................................................................................. 33 4.2.4 Air compressor ................................................................................................... 35 4.2.5 HVAC ................................................................................................................. 37 4.2.6 OnBC .................................................................................................................. 39 4.2.7 Cables ................................................................................................................. 41 4.3 Current transformer measurements at grid frequency ............................................... 41 4.4 Power Amplifier measurement .................................................................................. 42 4.5 Battery measurements using a current injection transformer .................................... 49 4.6 Vehicle measurements performed by Volvo ............................................................. 50 4.6.1 EMD type b ........................................................................................................ 50 4.6.2 EMD type c ........................................................................................................ 52 4.6.3 Dual EMD type c ................................................................................................ 52 4.6.4 DCDC ................................................................................................................. 53 4.6.5 Air compressor ..................................................................................................