Originally published: 2019-09-16, original URL: https://www.fangzhenxiu.com/post/283819
Motivation: Why Use Electric Vehicles Advantages of fully electrifying transportation: 1. Improve efficiency: reduce energy consumption 2. Replace petroleum as the primary energy source 3. Reduce environmental impact 4. Lower costs
Data from the U.S. Electronic Industries Alliance: share of transportation energy consumption and CO2 emissions 1. Transportation accounts for 28% of total U.S. energy consumption 2. Transportation accounts for 33% of CO2 emissions 3. Petroleum accounts for 93% of U.S. transportation energy consumption
Figure 1 More and more vehicles Figure 2 Vehicle dynamics Figure 3 Driving cycles Figure 4 Average power and energy Figure 5 Gasoline engine vs. electric drive Figure 6 Conventional vehicles vs. electric vehicles Figure 7 Stored energy and power density Figure 8 Conventional vehicles vs. electric vehicles Figure 9 Research on CO2 emissions and petroleum substitution Figure 10 Impact of policy Figure 11 Challenges of electric vehicles
Power Electronics Technology 1. Transportation electrification is a technology that makes a safe, reliable, and environmentally friendly future possible. 2. Problems faced by transportation electrification A. Battery energy storage and charging time are insufficient to meet consumer expectations B. High cost of power electronics: 33% of the total cost of hybrid vehicles comes from power electronics C. Miniaturization of weight and volume; thermal management and increased overall weight, consideration of safety issues D. Increase in power: materials (semiconductors, inductors, capacitors) are not cost-effective 3. Intelligent and integrated design of power electronics products is an inevitable requirement for the sustainable development of electric vehicles
Background: Role of power electronics Figure 12 Application of power electronics in future electric vehicles Figure 13 Electric vehicle drivetrain Figure 14 Cooling system using the Audi Q5 as an example Figure 15 Design of power electronics Figure 16 Powertrain components
Power Modules Figure 17 Power module substrate Description of the power module substrate: direct bonded copper (DBC) ceramic substrate, with one side soldered to the die and the other side soldered to the aluminum heatsink. Function: electrical conduction (copper-clad surface), insulation (ceramic board) Figure 18 Die Die description: the core of the power module, made of Si material (SiC and GaN in the future), with the die soldered onto the DBC. Function: electrical connection and mechanical connection Figure 19 Electrical connections Description: wire or ribbon bonds; usually aluminum or gold. Function: electrical connection Figure 20 Substrate Description: typically copper or metal matrix composites (such as AlSiC). Function: mechanical support and heat dissipation. Figure 21 Packaging Description: the interior of the module is filled with silicone gel. Function: electrical insulation, mechanical protection (damping mechanical shock), heat dissipation. Figure 22 Housing and terminals Description: the module is encapsulated in a plastic housing; bonding wires electrically connect the power module IGBT dies, diode dies, thermistors, etc. to the corresponding lead terminals. Function: mechanical protection and electrical connection. Figure 23 Cooling system Description: aluminum cooling systems are generally used; copper tubes are used for cooling in systems with high heat dissipation requirements; water and 50% ethylene glycol are generally used in vehicles. Figure 24 Power module Description: the packaged power module is mounted on the heatsink, with a thermal interface material (TIM) beneath the module, generally thermal grease and phase-change materials, to increase thermal conductivity; about 40% of the thermal resistance from junction to ambient is due to the TIM. Figure 25 Gate driver board Description: the gate driver board converts the PWM signal from the DSP into gate signals for controlling the power module. The gate driver board needs to be as close as possible to the power module to reduce interconnection length and minimize parasitic parameters. Figure 26 Sensors Description: current sensors control motor torque through closed-loop control, and resolvers control motor speed through closed-loop control. Figure 27 Busbars Description: busbars are generally copper bars, used for electrical connections between the power components of the inverter; for most inverters, the busbar must be designed to minimize parasitic inductance, generally using laminated busbars. Figure 28 Control board Description: control boards are usually much more crowded than shown in the figure; they include a microprocessor, usually a digital signal processor (DSP), control power supply, driver power supply, analog and digital interface units, gate drivers, etc. Figure 29 DC-LINK Description: the motor controller (inverter) requires a DC-LINK capacitor. Capacitors typically account for one-third of the inverter volume and roughly the same proportion of weight, and their cost is second only to that of the power module; in the motor controller, they filter the ripple current in the DC loop and maintain voltage stability in the DC loop. Figure 30 Model and physical object Figure 31 Power electronics drive Figure 32 Research areas Figure 33 Functional integration Figure 34 Functional integration Figure 35 Functional integration
Example 1: Bidirectional DCDC converter Figure 36 Powertrain DCDC Figure 37 Optimized powertrain DCDC Figure 38 Optimized powertrain DCDC Figure 39 Optimal bus voltage Figure 40 Integrated DCDC and OBC Figure 41 Reduced cooling
Example 2: Battery management system Figure 42 Battery management system Role of the battery management system: It is a system for managing the battery, usually with the function of measuring battery voltage to prevent or avoid abnormal conditions such as battery over-discharge, overcharge, and overtemperature. With technological development, many functions have gradually been added, including communication, SOC estimation, abnormal alarms, abnormal protection, balancing, etc. Passenger vehicles: 80–100S; commercial vehicles: 100–200. Figure 43 Cell balancing during charging Description: small differences in cell characteristics are exacerbated over multiple charge and discharge cycles due to series connection Figure 44 Cell balancing during discharging Description: discharge is limited by the first battery shown in the figure to reach the minimum allowable state of charge (SOC). Figure 45 Unbalanced discharge state Description: Discharge is limited by the first battery in the figure to reach the minimum allowable state of charge (SOC); the effective pack capacity is limited to the lowest battery capacity (in ampere-hours). Figure 46 Unbalanced charge state Description: when charging again, charging stops when the first battery reaches maximum capacity as shown in the figure, resulting in incomplete charging of some batteries and reducing the total pack battery capacity. Figure 47 Passive balancing or dissipative balancing Figure 48 Active balancing
Functional Integration Figure 49 Functional integration Description: design combining the necessary DCDC converter with the balancing converter; effective (differential) efficiency 100% Efficiency improvement at almost zero cost;
Future Development: Where Electronics Will Take Us Connected vehicle interaction systems Figure 50 VXG Description: electric vehicle batteries used for grid energy storage; alleviating power supply pressure, performing peak and off-peak power regulation; performing load shifting and power compensation.
Wireless charging Figure 51 Wireless charging Opportunities for wireless charging: 1. Provide convenience for customers Plug-in hybrid and battery electric vehicles can be charged conveniently and safely without cables and plugs. With a wireless charging system, the charging process can be fully autonomous, saving time and labor costs. 2. Use dynamic road charging to reduce on-board ESS size Figure 52 Wireless charging scenarios Figure 53 Wireless charging applications
3D printing Figure 54 3D-printed vehicle Figure 55 ORNL 3D-printed electric vehicle Figure 56 3D-printed water-cooled 80KW motor controller
Summary: 1. Power electronics technology plays a crucial role in the future applications of electric vehicles 2. Power electronics engineers must comprehensively consider performance within the system, rather than considering efficiency in isolation 3. Future technologies, including wireless power transfer and 3D printing, can completely transform this industry
Reference: Electric Drive Technologies for Future Electric Vehicles; Professor Daniel Costinett, The University of Tennessee