Traction Inverter DC-DC Transfer Across Mismatched Vehicle Voltages
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Solution Overview
Problem
There is a need for efficient electric power transfer between an on-vehicle DC power source and an off-vehicle DC power source in electric vehicles, where the on-vehicle power source has a higher nominal voltage than the off-vehicle power source, requiring innovative methods to manage voltage differences and facilitate energy transfer.
Innovation Solution
The method involves establishing a rotor position of a traction motor at a predetermined electrical angle, coupling the on-vehicle DC power source to the traction motor's stator phase windings, and using a power inverter with solid-state switches to configure the system as a switched-mode power converter, either in buck or boost mode, to transfer energy between the sources, with control of conduction through pulse width modulation to manage voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a power inverter is used to transfer power between DC power sources with different voltages, then energy transfer efficiency is improved, but device complexity increases due to the need for switched-mode power converter configuration
Solution Approach 1:
The power inverter is configured to perform multiple functions: it operates as a motor controller during vehicle propulsion and as a switched-mode power converter during wireless power transfer. This multi-functionality allows efficient energy transfer between DC power sources with different voltages without requiring a separate dedicated power converter, thereby improving energy efficiency while minimizing the increase in device complexity.
Solution Approach 2:
The system dynamically changes the operating parameters of the power inverter by adjusting the duty cycle of the solid-state switches. This parameter change enables the inverter to adapt to different voltage levels (48V to 800V) and operate in different modes (buck or boost), achieving efficient energy transfer across voltage differences without requiring multiple fixed-configuration converters.
2Power
If solid-state switches are used to control power flow, then power transfer capability is improved, but ease of operation deteriorates due to the need for precise conduction control
Solution Approach 1:
The control system continuously monitors the state of solid-state switches and adjusts their conduction based on feedback signals. This feedback mechanism ensures precise control of power flow while maintaining ease of operation, as the system automatically adapts to changing conditions without requiring manual intervention. The feedback control enables the system to safely manage high-power transfers between different voltage sources.
3Adaptability or versatility
If the power inverter is configured as a switched-mode power converter, then adaptability to different voltage sources is improved, but device complexity increases due to additional configuration requirements
Solution Approach 1:
The power inverter employs dynamic switching of solid-state devices to adapt to different voltage sources. By dynamically adjusting the conduction states of switches and changing the duty cycle, the system can operate in buck mode (800V to 48V) or boost mode (48V to 800V) as needed. This dynamic adaptability is achieved through control logic that automatically configures the inverter based on the connected power source, providing versatility without requiring multiple dedicated hardware configurations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient energy transfer between the on-vehicle and off-vehicle DC power sources, accommodating voltage differences and optimizing energy transfer efficiency by configuring the power inverter as a switched-mode power converter, thereby supporting seamless power exchange in electric vehicles.
Implementation Method 1
controlling conduction of the plurality of phase legs of the power inverter to operatively configure the power inverter and the plurality of stator phase windings as a switched-mode power converter
Implementation Method 2
a traction motor including a poly-phase stator winding having a plurality of stator phase windings
Data Source
AI summary
Electrical energy is transferred between an on-vehicle DC power source and an off-vehicle DC power source by controlling conduction of the phase legs of a power inverter to operatively configure the power inverter and the stator phase windings of a traction motor as a switched-mode power converter including the at least one phase winding and at least one switch of one of the phase legs.