Power Converter Voltage Management for BEV Efficiency
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Solution Overview
Problem
Current high-voltage battery electric vehicles (BEVs) face inefficiencies due to the limitations of 400V HV batteries and DC buses, which can be improved by increasing battery voltage, but this requires innovative power conversion solutions to manage voltage differences across various vehicle systems effectively.
Innovation Solution
A vehicle power system incorporating a power converter with a transformer and series-connected capacitors, operated by a controller to maintain equal voltage across capacitors and double the input voltage at the output, enabling efficient power transfer between the charger and traction battery while adapting to different voltage requirements within the vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the high-voltage battery voltage is increased to improve BEV efficiency, then the energy efficiency improves, but the complexity of power conversion systems increases due to voltage mismatch between battery, charger, and utility bus
Solution Approach 1:
The power converter is designed to perform multiple functions: it converts utility voltage to charger voltage for charging operations, and simultaneously converts charger voltage to battery voltage for propulsion. This multi-functionality eliminates the need for separate converters for each voltage conversion path, reducing overall system complexity while supporting the high-voltage battery architecture needed for improved efficiency
Solution Approach 2:
The system dynamically adjusts voltage parameters through controlled switching operations. The controller modulates the switching of power electronic devices to transform voltage levels adaptively - converting from utility voltage to charger voltage during charging, and from charger voltage to battery voltage during discharge, enabling efficient operation across different voltage domains without requiring fixed-ratio conversion
2Use of energy by moving object
If higher voltage is used on the drive bus to improve efficiency, then energy efficiency improves, but compatibility with lower voltage chargers and utility buses deteriorates
Solution Approach 1:
The charger bus serves as an intermediary voltage domain between the utility bus and the high-voltage battery. The power converter first transforms utility voltage to charger voltage, establishing an intermediate level that bridges the gap between low-voltage utility infrastructure and high-voltage battery systems. This intermediary approach enables compatibility with standard chargers while supporting high-voltage efficient operation
Solution Approach 2:
The voltage conversion process is segmented into two distinct stages: first converting utility voltage to charger voltage, then converting charger voltage to battery voltage. This segmentation allows each conversion stage to be optimized independently and enables the system to interface with both low-voltage infrastructure and high-voltage battery systems without requiring direct high-voltage connection to external chargers
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 solution enhances the efficiency of BEVs by effectively managing voltage differences, allowing for higher voltage on the drive bus while using lower voltage components on the charger and utility bus, improving compatibility and reducing manufacturing costs.
Implementation Method 1
a transformer having a primary side connected to the charger and a secondary side connected to the battery
Data Source
AI summary
A power converter includes a plurality of switches, a transformer electrically connected between some and other of the switches, and a plurality of series connected capacitors electrically connected between the switches and an output of the power converter. A controller operates the switches such that a voltage at an input of the power converter and across each of the capacitors is same and a voltage at the output is double the voltage at the input.