Vehicle Power Conversion Device Segmentation
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Solution Overview
Problem
Conventional vehicle power conversion devices using diode-clamped three-level circuits face challenges with high-voltage silicon carbide elements being expensive and requiring reliability testing, leading to the use of low-breakdown voltage elements connected in series, which increases losses and complexity, and necessitate cooling devices that complicate the structure and deteriorate cooling performance due to insulation needs.
Innovation Solution
A vehicle power conversion device comprising a two-level converter and a three-level converter with specific switching devices and capacitors, where the two-level converter uses silicon carbide devices for low switching losses and the three-level converter uses silicon devices for high voltage resistance, eliminating the need for insulation media between the cooling device and power modules by designing power modules with appropriate dielectric strengths and arranging capacitors and power modules for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-voltage silicon carbide elements are used, then voltage resistance is improved, but cost increases and reliability testing is required
Solution Approach 1:
The patent segments the voltage handling function by using a two-level converter for high-voltage processing with silicon devices and a three-level converter for low-voltage processing with silicon carbide devices. This segmentation allows each converter to operate within its optimal voltage range, avoiding the need for expensive high-voltage silicon carbide elements while maintaining overall system voltage resistance.
Solution Approach 2:
The patent applies local quality by matching device characteristics to specific circuit locations: silicon devices are used in the two-level converter where high voltage is present, while silicon carbide devices are used in the three-level converter where lower voltage operates. This localized device selection optimizes both cost and performance for each specific application area.
2Ease of manufacture
If low-breakdown voltage silicon carbide elements are used, then cost is reduced, but switching losses increase when connected in series
Solution Approach 1:
The patent segments the power conversion function into two converters: a two-level converter that handles high voltage with silicon devices, and a three-level converter that handles lower voltage with efficient silicon carbide devices. This segmentation allows silicon carbide devices to operate in their optimal voltage range where they exhibit low switching losses, rather than being forced to operate in series at higher voltages where losses increase.
3Temperature
If cooling device is grounded for external cooling, then cooling performance is improved, but potential difference occurs requiring insulation media
Solution Approach 1:
The patent applies equipotentiality by grounding the cooling device and designing the power module mounting structure to maintain equipotential connections. The case of each power module is grounded through the cooling device, and the circuit board is designed with appropriate grounding paths, ensuring that all components remain at the same potential and eliminating the need for insulation media between the cooling device and power modules.
4Reliability
If insulation media are provided between cooling device and power modules, then potential difference is managed, but cooling performance deteriorates and structure complicates
Solution Approach 1:
The patent eliminates the need for insulation media by implementing equipotential grounding throughout the system. The cooling device is grounded, and the power module cases are electrically connected to the cooling device through the mounting structure. The circuit board is designed with grounding paths that maintain equipotential conditions, allowing direct thermal contact between power modules and cooling device without insulation barriers that would impede heat transfer.
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 configuration reduces switching losses and maintains high voltage resistance while simplifying the structure and improving cooling performance by eliminating insulation media, allowing for direct mounting of power modules on a grounded cooling device.
Implementation Method 1
a cooling device 720, on which the power modules 704a to 704d and the power modules 705a to 705f are arranged
Implementation Method 2
When this cooling device is exposed to the outside environment so as to perform cooling by use of traveling wind of a vehicle
Data Source
AI summary
A vehicle power conversion device includes a two-level converter, a three-level converter and one cooling device. The two-level converter includes a capacitor, first switching devices and second switching devices. The three-level converter includes two capacitors, third switching devices, fourth switching devices and a bidirectional switch. The first and second switching devices are embedded in first power modules, and the third and fourth switching devices are embedded in second power modules. The second power modules have dielectric strength voltages at least equal to a voltage applicable to any one of the two capacitors connected in series included in the three-level converter, and the first power modules have dielectric strength voltages at least equal to a sum of a voltage applicable to any one of the two capacitors connected in series included in the three-level converter and a voltage applicable to the capacitor included in the two-level converter.