Converter Cell Capacitor Cooling via Thermal Link
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Solution Overview
Problem
In Modular Multilevel Converters, the compact design of power electronic converters leads to reduced space for cooling between heat-generating components, limiting the effectiveness of air cooling for cell capacitors, which can result in undesirable hot spot temperatures and reduced component lifespan.
Innovation Solution
A forced convection boiling two-phase cooling system is implemented, utilizing a closed working fluid circuit with evaporators connected to semiconductor switch elements and a dedicated thermal link with high thermal conductivity to transfer heat from power electronic modules to cell capacitors, ensuring efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If heat-generating components are packed more closely to reduce footprint, then space utilization improves, but air cooling effectiveness deteriorates due to reduced circulation space
Solution Approach 1:
A dedicated thermal link acts as an intermediary heat transfer component, conducting heat from the capacitor to the power electronic module's cooling system. This mediator enables effective heat removal despite the close packing that prevents direct air cooling of the capacitor.
Solution Approach 2:
The cooling systems of the power electronic module and capacitor are merged into a unified thermal management approach. The capacitor utilizes the power electronic module's forced convection cooling infrastructure through the thermal link, consolidating cooling resources.
2Temperature
If forced convection cooling is used for power electronic modules, then cooling efficiency improves, but system complexity increases due to additional fluid circuits
Solution Approach 1:
The capacitor cooling is merged with the power electronic module's existing forced convection cooling system. By using the same fluid circuit and cooling infrastructure for both components, the system avoids the complexity of a separate cooling circuit while achieving effective cooling for both heat-generating components.
3Device complexity
If air cooling is used for cell capacitors, then system simplicity is maintained, but cooling sufficiency deteriorates in compact designs
Solution Approach 1:
The thermal link serves as an intermediary that enables the capacitor to access the more effective forced convection cooling without requiring direct fluid contact or a separate cooling system. This maintains relative simplicity while overcoming the insufficiency of air cooling in compact designs.
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 provides sufficient cooling for cell capacitors in compact designs, maintaining optimal operating temperatures and extending the lifespan of converter components by effectively managing heat transfer and reducing the risk of hot spots.
Implementation Method 1
evaporators arranged in thermal contact with the semiconductor switch elements and adapted for evaporating a dielectric working or cooling fluid, or refrigerant
Implementation Method 2
forced convection boiling two-phase cooling system
Implementation Method 3
a central condenser
Implementation Method 4
a pump for circulating the fluid
Implementation Method 5
a dedicated thermal link with high thermal conductivity to transfer heat from power electronic modules to cell capacitors
Data Source
Figure 1~2
AI summary
The present invention is concerned with a provision of sufficient cooling to converter cells arranged in a compact design. In a stack of converter cells arranged on top of or next to each other, both the power electronics modules and cell capacitors face corresponding components of adjacent converter cells, which requires adequate electric, dielectric, and short-circuit design measures in-between the cells. With increasing footprint requirements, heat-generating components are packed more closely and the space available next to the cell capacitors, specifically between the power electronic modules and the capacitors, becomes scarce. Accordingly, in a compact converter design, circulation of ambient air in a stacking direction may be impeded or reduced to an extent that precludes cooling of the cell capacitors via capacitor surfaces perpendicular to the stacking direction. Here, a cooling system that transfers, via dedicated thermal connections, excess cooling power from forced convection boiling cooling of the power electronic modules to the cell capacitors ensures sufficient cooling of the latter.