Multi-cell Power Converter Start-up Voltage Balancing
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Solution Overview
Problem
In multi-cell power converters, the imbalance of DC link voltages during start-up can exceed the voltage blocking capability of semiconductor devices, leading to potential damage due to differing power consumption by individual converter cells.
Innovation Solution
At least one second converter cell is configured to internally dissipate power received from the corresponding DC link capacitor during start-up, limiting the voltage across the DC link capacitor and maintaining it within a safe range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the first converter cells are implemented such that during start-up the DC link capacitors are connected in series to form a capacitive voltage divider, then the start-up process can be simplified, but the DC link voltage imbalance may exceed the voltage blocking capability of semiconductor devices
Solution Approach 1:
The patent applies preliminary action by enabling at least one second converter cell to dissipate power during the start-up phase before normal operation begins. This preliminary power dissipation prevents voltage imbalance from exceeding semiconductor device capabilities, thereby protecting the devices while maintaining the simplified series capacitor start-up approach.
Solution Approach 2:
The patent converts the potentially harmful effect of power consumption differences between converter cells into a beneficial protective mechanism. By intentionally allowing one second converter cell to dissipate power during start-up, the system prevents dangerous voltage imbalances, transforming what could be a source of damage into a protective feature.
2Adaptability or versatility
If individual converter cells have different power consumption characteristics, then the converter cells can be designed with different functional requirements, but this leads to DC link voltage imbalance during start-up
Solution Approach 1:
The patent introduces an intermediary mechanism where at least one second converter cell acts as a mediator during start-up by dissipating power. This intermediary action compensates for the different power consumption characteristics of individual converter cells, thereby maintaining DC link voltage balance while allowing functional diversity among cells.
3Productivity
If no active voltage regulation is performed during start-up, then the start-up routine is simpler and faster, but the DC link voltages cannot be balanced
Solution Approach 1:
The patent implements self-service by enabling the second converter cells to automatically dissipate power during start-up without requiring external control intervention. This self-service mechanism maintains DC link voltage balance while preserving the fast, simple start-up routine, as the protection is inherent in the converter cell operation itself.
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 effectively balances the DC link voltages during start-up, preventing overvoltage and protecting semiconductor devices by actively managing the power dissipation in the second converter cells.
Implementation Method 1
at least one of the plurality of second converter cells is configured to, during start-up of the power converter, internally dissipate power received from the corresponding DC link capacitor
Data Source
AI summary
A power converter circuit includes a plurality of first converter cells, a plurality of second converter cells, and a plurality of DC link capacitors. Each of the plurality of first converter cells is coupled to a corresponding one of the plurality of DC link capacitors. Each of the plurality of second converter cells is coupled to a corresponding one of the plurality of DC link capacitors. At least one of the plurality of second converter cells is configured to, during start-up of the power converter, internally dissipate power received from the corresponding DC link capacitor while a cell output power of the at least one of the plurality of second converter cells is substantially zero.