Three-Level Power Conversion Device Current Redistribution
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Solution Overview
Problem
A three-level power conversion device with a clamp circuit faces instability during single-phase three-wire operation when the two AC powers output are different, causing some currents to pass through the power supply while others do not, leading to unstable operation.
Innovation Solution
Incorporating a second bidirectional switch between specific nodes in the bridge and clamp circuits, allowing for the redistribution of currents and reducing the disparity in current flow through the power supply, thereby maintaining stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a clamp circuit is used in a three-level power conversion device, then the device can output AC voltage with at least three voltage levels, but stable operation cannot be maintained during single-phase three-wire operation when the two AC powers output are different
Solution Approach 1:
The invention divides the single output phase into two separate output phases (first AC power and second AC power), allowing independent power delivery to two different loads. This segmentation enables the power conversion device to handle unbalanced load conditions by providing dedicated current paths for each output, thereby maintaining operational stability while preserving the three-level voltage output capability.
2Adaptability or versatility
If the two AC powers output from the three-level power conversion device are different, then the device can serve multiple loads with different power requirements, but current flow becomes unbalanced causing some currents to pass through the power supply while others do not
Solution Approach 1:
The invention introduces a neutral point as an intermediary connection between the two output phases. This neutral point serves as a common reference that allows both output phases to draw current from the DC power supply through balanced paths. The neutral point acts as a mediator that equalizes the current flow distribution, ensuring that both AC power outputs can serve different loads while maintaining stable current flow through the power supply.
3Reliability
If a second bidirectional switch is added to the bridge circuit, then current distribution is improved and stable operation is maintained, but the device complexity increases
Solution Approach 1:
The second bidirectional switch in the fourth leg serves multiple functions simultaneously: it provides an additional current path for balanced current distribution, enables the neutral point to function as a common reference for both output phases, and allows the circuit to maintain stability under unbalanced load conditions. By making this switch multi-functional, the invention achieves improved reliability without adding excessive complexity, as the switch integrates several critical functions into a single component.
Data Source
AI summary
A bridge circuit includes a first leg and a second leg arranged in parallel between the first node and the third node. A clamp circuit includes a third leg including a first bidirectional switch disposed between a fourth node that is a midpoint of the first leg and a fifth node that is a midpoint of the second leg. A first reactor is connected with the fourth node and a sixth node, and a second reactor is connected with a fifth node and a seventh node. A fourth leg includes a second bidirectional switch disposed between the second node and the fourth node or the fifth node.